Spe TATE a a Ne iy vf i, ' Ui =i ta ‘ t Tibs Z ‘8 » Al i pe \) i RET NS ales i in 3 i : pity ype Mi ; eh OP AMAA ING Uh Dia) UR EATSY, cei ant Mg) A a uh Pia aie +. HG AM ' ' re : i ’ 1 1 i Riya fy Re ( prey y i ie ; fil hy tet il aa 6 va iy ~ i ,/ Le a? rn Oe 6 Sk ay hal SMITHSONIAN MISCELLANEOUS COLLECTIONS VOE. «122 “EVERY MAN IS A VALUABLE MEMBER OF SOCIETY WHO, BY HIS OBSERVATIONS, RESEARCHES, AND EXPERIMENTS, PROCURES KNOWLEDGE FOR MEN’’—JAMES SMITHSON (Pustication 4219) CITY OF WASHINGTON PUBLISHED BY THE SMITHSONIAN INSTITUTION 1955 The Lord Baltimore Press BALTIMORE, MD., U. & A. HSOWN AN 14 Vy LIBRARY ADVERTISEMENT The Smithsonian Miscellaneous Collections series contains, since the suspension in 1916 of the Smithsonian Contributions to Knowledge, all the publications issued directly by the Institution except the An- nual Report and occasional publications of a special nature. As the name of the series implies, its scope is not limited, and the volumes thus far issued relate to nearly every branch of science. Papers in the fields of biology, geology, anthropology, and astrophysics have predominated. LEONARD CARMICHAEL, Secretary, Smithsonian Institution. (iii) \ ‘ f Ba yrs ‘estan ne ‘irae ela 10. HOES 12. 13: 1A. CONTENTS Assot, C. G. Long-range effects of the sun’s variation on the temperature of Washington, D. C. 14 pp., 5 figs. May 12, 1953. (Publ. 4131.) Witson, Mitprep Stratton. New and inadequately known North American species of the copepod genus Diaptomus. 30 pp., 58 figs. Aug. 4, 1953. (Publ. 4132.) Snopcrass, R. E. The metamorphosis of a fly’s head. 25 pp., 7 figs. June 25, 1953. (Publ. 4133.) Assgot, C. G. Solar variation, a leading weather element. 35 pp., 22 fies: Aus.\4, 1053. (Publ. 4153.) Hoover, W. H., and Frortanp, A. G. Silver-disk pyrheliometry. TO pp: 1 ng. Aug. 4, 1953: (Publ. 4136.) Cuao, Hstu-Fu. The external morphology of the dragonfly Onychogomphus ardens Needham. 56 pp., 50 figs. Sept. 15, 1953. (Publ. 4137.) Bryan, Kirx. The geology of Chaco Canyon, New Mexico, in relation to the life and remains of the prehistoric peoples of Pueblo Bonito. 65 pp., 11 pls., 3 figs. Feb. 2, 1954. (Publ. 4140.) WeErTMorE, ALEXANDER. Further additions to the birds of Panama and Colombia. 12 pp. Dec. 17, 1953. (Publ. 4142.) Snoperass, R. E, Insect metamorphosis. 124 pp., 17 figs. Apr. I, 1954. (Publ. 4144.) WHITTINGTON, Harry B. Two silicified carboniferous trilobites from West Texas. 16 pp., 3 pls., 1 fig. Apr. 22, 1954. (Publ. 4146.) Ciark, AiLsa M., and Crarx, Austin H. A revision of the sea-stars of the genus Tethyaster. 27 pp., 12 pls., 2 figs. Apr. 8, 1954. (Publ. 4147.) Roru, Louis M., and Wi11s, Epwin R. The reproduction of cockroaches. 49 pp., 12 pls. June 9, 1954. (Publ. 4148.) Aszot, C. G. Washington, D. C., precipitation of 1953 and 1954. 4 pp., I fig. Apr. 20, 1954. (Publ. 4170.) Concer, PauL S. A new genus and species of plankton diatom from the Florida Straits. 8 pp., 4 pls. July 15, 1954. (Publ. 4171.) (v) ih oe yy , +a b al Roe ica @ Loli ] SMITHSONIAN MISCELLANEOUS COLLECTIONS VOLUME 122, NUMBER 1 Roebling Fund EONG-RANGE EFFECTS OF THE SUN'S VARIATION ON THE TEMPERATURE OF WASHINGTON, D. C. BY. Cc. G. ABBOT Research Associate, Smithsonian Institution (PusicaTion 4131) CITY OF WASHINGTON PUBLISHED BY THE SMITHSONIAN INSTITUTION MAY 12, 1953 The Lord Baltimore Hress BALTIMORE, MD., U. 8 Ac Roebling Fund LONG-RANGE EFFECTS OF THE SUN’S VARIATION ON Pie TEMPERATURE OF WASHINGTON; D.C. By C. G. ABBOT Research Associate, Smithsonian Institution In a closely knit series of four recent papers ' I have shown (1) that the sun’s output of radiation varies regularly in 23 periods, all in- tegrally submultiples of 222 years; (2) that customary methods of tabulating weather records, giving normal values therewith, are faulty for computations of periodic terms because the normals are taken as a whole, without segregation of times of high and of low sunspot frequency ; (3) that with proper normal values and attention paid to phase changes, depending on the seasons of the year and on the sun- spot frequency, the precipitation at Peoria, Ill., shows plainly control by the regular periodic variations of the sun; (4) that similar control by solar variation is to be found in the precipitation at Albany, N. Y. Since the variation of the sun operates primarily and directly on the temperature of the atmosphere, and only indirectly on precipita- tion, it seemed probable that a study of temperature might show even more perfect control by solar variation than does precipitation. I therefore take up in the present paper the temperature of Washington in relation to the 23 known regular periodic variations of the sun’s output of radiation. As in the Peoria and Albany papers, I employ, for the most part, the monthly mean values published in the three volumes of ‘World Weather Records,” but supplement these by U. S. Weather Bureau publications since 1940. As I have shown, in Smithsonian Publication No. 4090, that the normals customarily published are misleading for my purpose, I com- puted new normals as follows, suited to high and low sunspot activity. I chose as the dividing line a Wolf sunspot number of 20. The tem- peratures which follow are in degrees Fahrenheit. . Jan, Feb. Mar, Apr. May June July Aug. Sept. Oct. Nov. Dec: 3. P.<20.... ery MEY Eol sles, 53-9 64.0 72.5 se 74.1 68.1 56.9 46.0 36.4 PE 2Oswcis 3350 . 35:60 43.7 Bata 03:0) yee ny OSes OLS S6sa00) 45-5) 0 35-3 1 Smithsonian Misc. Coll., vol. 117, No. 10 (Publ. 4088) ; No. 11 (Publ. 4090) ; No. 16 (Publ. 4095), 1952; vol. 121, No. 5 (Publ. 4103), 1953. SMITHSONIAN MISCELLANEOUS COLLECTIONS, VOL. 122, NO. 1 2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I22 From these normal temperature values I computed departures, ex- pressed in tenths of degrees, for all months available from 1854 to 1939. There is a gap in “World Weather Records” of Washington temperatures through 1860 and 1861. To avoid embarrassment by large jumps of temperature from month to month, I computed 5- month running means of the departures. That is, for March use Jan.-Reb.- Mare Apr-May , and similarly for all months. From these smoothed temperature departures I computed the effects of the 23 regular periodic variations of the sun’s output of radiation, employing only the interval from 1854 to 1939. For I wished to use these results to forecast the behavior of Washington temperature from 1940 to 1951, and to compare such forecast with the actual event. Obviously it is not to be hoped to find in such a manner very close agreement between forecast and event, because of the complexity of the earth’s surface and the turbulence of the atmosphere. But if it can be shown that a general forecast of seasons, whether they are to be on the whole warm or cold, wet or dry, can be made with reason- able success for 10 years in advance, it would be of inestimable value to people in many walks of life. As was shown in the studies of precipitation at Peoria and Albany, changed atmospheric conditions at different seasons of the year and at different activity of sunspots displace the phases of the terrestrial responses to solar variations. The same holds true for the temperature of Washington. In short, the amplitudes and forms of the marches of terrestrial responses to the regular periodic solar variations do not alter greatly, though of course affected by interference of all other periodicities. But the phases of the terrestrial curves shift from season to season and alter with sunspot activity. It is not possible to subdivide the data sufficiently to follow all these phase changes ac- curately. I have contented myself with separate tabulations for three seasons, viz: January to April—May to August—September to De- cember ; and with two states of sunspot activity, viz: S. P.<20, S. P.>20 Wolf numbers. The method of tabulation follows closely that used in the study of precipitation at Albany. Readers are referred to Smithsonian Publi- cations No. 4095 and No. 4103 for information as to this method. I have gone still farther in the direction of the modifications of Peoria procedure as used at Albany, so as to strengthen the mean values in the Washington temperature tabulations. For, before taking means, I have shifted to a common phase the phases of all six mean tabula- NO. I TEMPERATURE OF WASHINGTON, D. C.—ABBOT 3 tions for the three seasons, and for the two intervals, 1854-1899, and 1900-1939, with all 13 periods up to 153 months. At Albany only seven periods were thus treated. 1 have also cleared every long period from 224 months to 91 months of overriding shorter periods, which are integral submultiples of these long periods. In this way it was found unnecessary to use periods longer than 454 months, for all the ampli- tudes of still longer periods were produced by overriding shorter ones. The 20 periods actually used for Washington temperatures were as follows, expressed in months: 4%, 5%, 6-1/15, 7, 8%, 96, 93, 10-1/10, 10-6/10, 113, 13-1/10, 13-6/10, 15%, 224, 243, 274, 305, 345, 383, 453. To illustrate the points brought out above I give several figures. Figures I and 2 relate to the period of 13.6 months, as tabulated in tables 1 and 2. Figure 1 and table 1 cover the times when Wolf sun- spot numbers exceeded 20, and figure 2 and table 2, the times when these were below 20. As usual, for periods of less than 224 months tables 1 and 2 each comprise six independent subordinate tables, which I am accustomed to designate as Ai, Az; Bi, B2; Ci, Cs. Subscripts 1 and 2 relate, respectively, to times before and after 1900 in the span of years 1854 to 1939. Letters A, B, C, relate, respectively, to the months January to April, May to August and September to December. Symbols ok, +, | indicate whether curves were unchanged, moved earlier, or moved later in their phases before taking means marked M. In the 13.6-month tabulation for sunspots>20, the subordinate tables have the following numbers of columns: Designation : Ai Aa Bi Ba Ci (Oo No. of columns: 6 5 7 8 5 6 Without giving dates of beginnings of columns or the temperatures found in the individual columns, and recalling to the reader that, in order to keep average lengths exactly 13.6 months, certain tempera- tures are duplicated so that the columns as tabulated are 14 months long, I now give in table 1 the mean values for A,, A2; Bi, Bz; Ci Cz and their departures from the averages of these mean columns. The means and the departures are stated in hundredths of a degree Fahren- heit. The columns of departures from table 1 are plotted in figure 1 with the appropriate letters. Along with their letters are given symbols ok, 4, or |, to show what shifts of phases were required to bring the six curves to a common phase. In table 3 these changes of phase are made, and the mean of the departures is taken as thus arranged. This mean of departures is always employed, but reduced back to its proper Means Fic. 1—Sunspots>2o0 scissae, months. numbers. Six determinations of the periodicity of 13.6 months and their mean at uniform phases in each figure. Ordinates, hundredths degree Fahrenheit. Ab- Other symbols explained in the text. Fic. 2.—Sunspots<20 numbers. TABLE 1.—Illustrating tabulation for 13.6 months. S.P.>20 Ay Mean Dep. AS) tye —I123 —123 Of 07 ma 43 nd + 32 + 32 +135 +135 “+-135 -+135 +125 +125 ele lay, Boe, ie Ge cates) Ls, Se AD AS aa Dona BOO — 78 — 78 00 4 A Mean By Dep. ATi (5 17 + 29 Slo4-0 05 49° 4, 3 2I + 25 BN oi 59 =113 Slo at ed 44+ 2 93, =" 47 36 + I0 Sh rie us 61 — 15 81 — 35 46 Cy Mean —16 +17 —28 + 5 34) ak —44 —II = 5017 == S421 —Io +23 42: >=) 9 7-28 + 5 +20 +53 GOL ats —72 —39 +20 Ae, ar) Dep. As Mean Dep. + 38 + 57 + 8+ 25 Se ey — 84 — 65 — 6— 77 — 88 — 60 — 32 — 13 — 20 — I — 94 — 75 — 64 — 45 + 74 + 93 + 78 + 97 + 30 + 49 — 2+ 17 —— LO) Bs Mean =30"=—89 —2I —30 —II —20 Slee —I7 —26 +9 O +11 + 2 PIO ee 7 +25 +16 Dep. Co Mean Dep. — 20 —87 o —67 70 = s --, 00 4-23 +100 +33 +120 +53 “157 50 +105 +38 +118 +51 + 62—5 ces ae =~ Sal =e + 42 —25 Ses) eae FOF. NO. I TEMPERATURE OF WASHINGTON, D. C.—ABBOT 5 phase status in the syntheses to be described below. It is used instead of the individual columns of departures given in table 1, because it rests on 37 columns of temperatures, instead of on 5, 6, 7, or 8 columns, like the individual sets of departures in table 1. The reader should recall that nearly 20 other periodicities have their effects upon the columns of temperatures used to determine the periodicity of 13.6 months. Hence it is highly desirable to screen out these interferences by numerous repetitions of the temperature columns. The final mean of departures is graphed in the heavy line, M, of figure I. With this explanation of figure 1 and tables 1 and 3, it will not be necessary to explain in detail figure 2 and tables 2 and 4. But it is interesting to point out that the two heavy curves, M, of final columns of mean departures, plotted in figures 1 and 2, are very similar in form and amplitude but differ in phase, and that they are derived from wholly independent groups of temperatures, one group coming solely from times when Wolf sunspot numbers exceed 20, and the other when these were below 20. In the 13.6-month tabulation, table 2, for sunspots20 As cok Biok Book Cyok Cos Mean 45 +57 +5 a0 aek7, —I7 —5 53 +25 +29 30 ro —25 — 8 — 78 +7 +15 —20 — I —32 —18 igs —65 —3 —45 —It —87 —59 —I123 —77 +25 —26 — 8 —67 —46 — 8&7 —69 +15 0 —I7 + 3 —26 — 43 —I3 —I3 + 2 —2I +23 —IlI + 32 ++ 2 aps 7 +23 +33 +17 +135 —75 +2 +16 —9 +53 +20 +135 —45 —47 +15 +5 +50 +18 +125 +93 +10 +63 +53 +38 +64 +127 +97 +15 +50 —3 +51 +64 + 52 +47 —25 +18 —39 = 5 8 — 13 +17 —35 —14 +7 —I2 — 8 Ave Asok Byok Bate onerpenn (ats Mean —17 +109 +101 +19 +60 +38 +50 +28 + 26 137 +5 +50 +15 +27 =e — 42 7 +55 +23 aay +5 —3I — 67 — 88 —5 —47 —I2 —42 —52 — 67 —I31 —67 —87 —39 —74 —3l — 47 —108 —95 —72 —50 —67 +3 — 76 — 86 —39 —60 —69 —55 +12 — 26 — 96 —85 —4o —39 —46 +19 — 54 — 63 —37 +2 —I4 —25 +32 + 51 —= 06 +57 +40 +48 +35 +31 + 51 + 54 +49 +20 +21 +38 +19 + 46 ++ 109 +25 +HI5 +70 +47 +7 + 40 + 49 +61 +23 + 6 +31 —I3 + 56 +164 +57 +78 +31 +62 cate results from temperatures recorded before and after 1900, during the interval of years 1854 to 1939. In table 5 the column A, is the mean of eight columns and the column A, of nine columns. The departures shown in these tabulations having been plotted in figure 3, the tabulation of A, discloses the presence of the overriding periodicity of 9¢ months, approximately one-sixth of the 544-month period. To eliminate it, the departure values in column Ag, table 5, were arranged in six columns and their mean taken as shown in table 6. NO. I TEMPERATURE OF WASHINGTON, D. C.—ABBOT 7. These mean departures, repeated six times, are given in table 5, and, being subtracted from column Az, give the departure column A*,. The values A1, are plotted in figure 3, and show great similarity in form and phase relations to the departures A,. So the mean of A, and A, is taken in table 5, and plotted in figure 3. It is now obvious that the Fic. 3—The 544-month periodicity, cleared of superriding periodicities, as explained in the text. curve has an overriding periodicity of half its length. Hence the mean of departures of columns A, and A}, is analyzed for a periodicity of (544-2) months, yielding the results shown in table 6 and repeated end to end in table 5. Subtracting from the values given in the next preceding column, and plotting the remainder in figure 3, it is now obvious that only the effect of the overriding periodicity of 114, or approximately one-fifth of 544 months, remains. Hence it proves unnecessary to employ the periodicity of 543 months at all in the synthesis of Washington temperatures. Similar steps eliminate the periodicities of 684 months and 91 months from consideration. Weare now prepared to test the usefulness of the 20 periodic terms which have been worked out in the Washington departures from Means... TABLE 5.—Clearing the periodicity of 544 months of overrides Mean Dep. Ay “ts | to ON | w& Ny Mean Dep. — 49 — 4 mae — 50 ite ia et pe edleetes| oR Go The 93M. 1G A Aly oo —26 —40 = 55 ss 58 —86 Mean A; & Al, —I2 —I3 —II ==45 —45 =95 —38 ae. tar +40 +62 +37 — 2 + 6 — 8 —I4 —29 Seis +48 +64 The 27iM. —I9 —24 —I19 —40 —44 —63 =o me) TE NO. I TEMPERATURE OF WASHINGTON, D. C.—ABBOT 9 TABLE 6.—Periodicities 94 and 274M The 93-month periodicity from departures A» Mean — 49 + 2 — 32 +11 + 6 oO —I0 anes + 47 ao —32 + 32 —I4 Stas re! + 89 +101 +1 + 29 +15 +36 as +118 + 46 == ae 9 =H +22 — 50 + 59 + 29 —43 + 55 +30 +8 a 7o ame + 41 —48 +106 +25 +8 —="03 — 44 + 17 —35 + 45 —2 —19 —102 — 23 — iI —53 + 58 —26 —24 — 53 — 19 + 18 —26 — 14 —40 —22 The 27}-month periodicity from mean A; and Al, Mean —I2 —26 —I19 —I13 —36 —24 —II —28 —I19 —45 55 —40 —45 —43 —44 —98 —29 SOs 0D —I2 53 —84 —28 —56 O80 ae hs ah fe} == 3 +21 —2I fe) +40 7109 O +62 +15 +38 =1-37 a4, +42 = 3 37 +18 aa +62 +34 = +38 +5 —14 +45 +15 —29 +32 +1 — 4 she. +2 +48 +19 +33 +64 +63 +63 +64 +21 +42 +54 2 +28 +43 aie +16 +17 —29 — 6 1-16 —45 a9 normal temperatures for the interval from 1854 to 1939. It is pro- posed to synthesize the results in such a manner as to forecast the march of temperatures from 1940 to 1951, 12 years, and to compare this synthetic forecast with the event. As the departures in monthly records used for the interval 1854 to 1939 were smoothed by 5-month running means, it is proper to compute the monthly departures from Io SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 the same normals over the period 1940 to 1951, and to smooth these departures also by 5-month running means. As it is common knowledge that the temperature of eastern United States has been gradually rising for the past century, it is highly prob- able that we shall find that the departures from our normals, which I computed from records of 1854 to 1939, will be prevailingly plus during the interval 1940 to 1951. On another account it is also unlikely that the scale of the synthetic summation of the effects of 20 periodic- ities will be exactly the scale of our normal values. For the accumu- lation of such inaccuracies as have resulted from computing depar- tures from averages of 20 means, such as are shown in tables 1 and 2, must almost infallibly result in a plus or a minus departure in the synthesis. Hence, on both accounts, just mentioned, we can expect that there may be a systematic difference in level between the synthe- sis and the event for the years 1940 to 1951. Furthermore, as appeared in the study of the precipitation at Peoria and Albany and, indeed, in the tabulation of Washington temperatures, in comparing results before and after 1900, there are encountered brief, as yet unpredictable, shifts of phase between synthesis and event in the study of the control of weather by periodic solar variations. Therefore we are to expect not only some systematic difference in scale level between the synthesized forecast and the event in Washing- ton temperatures from 1940 to 1951, but we may also expect occasional brief unpredictable shifts of phase between the predicted and observed results. With these remarks we preface the results obtained. In table 7 I give a sample of the synthesis covering only part of the year 1940. Figure 4 shows in the thin full line the synthesis, and in the thick full line the event, for the years 1940 to 1951. The system- atic difference in scale referred to above amounts to 3.0 degrees Fahrenheit, the synthesis being lower than the event. It has been removed in the thick dotted line by a flat addition of 3.0 degrees to the synthesis, in order that attention might not be diverted from the comparative marches of the two curves. That is the real test of the method. In figure 4 the lighter line represents the synthetic forecast, as computed after the manner of table 7. It is apparent that the princi- pal features are found in the curves both of forecast and event. But throughout the 12 years the event runs behind the forecast by several months. From 1940 to May 1941 the lag is 4 months. Thence, in the long interval to July 1948 the lag holds steadily at 3 months. Thence to October 1951 it is only 2 months. In the dotted line I have made these indicated shifts of phase, retreating the features of the N wonN — we et aentass ++I141/i mo eonotet wm Ss = SS Oe + ++4+++4++ AN}, ia, HIN Na FAP 20 periodicities deter- ed; dotted curve, pre- Se a | gil al aa a ee shot ° aes Fey t+HEQaca Aa S SI eae a If 7. a ahi ; atte eS NALA i WAV EAC TE Aaa Ld; A PY Sat itiey ‘Mie M3 @Ae VI SAN AS NN | \ NW eS , 9) Ae ee — ies —+— MO{) 71 7 Fic. landed and observed temperature departures for Washington, D. C., years 1940 to I95I. "Heavy curve, observed ; full taht curve, pio ep dotted curve, pre- mined from records, 1854 to 1939. Ordinates, degrees Fahrenheit. Abscissae, years. dicted, altered in phases and scale as described in the text. All temperatures smoothed by 5-month running means before used. gZ — foe ‘saanjpapgap aanqosaguay uozburysp 44 ryporsag fo Sisayjuts fo ajguvs p—Z alav f9— vr— of— 61— bz— gi— ¥lz Ll— Ig— Leta |e 6 1 -- fre an ¢zz gI— ZS 41+ ox €r (0) Si+ gh eas qIl eb— Iz— 4 — z+ 1€+ 19+ oro he br— 1Z— SI— go-F ZI+ p+ 9To I €z— ei. €z+ Lp S9-+ ge+ 6 $6 Sz— Ocam vi— So-\- 9S++ ze-+ 8 “4yDqJ 2a4bap D fo syIpapuny ui Sadnpavgap aanyosaguiay, “syjuou ur spor4sag “* oun oe ARN ‘aidy "Tey ‘Pa ‘uel oré1 Il I2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 heavy dotted curve of the forecast, as just indicated. Thus the fore- cast in the dotted line can readily be compared with the heavy full curve of the event. To gather more data on the sporadic changes of phase, as yet un- predictable, I synthesized the periodicities from 1934 to 1939 and compared the synthesis with the event. I was surprised to find that in this interval, when, as one might say, the synthesis should be tailored to fit the event, there was less satisfactory accordance than in the fore- casted interval, 1940 to 1951. From September 1936 to September 1938 synthesis and event are exactly in the same phase. From September 1938 to January 1940 immediately preceding my forecast, the synthesis goes ahead of the event by 3 months, as it does in most of my forecasted interval, but is not yet 4 months, as immediately followed in the interval January 1940 to May 1941. The scale level of the synthesis from 1934 to 1939 lies about 3 degrees below that of the event, as it did later, through most of the interval from 1934 to 1939, but less in the months nearer 1934. If the causes of the changes of level and of phase in these comparisons could be unraveled and such changes predicted, a very great advance in meteorology would ensue. I think it can hardly be denied that there is a similarity between the main features of the 12-year forecast and of the event. This simi- larity is especially strongly marked in the rise of temperature from 1940 through 1941, though marred by the excessive rise of forecasted temperature at the end of 1940. The similarity is even more striking from May 1948 to December 1950, 8 to 11 years after the forecast began. But here an additional systematic difference of about 1 degree in level is seen. There are many who are so impressed by the elegance of the meth- od of correlation coefficients as an index of the worth of a forecast, that they are contemptuous of curve comparisons as a test. To me this seems unfair and misleading. For instance, old water mills used to employ tooth and pin gears, irregularly made by ordinary carpenters and having large and variable amounts of backlash. There was really 100 percent correlation in the running of a pair of these gears. But they were often out of step, owing to the combined effects of imperfect spacing and wide backlash. Computed coefficients of correlation would fall far short of 100 percent. In the control of weather by solar variation, obvious and certain though it is, the complexity of the earth’s surface and atmosphere NO. I TEMPERATURE OF WASHINGTON, D. C.—ABBOT LS causes variations in the lag of response to regular periodic variations. Consequently, when it is quite obvious that a pair of curves of forecast and event are related, a rapid rise or decline may be found in one curve slightly in advance of the other. This causes large departures between the two curves and may bring down the computed correlation coeffi- cient to apparent meaninglessness. Mere obstacles to the free opera- TABLE 8.—Forecast of Washington 5-month running mean Fahrenheit temperatures, 1952 to 1959 1952 Jan. 39°1 1954 Jan. 34°4 TOSOMJian. 3727 1958 Jan. 38°8 Feb. 40.4 Feb. 35.7 Feb: 37.3 Feb. 41.0 Mar. 47.3 Mar. 43.4 Mar. 43.7 Mar. 47.1 Apr. 56.9 Apr. 54.5 Apr. 55.2 Apr. 55.8 May 66.2 May 64.8 May 64.1 May 64.7 June 72.6 June 73.1 June 70.6 June 71.2 July 75.7 July 78.4 July: 75).7 July 76.0 Aug. 73.9 Aug. 76.8 Aug. 74.2 Aug. 75.3 Sept. 66.2 Sept. 72.6 Sept. 68.8 Sept. 70.1 Och 15558 Oct6s53 Oct soa7 Oct. 58.8 Nov. 44.2 Nov. 51.7 Nov. 49.1 Nov. 48.6 Dec. 35.2 Dec. 40.8 Dec. 40.5 Dec. 37.8 1953 Jan. 35.3 1955 Jan. 37.4 1957 Jan. 37.6 1959 Jan. 35.6 Feb. 35.9 Feb. 37.4 Feb. 38.4 Feb. 36.6 Mar. 43.1 Mar. 45.1 Mar. 45.0 Mar. 43.3 Apr. 54.2 Apr. 54.3 Apr. 54.5 Apr. 54.6 May 63.7 May 61.8 May 63.7 May 65.6 June 72.4 June 70.3 June 70.8 June 74.3 July 78.9 July 75.9 July 75.5 July 77.8 Aug. 76.9 Aug. 74.3 Aug. 76.0 Aug. 76.2 Sept. 71.6 Sept. 71.4 Sept. 68.1 Sept. 70.4 Oct ores Oct. 26283 Oct 57.1 Oct) 50.2 Nov. 49.8 Nov.ic51.7 Nov. 47.7 Nov. 48.1 Dec. 38.90 Dec. 40.4 Dec. 38.2 Dec. 40.0 tion of a cause may, in the correlation method, so far obscure the cause that it fails altogether of recognition as the cause. Yet, for practical purposes, the forecast may tell the interested agriculturalist quite nearly enough, in time and amount, the change which he wishes to know in advance. I regard the results of this test of forecasting Washington tempera- ture as so promising that I have ventured to synthesize the expected Washington temperatures from 1952 to 1959. This forecast is given in table 8. These forecasted 8 years of Washington temperatures I have reduced from the status of departures from normal to actual temperatures Fahrenheit. In making the forecast I have assumed that the lag between synthesis and event will be reduced to zero, and that 14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I22 the scale of mean temperatures will remain 2 degrees above synthesis, as now prevailing. The comparison of forecast is to be with Weather Bureau Records, means between averages of monthly maxima and monthly minima, at the main Weather Bureau Office, 26th and M Streets, NW., Washington, D. C. Obviously, to check the accuracy of the forecast, the observed temperatures of future years must first be smoothed by 5-month running means. <2?) 1 ee! FERRE Ay _ pens sees! et 4 BEERSy USES! SESE s SERPs es eee Pee aaee Prt fee Pe ae ee Fic. 5.—Washington temperature departures, 1950 to 1952, predicted (light curve) and observed (heavy curve). Correlation, 50.4 = 9.7 percent. Tempera- tures, degrees Fahrenheit. All temperatures smoothed by 5-month running means before used. To fix upon the probable scale difference and lag, I prepared figure 5, in which departures from normal in the synthesis are plotted from the upper zero line and the right-hand scale of ordinates. The departures observed are plotted from the lower zero line and the left-hand scale of ordinates. The plot begins with 1950 and extends through 1952. A lag of one to two months is seen, as stated above, in the years 1950 and 1951, but seems to vanish in 1952. As for the scale, the synthetic values seem to run about 2° Fahrenheit below the observed values in these three years. So I have assumed that the same scale difference and zero lag will continue till 1959, as stated above. In view of unpredictable changes of scale and lag heretofore noted, one hardly hopes that such changes will not occur before the end of this forecast. I can hardly hope to live to see it verified to the end. It is really a forecast for 20 years in advance, beginning with the year 1940. Considering that the basis of my forecast lies in records of 1854 to 1939, centering about 1900, one may even justly say that the fore- cast, 1952 to 1959, is over a half century in advance. For those who prefer correlation coefficients to graphs, figure 5 gives a correlation coefficient of 50.4+9.7 percent with the scale difference of 2° Fahrenheit removed. SMITHSONIAN MISCELLANEOUS COLLECTIONS VOLUME 122, NUMBER 2 NEW AND INADEQUATELY KNOWN NORTH AMERICAN SPECIES OF THE COPEPOD GENUS ‘DIAPTOMUS BY MILDRED STRATTON WILSON Arctic Health Research Center U. S. Public Health Service Anchorage, Alaska (PusLicaTIon 4132) CITY OF WASHINGTON PUBLISHED BY THE SMITHSONIAN INSTITUTION AUGUST 4, 1953 The Lord Baltimore Press BALTIMORE, MD., U. 8 Ae NEW AND INADEQUATELY KNOWN NORTH AMERICAN SPECIES, OF. THE COPEPOD GENUS DIAPTOMUS By MILDRED STRATTON WILSON Arctic Health Research Center U. S. Public Health Service Anchorage, Alaska INTRODUCTION In the preparation of a new key to the calanoid Copepoda for the revised edition of Ward and Whipple’s ‘““Fresh-Water Biology,” some new species of Diaptomus have been recognized and the status and distribution of other species have been clarified. In order that these new forms may be included in the key, the following diagnostic de- scriptions and notes are presented. More detailed treatment is reserved for the future monographic review of the North American species. A considerable part of the present report deals with the species that have in one way or another been confused with Diaptomus shoshone Forbes. It became apparent early in the study of the subgenus Hes- perodiaptomus that it would be necessary to establish the typical form of D. shoshone before it and several closely related species could be correctly separated from one another. All that remains of the orig- inal collection, which is in the Illinois State Natural History Survey, are slides consisting mostly of dissected appendages. These have been found adequate to determine both the important and unknown diagnostic characters of the type. Study of literature and other col- lections, particularly the Marsh and Light accessions in the U. S. National Museum, has shown that several definable forms can be unqualifiedly separated from the typical. Two of these (D. caducus and D. nevadensis) have already been distinguished by Light (1938), though he was unaware that they had been included in published rec- ords of D. shoshone. The others are herein described as new species. The confusion of these species with Diaptomus shoshone has been largely due to the fact that certain fundamental characters of the genus have been neglected in the descriptions of North American diapto- mids. Two of the most important of these are the setation of the antennules of the female, and that of the left side of the male, and the exact form of the left exopod of the male fifth leg. Both of these SMITHSONIAN MISCELLANEOUS COLLECTIONS, VOL. 122, NO. 2 2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I22 characters are significant in the taxonomy of the subgenus Hesperodi- aptomus, and particularly so in the case of D. shoshone and its allies. The setation of the antennule was recognized as a fundamental specific character by Schmeil (1896) in his comprehensive analysis of the genus, and its invariability has been emphasized by Gurney (1931, p. 114). The exception mentioned by Gurney has been clari- fied by Kiefer (1932, p. 512). I have noted, in examination of nu- merous American specimens, that anomalies sometimes occur in the setation, but these are very rare and are recognizable as such because they occur in isolated individuals of a sample and on only one anten- nule of a pair in the female. Since the subgenus Hesperodiaptomus TABLE 1.—Antennule setation in the subgenus Hesperodiaptomus 2 and left side d Segment Species and sex 2 6 10 1 LFol4e els b- 26) «. el eD, COMUCHS. eos a Shes alas O Ol v4: 2. A one. Be 2 SB ee ee hirsutus ...0.000.. fs 3 Ey aa aa a ae eh Oe sere Bee fie enters ol ey as) Gates a ie a ee shoshone ......0+. a ee Me ce Oe a Ls oa novemdecimus ..... Orgies Lier Twenty and @i Pian Derren re Va Te Dish [oad dey pod Peuitine tn iw Big oee SCREG CTA waitin nese EF a Oe Oe ae ee On AOE ENE Rk oS Ie 7 aS HO eee SR UR QR RN OS ala NE Bie or NeVAdENSIS .....06. wal 3. kL a a te he CVSOMU ABS ISES Po arb Met Wine tips Cy) pr eee aycticusis. ty. BEA OSes ive, ele seo tay Bea ee * schefferi—d left may occasionally have 2 on 6, as it always has on the right. belongs to what has been termed the “multisetaceous” group, in which the number of setae on segment I1 is 2, and on segments 13-Ig is either I or 2, it is highly desirable that the setation of all the species be known. It is therefore presented in table 1. The subgenus differs from any group that has been recorded in literature in having a species in which 4 setae are present on segment 2. In addition, some of the proximal segments may have 2 setae rather than the customary single seta. The preliminary consideration that has been given in this study to the structure and distribution of Diaptomus shoshone and the forms closely allied to it suggests that the group as a whole may be valuable material for studies in variation and distribution. Such studies not only might contribute to the zoogeography of this group but also might have wider application in the much-needed evaluation of structural characters. Since the knowledge of variation and distribution is so NO. 2 COPEPODS OF THE GENUS DIAPTOMUS—WILSON 3 incomplete, no reliable analysis can be made as to the systematic status of these forms. It is therefore not superfluous to emphasize that it is of much importance that published records of Diaptomus shoshone and related forms be based upon accurate identification. SYSTEMATIC DESCRIPTIONS DIAPTOMUS (HESPERODIAPTOMUS) SHOSHONE Forbes Figures 1-8 Diaptomus shoshone Forzes, 1893, p. 251, pl. 42, figs. 23-25—-ScHACHT, 1897 (in part), p. 141, pl. 26, fig. 3—MarsH, 1907, p. 431, pl. 28, figs. 2-5; 1920 (in part), p. 8j; 1929 (in part), p. 17—Dopps, 1915a, p. 102, fig. 9; 1915, p. 290, fig. 65; 1917, p. 76; 1924, p. 4. Diaptomus (Hesperodiaptomus) shoshone, Licut, 1938, p. 67. Specimens examined.—The material studied consisted of slides in the type (Forbes) and Schacht collections in the Illinois Natural His- tory Survey; specimens from all the localities reported by Marsh for which slides are available in the National Museum; unpublished rec- ords in the S. F. Light accession in the National Museum; and a recent alcoholic collection, consisting of 57 females and 31 males, collected by J. S. Stanford, Dry Lake, Cache County, Utah. This latter collec- tion agrees with the type material in the basic characters, which have been checked on all the specimens. The descriptive diagnosis and illustrations given here are based upon the Forbes slides, except for the habitus, which has been made from the Utah specimens inasmuch as it is desirable that study of whole specimens be made whenever possible from those that have been undistorted by cover-glass pressure. In all cases the term typical form refers to the type lot (Forbes did not designate an individual type specimen), or to individuals from other samples that agree with the type in the basic characters. The common variations that have been found are given in parentheses. Diagnosis (emended).—Length (after Forbes) : Female, 3.1 mm. ; male 2.59 mm. (Utah specimens, female, 3.7-4.4 mm.; male, 3.0-3.5 mm.). Greatest width in both sexes in the mandibular-maxillary re- gion, the metasome tapering sharply so that the posterior portion is noticeably narrower than the anterior. Metasomal wings of female not produced outwardly, directed posteriorly, reaching to near the end of the swollen portion of the genital segment (not bifid as stated by Forbes). Urosome of female 3-segmented. Genital segment asym- metrical, the lateral areas bearing the minute sensilla produced into prominent lobes, that of the right side larger and directed backward. Caudal rami subequal to segment 3, both margins ciliate. (The illus- VOL. 122 ONS ONIAN MISCELLANEOUS COLLECTI SMITHS opposite page.) 1-14.—(See legend on Fics. NO. 2 COPEPODS OF THE GENUS DIAPTOMUS—wWILSON 5 trations of the female urosome given by Marsh, 1907, and by Dodds, 1915a and 1915b, agree with Forbes’s description and slides and are correct. That of Schacht, 1897, pl. 26, fig. 1, is not of D. shoshone. It was found in checking slides in the Schacht collection that those labeled shoshone female were of a leptodiaptomid.) Antennules reaching to near end of metasome, setation of female and left side of male identical, having 3 setae on segment 2, I seta on 6 and 10, Segments 11 and 13-19: II 13 14 15 16 17 18 19 2 I 2 I 2 I 2 I Right antennule of male with spines of segments 10, 11, and 13 not grossly developed ; that of 10 less than width of segment, those of 11 and 13 hardly longer ; that of 13 a little longer than that of 11. (These spines show considerable individual variation.) Segment 15 without spinous process. Segment 16 with a long, distally placed process (usually varying from about 30-42 percent of the length of the margin of the segment ; I specimen examined has the extreme of 61 percent). The process of segment 23 reaching to the middle of the last segment (rarely beyond), its apex pointed (frequently rounded). Maxilliped of both sexes grossly developed, with greatly enlarged clawlike setae on the inner side of the endopod, the terminal and outer setae much reduced in size. Leg 1 with the spine of exopod 1 long and setiform, reaching to near the end of segment 2. Leg 2 lacking Schmeil’s organ. Leg 5 of female slender. Relative lengths of the exopod and endo- pod of Forbes’s slide 507 (fig. 2): Exopod 1 Exopod 2 (outer) Endopod Endopod setae 40 36 35 19:22 The endopod indistinctly segmented (or distinctly so), armed apically with large, flat spinules; the setae unornamented (only a few speci- mens show, at high magnification, scattered hairs on these setae; Schacht’s figure is undoubtedly of shoshone, but the dense plumosity Fics. 1-8.—Diaptomus (Hesperodiaptomus) shoshone Forbes: 1, Female, metasome segments 5-6 and urosome, dorsal; 2, female, leg 5; 3, male, right antennule, apical segments; 4, male, right antennule, segments 15-16; 5, male, leg 5, posterior view; 6, male, leg 5, left exopod, segment 2, anterior view; 7, ies antennule, setae of segments 1-6; 8, female, antennule, setae of segments 13-19. Fics. 9-11.—Diaptomus (H.) novemdecimus, new species: 9, Female, leg 5; 10, male, leg 5, anterior view; 11, male, leg 5, processes of left exopod, anterior view. Fics. 12-14.—Diaptomus (H.) kenat, new species: 12, Male, leg 5, left exopod and endopod, anterior view; 13, male, right antennule, apical segments; 14, male, leg 5, posterior view, with detail of lateral spine. 6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 of the endopod setae is an exaggeration). Length of the second exo- pod segment three times its greatest width, the whole of the claw very slender, evenly tapered from the area of the third exopod segment. Setae of the third exopod short, the inner the longer. Leg 5 of male, right: Claw swollen at its base (not divided as shown by Forbes) ; shorter than the rest of the leg, about 25: 33. Basipod I without inner lamella, sensillum on well-developed cutic- ular prominence. Basipod 2 without prominent raised ridge or pro- trusion. Exopod 2 nearly parallel-sided, with small spinule on inner posterior face; lateral spine straight, shorter (or a little longer) than the width of the segment. Endoped a little longer than the inner mar- gin of exopod I (I- or 2-segmented). Left leg reaching to about the middle of the right second exopod segment. Basipod 2 with the proximal inner half of the anterior face hardly protuberant (individually variable). Segment 1 of the exopod considerably longer than segment 2 (about 3:2). Inner process of distal segment a long, slender, tapering, distally directed spine whose basal portion is hardly widened and which reaches to the end of the outer process (or farther) ; its length more than half that of the outer margin of exopod 2 (measured to the base of distal process). The medial spinules of the distal pad very gross, those of the posterior and anterior faces very small, arranged in groups. Endopod 1-(or 2-) segmented. Distribution —The type locality is Lake Shoshone, Yellowstone Na- tional Park, Wyo. Other Yellowstone Park records given by Forbes are: Lewis Lake, Yellowstone Lake, Swan Lake, and an alkaline pond. It has been determined from examination of the Marsh slide col- lection in the National Museum that only the following records pub- lished by Marsh (1920, 1929) are of typical shoshone: Yellowstone Lake, Wyo.; Corona, Irwin, and Pikes Peak, Colo.; Nioche Valley and Salinas, Wasatch Mountains, Utah. The Toronto, Canada, record is questionable ; the only slide available is of a cyclopoid. All the other Marsh records and also those of Carl (1940) are referable to one or another of the species discussed below. The Light accession contains three unpublished records of typical shoshone. One is an additional Rocky Mountain locality: A pond 28 miles east of Cooke, Mont., 9,000 feet, A. G. Rempel, collector. The others are from the Sierra Nevadas of California: Iceberg Lake, Madera County, 10,100 feet, P. R. Needham; Helen Lake, Fresno County, 10,896 feet, H. J. Rayner. Dodds, whose illustrations agree with the typical form, has pointed out that in regions of the Rocky Mountains studied by him, Diaptomus NO. 2 COPEPODS OF THE GENUS DIAPTOMUS—WILSON 7 shoshone was found only in lakes at very high altitudes (around 9,000- 12,000 feet). The elevation given for the type locality, Lake Shoshone, was 7,740 feet (Forbes, 1893, p. 214). On the basis of present knowledge the distribution of typical sho- shone appears to be restricted. All the authentic records are from high altitudes (6,000-12,000 feet) in the Rocky Mountains or Sierra Ne- vadas. It is not intended to suggest here that this is proof of the altitudinal distribution of the species. It should be pointed out, how- ever, that a trend is apparent which is worthy of investigation and which may have bearing on the zoogeography of this and some of the species discussed below. DIAPTOMUS (HESPERODIAPTOMUS) NOVEMDECIMUS, new species Figures 9-11 Type lot.—Slides from the Light collection consisting of mounted appendages of both sexes. Temporary pond, 2 miles south of Charlo, Flathead Reservation, Mont., elevation about 3,000 feet, Gordon B. Castle, April 28, 1940. Occurring with D. wardi. Type slide, U.S.N.M. No. 94624. Since only mounted appendages are available, no measurements or description of the habitus can be given. The size of the appendages indicates that the body size of both sexes is similar to that of D. shoshone. Diagnosis.—Antennule setation of female and left side of male: 3 setae on segment 2, I on segments 6 and 10. Segments 11 and 13-19: II 13 14 15 16 17 18 19 2 I 2 I 2 I 2 2 Right antennule of male: Spines of segments 10, 11, and 13 not long, that of 13 of irregular shape, longer than that of 11. Segment 15 lacking a process; 16 with a distally placed process, its length about 20 percent of that of the segment. Process of segment 23 stout, straight, the apex pointed, reaching to near the end of segment 25. Leg 5 of female: Exopod 1 (outer margin) a little longer than exopod 2, 47:45. Exopod 2 wider at base than in typical shoshone, the width to total length, 20: 45 ; the claw not so slender as in shoshone, gradually tapered beyond the middle. Endopod 2-segmented (or indistinctly so), longer than the inner margin of exopod 1. The inner seta of exopod 3 subequal to, or not as stout or long as, the outer. Leg 5 of male: Claw not swollen at base, nearly as long as the rest of the leg, 37:35. Right basipod without modification or armature. Right exopod 2 somewhat enlarged, with a blunt spinule on inner pos- terior face. Right endopod 2-segmented, longer than exopod 1. Left 8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 basipod 2 with prominent inner proximal protrusion; serrate cuticle particularly conspicuous on inner anterior face (such a serration is a rudimentary structure which may be present or absent in hespero- diaptomids). Exopod 1 longer than exopod 2 (about 37:25). Inner process a stout spine with a slightly widened base, reaching to near the end of the distal process, its length a little less than one-half that of the outer margin of exopod 1 (to base of distal process). The trivial name of this species refers to segment 19 of the antennule, which differs from that of shoshone in the presence of 2 setae rather than 1 seta. The question of whether D. novemdecimus is a subspecies of D. shoshone should be considered in future studies. The status of species has been given here because of the antennular setation, which has long been considered by competent authorities to be a stable spe- cific character. In the several samples of typical shoshone that have been examined no individuals of either sex have been found to have 2 setae on segment 19. In addition, the two can be separated by two definable characters of the male fifth leg which also differ in other species of Hesperodiaptomus—that is, the length and shape of the claw and the size and shape of the inner process of the left exopod. This combination of a pattern of close structural similarity and de- finable differences in seemingly basic characters appears to make these two species valuable for studies in the interrelationships of the hes- perodiaptomid group and the problem of evaluation of characters. Until adequate knowledge of variation and distribution is available, it is my opinion that any attempt at subspeciation is both arbitrary and premature. DIAPTOMUS (HESPERODIAPTOMUS) KENAI, new species Figures 12-17 Diaptomus shoshone, MarsH, 1920 (in part), p. 8j; 1929, p. 17—CaRL, 1940, p. 81; ? 1944, p. 30. ? Diaptomus shoshone, THACKER, 1923, p. 88. Type lot.—t1oo specimens of both sexes. Shallow mountain pond on Palmer Creek Road, about 12.6 miles southeast of Hope, Kenai Peninsula, Alaska, Charles S. Wilson, August 24, 1949. Occurring with D. tyrrelli. Holotype female, U.S.N.M. No. 94632; allotype male, U.S.N.M. No. 94633. Diagnosis.—Length (dorsal view): Female, 2.03-2.08 mm.; male, 1.87-2.04 mm. The wings of the last metasomal segment of female a little asym- metrical, the lateral tip of each side drawn out, that of the right side larger than the left. Urosome of female 3-segmented. Genital seg- NO. 2 COPEPODS OF THE GENUS DIAPTOMUS—WILSON 9 ment symmetrical, without lateral protrusions. Third segment and caudal rami subequal in length; the greatest width of the rami a little more than one-half their length (21: 35), ciliate on inner margin. Antennules of female reaching to near the middle of the genital segment. Numerical setation: 3 on 2, I on 6 and Io, 2 on II, and 1 on 13-19. The seta of segment 1 short, not reaching to the end of segment 2; all setae comparatively short, none reaching beyond the middle of the succeeding three segments. Left antennule of male with same setation as female. Right antennule of male with the spines of 10, 11, and 13 thick, none longer than the width of their segments, proportions to one an- other, 11:16:21. Segment 15 without a process; segment 16 with a distally placed process reaching beyond the end of the segment, its length about 28 percent of the length of the segment. The process of segment 23 reaching to about the middle of the last segment, straight or outcurved. Maxilliped not so grossly developed as in shoshone. Setiform spine of exopod segment 1 of leg 1 only about half the length of segment 2. Leg 2 lacking Schmeil’s organ. Leg 5 of female: Exopod 1 (outer margin) a little longer than exopod 2 (35: 33). Proportion of greatest width to length of exopod 2, about 15:33; this great width gradually decreased throughout the length of the “claw” to near its apex where it may be abruptly nar- rowed. The outer seta of exopod 3 always stouter and usually much longer than the inner. Endopod 2-segmented, as long as, or longer than, the inner margin of exopod 1. The apex more or less prolonged on the inner side, armed with a few short spinules, the length of the subterminally placed setae about half that of the endopod. Leg 5 of male, right: Claw short, only a little longer than the exo- pod ; its base hardly swollen. Exopod 2 with spinule on the posterior inner face; the lateral spine short, characteristically incurved on the inner side. Endopod about as long as exopod 1, I- or 2-segmented. Left leg reaching to a little beyond the right exopod 1. First segment of exopod a little longer than the second. The inner process a broad- based spine, not reaching to the end of the distal process. This species is the only one of the shoshone group that has the seta- tion of the antennule reduced to one on segments 13-19. This char- acter distinguishes it from all the others, and particularly from D. caducus, to which it would appear to be most closely allied. The female fifth leg has a distinctive shape given to it by the widening of the second exopod segment. The inner process of the left exopod of the male fifth leg is distinguished by the broadened base from which it tapers to a slender spine. SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 Lif, S. 15-28.—(See legend on opposite page.) Fic NO. 2 COPEPODS OF THE GENUS DIAPTOMUS—WILSON II Distribution —tThe specimens reported as shoshone by Marsh from the Pribilof Islands, Alaska, and from Wheat Meadows, Calif., are referred to this species. Marsh is supposed to have identified the speci- mens reported by the Thackers, but slides from their British Columbia localities have not been found in the National Museum collections. They have here been questionably referred to D. kenai because the record falls within the distribution pattern of this species. Slides labeled D. shoshone by Carl and reported in the British Columbia rec- ords of his 1940 paper are in the Light accession and have been iden- tified by me with D. kenai. In addition to these collections and the type lot from Alaska, a large number of collections from Oregon and California have also been examined and referred to this species. These records are extensive enough to show that the species is not altitudin- ally restricted. In Oregon and California it is rare on the coast but of frequent occurrence in the Cascade and Sierra Nevada mountain ranges, where it has been collected to an elevation of 9,000 feet. The species also occurs in the Cascades of Washington, having been found in a collection from Lake George, Mount Rainier National Park, referred to me by C. C. Davis. DIAPTOMUS (HESPERODIAPTOMUS) CADUCUS Light Diaptomus caducus Licut, 1938, p. 67, figs. 1-5, 23. Diaptomus shoshone, MarsH, 1929 (in part), p. 17. Diaptomus sicilis, CARL, 1940 (in part), p. 81. Specimens reported by Marsh from Vancouver Island, British Columbia, are referable to this species. A slide labeled D. sicilis by Carl is present in the Light collection; the locality given is: Pond, Victoria, British Columbia. This specimen is clearly identifiable from the antennular setation as caducus. Diaptomus caducus has been adequately described by Light, and if proper attention is given to the highly important setation of the anten- Fics. 15-17.—Diaptomus (Hesperodiaptomus) kenai, new species: 15, Female, metasome segments 5-6 and urosome, dorsal, with detail of right “wing”; 16, female, leg 5, with detail of lateral setae of exopod; 17, female, antennule, setae of segments 13-10. Figs. 18-25.—Diaptomus (H.) hirsutus, new species: 18, Female, metasomal wings and distal portion of urosome, dorsal; 19, female, leg 5, with detail of lateral setae of exopod (type lot); 20, female, leg 5, endopod with elongate setae (lot from Eldorado County, Calif.) ; 21, female, antennule, segments I-10, showing setae of segments I, 2, 3, 6, and 10; 22, male, leg 5, posterior view; 23, male, leg 5, profile of protrusions of right basipod segments; 24, male, right antennule, apical segments; 25, male, leg 5, detail left exopod and endopod, anterior view. Fics. 26-28.—Diaptomus (H.) nevadensis Light: 26, Female, metasome seg- ments 5-6 and urosome, dorsal; 27, female, leg 5, with detail of apex of endopod, 2 different views; 28, female, leg 5, detail of lateral setae of exopod. I2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 nules (table 1) there should be no confusion of this species with any other known hesperodiaptomid. The species is unique among known diaptomids in having 4 setae rather than the usual 3 on the second segment in both sexes, including the right antennule of the male. Oc- casional specimens have been found in which 2 setae are also present on segments 4-7 on one antennule of a pair, apparently an anomaly rather than a variation of the species. Present knowledge of distribution confines this species to the Pacific coast areas from central California to British Columbia, where it characteristically occurs in temporary ponds and roadside ditches. The one mountain record given by Light is referable to the new species described below. DIAPTOMUS (HESPERODIAPTOMUS) HIRSUTUS, new species Figures 18-25 Diaptomus caducus LicHtT, 1938 (in part), p. 69. A single female from Granite Lake, Amador County, Calif., was incorrectly assigned to caducus by Light. Another collection made at a later date from the same locality yielded numerous specimens and has been made the type lot of the new species. Type lot—100 specimens of both sexes. Granite Lake, Amador County, Calif., 6,800 feet, June 22, 1937, R. E. Smith. From Light collection in the U. S. National Museum. Holotype female, U.S.N.M. No. 94628; allotype male, U.S.N.M. No. 94629. Other California mountain collections in the Light accession refer- able to this species are: Several ponds in Lassen National Park; pond at Columbia, Sierra County ; pond near Summit Lake, Shasta County ; Silver Ford, Eldorado County. Diagnosis —Length : Female, about 1.88 mm. ; male, about 1.79 mm. Greatest width in both sexes in the middle of the cephalic segment, that of the female about 28 percent of the length. Posterior margin of metasomal wings of female slightly bifid, the outer portion pro- duced laterally. Urosome of female 3-segmented. Genital segment symmetrical, not swollen laterally. Caudal rami shorter than segment 3 (about 29: 35) ; their width about 71-76 percent of the length ; both margins and entire dorsal surface hairy. Urosome of male symmet- rical, length of caudal rami subequal to segment 5, with hairs on the inner margins only. Antennules reaching nearly to end of metasome. Those of female having 3 setae on segment 2, I on 6, 2 on 10, 11, and 13-19; seta of 3 unusually long, reaching about to end of segment 10. Left antennule NO. 2 COPEPODS OF THE GENUS DIAPTOMUS—WILSON 13 of male differing from that of female in having 1 seta on segments 10 and 13 (2 on 11 and 14-19), seta of 3 reaching about to segment 8. (This sexual difference found in all the lots of specimens examined.) Right antennule of male: Length of spines of segments 10 and 11 less than the width of their segments and shorter than that of 13, which is exceedingly slender and reaches about to the middle of segment 14; segment 16 with a short, distally placed process not reaching beyond the end of the segment. Process of segment 23 spatulate, its tip always rounded, reaching to the end of 24 or to the middle of 25. Leg 2 lacking Schmeil’s organ. Leg 5 of female: Endopod 2-segmented, as long as, or longer than, exopod I ; apex truncate, with few spinules; setae subequal in length to endopod or longer. Leg 5 of male, right: Claw subequal to (or a little longer than) the rest of the leg. Basipod 1 without prominent inner lamella. Basi- pod 2 with raised ridge on posterior surface, produced proximally into a rounded lobe (fig. 23 shows profile of ridge, without pressure) ; this structure reduced to indefinite shape by cover-glass pressure (fig. 22). Exopod 2 with small spinule on inner posterior face, lateral spine a little shorter (or longer) than width of segment. Left exopod: Segment 1 a little longer than segment 2, 19:15. Inner process a tapered spine with a narrowly expanded base. Distal pad with minute spinules arranged in groups on the anterior side ; those of the posterior side larger and thickly set, extending far up on the face of the segment. The trivial name of this species refers to the presence of hairs on the dorsal surface of the caudal rami of the female, a condition un- usual in Diaptomus. D. caducus has been found to have hairs on both surfaces of the caudal rami, but they are few in number and scattered, in contrast to the numerous thickly set hairs of hirsutus. The two species appear to be related. They are the only ones known in which the segments of the female antennule proximal to segment I1 have some of the setae multiplied. D. hirsutus is clearly defined in its characters and the male is strikingly different from that of caducus not only in the setation of the left antennule (table 1) but in several of the characters of the fifth leg (greater length of the claw, modifica- tion of the right basipod 2, and the elongate form of the inner process of the left exopod). These characters, as well as those of the female, have been found in all the several collections examined. Present knowl- edge of distribution confines caducus to the Pacific coast area and hirsutus to the mountains of northeastern and north-central California. 14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 DIAPTOMUS (HESPERODIAPTOMUS) NEVADENSIS Light Figures 26-28 Diaptomus nevadensis LicHT, 1938, p. 60, figs. 6-7. Diaptomus shoshone, MarsuH, 1929 (in part), p. 17. The specimens reported by Marsh as shoshone from Devils Lake, N. D., are referable to this species.* Only males were present in the type lot from Nevada. Since publi- cation, Light collected and identified the species from another Nevada and several California localities, as listed: An alkaline lake, Washoe County, Nev., 5,000 feet; Honey Lake and Horse Lake, Lassen County, Calif.; Middle Lake, Cedarville, Modoc County, Calif. The above collections contained female’, from which an allotype specimen has been selected for description. The male in the new Nevada and California collections shows no significant differences from that described by Light from the type lot, except that the lateral spine of the right second exopod of the fifth leg is noticeably longer, equaling at least the width of the segment (in the type specimen, which has been examined, it is considerably less). The typical male is characterized by: Large size (about 3.5 mm.). Left antennule: 2 setae on II, I on 13-19. Right antennule: Spines of 10 and 11 exceptionally slender, that of 11 longer than that of 13. Short spinous processes on both segments 15 and 16. Process of segment 23 long and curving. Leg 5: Claw comparatively short, only a little longer than the exopod ; its base swollen. Right basipod 1 with prominent inner lamel- lar expansion. Second exopod segment of right leg greatly enlarged, with a very small spinule on inner posterior face. Left exopod: Seg- ment I a little longer than segment 2; the inner process a very short, but broad-based, toothlike spine, not reaching beyond the base of the distal process. Distal pad having the spinules closely set, not arranged in groups. The North Dakota specimens differ from the Nevada and California males in having the second exopod segment of the right leg not con- spicuously enlarged, and in the absence of the short spinous process on the 15th segment of the right antennule. The female shows no differences. Diagnosis of female—Allotype female: U.S.N.M. No. 94627. 1 Specimens recently reported as D. shoshone by J. E. Moore (Can. Journ. Zool., vol. 30, p. 422, 1952) from saline lakes in Saskatchewan have also been examined and found to be D. nevadensis. NO. 2 COPEPODS OF THE GENUS DIAPTOMUS—WILSON 15 Honey Lake, Lassen County, Calif., June 1938, collected and identi- fied by S. F. Light. The female is large but comparatively slender. Length 3.85-4.05 mm. Greatest width only 23.6 percent of length. Metasomal wings not expanded or produced laterally, symmetrical. Urosome 30 percent of total length, 3-segmented. Genital segment widened proximally with slight lateral protrusions, the sensillum of the right side borne on a larger protrusion than that of the left. Caudal rami subequal in length to segment 3, proportions of length to width about 3: 2; ciliate on both margins. Antennules reaching to the middle of the genital segment. Numeri- cal setation: 3 on segment 2, 1 on 6 and 10, 2 on II, and I on 13-19. The seta of segment 1 not elongate, hardly reaching to the middle of segment 2; that of 3 reaching to end of segment 6. All the segments extremely slender, the length of segments 17-19 are 4 to 5 times their width. Setae of segments 7, 9, and 14 exceptionally long, that of 7 the longest, reaching to middle of segment 13. Relative proportions of these setae: Segment 7: 265; segment 9: 210; segment 14: 175. Maxilliped very gross, as in shoshone, the endopod shorter than the preceding basipod segment, and armed with very stout clawlike setae. Leg 2 lacking Schmeil’s organ. Leg 5 elongate and slender, the total exopod almost twice the length of the basipod. Relative lengths: Basipod 1+ 2 Exopod I Exopod 2 90 90 85 The inner spine of exopod 3 much stouter and longer than the outer spine, armed with stout marginal spinules. Endopod shorter than inner margin of exopod (61:85), indistinctly 2-segmented, the inner apex produced into a sharp prolongation which is armed with coarse hairs ; the terminal setae about two-thirds the length of the endopod. Although it lacks any striking modification of the second basipod segment in the male right fifth leg, D. nevadensis appears to be refer- able to the eiseni rather than to the shoshone group of Hesperodiapto- mus. This is evident in the male fifth leg in the regular arrangement of the spinules of the distal pad of the left exopod and the prominent inner lamellar expansion of the first basipod segment ; and in the right antennule by the presence of a spinule on the fifteenth segment, which though not always present in members of the eiseni group, has not yet been found in those of the shoshone group. The fifth leg of the female is strikingly similar to that of typical etseni from which it can be distinguished by the prominent prolongation of the apex of the endopod ; in eiseni the endopod has only a minute production of the apex. 16 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 DIAPTOMUS (HESPERODIAPTOMUS) SCHEFFERI, new species Figures 33-42 Diaptomus shoshone var. wardi, JuDAY AND MutTTKOWSKI, I915, p. 23, fig. I, A-E. Diaptomus wardi, MArsH, 1920, p. 8j, pl. 3, fig. 10; 1929 (in part), p. 23. This interesting Pribilof Island species was erroneously identified by Juday and Muttkowski as wardi Pearse, which they considered to be a variety of shoshone. Marsh (1920, 1929) accepted this incorrect identification but did not refer the species to shoshone. Study of Montana specimens which are referable to typical wardi (see below) show several distinctive differences between the two forms. The most striking and the one that has hitherto been misinterpreted is the structure of the protrusion of the second basipod segment of the male right fifth leg. There has been available for study some of the original material examined by Juday and Muttkowski, now in the Marsh collection in the National Museum, and additional specimens also from the Pribilof Islands, referred to Dr. Light by Dr. Victor B. Scheffer, chief of Pribilof Fur Seal Investigations, U. S. Fish and Wildlife Service. The species is named for Dr. Scheffer. Type locality—Upper Ice House Lake, St. Paul Island, Pribilof Islands, Alaska. Holotype female, U.S.N.M. No. 94625; allotype male, U.S.N.M. No. 94626. Diagnosis.—Length: Female, about 2.66 mm.; male, about 2.5 mm. Urosome of female 3-segmented, symmetrical, the sensilla borne on very slight lateral protrusions. The caudal rami longer than the third segment (15:11) with hairs only on the inner margin. Antennules of female reaching about to the middle of the genital segment. Numerical setation: 3 on 2, I on 6 and 10, 2 on II, I on 13-19. The seta of segment I reaching to the middle of segment 4; that of 3 subequal in length to that of 1, reaching to near the end of segment 6. Left antennule of male usually armed as in the female, the seta of segment 1 not so long, reaching to the middle of 2, that of 3 to the middle of 7. The right antennule differing from the left in having 2 setae on segment 6 (occasional specimens have 2 setae on the left, but this is not usual) ; spines of segments 10, 11, and 13 only moderately developed, the length of all less than the width of their segments, that of 11 longer than that of 13. The midportion of the antennule only moderately swollen, segment 15 lacking a process, that on 16 short, distally placed, its length about 15 percent of the length of the segment. The process of segment 23 usually long, slim, always pointed, reaching to near the end of, or beyond, the last segment, the NO. 2 COPEPODS OF THE GENUS DIAPTOMUS—WILSON 7, inner edge usually smooth, but it may have one to several rounded notches. Leg 5 of female slender throughout. Exopod segments subequal to one another, claw of exopod 2 very slim, Lateral seta of exopod 2 shorter than third exopod segment. Outer seta of exopod 3 very short and narrow, about one-half the length of the inner which is usu- ally stout (slim in some specimens), armed with spinules. Endopod a little shorter than the inner margin of exopod 1, indistinctly 2-seg- mented, or distinctly so ; the apex truncated, without apical production, armed with a few stout spinules and hairs. The setae set terminally, the outer the longer; proportions of endopod to outer seta to inner seta, 38:28:17. The setae always armed with short stout hairs, often plainly visible at low power. Leg 5 of male, right: Claw about as long as the rest of the leg, slender, curving, symmetrical throughout. Basipod 1 with moderately expanded inner protrusion. Basipod 2 with long heavy ridge on posterior face, and a rectangular lamella placed just above the middle of the inner margin; this lamella clearly not a mere continuous pro- trusion of the segmental body but a cuticular outgrowth consisting of a heavy medial portion and an outer membrane. Exopod 2 lacking the usual spine of the inner posterior face. Left leg: Basipod 2 with the proximal inner portion protruding. Second exopod segment a little longer than the first. Both pads large; the distal with its spine- lets thickly set and not arranged in groups. The inner process a short slender spine swollen at its base, reaching a little beyond the edge of the pad. DIAPTOMUS (HESPERODIAPTOMUS) WARDI Pearse Figures 29-32 Diaptomus wardi PEARSE, 1905, p. 148, pl. 13, figs. 1-4. The type locality of D. wardi is Spokane, Wash. So far as is known, types do not exist in any available collection, although Juday and Muttkowski (1915) mentioned that they examined specimens referred to them by Pearse. Marsh’s (1920) figure of D. wardi from Pribilof Island material is D. schefferi. The confusion of these two species would be difficult to clarify without specimens of D. wardi. Fortunately the Light collection con- tains slides on which are appendages of two unidentified females (leg 5) and two males (leg 5 and antennules) which are so like Pearse’s illustrations of D. wardi that there can be no doubt of their identity. These specimens occurred in the Montana collection with Fics. 29-42—(See legend on opposite page.) NO. 2 COPEPODS OF THE GENUS DIAPTOMUS—WILSON 19 Diaptomus novemdecimus, described above. This apparently consti- tutes the first valid record of the species since its description. The protrusion of the second basipod segment of the male right fifth leg is not at all like the lamella on the medial margin of D. schef- feri, which is definitely of cuticular origin. That of wardi appears instead to be an outwardly projecting lobed protrusion of the proximal inner portion of the segment itself. Until unmounted appendages not distorted by cover-glass pressure can be examined, its exact structure may not be determinable, but one of the slides contained a profile view which appears to be quite natural (fig. 29). In the other mount, the outline of the protrusion is clearly visible, though flattened (fig. 30). It appears to be of the nature of that described above for D. hirsutus. The Montana specimens agree with Pearse’s description in other characters of the male fifth leg: The elongate cuticular prominence of the right basipod 1 which bears the minute sensillum ; the very long endopod of the right leg; the extremely slender claw subequal to the rest of the leg; and the structure of the left exopod and the inner process, similar to D. schefferi. These characters preclude possibility of identity with D. shoshone. Pearse did not indicate a minute spinule on the posterior face of the second exopod, which is present in the Montana specimens. The process of segment 23 of the right antennule agrees exactly with that shown by Pearse; it reaches beyond the apex and is rounded at the tip. Segment 6 has only 1 seta, and the spines of segments 10, 11, and 13 are all longer than the width of their seg- ments, that of segment 11 longer than that of 13; both segments 15 and 16 have minute processes, that of segment 16 is at the middle of the segment, thus differing from the usual distally placed lamelli- form process of other hesperodiaptomids. The left antennule has 2 setae on segment 11 and 1 on 13-19. Unfortunately, the antennule of the female had not been dissected, and it can only be assumed for the present that its setation is like that of the male.’ 2 Whole specimens of D. wardi have been examined since this report was first written. The number of setae on these segments of the female antennule is the Fics. 29-32.—Diaptomus (Hesperodiaptomus) wardi Pearse (Montana): 20, Male, leg 5, right basipod (profile view of inner protrusion of basipod 2) ; 30, male, leg 5, anterior view; 31, female, leg 5, with details of endopod apex and exopod setae; 32, male, right antennule, apical segments. Fics. 33-42—Diaptomus (H.) schefferi, new species: 33, Female, rostral fila- ments and segments 1-3 of antennule (with detail of setae of segments I and 3) ; 34, male, leg 5, posterior view; 35, male, leg 5, right basipod 2 and endopod; 36, female, leg 5; 37, female, leg 5, detail of lateral setae of exopod; 38, female, leg 5, detail of endopod apex and setae; 39, male, left antennule, setae of seg- ments 1-6; 40, male, right antennule, apical segments, with variation of process of segment 23; 41, male, leg 5, detail of left exopod segment 2, anterior view; 42, male, right antennule, segments 6-16, showing setae of 6, and spines and processes of other segments. 20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 The female fifth leg is exactly like that illustrated by Pearse, though it appears to be more slender. The endopod has two well-developed, equal, nonplumose setae, about half the length of the endopod which is very slightly produced between them. The setae of exopod 3 are very short and subequal, that of exopod 2 is very minute. DIAPTOMUS (ARCTODIAPTOMUS) ARAPAHOENSIS Dodds Diaptomus arapahoensis Dopps, 1915a, p. 99, figs. 3-6. Diaptomus bacillifer, MARSH, 1924 (in part), p. 485; 10920, p. 8. Marsh (1920) reported the occurrence of the Eurasian species Diaptomus bacillifer on the Arctic coast of Canada and on St. Paul, Pribilof Islands. In 1924 he supposedly extended its range in North America by placing in synonymy with it the species arapahoensis, de- scribed by Dodds from the Rocky Mountains of Colorado. I have examined Marsh’s specimens of bacillifer and find his identification to be correct. Further examination of cotypes of arapahoensis, which are in the U. S. National Museum, and a new collection in the Light accession, from the Rocky Mountains of Montana (Hidden Lake, G. B. Castle collector), indicates that Dodds’s species is not referable to D. bacillifer as Marsh had supposed. The fifth leg of the male in most groups of Arctodiaptomus shows, as in many species of Hesperodiaptomus, very close structural simi- larity, and it is necessary to take into consideration all the characters of the copepod when making identifications. The male fifth leg of arapahoensis is built on the same general plan as that of bacillifer. The most noticeable difference is the presence of a large, cuticular, spinelike structure on the midposterior face of the right second exo- pod segment. This is absent in bacillifer but is similar to that found in other species (salinus, acutilobatus). This process is much larger than depicted by Dodds. The setation of the female antennules and the left male antennule of the Canadian and Alaskan specimens of bacillifer agrees with that given by several authors for Eurasian specimens. There are 2 setae on segments II and 13 and I on segments 14-19, and the seta of seg- ment 1 in the female is very long. Diaptomus arapahoensis has been found to have the following setation in the female: II 13 14 15 16 17 18 19 2 2 I 2 I 2 I I The seta of segment I reaches to near the end of segment 5 and is sparsely plumose, being similar in this to bacillifer. The male left same as in the male. The seta of segment I is very long, reaching about to segment 12, NO. 2 COPEPODS OF THE GENUS DIAPTOMUS—WILSON 21 antennule differs from the female in having 1 seta on all segments 13-19. This difference exists in both the type (Colorado) and Montana collections. D. arapahoensis bears unmistakable resemblance to the Asiatic species D. acutilobatus Sars (1903). The antennule setation of the female agrees with that given for this species by Gurney (1931, table, p. 115). In order that its exact identity may be known, and particu- larly since there is a difference in the antennule setation of the two sexes, a fact not known for acutilobatus, it appears best to await com- parison of actual specimens of the two forms, before a decision as to their conspecificity is made. DIAPTOMUS (LEPTODIAPTOMUS) PRIBILOFENSIS Juday and Muttkowski Diaptomus pribilofensis JupAY AND MutTTKowSKI, I015, p. 25, figs. 1-6. Diaptomus tyrelli, MARSH, 1915 (in part), p. 459; 1929, p. 23.—Hooprr, 1947, p. 80. This is a form widely spread in Alaska and western Canada and has for years been considered synonymous with D. tyrrelli (corrected spelling). It is closely allied to D. coloradensis from the Rocky Moun- tains and forms with it and the Asiatic species Diaptomus angustilobus Sars (1898) a group of seemingly allopatric species. Its supposed synonymy with tyrrelli has been unfortunate in obscuring the pattern of its distribution and its closer relationship to the other species of the group. Specimens reported by Hooper as tyrrelli from western Canada have been examined and identified as pribilofensis. DIAPTOMUS (EUDIAPTOMUS) GRACILIS Sars Diaptomus gracilis is a well-known Eurasian species new to North American fauna. It has been found recently in several of my Alaskan collections. It appears to be common in the Arctic regions of Alaska, having been found on the western coast (lakes of the lower Yukon River and Bristol Bay areas) and on the Arctic slope at Umiat. In south-central Alaska it occurred in collections of the Kuskokwim River area at McGrath and in Wonder Lake, Mount McKinley National Park. DIAPTOMUS (AGLAODIAPTOMUS) MARSHIANUS, new species Figures 43-51 Type lot—13 females, 45 males. Lake Jackson, Leon County, Fa., April 3, 1950, Murray H. Voth collector. Holotype female, U.S.N.M. SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 22 Fics. 43-58.—(See legend on opposite page.) NO. 2 COPEPODS OF THE GENUS DIAPTOMUS—WILSON 23 No. 94634; allotype male, U.S.N.M. No. 94635. Occurring with D. (Arctodiaptomus) floridanus Marsh and D. (Skistodiaptomus) mis- sissippiensis Marsh. Diagnosis—Length, dorsal view : Female, 1.55-1.89 mm. ; male, 1.3- 1.58 mm. Greatest width of female in segments 2 and 3, equaling about 28 percent of the length. Metasomal segment 5 with an unusual dorsal protuberance consisting of an erect cuticular frill, placed mostly on the right side. The wings of the last segment not produced laterally, the inner portion rounded so as to form a lobe in dorsal view. Urosome of female 3-segmented. Genital segment noticeably asym- metrical, the right side being very tumid. Caudal rami longer than segment 3, 25:20, their width 64 percent of their length, ciliate on inner margin only; the inner dorsal seta as long as the inner caudal seta. Antennules reaching beyond the caudal rami by the last 2-3 seg- ments. Numerical setation: 2 on segment II, I on segments 13-19. The seta of segment 1 short, reaching to the middle of segment 2, that on 3 reaching to segment 6. Setae of segments 17, 19, 20, and 22 stiff and uncinate, their length less than, or equal to, that of the segment. Setation of left antennule of male like that of the female, including the uncinate setae. Right antennule of male having spines of 10 and 11 longer than the width of their segments, that on segment 13 longer than that of 11, strongly outcurved ; segments 15 and 16 with spinous processes. The process of segment 23 reaching to about the middle of 24, outcurved, accompanied by a narrow membrane. Maxilliped not grossly developed, the distal lobe of the basal seg- ment with 3 setae in both sexes. Schmeil’s organ present on the endopod of leg 2. Leg 5 of female: Basal segment with large sensillum on broad base. Exopod 1 and 2 subequal in length, exopod 3 not separated. Seta of exopod 2 present, set closely with the setae of exopod 3; the inner seta with marginal serrations. Endopod longer than inner margin of Fics. 43-51.—Diaptomus (Aglaodiaptomus) marshianus, new species: 43, Female, metasome segments 5-6 and urosome, dorsal; 44, female, metasome segments 5-6, lateral view; 45, female, leg 5, with detail of lateral setae of exopod; 46, female, leg 5, detail of endopod setae; 47, male, right antennule, spines and processes of segments 10-16; 48, male, leg 5, right basipod (with profile of inner protrusion) and outline of endopod; 49, female, antennule, de- tail of uncinate seta of segment 19; 50, male, leg 5, posterior view; 51, male, right antennule, apical segments. Fics. 52-58.—Diaptomus (Mastigodiaptomus) texensis, new species: 52, Fe- male, metasome segments 5-6 and urosome, dorsal; 53, female, metasome seg- ments 5-6, lateral view; 54, male, leg 5, left exopod, apical segment, posterior view; 55, male, leg 5, posterior view; 56, female, leg 5, with details of exopod setae and apex of endopod; 57, male, right antennule, spines and processes of segments 10-16; 58, male, distal segments of urosome, dorsal. 24 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 exopod I, its setae not longer than half its length, both with enlarged bases and thickly plumose. Leg 5 of male, right: Basipod 1 with a long spinelike sensillum reaching to near the middle of the next segment. The inner proximal portion of basipod 2 with a prominent lobed protrusion accompanied distally by a small narrow hyaline lamella (fig. 48) ; the distal portion of the segment lacking the cuticular process present in many species of Aglaodiaptomus. The first exopod segment about as long as basipod 2, the outer distal portion produced. Proportions of exopod 1 to exo- pod 2, 25:40. Inner portion of exopod 2 deeply grooved, the anterior side with a protruding flange ; relative length of lateral spine to exopod 2, 26: 40. Claw subequal to exopod 2, very stout and curving. Endopod a little less than one-half the length of exopod 1. Left leg: Sensillum of basipod 1 a stout spine. Exopod 1 noticeably longer than exopod 2, 24:16. Exopod 2 broadened distally, the distal process digitiform, nearly one-third the length of the outer margin of the segment ; the inner process a long, curving, setiform spine, nearly 3 times the length of the distal (14:5), spinulose on its inner margin ; the sclerotized marginal area of the segment produced to a point at its base. The proximal pad consisting of a hairy region on the upper inner margin; the distal pad of spinulose areas on the posterior face. The endopod very large, reaching to near the end of exopod 2, the inner portion grooved, the entire surface thickly spinulose from above the middle to the end. Taxonomic position—The subgenus Aglaodiaptomus was proposed by Light in 1938. The original list of included species should be revised as follows: D. piscinae Forbes (1893) should be recognized as a synonym of D. leptopus Forbes (1882). The type collections of Forbes (Illinois Natural History Survey) as well as those of Schacht and Marsh have been examined, and no definable structural difference has been found. (The details of this study are reserved for future publication.) In the synonymy of leptopus should also be placed D. manitobensis Ar- nason (1950). I wish to acknowledge Dr. Arnason’s courtesy in permitting me to examine type material of his proposed species. Diaptomus spatulocrenatus Pearse (1906) was omitted from Light’s list. The species Diaptomus pseudosanguineus Turner (1921), which was omitted by Marsh (1929), should be recognized, although there are certain inadequacies in the description. The species was described from the St. Louis, Mo., area, and on the basis of the description it is not referable to any of the known species of Aglaodiaptomus. The NO, 2 COPEPODS OF THE GENUS DIAPTOMUS—-WILSON 25 female of pseudosanguineus is described as having a pair of long, curved spines on the ventral portion of the genital segment, and the photographic illustrations show a process distad to the genital pro- tuberance in 2 lateral views of what appear to be two separate indi- viduals (Turner, 1921, pl. 1, fig. 3; pl. 2, figs. 1 and 2). Such a process does not occur on the genital segment of any of the species of Aglaodiaptomus, all of which have been examined. The male fifth leg is most comparable to that of spatulocrenatus, resembling it in the proportions of the segments of the left exopod which are subequal, and the endopod which is described as having a crenate inner margin. The right first exopod segment differs from spatulocrenatus in having the distal outer portion produced as in conipedatus and marshianus. No detail can be made out, from the illustration, of the right second basipod segment, adequate knowledge of which is extremely important in the taxonomy of this group. No type material of Turner’s species is known to be in existence. Diaptomus marshianus is distinguished in the female by the peculiar dorsal protuberance of the metasome. There is no evidence in any of the other species of Aglaodiaptomus of such cuticular development. There can be no question, however, of the reference of this female to Aglaodiaptomus and hence to the male described from this collection, because the female shows unmistakable aglaodiaptomid characters in the uncinate setae of the antennule, the presence of three rather than four setae on the distal lobe of the basal segment of the maxilliped, and the dense plumosity of the endopod setae of the fifth leg. The male fifth leg most closely resembles that of spatulocrenatus and conipedatus, from which it can be distinguished by the lack of a distal cuticular process of the right second basipod segment and by the grosser development of the left endopod. It appears to differ from pseudosanguineus in having the first leit exopod segment considerably longer than the second. It is a personal pleasure to give the name of Dr. C. Dwight Marsh to a distinctive American species of Diaptomus. In this connection, attention should be drawn to the fact that Kiefer (1936, p. 309) has shown that the species named D, marshi by Juday (1914) should be known as D. colombiensis Thiebaud. Kiefer has stated that Thiebaud’s paper was actually published as a separate in 1912 instead of 1914. Acknowledgment is due Murray Voth and Dr, Irene Boliek, of Florida State University, for specimens and information of this in- teresting species. 26 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 DIAPTOMUS (MASTIGODIAPTOMUS) TEXENSIS, new species Figures 52-58 Type lot.—200 specimens of both sexes. Temporary roadside pond, county road to Bayside, about 1.5 miles west of Rockport, Aransas County, Tex., “spring” of 1945, Joel W. Hedgpeth collector. Holo- type female, U.S.N.M. No. 94630; allotype male, U.S.N.M. No. 94631. Diagnosis ——Length, dorsal view: Female, 1.5-1.6 mm. Greatest width of female in segment 3, 26-28 percent of length. Distal part of fifth metasomal segment of female usually with a small, medially placed, rounded dorsal protuberance (not always present). Wings not expanded, the left larger than that of the right side, both with spinelike sensilla, that on the inner portion of the left side usually directed outward. Urosome of female 3-segmented. Genital segment symmetrical, without lateral protrusions, lateral sensilla stout. Caudal rami longer than segment 3 (26:20) ; their width about 61 percent of their length; both margins ciliate; the dorsal seta about one-half to three-fourths the length of the inner caudal seta. Urosome of male asymmetrical ; segment 4 produced backward on the right side ; caudal rami asymmetrical, the right longer than the left, with a cuticular process on its ventral side near the base of the inner setae. Antennules of female reaching beyond caudal rami by last two segments. Setation: 2 on segment II, I on segments 13-19; seta of segment I short. Left antennule of male like that of female. Right antennule of male: Spine on segment 8 not enlarged, that of segment 10 hardly larger than that of 8, that of 11 nearly as long as width of its segment, that of 13 not much longer than the width of its segment, but exceedingly stout. Segments 14, 15, and 16 with stout spinous processes. Proportions of spines and processes to one another : 8 10 II 13 14 15 16 3 5 14 20 13 14 5 Segment 23 with a short, outcurved process, reaching about to the middle of segment 24. Maxilliped slender, setation of basal segment normal ; the inner setae of the endopod not clawlike, all shorter than the endopod; the outer and terminal setae longer than the endopod (40: 37). Schmeil’s organ present on endopod of leg 2. Leg 5 of female stout, width of exopod 1 about half its length. Sensillum of basipod 1 a long, stout, flat spine. Exopod 1 a little longer than exopod 2 (27: 25). Exopod 3 separated, its outer seta short and spinelike, closely set with and usually overlying the inner seta; NO. 2 COPEPODS OF THE GENUS DIAPTOMUS—WILSON 27 lateral seta of exopod 2 present, shorter than exopod 3. Claw with spinules on both margins. Endopod nearly as long as inner margin of exopod 1, 2-segmented, bearing 2 setae, the outer longer than the inner, which is set considerably above the tip of the endopod; tip of endopod with double row of stout hairs. Leg 5 of male, right: Sensillum of basipod 1 a stout spine, in pos- terior view overlying the second basipod segment and directed toward a protrusion of the segment whose central portion consists of a cres- cent-shaped sclerotized lamella. The inner proximal portion with an inwardly and sometimes distally directed small marginal lamella. Exo- pod 1 with small lamellae on both inner and outer distal portions. Exopod 2 bulging medially, with a crescent-shaped sclerotization on the midposterior face; the lateral spine distally placed, stout and straight, its length less than that of the segment. Claw strongly curved at middle, as long as the rest of the leg. Left leg: Sensillum of basipod 1 stout as on the right side. Inner part of basipod 2 produced proximally. Exopod 1 more than three times longer than exopod 2 (50:15). The distal process short and broad, its margins strongly serrate ; the inner process spiniform, reach- ing to the end of the distal. Pads medial in position, the proximal the larger. Taxonomic position.—This new species is allied to the southwestern species D. albuquerquensis Herrick, the known distribution of which extends through the Rocky Mountain States from Utah to Guatemala in Central America. The only other species of the subgenus on the continent, D. amatitlanensis M.S. Wilson (1941), is also known from Guatemala. There are no authentic records of the group from south- eastern United States. Florida specimens identified by Schacht (1897) as D. albuquerquensis are undoubtedly referable to D. floridanus Marsh (1926). Such is also true of the specimens from Georgia listed by Humes (1950). Specimens to which Humes referred have been sent to me by Dr. M. S. Ferguson, of the United States Public Health Service, and have been found to be D. floridanus. Diaptomus saltillinus Brewer, which is closely allied to D. floridanus, is found in Texas and some other areas where the albuquerquensis group occurs. D. saltillinus and D. floridanus belong to the subgenus Arctodiaptomus Kiefer (1932) and the albuquerquensis group to the subgenus Mastigodiaptomus Light (1939). There are superficial re- semblances between these two groups of species, but they should not be confused with each other if careful attention is given to basic sub- generic characters such as are found in the left exopod of the male fifth leg, the armature of the endopod of the female fifth leg, and the 28 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 presence in Mastigodiaptomus of 2 setae on segment 11 of the female and left male antennules, as contrasted to the single seta of this seg- ment in saltillinus and floridanus. D. texensis is distinguished from albuquerquensis by several easily recognized differences in the male right fifth leg. In albuquerquensis the lateral spine of exopod 2 is longer than the segment, the second basipod segment has the inner proximal portion bulging upward as does also the marginal lamella, and the distal posterior face has a characteristic sculpturing of the cuticle that is lacking in tevxensis. The females are very similar but can be separated by the lateral pro- trusions of the genital segment and the usual shortness of the endopod of the fifth leg of albuquerquensis. ACKNOWLEDGMENTS The extensive collections of Diaptomus that have been gathered together by the American specialists Dr. C. D. Marsh and Dr. S. F. Light are in the U. S. National Museum. Their use has made much of this work possible. For the organization and selection of materials from these collections, I am greatly indebted to Dr. Fenner A. Chace, Je, and’ Dr--Paul': Tile. The type lots of Diaptomus shoshone, Diaptomus leptopus, and piscinae were lent by the Illinois Natural History Survey, through Dr. Herbert Ross and Philip W. Smith. The type of Diaptomus mamni- tobensis was kindly referred to me by Dr. I. G. Arnason. Collections upon which other published records were based were lent by Dr. Frank F. Hooper and Dr. M. S. Ferguson. Grateful acknowledgment is also made to the following persons who have referred new collections to me or supplied information concerning them: Charles S. Wilson, Murray H. Voth, Dr. Irene Boliek, Dr. Joel W. Hedgpeth, Dr. Charles C. Davis, Dr. Walter G. Moore, and Dr. L. B. Holthuis. LITERATURE CITED ArRNASON, I. GILBERT. 1950. A new species of diaptomid copepod from Manitoba. Journ. Elisha Mitchell Sci. Soc., vol. 66, pp. 148-155, 23 figs. Cart, G. CLIFFORD. 1940. The distribution of some Cladocera and free-living Copepoda in British Columbia. Ecol. Monogr., vol. 10, pp. 55-110, 14 figs. 1944. The natural history of the Forbidden Plateau area, Vancouver Island, British Columbia. Rep. Prov. Mus. for 1943, pp. D 18-40, 2 ills., I map. Dopps, GinEon S. 1915a. Descriptions of two new species of Entomostraca from Colorado, with notes on other species. Proc. U. S. Nat. Mus., vol. 49, pp. 97-102, 10 figs. NO. 2 COPEPODS OF THE GENUS DIAPTOMUS—WILSON 29 1915b. A key to the Entomostraca of Colorado. Univ. Colorado Stud., vol. II, pp. 265-208, 82 figs. 1917. Altitudinal distribution of Entomostraca in Colorado. Proc. U. S. Nat. Mus., vol. 54, pp. 59-87, Io figs., 2 pls. 1924. Notes on Entomostraca from Colorado. The Shantz collections from the Pikes Peak region. Proc. U. S. Nat. Mus., vol. 65, art. 18, pp. 1-7, I fig. Forses, S. A. 1882. On some Entomostraca of Lake Michigan and adjacent waters. Amer. Nat., vol. 16, pp. 537-542, 640-649, 2 pls. 1893. A preliminary report on the aquatic invertebrate fauna of the Yellow- stone National Park, Wyoming, and of the Flathead region of Montana. Bull. U. S. Fish Comm. for 1891, pp. 207-258, 6 pls. GuRNEY, RoseErrT. 1931. British fresh-water Copepoda. Vol. 1, 238 pp., 344 figs. Ray Society, London. Hooper, FranxK F. 1947. Plankton collections from the Yukon and MacKenzie River systems. Trans. Amer. Micr. Soc., vol. 66, pp. 74-84, 1 fig. Humes, ArTHUR G. 1950. Experimental copepod hosts of the broad tapeworm of man, Diboth- riocephalus latus (L.) Journ. Parasitol., vol. 36, pp. 541-547. JupAy, CHANCEY. 1914. A new species of Diaptomus. Trans. Wisconsin Acad. Sci. Arts and Lett., vol. 17, pp. 803-805, 2 figs. Jupay, CHANcEy, and MutrxKowskI, R. A. 1915. Entomostraca from St. Paul Island, Alaska. Bull. Wisconsin Nat. Hist. Soc., vol. 13, pp. 23-31, 6 figs. KIEFER, FRIEDRICH. 1932. Versuch eines Systems der Diaptomiden (Copepoda, Calanoida). Zool. Jahrb. (Abt. Syst.), vol. 63, pp. 451-520, 88 figs. 1936. Freilebende Stiss- und Salzwassercopepoden von der Insel Haiti. Arch. Hydrobiol., vol. 30, pp. 263-317, 126 figs., I map. ibiveiet, Sp ae 1938. New subgenera and species of diaptomid copepods from the inland waters of California and Nevada. Univ. California Publ. Zool., vol. 43, pp. 67-78, 23 figs. 1939. New American subgenera of Diaptomus Westwood (Copepoda, Calanoida). Trans. Amer. Micr. Soc., vol. 58, pp. 473-484, 24 figs. Marsu, CHARLES DWIGHT. 1907. A revision of the North American species of Diaptomus. Trans. Wisconsin Acad. Sci. Arts and Lett., vol. 15, pp. 381-516, 14 pls. 1915. A new crustacean, Diaptomus virginiensis, and a description of Diaptomus tyrelli Poppe. Proc. U. S. Nat. Mus., vol. 49, pp. 457- 462, 7 figs. 1920. The fresh water Copepoda of the Canadian Arctic Expedition 1913- 18. Rep. Canadian Arctic Exped. 1913-18, vol. 7, pt. J, pp. 1J-25J, 5 pls. 1924. A new locality for a species of Diaptomus. Science, vol. 59, pp. 485- 486. 30 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 1926. On a collection of Copepoda from Florida, with a description of Diaptomus floridanus, new species. Proc. U. S. Nat. Mus., vol. 70, art. 10, pp. I-4, 6 figs. 1929. Distribution and key of the North American copepods of the genus - Diaptomus, with the description of a new species. Proc. U. S. Nat. Mus., vol. 75, art. 14, pp. 1-27, 16 figs. Pearse, A. S. 1905. Contributions to the copepod fauna of Nebraska and other States. Stud. Zool. Lab. Univ. Nebraska, No. 65, pp. 145-160, 5 pls. 1906. Fresh-water Copepoda of Massachusetts. Amer. Nat., vol. 40, pp. 241-251, 9 figs. Sars, Georc OssIAn. 1898. The Cladocera, Copepoda and Ostracoda of the Jana Expedition. Ann. Mus. Zool. Acad. Imp. Sci. St. Pétersbourg, vol. 3, pp. 324- 359, 4 pls. 1903. On the crustacean fauna of Central Asia. Pt. III. Copepoda and Ostracoda. Ann. Mus. Zool. Acad. Imp. Sci. St. Pétersbourg, vol. 8, pp. 195-232, 8 pls. ScHACHT, FREDERICK WILLIAM. 1897. The North American species of Diaptomus. Bull. Illinois State Lab. Nat. Hist., vol. 5, pp. 97-208, 15 pls. ScHMEIL, OrrTo. 1896. Deutschlands freilebende Siisswasser-Copepoden. Pt. 3. Centro- pagidae. Bibl. Zool., vol. 21, pp. 1-144, 12 pls. THACKER, Mr. and Mrs, T. L. 1923. Some freshwater crustaceans from British Columbia. Can. Field-Nat., vol. 37, pp. 88-80. THIEBAUD, M. 1912. Voyage d’exploration scientifique en Colombie. Copépodes de Co- lombie et des Cordilléres de Mendoza. Mém. Soc. Neuchateloise Sci. Nat., vol. 5, pp. 160-175, 25 figs. TurRNER, C. H. 1921. Ecological studies of the Entomostraca of the St. Louis district. Pt. 1. Diaptomus pseudosanguineus sp. nov. and a preliminary list of the Copepoda and Cladocera of the St. Louis district. Trans. Acad. Sci. St. Louis, vol. 24, No. 2, pp. 1-25, 4 pls. Wirson, Mitprep STRATTON. 1941. New species and distribution records of diaptomid copepods from the Marsh collection in the United States National Museum. Journ. Washington Acad. Sci., vol. 31, pp. 509-515, I fig. SMITHSONIAN MISCELLANEOUS COLLECTIONS VOLUME 122, NUMBER 3 fae METAMORPHOSIS OF A FLY Ss. HEAD BY R. E. SNODGRASS Collaborator, Bureau of Entomology and Plant Quarantine, U. S. Department of Agriculture (PusiicaTion 4133) CITY OF WASHINGTON PUBLISHED BY THE SMITHSONIAN INSTITUTION JUNE 25, 1953 The Lord Baltimore Press BALTIMORE, MD., U. 3. A. fib METAMORPHOSIS"OF Ay BLY’S HEAD By R. E. SNODGRASS Collaborator, Bureau of Entomology and Plant Quarantine U. S. Department of Agriculture A legless, almost headless, wormlike maggot hatches from the egg of a fly; but the maggot is not a young fly in the sense that a kitten is a young cat, or even in the sense that the nymph of a grasshopper is a young grasshopper. The maggot does not grow up into a fly, and neither does it literally transform into a fly. It is a highly special- ized larval form of its species, which, though developed directly from the fly’s egg, becomes a creature self-sufficient in all respects except that of procreation. Structurally the fly larva is so different from its parents that it cannot itself go over into the next fly generation. Consequently nearly all the larval tissues finally go into a state of dis- solution, and the fly is then newly generated from groups of undif- ferentiated cells that are carried by the larva but which form no essential part of the larval organization. This potentiality of dual development from a single egg becomes most accentuated among the Diptera in the cyclorrhaphous families. It affects not only the internal organs, but also the body wall, which is almost entirely replaced during the pupal stage from groups of cells, known as imaginal discs, that remain undeveloped from an early period, and at the end of the larval life begin an active growth that forms the integument and appendages of the pupa. The cells of the larval integument degenerate before the advancing new epidermis and are cast into the body cavity where they become food for the develop- ing imaginal tissues. During larval life the regenerative discs of the thorax and head are contained in narrow-necked pouches of the epi- dermis, closed at their outer ends beneath the cuticle. Within these pouches the appendage rudiments may develop continuously through the larval instars without being exposed at the larval moults. Finally, however, during the prepupal or early pupal stage the pouches are everted and the appendages quickly grow to the state of development they have when the pupa is exposed by the shedding of the last larval cuticle, while the everted pouches themselves expand by cell prolifera- tion and construct the pupal integument. SMITHSONIAN MISCELLANEOUS COLLECTIONS, VOL. 122, NO. 3 2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 All this has been known for nearly a century. Weismann (1864) said that the thorax and head of the fly, together with their append- ages, the halteres, the wings, legs, antennae, eyes, and mouth parts de- velop within the body of the larva, and the truth of this statement has been verified by numerous subsequent workers. Most of the earlier students of the structure and metamorphosis of the cyclorrhaphous larva, however, did not understand the morphology of the larval head. Though they correctly described facts, their identification of anatomi- cal parts is often entirely erroneous, and later writers, taking their statements literally, either criticize them as false, or perpetuate their errors. In the following pages an attempt will be made first to under- stand the nature of the head of a cyclorrhaphous larva, and then to put together the story of the formation of the adult head as far as it can be compiled from our present information on the subject. In the lower nematocerous flies the metamorphic changes between larva and adult are less intense than in the cyclorrhaphous families, and larval tissues may go over directly into adult tissues. In the larva of Corethra, for example, as described by Weismann (1866), the imaginal discs of the thorax are mere groups of cells in the larval epidermis, which begin development in the prepupal period and then form only the pupal appendages. The general integument of the pupal thorax in this case is a product of renewed growth activity in the cells of the larval epidermis, which simply remodel the thorax into the form of the pupal thorax. The same applies to changes of the head, the pupal head being formed by alterations in shape and size of the larval head within the unshed cuticle of the last larval instar. The imaginal mouth parts of Nematocera have been shown by Kellogg (1902) to be formed directly within the larval mouth parts; the adult antennae, however, which are generally much longer than the larval organs, de- velop with only their distal ends in the larval antennae. In some of the lower flies, as will be shown later, the imaginal antennae grow within pockets of the integument, and the pockets may include also the rudiments of the compound eyes. The structural disparity between the larva and the adult in the Cyclorrhapha is due to the specialized form that the larva has acquired, rather than to that of the adult fly. The larval head of these flies in particular has become so highly modified in a specific way that it is difficult to understand how it has been evolved from a head of more usual structure. Only a small part of the adult head is derived directly from the larval head. The apparent, or functional, head of a muscoid maggot is a small, rounded lobe at the anterior end of the body (fig. 2 A, LH) more or less sunken into the thorax. Apically this larval head bears a pair of NO. 3 METAMORPHOSIS OF A FLY’S HEAD—SNODGRASS 3 large papillae, on each of which are situated two small sense organs, but there are no eyes of any kind. The under surface of the head (A) presents a median depression from which projects a pair of strongly ii re cy CATIT ALAN Fits 7 CL ARAN MAN | 4 meg Wu qt un vi ANS a a: WN “|B? i A a ‘J cae S| woe re Ai ees x f B Fic. 1.—Head and proboscis of adult muscoid flies. A, Musca domestica L., anterior. B, Calliphora vicina R.-D. (erythrocephala Meigen), clypeus and proboscis. C, Callitroga macellaria (F.), ventral. D, Gonia sp., with ptilinum everted. sclerotized, decurved hooks (mh) partly covered by lateral folds of the integument. Below the bases of the hooks is a soft median lobe (Lb), which at least serves the larva as an under lip, and appears to be a true larval labium. Above the labium, between the bases of the 4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 hooks, is the food-intake orifice of the larva (Atr), but it leads im- mediately into an atrial chamber before the mouth of the larval sucking apparatus. The larval organ of ingestion is a suction pump lying within the thorax, supported by a strongly sclerotized structure commonly called by students of cyclorrhaphous larvae the “buccopharyngeal skeleton” or the “cephalopharyngeal apparatus” (fig. 2B). By whatever name this complex structure is known, it is an important part of the larval head retracted into the thorax. In details of shape it differs character- istically in different species, but the general form and structure of the organ is that shown here for the mature larva of Callitroga macellaria. The dorsal part of the sucking apparatus (fig. 2 F) is a long, thin, hyaline plate having a strongly contrasting, dark U-shaped sclerotiza- tion around its anterior end with the arms extending posteriorly along the lateral margins. From the edges of this sclerotized part of the dorsal plate a strong lateral plate descends on each side (B) and ex- pands below into a broad posterior extension. Supported between the lower edges of the lateral plates is the sucking pump of the larva (CbP), which is continuous anteriorly from the atrium above the labium (Lb) and posteriorly into the oesophagus (Oc). The lumen of the pump when contracted is crescent-shaped in cross section (D, Cb), but on its concave upper wall are attached two rows of large dilator muscles (dlcb) arising on the arms (Clp) of the U-shaped sclerotization of the dorsal plate. Anterior to the lateral plates is a smaller, independent, median, ventral plate (B, e) on which the mouth hooks (mh) are articulated. This plate, which lies on the base of the dorsal wall of the larval labium (C, e), is H-shaped in ventral view (E, e). In front of its crossbar are two small sclerites bearing minute sense organs, and a narrow anterior V-shaped sclerite. Just behind the crossbar is the opening of the salivary duct (B, E, SIDct), which discharges on the base of the labium. The dorsal plate of the larval sucking apparatus is covered by a very delicate, closely adherent membrane (fig. 2B, a). Anteriorly, how- ever, the membrane becomes free, forming the dorsal wall of the atrium (Atr), and is then continued into the wall of the ventral de- pression of the external larval head (A). When the atrium is exposed by cutting away the covering membrane (C) there is seen projecting into it from the anterior end of the dorsal plate of the sucking appa- ratus a small conical lobe (Lm) with a minute sclerotic tip. This lobe is clearly the larval labrum ; in a first instar larva the sclerotized tip is larger and forms a conspicuous tooth. The “buccopharyngeal skeleton” of the cyclorrhaphous larva is NO. 3 METAMORPHOSIS OF A FLY’S HEAD—SNODGRASS 5 perhaps generally regarded as a structure distinctive of the larva, since most entomologists do not seem to have observed that it is almost a replica of the supporting skeleton of the sucking pump of the adult fly, which is commonly known as the “fulcrum” of the proboscis. This structure in the fly (fig. 3 F) consists of the clypeus (C/p) and a pair of lateral plates (f), called the paraclypeal phragmata, inflected ay » i > LS ea S SS = se = <> Fic. 2—Larval head structures of Callitroga macellaria (F.). A, head lobe of larva (LH), partly retracted into prothorax, ventral. B, feed- ing apparatus (“buccopharyngeal skeleton”) of a mature larva, lateral. C, dia- gram of anterior end of sucking apparatus, with lateral wall of atrium (Air) cut away, exposing the labrum (Lm). D, cross section of sucking apparatus, showing inflection of paraclypeal phragmata (f,f) from edges of clypeus, sup- porting the cibarial pump (Cb). , ventral surface of anterior part of cibarial pump and H-shaped sclerite (e) supporting the mouth hooks (mh) and the labium (Lb). F, frontoclypeal plate of sucking apparatus, dorsal. G, diagram- matic lengthwise section of head and prothorax, mesal view of right half. from the clypeal margins, which support between their lower edges the sucking pump (COP) of the food tract. The dilator muscles of the pump (G, dicb) arise on the clypeus and are enclosed between the paraclypeal phragmata. The cross section of the “fulcrum” of the fly (E), therefore, is an exact duplicate of a similar section of the “buc- copharyngeal” apparatus of the larva (fig. 2 D), and there can scarcely 6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 be any question that the two structures are merely imaginal and larval forms of the same thing. The clypeus of a muscoid fly is generally U-shaped or V-shaped with the closed end dorsal. In Musca and Calliphora (fig. 1 A, B) the clypeus (C/p) is fully exposed on the base of the proboscis; in Callitroga (C) it is deeply sunken in a cavity on the under side of the head; in Gonia (D) it is relatively very small. In Musca (A) the broad base of the clypeus is closely hinged to the lower margin of the frons (Fr) ; in Calliphora (B) a hinge plate (hpl) intervenes between the frons and the muscle-bearing plate of the clypeus; in Callitroga (C) the sunken clypeus is separated by membrane from the epistomal ridge beneath the frons; in Gonia (D) the diminutive clypeus is well removed from the frons. In any case, the proboscis, with the clypeus and the sucking apparatus, swings back and forth below the frons in the ample membranous connection of the clypeus with the head by muscles attached on the supporting skeleton of the sucking pump. The latter and the clypeus are, therefore, known as the “fulcrum” of the proboscis. Finally, to understand the nature of the parts that compose the “ful- crum” of the adult muscoid fly, we must go back to the more primitive condition in the orthopteroid insects. A median section through the distal part of the head of a cockroach (fig. 3 A) shows that there is a specific preoral food pocket, the cibariwm (Cb), between the epipha- ryngeal wall of the clypeus (C7p) and the sloping basal part of the hypopharynx (Hphy). Two suspensory rods on the cibarial floor ex- tend up through the angles of the mouth (4) and give attachment to muscles from the frons. On the anterior or upper wall of the cibarium are attached thick bundles of muscle fibers (dlcb) arising on the ex- ternal clypeal area of the head. These muscles are compressors of the clypeus, but their contraction expands the cibarium. If, then, the mov- able lobe of the hypopharynx is brought against the inner surface of the labrum (Lm), the cibarium will become practically a closed cham- ber opening anteriorly from the food meatus (fm) between the labrum and the free lobe of the hypopharynx, and proximally into the stomo- daeum (Stom). It is very probable that the cibarium thus serves the cockroach as an organ for the ingestion of liquids. On its dorsal wall are transverse compressor muscles not shown in the figure. The true mouth of the cockroach is the opening of the cibarium (Mzth’) into the stomodaeum. An important point to bear in mind is that the cibarial muscles of the clypeus are separated from muscles of the stomodaeum arising on the frons by the frontal ganglion and its brain connectives, NO. 3 METAMORPHOSIS OF A FLY’S HEAD—SNODGRASS 7 The homology of the sucking pump of the fly with the cibarium of the cockroach has been amply illustrated by Gouin (1949). In various insects the cibarium becomes a permanently more or less closed chamber by a lateral union of the epipharyngeal wall with the base of the hypopharynx, so that the functional mouth opening may come to lie beneath the base of the labrum. The cibarium thus becomes more efficient as a sucking organ. Among the Diptera this condition is fully developed in the lower families, and is well illustrated in the mos- quito (fig. 3B). The cibarial pump of the mosquito (CbP) has a strongly sclerotized basinlike floor ; the intake orifice lies beneath the base of the labrum and thus constitutes a secondary mouth (Mth’). Since the floor of the pump in the mosquito corresponds with the hypo- pharyngeal floor of the cibarium in the cockroach, the hypopharyngeal stylet of the mosquito (B, Hphy) represents only the free lingual lobe of the cockroach hypopharynx (A, Hphy). A section of the sucking pump of the mosquito (indicated by the arrow at B) shows two sets of strong dilator muscles (dlcb) from the clypeus to the concave upper wall of the pump. The cibarial pump of the mosquito projects freely into the head (fig. 3 B), and, though it is strongly sclerotized and is suspended from the frons by muscles attached on a pair of proximal processes (4), it is still not braced against the pull of the dilator muscles. This condition has been remedied in the higher flies. In some of them, as in the mydas fly (C), a strong ridge is inflected from a groove on each side of the clypeus, and the distal ends of the ridges (f) are fused with the lateral walls of the pump, thus serving to hold the latter firmly in place. From this simple condition it is only a step to that in the mus- coid flies in which the clypeal ridges have been enlarged into broad paraclypeal phragmata (F, f) supporting the full length of the pump. The dilator muscles of the pump (FE, dich) are thus boxed in between lateral plates (f, f), and the pump is securely braced against the clyp- eus. As in the cockroach and the mosquito, the primary mouth of the muscoid fly is the opening of the cibarium into the stomodaeal oesopha- gus (F, Mth’), but the functional mouth (Mth”) is the entrance into the cibarium from the food meatus (fm) between the labrum and the hypopharyngeal stylet. However, in those flies in which the labellar lobes of the labium form a broad, food-collecting disc (D), the deep notch between the lobes (Mth’’) is the real intake aperture for liquid food, and has been termed the prestomum. The paraclypeal phragmata are not primarily inflections from the extreme edges of the clypeus. In the adult male of Tabanus, as has been shown also by Bonhag (1951), the clypeus is divided longitudi- 8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 nally into three areas by a groove on each side well within the epistomal sulcus. These clypeal grooves in Tabanus form merely a pair of inter- nal ridges, but it is clear that the ridges represent the beginning of paraclypeal phragmata in other flies. Developmentally the phragmata are first formed in the larva, and they may be well developed in bra- chycerous as well as in cyclorrhaphous larvae. Theoretically, however, it seems probable that the complex sucking apparatus must have been first evolved in the adult fly, since the larvae of lower dipterous fam- ilies have biting and chewing mouth parts. On returning now to the larva, it is clear that the sucking pump (fig. 2B, CbP) is the cibarium, as it is in the fly. The dilator muscles of the larval cibarium lying in front of the frontal ganglion, therefore, should identify the part of the dorsal plate on which they take their origin as the clypeus (C/p), since these muscles entirely conform with the cibarial muscles of the adult. In the larva, however, there is an oblique posterior group of fibers just behind the frontal ganglion, at- tached below on the stomodaeal oesophagus (G) and arising on the posterior part of the dorsal plate of the sucking apparatus mesad of the cibarial muscles. In the cyclorrhaphous flies the stomodaeum proceeds from the cibarial pump as a simple tubular oesophagus (figs. 2 B, 3 F, Oe), but in adult Brachycera it is differentiated immediately behind the cibarium into a second, smaller pharyngeal pump, with its dilator muscles arising on the frons, and these muscles are those represented in the cyclorrhaphous larva by the oesophageal muscles arising on the posterior part of the dorsal plate of the sucking apparatus. The struc- ture and mechanism of the pharyngeal pump in the adult of Tabanus are well described and illustrated by Bonhag (1951). In the larvae of Stratiomydiae the pharyngeal pump has been con- verted into a crushing organ by the transformation of its dorsal wall into a thick plate with a convex, sometimes strongly ridged, under sur- face that fits like a broad pestle into the concave, mortarlike ventral wall. This pharyngeal organ is sclerotically continuous with the long, slender cibarial pump, from the end of which it turns upward like the bowl of a pipe from the stem (fig. 6 B, Phy). It is the Schlundkopf of Jusbaschjanz (1910), who calls the cibarium the “pharynx” ; it is described in the larva of Odontomyia alticola by Cook (1949), and Schremmer (1951) gives a fully detailed account of its structure and probable use in the larva of Stratiomys chamaeleon. The organ is operated by dorsal muscles arising on the frontoclypeal area of the head. A large anterior muscle inserted at the junction with the cibar- ium is shown by Cook to lie before the frontal ganglion and its brain connectives. This muscle, therefore, is a cibarial muscle; the other, posterior muscles are true frontal pharyngeal muscles. NO. 3 METAMORPHOSIS OF A FLY’S HEAD—SNODGRASS 9 The attachment of both frontal muscles and clypeal muscles on the dorsal plate of the larval sucking apparatus should identify this plate as a frontoclypeal element of the head skeleton, which is a well-defined, Fic. 3.—The sucking apparatus of adult Diptera, and comparison with the cibarium of a cockroach. A, diagrammatic lengthwise section of head of a cockroach. B, diagram of sucking apparatus of a mosquito. C, same of a mydas fly. D, labellar disc of a muscoid fly. FE, cross section of sucking apparatus of adult Callitroga macellaria. F, sucking apparatus and mouth parts of adult Callitroga macellaria, lateral. G, lengthwise section of sucking apparatus of same, showing clypeal dilator muscles of cibarium. median dorsal area of the head in most nematocerous and brachycer- ous fly larvae (fig. 6 A). Cook (1949) has called this entire area the “clypeus,” but in so doing he disregards the evidence from muscle attachments in insects having the clypeus separated from the frons, in IO SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I22 which the cibarial muscles arise on the clypeus and the postcibarial muscles on the frons. The frontal and clypeal areas, however, are often continuous. Ludwig (1949) says merely that this area of the head in the larva of Calliphora “includes the clypeus and some addi- tional part of the cranium.” The sucking apparatus of the cyclorrha- phous larva, therefore, is a more complex structure than that of the adult fly in so far as it includes not only the clypeus and the cibarium, but also the frons and frontal muscles of the stomodaeum. The fron- toclypeal plate and the sucking apparatus of the larva lie entirely within the thorax, a position they have acquired either by retraction or by the overgrowth of a fold from the thorax, or by both means. The frontoclypeal plate is connected with the external larval head (fig. 4 D, LH) by the membrane (a) extending back from the latter over the atrium. The H-shaped plate of the larva that lies on the base of the labium and supports the mouth hooks (fig. 2 B, E, e) suggests by its position the hyoid sclerite of the adult (fig. 3 F, hy), but in the larva the sali- vary duct (SIDct) opens behind the H-shaped plate, while in the adult it enters the hypopharyngeal stylet anterior to the hyoid. The hypo- pharynx in the larva is represented only by the floor of the cibarium, a free hypopharyngeal lobe corresponding with that of the cockroach (fig. 3 A) or with the hypopharyngeal stylet of the fly (F, Hphy), being absent in the larva. The larval labium (fig. 2 A, C, Lb) does not become the labium of the adult ; the labium of the fly is developed from a pair of histoblastic pouches formed inside the larval labium. The nature of the mouth hooks of the cyclorrhaphous larva has been a subject of much discussion, some writers contending that the hooks are mandibles, others that they are not. The latest advocate of their mandibular nature is Ludwig (1949). If the larval mouth hooks are not mandibles, the question is, what are they? In the first place, it is curious that mandibles should have their only articulations on a plate on the base of the labium, and secondly, since the muscles of the hooks are attached on the paraclypeal phragmata of the sucking apparatus, it is an unusual thing for mandibular muscles to arise on any part of the clypeus. However, since the parietal walls of a typical insect cra- nium are obliterated in the fly larva, the phragmata offer the only available solid support for the muscles, and muscles do change their points of origin where efficiency demands a change. On the other hand, if the hooks are not mandibles, they cannot be homologized with any other structure of other insects, and it is hardly to be supposed that such highly developed feeding organs should be developed de novo for the express use of the larva. However, since the hooks disappear at NO. 3 METAMORPHOSIS OF A FLY’S HEAD—SNODGRASS II the end of larval life and the adult fly has no mandibles, the larval hooks cannot be put to the crucial test of finding what they become in the imago, and for this same reason we may leave the matter without further discussion, inasmuch as the mouth hooks are not involved in the metamorphosis of the larva into the fly. In most nematocerous and brachycerous families the head of the larva is more or less retracted into the thorax, so that it is at least partly ensheathed in a fold of the prothorax. In the cyclorrhaphous larva, however, the head appears to consist of an external part bearing the apical sense organs of the larva, and of a retracted part that in- cludes only the frontoclypeal area, which carries the labrum and supports the cibarial sucking apparatus. The cyclorrhaphous larva thus presents a cephalic condition that is difficult to understand, and even the known facts of embryonic development do not make the condition entirely clear. The head of the embryo at an early stage of its development is a simple structure. As shown by Pratt (1901) in Melophagus ovinus (fig. 4 A) the embryonic head presents a dorsal lobe above the entrance into the food tract (Cb) and a ventral lobe below it. The dorsal lobe, which contains a group of compressor muscles (dich), Pratt calls the “muscular sucking tongue,” but we can easily recognize this lobe as the labrum and clypeus (Lm, Clip), and the muscles as the dilators of the future cibarial pump (Cb). The ventral lobe is clearly the larval la- bium. This stage of the embryo may be diagrammatically presented in a more conventional form as at C of the figure. The short dorsal wall of the embryonic head represents at least the clypeus of the larva (D, Clp) bearing the labrum and giving attachment to the dilator muscles of the cibarium. The primary embryonic head now becomes covered by the forward growth of an integumental fold (fig. 4 A, C, hf) from behind it, which goes over the labrum (B) and forms the roof of an antechamber, the head atrium (Atr), before the mouth of the cibarium (Cb), while the fold itself becomes at least a part of the external head lobe of the larva (D, LH) bearing the larval sense organs. The overgrowth of the primitive head by this secondary dorsal head fold is well illustrated also in Calliphora by Ludwig (1949, fig. 58). According to Pratt (1901) there is a dorsal and a ventral fold in Melophagus (A, B, C, hf, vf). Unfortunately Pratt’s terminology is confusing because he calls the newly formed atrium the “pharynx,” and the cibarium the “stomodaeum.” With the completion of the dorsal head fold the em- bryo acquires the essential head structure of the larva, represented diagrammatically at D of the figure. The frontoclypeal plate and the I2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 cibarial apparatus thus become enclosed within the thorax, and the major part of the external larval head lobe (LH) bearing the larval sense organs appears to be a secondary structure formed by the dorsal head fold extended from c to d. The original space (b) beneath the fold later becomes obliterated by the close apposition of the inner wall of the fold (a) on the frontoclypeal plate, but the labrum (Lm) is left projecting freely into the atrium (Afr). Of the two sense organs on each of the apical papillae of the larva, the dorsal one, according to Ludwig (1949), represents the larval antenna, the ventral one the maxillary palpus. This opinion was also that of Weismann (1864), but other authors have considered the inter- pretation doubtful. The alleged antennal organ is shown by Ludwig to be innervated by a long branch from the labrofrontal nerve—a most unusual association for an antennal nerve, and neither the nerve nor the sense organ can have any relation to the antenna of the adult. The ventral sense organ, Ludwig says, “is the maxillary palp sense organ,” but apparently the only basis for this statement is that the organ in question is innervated by a branch from the “mandibular-maxillary- labial nerve.” A sense organ wherever located must have a nerve. The origin of the papillar sense-organ nerves from head ganglia is not proof that the organs are either antennal or maxillary, but it is con- vincing evidence that, whatever they are, they belong to the head, and Ludwig shows, moreover, that the organs originate in the epidermis of the lateral walls of the embryonic head. It becomes a problem, therefore, to understand how these sense organs in the larva come to be situated on the external head lobe formed by the head fold, and their position on this lobe raises the question as to whether the fold pertains to the thorax or to the head. As seen in longitudinal sections the head fold of the cyclorrhaphous embryo (fig. 4 A, B, Af) suggests the prothoracic fold that partly en- sheaths the head of many nematocerous and brachycerous larvae (fig. 6 A, B, thf). Schremmer (1951) asserts that there appears to be no remnant of a head in the cyclorrhaphous larva, and that as a result of the forward growth of the dorsal fold the larval sense organs come to be on the anterior end of the thorax. Holmgren (1904) apparently regarded the larval head lobe as a derivative of the thorax, but he says nothing of the sense organs. Pantel (1898) called the larval head lobe a “pseudocephalon.” Ludwig (1949) also attributes at least a part of the head fold to the thorax because it contains a pair of muscles in- nervated from the prothoracic ganglion that “insert on a sclerotized area between the mandibles.” In the Callitroga larva, however, these muscles do not arise in the head lobe itself but on the overhanging NO. 3 METAMORPHOSIS OF A FLY’S HEAD—SNODGRASS 13 anterior part of the prothorax, so, if the larval head lobe is a part of the head, the muscles in question are merely prothoracic head muscles. In a cross section of the embryonic head of Calliphora it is shown by Ludwig that the head fold (fig. 6 C, hf) covers only a narrow space (b) above the frontoclypeal surface (C/p). The inner lamella of the fold (a) arches immediately over the frontoclypeus, while the outer lamella has become continuous with the parietal walls of the head. If IW erry case seSC ea ARVRuaa rumen Mth O S Cb e gIDet hace Fic. 4.—Development of the larval head of a cyclorrhaphous fly. A, lengthwise section of embryonic head of Melophagus ovinus (from Pratt, 1901), showing beginning of head fold (hf). B, later stage of same (from Pratt, 1901), in which the head fold has grown forward over the labrum and labium, which are now enclosed in a secondary preoral atrial chamber (Air). C, dia- grammatic expression of A. D, diagrammatic analysis of the anterior larval structure based on B. the fold proceeds over the head as a narrow median growth from the thorax alone, it is difficult to understand how it becomes so intimately a part of the head wall. In any case, it is evident that this head fold of the cyclorrhaphous larva is something quite different from the pro- thoracic fold that ensheaths the base of the head in a brachycerous larva. The head fold of Calliphora, Ludwig (1949) says, appears at about the thirteenth hour of the developing embryo, and “‘is in the shape of a 14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 U, with the open end pointed anteriorly.” Its lateral margins lie mesad of the developing larval sense organs. If, therefore, the head fold grows forward in this manner with its arms extending along the edges of the frontoclypeal area, it would seem that, whatever its origin, the extension of the fold must be at the expense of the head wall itself, and that the arms of the fold close medially from the sides as the fold advances. If this is the manner of growth of the fold, the condition seen in cross sections of the embryonic head (fig. 6 C) becomes under- standable. Furthermore, only by some such process of growth from the head wall could the lateral sense organs on the embryonic head be carried up over the labrum and finally come to be situated on the an- terior end of the fold, which forms at least the dorsal part of the head lobe of the larva. It is, then, certainly more rational to regard the larval head lobe as a part of the head itself than as a derivative of the thorax. Clearly there is need for further study of the nature of the head fold and the manner of its growth, and Schremmer (1951, p. 362) has promised a new investigation “tuber die Enstehung des Cyclorrhaphenlarvenkopfes.” When a young insect in its development takes a path widely diver- gent from that of its parents, and acquires a head structure as extra- ordinarily specialized as that of the cyclorrhaphous larva, it is evident that the larval structure cannot be “transformed” into that of the adult. The head of the fly, therefore, is practically a new structure de- veloped without reference to the larval head. In the evolution of the Diptera, however, the cyclorrhaphous way of forming the adult head has been derived from a more simple method retained in some of the lower flies. Among the nematocerous Diptera, as has been shown by Kellogg (1902) in Simulium and Bibiocephala, the imaginal (pupal) head may be formed simply and entirely within the loosened cuticle of the larval head, and the imaginal mouth parts are formed inside the cuticle of the larval mouth parts. The antennae of the pupa, because they are much longer than those of the larva, find space for their growth between the pupal head and the cuticle of the larval head, but their tips are retained in the corresponding larval organs. In Corethra, as described by Weis- mann (1866), the long slender antennae of the pupa become sunken into pouches of the pupal head, from which they are everted when the larval cuticle is shed. In Corethra the compound eyes are formed on the surface of the pupal head beneath the larval cuticle. In Tendipes (Chironomus) Miall and Hammond (1900) showed that both the antennae and the compound eyes of the pupa are developed within longitudinal infoldings of the epidermis of the dorsal wall of the pupal NO. 3 METAMORPHOSIS OF A FLY’S HEAD—SNODGRASS 15 head inside the larval cuticle. Dissection of a mature Tendipes larva reveals a pair of long pockets converging from the larval antennae to the posterior end of the head (fig. 5 A), each of which contains an axial tubular antenna (Ant) and, in the wall of its basal part, the de- veloping rudiment of a compound eye (E£). These elongate pockets Fic. 5.—Development of the frontal sacs. A, oculoantennal pockets from head of a mature tendipedid (chironomid) larva, Tendipes plumosus (L.), extending posteriorly from larval antennae. B, diagrammatic cross section of pupal head of Psychoda alternata showing open grooves (FS) containing imaginal antennae and rudiments of compound eyes (outline from Feuerborn, 1927). C, diagrammatic dorsal view of head of young pupa of same, showing oculoantennal grooves extended into pockets of prothorax (outline from Feuerborn, 1927). D, cross section of head of embryo of Me- lophagus ovinus showing origin of frontal sacs (FS) on sides of head (from Pratt, 1901). E, dorsal view of feeding apparatus of mature larva of Rhagoletis pomonella, with fully developed frontal sacs (FS) extending posteriorly from frontoclypeal plate (from Snodgrass, 1935). F, cross section of 7-hour prepupa of Drosophila melanogaster showing united frontal sacs produced into lateral pouches with folded walls (from Robertson, 1936). lie immediately beneath the ecdysial cleavage grooves of the larval head. Very similar groovelike pockets of Psychoda are described and figured by Feuerborn (1927) as infoldings of the pupal head (B, FS) open by narrow slits on the surface, and containing the developing an- tennae (Ant) and compound eyes (£). In Psychoda the grooves ex- tend into the front part of the thorax (C) as pockets, which deepen as the pupa develops. 10 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 It is probable that similar developmental processes occur in other Nematocera, though little attention has been given to the details of metamorphosis in these flies. The oculoantennal pockets of the head very clearly are equivalent to the peripodal pouches of the thorax in which the imaginal legs are developed and to the pouches that contain the wing rudiments. In the higher Diptera the oculoantennal pockets, known as the frontal sacs, are present in the larvae as long-necked pouches extend- ing from the posterior end of the frontoclypeal plate of the sucking apparatus into the thorax as far as the retracted brain, with which they are connected by ocular nerves (figs. 2B, 5 E,6 B, FS). In the strat- iomyid Odontomyia Jusbaschjanz (1910) says the pouches contain only the histoblasts of the compound eyes (fig. 6 B, FS), the antennae arising from the surface of the head as in Corethra. In all cyclorrha- phous flies that have been described, however, the frontal sacs contain the rudiments of both the eyes and the antennae. These sacs are formed in the embryo and are present in all stages of the larva, but reach their full development only in the last larval instar. In their early origin, therefore, the frontal sacs of the head in the cyclorrhaphous flies more nearly resemble the thoracic peripodal pouches of the legs than do the oculoantennal pockets of the Nematocera, which appear only in the prepupal stage. Because in the late embryo the sacs appear to arise from the inner end of the passage between the inner lamella of the head fold and the underlying frontoclypeal plate (fig. 4 B, FS), this passage (b) has been regarded as an unpaired part of the sacs, and the latter have been erroneously said to be invaginations from the atrium (Air), or from the “pharynx” if the atrium is mistaken for the pharynx. The point at which the sacs grow into the thorax (D, c) is simply overgrown by the head fold, and the true origin of the sacs is on the lateral parts of the embryonic head. According to Ludwig (1949) the imaginal discs of the compound eyes in the embryo of Calliphora arise as ectodermal thickenings on the lateral walls of the head, but in the larva both the ocular and the antennal rudiments are contained in a pair of membranous sacs lying along the sides of the oesophagus. Ludwig does not explain how the sacs are developed, or how they come to contain the histoblasts of the eyes and antennae. In his figure 57 he shows the left sac exactly as all other writers have depicted the frontal sacs, and yet he says “embry- onic studies reveal no such pouches.” Furthermore, Ludwig attributes to Pratt (1901) the absurd statement that the common opening of the sacs “is drawn forward and downward, and then posteriorly through the mouth,” and on this assertion he bases a criticism of Pratt’s work. NO. 3 METAMORPHOSIS OF A FLY’S HEAD—SNODGRASS 17 However, Pratt makes no such statement, or anything like it. More concisely than does Ludwig himself, Pratt describes in Melophagus ovinus the origin of the frontal sacs (“dorsal head discs”) as dorso- lateral thickenings of the epidermis of the embryonic head. Early in their history the discs begin to invaginate in the form of crescentic slits (fig. 5 D, FS), and later they move dorsally to the back of the head, where their outer parts unite in a single, transverse depression, while the inner parts increase in length and extend separately into the Aw Fic. 6.—Head of stratiomyid larva and sections of embryonic head of Calliphora. A, larval head of Ptecticus trivittatus (Say) partly ensheathed in fold of pro- thorax, dorsal. B, lengthwise section of larval head and prothorax of Odonto- myia (combination diagram from Jusbaschjanz, 1910, relettered). C, cross section near base of head of 15-hour embryo of Calliphora (from Ludwig, 1949). D, cross section of head lobe of 16-hour embryo of Calliphora, overhanging the labium (from Ludwig, 10949). body cavity as a pair of stalked sacs that lie in contact with the cere- bral ganglion. Now there takes place, from behind the mouth of the sacs (fig. 4 C, c), the formation of the dorsal fold (hf), which grows forward over the head. Since the inner lamella of the fold becomes closely adherent to the frontoclypeal plate, it thus comes about that in the larva the sacs appear to be attached to the posterior end of the larval sucking apparatus (figs. 2B, 5 E, FS). Their true opening at the posterior end of the head beneath a fold of the thorax (thf) is shown by Jusbaschjanz (1910) in his sectional figure of a stratiomyid larva (fig.6 B, FS). 18 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 From the description of the early history of the frontal sacs given by Pratt it is clear that the frontal sacs of the cyclorrhaphous flies can be correlated in their origin with the oculoantennal grooves of the pupal head in the Nematocera. That, in the former, the sacs arise in the embryo instead of in the pupa shows that the imaginal discs of the head have followed the same course of evolution as have those of the thorax, which also in the higher flies have come to be formed in the embryo. The further history of the frontal sacs has been followed by Wahl (1914) in Calliphora and by Robertson (1936) in Drosophila, Weis- mann (1864) observed that the head of the fly is formed from two “cell masses” (the frontal sacs), which at first are in contact and later become united. Jusbaschjanz (1910) noted that in a stratiomyid larva there is only one frontal sac (Kopffalte) at the time of pupation, from which fact he concluded that the two primary sacs must have united in a single pouch. Wahl (1914) specifically describes the formation of a single sac in the early pupa of Calliphora by a dissolution of the mesal walls of the original two sacs followed by a union of their outer walls. The resulting unpaired sac then increases in size by expansion of lat- eral pouches, and its walls become thrown into numerous irregular folds. In Drosophila Robertson (1936) says the closely appressed frontal sacs begin to fuse two hours after the formation of the pupar- ium. The median walls break down and the broken edges of one sac unite with those of the other until the two sacs have completely united (fig. 5 F, FS) except at their posterior ends where the optic concavi- ties are applied to the cerebral ganglia. At pupation the cephalic fold of the larva retracts (fig. 7 B, hf), the passage (b) beneath it opens and becomes continuous with the lumen of the now single frontal sac (FS), so that, as Wahl (1914) shows in the early pupa of Calliphora, the frontal sac comes to open directly to the exterior above the mouth of the cibarium (“pharynx”). The same thing was noted by Pratt (1897) in Melophagus, but Pratt’s language is somewhat confusing to a modern reader when he says “the lumen of the discs and that of the pharynx become completely merged and form together a single continuous space.”’ The “discs” are the frontal sacs, the “pharynx” is the larval atrium. When now the pupa is first exposed by the shedding of the last larval cuticle within the puparium, there is to be seen at the anterior end of the body only a great hole in the front of the prothorax (fig. 7 A). This stage is the cryptocephalic phase of the pupa. Shortly thereafter the walls of the cavity are sud- denly everted, and the pupa thus acquires a head (C). The pupal head is at first relatively small and not fully developed, but it takes on its NO. 3 METAMORPHOSIS OF A FLY’S HEAD—SNODGRASS I9 definitive size and structure (D, E) during the rest of this phanero- cephalic stage of the pupa. When the head of Drosophila is first everted, Robertson says, the eyes are brought to their final position, but are not yet histologically completed, and the antennae are simple thickenings of the front wall of the head. Bodenstein (1950) describes in detail the development of the compound eyes in Drosophila. Ludwig (1949) emphatically denies that there is any process of in- vagination involved in the formation of the head of the fly. However, Fic. 7.—The pupa. A, cryptocephalic pupal stage of Rhagoletis pomonella, ventral. B, lengthwise section of anterior end of 10-hour prepupa of Drosophila melanogaster showing opening of frontal sac just before pupation (from Robertson, 1936). C, early phanerocephalic pupal stage of Rhagoletis pomonella. D, mature pupa of Rhago- letis, lateral. FE, same, ventral. since the adult head is visibly everted in the pupal stage, it is not clear how it became introverted without a previous inversion. The frontal sacs are actually ingrowths of the embryonic integument, and an in- growth is usually called an “invagination,” though admittedly it is more properly an introversion. Furthermore, Ludwig criticizes a former statement by the writer (1935, p. 313) that “the entire facial region of the head, including the area of the frons and that of the imaginal antennae and compound eyes, is invaginated into the thorax.” This statment is in accord with the findings of other writers, since the time of Weismann (1864), and all that is needed to demonstrate its truth is a glance at a pupa in the cryptocephalic stage, whether of 20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, I22 Musca, Calliphora, Drosophila, or Rhagoletis (fig. 7 A). When the frontal sac is everted, it brings with it the eyes and the antennal rudi- ments, and its walls form the epidermis of all parts of the fly’s head except that part derived from the sucking apparatus of the larva. The cuticular skeleton of the latter is shed at the moult to the pupa, but the matrix of the organ must remain to form the more simple sucking ap- paratus (or “fulcrum’’) of the adult, though the transformation has not been observed. In the change from the larva to the adult the frontoclypeal plate of the larva undergoes a very considerable modification. First, it is dis- tinctly divided, in the fly, into frontal and clypeal elements ; the clypeal area retains the muscles of the cibarium, the frons now carries the attachments of the postcibarial frontal muscles of the stomodaeum. The shape of the clypeus in the adult becomes reversed from that of the larva, in that, though U-shaped or V-shaped in both, the open end is distal in the adult (fig. 1, Clp). The frons of the fly is a part of the head wall, including specifically the depressed area of the face (Fr) in which the antennae are lodged. Again we may point out that the frontal sacs of the cyclorrhaphous fly larva from which the imaginal head is formed are cephalic equiva- lents of the thoracic histoblasts, which latter not only give rise to the legs and wings, but in the higher flies regenerate the thoracic integu- ment as well. As an example we may refer to Robertson’s (1936) account of the formation of the imaginal thorax in Drosophila. As the histoblast pouches of the legs and wings open to allow the contained appendages to evert, their edges expand by cell proliferation, while the surrounding larval cells retreat and are gradually sloughed off into the body cavity to be devoured by phagocytes. The newly generated areas spread over the thorax, unite, and finally construct the entire thorax of the fly. In describing the formation of the thorax of Me- lophagus, Pratt (1897) says: “In proportion as the larval hypodermis disappears under the attack of the phagocytes, the edges of the imag- inal discs grow and take its place, forming the imaginal hypodermis.” The idea that the larval cells are first destroyed by phagocytes, how- ever, is not in accord with results of later investigators. The cephalic histoblasts of the fly have no opposition from larval cells because of the great reduction of the larval head ; the elaborate head of the cyclor- rhaphous fly is practically a new structure with no counterpart in the larva. Likewise, the mouth parts of the fly owe little to those of the larva. The larval mouth hooks are not re-formed in the pupa, and the fly has no trace of mandibles. The adult labium is formed from a pair of his- NO. 3 METAMORPHOSIS OF A FLY’S HEAD—SNODGRASS 21 toblastic pouches developed inside the larval labium. According to Wahl (1914) these ventral histoblasts give rise to the entire proboscis of the fly, including the hypopharynx, the maxillary remnants, and the labrum, which statement suggests that the matter should be reinvesti- gated. The cyclorrhaphous larva, as already observed, has no free hypopharyngeal lobe, and the salivary duct opens on the base of the labium (fig. 2C, S7Dct). In the fly, on the other hand, the salivary outlet duct traverses a median stylet arising at the base of the labium, which is commonly called the hypopharynx. Because this stylet gives passage to the salivary duct, however, Ferris (1950) asserts that it is not a hypopharynx, but a secondarily developed outgrowth containing the salivary outlet. According to the same interpretation the Hemiptera and Siphonaptera also should not have a hypopharynx. While it is generally true that the salivary outlet duct of insects opens between the base of the hypopharynx and the base of the labial prementum, the opening is sometimes on the base of the hypopharynx, as in the cock- roach (fig. 3 A, S/O), in dragonflies, and, as shown by Weber (1938), in the Psocoidea. The hypopharynx is a median, postoral outgrowth of the ventral wall of the head, principally on the maxillary segment, but it may encroach on the labial segment. If the organ includes a labial element, therefore, it is nonetheless a hypopharynx, and if the salivary duct opens into a pocket on its base it might traverse its entire length. In the larvae of nematocerous flies a hypopharynx is present, but, as in other holometabolous insects, it is united with the labium in a composite suboral lobe and the outlet duct of the salivary glands opens distally between the two component parts of the latter. The an- cestors of the Diptera, therefore, must have possessed a true hypo- pharynx, and there would seem to be no reason why it should not be restored in the adult, just as are the legs. Weismann (1864) called the median mouth stylet of the fly “die Kieferborste,” and described it as formed by the union of paired parts about a cellular strand that became the salivary duct. Again, we can say only that the pupal devel- opment of the mouth parts of the cyclorrhaphous flies needs further investigation, since the ordinary criterion of correlating the adult parts with the larval parts cannot be invoked. A comparison of the mouth parts of the fly with those of the cock- roach shows at least that the stylet containing the salivary outlet of the fly (fig. 3 F, Hphy) corresponds exactly in position with the free lobe of the hypopharynx in the cockroach (A, Hphy). Its grooved dorsal surface, moreover, is continued into the floor of the sucking pump (F, CbP), which represents the floor of the cibarium on the base of the hypopharynx in the cockroach. Even the oral arms of the suspensory 22 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 rods of the cockroach hypopharynx (A, y) may be retained in the flies as a pair of short cibarial processes (B, F, y) embracing the primary mouth (F, Mth’). Finally, in connection with the metamorphosis of the fly’s head, we should mention the ptilinum, since it constitutes an example of ex- ceptional development in the pupa of a special structure for the tem- porary use of the fly. The ptilinum is a vesicular introversion of the front of the head of the pupa in the schizophorous families of the Cyclorrhapha, which is everted by the emerging fly to open the anterior end of the enclosing puparium. After emergence, the lips of the open- ing come together in the long groove of the head that arches over the bases of the antennae (fig. 1 A, pts). As described by Laing (1935), in Calliphora the ptilinum is formed in the young pupa from the head wall just above the antennae, which on the third day of pupal life be- gins to introvert and soon becomes a crumpled sac inside the head with a greatly thickened cuticle. Eversion of the ptilinum in the emerging fly is brought about by blood pressure resulting from contraction of the abdomen. The surface of the organ in different flies may be smooth, covered with fine spicules, or, as in Gonia (fig. 1 D), thickly coated with coarse spines. After the ptilinum has served its purpose it is again retracted and remains as a large though shrunken body in the fly’s head. The retraction is caused by muscles, which are fully described by Laing. Some of the muscles are special ptilinal retractors, - and these muscles disappear during the first two days of the life of the fly. Metamorphosis in the cyclorrhaphous Diptera is a “change of form”’ in the insect as a whole, but it is not a transformation of the maggot into a fly. The maggot represents an extreme degree to which juvenile development among the insects has diverged from the evolutionary course that produced the adult, until the young insect has become an independent creature in no way structurally related to its parents. The embryo develops directly into the form of the larva and not into that of the insect that produced it, but certain cells of the larval tissues retain the potentiality of reproducing the corresponding adult tissues, while the rest of the larval tissues, after performing their temporary function, go into dissolution and become food for the growing imaginal tissues. The maggot is in no sense a recapitulation of any stage in the evolution of the fly, except larval stages of its more recent ancestors. The larval form is determined at an early period of development in the egg, and when the larva has completed its destiny it gives way to the ancestral development of the fly, but the manner in which the modern NO. 3 METAMORPHOSIS OF A FLY’S HEAD—SNODGRASS 23 fly is developed has no phylogenetic significance. The larval devel- opment and the adult development are known to be under control of hormones, but the mechanism of dual inheritance has not been explained. EXPLANATION OF LETTERING ON THE FIGURES a, membrane over frontoclypeal plate of larva, inner wall of head fold. Ant, antenna. Atr, head atrium. b, space between head fold of embryo and frontoclypeal plate. Br, brain. c, posterior end of frontoclypeal plate, origin of inner wall (a) of head fold. Cb, cibarium. CoP, cibarial pump. Clp, clypeus. Cr, crop. d, end of dorsal wall of head fold. dicb, dilator muscles of cibarial pump. e, H-shaped sclerite supporting mouth hooks. E, rudiment of compound eye. f, paraclypeal phragma. fm, food meatus. Fr, frons. FS, frontal sac. Gng, ganglion. h, hinge of clypeus on frons. hf, head fold. Hphy, hypopharynx. hpl, hinge plate of clypeus. H st, hypostome. H stl, haustellum. hy, hyoid sclerite. L, legs. Lb, labium. Lol, labellum. LH, external larval head lobe. Lm, labrum. mh, mouth hooks of larve. Mth', primary mouth (entrance to sto- modaeum). Mth", secondary mouth (entrance to cibarium). Mth'", tertiary mouth, prestomum (aperture to food meatus between labella). M-xPlip, maxillary palpus. NC, nerve cord. Nv, antennal nerve. Oe, oesophagus. Phy, pharynx. Ptl, ptilinum. pts, ptilinal sulcus. Rst, rostrum of proboscis. SIDet, salivary duct. SIO, salivary orifice. Stom, stomodaeum. Th, thorax. thf, thoracic fold. Vent, ventriculus. vf, ventral head fold. W, wing. y, oral arm of hypopharyngeal suspen- sorium, or of floor of cibarium. 24 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I22 REFERENCES BovENSTEIN, D. 1950. The postembryonic development of Drosophila. In Demerec, M., Biology of Drosophila, pp. 275-367, 33 figs. New York. Bonuae, P. F. 1951. The skeleto-muscular mechanism of the head and abdomen of the adult horsefly (Diptera: Tabanidae). Trans. Amer. Ent. Soc., vol. 77, pp. 131-202, 31 figs. Cook, E. F. 1949. The evolution of the head in the larvae of Diptera. Microentomology, vol. 14, pp. 1-57, 35 figs. Ferris, G. F. 1950. External morphology of the adult (of Drosophila). In Demerec, M., Biology of Drosophila, pp. 368-419, 22 figs. New York. FEUERBORN, H. J. 1927. Die Metamorphose von Psychoda alternata Say. I. Die Umbildungs- vorgange am Kopf und Thorax. Zool. Anz., vol. 70, pp. 315-328, 8 figs. GouIn, F. 1949. Recherches sur la morphologie de l’appareil buccal des diptéres. Mém. Mus. Nat. Hist. Nat., n.s., vol. 28, pp. 167-260, 64 figs., 3 pls. Hotmcren, N. 1904. Zur Morphologie des Insektenkopfes. II. Einiges tiber die Reduktion des Kopfes der Dipterenlarven. Zool. Anz., vol. 27, pp. 343-355, 12 figs. JUSBASCHJANZ, S. 1910. Zur Kenntnis der nachembryonalen Entwicklung der Stratiomyiden. Jenaische Zeitschr. Naturw., vol. 46 (N.F.38), pp. 681-736, 7 figs., I pl. Kettoce, V. L. 1902. The development and homologies of the mouth parts of insects. Amer. Nat., vol. 36, pp. 683-706, 26 figs. LAING, JOYCE. 1935. On the ptilinum of the blow-fly (Calliphora erythrocephala). Quart. Journ. Micr. Sci., vol. 77, pp. 497-521, 14 figs. Lupwic, C. E. 1949. Embryology and morphology of the larval head of Calliphora erythro- cephala (Meigen). Microentomology, vol. 14, pt. 3, pp. 75-111, figs. 43-65. Mratt, L. C., and Hammonp, A. R. 1900. The structure and life-history of the harlequin fly (Chironomus), 196 pp., 127 figs. Oxford. PANTEL, J. 1898. Le Thrixion halidayanum Rond. Essai monographique sur les caractéres extérieurs, la biologie et l’anatomie d’une larve parasite du groupe des Tachinaires. La Cellule, vol. 15, pp. 1-285, 6 pls. NO. 3 METAMORPHOSIS OF A FLY’S HEAD—SNODGRASS 25 Pratt, H. S. 1897. Imaginal discs in insects. Psyche, vol. 8, pp. 15-30, 11 figs. 1901. The embryonic history of imaginal discs in Melophagus ovinus L., together with an account of the earlier stages in the development of the insect. Proc. Boston Soc. Nat. Hist., vol. 29, pp. 241-272, 7 pls. Rosertson, C. W. 1936. The metamorphosis of Drosophila melanogaster, including an accu- rately timed account of the principal morphological changes. Journ. Morph., vol. 59, pp. 351-399, 4 pls. ScCHREMMER, F. 1951. Die Mundteile der Brachycerenlarven und der Kopfbau der larve von Stratiomys chamaeleon L. Osterreichische Zool. Zeitschr., vol. 3, Pp. 326-397, 25 figs. Swnoperass, R. E. 1924. Anatomy and metamorphosis of the apple maggot, Rhagoletis pomo- nella Walsh. Journ. Agr. Res., vol. 28, No. 1, 36 pp., 8 figs. 6 pls. 1935. Principles of insect morphology. 667 pp., 319 figs. New York and London. WaRL, B. 1914. Uber die Kopfbildung cyclorapher Dipterenlarven und die postem- bryonale Entwicklung des Fliegenkopfes. Arb. Zool. Inst. Univ. Wien, vol. 20, pp. 159-272, 20 figs., 3 pls. Weser, H. 1938. Beitrage zur Kenntnis der Uberordnung Psocoidea. I. Die Labial- driisen der Copeognathen. Zool. Jahrb., Anat., vol. 64, pp. 243-286, 16 figs. WEISMANN, A. 1864. Die nachembryonale Entwicklung der Musciden nach Beobachtungen an Musca vomitoria und Sarcophaga carnaria. Zeitschr. wiss. Zool., vol. 14, pp. 187-336, 7 pls. 1866. Die Metamorphose der Corethra plumicornis. Zeitschr. wiss. Zool., vol. 16, pp. 45-127, 5 pls. . “ ' ty ri ~ ’ ¢ ~ ?. v 1 ay ore i) ss “ 4 ; « a , ‘ ; , tad fe! | hae y ) at ee On ; ares SMITHSONIAN MISCELLANEOUS COLLECTIONS VOLUME 122, NUMBER 4 Roebling Fund SOLAR VARIATION, A LEADING dlc eno LE MMEIN TE By Cc. G. ABBOT Research Associate, Smithsonian Institution (PusticaTtion 4135) CITY OF WASHINGTON PUBLISHED BY THE SMITHSONIAN INSTITUTION AUGUST 4, 1953 The Lord Baltimore Mress BALTIMORE, MD., U. 8 A. Roebling Fund SOLAR VARIATION, A LEADING WEATHER ELEMENT By C. G. ABBOT Research Associate, Smithsonian Institution CONTENTS Page IntRopucTION. (Adverse contemporary opinion; three propositions contra thereto; a suggested supporting theory; citations of pertinent litera- [OPA Sea ee Aon One COS Pea TO DOES On oOo CORO OOOD COO ono OOD 2 Proposition I: Correlation of other solar phenomena with solar-constant measures indicates the probable reality of solar variation. (With eight RD HOPING GGUS.) fol siaic xcteipialepd & spoke © eines ae oia-@.so ehsseneke) suaieielar ata hahaa 5 Proposition II: Phenomena exist harmonious with a master period of 22} years in the variation of solar-constant measures. (With six supporting graphs and reference to Hale's discovery.) ooo cicce cca sejeocs esc nene nai 10 Proposition III: Integral submultiples of 223 years are regular periodicities in solar variation. (With one supporting table and four graphs.)...... 18,20 INTERLUDE: On the purpose and accomplishments of the Smithsonian re- Search on the vatiation of total! solar wmadiationy...c 4... scl «=+4-\ee a4 - 18 Proposition IV: Correlations exist between variations in solar-constant measures and weather, not involving periodicities. (With three sup- PORTS MORADMS Sl ovace sisic'g oe. 03 Spero else she a Meese erations, 6 wiape Sesion yo. open 25 Proposition V: Correlations exist between regular periodic changes in the solar-constant measures and weather changes. (Interlude on lags: Lags in weather responses to solar changes; impossibility of recognizing solar influences without knowing the periods of variation of solar-constant measures. With seven supporting graphs and three supporting forecasts MANY NV EAU STANA COVANCEs) (a's ssa cv atayaye oy asst Ne OAS tis. cle eI ToT: 26 RUN ARVe Bosc ction, Lata echt ae le Ute OS oi Nadie gC ee 2 33 INTRODUCTION On January 28, 1953, the American Meteorological Society devoted the day to consideration of the influence of solar variation on weather. An early speaker said he acknowledged the results of conscientious studies of total solar variation, which had been made, as probably sound. But the variations found appeared to be of the order of 1 per- cent, or much less. No reasonable theory could show that these might have important weather influences. He distrusted statistical conclu- sions, unless grounded on sound theory. Statistics might show that it is dangerous to go to bed, for the great majority of decedents died in bed. The remainder of the panel appeared to agree with him that, because percentage solar-constant variations are small, it is needless to consider the possibility that variations of total solar radiation affect weather importantly. The discussion was mostly confined to matters relating to the high atmosphere, in the stratosphere and beyond. Sug- gestions were discussed as to whether the large effects of solar changes known to exist in the high atmosphere could be connected with weather changes in the troposphere. No positive result was reached. One gathered the impression that meteorologists are so firmly con- vinced that variations of total solar radiation are of negligible weather influence, and that statistical methods of proof are to be ignored, that they probably do not read attentively any publications of the contrary tendency. I do not agree that the last word has been said. I submit several propositions. 1. Statistically derived results may be accepted, if well supported by observation, without supporting theory. Kepler’s laws were accepted statistically for many years before there was any supporting theory. 2. A conclusion may be accepted as a valuable working hypothesis, without being proved in the rigid sense, e.g., that the square of the hypotenuse of a right-angle triangle equals the sum of the squares of the other two sides. 3. In lieu of theoretical support, to be supplied later, a statistically derived proposition, A, may be adequately supported as a working hypothesis, if accepted phenomena, B, C, D, E, — — — — which stem from a related source, are harmonious with proposition A. I propose to show that the proposition that the variations of solar radia- tion are important weather elements is thus adequately supported. SMITHSONIAN MISCELLANEOUS COLLECTIONS, VOL. 122, NO. 4 NO. 4 SOLAR VARIATION, WEATHER ELEMENT—ABBOT 3 Further support comes when forecasts with high correlation compared to probable error result from such hypotheses. J depend strongly on this paragraph in what follows. However, I will venture a suggestion toward a theory of the matter. 1. It is commonly observed that the temperature is responsive to the direction of the wind. 2. The direction of the wind depends on the orientation of the sta- tion with respect to the cyclonic structure prevailing. 3. H. H. Clayton found, by his tireless statistical work, over a quar- ter of a century ago, that the “centers of action,” about which the cyclonic structure forms, are largely displaced in position on the earth’s surface, as solar-constant measures rise and fall. 4. If this Clayton effect is accepted, the mystery is no longer why large temperature and associated weather changes follow small per- centage solar-constant changes, but rather why the “centers of action” shift when solar-constant changes occur. 5. If meteorologists doubt the Clayton effect, they may find 30 years of 10-day solar-constant measures in paper No. 27, cited below, which they may compare with weather maps of the period 1920 to 1950. To provide a groundwork for reference, I first list certain pertinent publications of the past 20 years. A book would be needed if one col- lected all the evidence which supports the conclusion in hand. I shall give below a few of the more telling references. Those interested may find numerous others from the papers cited and from H. H. Clayton’s earlier papers in the Smithsonian Miscellaneous Collections. Students of research know that early work is often found partly erroneous as later results come in. So it is here in some measure. Nevertheless, I think all the papers cited here still retain features of some value and interest. Fundamental to the whole pattern, however, is the paper “Periodicities in the Solar-constant Measures,’’ Smithsonian Miscel- laneous Collections, vol. 117, No. 10, 1952 (reference No. 27, below), to which I particularly invite attention. LITERATURE PERTAINING TO SOLAR RADIATION AND ASSOCIATED PHENOMENA (BY ABBOT UNLESS OTHERWISE INDICATED) 1. How the sun warms the earth. Ann. Rep. Smithsonian Inst., 1933, pp. 149-179. 2. Sun spots and weather. Smithsonian Misc. Coll., vol. 87, No. 18, 1933. 1See Clayton, H. H., Solar radiation and weather, Smithsonian Misc. Coll., vol. 77, No. 6, June 20, 1925; also his Solar relations to weather, vol. 1, p. ix, and vol. 2, p. 384, 1943. 16a. 20. 27. SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 Solar radiation and weather studies. Smithsonian Misc. Coll., vol. 94, No. 10, 1035. Weather governed by changes in the sun’s radiation. Ann. Rep. Smith- sonian Inst., 1935, pp. 93-115. Rainfall variations. Quart. Journ. Roy. Meteorol. Soc., vol. 61, pp. 90-92, 1935. The dependence of terrestrial temperature on the variations of the sun’s radiation. Smithsonian Misc. Coll., vol. 95, No. 12, 1936. Further evidence of the dependence of terrestrial temperatures on the varia- tions of solar radiation. Smithsonian Misc. Coll., vol. 95, No. 15, 1936. Cycles in tree-ring widths. Smithsonian Misc. Coll., vol. 95, No. 19, 1936. Some periodicities in solar physics and terrestrial meteorology. Zvlastni Otisk, vol. 18, pts. 1-2 (54-55), Io pp., 1938. Prague. Solar variation and the weather. Nature (London), vol. 143, p. 705, April 1930. . The variations of the solar constant and their relation to weather. Quart. Journ. Roy. Meteorol. Soc., vol. 65, pp. 215-236, 1939. . Variations of solar radiation (Dixon). Quart. Journ. Roy. Meteorol. Soc., vol. 65, pp. 383-384, 19309. . On periodicities in measures of the solar constant (T. E. Sterne). Proc. Nat. Acad. Sci., vol. 25, pp. 559-564, 1939. On solar-faculae and solar-constant variations (H. Arctowski). Proc. Nat. Acad. Sci., vol. 26, pp. 406-411, 1940. . An important weather element hitherto generally disregarded. Smithsonian Misc. Coll., vol. 101, No. I, 1941. On solar-constant and atmospheric temperature changes (H. Arctowski). Smithsonian Misc. Coll., vol. 101, No. 5, 1941. Solar relations to weather (H. H. Clayton). Vols. 1 and 2, 1943. (Privately printed.) . A 27-day period in Washington precipitation. Smithsonian Misc. Coll., vol. 104, No. 3, 1944. Weather predetermined by solar variation. Smithsonian Misc. Coll., vol. 104, No. 5, 1944. The solar constant and sunspot numbers (L. B. Aldrich). Smithsonian Mise. Coll., vol. 104, No. 12, 1945. . Correlations of solar variation with Washington weather. Smithsonian Misc. Coll., vol. 104, No. 13, 1945. . The sun makes the weather. Scientific Monthly, vol. 62, pp. 201-210, 34I1- 348, 1946. . The sun’s short regular variation and its large effect on terrestrial tempera- tures. Smithsonian Misc. Coll., vol. 107, No. 4, 1947. . Precipitation affected by solar variation. Smithsonian Misc. Coll., vol. 107, No. 9, 1047. Solar variation attending West Indian hurricanes. Smithsonian Misc. Coll., vol. 110, No. 1, 1948. . Magnetic storms, solar radiation, and Washington temperature departures. Smithsonian Misc. Coll., vol. t10, No. 6, 1948. Short periodic solar variations and the temperatures of Washington and New York. Smithsonian Misc. Coll., vol. 111, No. 13, 1949. Periodicities in the solar-constant measures. Smithsonian Misc. Coll., vol. 117, No. 10, 1952. NO. 4 SOLAR VARIATION, WEATHER ELEMENT—ABBOT 5 28. Important interferences with normals in weather records associated with sunspot frequency. Smithsonian Misc. Coll., vol. 117, No. 11, 1952. 29. Solar variation and precipitation at Peoria, Illinois. Smithsonian Misc. Coll., vol. 117, No. 16, 1952. 30. Solar Aktivitat und Atmosphare (H. Koppe). Zeitschr. fiir Meteorol., vol. 6, Heft 12, pp. 360-378, December 1952. 31. Solar variation and precipitation at Albany, N. Y. Smithsonian Misc. Coll., vol. 121, No. 5, 1953. 32. Long-range effects of the sun’s variation on the temperature of Washington, D. C. Smithsonian Misc. Coll., vol. 122, No. 1, 1953. PROPOSITION I Correlation of other solar phenomena with solar-constant measures indicates the probable reality of solar variation Applying my criterion No. 3, above, I shall now cite evidence that variation observed in Smithsonian solar-constant measures is associ- ated with variation (a) in solar faculae areas; (b) in sunspot num- bers; (c) in calcium flocculi areas; (d) in incidence of magnetic storms ; and (@) in ionospheric data. Dr. H. Arctowski, of Poland, was attending a meeting in Washing- ton when his savings and work were swept away by the invasion of his country. I suggested to John A. Roebling that it would be helpful if so eminent a European meteorologist should examine our case for the variation of the sun and its control of weather. Mr. Roebling consented to support this project. After several months Dr. Arctowski told me: “T believed in neither proposition. But I determined to give them a fair trial. When I found them unsupported, I intended to tear up my papers and resign. I could not take money under false pretenses.” Af- ter a brief time, however, Dr. Arctowski came to believe in both propo- sitions, and said: “I have become more enthusiastic about them even than Dr. Abbot himself.” a. Referring to Dr. Arctowski’s paper, reference No. 14 above, I reproduce his figures I, 3, 4, and 5 as figures I, 2, 3, and 4 herein. b. Referring to L. B. Aldrich’s administrative report on the Astro- physical Observatory for 1952 (Rep. Secretary Smithsonian Inst., 1952, p. 131), I reproduce here as figure 5 his figure showing the correlation of solar-constant measures with sunspot numbers. c. Referring to my paper “Weather Predetermined by Solar Vari- ation,” reference No. 18 above, I reproduce figure 6 of that paper as figure 6 here. I call attention to the similarity of the full and dotted curves of the figure. This similarity indirectly proves the correlation claimed as c, above. Each month the curves represent means of effects on numerous occasions. 6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 FEB. £926 48 20 23 Fic. 1.—Variations of the solar constant and of areas of solar faculae. Daily solar-constant values for February and March, 1926, and areas of faculae. OCT, /929 =. Pe era Ae eG A Al A . necewure oe eee en Pe Ot SRR Se OR SES Fic. 2.—Discontinuous trends in solar constant and solar faculae. Solar constants and faculae, October, November, and December, 1929. NO. 4 SOLAR VARIATION, WEATHER ELEMENT—ABBOT 7 -q>~ - Ze Mik s 4; N id ‘ A UN ieee a fal _ JESS Lal af Ath Vea a yi fe NC ine ali 2400 “4 =! ° #2 2 Fics. 3 AND 4.—Time relations between maxima and minima in the solar constant and solar faculae. Means of faculae and solar constants for the 5 days before and the 5 days after the dates of 72 selected days of maxima and 82 days of minima of solar constants. 1.950 & & Solar Constant Values 4 ~~ (The number near each point indicates the number of monthly means included in each group.) . 7 Sunspot numbers Fic. 5.—Monthly mean values of the solar constant compared with monthly means of sunspot numbers for the same days. AEE ah oy va a a 4 aN ry i i] Z mig ti inl Bi ik ws ha SS e Hil : TT ial) oh aw 4 AA eA Se Se a“ wea a I a A cae maa mks ENS pe eer MeCN Paleo ds (rie eat ra i am Fo SS=SsaecSe = ener. A ica 2 Scar ha ee A A A i ate ize Bh 9 6 a me PES ala ae ee ee (ie eS, Sal ey AS] TT TA ak eM “a pA NSAI SEL JE NEN PON EZ Ne TC Pas 006s En Na a ; jae SA IP Le OH Cees encom oes i PRBMPEN Se VRE 2h Se ea ee ay RRB EE AEP EEA PESO iio 2 ES a a No i Fic. 6.—Average marches of temperature departures, Fahr., at Washington, DD sGe accompanying sequences of solar change (a) of the solar constant in years 1924 to 1936; (b) of character figures for solar calcium flocculi in years I910 to 1937, for months January to December. Ordinates are temperature departures; abscissae are days from beginning of solar-constant sequence. Flocculi band curves are displaced 2 days to right. Temperature changes following rising solar radiation above, falling radiation below. 8 NO. 4 SOLAR VARIATION, WEATHER ELEMENT—ABBOT 9 d. Referring to my paper “Magnetic Storms, Solar Radiation, and Washington Temperature Departures,” reference No. 25 above, | reproduce figure 2 of that paper as figure 7 here. I call attention to the sharp depression of the solar-constant measures by 4 percent on the day of the height of the magnetic storm. It is the mean result repre- senting 53 great magnetic storms over the years 1923 to 1946. Fic. 7—Depression of solar constant attending severe magnetic storms. Abscissae, days before and after height of storm; ordinates, solar constant (to be prefixed by 1.9). I refer also to the note by F. E. Dixon of the Imperial College of Science and Technology, reference No. 12 above, and to H. Koppe’s conclusions, reference No. 30 above. e. Referring to my paper “The Sun’s Short Regular Variation and Its Large Effect on Terrestrial Temperatures,” reference No. 22 above, table 7 of that paper is from values of the ionospheric quantity, Fe, furnished me by Dr. John Fleming from records of the ionospheric 10 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 stations at Huancayo and Watheroo for the years 1938 to 1944. As given there, the records have been cleared of average monthly march and of sunspot influence, and are as follows: TABLE 1.—lonospheric data, Fe. Monthly and sunspot effects removed Months 1938 1939 1940 1941 1942 1943 Analy uaeiecriced cence 378 369 341 352 338 325 Mebruanyyee cetacean 375 360 344 351 328 330 IMianchis teens ecteen os eae 376 344 347 340 340 334 NOTH (ican vida de soe cae Oe 384 343 331 322 323 B17 May Pisa tertisnterman area eect bie 370 336 313 206 303 204 BLS RES + Ae RE oP cata Me 342 328 311 203 206 286 Jialy; S85 bd ak eats eek 342 334 313 304 300 287 TS ER US) AES TATE OE ATTRA SE 349 345 330 318 302 203 September saree as screstakis 354 366 344 325 312 209 October? Mevcicrscheiaci:s ets 361 3061 353 330 320 304 INOVemDeny eapetceeieenreties 370 352 359 332 328 314 December Gy. siicyeciacposes- 375 346 357 334 329 322 I shall show in a later section that variations in solar-constant meas- ures, among many others, have regular periods of 6-1/30, 9-7/I0, 114, and 13-1/10 months. I do not use longer periodicities than these here, because the ionospheric data are of too brief duration. In figure 8° I show the mean curves representing these periods in the ionospheric quantity Fe, computed from the table just given. The four curves are, respectively, means of 12, 7, 6, and 5 repetitions of the periods. Their amplitudes, respectively, are 4, 44, 9, and 63 percent of mean Fe. The amplitudes of the corresponding curves of variation of the solar-constant measures (see reference No. 27 above) are, respec- tively, 12/100, 10/100, 17/100, and 11/100 percent, being means ob- tained from 16 to 28 repetitions, according to length of period. With these correlations shown in figures 1-8, I rest my claim that criterion No. 3 is satisfied as regards the reality of solar variation. Other evidence could be given, but this seems sufficient to establish as a reasonable working hypothesis that there is really a variation in the output of total radiation from the sun. PROPOSITION II Phenomena exist harmonious with a master period of 223 years in the variation of solar-constant measures I shall now show that (a) the features of solar-constant measures themselves of 1924 to 1927 are approximately repeated after about 23 2 Figure 8 will be referred to again later. NO. 4 SOLAR VARIATION, WEATHER ELEMENT—ABBOT Dal: years in the years 1947 to 1950; (0b) this 22$-year period is also found in sunspot frequency; (c) also in the magnetic polarity of sunspots ; (d) also in the thickness of tree rings; (e) also in terrestrial tempera- tures ; (f) also in terrestrial precipitation. a. To show the master period in solar variation, I reproduce here as figure 9 figure 4A from my paper “Periodicities in the Solar-con- stant Measures,” reference No. 27 above. The amplitude is 0.9 percent. Fic. 8.—Variation of Fe in solar periods of 6-1/30, 9-7/10, 114 and 13-1/10 months. b. I reproduce here as figure 10, figure 10 of my paper “Solar Radi- ation and Weather Studies,” reference No. 3 above. It will be found that alternate sunspot-cycle areas, i. e., the right-hand curves of figure 10, are all greater in area included by the curves than the left-hand areas. So the double of the usually termed ‘‘114-year cycle” in sunspot frequency is also a sunspot period. Note that a line through sunspot minima would incline to the left, as years increase, which shows that period to be less than 23 years. c. Dr. George E. Hale discovered over 40 years ago the reversal of I2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 polarities of sunspots with alternate recurrences of the 114-year cycles. That is, he discovered a period of about 223 years in sunspot mag- netism. d. I reproduce figure 30 from my paper just cited (No. 3 above) as figure 11 here. It shows similar features in the march of tree-ring 240 ia’) Po Departures from 1.90 calories in ten-thousandths. 200 Fic. 9.—Comparison of solar constants 1924-1927 (heavy lines) and 1947-1950 (light lines). widths in southern California for four successive cycles of 23 years each. These features stand out clearly in the mean curve at the bottom of figure IT. e. I reproduce here as figure 12, figure 1 of my paper “Some Peri- odicities in Solar Physics and Terrestrial Meteorology,” reference No. 9 above. The figure traces 23-year cycles in the temperature of St. Petersburg, Russia, from 1752 to 1912, and also brings out the double period of 46 years. f. I reproduce here as figure 13, figure 22 of my paper “Weather AC (iol al mem = ie Se Sabi te pad HH Ge hae el a a -CCOA ha! A SEA ae inl Cae ‘aa a I \ fae et Ba ig x i i a a os OS e's 1b SAR AMMA Unt TT TT TT PAN SS 8 8S ea 1 Rage ale 2a Se deals ba a ell hana al ST Fic. 10—Wolf sunspot numbers, 1810-1933. 1875 -1897 23-YEAR PERIOD IN TREE RINGS FROM See SO. CALIFORNIA 15 Fic. 11.—Cycles of 23 years in tree-ring widths. Individual cycles of 23 years show features which are found preserved in the mean of four cycles, or g2 years. 14 1752 Ss a — 00 HY Wy pall a Ve VOL. 122 SMITHSONIAN MISCELLANEOUS COLLECTIONS 16 *saoAD Sutpadeid JO uoreIapisuos Aq apeut (gf61 wos ‘outy uly} :PE61 WorZ ‘oUT] PeHop) sysedso10,~ ‘saTIAD SAISSaDONS UL sainyeoy AvpIUNIs jUasoidot sioyayT ‘“sopoAo steak-€z ur pasuesse ‘survow Suruuns yWUOU- -§ Aq poyjoous “TIT ‘elloag je uoneydie1g—€I “914 [25s 2S ESS ee ae ee kes Fe ee de is et ee ee ee eee ee eee Pe IN 7 i A | NT Mery al UT | OR ‘ay lh CR a [ATU es SN alN zsh A A | aaa | ee ee ee oo! ae a ik vee A eR = szg! 4 OT A ye UT At oh A PAA Se ae A Pa a SS ee Re SS Caio a LAM TN Me te fl MAM LT ta PP ese PPV A ie VO NIN ae ee). Se ee SSS SSS Sa Se SS SSeS Le) © &¢ AWWYON 1N3903d NO. 4 SOLAR VARIATION, WEATHER ELEMENT—ABBOT EF Predetermined by Solar Variation,” reference No. 18 above. It shows how the features of precipitation at Peoria, Ill., tend to repeat them- selves at intervals of slightly less than 23 years. PERCENTAGES FROM NORMAL PRECIPITATION Fic. 133A.—Mean 223-year cycle in Southern New England precipitation. 1750 to 1931. Mean of 8 cycles. g. I reproduce here as figure 13A, figure 1 of my paper “Rainfall Variations,” reference No. 5 above.® Many other harmonious phenomena might be brought forward, but sufficient has been shown to support the working hypothesis of a 223- year period in solar variation. 3 The New England drought of 1952 falls in timely with this curve. 18 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 PROPOSITION III Integral submultiples of 223 years are regular periodicities in solar variation I shall show that (a) at least 23 such periods were found by tabu- lating solar-constant measures of the years 1924 to 1950; (0) in tabu- lations of the longer submultiple periods, integral submultiples of these long periods, which, of course, are also integral submultiples of the master period of 223 years, appeared plainly in the mean values; (c) several of these submultiple periodicities were sought for and found in ionospheric records; (d) by analogy to harmonics in musical sounds, since three integral submultiples of 22% years were discovered as supposedly isolated periods in solar variation 20 years ago, it is rea- sonable to expect that a large number of integral submultiples of 223 years will be found to occur as regular periodicities in solar variation. Before disclosing these evidences I insert an account of the purpose and results of the Smithsonian solar-constant campaign. INTERLUDE On the purpose and accomplishments of the Smithsonian research on the variation of total solar radiation Measurements of the solar constant of radiation were made by Dr. S. P. Langley at Allegheny, and then in his famous expedition to Mount Whitney, Calif., in 1881. Becoming the third Secretary of the Smithsonian Institution in 1887, one of his first acts was to found the Astrophysical Observatory. After completing its first research on the infrared line and band spectrum of solar radiation, in the year 1902 Dr. Langley directed that the measurement of the solar constant of radiation should be undertaken, not especially for fixing that constant, but rather, by a long series of measurements, to find if it is a variable. His impelling thought was that in solar variation might lie a hitherto unknown weather element of great significance. Dr. George E. Hale cordially seconded this project, and, after the establishment of Mount Wilson Observatory, he urged Langley to undertake the research there. Accordingly I was sent out in 1905, and excepting 1907, 1917, 1918, and 1919, made measurements of the solar constant there every year up to and through 1920. L. B. Aldrich ob- served there in 1917, 1918, and 1919. We also, following Langley’s original suggestion, erected a tower telescope with mirrors, forming a solar image 20 centimeters in diameter. This image was allowed to drift across the slit of the spectrobolometer. Every day of solar-con- NO. 4 SOLAR VARIATION, WEATHER ELEMENT—ABBOT 19 stant measurement, in the years 1913 to 1920, we made automatic drift curves, showing the distribution of energy in many wavelengths across the east-west diameter of the sun. This, too, was done expressly to discover variations useful for weather forecasting. A positive corre- lation was discovered between the solar constant and solar-contrast measures. (See also, in that connection, paper No. 27 cited above.) In 1917, H. H. Clayton, then chief forecaster for Argentina, in- formed Dr. Walcott, then Secretary of the Smithsonian, that, by com- bining into large groups the Mount Wilson solar-constant measures, he had secured sufficient accuracy in mean values to show direct cor- relation with weather elements. This led us to establish a solar-constant station at Calama in the nitrate desert of Chile. Soon after, with John A. Roebling’s aid, it was removed to Mount Montezuma, at 9,000 feet altitude. Since 1920, when possible, daily measures of the solar con- stant of radiation have been made there and also at other Smithsonian observing stations on high mountains in arid lands. Mr. Clayton pub- lished many papers showing the correlation of solar-constant measures with weather. After his return to Massachusetts he conducted pri- vately for many years, till his death, a long-range weather-forecasting business, based on solar variation, and had many paying clients. About 20 years ago, having a long series of 10-day mean values of the solar-constant measures, I made a chart of them extending the length of my office. Standing at a distance, I sought to discover repeti- tions of configurations in the variations. I noted a small regular varia- tion of slightly more than 8-months period. Proceeding similarly, I discovered regular periods of variation of about 11} months, and of about 39 months. It then occurred to me to find the least number of months of which, within the errors of determination, these three peri- ods would be approximately integral submultiples. The number 273, seven times 39, 24 times 114, and 34 times 8, seemed best. This num- ber, 273 months, recommended itself as a solar period, because it is approximately twice the sunspot cycle and thus equal to Hale’s mag- netic cycle in sunspot polarities. Having three integral submultiples of 273 months represented in the variation of solar-constant measures, I naturally sought for others. This search, as completed for the present, is described in my paper “Periodicities in the Solar-constant Measures,” published in 1952, ref- erence No. 27 cited above. As I shall show, it would be quite tmpossi- ble for meteorologists to discover these regular periodicities in weather elements had they not first been found in solar variation. In passing, I remark that it greatly strengthens our case for the va- lidity of solar-constant work that the 10-day means, covering the 30- 20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 year interval 1920 to 1950, which yielded the results published in paper No. 27 cited above, rest throughout the 30 years on two sta- tions in opposite hemispheres. Winter in California coincides with summer in Chile. For several years the 10-day means from Mount St. Katherine, in Egypt, also contributed to the results published in paper No. 27. I now proceed with the correlations promised above. a. I quote, as table 2, part of table 1A from paper No. 27 cited above. TABLE 2.—Periodicities in solar-constant observations Period Period Period Amplitude Fraction Period Amplitude Fraction Months Percent of 272 Months Percent of 272 2h 0.05 1/127 13-1/10 0.11 1/21 3-1/20 0.05 1/90 152 0.09 1/18 44 0.06 1/63 223 0.07 ie 5-1/18 0.05 1/54 243 0.12 I/II 6-1/30 0.12 1/45 304 0.13 4 7 0.08 1/39 345 0.15 3 8-1/14 0.06 1/34 39 0.20 + 9-1/10 0.08 1/30 454 0.13 * 4 9-7/10 0.10 1/28 544 0.13 t 10-6/10 0.06 1/26 68 0.25 4 114 0.17 1/24 Ol 0.12 4 11.43 0.11 1/24 272 Hi 12.0 0.20 * This figure for amplitude was fixed before extraneous periods were removed, as in gure 14. b. I now show, as figure 14, six broken curves and one smooth curve, all relating to the period of 454 months in solar variation. Curve A represents the direct mean of seven repetitions, from the monthly means of the solar-constant measures, of the 454-month period. It is plain that it contains a period of 454+3 months. This period being removed, we have curve B. Now a period of 454~4 months is dis- covered. Removing it from curve B we have curve C. Then a period of 454+2 months seemed indicated. Removing it from curve C, we have curve D. There now appears a period of 4535 months. Re- moving it we have curve E. It discovers a period of 454+7 months. Removing it, we have curve F. Curve F contains a period of 455+ 13 or 34 months, but I do not remove it. For it is now easy to draw the smooth curve G, which is the real curve of the 454-month period. As will be seen, the researcher has no option. Once started he must follow this path. The periods discovered in solar variation by NO. 4 SOLAR VARIATION, WEATHER ELEMENT—ABBOT 21 figure 14 are 4, 1/12, 1/18, 1/24, 1/30, 1/42, and 1/78 of 223 years. c. I again invite attention to figure 8, which shows that periods ob- served in solar-constant variation of 6-1/30, 9-7/10, 114, and 33-1/10 months also occur in the ionospheric data on Fe given in table 1. There is another aspect of this matter of Fe which adds to its evi- dential quality. From solar-constant measures, as set forth in the paper cited above as No. 27, the times of maxima and minima for solar radia- i \Z if — Fic. 14.—The 453-month period in solar variation. tion in the year 1938 are as follows (December, when given, is Decem- ber 1937) : Peto ie sites, oa6 6-1/30 9-7/10 114 13-1/10 Mascitnan sonics 4 January December-January September March Minimas eebian. se March April-June March June-July From figure 8, here, the times of maxima and minima for Fe in the year 1938 are as follows: Reriod ia54h2 4st: 6-1/30 9-7/10 114 10-1/10 Midsximalciinee sins March April January-April August AMA ic 2s a 20, gives pairs of determinations from Washington temperature records of 1854 to 1899 and 1900 to 1939, seks a Se : ( Gio ae Re Ae ann Ed ave TL BAY UREN ~~ ; = Z| Pid HL Re are Wa \ Vila nS Fics. 16 AND 17.—The periodicity of 13-6/10 months in Washington temperature departures. Ordinates in hundredths degree Fahr. The symbols O.K., v and *% indicate phase changes in getting means. respectively, for the three seasons January to April, May to August, and September to December, all adusted to a common phase and averaged. Figure 17 shows the same for sunspot numbers <20. It will be seen that the thick-lined mean curves for sunspot numbers => 20 are similar in form, but differ in phase, and have ranges of about 14° F. Figure 18 is a synthetic prediction, 50 years in advance, of the tem- perature of Washington, 1950 to 1952, based on 20 regular periodici- 30 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 ties determined from monthly records of the years 1854 to 1939, cen- tering about 1900. The prediction is in the thin line. The thick line is the event. The two scales of ordinates, separated 2° F., indicate, as expected, that Washington is now warmer than 50 years ago. I should add that all the data are smoothed by 5-month running means. The coefficient of correlation between forecast and event is 50.4 + 9.7 percent. Figure 19 shows the 454-month period, computed as a straight mean of all repetitions of that period, in precipitation records at Albany BRSEESae8n roo Ti cH BR SEPP SSR eS PROS Seos oF SSA eeae. |S SSS SSSR See eee eee Ue 8 eS eeeeeel TTT ae | Fad SER Re Bees 2X8 SP. eee eee !/ ARES Cees eee ae 1 | JS). - —_ 48h UBER EE. Wee ER ESE PEER eSee NORE ‘BES SR SEERERee Reese 4eee H+ aH +4 SS eee SERR ion VE! —-f {Ty} THEUREGRGRGRERUREGY 40 .we JORSEES Vea y A268! SRSSSERSS See 2B ae LAR, Se co NT Bene pry Pr SeeES0007 GEBBRE sass See ee as ss GEEGE BES RE ORS Pe Bee eRe See Pee RSS ae Sh OEE Al PARRReeScAPeoToaas lh RSe? AOR BEES ROSE See Pe ee Pe ee SER eR El PRs ee PAT eee Se Way 2 SSRs Ena! } I 9SgRseaapans ape PERS CRAs Ses | BSE GER ERS eee ee See eee eeUeea ae 8 6 ee ee Be eee Pee ee Pees Ue) eh See rj EaBSaasaeEsaSssasvae aasraazta Gs aerTaeeaerTeeaes eet tersees TosTeereee reeeeeras tT ceriatent fy is REBSeeeeo8 HEEEEEE EE EEE EE eee Nee RAR ete Vit y AN ff a Fic. 18.—Synthetic prediction, 50 years in advance of mean basis, and verification on Washington temperature. Computed from temperature records 1854 to 1939 with 20 regular ‘periodicities, all integral submultiples of 223 years. Correlation coefficient 50.42£0.7 percent. Forecast, lighter curve, right-hand scale. Event, heavy curve, left- hand scale. Temperatures Fahr., 5-month running means. over the interval of go years, 1850 to 1939. It carries several integrally related shorter periods on its back. The curves a and c represent the years 1850 to 1899, and 1900 to 1939, respectively. Being similar, and in the same phase, their average, b, is used in what follows. With- drawing the average period of 454+3 months, curve d results. Withdrawing from it the average period 4543~+4 months, curve e re- sults. Withdrawing from it the average period 45$~+5 months, curve f results. Withdrawing from it the average period 453~+2 months, curve g results. The smooth heavy curve is the 454-month period freed from all encumbrances. It has the amplitude 7 percent of normal precipitation at Albany. Figures 20 and 21, relating to the periodicity of 11 months in Albany precipitation, will be understood from the description just given of figures 16 and 17. The heavy mean generalized curves, for sunspots 2 20 Wolf numbers, are similar in form and amplitude, but tea ee Sh a eae cleared of over Albany precipitation, integral submultiples thereof. Fic. 19.—The 454-month periodicity in riding periodicities, 1 31 32 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 Figs. 20 (left) and 21 (right)—Fig. 20, combination of six separate determinations of the 113-month periodicity into one general mean, for times when Wolf sunspot num- bers exceed 20. Fig. 21, same as figure 20 for Wolf sunspot numbers less than 20. Full curves are originals, dotted curves with phases shifted as per arrows. NO. 4 SOLAR VARIATION, WEATHER ELEMENT—ABBOT 33 differ in phase. Their amplitude is about 9 percent of normal precipi- tation at Albany. Figure 22 shows predictions of precipitation at Albany for the years 1928 to 1931. The event is the heavy line. The dotted line is a predic- tion made wholly by synthesis from the forms and amplitudes of 22 regular periodicities determined from records of 1850 to 1899, center- ing about 1875. The correlation coefficient between this prediction and event is 44.0+9.5 percent. The light full line is synthesized from all records of 1850 to 1939, centering about 1900. I should add that in this precipitation work the monthly records are smoothed by 5-month running means. These forecasts may be claimed to be 55 and 30 years in advance, respectively, counting from the central years of their bases. I also computed the correlation coefficient for the light full line, repre- senting synthesis of averages of 22 periodicities, 1850 to 1939. It is 75.6+6.9 percent. If it be urged that this is not evidential, because 1930 lies within the go-year basis 1850 to 1939, I reply that only 41 months, January 1928 to May 1931, can be of direct influence, but 1,039 other months really control the prediction. SUMMARY I have sought to support, as a reasonable working hypothesis, the union of five propositions: 1. The sun’s output of general radiation is variable. 2. Solar variation has a master period of about 223 years. 3. Solar variation has numerous subordinate regular periodicities, all integrally related to 22? years. 4. Solar variation affects weather importantly, irrespective of periodicities. 5. Weather responds importantly to most of the regular periodic solar variations. This is a new, powerful element in meteor- ology. Each of these five conclusions is supported by correlations with several other classes of phenomena, as follows: Conclusion 1 : a. Areas of solar faculae. Prevalence of sunspots. Areas of solar flocculi. Incidence of great magnetic storms. Tonospheric changes. SERS eds “sia oF WOIJ stsayyUAs = dAInd poop AAvay ‘sivak 06 WoOIZ stsayjUAS = AND [INF ST * + poaresqo = dAIND [NJ AAvazy “AjAATIDodsat “66Q1 0} OSgI ‘savaX ob uo pue ‘6£61 0} OSgI ‘sivad 06 UO paseq Sat}oIporiad jo sasayyUAs 0} posedusos ‘1€61 0} gzOI ‘Aueq ry }e pedstasqo uorepdIV1g—ze “1 fo ‘AON ip fo oF we fp aD aah - Pi 9261, tae rs sVeaial se 2) 7 TE teas Pe ee PrN ea alee ee AY WT RSA PNT Tt TLE 4 | AT 34 NO. 4 SOLAR VARIATION, WEATHER ELEMENT—ABBOT 35 Conclusion 2: a. Solar-constant measures approximately repeated in form of march of variation after about 223 years. This period found in sunspot frequency. Also in magnetic condition of sunspots. Also in thickness of tree rings. e. Also in terrestrial temperatures. f,g-Also in terrestrial precipitation. aS Conclusion 3: a. Over 20 regular periods, submultiples of 223 years, found in solar-constant measures. b. The longer of these regular subperiods carry submultiple regu- lar periods upon themselves. c. Many of these submultiple periods are found in ionospheric changes. d. Analogy with sound harmonics leads us to expect many other integral subperiods, after three of them were independently discovered. Conclusion 4: a. West Indian hurricanes, a trigger effect of depressed solar constants. b. Very numerous temperature changes correlated to solar varia- tions. c. Numerous precipitation features repeated at 233-year inter- vals. Conclusion 5: a. Nearly all subperiodicities found in solar-constant measures are found strongly represented in temperature and precipi- tation. b. Syntheses of temperature and precipitation periodicities yield approximate march of observed weather. c. Forecasts 50 or more years in advance of mean years of bases, from such syntheses, yield tolerable accord with observed weather, with correlation coefficients from 5 to II times their probable errors. i eueas a in fh dae ately SMITHSONIAN MISCELLANEOUS COLLECTIONS VOLUME 122, NUMBER 5 SILVER DISK PYRMELIOMETRY. (WitTH 1 Pate) By W. H. HOOVER AND A. G. FROILAND Astrophysical Observatory Smithsonian Institution ows Up , THSONO*. 4: ny Cor 2° S2eceeeee® (PusLicaTion 4136) CITY OF WASHINGTON PUBLISHED BY THE SMITHSONIAN INSTITUTION AUGUST 4, 1953 The Lord Baltimore Dress BALTIMORE, MD., U. & A. SELVER-DISK PYRBELIOMETRY By W. H. HOOVER anv A. G. FROILAND Astrophysical Observatory, Smithsonian Institution (WitH 1 PLATE) In June and July 1932, Dr. C. G. Abbot and L. B. Aldrich com- pared silver-disk pyrheliometer S.I. 5yis with an improved form of the water-flow pyrheliometer.* The mean of 37 comparisons indicated the constant of S.I. 5pis should be 0.3625. The original constant of S.I. 5pis (0.3715) was determined by Dr. Abbot and W. H. Hoover in August 1931 by 24 comparisons with A.P.O. 8);;. Eight more comparisons in September 1932 by Aldrich and Hoover indicated the constant of S.I. 5nis should be 0.3718. Silver-disk pyrheliometer A.P.O. 8pis has been used since 1912 solely for standardization at Washington. Thus the scale of the Smithsonian revised scale of 1913 is too high by the ratio 0.3718 to 0.3625, or 1.0256—about 2.5 percent. The results of 42 more comparisons in July 1934 by the same ob- servers were in close agreement with the results of 1932. The mean value of the constant of S.I. 5pis in 1932 was 0.3625, and 0.3629 in 1934.” No comparisons were made between 1934 and 1947. In August 1947, 18 comparisons gave 0.3626 as the constant of S.I. 5nis.4 The results of the comparisons between silver-disk pyrheliometer S.I. Spis and the standard water-flow pyrheliometer No. 5 in 1932, 1934, and 1947 are based on Dr. Abbot’s habit of reading the silver-disk pyrheliometer. L. B. Aldrich made a few observations with S.I. 5n:; in 1932. Since there is a small personal equation in reading the silver-disk pyrheliometer more comparisons were made in 1952 between S.I. 5pis and the standard water-flow instrument No. 5. The results of 1 Smithsonian Misc. Coll., vol. 87, No. 15, 1932. 2 Smithsonian Misc. Coll., vol. 92, No. 13, 1934. 8 Smithsonian Misc. Coll., vol. 110, No. 5, 1948. SMITHSONIAN MISCELLANEOUS COLLECTIONS, VOL. 122, NO. 5 2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 1952 are based on A. G. Froiland’s habit of reading the silver-disk pyrheliometer. In order to insure comparable results with the water- flow pyrheliometer no changes were made in the instrument. Figure 1, A, B, and C, shows the instrument in some detail. The two chambers a b c and a’ b’ c’ are almost exactly the same in all de- tails. The distilled water enters at d and divides into two streams at : TT LOLELLLE Fic. 1.—Standard water-flow pyrheliometer. e and e’. The water flows around the receiver at d and d’ and out of the instrument at 7 and j’. 7 and 7’ are the thermoelectric junctions used to determine the equality of temperature of the water streams outflowing from the two chambers. m is the water bath for the two receivers, water entering at p and being discharged at 0. is a wooden case surrounding the instrument. The heating coils are indicated by k and k’. Not shown is a shutter for alternating the chambers ex- posed to solar and electric heating. A detailed description of one of the receivers is given in volume 3 of the Annals of the Astrophysical Observatory. In order to keep the water bath surrounding the two receivers and the distilled water entering the instrument at the same temperature, we used a 50-gallon drum of water as a source of water for the water NO. 5 SILVER-DISK PYRHELIOMETRY—HOOVER AND FROILAND 3 bath. A circulating pump continually stirred the water in the drum and a bypass on the pump circulated some of the water through the water bath. The distilled water flowed through a coil in the drum before entering the instrument. Thus the bath water and the distilled water were always at the same temperature when leaving the drum. All the precautions that were taken in 1932, 1934, and 1937 to in- sure greater accuracy were again taken in the present comparisons. In addition, we found it very important to have the rate of flow of water in the two receivers as near the same as possible. The water entering the receivers may not be at exactly the same temperature as the water bath around the receivers, thus any change in the tempera- ture difference would produce a drift of the galvanometer. In order to get the flow of water the same in the two circuits, we exposed both receivers to solar radiation and adjusted the flow of water until the galvanometer remained at the open circuit zero. Thus the two streams of water were at the same temperature and since they were both receiving the same amount of heat the rate of flow should be the same. Water currents of approximately 50 cubic centimeters per minute in each branch of the pyrheliometer were found to give good results, but rates as low as 35 and as high as 65 cubic centimeters per minute were used without affecting the results. Temperature of the water bath varied from 23° to 28° C. on different days. Table 1 gives the results of the comparisons. The mean of 100 observations gives 0.3622 as the constant of S.I. 5yi;. The average deviation from the mean is 0.27 percent and the maximum devia- tion from the mean about 0.9 percent. The above value is about .13 percent lower than the mean of the previous values. TABLE I1.—Summary of 1952 comparisons Calories Corrected Constant by reading of of Deviation Date water-flow silver-disk silver-disk from 1952 Time No. 5 S.-I. Neo 551. SL. Nowsir. mean Sept. 28 8: 38 1.368 3-775 3624 + 2 44 1.376 3.7900 3630 + 8 50 1.380 3.700 3636 + 14 56 1.388 3.847 3609 — 13 9:05 1.400 3.877 3011 — II II 1.411 3.889 .3627 + £5 y/ 1.413 3.895 3628 + 6 23 1.412 3.906 3016 — 6 29 1.418 3.931 3608 —I4 35 1.428 3.951 3014 — 8 (continued) 4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 TABLE 1.—Summary of 1952 comparisons (continued) Calories Corrected Constant y reading of of Deviation Date water-flow silver-disk silver-disk from 1952 Time 0.5 I. No. 5i:5 alONOsS se mean Sept. 29 Q:22 1.405 3.861 3638 + 16 28 1.410 3.879 3638 + 16 34 1.407 3.894 .3613 =e 40 1.408 3.809 3012 — 10 46 1.415 3.918 3011 —IlI 52 1.419 3.937 -3604 — 18 58 1.425 3.947 .3609 a 10: 04 1.434 3.944 .3635 + 13 10 1.445 3.975 .3635 is II: 14 1.447 3.986 3630 + 8 20 1.454 4.018 3620 — 2 26 1.462 4.015 .3041 + 19 32 1.461 4.011 3042 + 20 38 1.458 4.022 3624 + 2 44 1.466 4.027 3640 + 18 50 1.454 3.996 .3639 + 17 56 1.464 4.025 .3637 +15 12:02 1.454 4.005 -3629 + 7 08 1.464 4.013 -3649 + 27 14 1.457 4.004 -3639 Sa Sept. 30 0:44 1.423 3.922 3628 + 6 50 1.421 3.930 36017 — 5 56 1.430 3.961 3010 —I2 10: 02 1.431 3.949 3624 + 2 08 1.426 3.045 3013 — 9 14 1.430 3.959 3611 —II 20 1.433 3-990 .3501 — 31 26 1.446 3.988 3026 + 4 32 1.438 3.998 .3596 —26 38 1.454 4.013 3023 + I Oct. I TDs 0r 1.446 3.990 3625 + 3 17 1.453 4.027 .3607 — 15 23 1.458 4.029 .3620 — 2 29 1.458 4.020 3628 + 6 35 1.458 4.029 .3619 — 41 1.457 4.008 -3635 + 13 47 1.454 4.018 .3617 = 5 53 1.469 4.058 3621 — I 59 1.472 4.058 .3627 + 5 12:05 1.472 4.067 3621 — I 13 1.463 4.054 3610 —iI12 19 1.458 4.023 3623 + I 25 1.461 4.048 3009 — 13 31 1.465 4.037 3628 + 6 37 1.447 3.994 .3623 ae 43 1.451 4.007 3021 — I (continued ) NO. 5 Och 11 SILVER-DISK PYRHELIOMETRY—HOOVER AND FROILAND TABLE 1.—Summary of 1952 comparisons (concluded) 10: 10 12: 10: Mean of 100 observations (6 days) Average deviation 42 Calories b by water-flow No. 5 1.445 1.427 1.418 1.427 1.447 1.450 1.463 1.465 1.478 1.479 1.494 1.492 1.406 1.506 1.516 1.526 1.530 1.534 1.543 1.550 1.548 1.549 1.551 1.548 1.554 1.557 1.558 1.558 1.558 1.548 1.553 1.546 1.546 1.540 1.530 1.535 1.537 1.541 1.545 1.549 1.548 1.539 1.540 1.543 Corrected reading of silver-disk TE. No. Shi 3.980 3.947 3.878 3.918 3-971 3-995 4.050 4.053 4.065 4.087 4.123 4.119 4.150 4.166 4.196 4.235 4.242 4.245 4.265 4.276 4.276 4.276 4.291 4.291 4.290 4.305 4.311 4.311 4.311 4.291 4.207 4.277 4.296 4.241 4.224 4.226 4.218 4.240 4.250 4.276 4.276 4.241 4.251 4.261 Constant oO silver-disk PDN: Shite 3631 3616 .3657 3042 .36.44 3030 3613 3014 .3635 3019 3023 3023 3604 3016 3012 3604 .3007 3015 36017 3625 .3620 3023 3614 3607 3623 3616 3613 .3614 3613 .3607 3014 36015 3599 3032 3622 3032 -3645 -3635 3636 3023 3019 5 Deviation = ol N Om 0 OO DH tNM Or NW U1 6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, \i22 ae Mat 3g /is- TT 5 hs SAA LIZ. fer 7~10.iP PAE ae 10:01/a 0 20% ML & 2 F AP 32 7 Bago ve OTT T rch d 33] 27227 ies 3325 538 as aS 230% 423 vf S950 SPAS ws ¥ [3224 5935, Ge rr WZ (3163 gu! 33560 3 3ENN4 6.76 Ee pe ee gs Wee 96.97) ae 34-77?~ 99 SPO) —795— PIC 1S) 339 GALLO 4b/07/20 AenbeFO zs ‘ oa ——— 40 -_—/- airy tbe syy 43364 c ie See ee Re Ae ae eee) map ee ee sree oe 4 - SHE o ye G3e7 it iy wie, #9 3e we Gris 7 a wage IZ ee Ge 36.357 3 42% - Po) . . 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Cats a7 : 3667 Wo 3799 ee 3S I2.5°3 DIS IYSS -IS 3 276 J3 3h a1 e gees : 407 nO ° pee ae of? 149 e ~/-2i0 ss -0F EES Ew) bee eae NC ee > — 33/7 ” : 330s or Wb”, Tag) Viens = Jeera "ee ED Pa: d 262, ac fi we. ugase we G Y 40 ¢ c 260 39, 6 Js 170 3ot/ aE oo 2 GPE a xe aealre Co eee 357 5/ Ee Sos 3 fee = ae oe ipl! 3Y37_ NSH ,, -3/ i pee Luger . FIF/LO —— ae TIA O i IZ 3S- aoe = —ttg qe F22€ 12G ‘e 2V-60 ees Ly (22 7 =} = bad Deve iz, w ‘ f 34.09 1) jaye 2 aay 3 Gi20 Ft SSIS 42 26.47 pubes 22.95 -493 as 2 ea Fic. 2—Photographic copy of Froiland’s original reading of the silver-disk pyrheliometer. SMITHSONIAN MISCELLANEOUS COLLECTIONS VOLE. 1227 (NO! 5, PL. 2 STANDARD WATER-FLOW PYRHELIOMETER AS MOUNTED AT TABLE MOUNTAIN, CALIF. NO. 5 SILVER-DISK PYRHELIOMETRY—-HOOVER AND FROILAND 7 Figure 2 is a photographic copy of A. G. Froiland’s original read- ings of the silver-disk pyrheliometer S.I. 5nis on September 29, 1952. A summary of all the comparisons between S.I. 5pis and standard water-flow No. 5 is given below: No. of values Date Mean constant S.I. 5), 37 1932 .3625 42 1934 .3629 18 1947 3626 100 1952 3022 The variations in the above results are probably within the limit of error of the observations; thus we may assume the constant of S.I. 5nis has remained constant since 1932. The constant of S.I. 5yis, as detemined by 32 comparisons with the standard silver-disk pyrheliometer A.P.O. 8pis in 1931 and 1932, was 0.3718. The mean of 64 comparisons with A.P.O. 8pis just before S.I. 5nis was carried to Table Mountain, Calif., and 64 comparisons just after its return to Washington gave exactly the same constant. The mean of all good comparisons between S.I. 5pis and A.P.O. 8nis from I93I to 1953 gives 0.3719 as the constant of S.I. 5pis. This would indicate that A.P.O. 8,:, has remained unchanged since 1932. The mean of all the above results would indicate that the scale of Smithsonian revised pyrheliometry of 1913 is very nearly 2.5 percent too high. SOME EXPERIMENTS WITH THE SILVER-DISK PYRHELIOMETER In the following series of experiments with the silver-disk pyr- heliometer the source of radiation was a 100-watt microscope lamp. An enlarged image of the filament was focused on the silver disk by means of a lens and the voltage on the lamp maintained constant with a voltage regulator. Silver-disk pyrheliometer S.I. 5pis was used in most of the tests. A DETERMINATION OF THE CONSTANT K A correction is added to the reading of the silver-disk pyrheliometer which depends upon the mean bulb temperature while exposed to radiation. The correction is [K(7-30°)] R where T is the mean bulb temperature, the rise in temperature in 100 seconds plus the cooling corrections, and K is a constant. The value of K in use is 0.0011. This value was determined experimentally, using two silver- 8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 disk pyrheliometers.* The present determination was made with one pyrheliometer. In this experiment and all the following experiments the lamp was turned on about an hour before making a series of readings. The lamp was very constant during a day’s observations and changed very little from day to day. In one set of observations the following results were obtained: The mean of 18 observations at a mean bulb temperature of 34.°21 was 3.388, and a mean of 12 observations at a mean bulb temperature of 21.66 was 3.435. The above readings represent the rise in tem- perature of the silver disk with all corrections applied with the ex- ception of the one depending on the mean bulb temperature. If this correction is applied, the two values should be the same. Thus 3.388+ [4.21 K (3.388) ] =3.435+[—8.34 K (3.435)], or K is equal to 0.001095. Other determinations of K with various temperature differ- ences gave results of K between 0.00104 and 0.00118, with a mean value approximately 0.0011. One set of observations made with pyr- heliometer S.I. 89 gave 0.00109. Some of the determinations of K were made with the pyrheliometer in a water-cooled chamber with a hole in one end to admit the radiation and a slot along one side to read the thermometer. Also an automatic shutter opening and closing device was used for some of the work. In any set of observations individual values were within +0.3 percent of the mean. SERIES OF OBSERVATIONS IN WHICH THE COOLING CORRECTION DURING THE FIRST IOO SECONDS IS ZERO OR NEAR ZERO In making a series of readings it has been our practice to start read- ings 20 seconds after completing an observation. Thus a 4-minute shaded period occurs between each 2 minutes of exposure. Each value is independent and the total rise in temperature of the silver disk is much less than the rise in temperature of the silver disk with only a 2-minute shaded period between each 2-minute exposure. In the following experiment sets of six readings each were taken and for each set the cooling correction for the first 100 seconds of the first reading was zero or near zero. Sets of readings were made at different temperatures and some were made with the automatic shutter opening and closing device. After the fifth reading the mean 4 Smithsonian Misc. Coll., vol. 95, No. 23, 1937. NO. 5 SILVER-DISK PYRHELIOMETRY—HOOVER AND FROILAND 9 bulb temperature and the cooling correction remained about constant. The mean of 30 sets is given below: INoMotereadinges. vasa sleet. I 2 3 4 5 6 Corrected reading ..... 3.202 3.206 3.208 3.210 3.211 3.212 The above indicates some increase in the reading from 1 to 6. The change is small, however, after the second reading. This fact was noted about 20 years ago, when many comparisons were being made between the silver-disk and the Angstrém pyrheliometers. Since that time, when using the silver-disk pyrheliometer, we have preheated the silver disk from one to three minutes before starting a series of readings. Series of readings taken after the silver disk was preheated gave very consistent readings. Some of the discrepancy in the read- ings shown above may be due to a delay in opening and closing the shutter or a time lag in reading the thermometer. The rate of move- ment of the mercury thread is different in the first two or three read- ings of a set from that in later readings of the set when the rate of heating and cooling remain about constant. EFFECT OF DELAY IN OPENING AND CLOSING SHUTTER A set of readings were made using the regular method of opening and closing the shutter and then a set in which there was a delay of Io seconds in opening the shutter after the end of a shaded period and a delay of 10 seconds in closing the shutter after an exposure period. The results in the latter case were about 3 percent higher. Thus a delay in opening and closing the shutter of even one second may result in an error of 0.3 percent. Variation in the time of open- ing and closing the shutter may explain the variation of the results with the silver-disk pyrheliometer by different observers. The pyrheliome- ter readings in this series of tests were made by L. B. Aldrich and W. H. Hoover. With the regular method of reading the pyrheliome- ter and the shutter operated by hand there was a difference of about 0.2 percent between the readings of the two observers. When the automatic shutter-opening device was used this difference was re- duced to 0.1 percent or less. EFFECT ON THE PYRHELIOMETER READINGS WHEN READINGS ARE TAKEN BEFORE THE PYRHELIOMETER CHANGES TO AMBIENT TEMPERATURE For this test the pyrheliometer was placed in the chamber of the water bath and the automatic shutter device was used when readings Io SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, I22 were made. With the water bath at 15° and the pyrheliometer at the same temperature, a few readings were made with the bath maintained at 15°. The temperature of the bath water was then changed to about 35° and readings made while the pyrheliometer was changing tem- perature. The first three readings were from 0.5 to 0.7 percent too high. When the pyrheliometer was about 5° below the temperature of the bath more readings were taken. These readings agreed with the original set of readings. These results indicate that the pyr- heliometer should be near the ambient temperature before making an observation. In a paper on the Abbot silver-disk pyrheliometer ° L. B. Aldrich discussed in some detail the method of observing with the silver-disk pyrheliometer and listed some precautions to be taken to insure greater accuracy. One precaution should be added. The shutter should be opened immediately at the end of the first shaded period and closed immediately after the end of the exposed period. A delay of a few seconds may result in an error of I percent or more. 5 Smithsonian Misc. Coll., vol. 111, No. 14, 1940. "SMITHSONIAN MISCELLANEOUS COLLECTIONS pVOEUME 122, NUMBER 6 || THE EXTERNAL MORPHOLOGY OF THE DRAGONFLY ONYCHOGOMPHUS ~ARDENS NEEDHAM BY HSIU-FU CHAO Department of Entomology University of Massachusetts > ON i abet Ty (Pusication 4137) , CITY OF WASHINGTON PUBLISHED BY THE SMITHSONIAN INSTITUTION SEPTEMBER 15, 1953 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOLUME 122, NUMBER 6 fae EXTERNAL MORPHOLOGY OF THE DRAGONFLY ONYCHOGOMPHUS ARDENS NEEDHAM BY HSIU-FU CHAO Department of Entomology University of Massachusetts (PuBLIcATION 4137) CITY OF WASHINGTON PUBLISHED BY THE SMITHSONIAN INSTITUTION SEPTEMBER 15, 1953 TBe Lord Baltimore Press BALTIMORE, MD., U. 8 A. the EXTERNAL MORPHOLOGY OF THE DRAGONFLY ONYCHOGOMPHUS ARDENS NEEDHAM * By HSIU-FU CHAO 2 Department of Entomology, University of Massachusetts In 1917 Tillyard brought together all the scattered information re- garding the morphology as well as other biological studies of dragon- flies in a book entitled “The Biology of Dragonflies.’ His discussion of morphology in this book was based on the writings of previous workers who were mainly interested in comparative studies of certain organs. Since this date some morphological characters have been fur- ther and well investigated, but other structures remain inadequately studied. Furthermore, entomologists working on dragonflies have paid little attention to the new interpretations given by Ferris and Penne- baker (1939), Ferris (1940), Snodgrass (1947), and others on the fundamental structures of certain parts of the body of insects in gen- eral. There is not a single species of dragonfly that has been studied critically in the light of the most recent morphological interpretations. The purpose of the present study is fourfold: (1) To bring into unity all the different terminologies that have been used in morpho- logical and taxonomic work on dragonflies; (2) to apply the knowl- edge of the most recent morphological interpretations; (3) to bring out some new interpretations of morphological characters that the author believes to be inadequately or erroneously treated previously ; and (4) to serve as a contribution to the morphology of dragonflies, especially as a foundation for future taxonomic studies. Onychogomphus ardens Needham (Gomphidae) has been selected for study for three reasons: (1) It belongs to the primitive family Gomphidae of the order Odonata. This family is well represented by genera and species in my own collection, which will be used for 1 Contribution from the Department of Entomology, University of Massa- chusetts, Amherst, Mass. 2 The author wishes to express his appreciation for the help and advice re- ceived from staff members at the University of Massachusetts. Sincere thanks and appreciation are likewise extended to coworkers throughout the world who have encouraged and helped the author during the progress of this work. SMITHSONIAN MISCELLANEOUS COLLECTIONS, VOL. 122, NO. 6 2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 future taxonomic studies. (2) Specimens of this species are of large size and therefore relatively easy to study. (3) It is rather common in South China. HEAD (Figures 1-6) The head of Onychogomphus ardens Needham is hypognathous and somewhat anteroposteriorly flattened, the anterior aspect being convex and the posterior aspect being concave. Posteriorly it is attached to a narrow neck. The female differs from the male in having a pair of occipital horns (fig. 2: OCCH) on the occipital margin. The areas generally referred to as frons, vertex, and occiput by earlier workers are designated as such in this paper. No attempt has been made to change their names, although they have been interpreted differently by modern morphologists (DuPorte, 1946; Snodgrass, 1947). The old designations are used here without modification to avoid further confusion in taxonomic work. SUTURES OF THE CRANIUM OR CAPSULE The principal sutures of the cranium are postocellar, epistomal, subgenal, ocular, parafrontal, postoccipital, and clypeal sutures. The POSTOCELLAR SUTURE (POS) is a transverse suture which separates the vertex from the occiput. It lies between the two com- pound eyes at their closest points. According to Lew (1933) this suture is secondarily developed and is not homologous with the epi- cranial suture (e.g., Garman, 1927) of other insects. This suture is designated by Lew as postocular suture ; but unfortunately in the same paper he created another term, postocellar suture, evidently referring to the same structure. The latter term is probably the one he meant to use, while the former term might be a typographical error, since it is definitely not descriptive of its position. Snodgrass (1947), how- ever, mentioned “The cleavage line on the head of larval Odonata is characteristically T-shaped rather than Y-shaped, inasmuch as the frontal arms usually go almost straight laterally.” In the present species the postocellar suture represents the transverse bar of the T and therefore corresponds to the frontal arms. The EPISTOMAL SUTURE (ESS), or frontoclypeal suture, is a distinct and almost straight line across the anterior part of the cranium. Along this suture a strong epistomal ridge (ESR) is produced internally. Each of the SUBGENAL SUTURES consists of two portions, the pleu- rostomal and hypostomal sutures. The pleurostomal suture (PMS) LATERAL VIEW TENTORIUM, 5) TENTORIUM, VENTRAL VEW LATERAL VIEW Fics. 1-6.—Head. 4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I22 marks the lateroventral margin of the capsule above the mandibular bases and between the anterior (AAR) and posterior articulations (CAR) of each. Along this suture the anterior tentorial arm (ATA) is produced internally, and to it a narrow sclerite, the pleurostoma (PM), is attached. The poorly defined hypostomal sutures (HMS) each follows closely the posterior margin of the cranium between the posterior articulation of the mandible (CAR) and the posterior ten- torial pit (PTP). The oCULAR SUTURES (OS) surround the bases of each of the com- pound eyes except in the anterior aspect of the head where a narrow band of sclerite, the ocular sclerite (OCS), is interposed between them. PARAFRONTAL SUTURES (PFS) are present, one on each side of the frons. Apparently no name has previously been given to them although they are shown in many drawings of various species of dragonflies by different authors (e.g., Tillyard, 1926; Lew, 1933). These are probably the frontogenal sulcus of DuPorte (1946) or lateral grooves of Snodgrass (1947). Each suture extends from the middle of the inner margin of the eye near the antenna to the anterior articulation of the mandible, thus separating frons from gena. Each is hidden by the lateral portion of the elevated frons and clypeus and therefore is invisible in the anterior aspect of the head. Along this suture a low ridge is produced internally. The PosToccIPITAL SUTURE (POCS) closely parallels the dorsal and lateral margins of the foramen magnum (FM). The CLYPEAL SUTURE is absent, but its position is indicated by a distinct line of demarcation between the sclerotized postclypeus and the mostly membranous anteclypeus. The antennal socket is well defined but is not circumscribed by an antennal suture. AREAS OF THE CRANIUM The principal areas of the cranium are clypeus, frons, vertex, occiput, genae, postgenae, postocciput, pleurostomae, hypostomae, and eyes. The gula is absent in this species. However, it has been very vaguely indicated as being present in the order Odonata by earlier workers. Calvert (1893) said that the gula was membranous; Till- yard (1917) probably concurred with him in this matter. Marshall (1914) probably wrongly designated submentum as gula. The cLYPEus is a large transverse sclerite differentiated into a light- colored, mostly membranous anteclypeus and black-colored, sclerotized postclypeus. The latter areas are separated by deep indentations on No. 6 MORPHOLOGY OF THE DRAGONFLY—CHAO 5 both sides. The anteclypeus (ACL) is light-colored, laterally produced into a lobelike structure, with a narrow sclerotized piece on each side extending mesally from the tip of the lobe a distance of one-third the width of the anteclypeus. The postclypeus (PCL) is black, with or without a small transverse light-colored spot on each side. It expands laterally and extends ventrally, thus overlapping a portion of the lateral lobe of the anteclypeus. A small condyle, the anterior articula- tion of mandible (AAR), is produced on each side near the base of the postclypeus. It is covered by the laterally expanded portion of the postclypeus so that it cannot be seen in the anterior aspect of the head. The Frons (FR) is a large, transverse, convex area which is bounded ventrally by the epistomal suture, laterally by the parafrontal sutures, and dorsally by a transverse furrow between it and the vertex. It is differentiated by a sharp fold into an upper horizontal portion and an anterior or vertical portion, but there is no sutural demarcation between these regions. The upper portion is called the top of frons (TFR) which is differentiated into two low prominences separated by a broad median furrow. A broad, transverse, light-colored stripe covers most of the top as well as a part of the anterior portion of the frons. This stripe is sometimes separated in the middle along the median furrow. In this light-colored area there are a few small black tubercles each of which bears a minute hair. The vERTEX (V) is a trapezoidal area bounded ventrally by a groove between it and the frons, dorsally by the postocellar suture, and laterally by the ocular sutures. It bears a pair of antennae and three ocelli (OC), the latter being very large. The deeply sunken middle ocellus is a little lower in position than the lateral ocelli. Along the dorsal rim of the middle ocellus there is a very low but large knoblike tubercle which bears a group of fine and wavy long hairs. External to the tubercle and the lateral ocellus there is a subsemicircular ridge. The dorsal tentorial pits (DTP) are present as a pair of semicircular sutures above and lateral to the bases of the antennae (mostly obscured by the antennae in anterior view and by the eye in lateral view). It is interesting to point out here that the dorsal tentorial pits are present in the adult dragonflies (Lew, 1933) whereas they are usually repre- sented by a pair of callosities in the dragonfly nymphs and many in- sects. Two peculiar papillae (PA), about two-thirds as long as the third antennal segment, situated one on each side very close to the external rim of the antennal socket, are present in both sexes. They are small and usually obscured from view by the antennae and there- fore are easily overlooked. Apparently they have not been reported 6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 heretofore. They occur also in Onychogomphus micans Needham which is very closely related to the present species, but not in Jctino- gomphus rapax (Rambur) (Gomphidae) and Anax nigrofasciatus Oguma (Aeschnidae) which I have examined. The furrow which separates the frons from the vertex is called frontal furrow or frontal suture by Tillyard (1917). These terms are confusing since the structures they define are definitely not homologous with the frontal sutures of other insects. Morphologically speaking (DuPorte, 1946; Snodgrass, 1947), the areas of the frons, vertex, and occiput described here are not homologous with those of other insects or even with these areas as designated in certain other species of dragonflies, although they are generally so considered by students of Odonata. The occiput (OCC) is situated on the top of the head between the compound eyes. In the anterior aspect of the head it appears as a transverse area bounded ventrally by the postocellar suture, laterally by the compound eyes, and dorsally by the occipital border, or occipi- tal margin (OCCM), which is almost twice as wide as the postocellar suture, and fringed with long black hairs. In the female there is a pair of occipital horns (OCCH) on the occipital margin. These are not to be confused with a pair of similar horns which arise on the vertex above the lateral ocelli and which are also, but erroneously, called the occipital horns. Such horns occur in a number of species of the family Gomphidae, e.g., Gomphus flavicornis Needham (Lew, 1933, pl. 8, fig. 9), Gomphus cuneatus Needham, and Davidius bi- cornutus Selys. The posterior aspect of the occipital region is called the rear of the occiput (ROCC). It is a subquadrate area situated above the foramen magnum, with a large, light, yellow-colored mark- ing in the center. Laterally it is demarked with weakly defined fur- rows or wrinkles which indicate the dividing line between it and the postgenae. The GENAE (G) are small sclerites. Dorsally each gena is bounded by the parafrontal and the ocular sutures, and ventrally to its evagi- nated margin is attached a small transverse sclerite, the plewrostoma (PM). The postGENAE (PG) area pair of large sclerites, one on each side of the posterior aspect of the head. The outer margin of each postgena which borders the eye is notched at about the center. Mesally and mesoventrally the postgena is bounded by the postoccipital suture and hypostomal suture respectively. Ventrally it is fused with the gena. This fused portion bears the posterior articulation of the mandible. The postocciput (POOC) is a roughly horseshoe-shaped narrow No. 6 MORPHOLOGY OF THE DRAGONFLY—CHAO Ff sclerite surrounding the dorsal and lateral sides of the foramen mag- num, with its ends terminating at the posterior tentorial pits (PTP) where a pair of small transverse processes, the occipital condyles (OCCD), are produced toward each other. On each side of the fora- men magnum the postocciput is produced mesally into a short process. The PLEUROSTOMAE (PM) are very small transverse sclerites, one on each side, situated in the evaginated ventral margin of the gena between the anterior and the posterior mandibular articulations. The HyposToMAE (HM) are narrow bands or thickenings, one on each side bordering the lower margin of the postgena between the posterior articulation of the mandible and the posterior tentorial pit. The compouNp EYES (EYE) are large, and are closest together along the postocellar suture. Each is evaginated in the middle on its posterior margin as shown in figures 4 and 5. TENTORIUM (Figures 4-6) The tentorium consists of a corporotentorium and three pairs of tentorial arms, namely, dorsal, anterior, and posterior. The CORPOROTENTORIUM (CT), or tentorial body, is a transverse bar very close to the posterior surface of the head capsule and appear- ing as the floor of the foramen magnum. Apparently it is often mis- taken for the gula by some students of Odonata. The POSTERIOR TENTORIAL ARMS (PTA) arising from distinct posterior tentorial pits (PTP) are very short and are not differentiated from the corporotentorium. The ANTERIOR TENTORIAL ARMS (ATA) arise from extremely elon- gated tentorial pits lying along the entire lengths of the pleurostomal sutures. Each anterior tentorial arm is a fanlike structure strength- ened by three heavily sclerotized ribs radiating from the corporoten- torium. The posterior rib (PRB) extends to the posterior mandibular articulation, the middle rib (MRB) to the anterior mandibular articu- lation, and the anterior rib (ARB) to the lateral end of the epistomal ridge. On the ventral surface of the middle rib there are two proc- esses: the anterior process is called the mandibular process (MDP) and consists of a very large, ovoid, tendonlike structure with a short, narrow stalk. The large ovoid portion is inserted in the heavy muscles of the mandible. The posterior process is called the maxillary process (MXP) and is a long and slender tendon supplying attachment for the maxillary abductor muscles. On the posterior rib there is also a short process. 8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 Each of the DoRSAL TENTORIAL ARMS (DTA) consists of a simple flattened structure arising from the middle rib of the anterior tentorial arm. Each narrows slightly in the middle and is apically fused firmly with the invagination of the dorsal tentorial pit. HEAD APPENDAGES (Figures 7-16) The movable parts of the head are the antennae, labrum, mandibles, maxillae, hypopharynx, and labium. The ANTENNAE (ANT) are short, inconspicuous, setaceous, and 4-segmented. The basal segment, or scape (S), is very thick. The second segment, or pedicel (P), is subequal in length and about half the diameter of the preceding segment. The third and the last seg- ments are collectively called the flagellum (FL), or distalia, which is slender and bristle-like; the third segment being about two-thirds as long as the pedicel ; the last segment being longer than the other three segments combined. The rasrum (LR), or upper lip, is a transverse subovoid sclerite, movably attached to the anteclypeus and functions as one of the mouth parts. It is generally regarded as not a true appendage. Great differ- ences of opinion exist among entomologists as to its homology. For more detailed accounts the reader is referred to recent papers by Ferris (1947) and Henry (1948). Aborally (fig. 7) it is slightly convex, black, with two large ovoid yellow spots, and fringed with many long hairs along its distal and lateral margins. Adorally (fig. 8) it has a flat surface, is black on lateral regions, and has a large clear area called the epipharynx in middle. The epipharynx (EPX) con- sists of a round, slightly depressed, sclerotized area in the center surrounded by a group of small circular tubercles and hairs. These tubercles are probably taste organs. Some hairs are grouped together to form the brushes (BH) pointing mesad. The mandibles (MD) are very strong unsegmented appendages bearing strong teeth which may be divided into two groups: a large basal mola (MO) and a distal group of three incisors (ICS). The base of the mandible is triangular in shape, with one lateral and two mesal angles. The mesal angles are designated as inner and outer. The mandible is attached to the head capsule by two articulations, the ginglymoid anterior articulation (AAR) at the outer angle and the condylic posterior articulation (CAR) at the lateral angle. A strong flexor tendon (FT) is attached to the inner angle and a weak re- tractor tendon (RT) to the lateral angle. No. 6 MORPHOLOGY OF THE DRAGONFLY—CHAO 9 The adoral side (fig. 10) of the mandible has two tuberculate and hairy areas, one at the base of the incisors and the other parallel to the margin of the mola, the former area being crescent-shaped. The aboral side (fig. 9) of the mandible has a similar crescent-shaped, tuberculate, and hairy area which is slightly depressed and joins with a ridge extending to the anterior articulation. The three incisors (ICS) are of unequal length; one of them being very long, sharply pointed, slightly curved, and bearing the smaller basal one on its mesal edge and an even still smaller medial one on its adoral side. The mola (MO) has four cusps set on a broad base in the shape of a Z on the right mandible and inverted Z (X) on the left mandible. The cusps are placed one at each end and one at each angle of the Z. The MAXILLAE are composed of several parts, namely, cardo, stipes, inner lobe, and outer lobe. The cardo is an elongate structure internally strengthened by an X-shaped ridge, the mesal arms of the X being submarginal and the lateral arms marginal. It is divided into basicardo (BCD) and disti- cardo (DCD) by a suture which is situated along the lateral margin of the basolateral arm and the mesal margin of the distomesal arm. The concave area of the basicardo between the basal arms is about two-thirds as large as the weakly sclerotized convex area of the disti- cardo between the distal arms; the latter area being adorned with a few long hairs. The stipes (STI) is a large elongate rectangular structure adorned laterally with many short hairs on its inflected area and apically with many long hairs. A mesal submarginal sutural groove (SG) (Snod- grass, 1935) sets off a narrow area called parastipes (SG) (Cramp- ton, 1923b, p. 83). An isolated sclerite is present in the membrane which attaches along the margin of the lateral inflected area. Nothing is known about this sclerite although it has been shown in drawings by earlier workers (e.g., Tillyard, 1917, p. 16, fig. 4). The inner lobe (IL) and the outer lobe (OL) are two freely mov- able processes, the former being generally regarded as representing the fused Jacinia and galea of more typical mandibulate insects, and the latter the palp. The inner lobe (IL) is a large process basally fused with the stipes but separated from the parastipes by a narrow strip of membrane. Basally it is expanded on its mesal portion and adorned with many long hairs. Apically it is narrowed and gently curved, ending in three teeth pointing mesad, the apical tooth being very long and the middle one the smallest. The weakly sclerotized area along the mesal margin IO SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 of the apical half of the inner lobe bears three widely spaced teeth of subequal length, also pointing mesad. ae HYPOPHARYNX Fics. 7-12,—Mouth parts. 7, 9, and 11, Aboral views; 8, 10, and 12, adoral views. The outer lobe (OL) is a stout, slightly curved, fingerlike structure, about as long as the inner lobe, with the lateral portion of the basal half weakly sclerotized and unpigmented. Basally it is situated on a small transverse sclerite on the adoral side of the maxilla. No. 6 MORPHOLOGY OF THE DRAGONFLY—CHAO II The HYPOPHARNYX is a large, elongate, wedge-shaped lobe in the preoral cavity, apparently consisting only of the lingua, with its aboral surface (fig. 11) about half as long as its adoral surface (fig. 12), its lateral sides slightly divergent, and its apical margin slightly emarginate. Adorally (fig. 12) the hypopharynx is adorned with hairs. Those hairs along the distal margins and surrounding the subapical, de- pressed, sclerotized area are very long and widely spaced. Basally the hypopharynx has a heavily sclerotized transverse bar which is fused laterally with a pair of slightly raised sclerotic structures im- mediately distal to it ; the former with a low, transverse internal ridge, and the latter with a number of small round nodules. A single trans- verse, raised, somewhat wrinkled, weakly sclerotized structure, and a pair of similar smaller ones are situated distal and lateral to the sclerotized structures respectively. Aborally (fig. 11) the lateral walls of the hypopharynx contain a pair of basal plates, the apical ends of which are attenuate, whereas the basal ends expand and extend along the basal margin of the hypo- pharynx to the salivarium (SAL). The Lazium consists of the following movable parts: Submentum, mentum, middle lobe, squames, lateral lobes, and movable lobes. The submentum (SM) is a quadrangular piece with its basal margin slightly evaginated and its lateral edges subparallel to each other. Basally it is bounded by membrane continuous with the neck region. Laterally and adorally it is connected with the mesal margins of the cardines and stipites of the maxillae and with the base of the hypo- pharnyx by a large membrane. The mentum (MN) is a transverse area. Adorally (fig. 16) it is partly membranous, with a pair of large transverse subrectangular sclerites imbedded in the membrane. These sclerites are adorned with long hairs on their bulging lateral portions. Apically the mentum is separated from the middle lobe by a distinct membranous fold. Aborally (fig. 15) it is sclerotized on its basal half and weakly so on its distal half, with distinct line of demarcation between these regions. The basal half is fused laterally with the squames. The distal half is unpigmented, adorned with a few scattered microscopic hairs, and fused distally with the middle lobe. Distolaterally it is evaginated into a socketlike structure on each side to which the mesobasal portion of the lateral lobe is attached. The middle lobe, or median lobe (ML), is a large subrectangular piece which, according to Butler (1904), corresponds to the ligula of other insects. The latter term is not to be used, because a part of 12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 the pronotum is also called the median lobe. Adorally (fig. 16) it is weakly sclerotized and pigmented on its apical third and narrowly so along its lateral portions, with long hairs on these areas: the re- MAXILLA LABIUM = [6 Fics. 13-16.—Mouth parts. 13 and 15, Aboral views; 14 and 16, adoral views. maining area is unpigmented and adorned with a few scattered micro- scopic hairs. The squames (SQ) are a pair of convex sclerites, which, according to Tillyard (1917), correspond to the palpigers. (The term squames No. 6 MORPHOLOGY OF THE DRAGONFLY—CHAO 13 is rather confusing since it has been used to designate different struc- tures in different orders of insects.) Aborally (fig. 15) they are subrectangular in shape, mesobasally fused with the basal portion of the mentum, laterally deflected to approach the sclerites of the mentum on the adoral side. The lateral lobes (LL) are a pair of hairy sclerotized structures attached to the squames and mentum, with their mesal margins straight and their lateral margins strongly convex. Each lobe is produced mesoapically into a very long, bare, and sharp end hook (EH) point- ing meso-orally. Lateral to the end hook is an even longer hairy movable hook (MH) with its basal half about twice as wide as its apical half. CERVIX (Figures 17-20) The cervix (sometimes called neck or microthorax) is a region between the head and the prothorax, narrow anteriorly, mainly mem- branous, with lateral, dorsal, and ventral cervical sclerites. The lateral cervical sclerites are the largest and serve as pivots for the head while the other sclerites are mostly small and completely surrounded by membranes. Each of the LATERAL CERVICAL SCLERITES consists of a basal post- cervicale (PC) and a distal eucervicale (EC) (Crampton, 1926) forming a hinge at their juncture. The postcervicale is V-shaped, fit- ting between the pronotum and the episternum, with the arms of the V pointing anteriorly. The eucervicale is incompletely divided into a dorsal and a ventral portion by a deep and narrow incision. The anterior half of the dorsal portion of the eucervicale is unpigmented and whitish. The ventral portion is somewhat twisted, produced mesad and then anteriorly into a long process called the cephaliger (CEP) ; the latter lies freely inside the cervical membrane, with its apex con- nected with the occipital condyle (fig. 3, OCCD). There are two transverse DORSAL CERVICAL SCLERITES (DC) in the middle of the cervix, with a pair of small and weakly sclerotized sclerites between them; the posterior transverse sclerite also being weakly sclerotized. Another pair of dorsal sclerites is situated on the posterior margin of the cervix: they are fairly large in size, well sclerotized, and partly obscured dorsally by the anterior lobe of the pronotum. The paired VENTRAL CERVICAL SCLERITES (VC) are roughly L- shaped, with the transverse bars of the L’s almost touching each other, and the other ends of the L’s being in contact with the occipital con- 14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 dyles. There is a small weakly sclerotized area attached at the angle of the L, with many tiny tubercles each bearing a microscopic hair. THORAX The thorax is differentiated into two distinct parts, namely a small prothorax and a large synthorax (the latter also called pterothorax) representing the fused mesothorax and metathorax. PROTHORAX (Figures 17-20) The prothorax is a small segment, narrow anteriorly, with its length subequal to the vertical diameter of its anterior end which is about two-thirds that of its posterior end. The pronotum (figs. 17, 19) covers the dorsal half of the segment, topographically differentiated into anterior, median, and posterior transverse lobes alternated with two furrows where ridges are produced internally. The anterior lobe (AB) has its anterior margin whitish. The anterior furrow is deep and about as broad as the anterior lobe, laterally with a depression on each side where a long, pointed apodeme is produced internally. The median lobe (MB) is divided into two parts by a narrow median sagittal groove. It is minutely tuberculate in the areas on both sides of the median groove and on its lateral portions and with a similar but smaller area between them. The lateral tuberculate areas are adorned with fine, long, and wavy hairs. A large semicircular depres- sion is situated at the anterior end of the median groove and gives rise to an internal apodeme which is long, slightly curved, narrow in the middle, and expanded distally into a discoidal structure. The posterior lobe (PB) is somewhat like a Cupid’s bow in shape on its dorsal aspect, dorsally minutely tuberculate, and with long, fine, wavy hairs all over. Each of the propLeurA (fig. 19) consists of two approximately equal-sized sclerites, the episternum and the epimeron, separated by the pleural suture (PLS,) which is almost perpendicular to the long axis of the body. Along the pleural suture a low ridge or lateral apodeme is produced internally. The episternum (ES) is a transverse piece, narrow in the middle, with its dorsoanterior angle fused with the sternum, and its posterior portion slightly bulging. It is minutely tuberculate all over, with the bulging area having larger tubercules and long wavy hairs. The epimeron (EM,) is a rectangular piece, slightly higher than wide, tuberculate only on its ventroposterior por- tions, dorsally produced into a narrow strip along the posterior border No. 6 MORPHOLOGY OF THE DRAGONFLY—CHAO 15 of the pronotum to approach closely the lateral end of the posterior lobe. —— DORSAL VIEW N\ eww 7 “e LATERAL VIEW POSTERIOR VIEW Fics. 17-20.—Prothorax and neck. The ProsTERNUM (fig. 18) consists of an anterior, large, elongate, rectangular piece and a posterior pair of small sclerites, the latter collectively termed the postfurcasternum (PF ST) (Crampton, 1926). The rectangular piece is divided into two portions, an anterior basi- 16 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 sternum (BS) and the posterior furcasternum (FS), by an anteriorly arched sternacostal suture (SCS) which ends at the large furcal pits (FP), or apophyseal pits (Ferris, 1940). Along the sternacostal suture a ridge is produced internally. The basisternum is fused on its anterior angles with the episterna. It is minutely tuberculate, with a broad, shallow, submarginal circum- scribing depression; the posterior course of the depression being weakly sclerotized and unpigmented. The area between the posterior depression and the sternacostal suture is raised, with long hairs along its anterior margin. The central area of the furcasternum (FS) be- tween the furcal pits and the sternacostal suture is protuberant and rather coarsely tuberculate. The furca (F,) consists of a pair of large, inverted, foot-shaped apodemes widely separated from each other; each arm with a long narrow tendon at its apex. SYNTHORAX (Figures 21-27) The synthorax, or pterothorax, is composed of the fused mesothorax and metathorax, ventrally carrying two pairs of legs on its anterior half, and dorsally two pairs of wings on its posterior half. The pleura are very large while the terga and the sterna are very small. TERGA (Figures 21, 22) The terga are connected with the pleura only by membranes. They are not connected with the latter by prealares anteriorly or by post- notum posteriorly, such as is the case in most other winged insects. Thus, it would seem that the terga can move up and down without distortion during flight. The anteriormost part of the mesotergum is roughly a T-shaped structure divided into the AcroTrERGITE (ATG) and the pREscUTUM (PSC,.) by the antecostal suture (ACS) along which a pair of small phragmata is produced internally. The ends of the transverse bar of the T are the prealares (PRA) which serve, in the present species, as pivots for the anterior lobes of the humeral plates (HP), and are connected posteriorly with the detached plates of the scutum (Snod- grass, 1935) to be described later. The scutum (SCT,) is a large, somewhat ovoid, convex structure, wider posteriorly, with a large, central portion weakly sclerotized and unpigmented. Anteriorly the lateral portion of the scutum is detached No. 6 MORPHOLOGY OF THE DRAGONFLY—CHAO 17 into a bilobed plate which is fused with the prealare. Posteriorly the adanal sclerite, or posterior notal wing process (PWP), is narrowly separated from the scutum by an incision and is articulated with the axillary plate. The detached plate of the scutum has been shown by Snodgrass (1930, fig. 11 A, a; 1935, fig. 123 B, a), but its importance in the wing mechanics has not been well investigated. It consists of two lobes, the anterior suralare sclerite, or anterior notal wing process (AWP), and the posterior adnotal sclerite, separated by the notal incision or the lateral emargination. Near the mesal margin of the detached plate there is a groove along which an apodeme (AP) is produced internally. The latter is a large, elongate structure, apically expanded into an irregularly elongate plate which is constricted in the middle. This apodeme is called cap-tendon by earlier workers (Calvert, 1893; Tillyard, 1917). To this apodeme the principal ele- vator muscle is attached. Two more small sclerites are present. One of these is the first axillary (IAX), also called notal ossicle, notale, or notopterale. It is elongate triangular, situated along the mesal margin of the humeral plate, and mostly obscured by the latter in dorsal view. The other small sclerite, distinct from the adnotal sclerite in this species, is situated between the latter and the anteromesal margin of the axillary plate. A preliminary study of Anax junius, a common American species (Aeschnidae), shows a condition in which the detached plates are not fused with the prealares and the axillary sclerites are not independent from the anterior notal wing processes. The importance of the detached plates of the scutum and the axillary sclerites morphologically and phylogenetically in the wing mechanism will be discussed later. The scuTELLUM (SCL,z) is a comparatively small, convex, trans- verse, ovoid sclerite from the posterolateral angle of which the corru- gated axillary cords (AXC) are produced. A small transverse sclerite is closely applied to and partly fused with the anterior margin of the axillary cord. Along the line of fusion a low ridge is produced in- ternally and to it the postscutellum (PSCLz) is articulated. The PosTSCUTELLUM (PSCL2) (= acrotergite, Whedon, 1938) is even larger than the scutum. It is a subrectangular sclerite, pigmented laterally only, separated by an internal V-shaped ridge into three re- gions which are probably inaccurately termed median postscutum and lateral postscutella by Tillyard (1917). The anteriormost part of the metatergum is a narrow transverse sclerite, the pREScUTUM (PSC3;), with a submarginal suture along which a low ridge is produced internally. It is mostly obscured by the 18 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 preceding postscutellum to which it is connected by a tiny linear scler- ite on each side. The scurum (SCT;) is a large transverse sclerite with rounded anterior angles. Its central portion is weakly sclerotized and unpig- mented. A small spinelike apodeme is produced internally from a pit which is situated very close to its anterior margin. Laterally the suralar, adnotal, and adanal sclerites are not separated from the scutum (also true in Anax junius). The scurELLUM (SCLs;) and the avillary cords (AXC) are similar to those of the preceding segment, except that the latter structures are divergent posteriorly in the metathorax. The POSTSCUTELLUM (PSCL;) is mainly weakly sclerotized, un- pigmented, and merged with the membrane between it and the first abdominal tergite, except for a trace of sclerotized area on each side posterior to the axillary cord. PLEURA (Figure 21) The pleura of the synthorax are very large and greatly modified. Laterally the synthorax has two oblique sutures, the mesothoracic pleural (PLS,) and the metathoracic pleural (PLS:) sutures, located between the coxae and wing base of their respective regions. On the lower portion of the synthorax between the two pleural sutures is a transverse ovoid spiracle, the posterior spiracle, or metastigma (IIISP). Just anterior to the metastigma is a short slanting suture, the middle lateral suture (MLS), which represents the remnant of the intersegmental suture (Snodgrass, 1909). Different names have been used by various taxonomic workers to designate the above-mentioned sutures as follows: Mesothoracic pleural suture =Humeral suture (Calvert, 18903; Needham, 1903, 1930; Tillyard, 1917; Fraser, 1933). =First lateral suture (Needham, 1903, 1930). Intersegmental suture (Snodgrass, 1909) =Interpleural suture (Tillyard, 1917). =Middle lateral suture, or middle suture (Needham, 1930). =First lateral suture (Rambur, 1842; Calvert, 1893; Tillyard, 1917). =Second lateral suture (Needham, 1930). =Anterolateral suture (Fraser, 1933). No. 6 MORPHOLOGY OF THE DRAGONFLY—CHAO I9 Metathoracic pleural suture =Second lateral suture (Calvert, 1893; Tillyard, 1917). =Third lateral suture (Needham, 1930). =Posterolateral suture (Fraser, 1933). The course of the mesothoracic pleural suture (PLSz) is crooked, with its lower one-fourth almost perpendicular to the longitudinal axis of the body, its upper three-fourths slightly bowed and slanting posteriorly, and with a short portion between them smoothly curved. The angle of skewness is 60° and the angle of tilt of wing bases is 32° in the present species. These angles are greater than the corresponding angles in any gomphine dragonfly measured by Needham and Anthony (1903). Needham and Anthony defined the degree of skewness or inclination (also called angle of humeral suture) as the acute angle between the suture and an imaginary line perpendicular to the longi- tudinal axis of the body, and the angle of tilt of wing bases as the acute angle between a line drawn through the wing bases and the longi- tudinal axis of the body. It must be pointed out that Tillyard (1917) used the term angle of obliquity in synonymy with skewness, both of which he defined as angle of tilt of wing bases. This must not be confused with the angle of skewness of Needham and Anthony. The metathoracic pleural suture (PLS;) has almost the same shape as the preceding one except that its lower one-fourth is a little slant- ing posteriorly instead of almost perpendicular to the longitudinal axis of the body, and its upper three-fourths is almost straight. Particular attention is here given to the courses of the pleural sutures and the relative positions of the wings and the legs. The older view as to the phylogenetic origin of the orientation of these parts is well expressed by Tillyard (1917, 1926), Imms (1948), and others who maintain that the great development of the mesothoracic anepisterna “pushes” the wings backward away from the head, carry- ing the terga with them, and that the correlated growth of the meta- thoracic epimera “pushes” the sterna and the legs forward so that the latter come into position close behind the mouth. However, judging from the courses of the pleural sutures, it is believed that the vertical positions of the lower portions of the pleural sutures (a condition usu- ally considered to be primitive) probably indicate the primitiveness of this region while the posteriorly slanting positions of their upper por- tions probably indicate the evolutionary enlargement of the upper portion of the synthorax. The static nature of the lower region indi- cates that the legs have not been “pushed” forward, while the poste- riorly slanting position of the upper region indicates that the wings 20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 om SC H ~ [:-® rR +M G2\)\ AYl SxCoP NL ISS: i : 2 2 P yess INTERNAL VIEW OF DORSAL PORTION Fics. 21-23.—Synthorax. No. 6 MORPHOLOGY OF THE DRAGONFLY—CHAO 21 have moved backward away from the head, to a position at or near the center of gravity of the greatly elongated body of the insect. Regarding the positions of the three pairs of legs, it is interesting to note that the knee joint between the femur and the tibia of the prothoracic leg is directed sideward, that of the mesothoracic leg, side- ward and backward, that of the metathoracic leg, backward. The pleurocoxal articulation of the metathoracic leg indicates a rotation of its axis of about 90°. The result of the rotation of the metathoracic legs might be of definite advantage to the insect in catching prey dur- ing flight or in perching on the twig. The legs are not fitted for walk- ing but they serve very well for climbing when that mode of progress is required. The mesothoracic episternum is divided by an inverted V-shaped suture into anepisternum and katepisternum. The anepisternum (AES,) is greatly expanded and meets with the corresponding part of the other side of the thorax along the middorsal line to form a ridge, the dorsal carina (DCR), anterior to the wing bases. At the anterior end of the dorsal carina there is a transverse ridge, the collar (COL), which is adorned with fine wavy hairs. On the dorsal aspect of the synthorax the area between the collar and the wing bases is called the front of synthorax. At about the middle of the front of synthorax the dorsal carina is raised into a sharp point. Posterior to this point the carina is divided into two low ridges which are parallel for a short distance and then widely divergent. These ridges are collectively called the antealar ridge (ARG), or crest. The area poste- rior to the ridge is called the antealar sinus (AAS). Anterior to the collar there is a transverse sclerite, the spiracular dorsum (SPD), which is medially invaginated to form a hornlike apodeme. The de- flected portions of the spiracular dorsum are called mesostigmatic laminae (MSL). Each lamina bears an anterior spiracle, or meso- stigma (IISP). A preliminary study of a few species of gomphine dragonfly nymphs shows that there are three pairs of small interseg- mental sclerites: a median pair (the members of which are narrowly separated from one another), a lateral pair bearing the spiracles, and a ventrolateral pair anterior to the katepisternum. Some, if not all, of these plates are referred to as prothoracic spiracle plates by Snodgrass (1909) who states that ‘‘in the adult they unite with each other across the back, thus forming a complete spiracular dorsum which fuses with the mesothorax. . .” The katepisternum (KEP.z) is a vertical sclerite ventrally separated from the sternum by a distinct oblique suture, the sternopleural suture (SPS), from which two large apodemes, the prefurca (PF.) and the 22 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 squame (TNz), are produced internally. Anteriorly the katepisternum is flanged by a narrow strip of sclerite which is continuous with the mesosternum and is probably a part of it. The mesepimeron (EPM,) is fused with the metathoracic anepi- sternum, except below the metastigma where the middle lateral suture (MLS) is separated from the mesepimeron. This sclerite surrounds the posterior half of the mesothoracic coxal cavity. The metathoracic episternum is divided into two parts, the anepi- sternum (AES;) and the katepisternum (KEP;), by an incomplete and slightly undulate suture below the metastigma. Dorsally the anepi- sternum is produced into a hairy lobe between the two wing bases. Ventrally the katepisternum extends to a place lateral to the furcal pit, without any suture separating it from the sternum. The meta- thoracic epimera (EPM3) are very large, fusing ventrally with each other to make a large unsutured area. This area bears a conspicuous median inverted Y-shaped pigmented area that is quite in contrast to that of the neighboring regions because of its lighter color and the direction of pigment streaking. The Y-shaped area has longitudinal streaks while the neighboring portions have transverse streaks. A pair of small apodemes at the center of the Y and a low ridge along the stem of the Y are produced internally; the latter thickening is visible externally and was often mistakenly regarded as a suture by earlier workers. The area between the arms of the Y is called post- sternum or pseudosternum (PSTN) and is generally regarded as a secondary sclerite filling the gap between the metasternum and the first abdominal sternite. This interpretation seems very inadequate and a more careful study of this sclerite is very desirable. The post- coxale (PCX;) is situated on the mesal edge of the metathoracic coxal cavity. The latter is elongated, with the coxal articulatory process lateroposteriorly located. STERNA (Figure 24) The mesosternum (IIST) is a clearly defined area between and in front of the two furcal pits, medially keeled, laterally separated from the katepisternum by an oblique suture, the sternopleural suture (SPS), anterolaterally produced into a narrow piece along the an- terior margin of the katepisternum on each side. The furcal pits (FP.), or apophyseal pits (Ferris, 1940), are close to one another, and are situated near the mesal margins of the coxal cavities. The metasternum (IIIST) is medially keeled, laterally deeply invaginated along both sides of the keel (fig. 26, posterior view of cross section No. 6 MORPHOLOGY OF THE DRAGONFLY—CHAO 23 of metasternum posterior to furcal pits; fig. 27, anterior view of cross section of same slightly posterior to the preceding section), and partly obscured by the approximately raised postcoxales (PCXs3). SYNTHORACIC ENDOSKELETON (Figure 25) The synthoracic endoskeletal projections are of different forms: (1) Ridges, (2) a complicated fusion product called the neural canal surrounding the nerve trunk, and (3) a median hornlike apodeme on the spiracular dorsum. The ridgelike apodemes are mesopleural and metapleural, interseg- mental, peristigmatic, and precostal apodemes. The mesopleural and metapleural apodemes (PLA;, PLA;) are strengthened by about eight short ridges projecting from their posterior sides. The lower portion of the mesopleural apodeme along the edge of the katepisternum and the apodeme between the anepisternum and katepisternum are inap- propriately called (due to different interpretation of sclerites) the sternoepimeral and sternoepisternal apodemes respectively by Tillyard (1917). The intersegmental or interpleural apodeme (IPLA) is a simple ridge with a spinelike process at its upper end near the meta- stigma, and with a very long fine tendon projecting from it at about the middle of its course. The peristigmatic apodeme (PSA) lies along the suture separating the metathoracic anepisternum from the kat- episternum. The precostal apodemes are situated along the meso- thoracic sternopleural sutures. From each precostal apodeme two dis- tinct structures are produced: the prefurca (PF,.) and the squame (TN,). The prefurca is a tonguelike structure along the edge of the stigmatic lamina. The squame (which term is also used in maxilla) consists of a short stalk apically expanded into an elongate flat surface, situated anterior to the coxal cavity: this is regarded by Tillyard, probably erroneously, as a part of the furca. The NEURAL CANAL (figs. 26, 27, NC) is a complicated fusion product of several invaginated processes. This fusion product is dif- ferentiated into two portions: an anterior portion on the mesosternum and a posterior portion on the metasternum. These two portions are connected dorsally, but are open between them on each side. The anterior portion of the neural canal is formed into a complete ring by the apical fusion of the mesothoracic furcal arms. The dorsal portion of this ringlike structure is expanded into a flat surface which is produced anteriorly into a pair of short protuberances, a pointed process curling ventrad (fig. 24), and lateroposteriorly into a long flat 24 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 arm which is attached to the posterior margin of the postcoxale to act as a brace. The posterior portion of the neural canal is an elongated structure formed by the apical fusion of the invaginated sternal fold (fig. 26, PLF). The dorsal of this fusion product is greatly expanded into a shieldlike structure which is an elongate, ovoid, flat surface, with two foci of heavy sclerotization anteriorly and posteriorly with a pair of long, narrow, ribbonlike tendons (fig. 25). The foci of sclerotization indicate the positions of the metathoracic furcal arms which are lateral to the sternal folds (fig. 25). From each focus a very long, fine tendon is produced. WINGS The wings are held horizontally on both sides of the body: they are unable to fold back on the top of the abdomen. This method of hold- ing the wings is pointed out by Crampton (1924) and his contempo- rary workers as an important archaic characteristic of the Palaeoptery- gota (including as living forms the dragonflies and mayflies). It appears that this condition is accounted for by the primitive structure of the wing base. However, it is interesting to note that great con- fusion exists in the literature regarding the structure of the regions at the bases of the wings of dragonflies and possibly also of mayflies. Structures involved are (1) wing base, (2) axillary sclerite and lateral regions of scutum, (3) pleural wing process and epipleurites, (4) principal wing muscles, (5) articulatory points, and (6) the mechanics of flight. The wine BASE (fused bases of wing veins) consists of two strongly sclerotized plates, the anterior humeral plate (HP) and the posterior axillary plate (AXP). Dorsally the humeral plate is divided into three lobes by transverse grooves. Ventrally the lateral edge of the humeral plate is connected by membrane to the distal margin of the pleural wing process. It does not seem to form an articulation with the anterior arm of the pleural wing process such as is mentioned by Snodgrass (1935, p. 221). The axillary plate is subquadrate in shape, slightly convex dorsally, posteriorly fused with the axillary cord (AXC). The costal vein (C) is articulated with a small intermediary plate (IP) which is in turn articulated with the posterior lobe of the humeral plate. Ventrally a short, rounded protuberance is found at the fused bases of C and Sc. The veins posterior to R+M are firmly fused with the axillary plate. The base of R+M is forked. Its dorsal branch strengthens the anterior margin of the axillary plate. Its ven- tral branch forms a process which is articulated with the pleural wing No. 6 MORPHOLOGY OF THE DRAGONFLY—CHAO 25 SS INTERNAL VIEW OF VENTRAL PORTION SYNTHORAX, VENTRAL VIEW ANTERIOR VIEW OF POSTERIOR VIEW OF X-SEC. BEHIND FP3 X-SEC. BEHIND FP3 a; a3 eean® EE ee DTTA“S PRETARSUS, g Ae EW ct)) VENTRAL VIEW Fics. 24-30.—Synthorax and legs. 26 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 process and is connected with the subalare by tough membrane. Thus the base of R+M has the same function as the second axillary of other orders of insects. It is probable that the second axillary sclerite is formed by detachment of a portion of the base of R+M or R. AXILLARY SCLERITE. Regarding the axillary sclerite (s), special attention is given to (1) the number and (2) the origin, since there appears to be a considerable amount of confusion in the literature regarding these considerations. In the species studied here there is only one, i.e., the first axillary sclerite (1AX), described previously. This sclerite has the same shape and is situated at the same position as that illustrated by Snodgrass (1909) for Pachydiplax longipennis. Another small sclerite between the adnotal sclerite and the anteromesal margin of the axillary plate is probably detached from the adnotal sclerite. Its homology is not certain. Crampton (1924) mentioned that in Palaeopterygota “there are frequently no alar ossicles, or at the most but one.” Forbes (1943) maintained that in the dragonflies there are no basal sclerites dorsally, or “no trace of dorsal axillary sclerites as separate elements.” Snod- grass (1909) pointed out that “only one distinct axillary is present” in the dragonflies. This axillary sclerite is clearly illustrated by him in this paper (1909, fig. 17, IAx), but not mentioned or illustrated in his later paper (1930) or his well-known “Principles of Insect Morphology” (1935). The present studies are in agreement with Snodgrass but not with Forbes. As to the origin of the axillary sclerites, Crampton and Forbes differ in opinion. Forbes (1943) mentioned that “the extreme bases of the veins are modified into a series of thickened knobs, the axillary sclerites.” Crampton (1942) maintained that “the axillary sclerites, alar ossicles or pteralia . . . are apparently formed, in part, as de- tached portions of the lateral region of the notum, and partly as de- tached basal portions of the wing veins, or as sclerotized areas at the bases of the veins.” He considered, on the basis of numerous com- parative studies, that the first axillary or the notopterale (notale) “probably represents a detached portion of the lateral edge of the notum.” Crampton’s opinion is adopted in this paper since in Anax junius the condition of fusion of the first axillary with the anterior notal wing process is perhaps indicative of such an origin. PLEURAL WING PROCESS and EPIPLEURITES. At the dorsal end of each pleural suture the pleuron is produced into an inverted foot- shaped pleural wing process (PLP). The tip of the foot (the poste- rior longer arm of the wing process) acts as the principal pivot for the articulation of the wing. The heel of the foot (the anterior shorter No. 6 MORPHOLOGY OF THE DRAGONFLY—CHAO 27 arm of the process) is connected to the humeral plate by membrane and does not seem to form an articulation with the latter. The an- terior basalare (BA) and the posterior subalare (SA), collectively called the epipleural sclerites or paraptera, are present. They are very small externally and so deeply imbedded in the membrane as to be easily overlooked. Internally each has a very large apodeme which has a stalk greatly expanded apically into a large surface for the at- tachment of the depressor muscle. The basalare is connected by tough fibrous membrane to the lateral portion of the anterior lobe and, to a lesser extent, to the posterior lobe of the humeral plate. The subalare is connected by similar membrane to the ventral branch of the base of R+M. It is also interesting to point out that the presence of the basalare and the subalare in dragonflies was probably correctly de- termined for the first time by Forbes (1943). They were considered as “‘cap-tendons” by earlier workers (Calvert, 1893; Tillyard, 1917). Snodgrass (1935) mentioned that “there are no epipleural sclerites in the dragonflies.” Probably he also considered the epipleural sclerites as tendons, since in the same works he mentioned that “in Odonata there are two anterior wing muscles . . . inserted by long tendons directly on the large humeral plate of the wing base,” and that “two posterior pleural wing muscles take their origins on the ventral edge of the epimeron in each alate segment and are inserted directly on the axillary plate of the wing base.” However, they seem to be more appropriately considered as basalare and subalare instead of tendons, since (1) they are distinct, though small, sclerites imbedded in the membrane in the same positions in which the epipleurites are found in other orders of insects; (2) they serve for the attachment of direct muscles as they also do in other winged insects; and (3) they are connected to the wing base by tough membrane as in other winged insects. Particular attention is called to the connection between the subalare and the ventral branch of the fused bases of R+M—a condition similar to the connection between the subalare and the second axillary sclerite. WING MUSCLES. Nine wing muscles in dragonflies have been recog- nized by Berlése (1909), Calvert (1893), and Tillyard (1917), but the apodemes of some sclerites to which the muscles are attached were called cap-tendons, and the sclerites considered to be of no morpho- logical importance. Of the nine muscles, three are very large: (1) The principal elevator, (2) the anterior depressor, and (3) the poste- rior depressor. The principal elevator (see Tillyard, 1917, p. 204, fig. 89, A, pe: and pez) is attached to the geat apodeme (AP2, AP3) produced internally from the detached plate of the scutum. The an- 28 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 terior and posterior depressors are attached to the basalare and suba- lare respectively. Snodgrass (1935) classifies flight muscles into two types, direct and indirect. The direct muscles are the axillary and epipleural mus- cles and the indirect are the dorsal and tergosternal muscles. The tergosternal muscles, according to Snodgrass, “are attached dorsally on the anterior lateral areas of the tergum, and ventrally on the basisternum before coxae.” The present study shows, however, that dragonflies have both types of flight muscles. This interpretation differs from what Forbes (1943) states that in Odonata the indirect muscles are “nonfunctional” or that “only direct wing muscles” are present. The direct (epipleural) muscles have been discussed before. There are several pairs of indirect muscles, the most important of which are the principal elevator muscles, which are attached to the detached portions of the scutum dorsally and to the “squame of furca” (produced internally from the pleurosternal sutures) ventrally. They have been homologized with the “‘first tergosternal” of other insects by Berlése (1909) whose opinion is adopted by Tillyard (1917). The dragonfly wing mechanics appear therefore to be not fundamentally different from those of higher groups of insects. ARTICULATORY POINTS. Each wing is articulated with the thorax in three places: (1) The ventral branch of R+M articulates with the posterior arm of the pleural wing process. This is the principal pivot of the wing. (2) The humeral plate articulates with the prealare. (3) The axillary plate articulates with the posterior notal wing proc- ess. The prealare-humeral articulation is particularly interesting in two respects: First, the prealare normally “extends laterad or ventrad to the episternum and thus supports the notum anteriorly on the pleural wall of the segment” (Snodgrass, 1935). In the present species, the prealare is separated from the episternum by a large mem- branous region. It does not offer any support to the notum anteriorly ; the latter thus moves up and down freely and synchronously with the movement of the wings. Secondly, the prealare-humeral articulation is probably unique to dragonflies, since in other winged insects the wings are articulated with the anterior wing processes instead of the prealares. MECHANICS OF FLIGHT. Since the author has not studied the mus- cles involved in controlling the wing movements, a discussion on the possible mechanics is based on inferences concerned with the sclero- tized structures described on a previous page. The wing mechanics in the dragonflies are similar to those of higher winged insects in two fundamental respects: (1) The wings No. 6 MORPHOLOGY OF THE DRAGONFLY—CHAO 29 are primarily controlled by the antagonistic indirect elevator muscles and the direct depressor muscles attached to the detached lateral plates of scutum and epipleurites respectively; (2) the subalare is con- nected to the wing base very close to the fulcrum while the basalare is far in front. This latter condition indicates that a pull upon the posterior depressor muscles would strongly depress the wing while a pull upon the anterior depressor not only would depress the wing but also deflect the anterior part of the wing to produce the sculling type of flight. On the other hand, the wing mechanics in dragonflies differ from those of higher winged insects in two important respects: (1) The prealare-humeral articulation is probably unique in dragonflies. This articulation forms the anterior part of the hinge line and differs from that in other winged insects in which the anterior notal process forms an important articulatory point. (2) Another feature probably also unique in dragonflies is that the terga are connected to the pleura by membrane only and the phragmata produced internally along the ante- costal sutures are very small. The latter fact indicates that the longi- tudinal dorsal muscles attached to the phragmata would be small, such as illustrated by Berlése (see Tillyard, 1917, p. 204, fig. 89, A, pt). The smail size of the dorsal muscles probably indicates that they do not produce an effective antagonistic action to the tergosternal elevator muscles. Judging from the above facts, it seems that the terga must probably move up and down during flight without distortion. This condition differs from that of other winged insects in which “the restoration of the dorsal curvation of the back by the contraction of the longitudinal dorsal muscles” will effect, in part, the down-strokes of the wings (Snodgrass, 1935, p. 234). As to the control of the direction of flight, the fore wings are probably more important in this action than the hind ones. This con- tention is based on the fact that the articulatory plates of the scutum are distinctly separated from the main body of scutum (detached plates) in the mesothorax but firmly fused with it in the metathorax. Thus the hinge line and consequently the pitch of the fore wing can be changed, but that of the hind wing appears to be fixed. WING VENATION (Figures 31, 32) The wings are transparent and supported by numerous veins form- ing a complicated network. The fore wings (fig. 31) are widest at the nodus (N) which is located at the middle of the anterior margin 30 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 of the wing. The hind wings (fig. 32) are slightly shorter and about one-fifth again as wide as the fore wings (the widest portion of the former is a little basal to the nodus which is situated at the basal two-fifths of the wing). In the male the inner margin of the hind wing is excavated and fringed with a narrow white edge, the mem- branule (mb), and the anal angle, or tornus (Aa), angulated. In the female the inner margin of the hind wing is not excavated and the anal angle is rounded. Both pairs of wings have a very conspicuous pterostigma (Pt) of the same size, shape, and color. The pterostigma is also called stigma or anastomosis, the latter being very rarely used. The term “stigma,” though frequently used, is rather confusing because it may refer also to the spiracles. It is a thickened area between Sc (Fraser, 1948) and R, near the apex of the wing, dark brown or black in color, elongate, about four times as long as wide, with its shorter sides oblique and parallel to each other; with its longer sides concave, surmounting about six cells; and with a strong vein, the brace vein (br. v.), ex- tending down from its basal side. Several systems of notation of the venation have been proposed. Originally, de Selys gave a name to each vein without notation in use. Later on, Needham gave an interpretation based on the larval wing tracheation, with a notation based on the Comstock-Needham system. This system has been widely used in the last thirty years or so. Till- yard (1926) gave a different interpretation, based on the study of fossil forms. His system, with a few modifications, has been generally accepted by later entomologists. Borror (1945) summarized in two tables the different systems of terminologies used by different authori- ties, such as de Selys, Kirby, Needham, Tillyard, Tillyard and Fraser, and others. Forbes (1943) gave very different notations. Fraser (1948) modified the costal vein and the anal veins. The present paper uses Tillyard’s system (1926) with a few modifications by subsequent workers. To summarize the points, a table (p. 31) is prepared to show a comparison of terminology of the principal longitudinal veins of the dragonfly wing. PRINCIPAL LONGITUDINAL VEINS. The principal longitudinal veins are costa, subcosta, radius (4 branches with 2 intercalaries), media (a single vein), posterior cubitus, and anal. The costa (C), or costal vein, is a simple and strong vein which, according to Fraser (1948), extends from the base of the wing to the nodus. The subcosta (Sc) is a long vein posterior to the costa. According to Fraser (1948), its course is from the base of the wing to the nodus MORPHOLOGY OF THE DRAGONFLY—CHAO 31 No. 6 WAS xVI Ny nO-+W+Sa NI JS (8£6T) Jose1y pue PreATIL wny VY ny inte) VIN A Sty SIA eB ea *Y aN “YI ey TW et Ty Ny NI Wt+u Wt+u 9S Ss) 8) a) (9761) (LT6T) preAqihL Joj9as [eseq-qns [eUIxO1g 9]8ULII JO 10}99S IOLIOJUT ®}S09}S0g 9] 8UeII} JO 1019s Jo1Iadnsg snjnoie JO 10}9as JaMO'T 10}99S URIPI[ Joj9as [epouj}sog 4o}0es jediourig snynore jo 10}09as 1addy ueIpay eysSOIqNS eSsOD ul9}SAs UPISATIS SUIDA JeuIpNysuoy jediourid sy 7, Ng W+u oS SD uorzeIAsIqqy Gece Oo tras ene PIpaUl JOLIN} en Orca, OnOeO sniper qyqyu-+ YjuAnoy es AxeyeoiojUl SNIpes PITY, @ hy RES" RS te a STN 36 STERNITET, ¢ STP 1 aN 4 ie a — STN Hea 6 O~S STERNITE I,¢ Sierra STN 38 ‘ STERNITE V, 2 \ ' A 3 oi Salaam “STERNITE VI,¢ Fics. 31-39—Wings and abdomen. 34 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 dragonflies (e.g., Fraser, 1940; Borror, 1945). Forbes (1943) called this vein the plait vein (Pl) which, according to him, corresponds to the anal furrow of insects of other orders. The basal portion of this vein is regarded as the common stem of the cubitus (Cu) by Needham (1903) and as the common stem of Cu,+1A by Tillyard and Fraser (1938). The anal vein (A) is slightly undulated at its basal portion. It meets with CuP at the apex of the triangle. The apical portion of the anal vein (A,) from the apex of the triangle to the posterior margin of the wing is parallel to CuP in the hind wing. On the other hand, in the fore wing it is parallel to CuP for a long distance and then di- verges from the latter. The notation A used in this paper refers to the vein from the base of the wing to the posterior apex of the tri- angle. A, denotes its extension. Tillyard (1926) regarded the basal portion (A) as a backward extension of IA toward the base of the wing. He designated the portion from the posterior apex of the triangle to the cubito-anal cross vein (cu-a) as Ab (anal bridge) and the portion between cu-a and the base of the wing as A’. Fraser (1938) demonstrates that the anal vein in the Odonata has an inde- pendent origin from the base of the wing. (The present notation A equals Ab+A’ of Tillyard.) In the hind wing the anal area is greatly expanded. There are three distinct anal veins, namely, Aia, As, and As. Aia and A, become fused not far from their origins thus forming a 2-celled anal loop (AL). The vein that separates the anal loop into two cells is called the anal supplementary (mspl) or midrib (mr). Forbes (1943) used a new term, “axillary” (AX), for the veins often called “anal” but which, according to him, are distinct from the origi- nal anal vein which is usually the Pl of his system. CROSS VEINS. The more important cross veins are as follows: Nodal, subnodal, antenodal and postnodal, primary antenodal, brace vein, arculus, oblique vein, and cubitoanal vein. The brace vein, arcu- lus, and oblique vein have been mentioned before and will not be repeated again. The nodus, or nodal vein (N), is a thick vein situated between the costal margin and R,. Both notations N and u have been used but the former is adopted in this paper. Their positions in the fore and hind wings have already been mentioned before. The anterior portion of the nodal vein coincides with the bending part of Sc. The extension of the nodal vein between R, and R,z is called subnodus (sn). Be- tween the costal margin and R, there are many cross veins, those between the base of the wing and the nodus being antenodal cross veins (Ax) and those between the nodus and the basal end of the No. 6 MORPHOLOGY OF THE DRAGONFLY—CHAO 35 pterostigma being postnodal cross veins (Px). The first and the fifth or sixth antenodal cross veins are thickened and are called primary antenodal cross veins (Ax, and Ax,). It should be noted that Forbes (1943) used the same notation Ax for the veins which he called axillary veins. This has been mentioned before. The number of the nodal veins varies. In systematic work the nodal index such as 13-16 | 16-12 I3-II | II-13 antenodal and postnodal cross veins in the left and right fore and hind wings respectively. The nodal indices of ten specimens are shown as follows: has been often used and indicates the number of the "3-16.°| 16-12. «, 11-14 || @e=13 g: T-19 | 18-2E “o. 12-15) aa My Mee eee rein Olan) JiTte 1) emg 13204" rene |i esren fey faG-1r a. 12-16'|| To-12 g, F219 | 18-10 oe 13-16 | 15-12 9: BERNE OCURA ll te. ae eee ALE aaa OE LE aae | ’ [sonic Vaso elm fo resto 4 Tose |) angers) ger 2-07) G12 4. £3=10 [Bar ai eS 2 eee eel ee ee The cubito-anal cross vein (cu-a) is a vein between CuP and A, basal to arculus for a considerable distance. Different notations have been given to this vein, such as ac (anal crossing, Needham), Cux (Tillyard, 1917), Ac (Tillyard, 1926), AC (Fraser, 1940), and cu-a (Borror, 1945) ; the last notation is used in this paper. The different terminologies are accounted for largely by the different interpreta- tions of the anal vein. CELLS and SPECIAL AREAS. The important cells and special areas are as follows: Pterostigma, basal space, triangle, hypertriangle, sub- triangle, discoidal field, basal anal area, anal loop, anal field, and anal triangle. The pterostigma (Pt) has been mentioned before and will not be considered again. The basal space (bs) is an area at the base of the wing, bounded anteriorly, posteriorly, and apically or externally by R+M, CuP and arc respectively, the first two being subparallel and the last slightly slanting. It is also called by different names, such as median space, midbasal space, sub-basal space, and basilar space. It is about 3} to 4 times as long as wide. The triangle (t) is a distinct and almost isosceles-triangular space formed by CuP basally and two cross veins anteriorly and apically (or externally) respectively. A space anterior to the triangle from arc to the apex of the triangle is called hypertriangle (h), which is also called by different names such as supratriangle, hypertrigone, or supratrigone. It is a narrow space bounded basally by the posterior 36 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 portion of the arculus or m-cu, anteriorly by a portion of MA, and posteriorly by a vein which is composite. The basal portion of this composite vein is a part of CuP and the distal portion a cross vein between CuP and MA. This cross vein is also the anterior side of the triangle. Its direction is such that it looks like part of a longi- tudinal vein. The subtriangle (s), or internal triangle, is also an isosceles triangle. It is situated basal to the triangles with the vertical part of CuP as their common side. It is bounded externally by the vertical part of CuP, posteriorly by a part of A, and basally by a slanting cross vein between CuP and A. Phylogenetically the triangle and the subtriangle are collectively called the cubital area, which is homologous with the discoidal cell or quadrangle of Zygoptera. The area apical to the triangle between MA and CuP is called the discoidal field. The discoidal field in the fore wing is of almost the same width throughout except that the portion beyond the level of nodus is slightly widened, while that of the hind wing is considerably widened at the posterior margin of the wing. The difference in shapes of the discoidal fields in both wings is accounted for by the different positions of the apical portion of the CuP. The basal anal area is a narrow space posterior to the basal space. It is situated between CuP and A and is limited by the cross vein cu-a. The anal loop (AL) is a 2-celled area in the hind wing bounded by A, Aia, and A, on its anterior, apical, and basal sides respectively. It is bisected by a short vein, the anal supplementary, or midrib (mr). The anal field refers to the area bounded by A, Az, Aia+Ac, and the posterior margin of the wing. It includes the anal loop in the hind wing. In the fore wing its apical limit is about at the level of the posterior apex of the triangle. The anal field has two rows of cells between A and the posterior margin of the fore wing, whereas there are five rows in the hind wing. The anal triangle (at) is a 4-celled space at the extreme base of the hind wing in the male, bounded anteriorly, externally, and basally by A, As, and the basal margin of the wing respectively. The basal mar- gin of the hind wing is flanged by a narrow whitish membrane, the membranule (mb). In the female the anal triangle is 8- or 9-celled. LEGS (Figures 28-30) The legs are small in comparison with the size of the body. They are strongly armed with spines. The prothoracic legs are the smallest, being slightly smaller than the mesothoracic legs, which in turn are No. 6 MORPHOLOGY OF THE DRAGONFLY—CHAO a7 considerably smaller than the metathoracic legs. The difference in size of the legs is accounted for especially by differences in length of the femur, tibia, and tarsus, since the coxa and trochanter are not con- spicuously different in lengths in the three pairs of legs. The coxa (CX) is of moderate size, more or less conical in shape, with its outer surface much longer than its inner surface which is conspicuously bulged. The basal portion of the outer surface is modi- fied to form the pleural articular socket which is articulated with the pleural process of the thorax. The basal end of the coxa is girdled by a submarginal basicoxal suture (BCXS), along which a ridge, the basicosta, is produced internally. The basicosta is enlarged on the outer surface posterior to the pleural articular socket. The basicostal suture sets off a marginal flange, the basicoxite (BCX), which is en- larged on the outer surface posterior to the pleural articular socket. Distally the coxa bears an anterior and a posterior articular socket to which the trochanteral articular condyles are attached. The TROCHANTER (TR) is a slender segment, about as long as the coxa, having a short outer surface so that its distal end is obliquely truncated. A transverse constriction gives this segment a superficially 2-segmented appearance. The basal portion is attached to the coxa by an articular membrane. It is also articulated with the coxa by an anterior and a posterior trochanteral articular condyle. The coxo- trochanteral condylic hinge is a right angle with the pleurocoxal articu- lation so that it there forms a “universal joint’ which allows a wide range of motion of the leg. A condylic hinge is also present at the distal end of the trochanter. This operates at a right angle to the coxotrochanteral condylic hinge, but permits of much less freedom of motion than the latter since nearly the entire basal rim of the femur is closely attached to the distal end of the trochanter. The anterior surface of the articular membrane between the coxa and trochanter is invaginated to form a deep pouch, the posterior wall of which is thickened and tendonlike in structure. This undoubtedly serves for the attachment of a muscle internally. On the inner wall of the trochanter there is a group of short and robust spines. There are only four or five spines on the basal, and the same number on the distal, portion of the trochanter of the pro- thoracic leg, whereas there are many on the distal portion of the tro- chanter of the mesothoracic and metathoracic legs. These spines are arranged at random: they are not arranged in a definite row to form a trochanteral brush such as reported by Cowley (1937) to occur in some other dragonflies. The FEMuR (FE) is the longest segment of the leg, nearly cylindri- 38 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I22 cal, armed with short stout spines on its inner surface which faces ventrally in its natural position. The front femur is slightly curved and therefore fits nicely along the side of the thorax. The hind femur is straight, slightly compressed, and is held beneath the thorax. Its spines are more irregularly arranged on the basal portion than on the distal portion where they are distributed in two distinct rows. Pro- ceeding distalward the spines are progressively larger and more widely separated. The area between the two rows of spines is smooth, flat, or slightly grooved, fitting it for the reception of the tibia when the latter is flexed close against the femur. The distal margin of the femur is crowned with a few short spines. The trp1a (TI) is a slender segment, convex on its dorsal or outer surface, flattened on its ventral or inner surface, armed laterally with a row of flattened spurs and dorsally with two parallel rows of short spines. It is constricted and slightly bent near its basal end which is articulated with the former by an anterior and posterior condyle. The articular membrane between the femur and the tibia has the same condition of invagination as that found in the membrane between trochanter and femur. The flattened lateral spurs are of two types: (a) The short and swordlike type; and (b) the elongate type. The short swordlike spurs number about 8 or 9 in a row, situated on the apical half of the anterior margin of the prothoracic tibia in either sex. They are col- lectively called tibial comb (TIC) which was first pointed out by St. Quentin (1936) to be present on the prothoracic tibia of ail dragon- flies. Each spur is set on a socket which is oblong in shape. The spur is not evenly sclerotized, but has one edge unpigmented and thinner than the other edge. The elongate type of spur is long, undulated, and pointed at the apex. Along the anterior margin of the tibia there are four such spurs basal to, and one apical to, the tibial comb on the prothoracic leg, whereas there are eight on the mesothoracic or meta- thoracic leg where the tibial comb is absent. Along the posterior mar- gin of the tibia there are eight to ten such spurs. Proceeding distal- ward these spurs are progressively shorter but broader. The function of the tibial comb is unknown. Garman (1917) said that it might be used for the cleaning of the mouth parts and antennae. Needham and Haywood (1929) said that it might serve to hold the dragonflies’ food. St. Quentin (1936) mentioned that it might be used for the cleaning of compound eyes. On the ventral surface of the tibia there is a group of bristles along the base of the tibial comb and a nonsclerotized structure near the distal end of the tibia. This nonsclerotized structure is elevated and No. 6 MORPHOLOGY OF THE DRAGONFLY—CHAO 39 elongated. It is present on the prothoracic tibia of the male sex only. As far as my knowledge goes, this special structure occurs in many species of gomphine dragonflies which I have examined. It has ap- parently not been reported heretofore. Its function is not obvious to me. The distal end of the tibia is notched and somewhat socketlike and therefore fitted for the reception of the bulbous basal region of the basitarsus. The tarsus (TA) is 3-segmented; the basal segment or basitarsus (BTA) is the shortest; the distal segment or distitarsus (DTA) is the longest. The latter is about as long as the basitarsus and the middle segment taken together. Each segment is armed with a few spurs on its lateral margin. The distitarsus (DTA) bears a ventrodistal pro- jection, the plantella (PTL), which is well developed. The pretarsus (fig. 30) or terminal region of the leg consists of a pair of claws, empodium, and unguitractor. The claws (CL) are the largest parts of the pretarsus, and they articulate with a small dorsal process of the distitarsus. Each claw bears a ventral tooth and a narrow, wavy, ridgelike structure on each side of it. Ventrally the bases of the claws are connected with membrane which is also closely attached to the mesally located unguitractor. The unguitractor is a ventral sclerite which is partially hidden by the distal projection of the distitarsus, the plantella. An empodium (EMP) is attached to the distal end of the unguitractor. The distal portion of the empodium is enlarged. ABDOMEN (Figures 33-50) The abdomen is composed of Io distinct segments and, according to Tillyard (1917), also of the reduced remnants of the 11th and 12th segments. It is long and slender; the basal two segments tumid and slightly compressed, becoming thin, slender, and cylindrical from seg- ments 3 to 7 (more pronouncedly so in the male) ; dilated and de- pressed from the posterior half of segments 7 to 9 (more pronouncedly so in the male), widest across the apical end of segment 8; seg- ment 10 ringlike (in male) or depressed (in female). The propor- tional lengths of the segments from base to apex are approximately BS OMOWS:.1-65:4,5 30.02 7.0:.7.0: 6.5.5.5: 4:052:5 5 1.5. The male differs from the female in (1) having auricles (AU) on segment 2, (2) in having accessory sexual organs (figs. 40-44) on the ventral surfaces of segments 2 and 3, (3) the relatively great dilation of segments 7-9, and (4) the relatively great length of the anal appendages (figs. 45-50) at the extreme apex of the abdomen. 40 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 MALE TERGITES The tergites are convexly arched. They occupy not only the dorsal region but also the whole of the lateral regions of the segments. The lateral edges of the posterior half of tergite 3 and also of tergites 4-6 almost meet midventrally, partially hiding the sternites from view. With the exception of segments I and 10, the tergites are distinctly separated from the sternites by pleural membrane. Tergites 1 and 2 are weakly sclerotized middorsally ; 3-7 weakened along the midline; and 8-10 not so weakened. Tergites 3-7 are adorned with minute spines middorsally and also along the posterior transverse and sub- marginal ventral carinae. The dorsal spines are absent on the tergites of the other segments. Tergites 3-6 are similar to one another, while those of the other segments differ from the former in various ways. Tergite 4, to be described first, illustrates the generalized condition. TERGITE 4 is strengthened by the formation of both internal ridges and external carinae. Basally it is girdled by a submarginal antecostal suture (ACS), which is very narrow and usually obscured by the apical portion of the preceding tergite. Dorsally the tergite is weak- ened along its midline but, conversely, is strengthened by a supple- mentary transverse carina (SUTC) which is situated at a point one- fourth the distance from base to apex of the segment. Posteriorly it is strengthened by the submarginal posterior transverse carina (PTC) which is continuous with the submarginal ventral carinae (SVC), one on each side along the ventral margins of the tergite. The posterior transverse carina is conspicuous and adorned with small spines. The submarginal ventral carinae are poorly formed and weakly sclerotized. TERGITE I is separated from the sternite by narrow pleural mem- branes except anteriorly where it is fused with the latter. Dorsally it is adorned with a pair of tufts of long, fine hairs each on a slightly elevated subapical area. Lateroventrally the acrotergite (ATG) is enlarged and produced into a pouchlike evagination on each side. All carinae are absent except the submarginal ventral carinae (SVC) which are very poorly developed, with or without a few minute spines. TERGITE 2 is peculiar in having a pair of lateral outgrowths, the auricles (AU). These are situated in an oblique position on the ante- rior portion of the tergite, and are weakly sclerotized except along their crests, which are denticulate ventrally. The supplementary trans- verse carina (SUTC) is situated slightly anterior to the middle of the tergite and extends downward on each side posterior to the auricle. A similar but much shorter structure is present posterior to the sup- plementary transverse carina. The submarginal posterior transverse No. 6 MORPHOLOGY OF THE DRAGONFLY—CHAO AI VENTRAL VIEW, PENIS & RIGHT HAMULES REMOVED ANTERIOR LAMINA & HAMULES PENIS, LATERAL VIEW Fics. 40-44.—Basal abdominal segments and male accessory sexual organs. 42 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I22 carina (PTC) is more prominent dorsally than laterally. The sub- marginal ventral carinae (SVC) are adorned with long hairs anteri- orly and with spines posteriorly. TERGITE 7 (fig. 45) is peculiar in having the median area of the submarginal posterior transverse carina raised considerably and the submarginal ventral carinae dilated into leaflike structures, the pseudo- lateral dilations (PLD) (Fraser, 1934). TERGITE 8 (fig. 45) is peculiar in having a pair of submedian, low, rounded, transversely wrinkled tubercles. The supplementary trans- verse carina is absent. The submarginal posterior carina is raised medially where it is deeply notched. The submarginal ventral carinae are greatly expanded to form pseudolateral dilations. TERGITE 9 is similar to the preceding one except that (1) it is with- out submedian tubercles, (2) it is submedially slightly constricted on both sides, and (3) its submarginal posterior carina is slight notched medially. TERGITE 10 is completely fused with the sternite to form a ring. Dorsally it is deeply concave on its apical margin, with a pair of sub- basal, very low, ovoid, transversely wrinkled tubercles followed by dorsal wrinkles paralleling the edge of the apical concavity. All carinae are absent: the position of the submarginal posterior carina is indi- cated by a few small spines laterally. MALE STERNITES STERNITE I (fig. 40) is short, transversely rectangular, antero- laterally fused with the tergite. Posteriorly it is produced into two short processes which are inflected and obscured from view by the main portion of the sternite. These processes are connected with the anterior processes of the anterior lamina of sternite 2. Laterally the sternite has a pair of ovoid spiracles and a pair of small pits meso- posterior to the former. From these pits short hornlike apophyses are produced internally. Sternite 2 and the anterior portion of sternite 3 are greatly modified into complicated accessory sexual organs which are collectively known as the copulatory apparatus. The main structure of the apparatus con- sists of a penis which is lodged in a membranous depression, the genital fossa, and is protected by various organs derived from sternite 2. Different parts of the apparatus will be described in detail as follows. STERNITE 2 (figs. 40-43) is modified to form the following parts: genital fossa, anterior lamina, posterior lamina, supporting framework, sheath of the penis, anterior hamules, and posterior hamules. No. 6 MORPHOLOGY OF THE DRAGONFLY—CHAO 43 The genital fossa (GF) is a membranous depression strengthened by anterior lamina, posterior lamina, and lateral supporting frame- works. The sheath of the penis (SHP) is located on the posterior part of this membrane. The anterior lamina (AL) is a large sclerite, situated at the anterior third of the second abdominal segment. It is differentiated into dis- tinct anterior and posterior portions. The anterior portion is flat, comparatively weakly sclerotized, anteriorly produced into two proc- esses which are connected with similar processes of the preceding sternite. The posterior portion of the anterior lamina is strongly sclerotized, convex, and adorned with many minute tubercles and hairs. The posterior margin of the anterior lamina is V-shaped, irregularly indented, and with a short median cleft, the cleft of the anterior lamina (CAL). The posterior lamina (PL) is a large sclerite situated at the poste- rior end of the second abdominal segment. It is weakly sclerotized, constricted medially, and greatly expanded laterally. The supporting frameworks, or the anterior portions of the frame- works (APF) (Thompson, 1908) are a pair of sclerites on the lateral sides of the genital fossa between the anterior and the posterior laminae. Each is an elongate sclerite, slightly convex ventrally, with a subapical mesodorsal process which supports the base of the sheath of the penis (SHP). Ventrally the sclerite has a low transverse ridge to which the posterior margin of the base of the anterior hamule (AH) is attached. Posteriorly the sclerite is emarginated to form, together with the anterior extension of the posterior lamina (PL), a socket to which the posterior hamule (PH) is attached. The sheath of the penis (SHP) is a placoid structure composed of a scooplike structure arising ventrally from the base which is imbedded in the membranous genital fossa. The scoop is supposed to be for the protection of the penis. The base of the sheath is five-sided, medially with a broad shallow groove. The anterior margin of the base is articulated with and supported by the two arms of the paired support- ing frameworks. Each of the posterolateral angles of the base is con- nected with a small slender sclerite, the outer end of which is articu- lated with the posterior margin of the base of the posterior hamule. The anterior hamules (AH) each consists of a long bifurcated proc- ess produced ventrally from the posterior portion of an elongate sclerite which is attached to the low ridge of the supporting frame- work. Mesally it is attached to the lateral margin of the anterior lamina. The two processes are of unequal length, pointed apically. The anterior process is hooked apically, about twice as long as the posterior process, and is subequal in length to the stem. 44 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I22 Each of the posterior hamules (PH) is a robust structure attached to the socket formed by the supporting framework and the posterior lamina. It is about as long as the anterior hamule, pointed, with more bristles on its mesal surface and apex than elsewhere. TABLE 2.—Designations for the segments of the penis of anisopterous dragonflies ro 2 Williamson Kennedy Borror Fraser Present 5 (1920) (1922) (1942) (1940) author < Desmogomphus| Libellula Erythrodiplax | Gomphidae Onychogomphus DRAGONFLIES STUDIED ardens Vesicle Segment 1 | First or basal | Vesicle Vesicle segment Segment 1 Segment 2 | Second seg- Stem or first | Stem ment joint n | Segment 2 Segment 3 | Third seg- = ment Z Wee pee ale EAE ah be eels a Fourth or Median or Median seg- a terminal second ment segment joint Segment 3 (Elongation Glans or dis- | Distal segment of distal tal joint meatus of segment 3 STERNITE 3 is modified anteriorly into a penis and posteriorly into a long, narrow sclerite; the former is abutted to the truncated end of the latter. Anteriorly the narrow sclerite bears a large, round, internal, apodeme on each side. The penis (fig. 44) is a complicated organ consisting of several segments. Different designations for each of the segments of the penis of anisopterous dragonflies have been proposed by various taxonom- ists. A table is here given to show the different terminologies. Those terms used by Fraser (1940) in his paper on the penes of a large number of gomphine dragonflies are adopted in the present paper with a few modifications. The vEsIcLe (VS) is a robust structure, heavily sclerotized except for its dorsal surface which is membranous, having a small sclerite imbedded in its posterior portion. This sclerite is connected to the No. 6 MORPHOLOGY OF THE DRAGONFLY—CHAO 45 posterior extensions of the posterior lamina by a pair of small scler- ites. These slender sclerites apparently have not been recorded in the literature. When viewed ventrally (fig. 40) the vesicle is slightly constricted near the base, widened apically, slightly protruded on its apical angles, and with a short median cleft. The cavity of the vesicle is filled with fluid, and is continuous with those of the succeeding seg- ments of the penis, but not with the haemocoele of the abdomen. The latter fact is contrary to the opinion maintained by Kennedy (1922) and probably also by Borror (1942). The vesicle is an important organ in relation to the erection of the penis, but the exact role that it plays remains obscure. Kennedy (1922) mentioned that the cavity of the vesicle is continuous with the haemocoele of the abdomen, and that the erection of the penis is accomplished by forcing blood from the latter through the vesicle to the cavity in the apical segments of the penis. This opinion is adopted by Borror (1942) with modification. Fraser (1940) says that “when pressure is raised in the vesicle . . . the penis” is “at once erected.” But he does not mention how the pressure is raised in the vesicle. From the present studies it appears that the raising of pressure in the vesicle is accomplished by exerting a force on the small sclerite imbedded in the dorsal membrane of the vesicle. This contention is based on the observation that the cavity of the vesicle is not continuous with the haemocoele and that the wall of the vesicle is rigid except for the dorsal surface which is membranous. Thus a force exerted on the small sclerite imbedded in the membrane will depress the latter and force the fluid in the vesicle to flow into the apical segments so that the penis is erected. The stem (STEM) is L-shaped, attached to the dorsal membrane at the anterior end of the vesicle. Apically it bears a large round mem- brane which has a long narrow opening, the proximal meatus (PXM). The presence of this proximal meatus probably indicates that the stem is a composite segment, i.e., consisting of the second and the third segments of Borror (1942) fused together. This contention is based on the fact that (1) in Erythrodiplax and Libellula the proximal meatus is always present in a small and distinct segment, i.e., the third segment of Borror, and that (2) the apical limit of the preceding segment is indicated by the presence of a short dorsal spur (Kennedy, 1922), or knoblike protuberance (Borror, 1942). In gomphine drag- onflies this spur is absent in many species, such as shown by Fraser (1940), but present in some other species, e.g., Gomphus agricola, G. suzuki, Onychogomphus flexuosus, O. circularis, Megalogomphus hannyngtom, Progomphus pygmaeus, Cyclophylla signata, and Stylo- 46 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 gomphus inglisit. The latter fact indicates the distal limit of a segment proximal to the segment bearing the proximal meatus. The suture between these two segments is generally obliterated in gomphine dragonflies. The MEDIAN SEGMENT (MS) is short, perpendicular to the basal segment, and distally inflated. The inflated portion is weakly sclero- tized and bears a large lobe, the posterior lobe (PLB) (Kennedy, 1922; Borror, 1942), also called preputial fold or prepuse (Fraser, 1940). Anteriorly the median segment is medially grooved. Dorsally it bears a pair of very heavly sclerotized structures to which the bilobed distal segment (DS) is attached. The pISTAL SEGMENT (DS), or glans (Fraser, 1940), is bilobed. Each lobe bears a curled flagellum (Fraser, 1940) or cornua (CN) (Kennedy, 1922). The distal meatus is situated deeply between the two lobes. STERNITES 4 and 5 (see fig. 38, sternite V, 2) are elongate sclerites. Each is differentiated into an anterior subquadrate area followed by a long, narrow piece which is slightly constricted near the apex and ending in a small piece, the sternellum (STN) (Tillyard, 1917). Anteriorly the subquadrate area is produced into a pair of short proc- esses. At the four angles of the subquadrate area, the sternite is pro- duced internally and laterally into two pairs of sternal processes (STP) for the attachment of the segmental muscles. The anterior pair is small and linear and the posterior pair is fairly large and scalelike. STERNITE 6 (fig. 35) is similar to the preceding sternite except that its sternellum is enlarged apically. STERNITE 7 (fig. 35) is peculiar in that the anterior pair of sternal processes is very small, and the long piece following the subquadrate area is widened apically; without sternellum. STERNITE 8 (fig. 46) is a large sclerite, subtrapezoidal in shape, basally with a low median keel, and laterally slightly sinuate. STERNITE 9 (fig. 46) is sclerotized on its basal half and very weakly so on its apical half. The sclerotized portion is 4-lobed, two on each side of a pair of median ovoid sclerites, the valvules (VV), which, according to Tillyard (1917), are homologous with the lateral proc- esses of the ovipositor of the female. The valvules cover the male gemtal pore; the latter is guarded by a sclerotized ring. STERNITE 10 (fig. 46) is fused with the corresponding tergite. Its posterior margin is deeply emarginated. MORPHOLOGY OF THE DRAGONFLY—CHAO LATERAL VIEW,¢& Fics. 45-50.—Terminal abdominal segments. 47 48 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 SPIRACLES There are eight pairs of abdominal spiracles (SP). The first pair is situated in the first sternite, described previously. The next six pairs are situated in the pleural membranes near the posterior sternal proc- esses in each of the abdominal segments 2 to 7. They are ovoid in shape and oblique in position. The eighth pair is situated on the pleural membrane close to the middle of the lateral margins of the eighth sternite. It is almost twice as large as the other spiracles, elongate ovoid, and parallel to the long axis of the body. FEMALE TERGITES AND STERNITES The tergites of the female are fundamentally the same as those of the male, except for some sexual dimorphic characters mentioned be- fore. TERGITE Io (fig. 48) differs from that of the male in that dorsally it is not wrinkled nor tuberculate, and apically it forms a straight line instead of being deeply concave. Of the sternites, the first, fourth, fifth, and sixth are the same as in the males. STERNITE 2 (fig. 36) differs from the more generalized condition of the above in that it is rather wide, with the anterior transverse area bearing a pair of lateral sternal processes only. STER- NITE 3 (fig. 37) is similar to the generalized sternite except that the anterior and lateral processes are comparatively longer. STERNITE 7 (figs. 39, 47) is comparatively broad, with very small sternellum. STERNITE 8 (fig. 47) is large, elongate rectangular, laterally sinuate, basally with a low median keel, subapically with a low protuberance, and apically with a pair of subgenital plates (SGP) which are about two-fifths as long as sternite 9. The two sclerites of the subgenital plates are called valves (or vulvar scales, anterior processes) of the ovipositor, probably synonymous with some other terms such as ven- tral valves and first valvulae. STERNITE 9 (fig. 47) is broad, basally emarginate and separated from the preceding sternite by a large semi- circular membrane. The female genital pore is situated in this mem- brane and is covered by the subgenital plates. At a point one-third the distance from apex to base of the segment a low arc-shaped ridge is produced, which is apically bordered by a narrow membrane; the latter is constricted in the middle. This ridge might possibly be the remnant of the median process of the ovipositor (Tillyard, 1917) (also called inner valves or second valvulae). STERNITE Io is transversely rec- tangular, apically not emarginated as in the male. | | | No. 6 MORPHOLOGY OF THE DRAGONFLY—CHAO 49 END SEGMENTS The end segments, as used by Tillyard (1917), consist of various structures apical to the segment 10. These structures differ morpho- logically and phylogenetically in different suborders and in the two sexes. The following table shows their homologies (modified from Tillyard, 1917, p. 225). TABLE 3.—Occurrence and homologies of terminal abdominal structures Seg- eae Name of parts Male Female 10 | Tergite - | eresent Present Sternite Present Present Cercoids Superior anal appendages| Anal appendages 11 Tergite Rudimentary Median dorsal appendage Sternite Fairly large Fairly large (bipartite) Appendix dorsalis | Inferior anal appendages | Absent Cerci Absent Absent 12 Tergite Rudimentary Rudimentary Sternite (two Rudimentary Rudimentary laminae anales) In the male the superior and inferior anal appendages are very well developed. The suPERIOR ANAL APPENDAGES (SAP) are elongate, more than double the length of the segment Io, declined in their apical halves, slightly sinuate in dorsal view, and ventrally serrate at the apices. The INFERIOR ANAL APPENDAGES (IAP) is a bifid structure with its two branches slightly longer than the superior anal append- ages. Its base bends down vertically for a short distance and bears two apposing arms which curve upward gently toward their rather acute apices. Each branch of the inferior appendage has a minute dorsal subapical tooth and a fairly large, low, internal ridgelike tu- bercle just opposite the apex of the superior appendage; the tubercle being adorned with fine hairs. The remnants of the 11TH STERNITE (figs. 46, 50) are divided into two fairly large sclerites, collectively called the bipartite 11th sternite, situated along the ventral and lateral margins of the segment 10. The 12TH TERGITE and STERNITE are represented by superior and inferior anal laminae. Both are weakly sclerotized and adorned with minute hairs. The superior anal lamina (SPL) is attached to the anterior surface of the base of the inferior anal appendage. The inferior anal laminae (IFL) consist of two pieces, one attached to each of the bipartite sternites. The anal opening is situated at the bases of the anal laminae. 50 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 In the female the end segments are comparatively short, consisting of anal appendages, median dorsal appendage, and the remnants of the 11th and 12th segments. The ANAL APPENDAGES (AAP) are a pair of slender conical structures, situated laterally above the dorsal appendage, slightly longer than the roth tergite. The median dorsal appendage, or supra-anal plate (SPP), is a subsemicircular sclerite, convex above, about half as long as the anal appendages. The sB1- PARTITE IITH STERNITE (fig. 47) consists of a pair of fairly large sclerites which, when viewed ventrally, are triangular in shape. The remnants of the 12th tergite and sternite are represented by superior and inferior anal laminae. The former is weakly sclerotized, attached to the ventral surface of the median dorsal appendage. The inferior anal laminae (IFL) are bipartite, attached to the 11th sternite, and exceed the length of the latter. ABBREVIATIONS Aa, tornus AAP, anal appendage AAR, anterior mandibular articulation AAS, antealar sinus AB, anterior lobe of prothorax ACL, anteclypeus ACS, antecostal suture AES:, AESs:, mesothoracic or meta- thoracic anepisternum AH, anterior hamule AL, anterior lamina AN, adnotal sclerite AP2, APs, apodeme of detached plate of mesothoracic or meta- thoracic scutum APF, anterior portion of framework ARB, anterior rib of anterior tentorial arm arc, arculus ARG, antealar ridge at, anal triangle ATA, anterior tentorial arm ATG, acrotergite AU, auricle AWP, anterior wing process Ax:, Ax: primary antecostal cross veins 1AX, first axillary sclerite AXC, axillary cord AXP, axillary plate BA, basalare BCD, basicardo BCX, basicoxite BCXS, basicostal suture BH, brush BPL, basal plate br, bridge vein br.v., brace vein bs, basal space BS, basisternum BTA, basitarsus C, costal vein CAC, cleft of anterior lamina CAR, posterior mandibular articula- tion CEP, cephaliger CL, claw CN, cornua COL, collar CT, corporotentorium cu-a, cubito-anal cross vein CuP, posterior cubitus CX, coxa CXC, coxal cavity DC, dorsal cervical sclerite DCD, disticardo DCR, dorsal carina DS, distal segment of penis No. 6 DTA, dorsal tentorial arm DTP, dorsal tentorial pit DTTA, distitarsus EC, eucervicale EH, end hook EMP, empodium EPM, epimeron EPX, epipharynx ES, episternum ESR, epistomal ridge ESS, epistomal suture EYE, compound eye F, furca FE, femur FL, flagellum of antenna FM, foramen magnum FP, furcal pit FR, frons FS, furcasternum FT, flexor tendon of mandible G, gena GF, genital fossa h, hypertriangle HM, hypostoma HMS, hypostomal suture HP, humeral plate IAP, inferior anal appendage ICS, incisors IFL, inferior anal lamina IL, inner lobe IP, intermediary piece IPLA, interpleural apodeme | (=inter- segmental apodeme) IR», IRs, intercalary radial veins KEP, katepisternum LL, lateral lobe LR, labrum M, media MA, anterior median mb, membranule MB, median lobe of pronotum MD, mandible MDP, mandibular process MH, movable hook ML, middle lobe of labium MORPHOLOGY OF THE DRAGONFLY—CHAO 51 MLS, midlateral suture (=interseg- mental suture) MN, mentum MO, mola mr, midrib of anal loop in hind wing MRB, midrib of anterior tentorial arm MS, median segment of penis MSC, mesostigmatic lamina MX, maxilla MXP, maxillary process N, nodus NC, neural canal 0, oblique vein OC, ocellus OCC, occiput OCCD, occipital condyle OCCH, occipital horn OCCM, occipital margin OCS, ocular sclerite OL, outer lobe OS, ocular suture P, pedicel PA, papilla PB, posterior lobe of prothorax PC, postcervicale PCL, postclypeus PCX, postcoxale PF, prefurca PFS, parafrontal suture PFST, postfurcasternum PG, postgena PH, posterior hamule PL, posterior lamina PLA, pleural apodeme PLB, posterior lobe of penis PLD, pseudolateral dilation PLF, sternal fold PLS, pleural suture PM, pleurostoma PMS, pleurostomal suture POCC, postocciput POCS, postoccipital suture POS, postocellar suture PRA, prealare PRB, posterior rib of anterior tentorial arm PS, parastipes PSA, peristigmatic apodeme 52 SMITHSONIAN MISCELLANEOUS COLLECTIONS PSC, prescutum PSCL, postscutellum PSTN, pseudosternum Pt, pterostigma PTA, posterior tentorial arm PTAR, pretarsus PTC, posterior transverse carina PTL, plantella PTP, posterior tentorial pit PWP, posterior wing process PXM, proximal meatus R, radius ROOGC, rear of occiput Rs, radial sector RT, retractor tendon of mandible s, subtriangle S, scape SA, subalare SAG, subalar ridge SAL, salivarium SAP, superior anal appendage Sc, subcosta SCL, scutellum SCS, sternocostal suture SCT, scutum SG, sutural groove VOL. 122 SP, spiracle (ISP, IISP, mesothoracic and metathoracic spira- cles; SPs, SPs; etc, ab- dominal spiracles) SPD, spiracular dorsum SPL, superior anal lamina SPP, supra-anal plate SQ, squame of labium ST;, ST:, etc., abdominal sternites IST, IIST, mesosternum, metasternum STEM, stem of penis STI, stipes STN, sternellum STP, abdominal sternal process SUTC, supplementary transverse ca- rina SVC, submarginal ventral carina t, triangle T, tergite TA, tarsus TFR, top of frons TI, tibia TIC, tibial comb TN, squame of precostal apodeme TR, trochanter UT, unguitractor SGP, subgenital plate V, vertex SHP, sheath of penis VC, ventral cervical sclerite SM, submentum VS, vesicle sn, subnodus VV, valvula REFERENCES BERLESE, A. 1909. Gli insetti: loro organizzazione, sviluppo, abitudini e rapporti con l'uomo. I, Embriologia e Morfologia. x+1004 pp. Soc. Editrice Libraria, Milan. Borror, D. J. 1942. A revision of the libelluline genus Erythrodiplax (Odonata). Ohio State Univ. Contr. Zool. Ent. No. 4, biol. ser., xv-+213 pp., 41 pls. 1945. A key to the New World genera of Libellulidae (Odonata). Ann. Ent. Soc. Amer., vol. 38, No. 2, pp. 168-194, 72 figs. Butter, H. 1904. The labium of the Odonata. Trans. Amer. Ent. Soc., vol. 30, pp. III-134, 6 pls. CALvERT, P. P. 1893. North American Odonata. Trans. Amer. Ent. Soc., vol. 20, pp. 153- 268, 3 pls. No. 6 MORPHOLOGY OF THE DRAGONFLY—CHAO 53 Criark, H. W. 1940. The adult musculature of the anisopterous dragonfly thorax (Odonata, Anisoptera). Journ. Morph., vol. 67, pp. 523-565, 7 figs. Cow Ley, J. 1937. Tibial and femoral combs, and a trochanteral brush, in the Odonata. Proc. Roy. Ent. Soc. London (A), vol. 12, pp. 123-125, 4 figs. -Crampton, G. C. 1918. 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The terminal abdominal structures of female insects compared throughout the orders from the standpoint of phylogeny. Journ. New York Ent. Soc., vol. 37, pp. 453-496, pls. 9-16. 1932. A phylogenetic study of the head capsule in certain orthopteroid, psocid, hemipteroid and holometabolous insects. Bull. Brooklyn Ent. Soc., vol. 27, pp. 19-55, pls. 4-8. 1942. The external morphology of the Diptera. Guide to the insects of Connecticut. Part VI. The Diptera or true flies of Connecticut. Conn. Geol. Nat. Hist. Surv. Bull. No. 64, pp. 10-165, 14 pls. CREMER, E. 1934. Anatomische, reizphysiologische und histologische untersuchungen an der imaginalen und larvalen Flugmuskulatur der Odonaten. Zool. Jahrb., vol. 54, pp. 191-223, 24 figs. DuPorte, E. M. 1946. Observations on the morphology of the face in insects. Journ. Morph., vol. 79, pp. 371-417, 7 pls. Ferris, G. F. 1940. The morphology of Plega signata (Hagen) (Neuroptera: Manti- spidae). Microentomology, vol. 5, pt. 2, pp. 33-56, figs. 6-20. 1942a. Some observations on the head of insects. Microentomology, vol. 7, No. 2, pp. 25-62, figs. 10-27. 1942b. Some fundamental concepts in insect morphology. Microentomology, vol. 8, No. I, pp. 2-7. 1943. The basic materials of the insect cranium. Microentomology, vol. 8, No. 1, pp. 8-24, figs. 1-6, 54 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 1944. On certain evolutionary tendencies in the heads of insects. Micro- entomology, vol. 9, pp. 78-84. 1947. The contradictions of the insect head. Microentomology, vol. 12, No. 3, Pp. 59-82, figs. 23-29. Ferris, G. F., and PENNEBAKER, PHYLLIS. 1939. The morphology of Agulla adnixa (Hagen) (Neuroptera: Raphi- diidae). Microentomology, vol. 4, pt. 5, pp. 121-142, figs. 59-71. Ferris, G. F., and Ress, B. E. 1939. The morphology of Panorpa nuptialis Gerstaecker (Mecoptera: Panorpidae). Microentomology, vol. 4, No. 3, pp. 79-108, figs. 36-51. Forses, W. T. M. 1943. The origin of wings and venational types in insects. Amer. Midl. Nat., vol. 29, No. 2, pp. 381-405. Fraser, F. C. 1933. The fauna of British India, including Ceylon and Burma. Odonata, vol. 1, xiii+423 pp., I map, 180 figs. London. 1934. The fauna of British India, including Ceylon and Burma. Odonata, vol. Il. xxiii+398 pp., 4 pls., 120 figs. London. 1938. A note on the fallaciousness of the theory of pretracheation in the venation of Odonata. Proc. Roy. Ent. Soc. London (A), vol. 13, pp. 60-70, 3 figs. 1939. The evolution of the copulatory process in the order Odonata. Proc. Roy. Ent. Soc. London (A), vol. 14, pp. 125-129, 1 fig. 1940. Comparative-study of penes of Gomphidae. Trans. Roy. Ent. Soc. London, vol. 90, pp. 541-550, 1 fig., 6 pls. 1942. A note on the evolution of some venational structures in the dragon- fly wing. Proc. Roy. Ent. Soc. London (A), vol. 17, pp. 64-60, 2 figs. 1944. The significance of vestigial oblique vein in the evolution of inter- calated veins in the Odonata wing, with the description of a new genus. Proc. Roy. Ent. Soc. London (B), vol. 13, pp. 58-67, 5 figs. 1948. A new interpretation of the course of the subcostal vein in the wings of Odonata, with remarks on Zalessky’s notation. Proc. Roy. Ent. Soc. London (A), vol. 23, pp. 44-50, 2 figs. Garman, P. 1917. The Zygoptera or damsel flies of Illinois. Bull. Illinois State Lab. Nat. Hist., vol. 12, pp. 412-587, 15 pls. 1927. The Odonata or dragonflies of Connecticut. Guide to the insects of Connecticut. Part V. Conn. Geol. Nat. Hist. Surv. Bull. No. 30, Pp. 1-331, 67 text figs., 22 pls. Henry, L. M. 1948. The nervous system and the segmentation of the head in the Annulata. Microentomology, vol. 13, No. 2, pp. 27-48, figs. 10-16. Imos, A. D. f 1948. A general textbook of entomology. 7th ed. xii+757 pp., 624 figs. London. Kewnnepy, C. H. 1922. The morphology of the penis in the genus Libellula (Odonata). Ent. News, vol. 33, pp. 33-40, 2 pls. No. 6 MORPHOLOGY OF THE DRAGONFLY—CHAO 55 LAMEERE, A. 1922. Sur la nervation alaire des insectes. Bull. Acad. Sci. Roy. Belg., Bruxelles, vol. 5, No. 8, pp. 138-149. (English trans. in Psyche, vol. 30, pp. 123-132, 1923.) Lew, G. 1933. Head characters of Odonata. Ent. Amer., vol. 14, pp. 41-96, 12 pls. Lucas, W. J. 1923. Labium (second maxillae) of the Paraneuroptera (Odonata). Proc. S. London Ent. and Nat. Hist. Soc. 1922-23, pp. 57-63, 2 pls. MARSHALL, W. S. 1914. On the anatomy of the dragonfly Libellula quadrimaculata Linn. Trans. Wisconsin Acad. Sci., Arts, Lett., vol. 17, No. 2, pp. 775- 790, 4 pls. Montcome_ry, B. E. 1940. Discussion of leg characters in Odonata. Lloydia, vol. 3, pp. 259-278. MunscHeEnD, L. 1933. Die metamorphose der labiums der Odonaten. Zeitschr. Wiss. Zool., PP. 201-240, 44 figs. NEEDHAM, J. G. 1903. A genealogic study of dragonfly wing venation. Proc. U. S. Nat. Mus., vol. 26, pp. 703-764, pls. 31-54. 1930. A manual of the dragonflies of China. Zool. Sin., Ser. A, vol. 11, No. I, pp. 1-344, 20 pls. 1951. Prodrome for a manual of the dragonflies of North America, with extended comments on wing venation systems. Trans. Amer. Ent. Soc., vol. 77, pp. 21-62, 7 figs., 3 pls. NEEDHAM, J. G., and ANTHONY, MAupe H. 1903. The skewness of the thorax in Odonata. Journ. New York Ent. Soc., vol. II, pp. 117-124, 1 pl. NEEDHAM, J. G., and Haywoon, H. B. 1929. A handbook of the dragonflies of North America. viii-+378 pp., many figs. Springfield, Ill., and Baltimore, Md. RAmBvr, J. P. 1842. Histoire naturelle des insectes. Neuroptéres ... xvii+534 pp., 12 pls. Paris. St. Quentin, D. 1936. Der putzapparat der Odonaten. Zool. Anz., vol. 115, pp. 225-231, 2 figs. Snoperass, R. E. 1909. The thorax of insects and the articulation of the wings. Proc. U. S. Nat. Mus., vol. 36, pp. 511-595, pls. 40-60. 1927. Morphology and mechanism of the insect thorax. Smithsonian Misc. Coll., vol. 80, No. 1, pp. 1-108, 44 figs. 1930. How insects fly. Ann. Rep. Smithsonian Inst., 1929, pp. 383-421, 25 figs. 1935. Principles of insect morphology. 667 pp., 319 figs. New York. 1947. The insect cranium and the “epicranial suture.” Smithsonian Misc. Coll., vol. 107, No. 7, pp. 1-52, figs. 1-15. 56 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 Soka, R. R. 1947. The anatomy of the head capsule of the dragonfly Pantala flavescens Fabricius (Anisoptera: Odonata). Musée Heude. Notes Ent. Chinoise, vol. 11, fasc. 6, pp. 157-223, 5 pls. STRICKLAND, E. H. 1946. Odonata as class-room material. Ann. Ent. Soc. Amer., vol. 30, No. 1, pp. 28-32. Tuompson, O. S. 1908. Appendages of the second abdominal segment of male dragonflies (Odonata). New York State Educ. Dept. Mus. Bull., vol. 124, PP. 249-263. TILLYARD, R. J. 1917. The biology of dragonflies. xii+306 pp., 4 pls. Cambridge Univ. Press. 1922. New researches upon the problem of the wing venation of Odonata. Ent. News, vol. 33, pp. I-7, 45-51, I pl., 3 figs. 1926. Insects of Australia and New Zealand. xi+560 pp., 44 pls. Sydney. TILLyarD, R. J., and Fraser, F. C. 1938. A reclassification of the order Odonata based on some new inter- pretations of the venation of the dragonfly wing. Austr. Zool., vol. 9, pp. 125-160, 27 figs. 1939. Ibid., pp. 195-221, 11 figs. 1940. Ibid., pp. 359-396, 15 figs. Wuepon, A. D. 1918. Comparative morphology and possible adaptations of the abdomen in the Odonata. Trans. Amer. Ent. Soc., vol. 44, pp. 373-437, 9 pls. 1927. The structure and transformation of the labium of Anax junius. Biol. Bull., vol. 53, No. 4, pp. 286-296, 2 pls. 1938. The aortic diverticula of the Odonata. Journ. Morph., vol. 63, No. 2, Pp. 239-261, 6 pls. WILLIAMSON, E. B. 1920. A new gomphine genus from British Guiana with a note on the classification of the subfamily (order Odonata). Occ. Pap. Mus. Zool., Univ. Michigan, No. 80, pp. 1-11, 1 pl. GRY tee As “SMITHSONIAN MISCELLANEOUS COLLECTIONS VOLUME 122, NUMBER 7 epates D. and #lary aux Walcott Research Fund x THE GEOLOGY OF CHACO CANYON Po NEW-MEXICO * . IN RELATION TO THE LIFE AND REMAINS | (OF Lee PREHISTORIC PEOPLES OF - PUEBLO BONITO (WitH 11 PLatEs) © a ey od, : BY GU: eae KIRK BRYAN Roa Bs | ; RP | iy ah hd ih folie . ' ~eeeeeee (Pustication 4140) . ‘CITY OF WASHINGTON We x PUBLISHED BY THE SMITHSONIAN INSTITUTION ds _ FEBRUARY iy, 1954 anil Pol SUQAR }] 7 7B fALOATOSOI SJ[LIoyJeA, JO JUOUTyUeqUIO 9} I aLV1g He Le ae ee ” x lay : la ae fawfe. SD ae tag et _ y ~ we 4 . ~4 vr. “ - - SMITHSONIAN MISCELLANEOUS COLLECTIONS VOLUME 122, NUMBER 7 Charles D. and Mary Waux CHalcott Research F und fine AG OLOGY OF CHACO’ CANYON, NEW MEXICO IN RELATION TO THE LIFE AND REMAINS OR iiae PReristORIC: PEOPLES OF PUEBLO BONITO (Wit 11 PLates) BY KIRK BRYAN (PusticaTion 4140) CITY OF WASHINGTON PUBLISHED BY THE SMITHSONIAN INSTITUTION FEBRUARY 2, 1954 The Lord Baltimore Press BALTIMORE, MD., U. 8. A. FOREWORD The geology of Chaco Canyon in relation to its prehistoric inhabit- ants was a subject that greatly interested Kirk Bryan. Born and schooled in New Mexico, he had seen hundreds of ruined Pueblo villages, mostly abandoned before advent of the Spaniards in 1540, and had given much thought to the reasons behind their desertion. Warfare may have been one cause but it obviously was not the only one, A geologist with the United States Geological Survey and engaged primarily in a study of groundwater resources of the Southwest, Dr. Bryan seemed to us especially qualified to seek out the factors that had invited, and then repelled, colonization of Chaco Canyon in the days of Pueblo Bonito. He accepted with enthusiasm our invitation to un- dertake this study but was able to devote only two brief vacation pe- riods to field work, in the midsummers of 1924 and 1925. His observa- tions in Chaco Canyon, admittedly incomplete, prompted like inquiries in other valleys during the decade that followed. In 1926 Dr. Bryan left the Geological Survey to accept a call from Harvard University, and thereafter academic commitments and sum- mers in the field allowed him but little leisure. In consequence, he never found an opportunity to finish this report on his Chaco Canyon researches. A first draft, dated March 1925, and written before his second visit to the canyon, was repeatedly revised and expanded as his continuing investigations annually provided new data. He appears to have made no change in the text after 1940. For these several rea- sons some sections of the report lack references to the more recent literature. Following Dr. Bryan’s untimely death in the summer of 1950, his unfinished manuscript was forwarded to me by Mrs. Bryan. I have undertaken to arrange its several parts in conformity with his original table of contents and to eliminate repetitions of subject matter and phraseology. The various stratigraphic columns Bryan examined and the course he plotted for an arroyo more or less contemporary with the decline of Pueblo Bonito are shown on the accompanying map of Chaco Canyon. Stratigraphic sections 10 to 23 were studied in 1925, but we have descriptions for numbers 15 and 17 only, and a third, without number but adequately located in relation to the expedition’s camp. lil iv FOREWORD Test pit No. 3, about midway between camp and the west refuse mound, was among those I had caused to be dug in 1922 in connec- tion with an analysis of Chaco Canyon soils. When it was deepened three years later at Bryan’s request and was found to penetrate the buried channel he was then trying to isolate, a common impulse was to extend the exploratory trench we had previously dug through the west refuse mound and thus reveal the original surface between buried channel and the old village dump. Pit No. 4, dug expressly for Dr. Bryan, was so named because of its proximity to his section 4, where the buried channel stood exposed near the southeast corner of Pueblo del Arroyo. Thus test pits 3 and 4 and the extended west-mound trench enabled Bryan to plot the course of that prehistoric arroyo as it passed Pueblo Bonito, and led to his search for traces of it as far east as Pueblo Wejegi. The extent of this ancient channel, together with evidence of alternating periods of erosion and sedimentation, formed the basis for Bryan’s growing conviction that a slight change in climate was the most likely cause for disruption and dispersal of the Chaco Canyon population in the early twelfth century. His con- clusion is certain to exert a profound influence upon future interpre- tation of past history in the Southwest. I gladly acknowledge our obligation to Mrs. Kirk Bryan and to two of Dr. Bryan’s former students, Dr. John T. Hack and Dr. Luna B. Leopold, both of the United States Geological Survey, for their coop- eration in the preparation of this report. Two members of my Pueblo Bonito staff, O. C. Havens and Lynn C. Hammond, and several of our Zufi workmen assisted Dr. Bryan in Chaco Canyon. The illustra- tions are mostly from photographs by Mr. Havens. It was originally intended that this paper appear as fourth in the series reporting the results of the National Geographic Society’s Pueblo Bonito Expeditions. But the series was discontinued after the first number, “Dating Pueblo Bonito and Other Ruins of the South- west,” by Dr. A. E. Douglass (1935). Early in 1953 the Society made the present manuscript available to the Smithsonian Institution, which proposed to publish it under the Charles D. and Mary Vaux Walcott Research Fund. The life and achievements of Dr. Kirk Bryan are briefly reviewed by Frederick Johnson in American Antiquity, vol. 13, No. 3, p. 253, January 1951. NeiL M. Jupp. Leader of the National Geographic Society's Pueblo Bonito Expeditions. Washington, D. C. June 1953. CONTENTS Page LORE WOLC ye chee aie ceca yore Hes IN Siete cRetame oun oh dl nehraye ctoubuchind bey abuiees ter steiatete ili IEA PTCA ELON rate ter ake ow ese iacad custaveye esioheaiaiois ete oA MNED shevatele opstetoieny © relakerarets I ATMO MEMEO DON Geico aisle w overaie ekohs wiarete opie avatay ohels llevan Shararslalavencicnate lay aierate 2 hy siockanhy sors Chacon Gatiyionkracvateyc seis oxsters ctor eletevers ere ole) atte iesaiel olekans/ovsaks 3 Generale ations: tiene ieccie oi uovsi bates ele) dele ssciekods ats chats arora wnuateieye 3 Climatic conditions affecting geologic processeS..........-.2.eeeeee 4 Excavation or Chacon Cany Oi. .veypcpeyeret atcusrotsietel ieieelel< ersisveeiedee) s.ietsyspale 8 Adluviationcol the Canyon MOOG saree ercte actos eke sislers sisiclsie Sine sieges ier eters II Waterob necenti Stream Chem hit eye ek fesyare TN aksceys revel esi orevare) holereue as 4 stencbote 15 IP resentececolOsiciprOoCeSSeShisisa cis ss leatoiintels mis cleiclatevele Gis alain. diaiel shaele « citlebelprs 18 Wreathernmne rand erosionvon die Clittstiar stale seis levereere nelalelaie see «e's 18 Vitro eoy Ot leas esse. t 8) oes ava ciety eh nclciecct aber bore rapa vaiaatiate Cision ene aia Marth Shia, § Opals 21 PNA tayidlli aM Sees iye ssc re catelelayek s eecete les diove oe ctaters ho ceiabriees Cheat c wea eaaieeae cholate 22 PAILS RELESIO NL AE Ly eis Plale m iteic bey yee Ab cla! aCalel ga alk bide eluniore ateiove weblrar sidan 23 EOSTOMPIMat eva ht OY Orjas eins acoice sunt cleterevoreisy Ateuswh air ecorers ha ereisrey sisi sevens eiets 23 Mhesvalleysalllivitme ss mets /o tee cae rao ete oye le arco ae ieee Sate Slotiagin che 23 Material shobethne efile yi rcstetedtarcterc nireterenst oa enon om eee Merce as ott at eal et lee 23 Acrancementrot thematerial sie ves ccs eieters tect siete deeln's aemania ale Sete 25 PI COERNGTT EN ANIVID 2G crak mi teverc ce Aalst ns wile Vaalt Miele omeiars a Hades 25 Euman elses) imythenval ley itil lecterievaters ohaiceys ol Puebio Lit fireplace: at SehHOm 5 ines... signe atiaesvwsees eenivla ves 10 Vi LIST OF ILLUSTRATIONS EESGavadavVViasit.we tres a hc tra are eee mre ia kan cane a Rem 2 ae Lower : 5. Upper: Lower: 6. Upper: Lower: 7. Upper: Lower : 8. Upper: Lower: 9. Upper: Lower: 10. Upper: Lower: 11. Left: Pit house below nearby Pueblo III ruin Right: Pueblo I pot in sand dune “Stonelace’\ on, detached! block oki... saan avcie sees po meie Looking down Chaco Canyon from Pueblo del Arroyo Recently fallen. arroyo bail. '. 5 Ssiv.te opiyeis era be eis oxosverla esate Small-house ruin, destroyed by floods........5....eeccececees Pueblo: Tpit) Rouse list). 2. os aes os bale 2 be aise Ghee eee Buried channel at section 16 Busiedichannelvati section: Ace a.ceiee oem seen ae ee Mouth \of Rincon del. Caminoiwsnwsss% 1.4% silos ode coe eee Lateral erosion caused by drainage from The Gap............ Skeleton 6 feet below surface... .io0i fon. fo vei conde dca ese bee Hearth at depth of 12 feet 8 inches Horses crossing thes@hacosinifood4..> cess ee seek week os oe Middle south wall of Pueblo del Arroyo eee eee ee CY ey ar Ce ee Cc FIGURES 1. Map of Chaco Canyon showing present and post-Bonito channels...... 2 Northwest portion onuNews Mexicosmcm. se embinace seen ee ee eeie Zu Banl< or Chaco between Sections: sandy lO etraer ies sake eee eee ier Page 4. Upper: Niches and dunes, north wall of Chaco Canyon, near mouth of 10 Io Charles D. and Mary Waux Walcott Research Fund TH, GEOLOGY OB; CHACO. CANYON NEW MEXICO IN RELATION TO THE LIFE AND REMAINS OF THE PREHISTORIC PEOPLES OF PUEBLO BONETO By KIRK BRYAN? (WirTa 11 PLaATEs) INTRODUCTION On the initiative of Neil M. Judd, leader of the National Geographic Society’s Pueblo Bonito Expeditions, and on the recommendation of Dr. John C. Merriam, then president of the Carnegie Institution of Washington, the present writer was selected to undertake an inquiry into the geologic history of Chaco Canyon. Two brief periods were devoted to field work: July 28 to August 9, 1924, and July 10 to August 1, 1925. In the well-ordered camp of the expedition he was received with gracious hospitality, and to all members of the staff he owes much in kindness. Mr. Judd placed every facility at his dis- posal including a number of excavations especially designed to bring to light geologic facts and thus expedite the investigation. Application of the stratigraphic methods of geology to archeologi- cal problems is no longer new, and knowledge of these methods forms a part of the equipment of every modern archeologist. Our inquiry into Chaco Canyon geology has proved (1) that the alluvial deposits of the canyon carry various relics of prehistoric peoples and (2) that the deposits can be separated into divisions of differing age. In recent years knowledge of these generalizations has become widespread and additional data have been gathered. It appears that we are now on the brink of establishing in the Southwest an alluvial chronology based on a sequence of episodes of erosion and alluviation. This sequence of geologic events gives a key to the fluctuations of climate of late geo- logic time and yields a proximate cause for the sudden decay of the great Pueblo communities of the San Juan country. (Bryan, 1941.) 1 Dr. Bryan died on August 23, 1950. SMITHSONIAN MISCELLANEOUS COLLECTIONS, VOL. 122, NO. 7 i) SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 Previous work on the general geology of this region is referred to hereinafter. During the summers of 1899 and Igor, Prof. Richard E. Dodge made a geological survey of Chaco Canyon as part of the ex- tensive plans for the Hyde Exploring Expedition. His work was done after archeological excavation had ceased, and, unfortunately, his re- sults were published only in skeleton outline in the report of the ex- pedition (Pepper, 1920, pp. 23-25) and in three abstracts (Dodge, 1902a, 1902b, 1910). Even so, these brief sketches record a number of observations of interest that are referred to in the following pages. They indicate that Professor Dodge was on the verge of discovery and, with more archeological help, the geological theory herein set forth would doubtless have been advanced by him 20 years earlier. The 1877 observations of W. H. Jackson (1878) were keen and penetrat- ing, and from exposures no longer visible he made the original dis- covery of the buried channel whose description and interpretation form such a large part of this report. The long delay between initiation of this study and its publication has not been without advantage. During the interval we have learned that the geologic history of Chaco Canyon is not unique. Other valleys have similar histories, as will appear from the data on these other val- leys summarized hereinafter. Generalizations on the cause of the alternations from erosion to alluviation and on the effect of these events on human affairs now rest upon a foundation of fact much larger than would have been possible in 1924 and 1925. PLAN OF "THE REPORT This Chaco Canyon study was begun as an isolated project. It was an attempt to relate recent geology to the life of prehistoric peoples in the area. The results proved so successful, however, that other studies were subsequently undertaken. The alternate periods of allu- viation and erosion discovered in Chaco Canyon and related to the tree-ring dates of Douglass (1935) have been found in other local- ities. The periods of alluviation are, so far as evidence now exists, nearly synchronous over the whole Southwest. Thus there has been developed an alluvial chronology still imperfect but valuable as a meas- ure of time in the dating of archeological events. It is presumably still more valuable as a measure of alternating periods favorable or un- favorable to floodwater farming, an important method of agriculture in the area. Still more important are the inferences on fluctuations in climate parallel with alternations in the regime of streams. The report begins with a general consideration of the area and its = iz - _ a j ¥ eae he TENET hone — wo erwin ¥ VERON A aad he i pes eaten e ats cy a i canny al ial a eee Wren | - <= Se o oie ~~ = eee S = & a = : * Plie _ Ray! sy ; ; jen.: op an 7 7 a —— WH he a CENTRAL PORTION CHACO CANY' ON NATIONAL MONUMENT HOWING THE LOCATION OF PUEBLO BONITO STE AE \ / NN iS<\ We. \ Ye 7 ‘PUEBLO BONITO EXPEDITIONS GNE ; & r A Nh - { ak OF THE _ > \ e “NATIONAL GEOGRAPHIC SOCIETY ‘AN Topography by Robert P Anderson =\4 1922 —s () e YZ (SM ANOS SRS = We us TT oe YA . BY) | 2 WEL \ UY TUNG a a\: Za , \ FROM SURVEYS BY THE t 4 2 a i Contour Interval 20 feet » Navaho Hogans o Ancient Ruins DRAWN BY JAMES M DARLEY Fic. 1.—The buried, or post-Bonito, channel in relation to the present arroyo in Chaco Canyon. NOW 7, GEOLOGY OF CHACO CANYON—BRYAN 3 climate, with such information as is available on the age of the present arroyo in Chaco Canyon, with rather detailed studies of geologic proc- esses now current there, and a description of the alluvium of the valley floor. It then presents evidence that this alluvium is divisible into three parts: the terrace, the main valley fill, and the post-Bonito channel. The antiquity of these divisions and their correlation with similar alluvial formations elsewhere are also considered. The im- portance of floodwater farming in the Southwest and the effect of the recent epicycle of erosion on this type of agriculture are next set forth. The cause of the alternation from alluviation to erosion in south- western valleys is next discussed and the argument advanced that simultaneous alternations in the regimes of widely separated streams must be due to synchronous climatic changes. The concurrent effects of climatic change and change in stream regime throughout the known human history of the Southwest affords a clue to fluctuations in human culture otherwise unattainable. PHYSIOGRAPHY OF CHACO CANYON GENERAL RELATIONS Chaco Canyon lies in northwestern New Mexico on the upper reaches of Chaco River, a tributary of San Juan River (fig. 1). Chaco River, about 100 miles long, is an ephemeral stream such as is char- acteristic of arid regions. Its sandy bed throughout the greater part of the year is dry and the stream is dignified by the name of river only because of its considerable length and the violence of its floods. The stream begins in the high plains country north of Chacra Mesa at an altitude of 6,900 feet and flows a little north of west for 68 miles. Here the course changes sharply to the north and the river flows nearly parallel to, and on the east side of, the ridge known as the Grand Hog- back for 26 miles and thence, breaking through the Hogback in a narrow canyon, it reaches San Juan River in 7 miles. The total length of the stream is thus about 100 miles, of which, however, only 15 or 20 miles of the upper course lies in a canyon worthy of the name. About 12 miles of this canyon, the portion with which we are con- cerned, is shown on the accompanying map (fig. 1). Chaco Canyon lies in the southwestern part of the great Plateau province which occupies northwestern New Mexico, northern Arizona, western Colorado, and eastern Utah. The province is noted for its extensive flat surfaces, long lines of cliffs, and deep canyons. The flat surfaces are in part developed on the more resistant beds of nearly horizontal sedimentary rocks, although in part they consist of large 4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 outflows of lava, and in part they are the remnants of extensive plains of erosion. In northwestern New Mexico the largest unit of the Pla- teau province is the San Juan Basin, a vast area in which the rocks dip gently from the periphery toward the center. Chaco Canyon lies near the southern part of this area with a dip of about 2° to the north and east. Sandstone and shale are the characteristic rocks. The shale is eroded into broad, flat surfaces or gently sloping valleys ; the sandstone stands out as ridges or plateaus, bounded, especially on the south, by cliffs. The order and succession of these rocks have been studied by a num- ber of geologists * interested primarily in the occurrence of coal or of vertebrate fossils. Chaco Canyon is cut in the Cliff House sandstone, the upper mem- ber of the Mesaverde group. This sandstone member is 369 feet thick as measured by Reeside on Meyers Creek, a few miles northwest of Pueblo Bonito. It is underlain by dark shale containing thin sandstone and coal (Menefee formation) which crops out in the cliffs on the south side of Chaco Canyon and in a few places on the north side. The Mesaverde group is overlain by the Lewis shale which forms the plain north of Pueblo Alto and has a thickness of about 70 feet. Above the Lewis shale lie the Pictured Cliff sandstone and higher formations. The Cliff House sandstone consists of two massive sandstones sepa- rated by relatively thin bedded sandstone. Consequently, weathering tends to produce two cliffs separated by a bench of gentler slope. The lower of these two massive sandstones is buff-colored and about 140 feet thick. The cliffs which make the northern wall of Chaco Canyon are carved from this rock by processes considered more in detail on pages 18-20. CLIMATIC CONDITIONS AFFECTING GEOLOGIC PROCESSES The climate of the Chaco country is arid, but such a simple state- ment does not adequately summarize the effect of climate on the geo- logic processes. Aridity has many gradations from the almost total lack of rainfall characteristic of parts of the Libyan desert of Africa, and of certain areas on the west coast of Peru, to the tempered aridity of California where trees and grass thrive in areas having relatively low rainfall. Aridity is thus an inclusive term embracing climates having varying amounts of precipitation up to a quantity fixed arbi- 2 Holmes, 1877; Endlich, 1877; Schrader, 1906; Shaler, 1907; Gardner, 1909; Sinclair and Granger, 1914; Matthew, 1897; Brown, 1910; Bauer, 1917; Bauer and Reeside, 1921; Reeside, 1924. NO. 7 GEOLOGY OF CHACO CANYON—BRYAN 5 trarily around 20 inches of rainfall a year. The many shadings and gradations of aridity are dependent on such factors as the propor- tion of the precipitation that may occur as rain or as snow, on the dis- tribution of precipitation throughout the year, and on the incidence of rainfall whether in hard showers or gentle drizzles. Similarly the daily or seasonal range of temperature and the extremes of heat and cold with their incidence and duration are all factors in aridity. Climatic elements directly affect various subprocesses involved in the weathering of rocks and indirectly influence the nature of streams which act as the agents of removal and of transportation of weathered rock. Slight differences in degree of aridity often have marked in- fluence in the growth of a vegetative cover, one of the greatest single factors influencing and delimiting erosive and sedimentary processes. In the account of these processes given hereinafter it will be seen that the scant vegetation of an arid region is a necessary prerequisite to the relative intensity of action, or even the existence, of many of the sub- processes. It follows, therefore, that any past or anticipated climatic change, provided it is sufficient to alter the existing vegetation, may have relatively large effect on geologic processes. The available rainfall records of the Navaho Country up to the end of 1913 were collected by Gregory (1916, pp. 51-59) and the factors of climate in Chaco Canyon are now being recorded by the National Park Service. Herein only such general elements of climate are de- scribed as seem necessary for the purpose of defining climate in respect to geologic processes. The climate of the Plateau province may be considered moderately arid. On the higher portion, between the valleys of San Juan River and the Little Colorado, there is greater precipitation than in the low- lands. In the mountains doubtless as much as 20 inches may fall each year, but current rainfall stations are all on lower ground. St. Mi- chaels, Ariz., altitude about 6,950 feet, has a mean of 13.72 inches based on records for 29 years out of a period of 68 years; Crown- point, altitude 6,800 feet, has 10.93 inches, based on an incomplete record extending over 11 years. At lower elevations, especially to the north and south of Chaco Canyon, the precipitation is less. Holbrook, Ariz., altitude 5,069 feet, has 9.38 inches with 25 years of record out of a total of 33 years. Places in the San Juan Valley have a lower rainfall: Fruitland, N. Mex., altitude 4,800 feet, 6.38 inches with 7 years of record; Farmington, N. Mex., altitude 5,220 feet, 9.23 inches with 7 years of record; Aneth, Utah, altitude about 4,700 feet, 4.96 inches. It seems likely the Chaco Canyon district has a precipitation similar to that at Crownpoint with a little less rainfall on the floor of 6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 the canyon which is 300 to 400 feet lower than the adjacent cliffs. For the purpose of this study it will be assumed that Chaco Canyon has a mean of about 10 inches. A large part of this precipitation falls during the so-called summer rainy season in July and August. This period is characterized by sharp local or general rains from cumulus clouds or thunderheads. The rate of rainfall is high but the storms seldom last long. The incidence of the rains is also variable in time and space. Small areas are deluged and adjacent areas are left dry. The rains may come as early as June or as late as September, or may be inconsiderable in amount for a whole summer. Gregory (1916, p. 63) summarizes many observations as follows: The area covered by a shower is frequently only a few square miles, and on two occasions showers of 20 to 30 minutes’ duration resulted in wetting less than 300 acres. Many of the showers result in a heavy downpour, and the total precipitation for a month is not infrequently the result of a single shower... . Generally the intense heat preceding a shower is reestablished within an hour or two after rain has ceased, especially at elevations below 6,000 feet. . . . Light- ning is the almost invariable accompaniment of summer showers and constitutes a real danger to travel... . My records of thunderstorms for the Navaho Reservation during the field seasons 1909, I910, 1911, and 1913 are 38, 26, 33, and 23, respectively, and it is believed that the annual number exceeds 40. The winter precipitation falls gently and is likely to be widely spaced in time, but on the average totals nearly as much as the summer rain- fall. At elevations above 6,000 feet there are 17 to 25 inches of snow, and at lower elevations some snow is possible each winter. The distribution of precipitation throughout the year and its effect on agriculture is best expressed in the following table compiled by Gregory and amplified in a quotation also from him (ibid., pp. 61-62) : Precipitation in percent of mean Season Months rainfall STMIM|EHA Vateitatene chre.s trrereters July, August, “September: 2... 2.0 aparece oe 37 Early witteg rae ses cena October, November, December.............. 25 Water wintel, £2) shai, s\s, «> z O 8 o PA MAL ATAU MEULE © § clots wis sich sis, sta Sieigs Sep eSyesio cian ec cts stal< I 2 9 2 RMD cig hice cid cratatal a: sneha c/s iflava to al ute cva les teesees I 5 10 7 Sand! and!silt tovbotton Of arroyo’). ol. sii.) «1-1-1211 3 ) 14 2 56 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 Section 8 South bank of main arroyo 2 miles east of Wejegi and outside the area of our map. Thickness Depth a Feet Inches Feet Inches Darleclaies aise srapstes aiellersia ey stotoae ue phate teemacrst ea 2 ) 2 fe) Laminated and crossbedded sand with a few lenses of gravel. At depth of to ft. 4 in. there is a streak of charcoal resting on burnt (red) earth; at 13 ft. 2 in., a second streak of char- coal, directly below the first but no red earth; scattered charcoal occurs to depth of 21 ft..... 25 4 27 4 Covered below. Section 9 In arroyo of Rincon del Camino, about 300 feet south of the road and in the fan of the rincon. Thickness Depth Oo FF Feet Inches Feet Inches Compact rusty sandy clay with fragments of stone and charcoal; potsherds at 6 ft. 3 in..... 6 3 6 3 Crossbedded sand with impressions of plant stems and scattered charcoal to depth of 14 ft. 8 in. At depth of 12 ft. 8 in. there is a hearth cres- centic in section and consisting of baked and reddened floor 2 ft. I in. across and rising 3 in. at the ends with layer of charcoal from 4 to 14 in. thick. South 50 ft. from this section, scattered charcoal occurs to a depth of 16 ft. Sil. froma top .Or bam ese cise. we elon Be ke} 0) 19 3 Section not numbered North bank of main arroyo west of 1924 dump. [South of the Wetherill corrals and 100 yards, more or less, west of the expedition camp.—N. M. J.] Thickness Depth 7) =< Feet Inches Feet Inches Apparently uniform indurated sand mixed with adobe and ta: little silt .c..ct.cvteenmnetes bicas e melee 6 ) 6 te) Laminated clay interbedded with slightly in- durated sand. Fine interbeddings well defined and nearly parallel. Lower 0.7 ft. has broader Deprratitnve chet eevsrevescts, eros ancieheve ec tateteteretercteme oriole cre ete 2 7 8 Indurated sand laminated without adobe........ I 6 10 I Fine white sand slightly indurated and finely Devtrirmrtedo.: rsievs seratyrenaveleveretecscakeavargienarel stetouelle teranads I 0) II I NO. 7 GEOLOGY OF CHACO CANYON—BRYAN 57 Thickness Depth Feet Inches Feet Inches Nonlaminated clayey sand, indurated........... (a) 5 II 6 White sand slightly and inconspicuously lami- RUE PPP ey of chet yay eh facie Ca. aioi ote) leaistails loyaileiavatele rs ans Bialats 0 9 12 3 Well-indurated inconspicuously laminated sand with large content of fine silt or clay......... 2 8 14 II Gray sand slightly laminated and indurated..... 2 8 17 7 Clay containing sand and showing tendency to granulate and fissure on shrinkage (adobe).... 2 8 20 3 Fine nonlaminated sand slightly indurated....... I 2 21 5 Clay containing some sand and showing tendency to granulate and fissure on shrinkage......... 2 7 24 (a) Pulverant loamy sand containing minute black EEA tMeMtS: |(IOISE) crests ahs aleyarela de chet intel cies 3 0 27 0 Section 15 In middle of buried channel, on south bank of main arroyo and 200 yards upstream from mouth of Rincon del Camino. Thickness Depth Feet Inches Feet Inches Alternate bands of sandy clay with internal ChaCksr anlGucOmMmactySafld enisictes cis sieiele iokee oie rs 4 0 4 (0) MOIRA ACL SAM tists au lrecchs Wtcinlalslersitvetareis' «tise ho 6 I 7 5 7 Sandy clay with internal cracks and streaks of COMIPACE SAN ys Croversyesa eis wlel wisi elel ce ws sro leratata tatoo ove I 2 6 9 Minutely crossbedded compact sand with a few lenses of clay 3 to 4 ft. long near base........ 3 4 10) I Crossbedded compact sand with lense of gravel 1 ft. thick and 4 ft. long at base, containing burnt sandstone blocks up to 6 in. across, clay pellets, blocks of clay, and potsherds of late type, base of buried channell.................-. 3 (0) 13 I Crossbedded sand, crossbedding on larger scale, streaks of pieces of black shale and coal...... 2 3 15 4 Compactycrossbeddedisandeas- a..c cscs co essa ae 2 7 17 II GOVeredmr ies yam rlcie testes ere See ee ree ole Altay 5 O 22 II Section 17 At the mouth of Rincon del Camino a narrow point projects into the main arroyo from the north. On the east face of this point a well- defined buried channel is exposed. Section 17 was measured in the middle of this exposure. Thickness Depth =a SSS Feet Inches Feet Inches Yellow pulverant sand derived from Rincon del ROAMING Sch avseyeee as BO OO RE CECB eee (a) 6 (0) 6 58 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 Thickness Depth Feet Inches Feet Inches Sandy. clay -with internal) cracks.:'....664. .cstsis ee I (o) I 6 Yellow pulverant sand derived from Rincon del CAMAGeh Ss oes cece eas adenine Sates ee eR I 4 2 10 Sandy clay with internal cracks contains sand lense ‘to South Of SECtiONs snrcleiers o's:0 2 5 14 3 NO. 7 GEOLOGY OF CHACO CANYON—BRYAN 59 Materials found Thickness Depth Found at Feet Inches Feet Inches Potsherds Feet Inches PEATE CLAY sco ci die's bivie ave resiesse te) / 14 10 Laminated and minutely crossbedded coarse sand. This bed grades to south into gravelly clay that ex- 16 I tends to depth of 16 ft. Io in....... I 5 16 3 Many to DSS (OER GAG Ma aa eC Peed Se O 5 16 8 16 8 PEIN aia aha'v ails wis, od ath linia erate co) 2 16 10) Gravelly clay containing large and small stones, grades into sand to 17 3 SUEUR etree a fovn miele aie eva eisacer sists I 5 18 3 Numerous to EGUITEMS TACOS hice oye cooks a ete cterac clevettceteree fo) 3 18 6 18 3 Log of test pit number 4 Sixty feet east from arroyo bank at section 4 Materials found Thickness Depth Found at Feet Inches Feet Inches Potsherds Feet Inches Gray-brown sandy clay (adobe).... 1 10 I 10 Laminated sandy adobe, a lense.... 0 z 2 ) Hard brown sand with pieces of char- EOE Se cura Sis SRN rien oes a cane 2 2 4 2 Brown sand in part finely laminated with lenticular streaks of dark laminated clay 4 to 1 in. thick and spaced 2 to Io in. apart........... 3 3 z 5 \“Oneonly “7 ) “c “cc 7 2 Hard brown sand, containing at north end of pit an irregular lense of sandy and gravelly adobe con- taining charcoal and bones....... 2 5 9 10 Many 9 6 Dark sandy clay (adobe) with small : 10 6 HGMSEU OL STAVE! se ole lisld Sad.cuw e's SOCET | 7 14 5 Many in to gravel 10 II 6 Many to II 8 Sand (a lense) that extends to 15 ft. Ae northend OF Pit. \ysisc seis ae eee (a) 3 14 8 mdobe to bottom: Of pit. dele. 6s (a) 9 15 5 Many 15 (a) SUMMARY Chaco River, a river only during occasional floods, entrenched itself at some past time, doubtless Pleistocene, in a broad plain that then existed in the San Juan Basin of northwestern New Mexico. In the nearly horizontal sandstones and shales that underlie San Juan Basin, 60 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 the Chaco River flows, when it flows at all, alternately in broad valleys and narrow canyons. To one of these latter the name Chaco Canyon is applied almost exclusively, and here, in a stretch of about 12 miles, there are numerous ruins of prehistoric villages, the largest of which is Pueblo Bonito. Chaco Canyon, after its excavation, was partly refilled with sand and silt during a period of alluviation common to most streams of the southwestern United States. On the flat floor of the canyon, result- ing from this alluviation, the prehistoric peoples lived and left evidence of their long-time occupation in hearths, scattered charcoal, potsherds, and other relics. These remains extend to a depth of 21 feet below the present surface of the alluvium. An ancient type of dwelling known as a pit house has been found at a depth of 6 feet below the surface, but the typical Pueblo III type of construction has not been surely identified below 4 feet. Alluviation in Chaco Canyon and generally throughout the South- west has more recently been interrupted by the formation of an arroyo or steep-sided gully in which the floods of the stream are now wholly confined. The Chaco Canyon arroyo is presently 20 to 30 feet deep and from 150 to 400 feet wide, yet a military expedition of 1849 did not mention the gully, if it then existed. In 1877 an arroyo 16 feet deep and 60 to 100 feet wide was reported. Available evidence indi- cates that the arroyos of other streams were mostly formed in the decade 1880 to 1890 and that the process is still going on. The begin- ning of the Chaco arroyo appears to have been somewhat earlier and the date may, with some assurance, be placed in the decade 1860 to 1870. A study of the deposits that make up the valley fill indicates that Chaco River never had a permanent low-water flow. No signs of irri- gation ditches or other diversions of flowing water have been found in the alluvial deposits. It seems probable, therefore, that the prehis- toric inhabitants of the canyon practiced floodwater farming, a form of agriculture still in use in the region. For this type of farming wide-spreading floods are a prerequisite, and the beginning of erosion, with formation of an arroyo that confines the floods and lowers the water table, puts an end to agriculture of this type. The main body of the valley fill is of unknown depth. Only the upper 30 feet is exposed and of this the uppermost 21 feet contains relics of man. Pottery made by the ancient people varies in texture and design according to locality and age. Differences between the kinds of pottery typical of different stages in human culture are not wholly known, nor has a definite chronology of the stages been deter- NOI GEOLOGY OF CHACO CANYON—BRYAN 61 mined, but broad distinctions can be made between the older and younger civilizations. Collections of potsherds can therefore be used as fossils in studying the stratigraphy of the valley alluvium. Generally, only a few pot- sherds are found at any one place and many of these are indeterminate, hence of no diagnostic value. Somewhat meager collections of sherds from depths of 6 to 21 feet have been examined by the expedition’s archeologists who identify them as mostly a coarse ware characteris- tic of the Pit House culture. On the basis of these fragments, there- fore, we may draw the inference that people of the Pit House period were the principal inhabitants of Chaco Canyon during the time required for deposition of those 15 feet of alluvium. Potsherds collected from the zone of valley fill less than 6 feet below the surface are generally of Pueblo III type. This fact, together with ruins whose foundations are partly buried in alluvium, indicate that Pueblo III people occupied the valley during the period represented by the last 6 feet of alluviation. In the bank of the arroyo near Pueblo del Arroyo there is exposed a buried channel which extends to a depth of 15 feet below the pres- ent surface. At this point the channel is a well-defined ancient arroyo that had been refilled and then buried under an additional 2 feet of sediment in the interval between abandonment of Pueblo Bonito and American Army penetration of Chaco Canyon in 1849. Potsherds removed from the gravel lenses of that buried channel included frag- ments of the latest Pueblo Bonito types. The channel, therefore, must have been refilled late in the occupancy of Pueblo Bonito or after its abandonment. By means of test pits in which similar pottery was found, we traced this buried channel for about 1,000 feet across the plain fronting Pueblo Bonito and later discovered remnants of it both up and down the canyon. This buried channel clearly represents a period of dissec- tion and arroyo formation for the full length of the valley and, assum- ing that the dissection occurred late in the occupancy of Pueblo Bonito, an adequate cause exists for abandonment of the canyon by aboriginal farmers whose floodwater fields were destroyed by confinement of the floods within this channel, and by concurrent events. Our examination of the main valley fill suggests alternate dissection and alluviation of Chaco Canyon: three periods of dissection and two of alluviation. If this alternation represents a true cycle, we may expect the present arroyo to run its course and then be refilled and perhaps covered over. However plausible it may be to attribute forma- tion of the present arroyo to destruction of the vegetative cover by 62 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 overgrazing, the previous dissection and subsequent alluviation were in no way affected by domestic animals. It seems probable, therefore, that the ultimate cause of this periodic change in the regime of streams is climatic. A slightly increased rainfall would increase the vegetative cover and thereby both reduce the violence of floods and protect the soil from erosion. Any decrease in rainfall would produce a reversed effect. Although the deposits of Chaco Canyon contain no definite evidence of a more humid climate during the two periods of their deposition, it seems likely that an increased humidity did exist and was a factor in development of the distinctive Chaco culture. The sub- sequent change to more arid conditions was doubtless of less effect until it culminated in formation of the twelfth-century arroyo that unexpectedly became a dominant feature of this study. BIBLIOGRAPHY BAvER, CLYDE Max. 1917. Stratigraphy of a part of the Chaco River Valley. U. S. Geol. Surv. Prof, Pap. 98, pp. 271-278. BAvER, CLlypDE MAx, and REEsSIDE, JOHN B., Jr. 1921. Coal in the middle and eastern parts of San Juan County, New Mexico. U. S. Geol. Surv. Bull. 716, pp. 155-237. Brown, BARNUM. 1910. The Cretaceous Ojo Alamo beds of New Mexico, with description of the new dinosaur genus Kritosaurus. Bull. Amer. Mus. Nat. Hist., vol. 28, pp. 267-274. Bryan, Kirk. 1920. Origin of rock tanks and charcos. Amer. Journ. Sci., ser. 4, vol. 50, pp. 188-206. 1923a. Erosion and sedimentation in the Papago country, Arizona, with a sketch of the geology. U. S. Geol. Surv. Bull. 730, pp. 19-90. 1923b. Ground water in Quinn River and Paradise Valleys, Nevada. U. S. Geol. Surv. press notice, Jan. 29, 1923. 1925a. Date of channel trenching (arroyo cutting) in the arid Southwest. Science, n.s., vol. 62, No. 1607, pp. 338-344. 1925b. The Papago country, Arizona—a geographic, geologic, and hydrologic reconnaissance, with a guide to desert watering places. U. S. Geol. Surv. Water-Supply Pap. 499. 1926a. Recent deposits of Chaco Canyon, New Mexico, in relation to the life of the prehistoric peoples of Pueblo Bonito. (Abstr.) Journ. Wash- ington Acad. Sci., vol. 16, No. 3, pp. 75-76. 1926b. Channel erosion of the Rio Salado, Socorro County, New Mexico. U. S. Geol. Surv. Bull. 790A, pp. 17-19. 1928a. Historic evidence on changes in the channel of Rio Puerco, a tribu- tary of the Rio Grande in New Mexico. Journ. Geol., vol. 36, No. 3, pp. 265-282. 1928b. Change in plant associations by change in ground water level. Ecology, vol. 9, No. 4, pp. 474-478. NO. 7 GEOLOGY OF CHACO CANYON—BRYAN 63 1928c. Niches and other cavities in sandstone at Chaco Canyon, N. M. Zeitschr. Geomorph., vol. 3, pp. 125-140. Leipzig. 1929. Flood-water farming. Geogr. Rev., vol. 19, pp. 444-456. 1941. Pre-Columbian agriculture in the Southwest as conditioned by periods of alluviation. Ann. Assoc. Amer. Geogr., vol. 31, No. 4, pp. 219- 242. Bryan, Kirk, and McCann, FRANKLIN T. 1936. Successive pediments and terraces of the Upper Rio Puerco in New Mexico. Journ. Geol., vol. 44, No. 2, pt. 1, pp. 145-172. Davis, W. M. 1903. An excursion to the Plateau province of Utah and Arizona. Bull. Mus. Comp. Zool., Harvard Coll., vol. 42, pp. 1-50. Donce, RicHArp E. 1902a. An interesting landslide in the Chaco Canyon, New Nexico. Science, n.s., vol. 15, p. 746. 1902b. Arroyo formation. Science, n.s., vol. 15, p. 746. 1910. The formation of arroyos in adobe-filled valleys in the southwestern United States. (Abstr.) Rep. British Assoc. Adv. Sci., vol. 79, PP. 531-532. 1920. See Pepper, George H. Dovetass, A. E. 1924. Some aspects of the use of the annual rings of trees in climatic study. Ann. Rep. Smithsonian Inst. for 1922, pp. 223-239. 1935. Dating Pueblo Bonito and other ruins of the Southwest. Nat. Geogr. Soc., Contr. Techn. Pap., Pueblo Bonito Ser., No. 1. Duce, JAMES TERRY. 1918. The effect of cattle on the erosion of canyon bottoms. Science, n.s., vol. 47, pp. 450-452. Dutton, C. E. 1882. Tertiary history of the Grand Canyon district. U. S. Geol. Surv. Monogr., No. 2. Enpiicu, F. M. 1877. Geological report on the Southeastern district. 9th Ann. Rep. U. S. Geol. and Geogr. Surv. Terr. for the year 1875, pp. 103-235. GARDNER, J. H. 1909. The coal field between Gallina and Raton Spring, New Mexico, in the San Juan coal region. U. S. Geol. Surv. Bull. 341, pp. 335-351. Grecory, H. E. 1915. The oasis of Tuba, Arizona. Ann. Assoc. Amer. Geogr., vol. 5, Pp. 107-119. 1916. The Navajo country: A geographic and hydrographic reconnaissance of parts of Arizona, New Mexico, and Utah. U. S. Geol. Surv. Water-Supply Pap. 380. 1917. Geology of the Navajo country: A reconnaissance of parts of Ari- zona, New Mexico, and Utah. U. S. Geol. Surv. Prof. Pap. 93. Hack, Joun T. 1942. The changing physical environment of the Hopi Indians of Arizona. Pap. Peabody Mus. Amer. Archaeol. and Ethnol., Harvard Univ., vol. 35, No. 1. 64 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 Hoimes, W. H. 1877. Geological report on the San Juan district. 9th Ann. Rep. U. S. Geol. and Geogr. Surv. Terr. for the year 1875, pp. 237-276. Hoover, J. W. 1929. The Indian country of southern Arizona. Geogr. Rev., vol. 19, No. 1, pp. 38-60. 1930. Tusayan: The Hopi country of Arizona. Geogr. Rev., vol. 20, pp. 425-444. HuNTINGTON, ELLSworrtu. 1914. The climatic factor as illustrated in arid America. Carnegie Inst. Washington Publ. 192. Jackson, W. H. 1878. Report on the ancient ruins examined in 1877. 1toth Ann. Rep. U. S. Geol. and Geogr. Surv. Terr. for the year 1876, Chaco Canyon, PP. 431-450. Jupp, Nei M. 1924. Two Chaco Canyon pit houses. Ann. Rep. Smithsonian Inst. for 1922, PP. 399-413. Loew, Oscar. 1879. Report on the ruins in New Mexico. Report upon U. S. geographical surveys west of the 1ooth meridian (Wheeler Surveys), vol. 7, Pp. 337-345. (Abstr. from Ann. Rep. Chief of Engineers for 1875, App. LL, Sect. J-2, pp. 174-178.) LuMHOLTZ, Kart SoFus. 1912. New trails in Mexico. New York. MaAtTTHEw, W. D. 1897. A revision of the Puerco fauna. PP. 259-323. Morrison, C. C. Amer. Mus. Nat. Hist. Bull. 9, 1879. Notice of the Pueblo Pintado and of other ruins in the Chaco Canyon. Report upon U. S. geographical surveys west of the rooth meridian (Wheeler Surveys), vol. 7, pp. 366-369. (Abstr. from Ann. Rep. Chief of Engineers for 1876, App. JJ, Sect. E, pp. 359-360.) Netson, N. C. 1914. Pueblo ruins of the Galisteo Basin, New Mexico. Anthrop. Pap. Amer. Mus. Nat. Hist., vol. 15, pt. I, pp. 1-124. OLmstTED, FRANK HENRY. 1919. Gila River flood control: Report on flood control of Gila River in Graham County, Arizona. Dep. Interior, 65th Cong., 3d Sess., Senate Doc. 436. Pepper, Grorce H. 1920. Pueblo Bonito. Anthrop. Pap. Amer. Mus. Nat. Hist., vol. 27. REAGAN, ALBERT B. 1922. Archaeological notes on Pine River valley, Colorado, and the Kayenta- Tuba region, Arizona. Trans. Kansas Acad. Sci., vol. 30, pp. 244- 331, 394-429. 1924a. Recent changes in the Plateau region. Science, n.s., vol. 60, pp. 283- 285. 1924b. Stream aggradation through irrigation. Pan-Amer. Geol., vol. 42, PP. 335-344. NO. 7 GEOLOGY OF CHACO CANYON—BRYAN 65 REEsIDE, J. B., Jr. 1924. Upper Cretaceous and Tertiary formations of the western part of the San Juan Basin, Colorado and New Mexico. U. S. Geol. Surv. Protpeapwisa: Ricu, Joun Lyon. ro1r. Recent stream trenching in the semi-arid portion of southwestern New Mexico, a result of removal of vegetative cover. Amer. Journ. Sci., ser. 4, vol. 32, pp. 237-245. Rosinson, H. H. 1907. The Tertiary peneplain of the Plateau district and adjacent country in Arizona and New Mexico. Amer. Journ. Sci., ser. 4, vol. 24, pp. 109-120. Scurapver, F. C. 1906. The Durango-Gallup coal field of Colorado and New Mexico. U. S. Geol. Surv. Bull. 285, pp. 241-258. SENTER, DoNovVAN. 1937. Floor deposition and erosion in Chaco Canyon. Univ. New Mexico Bull. No. 308, App. I, pp. 134-139. SHALER, MILvarp K. 1907. A reconnaissance of the western part of the Durango-Gallup coal field of Colorado and New Mexico. U. S. Geol. Surv. Bull. 316, Pp. 376-426. Stmpson, JAMES H. 1850. Journal of a military reconnaissance from Santa Fe, New Mexico, to the Navajo country ... in 1849. Rep. Secretary of War, 31st Cong., ist Sess., Senate Ex. Doc. No. 64, pp. 56-168. Srnciair, W. J., and GRANGER, WALTER. 1914. Paleocene deposits of the San Juan Basin, New Mexico. Bull. Amer. Mus. Nat. Hist., vol. 33, pp. 207-316. Situ, G. E. P. 1910. Ground water supply and irrigation in the Rillito Valley. Univ. Arizona Agr. Exp. Stat. Bull. No. 64, pp. 98-99. THORNBER, J. J. 1910. The grazing ranges of Arizona. Univ. Arizona Agr. Exp. Stat. Bull. No. 65, pp. 335-338. WILLIAMS, GEORGE O. 1925. Radium-bearing silts of southeastern Utah. Eng. and Min. Journ. Press, vol. 119, pp. 201-202. sama a 1a" Fee ; Thai ve i all ae A ry ie ai tet) Oye NES eat ean th . : ee ea nie 4 bee if i ne ‘ ; ae ; : rie SMe | Hytoet + i 4 RE ale ay cata dae ea - Pike ” ; a) , ih A Wee Carle ath WY Fidos oe wer j sages / \ re. a ig Fl Ange NY rr SMITHSONIAN MISCELLANEOUS COLLECTIONS VOLUME 122, NUMBER 8 Ser tieR ADDITIONS TO THE BIRDS OF PANAMA AND COLOMBIA BY, ALEXANDER WETMORE Research Associate, Smithsonian Institution eS FEMA Regs \e) Ol ie) sen < ee ANor 0, (PusicaTion 4142) CITY OF WASHINGTON PUBLISHED BY THE SMITHSONIAN INSTITUTION DECEMBER 17, 1953 The Lord Baltimore Press BALTIMORE, MD., U. & J. FURTHER ADDITIONS TO THE BIRDS OF PANAMA AND COLOMBIA By ALEXANDER WETMORE Research Associate, Smithsonian Institution During work of recent months on our extensive collections of birds from Panama and northern Colombia, several hitherto unrecognized forms have been found that merit description to give better under- standing of the geographic variation in the species concerned. With these I have included records of three others that have not been re- ported previously from Colombia. Family CRACIDAE ORTALIS RUFICRISSA LAMPROPHONIA, new subspecies Characters—Similar to Ortalis ruficrissa ruficrissa (Sclater and Salvin)? but smaller; feet smaller; tail shorter; lower breast and abdomen whiter ; back and wings more grayish brown. Description—Male adult, U.S.N.M. No. 368535, from the Serrania de Macuire, above Nazaret, Guajira, Colombia, collected May 5, 1941, by A. Wetmore and M. A. Carriker, Jr. (orig. No. 11792). Crown chaetura drab, feathers of forehead edged with a wash of light olive- gray; ear coverts drab; remainder of side of head mouse gray, the feathers with fuscous shafts ; hindneck deep mouse gray, shading into the color of the upper back ; upper back and wings between olive-brown and deep olive ; rump and upper tail coverts slightly darker than buffy brown; primaries light olive-brown, with a slight grayish wash on outer webs; central rectrices deep olive, tipped indefinitely with buffy brown; outer rectrices dark greenish olive (slightly iridescent) , tipped widely with white ; foreneck and sides of neck light grayish olive with a slight brownish wash; multiple line of feather shafts, extending longitudinally down center of bare throat, black, becoming fuscous where they merge with upper portion of feathered foreneck ; webs of 1 Ortalida ruficrissa Sclater and Salvin, Proc. Zool. Soc. London, November 1870, p. 538 (Valledupar, Magdalena, Colombia). SMITHSONIAN MISCELLANEOUS COLLECTIONS, VOL. 122, NO. 8 2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 feathers bordering bare throat pale smoke gray; lower breast and upper abdomen white, washed with pinkish buff on upper portion of breast, this buffy wash extending down onto the sides; flanks and under tail coverts tawny ; tibiae pinkish buff to cinnamon-buff ; under wing coverts with outer half light grayish olive, inner half clay color. Tip of bill horn color; rest of distal half castor gray; basal half neutral gray ; tarsus and toes fuscous; claws drab (from dried skin). Range——The Serrania de Macuire, at the eastern end of the Guajira Peninsula, Colombia. Measurements—Males (2 specimens): Wing 195-202 (198), tail 227-235 (230), culmen from base 25.7-27.2 (26.4), tarsus 64.0-65.4 (64.7) mm. Females (2 specimens): Wing 195-200 (197), tail 217 (in both), culmen from base 25.8-26.0 (25.9), tarsus 59.5-62.3 (60.9) mm. Type, male: Wing 202, tail 235, culmen from base 27.2, tarsus 65.4 mm. Remarks.—Ortalis ruficrissa ruficrissa, named many years ago by Sclater and Salvin from Valledupar, was known prior to our work in northeastern Colombia from two specimens, the type in the British Museum and one from Dibulla on the north coast, about 35 miles west of Riohacha, in the Carnegie Museum. We found it first at Maicao, Guajira, and later Carriker secured a series that extend the range of the typical race from the western Guajira at Maicao, into northeastern Magdalena, from La Cueva in the eastern foothills of the Sierra Nevada de Santa Marta southward, along the western base of the Sierra de Perija, to Casacara. This excellent series is sufficient to demonstrate the distinctness of the isolated colony on the Serrania de Macuire, which is cut off by many miles of barren desert, where there is no suitable habitat for these birds, from the more-forested section of the western Guajira inhabited by Ortalis ruficrissa ruficrissa. Measurements of the typical race are as follows: Males (7 specimens): Wing 206-238 (217), tail 240-272 (253), culmen from base 26.0-29.8 (27.8, average of 6), tarsus 64.0-73.1 (69.2) mm. Females (5 specimens) : Wing 196-217 (205), tail 230-253 (239), culmen from base 26.0-28.2 (26.7), tarsus 62.0-67.0 (64.1, average of 4) mm. In the series of ruficrissa there is one bird in somewhat worn plumage, from Camperucho, Magdalena, that is as white on the breast as the four lamprophonia, but it has the upper breast and fore- neck and the dorsal surface darker, the feet larger, and the tail defi- nitely longer. no. 8 BIRDS OF PANAMA AND COLOMBIA—WETMORE 3 The name for the new race is given because of the raucous voice that carries for long distances. Family BUCCONIDAE NONNULA FRONTALIS STULTA, new subspecies Characters.—Similar to Nonnula frontalis frontalis (Sclater),? but somewhat grayer, less rufescent above; crown duller brown; averag- ing very slightly duller brown on breast and foreneck. Description—Type, U.S.N.M. No. 445077, male, El Uracillo, Province of Coclé, Panama, February 23, 1952, A. Wetmore and W. M. Perrygo (orig. No. 16946). Forehead, sides of head extend- ing to area above eye, and including the lores and erectile feathers above the anterior end of the eye, gray (dark gull gray) ; anterior portion of crown between verona brown and warm sepia, shading to bister on nape; rest of upper surface, including wings and tail, sepia, with wing coverts, primaries, and secondaries edged lightly with Saccardo’s umber, and the ends of the rectrices shading to clove brown ; outermost rectrix drab, the second pair edged externally and tipped rather widely with drab, the others with the drab less exten- sive; extreme base of the feathers on chin at the base of the bill white; throat, foreneck, and breast between cinnamon and _ sayal brown; flanks clay color ; abdomen whitish ; under tail coverts white ; edge of wing cinnamon; under wing coverts tawny-olive ; inner webs of secondaries and inner primaries cinnamon-buff. Bill, tarsus, and toes blackish slate (from dried skin). Measurements.—Males (12 specimens): Wing 55.2-58.8 (57.1), tail 52.3-58.7 (55.1), culmen from base 22.3-24.8 (23.5), tarsus 13.0-14.7 (13.6) mm. Females (17 specimens): Wing 55.1-62.0 (58.1), tail 53.6-59.6 (57.1), culmen from base 22.4-25.6 (24.0), tarsus 12.2-14.2 (12.6) mm. Type, male: Wing 55.7, tail 54.8, culmen from base 23.7, tarsus 13.5 mm. Range.—Panama from northeastern Coclé (El Uracillo) and the Canal Zone (Lion Hill) through eastern Province of Panama (Tocu- men, Pacora, Chepo), through Darién (Jesucito, Rio Esnape, El Real, El Tigre, Boca de Cupe, Capeti, Cana) to extreme northern Choco (Acandi), Colombia. Found mainly on the Pacific slope. 2 Malacoptila frontalis P. L. Sclater, Ann. Mag. Nat. Hist., ser. 2, vol. 13, 1854, Pp. 479 (interior of Colombia). 4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I22 Remarks.—This attractive little bird, while somewhat more active than the larger members of its family, shares with them the habit of resting quietly for long periods. I have found it in brushy areas or low down in tracts of gallery forest. In the main, in Panama it ranges on the Pacific slope, thus far having been found in the Carib- bean drainage near the head of canoe navigation on the Rio Indio in northern Coclé, at Lion Hill (before the Panama Canal was con- structed), and at Acandi, Colombia, on the western shore of the Gulf of Uraba. Specimens from Unguia, Choco, on the western side of the lower Rio Atrato, are N. f. pallescens. This species has two color phases, one rufescent, in which the dorsal surface is decidedly brown and where brown extends over the entire ventral side except the center of the abdomen and the lower tail coverts, and the other grayish, where the lower surface especially is paler, with the white of the abdomen more extensive. Nonnula f. stulta differs from pallescens of extreme northern Colombia in being darker colored and also duller brown, less rufescent, above. Family TROCHILIDAE COELIGENA ORINA, new species Characters —Similar to Coeligena bonapartei (Boissoneau)* but crown uniform, without frontal spot ; body color uniform dark green, without bronzy sheen on lower breast, under tail coverts and rump; under tail coverts uniform green, without cinnamon edgings; tail dark green without bronzy reflections ; wings dull black (not fuscous) ; spot on foreneck decidedly brighter blue; under wing coverts darker green ; bill more slender. Description—Type, U.S.N.M. No. 436219, male adult, Paramo de Frontino, at 10,500 feet, Antioquia, Colombia, August 27, 1951, col- lected by M. A. Carriker, Jr. (orig. No. 21016). Feathers of crown, sides of head, and hindneck iridescent elm green, margined with black, the green being evident clearly only when viewed at an appropriate angle; back, and lesser and middle wing coverts iridescent spinach green ; rump and upper tail coverts strongly iridescent, varying from lettuce green to Cosse green ; remiges and greater wing coverts aniline black, with a faint violet-purple sheen, the inner greater coverts edged with shining lettuce green; outer primary margined lightly on external web with avellaneous ; rectrices iridescent yellowish oil green, with lightly indicated edgings of dull black; chin chaetura black; 3 Ornismia bonarpartei [sic] Boissoneau, Rev. Zool., 1840, p. 6 (Bogota). no. 8 BIRDS OF PANAMA AND COLOMBIA—-WETMORE 5 foreneck and upper breast iridescent spinach green, the feathers margined lightly with black; a spot of glittering salvia blue on fore- neck ; lower breast, sides, flanks, and under tail coverts shining lettuce green; center of abdomen, in a small area, dull white; tibiae cinna- mon-buff ; under wing coverts iridescent elm green. Bill black, toes fuscous, claws black (from dried skin). Measurements.—Male, type: Wing 75.2, tail 44.0, culmen from base 33.6 mm. Range.—Known only from the Paramo de Frontino at 10,500 feet, above Urrao, Antioquia, Colombia. Remarks.—The single male seen appears closer to Coeligena bona- partei than to others of the genus, and apparently is a representative of that group in the western Andes. It is so different, however, that I have no doubt as to its being a distinct species. The specimen appears fully adult, so that absence of the frontal spot may not be ascribed to immaturity. Compared to C. bonapartei the bill, in addi- tion to being more slender, is longer. This is one of the handsomest of the novelties obtained during the present ornithological exploration of Colombia. Carriker noted on the label that the bird was taken in forest below the open paramo. Family TYRANNIDAE MYIARCHUS FEROX AUDENS, new subspecies Characters.—Similar to Myiarchus ferox panamensis Lawrence * but grayer above, with the crown more nearly uniform with the back ; slightly paler yellow below. Description—tType, U.S.N.M. No. 443502, female, Nuqui, Choco, Colombia, collected on March 5, 1951, by M. A. Carriker, Jr. (orig. No. 19780). Crown and auricular area between hair brown and deep grayish olive, with an indefinite wash of chaetura drab on central portion along shafts; neck, back, lesser wing coverts, and upper tail coverts slightly darker than deep grayish olive; rump grayish olive ; middle and greater wing coverts chaetura drab, tipped rather widely with grayish olive to produce two indistinct wing bars; primary coverts, primaries, secondaries, and rectrices chaetura drab; sec- ondaries margined prominently and inner primaries lightly with dull white; outer rectrix with outer web dull buffy brown, the others edged with grayish olive, more prominently at the base, all tipped lightly with a wash of olive-buff; lores, and an indistinct line above 4 Myiarchus panamensis Lawrence, Ann. Lyc. Nat. Hist. New York, vol. 7, May 1860, p. 284 (Atlantic slope of Canal Zone on the Panama Railroad). 6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 eye pale olive-gray ; a mixture of dull white immediately in front of eye, with whitish feathers extending back over the lower eyelid ; chin indistinctly whitish; throat, foreneck, and upper breast light olive- gray, lined indistinctly with dull white on throat and upper foreneck ; lower breast and abdomen chartreuse yellow; sides and under tail coverts sea-foam yellow; edge of wing and under wing coverts be- tween Marguerite yellow and primrose yellow; inner webs of pri- maries and secondaries pale olive-buff toward base. Bill, tarsus, and feet dull black (from dried skin). Measurements——Female (3 specimens): Wing 86.0-91.1 (89.4), tail 78.2-86.4 (83.3), culmen from base 20.2-21.6 (20.8), tarsus 21.8- 22.7 \(22.2 jem. Type, female: Wing 91.1, tail 86.4, culmen from base 21.6, tarsus 22.7 cin: Range.—Known only from near Nuqui, Department of Choco, northwestern Colombia. Remarks.—The three skins on which this new race is based have been compared with a large series of M. f. panamensis covering the area from western Panama across northern Colombia. They stand out clearly from all in the definitely gray coloration. The nearest specimens of panamensis seen are from Jaqué, Darién, across the border in Panama, and from Nicocli and Villa Artiaga, Antioquia, in Colombia. It is probable that the new race ranges immediately back of the beaches along the coast, as the species as a whole does not penetrate into heavy forests such as are found inland in the Choco. Its distribution, therefore, may be through a relatively narrow belt, east and west. It is pertinent to add here that Myiarchus ferox australis Hellmayr is also to be included in the list of birds found in Colombia, as shown by a male in the U. S. National Museum taken at Villavicencio, Meta, by Hermano Nicéforo Maria in December 1939. Zimmer records four specimens from this locality as intermediate between M. f. ferox and australis, but nearer australis. In a later paper by Zimmer and Phelps,® describing M. f. brunnescens, these four skins from Villa- vicencio were, through some error in printing, included under brunnes- cens instead of australis in their list of specimens examined. It was this, apparently, that caused De Schauensee‘ to include Villavicencio under the range he assigns to brunnescens, and to omit australis from his list. 5 Amer. Mus. Nov. No. 994, June 2, 1938, pp. 12, 15. 6 Amer. Mus. Nov. No. 1312, March 12, 1946, p. II. 7 Caldasia, vol. 5, No. 24, July 10, 1950, p. 826. no. 8 BIRDS OF PANAMA AND COLOMBIA—WETMORE 78 PHAEOMYIAS MURINA EREMONOMA, new subspecies Characters —Similar to Phaeomyias murina incomta (Cabanis and Heine)* but dorsal surface lighter, grayer ; slightly smaller in size. Description—Type, U.S.N.M. No. 400534, male, taken on the Rio Santa Maria, 4 miles north of Paris, Herrera, February 24, 1948, by A. Wetmore and W. M. Perrygo (orig. No. 13500). Crown, sides of head, hindneck, back, and lesser and middle wing coverts between drab and grayish olive; the feathers of the back becoming drab at the tips ; rump and upper tail coverts drab; superciliary stripe, extending from the front of the eye back along the sides of the crown, and the feathers encircling the edge of the eyelids, dull white; lores light grayish olive; primaries, secondaries, and greater coverts dull hair brown; lesser wing coverts edged indefinitely with dull tilleul buff, forming an indistinct wing bar; middle and greater coverts tipped widely with somewhat dull pale pinkish buff, forming two prominent wing bars, in addition to the third indistinct one on the lesser coverts ; inner secondaries margined and tipped broadly with dull white ; outer webs of outer secondaries and primaries edged very narrowly with pale olive-buff; rectrices dull hair brown, tipped and margined nar- rowly on the external webs with pale olive-buff; throat and fore- neck dull white ; upper breast and sides washed with pale smoke gray ; lower breast and abdomen light primrose yellow; under tail coverts Marguerite yellow; under wing coverts light primrose yellow, lined with hair brown on bend of wing. Maxilla and tip of mandible fuscous-black ; base of mandible light grayish olive ; tarsus, toes, and claws black (from dried skin). Measurements—Male (16 specimens): Wing 54.8-60.5 (56.8), tail 48.7-56.2 (51.5), culmen from base 10.0-11.6 (10.8), tarsus 17.0- fo.3 (17.7) mm, Females (13 specimens): Wing 49.8-55.9 (52.8), tail 44.5-48.3 (46.7, average of 12), culmen from base 9.9-I1.5 (10.4, average of 12), tarsus 15.8-18.3 (16.9) mm. Type, male: Wing 55.8, tail 48.7, culmen from base 10.7, tarsus 17.5 mm. Range.—Lowland areas of the Pacific slope of Panama, from the valley of Rio San Pablo in southern Veraguas (Sona, Rio de Jests), and the eastern side of the Azuero Peninsula (Los Santos, Parita, Paris, Potuga, El Barrero) through Coclé (Aguadulce) to the western section of the Province of Panama (Nueva Gorgona, La Campana). 8 Elainea incomta Cabanis and Heine, Mus. Hein., vol. 2, 1859, p. 59 (Carta- gena, Colombia). 8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 Remarks.—Since 1948, when I first found this small flycatcher in the Provinces of Los Santos and Herrera on the eastern side of the Azuero Peninsula, I have been assembling material for comparison from elsewhere in Panama, and from Colombia, since it seemed doubtful that the Panamanian birds, separated from the Colombian group by the whole of Darién and the lower Atrato basin, were the race incomta, named from Cartagena, to which they have been re- ferred. It was found immediately that so many were in worn plum- age, due to the intense light and lack of deep shade in their brushy haunts, that there was considerable fading in color. Finally, enough have been obtained to demonstrate the differences outlined above, through comparison of birds in reasonably fresh dress. Panamanian birds, in addition to being lighter, grayer above, average more yellow below. The latter difference however is variable from specimen to specimen, and is useful only in examining series, so that it is not included in the formal diagnosis. The size difference between the newly described race and incomta is not great but is illustrated by examination of the following meas- urements of the latter form, from Colombian specimens. Males (23 specimens): Wing 60.1-64.4 (62.2), tail 51.0-58.9 (54.9), culmen from base 10.3-11.7 (10.9), tarsus 16.4-19.4 (18.4) mm. Females (16 specimens): Wing 55.5-60.1 (58.3), tail 46.5-53.5 (58.4), culmen from base 9.8-11.0 (10.4), tarsus 16.3-19.3 (17.1) mm. Zimmer ° has recorded one from Panama from El Villano, a locality that I have not found on available maps. In the field this species is liable to confusion with the beardless flycatcher (Camptostoma obsoletum), often encountered in the same localities, in spite of the larger size of Phaeomyias murina, because of similar habits. PHYLLOMYIAS GRISEICEPS QUANTULUS, new subspecies Characters—Similar to Phyllomyias griseiceps cristatus Ber- lepsch,!° but grayer, less greenish, on the back; pileum darker, more brownish; under surface slightly paler, the yellow of breast and abdomen being lighter, and the sides and upper breast paler, with less olive wash. 9 Amer. Mus. Nov. No. 1109, May 15, 1941, p. 10. 10 Phyllomyias cristatus Berlepsch, Journ. Orn., vol. 32, April 1884, p. 250 (Bucaramanga, Santander, Colombia). This description was repeated on page 300 in the succeeding issue for July-October. no. 8 BIRDS OF PANAMA AND COLOMBIA—WETMORE 9 Description—tType, U.S.N.M. No. 420014, male adult, Cana, 1,800 feet elevation, Darién, Panama, June 1, 1912, E. A. Goldman (orig. No. 15783). Crown and hindneck fuscous-black; a narrow super- ciliary, extending from well behind eye to nostrils, dull white; lores chaetura drab; hindneck, back, and scapulars deep olive; rump and upper tail coverts citrine-drab; wing coverts hair brown, with very slight paler borders; primaries and secondaries chaetura drab, the innermost secondaries margined narrowly with pale olive-buff; rec- trices hair brown, the outermost with slight tipping of pale olive-buff ; sides of head chaetura drab, with the lower eyelid dull white, and numerous thin lines of dull white across auricular area ; chin and throat dull white; rest of under surface in general reed yellow, becoming primrose yellow on the abdomen and under tail coverts ; sides of breast lightly washed with citrine-drab ; axillars barium yellow; under wing coverts primrose yellow; inner webs of primaries and secondaries edged prominently with Marguerite yellow. Bill fuscous, tarsus and toes fuscous-black (from dried skin). Measurements.—Male, type: Wing 49.3, tail 43.1, culmen from base 9.7, tarsus 13.9 mm. Range.—Known only from near Cana, Darién. Remarks.—The single specimen on which this form was based was taken by E. A. Goldman toward the close of his work near Cana. While Nelson identified it correctly to species, later the skin was not entered in the museum catalog with the rest of Goldman’s collection, coming to attention only recently in examining the rest of this series. It seems appropriate to describe it, since I find no dupli- cation of its characters in more than 30 skins of griseiceps examined, including examples of the subspecies griseiceps, cristatus, caucae, and pallidiceps. It is the only record for the species in Panama. It is probable that a bird recorded by de Schauensee +! from the Rio Juradé, across the border in Choco, Colombia, also belongs to this new race. The name quantulus, “how small,” is given because of the tiny size of these little flycatchers. Family FRINGILLIDAE SICALIS LUTEOLA EISENMANNI, new subspecies Characters—Male similar to that of Sicalis luteola chrysops Scla- ter ** but clearer, brighter yellow on under surface; dark streaking 11 Caldasia, vol. 5, No. 24, 1950, p. 864. 12 Sycalis chrysops Sclater, Proc. Zool. Soc. London, 1861 (Feb. 1, 1862), 10 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 on back heavier; sides of head more greenish. Female like that of S. 1. chrysops, but lighter, brighter yellow below and on rump; sides of head more grayish brown. Description—Type, U.S.N.M. No. 449369, male adult, taken 2 miles east of Anton, Province of Coclé, Panama, June 20, 1953, by A. Wetmore (orig. No. 18159). Forehead wax yellow, extending back over eye as an indefinitely delimited superciliary line, and shad- ing posteriorly into the sulphine yellow of the crown; hindneck olive lake with a slight grayish overwash; crown, behind the level of the eyes, and hindneck streaked narrowly with chaetura drab; auricular region and side of neck yellowish citrine; lores wax yellow, feathers of the lower half and those behind rictus being white basally, form- ing an indefinite whitish spot; feathers of upper back chaetura black, edged with olive-yellow, producing heavy dark streaks outlined by narrower lighter ones ; lower back yellowish citrine ; rump and upper tail coverts slightly brighter than sulphine yellow; wing coverts in general chaetura drab; lesser coverts edged with light yellowish olive, which is more extensive on the inner feathers; middle coverts mar- gined with deep olive-buff ; greater coverts edged with pale olive-buff ; primaries and secondaries chaetura drab; central portion of outer webs of primaries edged narrowly with olive-citrine, distal portion and secondaries margined with dull white; rectrices chaetura drab, edged basally with yellowish citrine; under surface lemon chrome, deepening on sides of throat and foreneck to apricot yellow ; under tail coverts wax yellow; sides of upper breast washed with strontian yellow ; under wing coverts lemon yellow; inner webs of primaries edged indistinctly with pale olive-buff. Maxilla and tip of mandible chaetura black ; sides of mandible fuscous, base olive-buff ; tarsus and toes clove brown (from dried skin). Measurements.——Males (9 specimens): Wing 60.4-64.8 (62.8), tail 38.5-45.0 (41.3), culmen from base 8.9-10.0 (9.5, average of eight), tarsus 14.2-15.8 (15.0) mm. Female (1 specimen) : Wing 60.1, tail 37.3, culmen from base 9.3, tarsus 15.4 mm. Type, male: Wing 62.3, tail 45.0, culmen from base 9.7, tarsus 14.9 mm. Range.—The savannas of southern Coclé Province, Panama; re- corded to date from west of Rio Hato to near Aguadulce, and north to Penonomé. p. 376. (Mexico merid. = Orizaba, Veracruz, designated by Brodkorb, Journ. Washington Acad. Sci., vol. 33, No. 2, Feb. 15, 1943, p. 34). no. 8 BIRDS OF PANAMA AND COLOMBIA—-WETMORE II Remarks.—This interesting subspecies is described from Io speci- mens taken near Anton and Penonomé. From the race of the species found in southern México, named Sicalis luteola mexicana by Brod- korb (in the reference cited above), which is known from Morelos and Puebla, the form described here is distinguished by brighter color, and by slightly smaller size. The Panamanian form furnishes an interesting link between the races of South America and those of the southern half of México. This bird was first recorded through a sight observation near Penonomé late in January 1951, by Dr. R. T. Scholes, who recog- nized that it was unknown. Eugene Eisenmann and John Bull, in July 1952, found it fairly common, several small colonies being located. In crossing through this area in May 1953, I collected one near Anton, and later, on June 20, I secured the rest of the series from which this description was written. On the June excursion I had the pleasure of the company of Dr. Eisenmann, in whose honor the race is named in recognition of his studies of living Panamanian birds. The birds are found in the nesting season in little colonies that may be overlooked because of the brilliant light of the savanna areas which often obscures the yellow breast color, so that the Sicalis may be confused with the seed-eaters that abound in the same habitat. OTHER ADDITIONS TO THE LIST OF BIRDS RECORDED FROM COLOMBIA Crax daubentoni Gray: Crax Daubentoni G. R. Gray, List Birds Brit. Mus., pt. 5, Gallinae, 1867, p. 15 (Venezuela). M. A. Carriker, Jr., found these birds fairly common in the forested foothills of the Sierra Negra, where he collected specimens near Monte Elias, Magdalena, August 13, and at El Bosque, Guajira, above Carraipia, in the Montés de Oca, June Io and 14, 1941. The occur- rence is to be expected since the species has been taken in the drainage of the Rio Negro on the Venezuelan side of the Sierra de Perija. Chaetura chapmani viridipennis Cherrie: Chaetura chapmani viridipennis Cherrie, Bull. Amer. Mus. Nat. Hist., vol. 35, May 20, 1916, p. 183 (Doze Octobre= Doze de Outobre, Mato Grosso, Brasil). A female taken at El Real, on the Rio Nechi, March 10, and a pair from Taraza, shot April 28, 1948, constitute the second report I2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 of this race since its description from specimens taken in Mato Grosso. Both of the Colombian localities are in Antioquia. Myiarchus ferox venezuelensis Lawrence: Myiarchus veneguelensis Lawrence, Proc. Acad. Nat. Sci. Philadelphia, 1865, p. 38 (Venezuela). A female taken near Nazaret, Guajira, in the foothills of the Serrania de Macuire, on May 13, 1941, is a well-marked example of this race. * { oh ‘ LT sth a yi o ny £ Ny i rey: SMITHSONIAN MISCELLANEOUS COLLECTIONS VOLUME 122, NUMBER 9 INSECT METAMORPHOSIS BY R. E. SNODGRASS Collaborator of the Smithsonian Institution and of the U. S. Department of Agriculture qeoeeeesens mE INCE S ot RES peu SOW MSiO, zn O09 ; PRAIA aN KR Papt Cer Fic. 5—Odonata; general features of larvae. A, Larva of Anax sp., labium in passive position. B, same, labium lowered and partly protracted. C, Crocothemis servilis Drury, labium applied against the face. D, anisopterous larva, posterior segments and lobes enclosing the anus. E, Agrion virgo L., posterior end of body with gill lobes removed. F, Archilestes grandis (Rambur), end segments of body and gill lobes. G, Agrion virgo L., end segments and apical lobes. An, anus; Cer, cercus (cercoid); dl, dorsal gill lobe; Eppt, epiproct; Lb, labium; /l, lateral gill lobe; Md, mandible; Papt, paraproct; sa, supra-anal lobe. of water. Zygopterous larvae are provided with three external gill lobes of various forms at the end of the body, one median and dorsal, the other two lateral, borne on basal plates surrounding the anus. Typically these caudal gills are thin lamellae (fig. 5 F), but they may be sacciform, and in some species they are slender horny blades (G) that do not appear to be suitable for respiratory purposes. The gills are weakly attached to the supporting plates so that they are easily broken off, but they regenerate at the next moult. The current interpretation of the zygopterous larval gills, taken NO. 9 INSECT METAMORPHOSIS—SNODGRASS a7 from Heymons (1904), is that the dorsal gill represents a median dorsal filament and that the lateral gills are the cerci. Arising on each side between the bases of the gill-supporting plates is a small cercus- like process (fig. 5 F,Cer), the ‘‘cercoid” of Heymons, who says it is developed during larval life. The gill-bearing plates (Eppt,Papt) surround the anus (E, An) in a manner so exactly comparable to the epiproct and paraprocts of an orthopteroid insect that their identity as such is hardly to be questioned, and the “cercoids”’ (Cer) have the usual relation of cerci to these plates. The lateral gill lobes (E, Jl, re- moved at their bases) therefore appear to be mere outgrowths from the paraproctial plates, and as such they could hardly be cerci. In the anisopterous larva (D) the gill-bearing plates of the zygopterous larva are produced into long valvelike lobes enclosing the anus, and there is no apparent reason for not identifying these lobes (Eppt,Papt) with the usual epiproct and paraprocts in the same position. The gills are cast off at the transformation to the adult, except as said by Tillyard (1917) that the lateral gills (“cerci”) of the male leave a pair of small processes developed within their bases. If the lateral gills are cerci, it is an unusual thing for an insect to lose these organs. In some zygopterous larvae, in addition to the caudal gills, there are paired lateral gills in the form of tracheated filaments along the sides of the abdomen (see Calvert, 1911; Needham, 1911; Tillyard, 1917). The tracheal system of the Odonata is present in the newly hatched larva, but according to Calvert (1898) the tracheae do not fill with air until the first moult. Spiracles are present in the larva but ordinarily are not functional except for the withdrawal of the tracheal linings at ecdysis. The early development of the tracheal system and the presence of spiracles in the larva, Calvert points out, attest that the immediate ancestors of the Odonata were air-breathing insects. The structural changes that take place during larval life of the Odonata have been summarized by Tillyard (1917) under nine headings. Such changes, however, as the growth of the compound eyes, development of the ocelli, increase in the number of antennal joints and of subsegments in the tarsi, changes in the shape of the thorax correlated with development of the wings, progressive changes in the nervous system, and increase in the number of Malpighian tubules are merely stages in the postembryonic development of the adult organs. These are not true metamorphic changes such as those producing the general form of the larval body, the modification of the labium, and the development and differentiation of the rectal and 38 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 caudal gills. In addition to these changes, however, there takes place during the transformation period a radical change in the sclerotiza- tion pattern of the abdominal segments, accompanied by an almost total destruction of the larval abdominal musculature and the forma- tion of a much more simple musculature for the adult. The Odonata might almost be said to be holometabolous insects without a pupal stage. As in the case of other insects having aquatic larvae, the adult fe- male of the Odonata has one instinct of responsibility to her offspring, namely, that which impels her to go back to the water to deposit her eggs. Some are so conscientious in this respect that they even enter the water and insert their eggs in the stems of submerged water plants. VII. HEMIPTERA The Hemiptera differ from most other insects having specialized mouth parts in the mature stage in that the adult type of mouth parts is just as practical for the young as for the imago. The adult hemip- teron has not evolved feeding organs useful only to an insect with functional wings. The piercing and sucking mouth parts in Hemip- tera, therefore, are developed in the embryo and are functional as such in the newly hatched insect. The same is true of the Thysanop- tera and Anoplura. If there are metamorphic changes between the young and the adults of these insects, they do not affect the essential nature of the feeding organs, and all instars of a species can live and feed together in the same habitat. Among the Heteroptera postembryonic development is principally a succession of growth stages from the young to the adult; the Heteroptera, as the Orthoptera, are essentially ametabolous. Though the change between instars may be accentuated at the last moult, there is in general little, if any, structural deviation on the part of the young insect that must be suppressed in the imago. However, a defi- nite case of juvenile aberration in the Heteroptera is to be seen in a species of mirid described by China (1931) in which the nymph (fig. 6F) is armed on the head, thorax, and abdomen with large dorsal prongs. Though the adult of the species has not been certainly identi- fied, no adult mirid is known to possess any such armature. Among the Homoptera there is a distinct though sporadic tendency for the young insect to develop special characters of its own that are not carried over into the adult stage, or to take on a form quite different from that of its parents. The aberration of the young insect may even become so pronounced that the final transformation to the imago approaches or actually attains a condition of holometabolism. NO. 9 INSECT METAMORPHOSIS—SNODGRASS 39 A good example of simple metamorphosis in the Homoptera is seen in the structural adaptation of the young cicada to a subterranean life by the modification of its front legs for digging (fig. 6D). The nymphal structure of the leg is not present in the embryo (A); it appears first on the nymph with the shedding of the embryonic cuticle just after hatching (B) and becomes more fully developed in succes- Fic. 6—Examples of simple juvenile metamorphic characters in Hemiptera. A, Magicada septemdecim (L.), newly hatched nymph still in embryonic cuti- cle. B, same, left front leg of first instar (from Marlatt, 1923). C, same, front leg of third instar, mesal vieiw showing reduced tarsus (Tar). D, same, front leg of mature nymph, lateral. E, same, front leg of adult. F, Paracarnus myersi China, nymph, Heteroptera-Miridae (from China, 1931). sive instars (C,D). The tarsus of the first instar (B) is reduced in later stages to a small spur on the inner surface of the tibia (C,Tar), but it is fully restored in the mature nymph (D). At the transforma- tion to the adult, the special features of the nymphal leg are much reduced or obliterated (E). The newly hatched cicada has a pair of small eye spots, but in subsequent instars the eyes are lost, and func- tional compound eyes are redeveloped only in the imago. Within a chamber just below the surface of the ground, or built up above the surface, the 17-year cicada at last goes through a period of recon- struction inside the nymphal cuticle, during which the adult structure of the insect is developed, including the compound eyes, the external genital organs, and the sound-producing organ of the male. When 40 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 the insect emerges from its transformation chamber it is an active adult, but it still wears the nymphal skin until it arrives at a suitable place for ecdysis. As another example of simple specialization in a young homopteron we may cite the respiratory canal of the spittle bugs, Cercopidae. On the ventral surface of the tapering posterior segments of the nymph is a deep groove that expands anteriorly into a wide space covered on the sides by the extended abdominal terga, which protect the spiracles. This modification is a respiratory device necessary only to the nymph and is discarded at the moult to the imago. As further examples of juvenile aberration we might note the presence of large branched spines on the back of certain membracid nymphs, and of various minor nymphal characters in other homopterous families that are not retained by the adult. Juvenile specialization among the Homoptera, however, is carried progressively further in the Psyllidae, Aleyrodidae, and Coccidae, until in the last family the transformation to the imago attains the status of true holometabolism. In the Aley- rodidae and the Coccidae the young insects are so different from their parents that, following the definitions given in the introduction, we must call them larvae, but admittedly they are nymphs that have acquired the status of larvae by definition. The Psyllidae go through five juvenile instars, which, except for the flattened form of the body, in general resemble the nymphal stages of ametabolous Hemiptera. The wings appear first in the third instar and increase in size during the fourth and fifth instars ; the legs, how- ever, undergo a metamorphosis, which has been fully described by Weber (1930, 1931) in Psylla mali. The first instar is active because the young psyllid newly hatched on the twig of an apple tree must find an opening bud on which to feed; the legs are relatively far apart on the under side of the body, and in their movements are fitted for walking. After the first moult the insect becomes sessile, the legs come closer together at their bases and are flexed transversely beneath the thorax in order now to function as clasping organs. From the begin- ning, however, the segmentation of the legs has been reduced by a suppression of the femoro-trochanteral and the tibio-tarsal joints. At the moult to the fifth instar the young insect takes on something of the form of the adult, the body becomes deeper, the antennae longer, and in the legs there appears a slightly marked division between the tibia and the tarsus and an indication of two tarsal subsegments. Finally, within the cuticle of the legs of the last juvenile instar the imaginal legs are developed, the trochanter being now separated from the base of the femur, the tarsus distinct from the tibia, and two NO. 9 INSECT METAMORPHOSIS—SNODGRASS 4I well-defined tarsomeres present. The first two pairs of clasping legs of the young become normal walking legs in the adult, but the hind legs are elongated and transformed into jumping organs by an en- largement of the coxae and a lengthening of the body muscles of the trochanters associated with a dorsal extension of the sternal apodeme on which they are attached. The general alteration of the body form at the last moult, Weber shows, involves changes and enlargements of muscles in the thorax that are destined to be motors of the wings. The mouth bristles are retracted into a crumenal pocket instead of being looped outside the head as in the immature stages. While the degree of metamorphosis in the psyllids is thus not large, it is enough to show how a young nymphlike insect can be specifically modified in adaptation to its needs, even in a different way in successive instars. The transformation of the young psyllid into the adult, however, is complicated by the development of special imaginal characters along with the suppression of juvenile characters. In the Aleyrodidae there is a juvenile metamorphosis somewhat similar to that of the psyllids because here also the first instar is ac- tive and the others are sessile. The young aleyrodid, however, is much flattened, the body being of a simple, oval, scalelike form and wingless in all immature instars; the spiracles are on the under surface, and a wide fringe of wax filaments forms a marginal palisade that en- closes an air space beneath the body. There are four immature stages, the characteristics of which are described by Weber (1931, 1934) as follows. In the active first stage the antennae and the slender, taper- ing legs are relatively long; each leg has only three segments and bears a stalked apical adhesive disc, representing the unguitractor plate of the adult insect. In the second instar the antennae are much shortened, and the legs are reduced to small, unsegmented stumps useless for locomotion but retaining the adhesive discs. The same leg structure is carried over into the third instar, but in the fourth instar both the legs and the antennae become again larger, and the legs are now 2-segmented. From the fourth instar the adult aleyrodid is produced directly, but by an unusual transformation process. As described by Weber (1931, 1934) in Trialeyrodes vaporrariorum, the body of the young insect in the fourth instar becomes deeper than that of the preceding instars, and the marginal wax palisade stands vertically below the edges. In the early transformation stage the long, slender legs of the imago grow beneath the larval cuticle, but for want of space they become much folded and looped. Above the bases of the legs deep infoldings of the body wall of the imago form large cavities, which separate the 42 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 median part of the body of the imago from the wide lateral exten- sions of the larval body. From the median walls of these cavities the wings are formed as outgrowths that finally extend back into the ab- dominal region. The lumina of the lateral body lobes of the larva are filled with fat cells, and at first are narrowly continuous above the wing cavities with the haemocoele of the central part of the body, but, as the wings push out, the lateral lobes become disconnected from the central body, and at ecdysis are shed with the larval cuticle. A cavity is similarly formed anteriorly that cuts off the precephalic mar- gin of the nymph, while a third cavity at the posterior end of the body provides for the growth of the external genitalia. At ecdysis, therefore, all the superfluous marginal parts of the larval body are cast off, and the imago is formed from the central part only. The metamorphic characters of the young aleyrodid are thus seen to include a flattening and simplification of the body and a suppres- sion of the wings, together with modifications of the legs adaptive first to active and then to sessile habits. The characteristic feature of the final metamorphosis, however, is in the manner of transforma- tion to the adult involving the discarding of parts of the larval body. The aleyrodid metamorphosis has been termed allometabolism (from allo, different), but the development of the wings beneath the cuticle of the last larval instar is entirely comparable to the simplest form of wing development in typical endopterygote insects; the term En- dopterygota taken literally, therefore, would include the Aleyrodidae. It is in the Coccidae that metamorphosis among the Homoptera reaches its highest degree of complexity. The young scale insect is a larva adapted to a parasitic life on plants, and in its external aspect it is quite different from the adult. The true form of an adult coccid, however, is known only from the winged male, since the female be- comes sexually mature in a late larvalike stage and undergoes no further transformation. On hatching from the eggs the simple, flattened first-instar coccid larvae are provided with eyes, antennae, mouth parts, and legs. They are active crawlers whose function it is to disperse themselves over the food plant. When the young larvae have settled down at a suitable feeding place, they moult and enter a second larval stage in which the legs in many species are reduced, or lost altogether, though in some forms the legs are fully retained. With typical species (diaspine scales) there are only two larval instars, but in some there are three or more, and generally during the larval period there is only a slight difference between the males and the females. At the last larval moult, however, the sexes are differentiated. The female looks like only NO. 9 INSECT METAMORPHOSIS—SNODGRASS 43 another and larger larval instar, since she has no vestiges of wings; in some species the legs and antennae are retained, but in many the legs are much reduced or suppressed. The female usually preserves her mouth parts and alimentary canal, though the external feeding organs may disappear. The ovaries, however, become functional and soon the body of the female is converted into a bag of eggs. In the reproductive stage the female scale insect thus appears to be a sexu- ally precocious larva, but some coccidologists contend that she has at- tained a larval form secondarily by a process of reduction or degen- eration from a winged adult. Perhaps the only way to settle the ques- tion would be to give the female a dose of the proper hormone and see what happens to her. The male coccid, after the last larval moult, goes through usually two immobile transformation stages, and then becomes in most cases a winged insect. In the first transformation stage, know as a propupa, the male of winged species begins to take on the form of the adult; the antennae, legs, and wings appear, and the eyes are fully developed, but the mouth parts are reduced or suppressed. In the next stage, termed the pupa, the insect assumes more closely the form of the winged imago, the antennae and the legs increase in length, taking on the character of the adult appendages, and the wings lengthen. In the male of Lepidosaphes ulmi, according to Suter (1932), there is only one pupal stage, during which the wings and legs appear and increase in size until the moult to the adult. The adult male usually has a pair of well-developed wings, but is devoid of feeding organs. In some species, however, the male does not attain the typical winged structure; the wings may be absent, the antennae and the legs much reduced in length, while the body retains the larval form with no constriction between head, thorax, and abdomen. The redevelopment of the antennae and legs of the male scale has been shown by Berlese (1896) in the Diaspinae (/ytilaspis) to take place in the early pupa by evagination of the appendage rudiments from pouches of the integument beneath the cuticle of the propupa. In addition to its external transformations the male coccid under- goes a very considerable degree of internal metamorphosis, which has been described particularly in Pseudococcus by Makel (1942). Along with the casting off of the mouth parts there is a great reduction of the alimentary canal, which retains its form in the pupa, but in the imago the mesenteron is reduced to a mass of cells without a lumen. The oesophagus remains as a slender tube, the proctodaeum is nar- rowed, though the rectum keeps its original dimensions, and the 44 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 Malpighian tubules increase in size. These changes are mostly retro- gressive from the larval condition. On the other hand, the reproduc- tive organs develop gradually to the definitive functional state, and there is a thoroughgoing reconstruction of the larval musculature into that of the adult. In her account of the muscle transformation in the male of Pseudo- coccus Makel distinguishes five different groups of muscles, as fol- lows: (1) Larval muscles that go over with little or no change into the imago; (2) larval muscles that undergo such changes as splitting, uniting, or a change of position; (3) larval muscles destroyed by histolysis and not regenerated; (4) transformation muscles formed by addition of imaginal elements to larval muscles; (5) muscles of the imago that arise as new muscles in the propupa. To this last group belong four muscles of the thorax, and seven oblique intersegmental muscles of the abdomen, together with two muscles connected with the external genital organs. The metamorphosis of the muscular sys- tem as given by Makel is based on a detailed comparative study of the musculature in the larva, pupa, and adult. It is clear that the transformation of the male coccid is a true holo- metabolous metamorphosis, and that the larva is a specialized juvenile stage. It may be questioned, however, that the coccid pupa is com- parable to the pupa of the higher holometabolous insects. The pres- ence of two pupal stages having a general resemblance to the winged nymphal stages of other Hemiptera suggests that the so-called pupal instars of the male coccid pertain to the juvenile period of the life history and not to that of the imago. The work of Wigglesworth (1948, I951a) on the hormonal control of transformation in the reduviid Rhodnius shows that the juvenile hormone controls the nymphal status up to the imago, and if this is true in other Hemiptera the coccid pupa is not a part of the imaginal stage. Holometabolism can be defined only as a type of metamorphosis ; the fact that it occurs among the Hemiptera in the male coccid, and also in the Thysanop- tera does not taxonomically relate these insects to each other or to such holometabolous insects as Coleoptera, Lepidoptera, Diptera, and Hymenoptera. VIII. THYSANOPTERA The Thysanoptera seem to contradict the principle that postembry- onic metamorphosis is due to some structural aberration on the part of the young insect that fits it to a special environment or way of liv- ing. The active young thrips in appearance differs from the imago little more than a young aphis differs from a winged adult aphis, and NO. 9 INSECT METAMORPHOSIS—SNODGRASS 45 it would seem that in like manner it could grow into an adult thrips without any radical process of transformation. However, after two active, feeding nymplike stages (fig. 7 A,B) the young thrips becomes SS MSW Wy Wi LEELA e = ZB SSS BROS. SS LALA OZ. NSAINASSSSSSS WYO” ZA YS \\ Vif ee (pj aa Wx Nr Fic. 7.—Life-history stages of a thysanopteron, Scirtothrips citri Moulton (out- lines from Horton, 1918). A, first instar. B, second instar. C, propupa. D, pupa. E, adult female. inactive, ceases to feed, moults, and enters a quiescent stage known as a propupa (C). The propupa in turn is followed by a second rest- ing stage termed the pupa (D), from which after a final moult the adult emerges (E). In the Terebrantia the wings appear in the propupal stage as straplike outgrowths, which become still more ex- tended in the pupa. In the Tubulifera the propupa differs little in 46 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 external appearance from the second nymph, since in this suborder the wings do not appear until the pupal stage. In most of the Tubu- lifera, however, there is a second pupal stage separated from the first by a moult, making five immature instars in all, but according to Priesner (1920) a propupal stage is absent in some species and in others there is only one pupal stage. The few external changes other than the growth of the wings that take place during the postembryonic development of the Thysanop- tera are of little consequence. In some forms the antennae are reduced in the propupa and their segmentation becomes indistinct. In the pupal stage the antennae elongate, their segmentation becomes distinct, the form of the head approaches that of the imago, the compound eyes increase in size, the ocelli appear, and the sexes are now distin- guishable. Most of these changes are merely those that any ametabo- lous nymph might go through in its development to maturity. The resting stages in the life history of a thrips, however, suggest that internal changes are going on, and, in fact, a reconstruction of some of the internal organs takes place during the propupal and pupal stages that is entirely comparable to the transformation processes of holometabolous insects. These changes in the thrips affect the alimen- tary canal, the salivary glands, the fat tissue, the muscular system, and in a lesser degree the nervous system. The alimentary canal of Liothrips oleae, according to Melis (1935), does not differ essentially in external form during preimaginal stages from that of the adult, but the cellular structure of the mesenteron becomes highly unstable and is in a continuous state of reorganiza- tion. On the other hand, in Parthenothrips dracaenae, as described by Miller (1927), the alimentary canal undergoes changes in shape and size as well as cellular reconstruction during the propupal and pupal stages. In the two nymphal instars the long tubular ventriculus is looped forward upon itself and then turns back to join the intes- tine; in the propupa the whole canal becomes a simple straight tube with no ventricular loop; in the pupa the ventricular loop reappears but only as a short lateral fold from the middle of the tube; in the imago the ventriculus is again bent forward on itself as in the nymph, and there is a secondary small loop in the descending arm. Since the alimentary canal of the adult becomes practically the same as that of the young thrips the intervening changes might seem useless, except that, as the insect takes no food during the propupal and pupal instars, the ventricular changes may be simply economy adaptations to a lack of need for a digestive organ. In Parthenopthrips, Miller says, there is one renewal of the midgut epithelium. At the beginning of metamor- NO. 9 INSECT METAMORPHOSIS—SNODGRASS 47 phosis in the last part of the second larval stage the regenerative cells of the ventriculus actively multiply and later spread out to form a new epithelial layer while the old degenerating layer is cast off into the lumen. Elongation of the stomodaeum and the proctodaeum pro- ceeds from cell proliferation by mitotic division in “imaginal rings” of cells at the inner ends of these two ectodermal parts of the canal. The Malpighian tubules of Liothrips oleae, according to Melis (1935), undergo no appreciable transformation, being the same in all stages. The salivary glands degenerate in the propupa and pupa, and are reduced to long bodies crowded with large nuclei in a scant protoplasm, but they are restored in the adult to essentially the nymphai form. The cells of the fat body play the usual role in meta- morphosis; they increase in size during nymphal life and store up nutritive products in their cytoplasm, which in the propupa and pupa are given out and consumed in the reconstruction of the muscles. The change in the nervous system involves principally a transposition of the brain from its nymphal position in the thorax into the head of the adult, accompanied by development of the cerebral nerves and their adaptation to the imaginal organs they innervate. The reorganization of the muscular system is the most important feature of metamorphosis in the Thysanoptera. As described by Melis (1935) in Liothrips oleae, during the propupal stage the larval muscles of the head go into complete histolysis, in the thorax and in the last abdominal segment there is a partial myolysis, but most of the abdominal muscles do not undergo any appreciable change. Dur- ing the pupal stage there follows a total regeneration of the intrinsic head muscles, and a reconstruction of the thoracic and abdominal muscles to fit the needs of the adult. The processes of histolysis and histogenesis as described in detail by Melis are the same as those in typical holometabolous insects; muscles that are to be reconstructed with new attachments undergo a partial dissolution, but the nuclei persist in small fragments of cytoplasm that reassemble to form new muscles, or attach themselves to remnants of old muscles to form reconstructed muscles. The internal metamorphosis of the Thysanoptera is thus seen to be truly holometabolous, but the nymphlike form of the insects in all the immature stages, and the small degree of external change from nymph to pupa and from pupa to imago suggest that the so-called pupal stages are merely the usual third and fourth instars, which have become inactive because of the reconstructive process that takes place within them. The immature stages of the Thysanoptera thus appear to be comparable to the nymphal stages of ametabolous insects, with 48 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 the wings developed in the third or fourth instar. It is, therefore, difficult to account for an internal metamorphosis for which there is no apparent external reason. IX. OLIGONEOPTERA, OR TYPICAL ENDOPTERYGOTA: NEUROPTERA TO HYMENOPTERA Whether the orders here included constitute a monophyletic group of holometabolous insects or not will be a matter of opinion. Since holometabolism occurs in the unrelated Coccidae and Thysanoptera, some entomologists will contend that it may have arisen independ- ently among other holometabolous orders. The modern larvae of the typical endopterygote insects differ from the nymphs of ametabolous insects and the larvae of hemimetabolous insects not only in being endopterous but also in several other respects. They lack eyes that are identical with the compound eyes of the adult, and usually they have independently developed simple larval eyes; the hypopharynx, when present, is more or less united with the labium; the body mus- culature differs from the typical adult musculature in varying degrees ; and metamorphosis from larva to imago in all cases involves an inter- vening pupal stage. Inasmuch as there can be little question that endopterygote insects have been evolved from exopterygote ancestors, the simplest and most reasonable view to take concerning the nature of the holometabolous endopterygote larva is that it represents in modified form the nymphal instars of ametabolous exopterygote insects. Both the larva and the nymph are the active juvenile stage of the insect during which the wings are developed. Whether the wings grow externally or in- ternally, or may be retarded in their growth to a late instar, is a difference of no consequence. The larva as well as the nymph has wings in the course of development, and is not a “wingless” stage of ontogeny. If the legs also are developed beneath the cuticle, the larva for that reason is not “legless,” and does not represent an apodous stage of ontogeny or phylogeny. The principal problem concerning the origin of the endopterous holometabolous larva involves the question: For what way of life was the primary larva modified from an ordinary ametabolous nymph that led to the acquisition of its distinctive features and its holo- metabolous metamorphosis? The young cicada or the young stonefly clearly show how, by simple structural adaptations for environments different from those of the adult, a nymph might readily be converted into a hemimetabolous larva, but external modifications do not account for holometabolism. NO. Q INSECT METAMORPHOSIS—SNODGRASS 49 The endopterous condition of the larva and the substitution of short-sighted simple eyes for long-sighted compound eyes were con- ceived by Lameere (1899) to have arisen as adaptations in a primary nymphlike juvenile form to boring into plant stems. The theory, how- ever, does not take into consideration the facts that most present-day larvae of the boring type are specialized forms in their own orders, and that free-living forms give no evidence of having been recon- structed for life in the open from a primary boring type of larva. It is hard to believe, for example, that the antecedents of the aquatic Corydalus larva or the Dytiscus larva, or even those of terrestrial beetle larvae lived in plant stems. As for the change of eyes, it would seem that a boring larva would hardly need any eyes at all. Though the Lameere theory of larval origin is thus not convincing, it is the only theory that has been proposed to account specifically for the characteristic external features of modern endopterygote larvae. We can readily imagine that the suppression of external wing pads during the nonfunctional period of their development would be a con- venience to most any young insect regardless of its habitat. Wing- less larvae, by comparison with winged nymphs, have certainly shown a great superiority in ability to adapt themselves to different environ- ments and to different ways of living. A theory concerning the nature of the endopterygote larva, elabo- rated by Jeschikov (1929), regards the larva as a free-living continu- ation of the embryo; the larva has even been defined as such (Hen- derson, 1949). First, we might ask, what animal is not a continuation of the embryo? The theory of Jeschikov, however, contends that the larva is an embryo, and that the nymphal stages of its ancestors are all condensed in the pupa. However, in no other insects are the wings developed in the embryo, at most they are represented only by differentiated groups of cells in the embryonic epidermis. The ame- tabolous and hemimetabolous Pterygota all show that wing develop- ment is a function of postembryonic life. Periodic moulting is com- mon to both nymphs and larvae, but it would be quite exceptional in an embryo. If the larva is an embryo, cases of paedogenesis would really be embryogenesis, and larval heteromorphosis would be embry- onic heteromorphosis; some embryos would take to the water on hatching, others would burrow into the ground, still others would climb trees, and finally we should have embryos spinning cocoons and transforming into pupae. These implications are rather too much for the theory. When the embryo comes out of the egg and takes on all the functions necessary for a free life, its embryonic stage is ended, 50 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I22 though of course what we now call it is merely a matter of conven- tional definition. The endopterous condition of the larva very probably was not pro- duced by a single mutation. In the simplest type of wing development among modern endopterygote insects, as shown by Tower (1903) in certain Coleoptera, the wing is first formed in the early pupa beneath the cuticle of the last larval instar, and is therefore exposed only at the moult to the pupa. If formed as a fold of the body wall at any earlier stage the wing rudiment would be exposed at the next larval moult. The first appearance of wing pads among exopterygote in- sects on different instars shows that the wing growth may be retarded. In the past history of those beetles in which the wing is not present as a fold until the early pupa, the external growth of the wing must have been first retarded and then suppressed until the end of larval life, and we may conclude, therefore, that the first step in attaining the endopterous condition was a retardation in the time of develop- ment of the wing rudiment. The formation of a wing fold is not the true beginning of the wing development; in earlier larval stages the alar rudiment is present in the form of a thickening or a differenti- ated group of cells in the epidermis, which is the wing in a state of suppressed growth. On the other hand, in most of the endopterygote insects the de- velopment of the wings has been expedited by the early recession of the growing wing rudiments into pockets of the epidermis beneath the cuticle, which become closed and are thus not affected by the larval moults. Within these pockets the wings can grow without being ex- posed until they are everted at the moult to the pupa. According to Tower (1903) the wings develop in this manner among the Coleop- tera in Scarabaeidae, Coccinellidae, and Chrysomelidae; Patay (1939) says the wings of Leptinotarsa develop in closed pockets toward the end of the third instar. A familiar example of the usual recessed type of wing development beginning in the second larval instar is that given by Mercer (1900) for Pieris rapae. The endopterous condition in its evolution, therefore, has probably gone through two phases, both existing among modern insects. In the first phase the growth of the wings presumably was suppressed until the end of the juvenile period; in the second phase the wing rudiments developed again at an early larval stage, but now sank into the epidermis beneath the cuticle, thus still preserving the “wingless” state of the young insect. It must be evident, then, that there is no truly wingless larva of any winged insect; the wings exist in some NO. 9 INSECT METAMORPHOSIS—SNODGRASS 5I retarded stage of growth. The endopterygote larva, therefore, does not represent an apterous stage of ontogeny, and much less does it recapitulate an apterous stage of phylogeny. Similarly, legless larvae are not truly apodous; the leg rudiments are present in some form, though they may be greatly reduced. In the honey bee, for example, Nelson (1915) has shown that external leg rudiments are present on the embryo, but at the time of hatching are reduced to discs in the epidermis, which later redevelop internally in the larva. The leg tissue, therefore, is continuously present, though it may not take the form of a leg bud until late in larval life. The suppression of compound eyes during larval life, unlike the suppression of wing pads, would not seem to confer any advantage on a free-living young insect. The typical larval eyes are simple single eyes, usually only a few in a group on each side of the head. They are developed on the site of the future compound eyes and are con- nected with the same part of the brain; but generally at the end of larval life the larval eyes degenerate, and they never take any part in the formation of the definitive compound eyes. In the Culicidae and related Diptera it is shown by Constantineanu (1930) that the com- pound eyes begin their development in an early stage of the larva, and that the larval eyes, which are formed in the embryo, are retained in the adult. Yet the two remain as entirely distinct organs. In the larva of Panorpa there are 30 to 35 single eyes in a group on each side of the head, and, as described by Bierbrodt (1942), these pan- orpid larval eyes have attained the structure of ommatidia, and prob- ably function as appositional compound eyes. However, the larval eyes and their nerves degenerate during the pupal metamorphosis and do not become the compound eyes of the adult. Here is a case, there- fore, in which a larva has succeeded in reacquiring functional com- pound eyes, but these larval eyes, as those of other insects, give place to adult compound eyes newly developed in the pupa. In discussing the origin and evolution of endopterygote larvae, Chen (1946) contends that the primary larva, derived from an exop- terous nymph, was aquatic, and he cites the megalopterous larvae, particularly the larva of Corydalus, as being the closest modern repre- sentative of the primary larva. Though it may be conceded that the megalopterous larvae are relatively generalized modern forms, they are nevertheless superficially modified for aquatic life, and life in the water does not account for their more fundamental characters, which are those of endopterygote larvae in general. The stonefly, mayfly, and dragonfly larvae are all aquatic, and yet they have compound eyes and external wing pads, and they transform without a pupal stage. 52 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 If we assume that the primary endopterygote larva was a modified nymph, we might more reasonably expect it to be best represented among modern forms by some of the simpler terrestrial larvae, such as a raphidian larva (fig. 8B), or coleopterous larvae in the families Carabidae, Staphylinidae (C), and Dermestidae (D). Such larvae live in the same general habitat as the adults, feed on the same kind Fic. 8—Examples of a generalized ametabolous nymph and of simple holometabolous larvae. A, Zootermopsis angusticollis (Hagen), nymph of a winged termite. B, Agulla adnixa (Hagen), raphidian larva. C, Creophilus mavillaris Long, larva of a staphylinid beetle. D, Attagenus piceus Oliv., larva of a dermestid beetle. of food with the same kind of mouth parts, and have no structural adaptations for any particular environment. Except for the lack of external wing pads and compound eyes they resemble an ametabolous nymph (A), and they differ least from the structure of the adults of their species. The larvae of the lower endopterygote groups show their closer relation to the exopterygote insects in the possession of typical two- clawed pretarsi. Those with paired movable claws on the feet include the larvae of Megaloptera, Raphidioidea, most Neuroptera except Sisyridae, and the larvae of the coleopterous families Carabidae, Cicindellidae, Gyrinidae, Dytiscidae, Amphizoidae, and Noteridae. The two-clawed foot evidently is primitive among the winged insects ; NO. 9 INSECT METAMORPHOSIS—SNODGRASS 53 the single claw of the larva in the higher orders, therefore, is a secondary larval modification, and does not represent a primitive one- clawed pretarsus, or dactylopodite. It would seem, therefore, that an unspecialized modern larva should best represent the primary endopterygote larva, since from such a larva evolution could more readily produce various specialized forms. Yet even the simplest of modern larvae gives us no suggestion of how or why it acquired its distinctive larval characters. The endopterous holometabolous larva must, for the present, be accepted only as a fact ; we have no evident explanation of its origin. The reason for holometabolism, that is, for metamorphosis that involves the intervention of a pupal stage between the larva and the imago, is not to be found in the external characters of the larva. The young mayfly or the young dragonfly differ externally from their parents more than do the larvae of some endopterygote insects, but yet they transform without a pupal stage. The pupal transformation processes involve a variable degree of reconstruction of both external and internal larval tissues, but, so far as known, they always include at least a partial dissolution of the larval musculature accompanied by the formation of new muscles or of new muscle attachments for the imago. The cessation of muscular activity brings about the quiescence of the pupal stage. Since the lesser degrees of change in other internal organs might be accomplished direct from larva to imago, it appears to be the disparity in the muscular system between the young insect and the adult that constitutes the reason for holo- metabolism. As we have seen, this is true also for male Coccidae and the Thysanoptera. The external suppression of the wings, the absence of compound eyes, or the presence of abdominal appendages in the larva have nothing to do with the fact that the holometabolous larva has a muscular system that cannot go over entirely or directly into the adult musculature. The somatic musculature of nearly all adult pterygote insects is built on the same fundamental plan, though some muscles may be re- duced or eliminated in the thoracic segments of wingless species or in those having weak powers of flight. The musculature of exopterygote nymphs is essentially like that of the adults, but in holometabolous in- sects the musculature of the larva is usually very different from that of the adult. The pattern of the larval musculature is simpler in the less specialized larvae of each order, and it is least specialized in larvae that differ least from the adults. Hence, we may suppose that the simplification of the larval musculature in a primitive endopterygote 54 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I22 larva was an economy measure correlated with the reduction of the wings and the fewer abdominal movements that the larva had to make as compared with the adult. Whenever the difference between the larval musculature and the adult musculature reached a point where new attachments for imaginal muscles became necessary, a new moult had to intervene, and thus a pupal stage became interpolated between the larva and the imago. With the pupa once established as a reconstruction stage for the muscles, it served also increasingly for the transformation of other tissues. In most of the major holometabolous orders the larval musculature becomes progressively more complex in the higher families. The wormlike form assumed by so many larvae, and the consequent neces- sity of a wormlike mechanism of movement readily accounts for the specialization of the musculature in all vermiform types of larvae. Since the insect larva, however, is not a worm, no matter how worm- like it may be, its musculature is never that of a worm, it merely serves mechanically to enable the larva to make wormlike movements. Otherwise, the forms and structure of most modern specialized holometabolous larvae are clearly adaptations to specific environments or ways of living, usually different from those of the adult. Such larvae have thus taken on temporarily structures useful only to them- selves, which must be discarded at the final transformation to the imago. The ordinary caterpillar with its short thoracic legs, its long abdomen supported on leglike props, its strong biting and chewing jaws and ample food tract is clearly made for feeding in the open and for the storage of food reserves. A boring larva, on the other hand, is unmistakably adapted to burrowing into wood or plant stems. The larvae of Diptera were probably in the first place aquatic, but their structure is readily adaptable to life in mud, fruit pulp, manure piles, and the bodies of other animals. The grubs of wasps and bees are incapable of self-support, but they are perfectly constructed for con- finement in cells where they are furnished with food by their mothers or other adult attendants. Internal parasitic larvae are usually greatly simplified in structure because they have nothing to do but to feed on the food in which they are immersed. The presence of paired appendicular organs on the abdomen of various endopterygote larvae has often been taken to be a retention from the embryo of a stage representing a primitive polypod condition in the ancestry of insects. Thus Chen (1946) says: “The primitive larvae are presumably of the campodeoid-polypod type, having three pairs of thoracic and ten pairs of abdominal legs; the latter bear each NO. 9 INSECT METAMORPHOSIS—SNODGRASS 55 a vesicle and a stylus.” From this premise Chen concludes that the Corydalus larva is the closest modern representative of the primary larva, and that the latter was aquatic. In a former paper the writer (1931) reviewed the structure of the appendicular organs on the ab- domen of endopterygote larvae, and suggested that these appendages represent the eversible vesicles and the styli of Thysanura. Broad generalizations are always mentally comforting because they relieve the mind from the confusion of seemingly unrelated facts, for which reason also generalizations are prone to become wider than the evidence on which they are based. A closer comparison of the ab- dominal appendages of endopterygote larvae with the vesicles and styli of Thysanura shows that the two sets of organs are not identical in structure, which fact raises the suspicion that they may be in no way related. Furthermore, there is no valid reason for supposing that the primary endopterygote larva should have had thysanuran charac- ters. Some exopterygote insects retain a single pair of styli on the abdomen, but none of them has abdominal vesicles or other abdominal appendages except cerci and the organs of copulation and egg laying, which are a common inheritance of Thysanura and both exopterous and endopterous Pterygota. Insects could not be encumbered with abdominal appendages after they acquired wings. The polypod pro- genitors of the insects are unknown; they probably became extinct when the primitive apterygotes became hexapods. As we have seen, even the Thysanura do not have true legs other than those of the thorax. Possible vestiges of abdominal legs are retained among the apterygotes only in the Protura and Collembola. The adjectives “thysanuriform” and “campodeiform” as applied to the more simple types of endopterygote larva can have only a de- scriptive value. An endopterygote larva, no matter how thysanuri- form it may be in appearance, is just as truly a winged insect as is an exopterygote nymph, and it is much farther removed than the nymph from its apterygote ancestors. Since it is hardly to be sup- posed that the exopterygote orders and the endopterygote orders represent two primary lines of divergence from primitive winged insects, the endopterygotes must have had a long line of exopterygote ancestry separating them from their apterygote progenitors. Exop- terygote insects were already flourishing in Carboniferous times, en- dopterygotes appear in the Permian; the earliest apterygotes (Col- lembola) are known from the Devonian. Larval abdominal appendages are most fully developed in the larva of Corydalus (fig.9 A). Along each side of the abdomen on the first 56 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 Fic. 9.—Abdominal appendicular organs of holometabolous larvae. A, Corydalus cornutus (L.), posterior abdominal segments and appendages. B, same, terminal appendage of right side, mesal. C, same, cross section of gill- bearing segment. D, Malacosoma americanum (F.), a right abdominal leg cut open mesally to expose muscles. E, section of leg of a tardigrade, showing muscles (from Baumann, 1921). F, panorpid larva, under surface of meta- thorax and first abdominal segment. G, same, sternal arc of first abdominal segment, posterior. H, Dineutes sp., larva, metathorax and anterior abdominal segments. I, same, inner surface of an abdominal appendage-bearing lobe. J, same, section of left side of an abdominal segment. K, same as I with inner layer of muscles removed. NO. 9 INSECT METAMORPHOSIS—SNODGRASS 57 eight segments is a row of lobelike projections between the terga and sterna that fall in line with the bases of the thoracic legs. Each lobe bears a long, tapering lateral process, and each but the last a large ventral tubercle carrying a brush of gill filaments. On the tenth seg- ment is a larger appendage (B) armed distally with a pair of strong claws, and bearing on its outer surface a slender process like that of the preceding appendages. In the larva of the related Chauliodes ven- tral tubercles are absent, but long, tapering lateral processes are pres- ent on the first eight abdominal segments, and the ninth segment bears a pair of appendages similar to those of Corydalus. Ventral tubercles are absent also in the Sialis larva (fig. 10 A), but long tapering lateral processes are present, each of which is distinctly divided into six segmentlike parts. The abdominal “legs” of caterpillars have a struc- ture resembling so closely that of the gill tubercles of the Corydalus larva as to suggest that the two are homologous organs. The same is true of the abdominal “legs” of sawfly larvae, and of the apical ap- pendages of trichopterous larvae, the structure of which has recently been reviewed by Pryor (1951). The abdominal vesicles of Thysanura are retractile by short muscles arising on the supporting plates of the venter (fig. 2 C,D,E), and the styli are movable by muscles arising on these same plates (D,E). The plates are admittedly flattened remnants of abdominal limbs, and Machilis demonstrates that the styli are coxal appendages (B,Sty) acquired during postembryonic development. In the endopterygote larva the abdominal tubercles are likewise retractile, but the principal retractor is a long muscle taking its origin on the dorsal wall of the corresponding body segment (fig. 9C,D). Whether this difference in the musculature of the thysanuran and larval organs is significant or not will be a matter of opinion, but the fact remains. On the other hand, the basal musculature of the tapering lateral processes of the megalopterous larvae (fig. 9 C) is quite comparable to that of a thy- sanuran stylus in that it arises from the supporting body lobe, which fact might therefore be taken as evidence that these processes truly represent styli. When, however, we note the occurrence of similar abdominal proc- esses in other unrelated larvae, the interpretation of any of them as primitive styli becomes doubtful. The aquatic larva of the gyrinid beetle Dineutes (fig. 10 B), for example, has a pair of long, tapering lateral filaments arising from each of the first eight abdominal seg- ments and two pairs from the ninth segment. The single filaments are supported on lobes of the body (fig. 9 H) that lie in a line above 58 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 the level of the pleural plates (P/) of the thorax. Each lobe is crossed internally by two layers of vertical muscle fibers (I) enclosing a large trachea between them (J,K,7ra) that runs out into the filament. The filament itself is movable by two antagonistic muscles, one mesal, the other lateral, attached on its base. Then there is the curious termi- tophilous tineid caterpillar, Plastopolypus divisus (fig. 10C), first described by Silvestri (1920), which has long, slender, multiarticulate Fic. 10.—Examples of unrelated holometabolous larvae with lateral appendicu- lar organs on the abdomen. A, Sialis sp. Megaloptera. B, Dineutes sp. Coleoptera-Gyrinidae. C, Plasto- polypus divisus Silv. Lepidoptera-Tineidae (from Hollande, Cachon, and Vail- lant, 1951). D, Nymphula maculalis Clemens, Lepidoptera-Nymphulidae (from Welch, 1916). processes projecting from the sides of the first seven segments of the abdomen. These appendicular structures have been shown by Hol- lande, Cachon, and Vaillant (1951) to be sensory and not exudatory organs, since they are covered with innervated setae and contain no glandular tissue; but these writers, and also Silvestri, find that each appendage is movable by a muscle inserted within its base. Must we, therefore, interpret all these structures as representative of thysa- nuran styli? Hollande, Cachon, and Vaillant contend that the abdomi- nal appendages of the Plastopolypus caterpillar are merely secondary adaptations of the larva to life in the termite colony, as are also true exudatory lobes on the body of other termitophilous species. NO. 9 INSECT METAMORPHOSIS—-SNODGRASS 59 Similar though nonmusculated processes are shown by Hollande, Cachon, and Vaillant to be present on a termitophilous fly larvae, but in this case two pairs are present on each body segment, one pair lateral, the other dorsal, and several other fly larvae associated with termites have simple nonarticulate lateral appendages, some very small, others large and club-shaped. Then there are the aquatic cater- pillars with gill filaments along the sides of the abdomen (fig. 10 D), some of which are simple fingerlike processes and others elaborately branched filaments. The panorpid larva is sometimes cited as an ex- ample of a larva having abdominal leg rudiments, but an examination of this larva shows that the supposed “legs” on the abdomen (fig. 9g G) do not fall in line with the thoracic legs, and correspond exactly in position with seta-bearing papillae on the thoracic venter between the legs (F). All such examples of the presence of segmental appendicular struc- tures on the larval abdomen only go to show the facility with which the young insect can develop special organs for various purposes of its own. As Pryor (1951) has pointed out, similarity of structure in nonsegmented organs of locomotion is not necessarily a criterion of homology. With respect to the abdominal “legs,” he says, “there is in fact as much resemblance between a caterpillar and an onychophoran or a tardigrade as between a caterpillar and Corydalus.” The tardi- grade leg (fig. 9 E) has a long muscle (b) from the body wall, which, according to Baumann (1921), is connected with each claw by a slender tendon (f). Likewise in the Onychophora the plantar discs and claws of the legs are retractile in the same manner by muscles, some of which have their origins in the leg and others on the body wall. Such cases of similarity in musculature, as noted by Pryor, are evidently independent adaptations to the functional needs of locomo- tor organs having the same type of structure and action. Ideas that can be neither proved nor disproved have to depend on circumstantial evidence for support, but when circumstantial evidence is not conclusive they had better be dropped, or held for further in- vestigation. This principle applies to the musculated abdominal ap- pendages of endopterygote larvae. If these appendages are related to the vesicles and styli of Thysanura, they are appurtenances of ab- dominal legs and not legs themselves. On the other hand, many in- sect embryos do have leg buds on the abdomen which usually disap- pear, but it is certainly quite possible that embryonic remnants of primitive legs might be retained and redeveloped in a new form for postembryonic use. We have only to consider the extraordinary elab- 60 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 oration of pleuropodia in the embryos of some insects to see the ex- tent to which appendages presumably equivalent to legs can be modi- fied for a new purpose. Eastham (1930) has shown that rudiments of abdominal appendages appear on the embryo of Pieris rapae in line with the rudiments of the thoracic legs, and that there is no evi- dent reason for not regarding all these appendages as serially homolo- gous organs. Many cases might be cited from other arthropods in which a leg rudiment develops into a very unleglike structure, and perhaps a very good example of this is to be seen in the external geni- tal organs of insects. The idea usually deduced from the presence of paired movable appendages on the abdomen of endopterygote larvae is that such larvae are recapitulations of a polypod stage of insect ancestry. This idea, however, is not supported by other characters of these larvae. Take the caterpillar, for example; in no respect does it have a primi- tive organization. In the structure of its head, its mouth parts, and its muscular system the caterpillar is a highly specialized modern insect form, and, most important, it is a stage of postembryonic growth in which wings are in the course of development. The cater- pillar has a polypod status because its abdominal appendages were not suppressed in the embryo, but it does not represent a primitive polypod stage of phylogeny. Wings certainly did not arise in a poly- pod ancestor of the insects ; a winged centipede is hardly to be visual- ized as a reality. The holometabolous larva is an independent organism. It can de- part to any extent from the structure of its parents, and it is under no compulsion to recapitulate its ancestral history. The independence of the larva begins with the embryo, which develops directly into the larval form whatever this may be. From the experimental work of Hegner (1911) on the eggs of Leptinotarsa, of Reith (1925) and of Pauli (1927) on the eggs of muscoid flys, and of Smreczynski (1938) on eggs of the beetle Agelastica alni, it is known that in these insects the larval structure is fully determined in the preblastoderm stage of the egg. Probably the same is true for many other holo- metabolous insects. A few hours later, however, as shown by Geigy (1931) in Drosophila, injury to the blastoderm causes defects in the adult fly. In this very early stage, therefore, the egg has the poten- tiality of producing both a larva and an imago, but the larval develop- ment takes precedence over the imaginal development. The primary business of the holometabolous embryo is to produce a larva; in so doing it may entirely ignore its own phylogenetic history, and needs NO. Q INSECT METAMORPHOSIS—SNODGRASS 61 only to conserve enough undifferentiated material for the reconstruc- tion of the adult in the pupal stage. The embryo and the larva thus become a single independent phase in the life history of the insect, but this fact is not a vindication of the idea that the larva is simply a continuation of the embryo leading a free life instead of being con- fined to an egg shell. The reverse more nearly expresses the truth; the specialized structure of the larva has been forced back on the embryo until the embryo becomes a preliminary larva. A phyloge- netic significance, therefore, cannot be attributed either to the larva or the embryo of a holometabolous insect. The insect larva owes its independence and its ability to take on characters of its own to its release from the necessity of inheriting spe- cial adult characters of its parents. The development of structures practical only to the winged imago must be inhibited throughout the embryonic and larval stages, and conversely, larval organs useful only to the larva may not be transmitted to the imago. In this way both the larva and the adult are free to become more and more specialized in different directions, but the greater their divergence, the greater becomes the degree of reconstruction required of the pupa. Yet the larva, no matter how divergent it may become from the line of adult phylogeny, must carry the adult inheritance as well as its own. The potency for redeveloping the parent form either resides in the ability of larval tissues to be transformed into imaginal tissues, or it is carried by undifferentiated embryonic cells of the larva, which resume the imaginal development in the pupa. In the more intense degrees of pupal metamorphosis, as Tiegs (1922) has said, the changes amount at times to an absolute death of the larva, the tissues of which go into almost complete dissolution, and if imaginal reconstruction cells were not present the larva would be left to decompose. X. LARVAL HETEROMORPHOSIS Heteromorphosis of the larva, commonly called hypermetamor- phosis, is of frequent occurrence among predaceous and parasitic species of insects, examples being known in Neuroptera, Coleoptera, Strepsiptera, Lepidoptera, Hymenoptera, and Diptera. It seems re- markable that a larva can assume two or more distinct forms during its life history, and the fact that it may do so raises the question as to how the juvenile hormone is able to control a succession of differ- ent forms. However, since this hormone is nonspecific with regard to related species of insects, it should be nonspecific with regard to different larval forms of any one species. The hormone has nothing 62 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 to do with determining the structure of the young insect; this is the work of hereditary factors. The hormone simply maintains the in- tegrity of the juvenile form, whatever this may be, against the forces of further development. The ability of the embryo to develop into a larval form that has no relation to the form of its parents is strange enough, but it is passing strange that this same larva can change its form several times during its larval life and still finally revert to the adult structure. The fact of heteromorphosis appears to demonstrate the plasticity of larval tissues, which seemingly can be molded and remolded by the growth organizer to produce a succession of adaptive forms. The histologi- cal changes that may take place in larval metamorphosis, however, as well as the role of hormones remain yet to be investigated. Two categories of heteromorphosis in parasitic larvae are to be distinguished according as the adult female lays her eggs in the open, or on or within the body or egg of the prospective host of the larva. In the first case the newly hatched larva must be able by its own activity either to find its appropriate host, or to attach itself to a carrier that will transport it to the nest wherein are the host eggs or larvae on which it is destined to feed. A first-instar larva of this type, therefore, is constructed for an active life, and has been termed a planidium (little wanderer), but its structure, of course, will depend on the insect order to which its parents belong. After entry into the nest or body of the host, however, the planidium transforms into a second-stage larva of much simplified form and structure adapted to a sedentary life of parasitism. With those species, on the other hand, in which the eggs are attached on, or inserted into, the body of the host, the young larva begins at once its parasitic existence ; it has no need for an “active stage, and develops directly from the embryo into a form adapted only for life and feeding usually within the host, and accordingly in many species it is greatly reduced and simplified in structure. During later instars, however, the simple larva takes on a form more typical of the usual larva of its order. PARASITES WITH A PLANIDIAL STAGE The term planidium has a functional rather than a structural sig- nificance, but it is remarkable how larvae in different orders have taken on similar characters in adaptation to the requirements of planidial life. Coleoptera.—Larval heteromorphosis among the Coleoptera occurs in the Carabidae, Staphylinidae, Meloidae, and Rhipiphoridae. Most NO. 9 INSECT METAMORPHOSIS—SNODGRASS 63 familiar are the life histories of the blister beetles, Meloidae, some of which feed on the eggs of grasshoppers, others infest the nests of bees. The transformations of species of the American Epicauta are well known from the early work of Riley (1876) and later papers by Ingram and Douglas (1932) and Horsfall (1941). The European Mylabris variabilis is described and fully illustrated by Paoli (1938). The adult females of Epicauta and Mylabris deposit their eggs in the ground where grasshoppers are likely to be, but not necessarily Fic. 11.—Three larval stages of a meloid beetle, Mylabris variabilis Pall. (from Paoli, 1938). A, first instar, planidium. B, same, more enlarged. C, second instar. D, fourth instar, similar to third and fifth instars. close to a grasshopper’s nest. The first-stage larva is a planidium hav- ing the form of an active generalized coleopterous larva with long slender legs (fig. 11 A,B). It is commonly termed a “triungulin,” though two of its pretarsal “claws” are merely strong spines. The planidium runs actively about and burrows into the ground until it finds the egg nest of an acridid. After feeding on a few eggs, it moults and transforms into a more simple short-legged, soft-bodied second instar (C). This larva resumes feeding, grows, and goes through two more stages in which it becomes a thick scarabaeoid grub (D). The next instar, which is the fifth, resembles the preceding, but it comes out of the egg nest and burrows downward a short distance into the ground. This larva in Mylabris, according to Paoli, does not feed, and transforms into a sixth larva, in which the integument is thick, rigid, and dark-colored, and the mandibles and legs are much 64 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 reduced. This sixth larva, the “ipnotica” of Paoli, is immobile and passes the winter in a dormant condition. In the spring it sheds its tough, protective integument. The seventh larva that emerges resem- bles the fourth and fifth instars; it is again active, though it does not feed, and burrows upward to near the surface of the ground, where it transforms into the pupa, from which finally the adult emerges. The life history of Epicauta is essentially the same as that of Mylabris, though according to Horsfall (1941) the fifth larva of E. pennsylvanica feeds to repletion before it burrows down into the ground. Moreover, this fifth larva in species of Epicauta may trans- form directly into the pupa, thus eliminating the hibernating form and the seventh instar. Pupation following the fifth instar is said by Ingram and Douglas (1932) to take place with individuals of Epi- cauta lemniscata that complete the fifth stage in the spring, while those maturing in the fall or under unfavorable weather conditions go over into the hibernating stage, which is followed by the active seventh instar. Horsfall (1941) reports the same thing for Epicauta pennsylvanica. A notable feature in the metamorphosis of these meloid larvae is its reversibility, as shown by the transformation of the hibernating larva into an active burrowing form like that which preceded it, though geotropically one is positive and the other negative. Other species of Meloidae are parasites in the nests of bees in the families Megachilidae and Andrenidae. The life history and larval stages of one of these, Tricrania sanguinipennis, infesting the under- ground nests of the andrenid Colletes rufithorax is fully described by Parker and Boéving (1925). The female of Tricrania deposits her eggs under small objects lying on the ground in the vicinity of the nesting places of the bees. The newly hatched larvae are slender planidia, tapering at each end, with long legs and well-sclerotized body segments. It would appear that they might find their way di- rectly into the nest of a prospective host, but observations show that generally they attach themselves to a male bee seeking a female and are thus carried into the nest. Within the brood cell the intruder first devours the egg of the bee, thus making sure of no competition from the bee larva that might otherwise hatch. At the first moult the planidium transforms into a soft, smooth larva having a boat-shaped form with the spiracles on the back, an adaptation that enables the larva to float on the food mass of honey and pollen in the cell, which constitutes its food from now on. At later stages, however, as the larva grows larger and the food mass shrinks, the larva becomes a fat scarabaeoid grub. In all, the Tricrania larva goes through six NO. 9 INSECT METAMORPHOSIS—SNODGRASS 65 instars, but, except for a shortening of the legs and other minor modi- fications, it makes no radical change of form after the second moult. There is no hibernating larval stage in the life of Tricrania, but the fifth and sixth instars remain within the unbroken fourth and fifth skins, which serve also as a covering for the pupa. The adult beetles are formed in the fall, but remain within the bee’s nest until the following spring. The metamorphosis of the carabid Lebia scapularis, which is pre- daceous on the larvae of the elm leaf beetle, Galerucella luteola, is described by Silvestri (1904) as follows. The young Lebia is a slen- der, elongate larva of the planidium type, having legs adapted to run- ning, well-developed mandibles, and a pair of long, jointed apical processes on the abdomen. It attacks a Galerucella larva and feeds on the viscera until its growing body becomes so large and loaded with fat to such an extent that it can no longer move actively about. In this condition it might fall an easy prey to other insects, but the Lebia larva now encloses itself in a cocoon spun of silk threads from the Malpighian tubules, and finally includes its prey in the cocoon. When finished with feeding, and having attained its maximum de- velopment, this first larva moults into a second form having a general pale color, mouth parts unadapted to feeding, the legs and antennae reduced to small conical stumps, and the caudal processes suppressed. From this second, nonfeeding instar the larva goes into a prepupal stage, in which the head takes on adult characters, and wing rudi- ments are present on both the mesothorax and the metathorax. After another moult the prepupa becomes a pupa. Silvestri makes no com- ment on the unusual occurrence in the Coleoptera of a prepupa, which evidently belongs to the pupal stage of the insect. Heteromorphosis in Lebia, therefore, appears to affect the pupa as well as the larva. Heteromorphosis again occurs in several genera of Staphylinidae in which the larvae are parasitic on the pupae of Diptera within the puparium. Wadsworth (1915) gives a good account of the life his- tory and larval stages of Aleochara bilineata, a parasite of the cabbage fly, Chortophila brassicae. The newly hatched larva is an active thysa- nuriform planidium that must seek in the ground the puparium of the cabbage fly. Having found a puparium it gnaws a hole in the latter and feeds on the outside of the pupa from a puncture in the pupal integument until it becomes much swollen. The second instar of the larva is quite different from the first; the cuticle is soft and white, the antennae and mouth parts are altered, the legs reduced to vestiges, the claws are lost, and the caudal spines disappear. The third 66 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 larva resembles the second except for its larger size. Both the second and the third larvae lie lengthwise on the back of the thorax of the fly pupa, and obtain their food by suction. Pupation takes places in the fly puparium, and the adult beetle gnaws its way out. The larval heteromorphosis of the Rhipiphoridae is too well known to need more than a brief notice. Species of Rhipidius are internal parasites in all larval stages on cockroaches. Other species attacking wasps and bees are endoparasitic in the first instar but take an external position in later instars. The first larva of one of these species is an active planidium which must find and attach itself to a carrier that will transport it to the nest of a prospective host. Here it enters the host larva as an internal parasite. When fully grown in the first in- star, however, it leaves the body of the host through a puncture, moults, and in the second stage takes a position across the back of the host larva on the first or second thoracic segment. The external larva loses the features of the first instar and becomes a grublike parasite, some species being characterized by the presence of large tubercles on the back. Neuroptera-—Among the Neuroptera the larvae of nearly all spe- cies are predaceous, their prey being mostly other insects which they attack in the open. The larvae of some Mantispidae, however, feed on spider eggs within the spider’s cocoon. The mantispid eggs being laid on trees or bushes, the young larva must actively find its food. The life history of Mantispa styriaca has long been known from the work of Brauer (1869). The newly hatched Mantispa is a simple, slender neuropteroid larva with relatively small mandibles and no distinctive specialization. Hatched in the fall, it hibernates through the winter ; in the spring it finds a spider’s cocoon and cuts its way through the silken wall. With feeding in the first instar, the abdomen becomes greatly enlarged, but at the first moult the larva changes to a fat grub with a small head and greatly reduced legs. This change of the active first-stage mantispid larva to a sedentary grub is cer- tainly not a reversion to any ancestral larval form among the Neurop- tera; it is an individual secondary adaptation to the life of ease and plenty the larva is to lead from now on in the protection of the spider’s cocoon, within which it finally pupates. Strepsiptera.—The Strepsiptera are notable for the heteromorphosis of the parasitic larval stages of both sexes, and also for the fact that in most species the sexually mature female retains the larval form, though with a greatly modified reproductive system, and remains within the body of the host. In the genera Eoxenos and Mengenilla, however, the female leaves the host and in the adult stage is found NO. 9 INSECT METAMORPHOSIS—SNODGRASS 67 in the open, either free or enclosed in the last larval skin. The females of these species are much less modified in structure than are the fe- males of species that remain in the hosts. The males of all species are free, fully winged insects. The adult female of Eoxenos laboulbenet, as described by Parker and Smith (1933), is broadly oval, with a distinct head and thorax and a 10-segmented abdomen ; wings are absent, but the legs are rela- tively long and segmented, mandibles are present though simple, and spiracles occur on each of the first seven abdominal segments. At the posterior border of the seventh abdominal segment is a genital aper- ture leading into a short, open, median oviduct, but otherwise noth- ing is to be seen of the reproductive system; in the mature female the entire abdominal cavity is full of eggs. Females of Eoxenos found within the last larval skin are enveloped also in a thin pupal cuticle, showing that, in this genus at least, the female is a true imago. In mating, as observed by Parker and Smith (1934), the male of Eoxenos curves his abdomen beneath that of the female, but the aedeagus pierces the integument of the female instead of entering the genital aperture. The eggs hatch within the body of the female and the young planidial larvae escape through the open inner end of the oviduct. The host of Eoxenos laboulbenei was for a long time un- known, but Carpentier (1939) finally discovered the parasitic stage of the larva in the body of a lepismatid, Lepisma aurea. In other strepsipteran genera, parasitic in Orthoptera, Pentatom- idae, Fulgoridae, Cicadellidae, and particularly in Hymenoptera of many families, both the female and the male develop to sexual ma- turity within the body of the host. The female remains within the host, and retains the form of the mature larva, having a large, soft abdomen and a short, cylindrical, darkly sclerotized cephalothorax (fig. 12 G), which latter alone is thrust out of the abdomen of the host. Mandibles are present in some species, absent in others, but the female is always wingless and legless. She remains enclosed in the last larval skin, and the parasitic females are not known to have a pupal stage. It is questionable, therefore, whether the egg-producing parasitic female is a true adult or a sexually precocious last-stage larva. As noted above, Parker and Smith found evidence of a pupal stage in the nonparasitic female of Eoxenos laboulbenet. The reproductive organs of the parasitic females are greatly re- duced, and the abdomen is filled with a great mass of eggs. The de- velopment of the eggs free in the body cavity is described by Brues (1903) in Xenos peckti. Between the ventral surface of the body of the female and the enveloping larval skin is a free space, or brood 68 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 chamber, which opens anteriorly at the base of the cephalothorax by a median slit, or in some species by a pair of apertures. The brood chamber is in communication with the body cavity of the female by several funnel-shaped tubes. During mating, according to Perkins (1918), the male of Stylops aterrima inserts the aedeagus into the an- terior opening of the brood chamber; in Acroschismus wheeleri, Schrader (1924) says the spermatozoa, after being discharged into the brood chamber, find their way through the ventral ducts of the female’s abdomen into the body cavity, where they disperse, penetrate the egg membranes, and effect fertilization. Silvestri (1940), how- ever, has apparently demonstrated that the male of Halictophagus tettigometrae, in inserting the aedeagus through the ventral mem- brane between the head and thorax, penetrates the body wall of the female and discharges the spermatozoa directly into the haemocoele, whence they finally migrate to the posterior extremity of the abdo- men. The young larvae on hatching from the eggs escape from the body of the female through the ventral funnels into the brood cham- ber, and gain the exterior by way of the anterior opening of the chamber. The male strepsipteron develops also inside the body of the host, and before emergence as an adult he is enveloped by the last larval skin. Unlike the female, however, the male goes through a pupal stage before transforming into a free-winged insect, leaving the pupal cuticle behind within the larval skin. For a good example of the larval stages of a typical strepsipteron we may refer to the well-illustrated account by Kirkpatrick (1937) of the life history of Corioxenos antestiae, a parasite of Pentatom- idae infesting coffee plants in East Africa. The first-instar larva is a planidium (fig. 12 A) of coleopterous type of structure, and attaches itself (B) to an immature pentatomid of the genus Antestia. The parasite remains motionless on the host until the latter moults, when it bores into the body through the soft new skin. At its own first moult the planidium transforms into a simple, soft-bodied, legless scarabaeoid grub (C), in which even body segmentation is not visible. With succeeding moults the larva goes through four more instars (D,E,F), without any radical change of form except for the develop- ment of a row of eight processes along the back of the abdomen. The larva apparently feeds by the absorption of body liquids of the host through its skin, and the dorsal protuberances are supposed to increase the absorptive area. During the later larval stages (F) the body be- comes differentiated into a slender cephalothorax and a large abdo- men ; extrusion of the cephalothorax from the host takes place in the NO. 9 INSECT METAMORPHOSIS—-SNODGRASS 69 seventh instar, after which the female larva moults to the final form (G) within the last larval skin. The larval instars of the male resemble those of the female, but the male goes through a pupal stage before issuing as a winged adult. Fic. 12.—Developmental stages of a strepsipteron, Corioxenos antestiae Blair (from Kirkpatrick, 1937). A, first instar, planidium in waiting attitude (length 0.25-0.27 mm.). B, same, in position of attachment on host. C, first parasitic instar (length 0.4 mm.). D, second parasitic instar, female. E, third parasitic instar, female. F, fifth parasitic instar, female. G, mature female, unfertilized (length 3 mm.). Extrusion of the cephalothorax of Corioxenos antestiae, Kirk- patrick says, is always between the back plates of the third and fourth segments of the host, the male in the middle and the female on one side. In this species the female has a pair of openings into the brood pouch, one right, the other left, a provision to insure that one or the other will not be covered by a wing of the host. The body of the mature larva and also of the adult female lies in the body of the host with the ventral side of the abdomen uppermost and the cephalothorax 7O SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 bent posteriorly, so that the dorsal surface of the exposed cephalo- thorax is uppermost when extruded. In this position of the female copulation with a free male takes place. An even more detailed account of the biology, life history, and anatomy of a strepsipteron will be found in the paper by Silvestri (1940) on Halictophagus tettigometrae Silv. Lepidoptera.—The caterpillar in its body form is the most con- servative of all holometabolous larvae, even predaceous species in general preserve the eruciform type of structure. In the Epipyropidae, however, the larvae of which are external parasites on Homoptera, particularly Fulgoridae, there is a pronounced structural adaptation of the larva to parasitic life and even a heteromorphosis. Since the adult female deposits her eggs not on a prospective host but on vege- tation, the first-stage larvae must attain a host by their own efforts, and they resemble, as much as a caterpillar might, the planidia of other parasites with similar habits. The newly hatched larva of Aga- mopsyche threnodes is described by Perkins (1905) as a minute, slender creature, tapering to the caudal extremity, and provided with legs unusually long for a caterpillar ; it is clearly adapted for the ac- tive life of a young predaceous insect that must find a host for itself. The later instars, which.feed on the back of the abdomen of the host, are very different from the first. In the mature stage the head is ex- tremely small, the legs reduced, the mandibles minute; the body be- comes contracted to an oval form, and the larva takes on a superficial resemblance to a mealy bug, accentuated by the presence of a waxy covering. A description of all the stages of Epipyrops eurybrachydis Fletcher is given by Krishnamurti (1933). Among the Lepidoptera various leaf-mining species also undergo a change of form during larval life, being at first flattened for feeding within the leaf, and later, on emergence from the mine, taking on the usual caterpillar form for cocoon spinning. Diptera.—Parasitic dipterous larvae, of which the first instar is of planidium type, and which, therefore, are heteromorphic, are said by Clausen (1940) to occur generally in the Acroceridae (Cyrtidae), Bombyliidae, and Nemestrinidae, frequently in the Tachinidae, and in a few species of Sarcophagidae. The Acroceridae (Cyrtidae, Oncodidae) are parasitic in their larval stages on spiders. The female deposits her eggs on bushes or trees, and the young larvae by their own efforts must attach themselves to spiders that chance to come their way, if they are to survive. The larval stages of Oncodes pallipes as described by Millot (1938) may be taken as typical of the family. The newly hatched planidium (fig. NO. 9 INSECT METAMORPHOSIS—SNODGRASS 71 13 1) is not over 0.4 mm. in length, slender and elongate, with a small head and 11 body segments. The body segments are sclerotized dor- sally and ventrally and are armed with strong spines, a pair on the last segment being particularly long. The mouth armature includes a median sharp-pointed process and a pair of lateral hooks. The last abdominal segment terminates in an attachment apparatus consisting of three strong central hooks and a ventral semicircle of small spines. The larva at this stage is metapneustic, having a pair of spiracles only on the last segment. After hatching, the larva stands vertically by means of the attachment structure on the end of its abdomen, but it is capable of locomotion either by looping movements like those of a measuring worm, or by small leaps of a few millimeters made by suddenly straightening the curved body. If a young spider happens to pass close by, the planidium springs upon it and penetrates into its interior ; otherwise the prospective parasite will die in the course of a few days. The parasite passes the winter without change in the body of the spider. In the spring it moults into a second instar and later again into a third instar (J). In these instars the larva is simply a small fly maggot; the body is indistinctly segmented, tapering an- teriorly, enlarged posteriorly, and ends with a small apical cone. There are now two pairs of spiracles but those of the prothorax are not func- tional. The infested spider remains alive and normally active almost to the end, but at last the parasite consumes the vital organs of its host and comes out to pupate, leaving nothing of the spider but the empty skin. The planidium of Pterodontia flavipes (fig. 13 H), another ac- rocerid parasite of spiders, described by King (1916), resembles that of Oncodes, but the body ends with a small adhesive disc between the bases of a pair of long, slender spines. This larva, according to King, progresses either by looping in the manner of a leech, or by jumping. Preparatory to making a leap, the larva stands erect on the attach- ment disc with the caudal spines extended backward; by a sudden downward pressure of the spines the larva then throws itself a dis- tance of five or six millimeters. When on moist surfaces, however, King says, the larva progresses by extending and contracting its body. This last observation is of particular interest because it shows that the planidium still retains the common mode of locomotion of a fly maggot. In its subsequent stages the Pterodontia larva returns to the form of a simple, smooth-skinned maggot, which, when mature, emerges from the body of the spider. For another example of larval heteromorphosis among the Diptera, we may refer to the paper by Clausen (1928) on Hyperalonia oeno- 72 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 maus, a bombyliid larval parasite of the scoliid Tiphia, which itself is parasitic on grubs of the scarabaeid genus Anomala. The eggs of Hyperalonia are deposited on the ground or dropped there by the female in flight. The first larva (fig. 13 G) on hatching is a slender, vermiform planidium 0.9 mm. in length, with a strongly sclerotized head and 12 uniform body segments; the thoracic segments bear each a pair of long, slender lateral spines, and on the apical segment of the abdomen is a pair of similar but longer spines directed posteriorly. This larva has to search through the ground for the buried cocoons of Tiphia; after entering a cocoon it feeds on the thoracic region of the Tiphia larva. At the first moult the planidium changes into a much simpler larval form, which lacks the body spines and the strong sclerotization of the head, and is characterized by deep intersegmen- tal constrictions. In the third stage (F) the larva becomes thick- bodied and grublike, but is not essentially different from the second larva; it passes the winter in the cocoon of the host, and pupates the following spring. The same species attacks also other scoliid genera, and the Bombyliidae in general, according to Clausen, are parasitic on Orthoptera (egg cases), Coleoptera, Lepidoptera, Diptera, and Hymenoptera. Hymenoptera.—Among the Hymenoptera, larval heteromorphosis following a first-stage planidium occurs in the parasitic Perilampidae and Eucharidae. The females in these families lay the eggs apart from the host, and the young larvae are provided with a strongly sclerotized integument which allows them to live a relatively long time without desiccating and without feeding. By means of a caudal sucker and long tail bristles the planidium is able to stand erect and to spring at a prospective host. The following account of the planidium of a species of Perilampus parasitic on larvae of Chrysopa is given by H. S. Smith (1917). The eggs are laid on the leaves of plants where the Chrysopa larvae are looking for aphids. From the egg hatches an active planidium (fig. 13 A), which at first crawls rapidly about, but soon attaches itself to the leaf by its caudal sucker and stands up at a right angle to the leaf surface. In this position it may remain motionless for days at a time until some insect comes within its reach. Then suddenly the planidium becomes “frantically active, reaching and swaying back and forth in its attempt to attach itself to the prospective host.” If a Chrysopa larva comes too near, “the planidium attaches itself with lightning- like quickness to a hair or bristle of the host. It then leisurely crawls down the hair to the host’s body and attaches itself by its mouth hooks.”” When the Chrysopa larva spins its cocoon and pupates, the NO. 9 INSECT METAMORPHOSIS—-SNODGRASS 73 Fic. 13——Examples of hymenopterous and dipterous parasitic larvae with a planidial first instar. A, Perilampus chrysopae Crawford, planidium (from Smith, 1912). B, Peri- lampus hyalinus Say, planidium (from Smith, 1912). C, Schizaspidia tennicornis Ashm., planidium (from Clausen, 1923). D, same, second instar (from Clausen, 1923). E, same, third instar (from Clausen, 1923). F, Hyperolonia oenomaus Rond., third instar (from Clausen, 1928). G, same, first instar (from Clausen, 1928). H, Pterodontia flavipes Say, first instar (from King, 1916). I, Oncodes ie Latr., first instar (from Millot, 1938). J, same, third instar (from Millot, 1938). 74 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 planidium feeds as an external parasite on the pupa. Often, however, . the parasite attaches itself to the stalk of a Chrysopa egg, in which case the young chrysopid falls a sure victim to the Perilampus pla- nidium in wait for it. Another species of Perilampus described by H. S. Smith (1912) is a secondary parasite on the fall webworm, Hyphantria cunea. The planidium (fig. 13 B) enters the body of the caterpillar through the skin and searches for the larva of a primary parasite, including both dipterous and hymenopterous species. At the first moult the perilam- pid larva loses the characteristic features of the planidium and changes into an ordinary hymenopterous grub, in which form it remains through subsequent instars with only slight modifications. The description by Clausen (1923) of the life history of a Japanese eucharid, Schizaspidia tenuicornis Ashm., parasitic on ant larvae, will serve as a good example of the nature of the planidium and the heteromorphosis of the larva in the Eucharidae. The eggs of this species are laid by the females during the later part of summer in the buds of trees and hatch the following spring. The newly emerged larva (fig. 13 C) is a planidium scarcely more than one-tenth of a millimeter in length, having suctorial mouth parts and a pair of sharp mandibles, and is provided with a small adhesive disc at the posterior end of the abdomen, which is armed with strong spines. Locomotion is accom- plished by successive loopings and extensions of the body as the latter is held to the support alternately by the mouth and the caudal disc. When awaiting the chance arrival of a prospective host, however, the planidium stands up at an angle of 45 degrees on its caudal sucker, and then, when opportunity offers, it attaches itself by its mandibles to a passing ant, and is thus transported to the ant’s nest. Here the parasite is brushed off from its carrier and now attaches itself by its jaws to an ant larva. At the first moult the special characters of the planidium, together with the mandibles, are cast off with the exuviae. The second instar of the parasite is a simple, thick, grublike larva (fig. 13 D) having only suctorial mouth parts; it maintains its hold on the host by the mandibles of its own cast skin. When now the ant larva becomes a pupa, the parasite frees itself from the larval exuviae of the ant and by means of its oral sucker attaches itself to the pupa. It then moults to its third instar (E), in which the body segmentation is lost and the mouth is armed with a short stiletto for puncturing the skin of the pupa. The ant pupa is now sucked dry and soon dies, after which the fully fed parasite pupates. Though the Schizaspidia larva assumes a characteristically different form in each of its three instars, the pupa is typically hymenopteran. NO. 9 INSECT METAMORPHOSIS—SNODGRASS 75 The larval history of Schizaspidia tenuicornis shows how complex the life of a parasite may be, and how both in its structure and its instincts the young insect must become adapted in each instar to con- form with the particular conditions that confront it. As noted by Clausen, the Schizaspidia larva, in losing its mandibles, breaks with all other hymenopterous parasites, in which the mandibles are retained in all stages. PARASITES WITHOUT A PLANIDIAL STAGE Finally we come to those dipterous and hymenopterous parasites of which the female deposits her eggs directly on or in the body of the host or in the host egg. In these species the young larva on hatch- ing finds itself in immediate contact with its food supply, and there is hence no need of an active stage in its life history. The larva is structurally adapted during its embryonic development for life in the body of the host, and in many cases, especially with hymenopterous parasites, the adaptive modifications result in a greatly simplified larval form. Diptera—Among the Diptera, modifications or special structural developments of endoparasitic larvae appear to be related principally to the function of respiration, but they may be superposed on a state of simplification in which most of the usual vital organs are not yet developed. An extreme case of reduction or of delayed development accom- panied by specialization in the first-stage larva of Diptera is seen in the agromyzid Cryptochaetum, parasitic in scale insects, described by Thorpe (1931, 1941). The eggs of the fly are inserted into the body of a half-grown scale before the body wall has become hardened. The first-stage larva of C. iceryae, according to Thorpe (1931), is little more than a transparent cylindrical sac (fig. 14A), 0.3 to 0.4 of a millimeter in length. There is no mouth or sclerotized mouth parts, no somatic muscles, no spiracles, tracheal system, or heart. The ali- mentary canal is complete, but the stomodaeum and the proctodaeum are not open into the mesenteron, and no food is present in the tract ; the parasite evidently absorbs nutriment through its integument from the body liquid of the host. A special feature of the larva is the presence of a pair of large, fingerlike diverticula containing blood projecting from the posterior end of the body. In the second-stage larva (B) the body becomes distinctly segmented, and the posterior segments are ringed with short spines ; the mouth is open and strongly sclerotized mouth parts are present; there is a tracheal system but no 76 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 spiracles, and a few longitudinal muscles have been developed. The caudal diverticula of the first instar have lengthened into a pair of tails nearly half the length of the body, and fine tracheal branches later penetrate into their open basal parts. In the third stage the body preserves the general form and structure of the second stage, but the tails have increased greatly in length, being one and a half times or more the length of the body. In its fourth stage (C) the larva Fic. 14.—Three larval stages of an agromyzid dipteron, Cryptochaetum iceryae (Will.), parasitic in the coccid Icerya purchasi Maskell (from Thorpe, 1931). A, first instar. B, second instar. C, fourth instar. becomes an ovoid, yellowish-white maggot composed of a head and 10 body segments ; the tails are greatly lengthened, slender filaments, but have become brittle and are easily broken. Each body segment has a belt of minute spines around its anterior end, anterior and pos- terior spiracles are now present, but the hooklike posterior spiracles are still closed, the alimentary canal is open, the muscular system is fully developed. In Cryptochaetum striatum (Thorpe, 1941) the larval stages are said to be much the same as in C. iceryae, but in the third stage the respiratory tails are Io times the length of the body and are filled for at least two-thirds of their length with fine tracheal branches. In contemplating a larva of such incomplete structure as that of NO. 9 INSECT METAMORPHOSIS—SNODGRASS Ti. the first instar of Cryptochaetum, the question comes up as to how it got that way. The usual answer to the question is that the embryo hatched at an early immature stage. Concerning the “early hatching” idea, Thorpe (1931) says: “The theory obviously cannot be pushed too far, for there are many truly adaptive characters which arise de novo in insect larvae, and cannot in any way be described as embry- onic.” There is no question that “adaptive characters” may include the suppression of structures that are temporarily useless, as well as the development of new structures that are only temporarily useful. Nature is always economical where there is no need of prodigality. A larva living in the midst of liquid food which it absorbs through its skin has no use for a mouth, feeding organs, or a functional alimen- tary canal, and no need of a locomotor muscular system. If also it can get sufficient oxygen by absorption from the medium in which it lives, there is no immediate need of a tracheal system. All these negative conditions might be supposed to have been acquired by the simple expedient of early hatching, but the larva, if so produced, is not a normal early-stage embryo. The retarded state of development very probably was early determined in the egg, and the larva must then be what it is regardless of when it hatches. The principal new structures of the Cryptochaetum larva, Thorpe points out, are the respiratory tails. Otherwise the larva simply develops the other or- gans when they are needed. The delay in development is a mere economy, and numerous examples of various degrees of economy might be cited from other species. Hymenoptera.—In the Hymenoptera endoparasitic first-stage larvae often have such strange forms that they would hardly be known for young insects if their development had not been followed. Clausen (1940) distinguishes, describes, and illustrates 14 different types of first-stage parasitic larvae in the Hymenoptera, nearly all of which but the planidium are endoparasitic. The eggs of some species are deposited on the outside of the host, of others in the body cavity of the host, and of still others in the host egg. The so-called “egg para- sites,’ however, Clausen observes, are truly larval parasites, since they feed on the larva and “their development is primarily at the expense of that stage.” In the present discussion we are concerned entirely with the forms of these first-instar larvae, which later take on the more conservative structure of typical hymenopterous grubs. The species are therefore heteromorphic, though their heteromorphism affects principally the first instar. The change to the final form may take place at the first moult, but often the second instar is inter- mediate in form between the first and the following instars. As with 78 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I22 the parasitic larvae of Diptera, these aberrant hymenopterous para- sites present various special developments in combination with differ- ent degrees of undevelopment of usual organs. Whatever their form or structure may be, however, we must assume that in some way it is fitting to the life these larvae live. As an example of greatly simplified and specialized first-stage larval structure in the Hymenoptera we may take the braconid Helori- morpha antestiae, an internal parasite of the pentatomid Antestia, de- scribed by Kirkpatrick (1937), or the similar larva of the ichneumonid Limnerium validum, endoparasitic in the fall webworm, described by Timberlake (1912). In each of these species the first-instar larva (fig. 15 C) has an enormous “head” on a relatively small, simple, un- segmented body ending in a long tapering tail. The only appendages present are a pair of slender, incurved, sharp-pointed mandibles. An even simpler larva of the same type is that of Platygaster marchali (E). In the second stage the Limnerium larva takes on a vermiform type of structure with a small head and 12 body segments, the tail of the first instar being greatly shortened. The third instar, as also that of Helorwmorpha antestiae (fig. 15 D), is a typical hymenopterous larva. The heteromorphosis of these species, therefore, results from the extreme modification of the first instar ; in its subsequent changes the larva merely returns to the usual form. A somewhat more specialized type of first-instar larva occurs among the Platygasteridae, examples of which are here illustrated at A,B,F, and I of figure 15. The large anterior part of the body carries the mandibles, antennal rudiments, and a pair of simple posterior appendages. This headlike part of the larva has been shown by Marchal (1906) to be a cephalothorax bearing the antennae, mouth parts, and the prothoracic legs. The body region behind the cepha- lothorax is partly or entirely segmented, and may end with tail ap- pendages of various patterns. In their development these larvae even- tually attain the form and structure of an ordinary hymenopterous grub. A curious type of first instar larva is characteristic of the Sceli- onida; it is classed by Clausen (1940) as the “teleaform” type of larva, but in form it suggests the embryo of a mouse (fig. 15 J). Hadronotus ajax, an egg parasite of the squash bug, Anasa tristis, furnishes a good example. The newly hatched larva (J) as described by Schell (1943) is a slender creature with a sharp, tail-like caudal horn curved anteriorly. The body is constricted between a large an- terior part, probably a cephalothorax, and an elongate posterior part, NO. 9 INSECT METAMORPHOSIS—SNODGRASS 79 but is unsegmented. The cephalothorax bears anteriorly a pair of large, soft mandibles, and posteriorly a “labial projection.” The caudal horn is a feeding accessory. This larva grows by a great in- crease in the size of the abdomen only. In the second stage the larva takes on an oval saclike form, still without segmentation. The third instar, however, is a fully segmented, typical hymenopterous larva (K). Finally, we must note that not all parasitic hymenopterous larvae take on queer forms in the first instar. Among the Proctotrypoidea the larva of Phaenoserphus viator, parasitic on a carabid beetle larva, as described by Eastham (1929), hatches in the form of a simple grub (fig. 15 H), in which the abdomen becomes fully segmented during the first instar. The only special character of this larva is the presence of small paired ventral papillae on the eight body segments following the prothorax. On the head, according to Eastham, are a labrum, a pair of antennal papillae, a pair of sickle-shaped mandi- bles, a pair of simple maxillary lobes, a small labium, and a sclerotized ring supporting the mouth parts. Advocates of the Berlese “early hatching” theory would explain the simplicity of these first-instar parasitic larvae as products of im- mature eclosion of the embryo. Thus Chen (1946), who discredits the theory as applied to other larvae, says: “The precocious types are confined to parasitic Hymenoptera and appear to have been inde- pendently acquired by the different groups.” He then distinguishes among these first-stage larvae a “‘vermiform polypod” type (fig. 15H), an “oligomerous protopod” type (A), and a “polymerous protopod” type (F), supposedly representing successively earlier stages of embryonic development. The usual implication of this theory is that the different types of larvae correspond with phylogenetic stages presumed to be recapitulated in embryonic development. The presence of apparent abdominal appendages on the first-instar larva of Phaenoserphus viator (fig. 15 H) gives this larva a polypod appearance, but Eastham (1929) says the abdominal papillae may be merely adaptive structures. He notes that the difficulty of ascribing such a larva to a primitive embryonic stage “lies in comparing the whole larva at any one stage in its life with any single embryonic state.” The presence on the head of fully developed, typical hymenop- terous larval mouth parts does not harmonize with the idea that the larva respresents an early polypod stage of the embryo. The presence of mandibles on such a simplified larva as that of Helorimorpha (C) likewise shows that the form of this larva has no embryonic or phylo- 80 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 Fic. 15.—Examples of hymenopterous parasitic larvae without a planidial first instar. A, Platygaster herrickiit Packard, first instar (from Kulagin, 1898). B, Platygaster instricator Kulagin, first instar (from Kulagin, 1898). C, Helori- morpha sp., first instar (from Kirkpatrick, 1937). D, same, mature larva (from Kirkpatrick, 1937). E, Platygaster marchali Kieffer, first instar (from Marchal, 1906). F, Synopeas sp., first instar (from Marchal, 1906). G, same, embryo (from Marchal, 1906). H, Phaenoserphus viator Hal., first instar (from East- ham, 1929). I, Tricacus remulus (Walker), first instar (outline from Marchal, 1906). J, Hadronotus ajax Girault, first instar (from Schell, 1943). K, same, third instar (from Schell, 1943). NO. 9 INSECT METAMORPHOSIS—SNODGRASS 81 genetic significance. The other appendages have simply been sup- pressed as needless. The same may be said of the so-called “‘oligomerous” and “‘poly- merous protopod” larvae (fig. 15 A,B,F,I). They do not as a whole have the structure of any one stage in ordinary embryonic develop- ment, and none of them is suggestive of being a primitive embryo. An embryo develops continuously, but these larvae maintain the form and structure they have at hatching until the first moult, as does any ordinary larva. In short, there is no reason for regarding them as embryos. Just as a free, active, first-stage larva, or planidium, is adapted to the predatory life it must lead, so these internal parasitic larvae are adapted to an endoparasitic life. They are specialized both in the forms they have, and in the developmental retardation of organs they do not have and do not need. The principle of economy is in- voked here just as with the simplified dipterous larvae. In the first-stage Hadronotus larva (fig. 15 J) we see again an ex- ample of early specialization in form accompanied by retardation in the development of organs not immediately needed. If we consider the numerous other forms of first-instar larva among the parasitic Platygasteridae and Scelionidae, illustrations of which are assembled by Clausen (1940, figs. 108-111, 113), it is clear there is no evident logic in picking out any one form as representing a particular stage of ordinary embryonic development. The development of Synopeus rhanis within the egg from the blastula to the first larva (F), as illus- trated by Marchal (1906, pl. 17), shows that the embryo (G) de- velops directly from the beginning into the platygasterid larval form, without going through any stages suggestive of those of an embryo that develops into a typical free-living larva. Evidently the larval form is determined in the egg, and the embryo, thus relieved from phylogenetic influences, develops into a larva of the platygaster type. The time of hatching has nothing to do with it. An example of heteromorphosis affecting the first larval stage very similar to that in the parasitic Hymenoptera occurs in the pseudoscor- pion (Barrois, 1896; Vachon, 1938). The eggs at an early stage of development are discharged into a brood pouch suspended below the genital aperture of the female and are here nourished on a secre- tion from the ovaries. On hatching, the larva breaks through both the chorion and the wall of the brood pouch, but remains attached to the outside of the latter by its ventral surface and the mouth region. It is now nourished, as were the eggs, by the ovarial secretion dis- charged into the brood pouch. At this stage the young pseudoscorpion is a simple saclike creature with rudimentary appendages, but without 82 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I22 body segmentation or internal organs. A deep musculated invagina- tion on its ventral surface was regraded by Barrois as a sucking or- gan, but Vachon has questioned this function. However, in some manner the larva absorbs the ovarial secretion from the brood pouch and completes its development in one instar. At the next moult it takes on at once the adult structure in miniature. The so-called larva might be regarded as a second embryo, but clearly it is an adaptive form quite unlike any early stage in ordinary arachnid development. The frequency with which larval heteromorphosis occurs among unrelated insects shows that the larval organization is highly unstable and that mutations make it readily responsive to the need of environ- mental adaptation. A case of heteromorphosis among the vertebrates would be most astonishing ; with the insects heteromorphosis is com- monplace. The adaptational changes in the structure of heteromorphic larvae from one instar to the next is good evidence that homomorphic larvae are themselves merely juvenile adaptations to their various modes of living. The ease with which the insect larva assumes a form compatible with its living conditions is well illustrated by the difference between a free-living planidium of one parasitic species and the endoparasitic first larva of another related species. The planidium is equipped for activity, for finding and attacking its prospective host ; the endoparasite is reduced to the bare essentials needed for feeding on an ambient food supply and for mere existence otherwise. It may be noted here, also, that simplification of structure often occurs in the second or following instars, as with species having a planidial first larva, in which case “early hatching” cannot be invoked to account for it. Whatever form the early larva may take on, however, it is incumbent on the larva eventually to return to its parental form, and this it does by first reverting in its later stages to the larval form typical of its order or family. XI. THE PUPAL TRANSFORMATION The insect pupa is one of the most remarkable things in animate nature; within it are intimately mingled the processes of both life and death. With the shedding of the last larval skin the fully formed pupa appears as a rough sketch of the future adult. The visible pupa, however, is only an external shell; inside of it the larval tissues and organs are being replaced by those of the imago. The juvenile hor- mone no longer maintains the larval organization, and in consequence the tissues of the larva have either gone into a state of dissolution, or, under the influence of the developmental hormones, are being recon- NO. 9 INSECT METAMORPHOSIS—SNODGRASS 83 structed into imaginal organs, while other organs of the imago are being formed anew from undifferentiated living cells whose develop- ment had been repressed by the juvenile hormone. Though hormones control or regulate the transformation processes, there resides in the pupa some mysterious organizing force that builds up the imago from the larval material or from special cells that have been carried by the larva from the embryo. When the imaginal structure is ac- complished, the pupal skin is shed and the insect now reappears in the parental form that produced the fertilized egg from which the larva was hatched. The life cycle is thus completed, only to be indefinitely repeated. Various investigators have observed that the cells of tissues, par- ticularly the epidermis, undergoing metamorphosis discharge dark- staining globules from the nuclei. These globules are commonly termed chromatic droplets. Earlier writers, as Pérez (1910) and Poyarkoff (1910), regarded their discharge as a sign of “‘rejuvena- tion” in the larval cells; by the rejection of the droplets the cells were supposed to discard their larval ingredients and to be thus prepared for a new growth. The same globules, however, are observed to re- sult from the dissolution of nuclei, and Wigglesworth (1942), from a review of the evidence, concluded that the droplets are always formed in this way. He noted that they are present in the epidermis during the moults of Rhodnius, and in greatest numbers where nuclei appeared to be formed in excess of the need for new cells. Nuclei become superfluous, he says, “either because they belong to specialized larval structures that are being discarded, or because the exuberance of cell division has led to their production in greater numbers than are needed.” Several writers have observed chromatic droplets also in the growing tissues of the embryo. The epidermis.—Since the newly exposed pupa appears to be al- ready perfectly formed and does not thereafter change externally, it is the ectoderm that undergoes the first reconstruction. The change to the pupal form, however, is not as sudden as it appears to be, since long before the larval skin is cast off the transformation processes had begun in the so-called prepupal stage of the larva, just as each larval stage begins within the unbroken cuticle of the preceding instar. Moulting and ecdysis, therefore, are not synchronous, and the two terms are not synonymous. The method by which the pupal epidermis is formed is not the same in all insects. In various families of the Coleoptera in particular it appears that the cells of the larval epidermis retain a faculty for renewed and differential growth, and that in these insects most of the 84 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 larval epidermis goes over, with changes, directly into the pupal epi- dermis. At the other extreme, in the higher orders the larval cells enter a state of degeneration and are thrown into the body cavity, while the entire pupal epidermis is generated anew from small groups of cells, the imaginal discs, that have remained undifferentiated from the embryo. Imaginal discs of undeveloped appendages, however, are present in all cases, and represent adult structures whose growth is continued during the larval life. In the beetle Sitophilus (Calandra) oryza Murray and Tiegs (1935) say it is usually possible to distinguish in the epidermis even of the very young larva groups of small, more basophile cells that will form the appendages, rostrum, and copulatory organs of the adult, but that there is no distinct imaginal tissue to form the main part of the body wall. Also in Leptinotarsa, according to Patay (1939), the larval epidermis simply undergoes a renewal of developmental activity by which it is transformed into the pupal epidermis without any process of dissolution of its cells. Again, in the chrysomelid Galerucella, Poyarkoff (1910) finds little evidence of destruction of larval cells in the transformation of the epidermis from the larva to the pupa. On the other hand, in Hymenoptera and Diptera there may be a complete renewal of the epidermis from imaginal discs of the larva, accompanied by a destruction of the larval cells. In the thorax the imaginal discs of the appendages not only form the appendages them- selves, but they spread outward on all sides to furnish new epidermis for the thorax, and in the abdomen the pupal epidermis is likewise proliferated from abdominal discs. As the new epithelium spreads from the regeneration centers, the old cells of the larval epidermis go into a state of dissolution and are forced into the body cavity where they dissolve or are consumed by phagocytes. According to Anglas (1901), in Vespa and Apis as the pupal epi- dermis spreads from the proliferation centers, the old epidermis be- comes vactiolated and separated from the basement membrane. The new tissue advances by incorporating what remains of the larval cells, the protoplasm of which is absorbed, digested, and assimilated by the multiplying imaginal cells. The new epidermis is at first plastic, al- lowing the modeling of the pupal form, but later it becomes fixed by the hardening of the new cuticle. Anglas reports there is no phagocy- tosis of the disintegrating larval cells, such as described in some other insects. In the chalcid Nasonia, Tiegs (1922) says that in the newly hatched larva the ectoderm consists of large cells which constitute the greater part of the integument, and of strips of small embryonic NO. 9 INSECT METAMORPHOSIS—SNODGRASS 85 cells which are the imaginal discs of the future pupal integument. In the last part of the final larval instar the larval cells go into a state of cytoplasmic disintegration, which is partly chemical and partly due to the action of phagocytes. At the same time the cells of the imagi- nal discs of the epidermis multiply and spread out, replacing the dis- integrating larval cells, until they re-form the entire body wall, including such internal parts of it as the tendons of muscles, the tentorium, and the thoracic phragmata. The regeneration of the integument in Diptera from imaginal discs has been described by various writers. Wahl (1901) gives a full ac- count of the epidermal regeneration centers in the larva of Eristalis, which on the thorax include the discs of the pupal respiratory trum- pets, the wings, the halteres, and the legs, and on the abdomen epithelial thickenings formed of embryonic cells. Pérez (1910) says the newly generated epidermis of Calliphora on the thorax grows over the larval epidermis, the cells of which are thus rejected into the body cavity and phagocytized. In the abdomen the epidermal renovation is progressive and slow, but here also the old cells are thrown into the body cavity where they become the prey of phagocytes. Finally, we may quote from the more recent paper by Robertson (1936) on the epidermal regeneration in Drosophila. At an early larval period the rudiments of the legs, wings, and halteres, Robertson Says, are masses of embryonic cells sunken into pockets of the ecto- derm, which remain open through hollow stalks. These pockets are the imaginal discs which will regenerate the thoracic epidermis. As development proceeds, the mouths of the stalks become wider and the peripheral parts of the discs expand into the surrounding epi- dermis, the cells of which gradually retreat and are sloughed off into the body cavity, where they are taken up by phagocytes. The imaginal discs continue to expand by cells multiplication until finally they unite and thus replace the entire larval epidermis of the thorax with a new epidermal epithelium, which is that of the pupa and the adult. On the abdomen likewise the larval epithelium is replaced by a new epi- dermis generated from islands of undifferentiated cells. On most of the abdominal segments there are two pairs of these imaginal discs, one pair dorsal, the other ventral, but the spiracles also are centers of regeneration, making thus six discs on each spiracle-bearing seg- ment. On the last segment, however, there is only a single, ventral histoblast. During the early part of the pupal stage the cells of the abdominal discs multiply and spread out, displacing the larval cells, which are rejected into the body cavity and there phagocytized. At 86 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 about the thirty-sixth hour of pupal development in Drosophila the imaginal epidermis is complete. That the body setae may also undergo a metamorphosis is shown by the studies of Krumins (1952) on Galleria mellonella, the wax moth. The setal apparatus consists of the three usual cells, the tricho- gen, the tormogen, and a sense cell. In all larval instars except the first, the setae are slender and hairlike and are re-formed at each moult, but in some cases the sense cell is subepidermal and in others it is intraepidermal. At the moult to the pupa only those larval setae hav- ing intraepidermal sense cells are re-formed on the pupa, and these pupal setae are replaced on the imago by conical setae. The adult, however, acquires also smaller conical setae not represented on the pupa. The appendages.—In the lower orders of holometabolous insects in which the adult mouth parts are not essentially different from those of the larva, and the larval legs are functional external organs, the corresponding pupal appendages are formed simply within the cuticle of the larval appendages. If the adult appendages are to be much longer than the larval appendages, the growing organs become folded beneath the larval cuticle until they can straighten out at the pupal ecdysis. In some cases, however, the lengthening organs push back into pockets of the pupal integument, but if the imaginal organ begins its growth during larval stages it will be accommodated in a pocket of the larval integument. Eassa (1953) very precisely describes the growth of the imaginal antennae of Pieris brassicae, which have their inception in the first larval stage. Each imaginal antennal rudiment is differentiated around the sense cells and trichogenes at the base of the corresponding short larval antenna; as it increases in size it recedes into a pocket of the head wall, and becomes folded upon itself. During the fifth (last) instar the antennal pocket of the forming pupal head is open by a long slit under the yet unshed larval cuticle, from which the antenna will be everted at the ecdysis of the pupa. On the pupal head, however, the antenna has taken a much higher position than that of the larval antenna. The intervening part of the head wall, Eassa shows, is newly generated from the unfolding wall of the antennal pocket. The growth of the antenna and the reconstruction of the head in Pieris is very similar to that which takes place in lower Diptera, ex- cept that in the latter the antennal pouches may include the rudiments of the compound eyes. In the cyclorrhaphous flies the antennae and eyes are developed in pouches of the larval head commonly known as the “frontal sacs,” which are ingrowths behind the frons (not “in- NO. 9 INSECT METAMORPHOSIS—SNODGRASS 87 vaginations of the pharynx” as they are often said to be). With the formation of the pupa the two postfrontal pouches unite, and when everted their walls form a large part of the imaginal head bearing the eyes and the antennae (see Snodgrass, 1953). The imaginal legs of holometabolous insects, in which the larva has external legs, are formed in the usual manner within the larval legs and find space to grow beneath the larval cuticle. If the larva is externally legless, however, the rudiments of the adult legs, which may appear early in larval life, grow within peripodial pockets of the larval epidermis, and are not everted until the moulting of the last larval skin. In the same manner are developed the wings of all endop- terous insects. In the higher orders the everting leg and wing pouches contribute to the formation of the thoracic wall of the pupa. The alimentary canal—Of the three constituent parts of the ali- mentary tract of an insect, the stomodaeum and the proctodaeum are unquestionably ectodermal since they are formed in the embryo as ingrowths of the body wall. The embryonic mesenteron, however, is ordinarily generated from cells proliferated at the inner ends of the stomodaeum and proctodaeum, which, growing respectively rearward and forward, envelop the yolk in a sac, which is the definitive mes- enteron, or functional stomach of the insect known as the ventricu- lus. Because of the mode of its embryonic origin, some writers have insisted that the insect stomach also must be ectodermal. That this interpretation is entirely unnecessary and evidently erroneous, how- ever, has been shown by Henson (1946), who points out that the tissue at the inner ends of the stomodaeum and the proctodaeum represents the anterior and the posterior lips of the closed blastopore, which, according to the rules of embryogeny, should normally gen- erate ectoderm outwardly and endoderm inwardly. The writer (1935) has explained the matter in essentially the same way in showing that the anterior and posterior mesenteron rudiments are remnants of an originally invaginated endoderm that regenerate the mesenteron. As already noted in the introduction, the embryonic method of forming the stomach is an adaptation to life in the egg. Inasmuch as the embryo cannot take its food into its stomach in the manner of its free-living ancestors, the embryonic stomach grows around the food stored as yolk in the egg. The insect stomach, therefore, begins its history with a metamorphic process, but it does not violate the germ- layer theory. Since the diet of an adult insect is often very different from that of the larva, the alimentary canal in most holometabolous insects undergoes a very considerable alteration during the pupal transforma- 88 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 tion, the change affecting not only the form and relative size of its several parts, but also the nature of the epithelial wall. The degree of reconstruction that takes place in the stomodaeum and proctodaeum varies in different insects, but the mesenteron epithelium is probably always renewed from the larva to the pupa, and in some cases it undergoes a second renewal from the pupa to the adult. An interest- ing feature in the metamorphosis of the alimentary canal, however, is that the reconstructive changes do not proceed in the same manner in all insects. The stomodaeum and proctodaeum being of ectodermal origin, their changes in the pupal metamorphosis are similar to those of the epidermis. They may be merely remodeled by a renewal of activity in their cells without any cell destruction, or they may be partly or wholly regenerated from proliferation centers, accompanied by a de- generation and elimination of the old larval cells, which are thrown off into the body cavity. Where the proliferation centers are best dif- ferentiated they take the form of circular bands of cells at the inner end of the stomodaeum and the proctodaeum, termed the anterior and posterior imaginal rings. Reconstruction of the stomodaeal and proctodaeal epithelium by a general renewal of developmental activity of the larval cells, without accompanying cell destruction, has been described in some Coleoptera, as in Galerucella by Poyarkoff (1910), Leptinotarsa by Patay (1939), and Sitophilus by Murray and Tiegs (1935). In Tenebrio, accord- ing to Rengel (1897), the remodeling of the stomodaeum and proc- todaeum proceeds from their inner ends, but there are no specific imaginal rings clearly differentiated. The old larval epithelium ap- pears to be absorbed by the advancing newly formed cells. Dobrovsky (1951) follows in great detail the anatomical alterations that take place in the digestive tract of the honey bee during postembryonic development. The stomodaeum and proctodaeum apparently are re- modeled into the adult structure by a new growth of the larval cells. In the wasp, according to Anglas (1901), the cells at the posterior end of the stomodaeum and the anterior end of the proctodaeum begin at the time of pupation an active proliferation extending respectively backward and forward; the advancing new cells absorb the old and thus renew the epithelium. In Trichoptera, Litbben (1907) describes the remodeling of the stomodaeum and proctodaeum by new growth of the larval cells. Russ (1908), however, says that in Anabolia laevis imaginal rings are present, though of little importance. The anterior ring serves only for the lengthening of the stomodaeum and the formation of the NO. Q INSECT METAMORPHOSIS—SNODGRASS 89 stomodaeal valve; the posterior ring is but weakly developed and plays no important role in the reconstruction of the proctodaeum. A part of the rectal region is regenerated from a circumanal zone of proliferation. The regeneration of the stomodaeum and proctodaeum from imagi- nal rings is said by Tiegs (1922) to take place in the hymenopteron Nasoma, but it is particularly in Lepidoptera and Diptera that these proliferation centers have been observed. In the silkworm, according to Verson (1905), the cells of the imaginal rings become active at the change to the pupa, but they are merely centers of enlargement of the stomodaeum and proctodaeum. Newly formed cells are added to the larval cells already present, pushing the latter farther away without replacing them. Otherwise the stomodaeum and proctodaeum, though they undergo great changes in form, are remodeled by renewed ac- tivity of the larval cells. Likewise in Malacosoma, Deegener (1908) says the imaginal rings form only small additions to the larval stomo- daeum and proctodaeum, and there is no degeneration or emission of larval cells. The larval cells remain, forming the pupal epithelium by reconstructive growth. The imaginal rings of Calliphora erythrocephala are very precisely described by Pérez (1910). The anterior ring is a circle of small cells in the alimentary epithelium surrounding the base of the stomo- daeal valve, and therefore on the dividing line between stomodaeum and mesenteron. The posterior ring is a narrow circle of cells in the intestinal wall just behind the bases of the Malpighian tubules. Cellu- lar proliferation from the imaginal rings is said by Pérez to regen- erate most of the stomodaeal and proctodaeal epithelium in Calliphora, but the terminal parts are formed from anterior and posterior centers of ectodermal proliferation. The degenerating replaced larval cells are thrown off into the body cavity. In Calliphora vomitoria, accord- ing to Van Rees (1889), there is only a partial regeneration of the stomodaeum and proctodaeum from imaginal rings; the anterior part of the stomodaeum is remodeled by transformation of the larval cells, and in the proctodaeum the rectum is regenerated from behind for- ward. In Drosophila the stomodaeal epithelium is described by Rob- ertson (1936) as being mostly regenerated from the anterior imagi- nal ring, but regeneration in the pharyngeal region proceeds from the buds of the labium. “As the new epithelium forms, the old larval cells are displaced into the body cavity where they are devoured by phagocytes.” The proctodaeal epithelium of Drosophila is likewise regenerated in its anterior part from the posterior imaginal ring, and go SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 posteriorly by forward proliferation from the ectodermal imaginal disc of the last body segment. From these samples of the reconstruction processes that convert the stomodaeum and the proctodaeum of the larva into the corresponding parts of the adult, we may conclude that in the majority of insects the larval cells of the ectodermal parts of the alimentary canal retain the potentiality of rejuvenation. When released from the inhibition of the juvenile hormone they proceed by renewed division and differ- entiation with the formation of the adult organs. As with the epi- dermis, however, there is a tendency for certain groups of cells to as- sume more and more of the work of reconstruction, and these cells finally take the form of specific regeneration centers, the so-called imaginal rings. It is to be noted that the degenerating larval cells of the stomodaeal and proctodaeal epithelia are thrown out into the body cavity, as are those of the epidermis; the discarded epithelium of the mesenteron, on the other hand, is ejected into the stomach lumen. The mesenteron in its function is more specifically physiological than are the ectodermal parts of the food tract, since it is the seat of digestion and absorption, while the stomodaeum and proctodaeum serve rather in a mechanical way for ingestion, storage, and elimina- tion. The mesenteron, therefore, undergoes a more thorough renova- tion during the pupal metamorphosis, since it must radically alter its functional activities in response to the usual change of diet from larva to adult. Probably in all holometabolous insects there is a com- plete renewal of the mesenteron epithelium, but here again, as with the epidermis, the stomodaeum and the proctodaeum, we find that the method of renewal is not the same in all insects. The larval epithelium of the mesenteron consists typically of two sets of cells. Those of one set are the functional cells concerned with secretion and absorption ; those of the other are small cells next to the basement membrane between the bases of the functional cells, known as replacement cells because by multiplying they form new functional cells to take the place of those that have become exhausted and which in a degenerating condition are thrown out into the lumen of the stomach. In the majority of insects it is these replacement cells that form also the entire epithelium of the pupal mesenteron, but some Coleoptera appear to repeat the embryonic method of forming the stomach, since they regenerate the mesenteron epithelium from cells at the inner end of the stomodaeum. According to Mansour (1934) the mesenteron epithelium is regen- erated from the posterior end of the stomodaeum in representatives of the following coleopterous families: Cucujidae, Chrysomelidae, NO. 9 INSECT METAMORPHOSIS—SNODGRASS OI Curculionidae, and Scolytidae. In Galerucella Poyarkoff (1910) says the larval epithelium of the mesenteron is rejected in toto, including the basement membrane, and that there is then formed a provisional pupal epithelium derived from cells of the posterior face of the stomo- daeal valve. The cells of the new pupal epithelium become differ- entiated into ordinary epithelial cells and small replacement cells. The pupal epithelium, however, is in turn replaced by an imaginal epithe- lium formed by the pupal replacement cells, but the imaginal epi- thelium is thus also derived primarily from the stomodaeum. In Sitophilus (Calandra) oryza Mansour (1927) says that about three days before the pupal moult, the larval epithelium of the mesenteron collapses and degenerates, and together with the replacement cells is thrown off into the lumen. The adult epithelium is then derived in S. oryza and in other rhynchophorous species from the posterior end of the transforming stomodaeum. According to Murray and Tiegs (1935), however, the larval replacement cells of S. oryza are not discharged with the old epithelium, but remain as a layer of scattered cells on the outer surface of the new epithelium and eventually form the mesenteron caeca. The regeneration of the mesenteron of Leptinotarsa decimlineata is described by Patay (1939) as follows. When the larva is ready for transformation, the stomodaeal valve becomes the seat of an in- tense proliferation, forming numerous fusiform cells of an embryonic character. The basement membrane behind the valve soon breaks, and the larval epithelium turns inward and rearward while the newly formed cells from the valve extend over its outer surface. The larval epithelium, including the replacement cells, is then soon rejected into the lumen. The valve cells construct an entire new epithelium, includ- ing islands of replacement cells and a basement membrane. Thus is formed the pupal epithelium, but again at the moult to the imago the pupal epithelium is rejected and the replacement cells reconstruct an imaginal epithelium. The metamorphosis of the mesenteron of Leptinotarsa as given by Patay is thus the same as that in Galerucella as described by Poyarkoff. Statements that the mesenteron is formed from cells of the pos- terior end of the stomodaeum are not to be understood to mean that these cells are ectodermal; as already noted, Henson (1946) has shown that corresponding cells in the embryo represent the anterior end of the blastopore, and therefore properly generate endoderm in- ward, The imaginal ring of the larva, as said by Henson, “is not an imaginal rudiment but a reactivated blastopore.”’ g2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 The formation of the pupal mesenteron epithelium from replace- ment cells of the larva is widespread among the insects, and is too well known to need an extensive review here. According to Mansour (1927) this method of epithelial regeneration is known to occur among Coleoptera in Tenebrionidae, Histeridae, Hydrophilidae, Bos- trychidae, Elateridae, Scarabidae, Buprestidae, Anoboliidae, Dytis- cidae, and Lucanidae. It is the only method of replacement that has been observed in Trichoptera, Lepidoptera, Hymenoptera, and Dip- tera. At the beginning of metamorphosis in these insects, the diges- tive cells of the larval epithelium go into a state of degeneration, while the replacement cells enter a phase of active division, proliferating new cells that spread out under the old epithelium and eventually re- place it. The degenerating larval cells are cast off into the stomach lumen, where they form a disintegrating mass of material known as the “yellow body.” Of particular interest are those cases in which the pupal epithelium of the mesenteron is said to be replaced by a special imaginal epi- thelium. However, without any renewal of the pupal epithelium, the imaginal mesenteron may undergo changes of form and relative size. Deegener (1904) described in Cybister the formation of a sepa- rate epithelium for the pupa differing from that both of the larva and the imago, the function of which he said is to digest the yellow body resulting from the dissolution of the larval epithelium. Both the pupal epithelium and the imaginal epithelium are generated from replace- ment cells. We have already noted that Poyarkoff (1910) reports the formation of a provisional pupal epithelium in Galerucella, which is replaced by an imaginal epithelium generated from the replacement cells of the pupal epithelium. Poyarkoff, however, contends that the pupal epithelium of Galerucella is never functional because in the pupal stage the mesenteron is closed at both ends. In the same way in Leptinotarsa, according to Patay (1939), the pupal epithelium of the mesenteron derived from the inner end of the stomodaeum is re- placed by an imaginal epithelium regenerated from the pupal replace- ment cells. In the coleopteron Acanthoscelides obtectus as described by Bushnell (1936), the pupal epithelium formed from the larval re- placement cells is later cast off into the stomach lumen, leaving only a basal layer of cytoplasm containing the smaller nuclei, from which there is then regenerated the definitive imaginal epithelium. The de- generating material from the larval epithelium, Bushnell says, is prob- ably digested and absorbed by the pupal epithelium, which is then it- self cast off and gives place to the imaginal epithelium. Lastly, we may note that Tiegs (1922) says the pupal epithelium of the chalcid NO. 9 INSECT METAMORPHOSIS—SNODGRASS 93 Nasonia, which is formed from larval replacement cells, proceeds to digest and absorb the detritus from the rejected larval epithelium, after which it degenerates, but from its posterior part is formed the definitive mesenteron of the adult. Deegener (1904) contended that the presence of separate pupal and imaginal epithelia in the mesenteron of many insects is evidence that the pupa represents a former actively feeding stage in the life history of holometabolous insects. Most students of insect metamor- phosis, however, have seen a physiological reason for the formation of a specific pupal mesenteron epithelium in the fact that the pupal stomach must digest the disintegrating tissue of the larval mesenteron thrown into it, in order that this material may be reutilized by the developing imaginal organs. In this case the physiological require- ments of the adult stomach will be very different from those of the pupal stomach, and it is therefore but a physiological necessity that the epithelium should be renewed for the purposes of the adult. Dee- gener (1908) himself notes that there is no formation of a new imagi- nal epithelium in Malacosoma; the pupal epithelium persists and goes over directly into the epithelium of the imaginal mesenteron, but with many changes in its cytological structure. That there is a complete regeneration of the mesenteron epithelium at the moults of the larva, as described by Mobusz (1897) in An- threnus, has not generally been observed, but there is nothing improb- able in Mébusz’s claim, since the replacement cells are active at all times in renewing the depleted functional epithelium. According to Henson (1929) the mesenteron epithelium of Vanessa is renovated at each larval moult by the addition of new cells. It would be of in- terest to know if any such change takes place in the successive forms of heteromorphic larvae. The Malpighian tubules——In some insects the Malpighian tubules go over from the larva to the adult without any essential change, in others their walls are regenerated from replacement cells while the old cells degenerate, in still others the larval tubes completely disap- pear and the imaginal organs grow out in their place as a new set of tubes. It is still an open question, or at least a disputed one, as to whether the Malpighian tubules of insects are ectodermal or endodermal in origin. Most investigators claim that they arise from the inner end of the proctodaeum, others state as positively that they are outgrowths of the posterior part of the mesenteron. In the embryo of the honey bee Nelson (1915) says the rudiments of the tubules are formed prior to the ingrowth of the proctodaeum as invaginations of the ectoderm Q4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 around the point where the proctodaeum is to appear. For a short time, therefore, the tubules “open directly on the external surface of the embryo.” A similar condition, according to Nelson, is known otherwise only in Chalicodoma. If it occurred more widely we might suspect that the Malpighian tubules were originally circumanal glands of the integument, and that they have secondarily been carried inward with the ingrowing proctodaeum. The larval tubes of Hymenoptera that have been studied degenerate and disappear, the imaginal tubes are formed anew. In the honey bee Oertel (1930) says the larval tubes disappear apparently by chemical means, not by phagocytosis. The imaginal tubes are then formed as budlike outgrowths from the extreme anterior end of the proctodaeum. According to Dobrovsky (1951) the ring of buds of the imaginal tubes of the bee appear on the surface of the pylorus a short distance behind the inner fold, or “diaphragm,” that separates the lumen of the larval mesenteron from that of the proctodaeum. These observations agree with those of Anglas (1901) that the larval tubes of the wasp and bee arise from the front end of the procto- daeum, disappear at metamorphosis, and are replaced by imaginal tubes that grow out just behind their bases. In the same manner, ac- cording to Tiegs (1922), are formed the imaginal tubules of the chalcid Nasonia, though there are no larval tubules. The developing imaginal Malpighian tubules of the beetle Leptino- tarsa are described and distinctly illustrated by Patay (1939) as diver- ticula from the anterior end of the proctodaeum. At the beginning of pupation their cells take on an appearance of degeneration, the cyto- plasm becoming vacuolated and the nuclei irregular, but after the moult to the imago they soon again assume the aspect of normal func- tional cells, and without destruction or cell division the persisting larval tubules become the organs of the imago. In some other Coleop- tera, however, the imaginal tubules are said to be regenerated from small replacement cells in the walls of the larval organs. Poyarkoff (1910) describes the imaginal tubules of Galerucella as being formed in this manner, and Murray and Tiegs (1935) say the cells of the larval tubules in Sitophilus (Calandra) degenerate in the pupa, while new imaginal cells are proliferated by active mitosis of the replace- ment cells until they form a new tube. The detritus of the larval cells is not discharged but slowly absorbed. A detailed account of the transformation of the Malpighian tubules from the larva to the adult without dissolution or cell destruction is given by Samson (1908) for the lepidopteron Heterogenea limacodes. During the long prepupal stage of this species the Malpighian tubules NO. 9 INSECT METAMORPHOSIS—-SNODGRASS 95 go into a degenerative state to such an extent that they appear to be on their way to complete dissolution ; at the moult to the pupa, how- ever, reconstructive changes begin that lead to the reformation of the tubules into the organs of the imago. The imaginal tubules retain the form of the larval tubules, but they have undergone an entire change in their histological structure, which, Samson suggests, is correlated with the change of food from the larva to the moth. In the Diptera the Malpighian tubules, so far as observed, undergo no essential change from larva to adult. Pérez (1910) says that the cells of the tubules in Muscidae simply go into a resting condition during the pupal period, and then again resume functional activity in the imago. Robertson (1936) notes simply that the cell structure of the tubules in Drosophila appears to be the same in the larva and the imago. The tubules of Drosophila, Robertson says, open into the digestive tract just in front of the posterior imaginal ring that regen- erates the proctodaeum, from which fact it would appear “that the Malpighian tubules of Drosophila belong to the mesenteron.” Henson (1946) finds likewise in Calliphora that the Malpighian tubules grow out in front of the posterior imaginal ring, so that not only the tubules but also the pyloric region from which they arise are of endodermal origin, and he believes that the same condition prevails in other insects. The fat body.—The so-called fat body of the insect is a physiologi- cal tissue; the changes its cells undergo from larva to imago are merely the accompaniments or results of functional activities and are not of the nature of a true metamorphosis. In the larva the fat cells elaborate and store nutritive materials in the form of fat, albumi- noids, and glycogen, which are utilized mostly in the pupal reconstruc- tion, but may be carried over into the adult. In some insects there is little or no destruction of the fat cells during metamorphosis, in others most of the cells disintegrate in the pupa to liberate their stored products, while a few are carried over intact to generate the fat body of the adult. Insects such as most Coleoptera in which the pupal trans- formation is less intense, and which feed amply in the adult stage, have less need of larval food reserves, and show the least change in the larval fat cells during metamorphosis. On the other hand, with insects in which there is an extensive breakdown of larval tissues and an almost complete reconstruction of adult tissues in the pupa, the food material stored in the larval fat cells is of vital importance for the reconstruction of new imaginal tissues. It is in such insects that the fat cells most abundantly give up their contents to the pupal blood, and perish in so doing, leaving only a few to go over into the adult to form the imaginal fat body. 96 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 In the Muscidae, it is said by Pérez (1910), the larval fat cells dis- integrate completely in the pupa and their remains are devoured by phagocytes. The imaginal fat body, according to Pérez, is then re- developed from mesenchymatous cells on the inner surface of the epi- dermis, the abdominal fat tissue being derived from mesenchyme on the inner surfaces of the imaginal discs of the epidermis. If the imaginal fat body is renewed in this manner in the higher Diptera, its formation from mesenchyme is paralleled by the renewal of the muscles from free myoblasts in the same insects. The oenocytes.—The oenocytes are specialized ectodermal cells de- veloped from the epidermis in the neighborhood of the spiracles, mostly in the abdomen. In some insects the oenocytes remain in the epidermis, but usually they are liberated into the body cavity, where they occur either in groups connected with the spiracular tracheae, or freely scattered in association with the fat cells. Most students of insect metamorphosis report that the oenocytes are renewed at the pupal transformation, and Wigglesworth (1933) says there is in the hemipteron Rhodnius a new generation of oenocytes formed at each nymphal moult, though some of the old oenocytes persist. Accord- ing to Albro (1930) the larval oenocytes of the beetle Galeruclla nymphaeae persist very definitely up to the pupal period, but then they undergo degeneration and histolysis. The smaller imaginal oenocytes appear later newly proliferated from the epidermis. In Sitophilus (Calandra) the larval oenocytes are said by Murray and Tiegs (1935) to begin a slow distintegration in the prepupal stage, some being at- tacked by leucocytes, but the majority later disappear without phago- cytosis. The imaginal oenocytes are independently developed from the epidermis of the abdomen close to the spiracles, but in the imago they are mostly dispersed among the cells of the fat body. No budding of imaginal oenocytes from larval oenocytes was observed by Mur- ray and Tiegs, such as described by some earlier writers. In Leptino- tarsa, Patay (1939) observes that the imaginal oenocytes scatter in the body cavity by amoeboid movements. The function of the oenocytes is still not exactly known, though the cells are now thought to be secretory organs of some kind. It has com- monly been observed that the appearance of secretional activity in the cells is greatest at the times of moulting, and Albro (1930) expressed a common opinion in her statement that secretion by the oenocytes “is in some way, directly or indirectly, correlated with the phenomenon of moulting seems highly probable.” Wigglesworth (1933), however, finds that the oenocytes of Rhodnius show their greatest activity after the new epidermis is complete. He concludes, therefore, that the oeno- NO. 9 INSECT METAMORPHOSIS—SNODGRASS 97 cytes are concerned with the formation of the new cuticle, “that they synthesize, and secrete into the blood, materials which go to form a part of the cuticle.” This conclusion receives support also from the fact that the oenocytes are specialized epidermal cells. For a good, well-documented review of the present status of the oenocyte ques- tion, see Richards (1951). The tracheal system.—In most holometabolous insects the tracheal system of the larva is carried over to the adult with little change other than the development of new branches to accommodate the particular needs of the imago, and the elimination of tracheae needed only by the larva. As with other parts of the ectoderm, however, more com- plex reconstructive processes take place in the tracheal tubes of some insects, involving a dissolution of the larval epithelium and the regen- eration of a new imaginal epithelium. According to Anglas (1901) the tracheal system of the bee undergoes no true metamorphosis, the only change being one of growth and extension by proliferation from the ends of branches, and the enlargement of certain tubes to form the air sacs of the adult. In the curculionid beetle Sitophilus (Calandra), Murray and Tiegs (1935) say that the tracheal system of the adult differs from that of the larva principally in the elaboration of the thoracic tracheae. The larval tracheae are directly converted into the adult tracheae, accompanied by cell division in the epithelium, but only rarely is there any disintegration of the cells. Even terminal branches within the metamorphosing larval muscles remain intact and become reassociated with the newly forming imaginal fibers. On the other hand, in the chalcid Nasonia, Tiegs (1922) finds that there is an extensive reconstruction of imaginal tracheae from replace- ment cells in the basal parts of the larval spiracle trunks. Partly by disintegration and partly by phagocytosis, he says, the entire larval tracheal system disappears, but regeneration of the imaginal epithe- lium keeps pace with the destruction of the larval cells, so that there is no discontinuity in the tracheal system itself. Pérez (1910) givesa detailed account of the tracheal metamorphosis in Calliphora erythro- cephala. Though the greater part of the larval system of the fly per- sists into the imago with more or less extensive remodeling, certain parts of it are destined to be totally destroyed by phagocytes, and to be replaced by newly generated tissue. The tracheal regeneration cen- ters, or histoblasts, are groups of small cells distributed through the walls of the larval tubes ; they give rise to new branching trunks, and replace the larval epithelial cells of those parts that have been de- stroyed by phagocytes. The presence of histoblastic centers of re- generation in the tracheal system, as in other parts of the ectoderm, 98 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 thus appears to be a specialized condition developed in only certain groups of insects. The dorsal blood vessel—From the descriptions of most writers on the internal metamorphosis of insects it would appear that the heart and aorta undergo little change from larva to adult during the pupal transformation, and it has been observed in various insects that the heart continues to beat throughout the pupal stage. In the wasp, Anglas (1901) says the dorsal vessel undergoes no metamorphosis except a change of form. According to Murray and Tiegs (1935) the cells of the heart and aorta of Sitophilus increase in size during the larval stage, but they do not divide, and they survive the period of metamorphosis intact ; the alary muscles of the heart go over with little change into the imago. In Leptinotarsa about the only change in the heart described by Patay (1939) is the formation during the pupal stage of the pulsatile vesicle in the mesothorax of the imago. Robert- son (1936) says of Drosophila that “the dorsal vessel of the larva seems to pass over directly into the adult,” and that “the alar muscles either disappear and are re-formed in the late pupa, or they are some- what altered, being much more delicate in the imago than in the prepupa.” In contrast to these accounts, Tiegs (1922) reports that the heart of Nasonia undergoes a profound metamorphosis, beginning at the time of larval defaecation. Just prior to this the cells of the heart and the pericardium undergo a granular degeneration. The imaginal heart is then regenerated mainly from scattered embryonic cells in the heart wall. A new pericardium is formed from a mass of embryonic cells lying below the larval pericardium, from which proliferating cells extend forward, absorbing the elements of the larval pericardium as they grow. Eight hours after defaecation, Tiegs says, the heart tube of Nasonia has been completely regenerated, and below it is the re- generated pericardium. It seems probable that further studies on the heart of other insects during metamorphosis will reveal greater changes than have hereto- fore been reported, unless there is some special reason for the reno- vation of the organ in Nasonia. On the other hand, if reorganization in the structure of the heart is of common occurrence, it is difficult to explain how a regular heartbeat is maintained during the pupal stage. In the larva the heart beats continuously in a forward direction, but it has been shown by Gerould (1924) and other investigators that dur- ing the pupal and adult life in many insects there is a periodic reversal in the direction of the beat. Gerould (1933) records the occurrence of periodic heartbeat reversal in the pupa and imago of representatives NO. 9 INSECT METAMORPHOSIS—SNODGRASS 99 of Coleoptera, Lepidoptera, Hymenoptera, and Diptera. “In general,” he says, “normal reversal occurs independently of the central nervous system and is essentially myogenic.” For a bibliography of the subject, and a description of the structure and action of the heart in the pupa and imago of Bombyx mort, see Gerould (1938). The nervous system.—lIt is well known that changes in the gross structure of the central nervous system commonly take place between the larva and the adult. Ganglia are drawn forward or condensed by a shortening of the connectives in both the thorax and the abdomen, with the result that ganglionic masses on the nerve cords are fewer and individual ganglia are displaced from their proper segments. On the other hand, condensation of ganglia may be present in the larva, as in the higher Diptera, in which all the body ganglia are united in a large thoracic nerve mass closely connected with the brain. The significance of these gross changes in the nervous system is not clear, but concen- tration and anterior displacement of ganglia is always found in the more specialized insects. The internal reorganization of the nervous system during the pupal transformation has been less studied than that of other tissues. Bauer (1904) has shown that a reconstruction of the brain and the develop- ment of the optic lobes of the adult proceeds from neuroblasts in the larval brain, and, though he apparently made no special study of re- organization in the other ganglia, he says that scarcely any other organ system of the insects undergoes such a thorough metamorphosis as does the central nervous system. In their account of the metamorphosis of Sitophilus (Calandra) oryza, Murray and Tiegs (1935) say that “no direct observations have been made on the manner in which the nervous system of an insect like Calandra becomes readjusted during metamorphosis to meet the needs of the highly specialized imaginal musculature,” but they add that “many new motor neurons doubtless develop from neuroblasts.” However, “disintegration of larval cells occurs but rarely, and con- sequently degenerating nerve trunks are never found, as in many other insects.” In contrast to this Tiegs (1922) finds in the chalcid Nasoma that the larval cells of the nerve cord degenerate, while the imaginal neuroblasts begin to divide and multiply, growing at the expense of the larval cells on which they nourish themselves. In the larval brain there is a distinct layer of nonfunctioning neuroblasts outside the cen- tral mass of functional cells. At the time of defaecation by the larva the larval brain cells go into dissolution as do the nerve fibers, while the neuroblasts become active and give rise particularly to the complex 100 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 optic lobes of the compound eyes and to the centers of the imaginal ocelli and antennae. A study of the developing innervation of the pupal legs of Tenebrio molitor has been made by Sorokina-Agafonowa (1924), who describes an elaborate definitive branching of motor and sensory nerves growing out from the main leg nerve of the larva. The sensory branches go to the epidermis and end in bipolar nerve cells. In a later part of the pupal stage these end cells divide each into several cells until there are hundreds of them which become connected with small setae of the cuticle. The author points out that the connection between the nerve cells and the receptor organs thus appears to be secondary and not primary. It is generally said, however, that the sense cell of a setal sense organ is a division product of a cell in the epidermis, and that the sensory axon grows centrally from it (see Wigglesworth, 1953b). A complete analysis of insect metamorphosis certainly should in- clude a study of differences in the neuromuscular mechanisms between larva and adult that form the basis of difference in sensory reactions and instincts. It would seem that in many cases there must take place in the pupa an extensive rearrangement of both sensory and motor nerves and an almost complete reorganization of the neuron associa- tions in the central nervous system to account for the behavioristic differences between the larva and the adult. Since we cannot attribute any degree of intelligence to a larva, the common act of spinning a cocoon must be supposed to depend on some special pattern of struc- ture in the larval nervous system that would be entirely useless to the adult. Van der Kloot and Williams (1953a, 1953b) have made an in- teresting analysis of the role of both external and internal stimuli in the spinning of the cocoon by the Cecropia caterpillar. A good example of a complex larval instinct is seen in the manner by which the caterpillar of the bagworm moth, Thyridopteryx ephe- meraefornus constructs its portable bag. Several hundred tiny larvae may hatch out at the same time from the eggs of a single female moth. After a period of dispersal they all settle down and proceed by identi- cal methods to enclose themselves in conical bags. Each little cater- pillar first with its mandibles cuts out a number of small oval pieces of leaf epidermis (cork or blotting paper will do just as weil), and then strings them together in a band with threads of its silk attached to the leaf at each end (fig. 16 A). This done, instead of crawling beneath the band, the caterpillar turns a complete somersault, going head first over and under the band (B), landing on its back in reversed direction (C). Then, righting itself (D), it cuts out more leaf bits and makes a ventral band (E) continuous with the one over its back. It now has a NO. 9 INSECT METAMORPHOSIS—SNODGRASS IOI complete girdle about its thorax. Next, elevating its abdomen (F) it lengthens the girdle downward until only its head and feet are ex- posed below (G). Finally, when the bag encloses the whole body, the anchoring threads break loose and the now fully clothed young cater- pillar walks away (H_) to take its first meal on the leaf. As the cater- Fic. 16—Construction of a bag by a newly hatched bagworm, Thyridopteryx ephemeraeformis (Haw.). A-H, consecutive acts of an individual larva making its bag from bits of leaf epidermis cut out with its mandibles. I, an older specimen with later additions to the bag, less enlarged. pillar grows it merely enlarges the bag by leafy additions to the lower edge (1). Such instinctive skill and methodical procedure as this of the newly hatched bagworm must depend on the presence of a highly developed mechanism for coordinated sensory and motor chain re- actions in the central nervous system. The muscular system.—In considering the metamorphosis of the muscular system it must first be noted that all the muscles of all holo- metabolous insects do not undergo the same degree of change. Five categories may be distinguished: (1) Larval muscles that go over un- changed into the adult, (2) larval muscles that are reconstructed into 102 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 imaginal muscles, (3) larval muscles that are destroyed and not re- placed, (4) muscles newly formed for the imago replacing larval muscles that have been completely destroyed, (5) newly formed mus- cles not represented in the larva or which are as yet undeveloped in the larval stage. The histolysis and histogenesis of the muscles have been described by many writers for various insects. The accounts are not all in entire agreement as to the details of the processes, but a chief point of dif- ference relates to the part that phagocytes may play in the destruction of the larval muscles, a question which is of no concern to us in the present discussion, and is fully reviewed by Oertel (1930). The most important matter is the apparently well-established fact that in dif- ferent insects the muscles are regenerated in different ways. In the more generalized orders, such as Coleoptera, the histogenesis of a re- organized muscle or of a replacement muscle is said to proceed from small nuclei within the tissue of the larval muscle itself. On the other hand, in the more specialized orders, particularly in the higher Diptera, such muscles are remodeled or replaced by myoblasts originating owt- side the larval muscles, probably generated from mesoderm in the embryo. Muscles of appendages that are undeveloped in the larva are in all cases derived from free myoblasts. The degenerative processes in larval muscles are always pretty much the same. The complete histolysis of a thoracic muscle of Ephestia kiihniella is described as follows by Blaustein (1935). The advent of degeneration appears at the beginning of the prepupal period with the disappearance of cross striation in the muscle fibers. Lymphocytes now enter the muscle through the sarcolemma and penetrate between the fiber bundles, which lose their connections and separate from one another. The sarcolemma is next broken, admitting increasing num- bers of lymphocytes, and is finally ruptured on all sides. The lympho- cytes, however, Blaustein says, probably do not at this time have a phagocytic action on the muscle tissue. At the end of the third day of pupal life the muscle nuclei begin to degenerate in large numbers, and dissolve as the nuclear membranes disappear. The degenerating mus- cle tissue is now attacked by phagocytic lymphocytes that penetrate be- tween the dissociated fibrillae. By the end of the fourth day of the pupa the histolysis of the muscle is complete, and there remains in the place of the muscle only a great number of phagocytes engorged with muscle fragments. Essentially the same process of muscle degeneration has been de- scribed by other writers for other insects. Some earlier writers re- garded the lymphocytes penetrating the muscles as phagocytes, but it NO. 9 INSECT METAMORPHOSIS—SNODGRASS 103 is now generally agreed that phagocytes do not initiate the destruction of the muscles. They devour the products of the muscle disintegration, and the greatly enlarged, engorged phagocytes may become extremely numerous throughout the body cavity of the pupa, as in higher Dip- tera, in which they have been called “spherules of granules,” or “Kornchenkugeln.” The reconstruction of the muscular system was thought by Berlese (1902) to proceed from the nuclei of the larval muscles, which, being set free in small masses of cytoplasm, became myocytes and were car- ried to the places where imaginal muscles were to be formed. More recent writers, however, find that in those insects in which the muscles are reconstructed from intrinsic elements, the larval muscles contain two sets of nuclei. Those of one set are the functional larval nuclei, which are destroyed; those of the other set are converted into myo- cytes, which form the new muscle in place of the degenerated larval muscle. In the beetle Galerucella, for example, Poyarkoff (1910) says that the larval muscles contain large nuclei that multiply by amitosis, and small nuclei that multiply by mitosis. The first are the larval nuclei, and will disappear ; the small nuclei are the regenerative elements of the imaginal muscles. These mitotic nuclei become en- closed in small masses of sarcoplasm to form myocytes, which asso- ciate in long strands that eventually become the fibers of the new or reconstructed imaginal muscle. The regeneration of muscles in Sito- philus (Calandra) is similarly described by Murray and Tiegs (1935). The small nuclei are at first scattered in the sarcoplasm of the larval fibers, but as the muscle degenerates they migrate into the body of the muscle, which becomes crowded with them. Here these nuclei form myocytes, which unite into columns of cells that finally become the imaginal fibers. Likewise the formation of adult muscles that replace degenerating larval muscles is said by Patay (1939) in Leptinotarsa to proceed from small peripheral nuclei within the tissue of the larval muscles. In the honey bee, Terre (1899) very concisely describes two sets of nuclei in the larval muscles; those of one set are large nuclei in the body of the muscle, the others are small nuclei mostly arranged in longitudinal rows at the surfaces of the fibers. After the larva has finished spinning its cocoon, the muscle substance degenerates and is penetrated by the small nuclei, while the large nuclei dissolve and dis- appear. The small nuclei become surrounded by masses of myoplasm and thus become the myocytes that reconstruct the muscle for the imago. On the other hand, in the account of the metamorphosis of the muscles of the honey bee given by Oertel (1930) it would appear that IO4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 the myoblasts invade the muscle from the outside. Oertel does not dis- cuss the genesis of the free myoblasts, but he says “it is commonly be- lieved that the myoblasts are of mesodermal origin.” In the regenerat- ing abdominal muscles he notes that the fibers in some cases are com- pletely covered by myoblasts, and, in connection with the thoracic muscles, that nuclei present in the larva before sealing of the comb cell become incorporated into the new muscles. In the wasp Polistes, according to Pérez (1912), the larval muscles have two sets of nuclei, large larval nuclei in the body of the muscle, and small embryonic nu- clei attached to the outside of the muscles. The muscles undergo a de- generation and reconstruction without being entirely destroyed, but the larval nuclei are mostly eliminated as the imaginal nuclei take their places in the regenerating muscle. In comparing the muscle meta- morphosis of the vespids with that of the muscid flies Pérez says the only difference is that in the muscids the imaginal myoblasts are at first exterior to the muscles, while in the wasps the myoblasts are attached on the muscles they are to reconstruct and later become free in order to proliferate outside the muscle. In the chalcid Nasonia, according to Tiegs (1922), the adult mus- cles are all formed from free mesodermal myoblasts, which are present in the earliest larva. During the larval period the myoblasts are small embryonic cells scattered in the body cavity close to the muscles. As the larval muscles degenerate the neighboring myoblasts become active, multiply by mitosis, penetrate the sarcolemma, and move about in the disintegrating myoplasm by amoeboid movements. Eventually the whole larval fiber, including the sarcolemma, disappears and the invad- ing myocytes take its place, becoming arranged in rows that finally form the new imaginal fibers. The description by Blaustein (1935) of the muscle transformation in the lepidopteron Ephestia kiihniella is not explicit as to the origin of the myoblasts, but this author says that where a prospective muscle is to be formed very small embryonic cells are first laid down. By mitotic division they multiply, and by fusion with one another they form long strands that become the imaginal muscle fibers. The histogenesis of the muscles of the dipteron Psychoda alternata is described by Schmidt (1929), but here again it is not clear whether the myoblasts are intrinsic or extrinsic with relation to the larval mus- cles. The dorsal longitudinal muscles of the metathorax of the larva while undergoing degeneration lose their cross striation and the sar- colemma disappears, the contractile substance and the plasma blend into a homogeneous mass in which are imbedded many small nuclei, which are the myoblast nuclei that will regenerate the imaginal muscles. NO. 9 INSECT METAMORPHOSIS—SNODGRASS 105 In the higher Diptera there appears to be no doubt that the imaginal myoblasts are primitive embryonic cells at first free in the body cavity of the larva. As examples of the process of muscle formation in the higher Diptera we may cite from the paper by Pérez (1910) on the metamorphosis of Muscidae, and from that by Robertson (1936) on Drosophila. Both authors describe the myoblasts of the imaginal muscles as originating outside the larval muscles. According to Pérez the myocytes are mesodermal cells preexisting in the body cavity, more or less in the vicinity of the epidermal histoblasts, but they are not of ectodermal origin. They represent the precocious rudiments of the imaginal musculature in a state of dissociation. These free myo- cytes, Pérez asserts, are the homologues of the small regenerative nuclei in the larval muscles of those insects in which the muscles are re-formed from intrinsic elements. However, he does not suggest how the free myocytes became dissociated from the larval muscles. Robert- son does not discuss the origin of the free myocytes in Drosophila. The adult muscles of Muscidae, according to Pérez, excepting those that are exclusively imaginal, are mostly muscles that have been re- constructed in the pupa from larval muscles. The larval muscle de- generates into a homogeneous mass, which is then penetrated from the outside by the myoblasts, which reconstruct the larval muscle tissue into a muscle for the adult. The imaginal muscles of the muscids, Pérez says, are thus formed from two different sources, the remains of the larval muscles, and the embryonic myoblasts, the two being combined in different proportions in different muscles. On the other hand, Robertson says, “Practically all muscles of Drosophila are de- stroyed by histolysis and consumed by phagocytes during the prepupal and early pupal instars.” Thoracic muscles, which in Calliphora Pérez believed were remodeled into imaginal muscles, according to Robertson simply undergo a long-delayed histolysis. Myocytes of the longitudinal thoracic muscles appear in the dorsal part of the pupa of Drosophila as early as the fifth hour of the pupal period. They surround the persisting larval muscles and increase greatly in numbers. The larval muscles degenerate completely and disappear, leaving in their place the myocytes, which spread out in the position of the future imaginal muscles. Differentiation then proceeds anteriorly and pos- teriorly from the central mass of myocytes until a new muscle is fully formed. Muscles newly generated in the pupa, having no representatives in the larval musculature, are for the most part the muscles of append- ages that are undeveloped in the larva, including the mouth parts, the antennae, the legs, and the external reproductive organs. These mus- 106 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 cles necessarily are generated from unorganized groups of myoblasts of mesodermal origin that are adventitious on the inner surfaces of the ectodermal histoblasts of the appendages. If, however, an append- age is functionally developed in the larva, it has its own normal larval muscles, and these muscles will undergo a metamorphosis of the type characteristic of the species. In the larva of the beetle Thymalus, for example, Breed (1903) says the leg muscles go into a state of degener- ation until they reach a structureless condition, but this condition is of short duration and is followed by a phase of reconstruction. The reason for the metamorphosis of the muscular system is not hard to see; it is the difference between the musculature of the larva and that of the imago. Breed (1903) argued that the larval muscula- ture must undergo a reconstruction because of the specialized condi- tion of the adult musculature in winged insects. The truth, however, is clearly just the reverse. The adult musculature is essentially the same in all insects from Ephemeroptera to Diptera, except that the thoracic musculature is uniquely specialized in Odonata and is simpli- fied in Blattidae, Mantidae, and Isoptera. The musculature of an adult holometabolous insect, therefore, is in general no more special- ized than that of a winged adult ametabolous or hemimetabolous in- sect. It is the musculature of the holometabolous larva that has be- come specialized for purposes of the larva. Its specialization was at first perhaps one of simplification, but with the larval evolution the larval musculature increases in complexity along patterns that have little or no relation to the imaginal musculature because it becomes adapted to the entirely different mechanism of movement in the larva. The more different a larva becomes from the adult of its species, the more specialized its musculature must be, and, therefore, it is in such insects as Lepidoptera, Hymenoptera, and Diptera that the greatest degree of muscle reconstruction occurs between larva and imago. It is evident that the pupal transformation of the muscles is not entirely comparable to the regeneration of any of the other tissues. The formation of imaginal muscles from special nuclei within the larval muscles might be likened to the regeneration of ectodermal parts from histoblasts within the ectoderm, but the construction of muscles from myoblasts scattered in the larval body has no counterpart in the re- generation of other tissues. Furthermore, it is difficult to understand how the free myocytes in one case, as Pérez contends, can be homo- logues of the regenerative nuclei in the other, and it is quite mysterious how mesodermal cells lying idle throughout embryonic and larval life can be assembled in the pupa and induced to form new muscles for NO. 9 INSECT METAMORPHOSIS—-SNODGRASS 107 the imago. Yet there seems to be no doubt that they do this very thing. The essence of holometabolism is the muscle transformation. XII. MUSCLE ATTACHMENTS AND THE NATURE OF THE PUPA The somatic muscles of arthropods for mechanical reasons are necessarily attached on the cuticle of the integument. The attachment is by means of fine fibrils called tonofibrillae, which traverse the epi- dermis from the cuticle and are attached to the muscle fibrillae ; their outer ends in some cases appear to be embedded in the inner part of the endocuticle. The nature of the tonofibrillae and the manner of their formation have been discussed for half a century, and are still not definitely known ; a review of opinion is given by Richards (1951) and need not be repeated here. Probably the best explanation of the tonofibrillae is that they are cuticular filaments formed by the epider- mal cells where a muscle comes into contact with the integument; if their outer ends are embedded in the cuticle we may assume that the inner layer of the endocuticle was laid down subsequent to the forma- tion of the tonofibrillae. The connection with the muscle fibrillae is said to be formed by a splitting of the inner ends of the cuticular fibers, which are thus “spliced” to the muscle fibrillae so that the two become mechanically continuous. It is well known that homologous muscles may have their attach- ments at different places on the body wall in different insects. The shift is generally attributed to “migration” of the muscles in the phylo- genetic history of the insects; but in embryonic development and in metamorphosis the muscles become attached where their ends come in contact with the epidermis. It seems probable, therefore, that the for- mation of tonofibrillae by the epidermis is evoked by the muscle con- tact. A necessary condition for muscle attachments on the cuticle is that the latter must be established when the epidermal cells are physio- logically active and thus able to produce tonofibrillae while the cuticle is in a formative state. Since most of the adult muscles of holome- tabolous insects undergo a prolonged period of reconstruction in the pupa, they do not make their final attachments until the end of the pupal period when the imaginal cuticle is being formed. On the other hand, if a muscle is ready for attachment at an early stage, as in hemimetabolous insects, it can be attached at once on the imaginal cuti- cle at the end of the larval stage. The nature of the pupa has been a subject of much difference of opinion. Perhaps the most common interpretation is that the holo- metabolous pupa represents the last nymphal stage of insects without 108 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 metamorphosis, which would mean either that the pupa is simply a modified last larval instar, or that the juvenile specialization that pro- duced the larva stopped at the penultimate moult, so that the pupa is a reversion to a nymphal stage with incompletely developed external wings. The nymphal theory of the pupa is carried still further by Jeschikov (1929), who contends that the larva is merely a free-living stage of the embryo and that the pupa represents the whole period of ancestral postembryonic development, “sie erscheint als Resultat des Zusammenfliessens aller nymphalen Altersstufen.” The pupa it- self sufficiently refutes this theory; it gives no evidence of being a composite stadium since its external structure once formed remains unchanged. (See also p. 49.) A more reasonable theory concerning the nature of the pupa is that of Poyarkoff (1914), which holds that the pupa is a preliminary imaginal stage that has been separated from the final adult by an extra moult in order to furnish a new cuticle for the attachment of muscles reconstructed or newly formed in the pupa. Furthermore, Poyarkoff adds, the pupa as a preliminary adult serves as a necessary mold for the muscles forming within it, since in the larva these muscles could not attain the size and the points of attachment appropriate for the adult. It is only after the insect has assumed the external imaginal form in the pupal stage that new muscles can be completed, but even then they are still incapable of functioning because of the lack of attachments. They cannot be attached at the beginning of pupation since they are not yet formed, and they are not able to attach on the pupal cuticle after the latter is hardened. Hence a new moult is necessary to furnish the only condition in which tonofibrillae can be formed for anchoring the muscles on the cuticle. Hinton (1948) strongly advocates the views of Poyarkoff concerning the nature of the holometabolous pupa. If the larval muscles had not departed from the plan of the adult musculature, the larva might go over di- rectly into the adult. The pupal moult is the solution on the part of the insect to the problem of attaching new or reconstructed muscles. The only evidence against this interpretation of the pupa that might arise would be the discovery in some insect with a pupal stage that no new muscle attachments are formed. At present no such condition is known. There can be no question that in its general form and structure the pupa is an unfinished adult. The likeness to the adult is strikingly seen in the relatively generalized raphidian pupa (fig. 17 B), which has distinctly imaginal characters in the shape of the head, the long, slender legs, the subsegmented tarsi, and the large, paired movable NO. 9 INSECT METAMORPHOSIS—SNODGRASS 109 claws on each foot (D). When this pupa is ready to transform it leaves the winter nest of the larva and crawls to a suitable place on the bark of twigs of the tree, to which it tightly clings with its claws TS; L ‘< | i Fic. 17.—Larva, pupa, and adult of a raphidian, and examples of pupal tarsi. A, Agulla adnixa (Hagen), larva. B, same, pupa. C, same, adult female. D, same, pupal tarsus. E, same, tarsus of adult. F, myrmelionid pupal tarsus. G, Corydalus cornutus (L.), pupal tarsus. H, chrysopid pupal tarsus. I, Boreus sp., pupal tarsus. J, Mantispa sp., pupal tarsus. K, Musca domestica (L.), pupal tarsus. (see Stein, 1838, Kastner, 1934). The pupa of the megalopteron Nigronia serricornis (Say) also has paired claws, but in most of the other neuropteroid families the end segment of the pupal leg is merely split into two apical points (F, G), or it bears two small clawlike teeth (H, I) within which the paired claws of the adult are formed. Ina IIo SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 mantispid (J), however, the pupal tarsus ends with a simple expan- sion, and in the higher insect orders, whether the larval leg is one- clawed or two-clawed, the end of the pupal leg (K) is a simple lobe ensheathing the pretarsus of the adult. The clawless pupal leg in the higher orders, therefore, is a result of secondary simplification in an appendage not yet needed for locomotion. That the pupa is a part of the imaginal phase of the insect can be de- duced from other lines of evidence. In the ametabolous or hemime- tabolous insects the juvenile hormone maintains the nymphal or larval status up to the transformation to the imago; in the holometabolous insects the same hormone carries the larval form only up to the pupa. Furthermore, the histoblasts of the larva, or imaginal discs, form di- rectly not the organs of the adult but those of the pupa. The dividing line that separates the holometabolous pupa from the larva, therefore, is the same as that which separates the ametabolous imago from the nymph. The holometabolous pupa and adult thus equate as a unit \ith the ametabolous imago. Williams (1952) has shown that the same hormone system, namely, that of the brain and the thoracic glands, controls both pupation of the larva and the adult development of the pupa. Finally, when we consider that all the internal organs of the pupa are the adult organs in a state of being completed, the pupa can hardly be regarded as anything else than a preliminary adult. At the last larval moult, as Poyarkoff has said, the insect changes into an imago, but the state of its internal organs does not permit it to be- come at once an adult. The occurrence of a moult in the imaginal stage, as Hinton (1948) points out, is not limited to the holometabolous insects; it regularly takes place in most Ephemeroptera, while in the apterygote insects and the other arthropods moulting is usual throughout life. Hinton suggests, therefore, that the pupa is equivalent to the ephemeropterid subimago. However, it would hardly seem that there can be any real relation between the imaginal moult of the mayfly and the moult of the pupa in the very distantly related holometabolous insects. More prob- ably the pupal moult was a secondary, independently developed moult in the ancestors of the present holometabolous insects, rather than a “throwback” to a time when adult moulting was a regular event. It has been shown by Burks (1953) that the subimagines of Ephemer- optera are sexually mature; their sperm and eggs mixed in normal saline solution produce fertilized eggs, from which larvae may be hatched. 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WHITTINGTON ‘ : Museum of Comparative Zoology Harvard University Mel HONOR o/ ain NGTOW ie (Pustication 4146) Ri CITY OF WASHINGTON PUBLISHED BY THE SMITHSONIAN INSTITUTION APRIL 22, 1954 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOLUME 122, NUMBER 10 Charles D. and flary Waux CHalcott Research Fund wo SICICIF IED ea BONIFEROUS TRILOBITES FROM WEST TEXAS (Wir 3 PratEs) BY HARRY B. WHITTINGTON Museum of Comparative Zoology Harvard University soe ose) APRONS iss INGT TON (Pustication 4146) CITY OF WASHINGTON PUBLISHED BY THE SMITHSONIAN INSTITUTION APRIL 22, 1954 The Lord Baltimore Dress BALTIMORE, MD., U. S. Ac Charles BD. and Mary Waux Walcott Research Fund TWO SILICIFIED CARBONIFEROUS TRILOBITES FROM WEST.TEXAS By HARRY B. WHITTINGTON Museum of Comparative Zoology Harvard University (With THREE PLaTEs) The specimens of silicified trilobites described in the following pages were collected and prepared by Dr. Arthur L. Bowsher, of the United States National Museum (hereafter abbreviated as U.S.N.M.). Iam indebted to Dr. Bowsher for suggesting that I study this material and to Dr. G. Arthur Cooper for permitting the loan of it to me. All the specimens are in the National Museum collections and are from the following localities : U.S.N.M. locality 3070.—Helms formation, El Paso quadrangle, Hueco Mountains, Tex., 24 miles west of Powwow Tanks, latitude approximately 31°50'17” N., longitude 106°04’40” W. This locality is stop 13 (p. 40), West Texas Geological Society Guidebook, Field Trip No. 5, November 1949, and stop 1 on the map accompany- ing West Texas Geological Society Field Trip of May-June 1946. No. 3070-2 is from a limestone thought to be the same as bed 9, sec- tion “C” of 1946 Field Trip Guidebook, and No. 3070-4 is from a limestone thought to be the same as bed 11 of the same section. U.S.N.M. locality 3069.—Helms formation, El Paso quadrangle, Hueco Mountains, Tex., 1.1 miles west of Powwow Tanks, latitude approximately 31°50'17” N., longitude 106°03'38”W. No. 3069-2 is from about 10 feet above the base of the Helms in the saddle, from an oolitic limestone lens, and approximately equivalent to the horizon of No. 3070-2. No. 3069-4 is from about 25-30 feet above the base of the Helms in the saddle, from an oolitic limestone with Archimedes, and approximately equivalent to the horizon of No. 3070-4. The numbers of these localities are used in subsequent references to the specimens. The Helms formation in west Texas and adjacent New Mexico has been described briefly by Laudon and Bowsher (1949, pp. 19-20, 31-34), and the term is used here in the restricted SMITHSONIAN MISCELLANEOUS COLLECTIONS, VOL. 122, NO. 10 2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 sense of these authors. The Helms formation is stated by Laudon and Bowsher to be of Chester (Upper Mississippian) age, and it is of interest that the commonest trilobite in the formation, described here as Paladin (Paladin) helmsensis, new species, is very much like the type species of the genus from the Morrow Series (Lower Penn- sylvanian) of Oklahoma. The silicified specimens show the morphology of the exoskeleton in unusual detail and perfection; hence in the next section significant features of morphology and development are described and discussed, and these comments are not repeated in the ensuing detailed descrip- tions. The terminology employed follows that of previous papers (Whittington, 1950, p. 533), except that I have used pleural region of the pygidium rather than pleural lobes or side lobes of Warburg (1925), and interpleural grooves rather than furrows. The additional terms used in describing the articulation of the thorax, and the hypo- stome, are explained on plates 2 and 3. In order to avoid ambiguity in the terms “length” and “breadth” in descriptions, I have used (in the abbreviated form indicated in paren- theses) sagittal (sag.) to describe a measurement in the median line; exsagittal (exs.), parallel to, but outside of, the median line; and transverse (tr.), at right angles to the median line. MORPHOLOGY AND DEVELOPMENT OF THE SILICIFIED SPECIES An unusual feature of the silicified exoskeletons is the relatively great thickness, as compared, for example, to those of silicified Ordo- vician trilobites. I consider the thickness to be original and not a result of the process of silicification. Plate 2, figures 5 and 6, and plate 3, figures 3, 5, and 6, show the thickness of the exoskeleton at the suture lines and along selected sections. The doublure of both py- gidium and cephalon is thicker than the immediately overlying dorsal exoskeleton (pl. 3, figs. 3, 5), nowhere more so than at, and adjacent to, the rostrum. The inner part of the thoracic pleurae is also thick, at a maximum at the posterior edge, the inner surface flat and sloping forward to the much thinner anterior edge. The thickness is such that there is no ridge on the inner surface corresponding to the pleural furrows on the outer surface (pl. 3, figs. 10, 13). Four pairs of glabellar furrows have been observed in some Car- boniferous trilobites (e.g., Stubblefield, 1948, p. 99; R. and E. Richter, 1951, pl. 5). On the inner surface of the exoskeleton (pl. 3, fig. 2) these furrows form inwardly projecting platforms with a well-defined edge (cf. R. and E. Richter, 1951,.p. 225). These are areas of muscle NO. IO TRILOBITES FROM WEST TEXAS—WHITTINGTON 3 attachment, as is also the thickened and projecting outer one-third of the occipital furrow. On the outer surface (pl. 3, fig. 1) only the first (basal) furrow appears as a depression, the second, third, and fourth furrows as smooth areas, in larger specimens appearing as con- spicuous dark patches, dark perhaps because the exoskeleton is thicker here. The articulating furrows of the thoracic axis are slightly thick- ened at the extremity, and presumably are areas of muscle attachment. On the pygidial axis (pl. 3, fig. 5), however, the outer parts of the ring furrows become shallower, and the ovate areas between them, ap- pearing darker in some specimens, are areas of muscle attachment. The eye surface (pl. 3, figs. 4, 6) is externally almost smooth, the facets faintly convex. On the inner surface each circular facet is strongly convex, and the facets are close-spaced and arranged in verti- cal and diagonal rows. The course of the cephalic sutures is revealed in detail (pl. 2, figs. 1, 5, 6; text fig. 1), and I am not aware of any previous descriptions of the rostrum of a Carboniferous trilobite. The edge of the exoskeleton at the sutures is thick and flat, and the hypo- stome fits against both the posterior edge of the rostrum and the ad- jacent inner edge of the doublure. The wing process (at the tip of the large anterior wing) evidently rested in the conspicuous circular pit in the anterior boss on the inner surface of the cranidium (pl. 3, fig. 17). Thus the hypostome was attached to the rest of the cephalon in the same manner as in calymenids, cheirurids, and other trilobites. Articulation between the segments of the thorax and the cephalon and pygidium is effected by a series of devices (see pl. 3, figs. 7-13, I5, 16, and compare Whittington and Evitt, 1954, pp. 21-24). The ring process is a large boss situated at the outer, posterior edge of the axial ring, and fits into a ring socket at the anterior, outer edge. Above the ring socket, in line with the axial furrow, is a tiny, round axial process, which fits into the axial socket in the posterior edge of the segment at the base of the ring process. A narrow (exs.) strip along the anterior edge of the inner part of the pleura is defined by a shallow furrow, and the leading edge is thin and bluntly rounded. It fits into a groove in the thick posterior edge of the inner part of the pleura, this groove being beneath the upper, outer margin of the pleura. This “tongue and groove” articulation extends out to the fulcrum, where it dies out, and there are no articulation processes and sockets at the fulcrum. The posterior edge of the cephalon inside the branches of the facial suture, and the anterior margin of the pygidium inside the fulcra, are shaped like the corresponding edges of the thoracic seg- ments. The outer parts of the thoracic pleurae, and the pygidium, are faceted to facilitate overlap in enrollment. In the doublure of each 4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 segment is a broad V-shaped notch (pl. 3, fig. 14), the Panderian opening, and the anterior edge of this notch is raised (inwardly pro- jecting ), and acts to limit the amount of overlap between segments. Only what are probably the later meraspid stages of the develop- ment are known (pls. 1, 2). The cranidium shows a general reduc- tion in convexity with increasing size. The glabella in the smallest specimens is almost parallel-sided, and with increasing size the lateral expansion of the anterior lobe takes place, the posterior part widens between the eye lobes, and the relative convexity of the posterocentral glabellar region, and of the basal glabellar lobes, is reduced. The eye lobe becomes relatively shorter. The pygidium shows a considerable reduction in convexity with increasing size, and the shallow median notch in the posterior margin of small specimens soon disappears. The meraspid development of Ditomopyge was described by Weller (1935), and the smallest cranidium, 1 mm. in length, has the sub- parallel-sided glabella, long (sag.) anterior border and eye lobe seen in Paladin. However, the glabellar lobation is absent, in contrast to the presence of well-marked basal lobes and furrows in Paladin. Small pygidia of Ditomopyge show a median notch in the posterior border (Newell, 1931, pl. 31, fig. 31; Weller, 1935, p. 508) like that seen in Paladin. While the development of the pygidium in the two genera has some features in common, a notable difference is that in Ditomopyge the pleural regions increase in convexity (Weller, 1935, figs. 4c, 5c, 7c, 8c), in contrast to the decrease in Paladin. The meraspid specimens of Paladin do not resemble any geologically older adult Carboniferous trilobite, and Weller (1935, p. 513) like- wise found that the meraspid specimens of Ditomopyge resembled no known geologically older adult trilobite. One may take these observa- tions as further evidence of the untruth of the so-called “law” of re- capitulation, in the strict sense of Haeckel (cf. de Beer, 1951). SYSTEMATIC DESCRIPTIONS Family PROETIDAE (Hawle and Corda, 1847), Salter, 1864 Subfamily PHILLIPSIINAE (Oehlert, 1886), Pribyl, 1946 A characterization of this subfamily has recently been given by Pribyl (1946, pp. 33-34). The present material of Paladin shows that up to four pairs of glabellar furrows may be present. Few illustra- tions have been published of phillipsiinid hypostomes, but those avail- able (e.g., Woodward, 1883-1884; Weber, 1937) suggest that they are similar to each other and like that of Paladin (pl. 1, figs. 29, 30, 35; pl. 2, figs. 21, 26, 27, 32, 33). Characteristic are the large anterior NO. I0 TRILOBITES FROM WEST TEXAS—WHITTINGTON 5 wings, lack of distinct anterior border, narrow lateral, but wider (sag.) posterior, border, and short (sag.), crescentic, inflated posterior lobe of the middle body. This type of hypostome is not like known examples of hypostomes (Pribyl, 1947, figs. 12-15, 17-19) of proetid genera in other subfamilies, and may be typical of the Phillipsiinae. The shape of the rostrum may equally well be characteristic of the subfamily, but little information is available. Genus PALADIN Weller, 1936 Type species —Griffithides morrowensis Mather, 1915, by original designation of Weller, 1936, p. 707. Discussion—The most abundant of the two species of silicified trilobites described below has been compared with the holotype of Paladin morrowensis, and belongs in this genus. The second species differs from the first notably in the greater convexity of the cephalon and pygidium, the shorter anterior cephalic border, and the outline of the glabella, which is less expanded between the eye lobes but more strongly expanded anteriorly. These relatively minor differences ally it with Kaskia chesterensis (Weller, 1936, pp. 708-711, pl. 95, figs. 4a-6), the type of the genus Kaskia Weller, 1936. K. chesterensis has an even shorter (sag.), steeper anterior border. Weller admitted (1936, p. 708) that Paladin and Kaskia were closely similar, and that there were species intermediate between typical species of the two genera. The second silicified species here described is one of these intermediates. In view of these facts, it seems to me preferable to regard Kaskia as a subgenus of Paladin, with P. morrowensis repre- senting the typical subgenus Paladin (Paladin), and this procedure has been followed below. Reed (1942, pp. 653, 660-667, pl. 10, figs. 4-5b, pl. 11, figs. I-5a; 1943, pp. 179-184, pl. 2, figs. 6, 7, pl. 3, figs. 1-8) considered that the forms he referred to his genus Weberides included most of, if not all, the originals of Woodward’s (1883-1884) plate 4, and were similar to the Russian species described by Weber (1933, pp. 33-35, 37-41, pl. 2, figs. 2-11, 17-33, 36-41, text figs. 14-17, 19-21 ; 1937, pp. 74-75, pl. 8, figs. 31-34, 36, 39-44, 48) under the names Griffithides lutugini and varieties and G. transilis and varieties. Weller (1936, pp. 707- 708), however, had previously placed these Russian species and va- rieties in his genera Paladin and Kaskia. Reed recognized this (1943, p. 180) but did not say how Weberides differed from Paladin. It seems that some of the species referred to above may be congeneric, and if so ought to be placed in Paladin. Before it is concluded that 6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 W eberides Reed, 1942, is a synonym of Paladin, however, the diplo- type of Weberides should be reexamined, for Reed (1942, p. 663) admits that he did not see it. The specimen in question (original of M’Coy, 1844, pl. 4, fig. 5) is a pygidium, with a short, blunt spine on the posterior border. The genus Ditomopyge Newell, 1931 (as emended by Weller, 1935) is related to Paladin (Kaskia), as Weller pointed out (1936, p. 711). The inflation of the central region of the glabella in front of the occi- pital ring seen in P. (K.) rarus, new species, could give rise to the preoccipital lobe of Ditomopyge. The free check of P. (K.) rarus, new species, is much more like that of Ditomopyge than that of P. (P.) helmsensis, new species, which lacks the flattened upper surface of the border. Contrary to the opinion of Weller (1936, pp. 713-714), I regard Ameura as related to Paladin. I have examined the holotype of Ameura sangamonensis (Meek and Worthen, 1865) and the gla- bella is only slightly wider between the eye lobes than across the an- terior lobe. The basal glabellar lobes do have independent convexity. The pygidium, of length (sag.) about equal to width, recalls the original of Woodward’s (1883-1884) plate 4, fig. 9, and the elongated appearance is distinctive. The aforementioned four genera, together with Sevillia (Weller, 1935, p. 506, explanation of text fig. 9, nomen nudum; Weller, 1936) and Linguaphillipsia Stubblefield, 1948, probably form a related group ranging from Lower Carboniferous to Lower Permian in age, wide- spread in North America and Eurasia. PALADIN (PALADIN) MORROWENSIS (Mather, 1915) Plate 1, figures 1-6, 9 Holotype-—Walker Museum No. 16174, incomplete cephalon, from Brentwood limestone, Morrow Series, lower Pennsylvanian, Sawney Hollow, head of Indian Creek, Okla., and 33 miles south of Evansville, Ark. Description—The holotype is refigured here, and the following notes are added to supplement Mather’s (1915, pp. 244-246, pl. 16, figs. 13, 13a) original description. Basal glabellar furrow deepest at about the midlength, disappearing before reaching axial furrow. Ad- ditional furrows not represented by depressions in outer surface. An- terior branch of facial suture running at first outward at about 50° to the sagittal line, then on the border, opposite the maximum width of the anterior glabellar lobe, curving to run inward straight to the mar- gin. The angle between the two sections is about 100°. The doublure NO. 10 TRILOBITES FROM WEST TEXAS—-WHITTINGTON 7 of the cephalon is convex and slopes steeply laterally, but is flattened and slopes gently anteriorly. The rostral suture runs close to the outer edge, the connective sutures curve inward, and the hypostomal suture runs in a curve convex forward. The rostrum is thus similar in outline to that of P. (P.) helmsensis, new species. The associated pygidium is also refigured, and the border is gently convex, not concave as stated by Mather (1915, p. 245). PALADIN (PALADIN) HELMSENSIS Whittington, new species Plates 2, 3; text figure 1 Holotype-—U.S.N.M. No. 116513, cranidium, original of plate 2, figures I, 2, 5, 6; locality 3070-2. Paratypes—U.S.N.M. Nos. 116514a-h; free cheek, rostrum, and hypostome from locality 3070-2; two segments from locality 3069-4 ; two segments from locality 3070-4; pygidium from locality 3069-2. Description—Dimensions of holotype in millimeters: Length (sag. ) 7.0, height 2.7; length of glabella (sag.) 6.3, width across anterior lobe 3.9, at third furrows 3.1, of occipital ring 3.9. Length of para- type pygidium (sag.) 6.3, width 7.8, height 2.8. Cephalon subsemicir- cular in outline, gently convex. Glabella gently convex (sag. and tr.), outlined by shallow axial and preglabellar furrows ; narrowing slightly immediately in front of the occipital ring, expanding between the eye lobes, then narrowing again forward to the minimum width opposite the third furrows, and then expanding forward again until width across anterior lobe is the same as, or slightly greater than, that of oc- cipital ring. Latter moderately convex, highest point near posterior margin, from which it slopes down to the shallow, sinuous occipital furrow ; faint median tubercle. Four pairs of glabellar furrows (pl. 3, figs. 1, 2), the first (basal) appearing as shallow depressions, gently curved, directed inward and backward to isolate triangular, gently con- vex basal lobes. The basal furrows are deepest at midlength, becoming poorly defined at the outer extremity, faint at the inner ends as they meet the occipital furrow. The maximum width of the basal lobes is one-third the glabellar width in front of the occipital furrow. Between the basal lobes the central glabellar region is slightly inflated and pos- teriorly slopes steeply. The second and third glabellar furrows are progressively shorter and directed less strongly backward, the fourth short, ovate, directed slightly forward and commencing a short dis- tance inside the axial furrows. Cheeks sloping gently outward and forward, with a broad (tr.) lateral border defined by the slight change in slope at the faint border furrow, the anterior border nar- 8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 rower (sag.). Posterior border defined by a deep border furrow, and with independent convexity. Genal spine broad at base, relatively long. Eye lobe large, length (exs.) more than one-third that of cephalon, situated with the anterior edge about opposite the glabellar midpoint, and close to the axial furrow, the highest point lower than the glabellar midline between the eye lobes. Palpebral lobe without rim, outer part horizontal, inner part sloping down to axial furrow. Eye surface (pl. 3, figs. 4, 6) with numerous small, gently convex facets. Anterior branch of suture runs straight outward and forward from the eye lobe onto the border, then curves and runs straight in- ward and forward to reach the anterior margin at a point in line (exs.) with the inner margin of the eye lobe. The posterior branch runs outward and backward to the border furrow, then curves, at first more strongly outward, over the posterior border to reach the margin just inside the base of the genal spine. Doublure laterally of less width (tr.) than the border, gently convex and sloping steeply outward. An- teriorly doublure becomes flattened, horizontal, and narrower (sag.). The rostral suture runs along the outer edge of the doublure, the con- nective suture in a curve convex outward. The anterior and posterior margins of the rostrum are thus forwardly curved, the lateral margins outwardly so. The rostrum (pl. 2, figs. 40-42) is also thickest along a line midway between the anterior and posterior margins, so that while the outer surface is flat, the inner is convex. The doublure of the free cheek adjacent to the rostrum shows a corresponding thicken- ing, which fades out laterally. Certain features displayed by the inner surface of the cephalon have been discussed above. Plate 3, figure 2, shows the doublure of the occipital ring. In the inner edge of the doublure of the free cheek (pl. 3, fig. 6) is a shallow notch, in line with the posterior border. I interpret this notch as the Panderian open- ing, and as corresponding with the larger notches in the thoracic pleu- ral doublures. Length of hypostome (pl. 2, figs. 21, 26, 27, 32, 33) (sag.) slightly greater than maximum width across anterior wings. Middle body gently convex longitudinally, more strongly so transversely, not de- fined anteriorly or separated from the anterior wings by a furrow, but laterally and posteriorly outlined by the change in slope at the borders. The crescentic posterior lobe, the tips at about two-thirds the length of the middle body and opposite the lateral shoulders, has a faint independent convexity, most marked at the tips. The anterior sutural edge of the hypostome is thick, extending between the bases of the wings, and fits against both the inner edge of the rostrum and the doublure of the free cheeks (text fig. 1). The anterior wings are NO. I0 TRILOBITES FROM WEST TEXAS—WHITTINGTON 9 broad (exs.) at the base, slope steeply upward, with a small articulat- ing boss at the outer, anterior corner. The lateral borders narrow, gently convex, shoulder well marked, posterior border broader, mar- gin sinuous, posterolateral corners rounded. The interior view shows that the doublure is narrow along the lateral borders, wider along the posterior border, and the furrow dividing the middle body more evi- dent. In lateral view the notch between shoulder and anterior wing is seen, and posterior wings seem not to be developed. Fic. 1.—Paladin (Paladin) helmsensis, new species. Outline reconstruction of the exoskeleton of the cephalon in ventral view, approximately x 7. Number of thoracic segments unknown. Axis moderately convex, each ring subdivided into a short (sag.) anterior part that disappears laterally, and a longer (sag. and exs.) posterior part. The articulating furrow narrow and deep, the half-ring short (sag. and exs.). Inner part of pleura horizontal, outer part bent steeply down, faceted, the facet of the anterior segments (pl. 3, figs. 10-13) abruptly cutting off the narrow (tr.) outer pleural part. The narrowness of these latter enables these segments to fit between and under the genal spines of the cephalon. Succeeding segments (pl. 3, figs. 7-9, 15, 16) have the outer pleural parts wider (tr.). Pleural furrow narrow and deep, situated at about half the length (exs.) at the fulcrum, and extending to the inner edge of the facet. The interior view (pl. 3, fig. 10) shows Io SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 the doublure of the axial ring and the low ridge, the area of muscle attachment, formed by the outer part of the articulating furrow. The devices which facilitate articulation between the segments have been described above. In the doublure of the outer pleural part (pl. 3, fig. 14) is the broad notch of the Panderian opening. The doublure in front of, and outside, this notch is gently convex. Pygidium moderately convex, axis moderately convex and gently tapering. In largest specimens 17 ring furrows, the inner part straight, deep, the outer shallow, turning slightly back. Inner, anterior part of pleural region horizontal, outer part gently convex, steeply sloping, border distinctly separated by change in convexity, and sloping out- ward. Ten deep pleural furrows in largest specimens, progressively more strongly backwardly directed, ending at inner edge of border. Interpleural grooves faint, sometimes absent, sometimes first five visi- ble, not extending on to border. Doublure of same width as border, inner part bent steeply up. External surface of glabella and palpebral lobes with shallow, ir- regular pits (pl. 3, fig. 1), largest near the median line. Small tubercles occur along the posterior edge of the occipital and axial rings. Raised lines, parallel to each other and the margin, on the outer part of the cephalic and pygidial borders and the outer surface of the doublures. Hypostome with similar lines on the middle body and borders, and tiny, shallow, scattered pits on the middle body. Discussion.—Comparison of the cephalon of Paladin (Paladin) morrowensis with the type of P. (P.) helmsensis shows that the latter differs from the former principally in characters of the glabella. That of P. (P.) helmsensis is less inflated (as seen in longitudinal profile), has the basal glabellar lobes and posterior part of the central glabellar region less inflated, and has the anterior lobe less expanded trans- versely, though between the eye lobes the glabella of P. (P.) helmsen- sis is more markedly expanded than that of P. (P.) morrowensis. The external surface of the glabella and palpebral lobes is tuberculate in P. (P.) morrowensis, pitted in P. (P.) helmsensis. The lateral ce- phalic border of P. (P.) morrowensis slopes more steeply than that of the Texas species. The pygidia of the two species (pl. 1, figs. 4-6; pl. 2, figs. 9, 10, 14, 15) are similar, that of P. (P.) helmsensis being distinguished by the axis showing more rings and being more inflated posteriorly, and by the border being relatively broader (sag.) pos- teriorly. The axial rings of P. (P.) morrowensis are apparently with- out the row of tubercles on the posterior margin. Evidently P. (P.) helmsensis and P. (P.) morrowensis are closely related species, though they differ considerably in age. NO. 10 TRILOBITES FROM WEST TEXAS—-WHITTINGTON II DEVELOPMENT OF Paladin (Paladin) helmsensis, NEW SPECIES Cranidium.—Length of smallest cranidium (pl. 2, figs. 34-36) (sag.) 1.5 mm., glabella narrowest between the anterior end of the eye lobes, but since it lacks the anterior and posterior expansions of larger forms it appears almost parallel-sided. Basal glabellar furrows deep and broad, so that the basal lobes are prominent, and the posterior part of the central glabellar region is quite strongly inflated. The sec- ond and third glabellar furrows are ill-defined patches on the exo- skeleton. Length of anterior border of the cranidium (sag.) about one- eighth that of the glabella. Length of palpebral lobes (exs.) more than one-third that of cranidium. In cranidia of increasing size that part of the glabella in front of the third furrow becomes relatively wider (compare figs. I and 34, pl. 2). The palpebral lobes become relatively smaller, the length (exs.) being reduced to less than one-third that of the cranidium. The basal glabellar furrows become shallower, and the convexity of the basal lobes and posterior part of the central glabellar region is reduced. Small cranidia with close-spaced tubercles on the glabella and palpebral lobes, the tubercles on the frontomedian glabel- lar lobe close-spaced and arranged in lines subparallel to the anterior margin. With increasing size of the cranidium these tubercles become less prominent, and in the largest cranidia only the reticulate pattern of pits remains. The smallest hypostome known (pl. 2, figs. 39, 44) is little different from the largest—the shoulders are rather more prominent, and the tips of the crescentic posterior lobe of the middle body are more strongly inflated. The smallest pygidium known (pl. 2, figs. 37, 38, 43) is 1.6 mm. in length (sag.), 2.2 mm. in width. Axis of I5 rings. Pleural region convex, inner, anterior part horizontal, outer part steeply sloping, the border sloping outward but less steeply. Eleven pleural furrows visible, terminating at the inner margin of the border. First three interpleural grooves shallow, situated close to the succeed- ing pleural furrows, and extending on to the inner part of the border. Border broad (sag.) posterolaterally, narrow (tr.) anterolaterally, with a shallow median notch in the posterior margin. With increasing size the pygidium maintains about the same ratio between length and width, and the original of plate 2, figures 30, 31, is 2.2 mm. in length (sag.), 3.3 mm. in width. The convexity of the pleural regions is markedly reduced, the notch in the posterior margin disappears and the difference in the width of the border laterally and posteriorly is reduced. Ina pygidium (sag.) 3.2 mm. long only the first interpleural groove is visible. The tubercles on the median part of the axial rings are visible in this and larger specimens. I2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 PALADIN (KASKIA) RARUS Whittington, new species Plate 1, figures 7, 8, 10-35 Holotype-——U.S.N.M. No. 116511, cranidium, original of plate 1, figure 7, 8, 10, 11, locality 3070-4. Paratypes—U.S.N.M. Nos. 116512a-c, free cheek and pygidium from locality 3070-2, hypostome from locality 3069-4. Description.—Length of holotype cranidium 5.6 mm., height 3.2 mm. ; length (sag.) of glabella 5.1 mm., width across anterior lobe 3.6 mm., between anterior ends of palpebral lobes 2.9 mm., of occipital ring 3.2 mm. The cephalon of this species is similar to that of Paladin (Paladin) helmsensis, new species, but is distinguished by (1) the greater con- vexity ; (2) the glabella being slightly expanded between the eye lobes, but more strongly expanded across the anterior lobe; (3) the sharper angle in the course of the anterior branch of the facial suture on the border (compare the antero-lateral margins of the cranidia in pl. 1, fig. 7, and pl. 2, fig. 1) ; (4) the relatively shorter (sag. and exs.) an- terior border ; (5) the much greater change in slope at the border fur- row of the free cheek, resulting from the inner part of the border being flattened. Additional ways in which the cephalon of P. (K.) rarus differs from that of P. (P.) helmsensis are: (6) the basal gla- bellar furrows are deeper, the basal lobes more inflated; (7) the pal- pebral lobes are narrower (tr.) ; (8) the middle body of the hypo- stome is more convex, with deeper middle furrows, and tiny maculae are present. There is a sharper angle in the anterior margin between where the hypostome fits against the rostrum and the doublure of the free cheek, the shoulders are more prominent, and the posterior bor- der has the three blunt spines; (9) the external surface of the gla- bella and palpebral lobes is tuberculate rather than pitted. Rostrum and thorax unknown. Length of paratype pygidium (sag.) 5.0 mm., width 6.9 mm., height 3.0 mm. This pygidium is distinguished from that of P. (P.) helmsensis by the greater convexity and consequent height. Both the axis and the pleural regions inside the border are more convex in P. (K.) rarus, and the border slopes more steeply outward. The number of axial rings and pleural furrows is the same in the two species, but the ribs between the furrows in P. (K.) rarus are much more convex. Discussion.—Paladin (Kaskia) rarus is distinguished from the type species P. (K.) chesterensis (Weller, 1936, pp. 708-711, pl. 95, figs. 4a-6), also of Chester age, by the less steep slope of the anterior part of the glabella and the longer (sag.) projecting anterior border (com- NO. IO TRILOBITES FROM WEST TEXAS—WHITTINGTON 13 pare pl. 1, fig. 10, with Weller, 1936, pl. 95, fig. 4c). The pleural regions of the pygidium of the Texas species appear to be more convex than those of P. (K.) chesterensis. Four pairs of glabellar furrows are present in P. (K.) rarus, but only three are described as present in P. (K.) chesterensis. Weller (1936, pp. 708-710) pointed out that forms intermediate between the type species of Paladin (Paladin) and Paladin (Kaskia) occur. In the outline and convexity of the glabella, P. (K.) rarus is more like P. (P.) morrowensis than is P. (P.) helmsensis, a further illustration of the close relationship between these species. DEVELOPMENT OF Paladin (Kaskia) rarus, NEW SPECIES The smallest cranidium (pl. 1, figs. 23, 24) is 3.2 mm. in length (sag.). Compared with the largest cranidium it is more convex as a whole, as well as considering the frontomedian and basal glabellar lobes separately ; the glabella is less expanded anteriorly, and the pal- pebral lobes are longer. The development thus parallels that of Paladin (Paladin) helmsensis, with an expansion of the glabella anteriorly, a general reduction in convexity, and decrease in size of the palpebral lobes. The smallest pygidium (pl. 1, figs. 26-28) is 1.7 mm. in length (sag.), strongly convex, the outer parts of the pleural regions over- hanging the border. There are 13 or 14 axial rings, 10 pleural furrows, no interpleural grooves. There is no median notch in the posterior margin of the border. The chief change with increasing size of the pygidium is the reduction in convexity, so that the outer parts of the pleural regions slope steeply but do not overhang the border. REFERENCES DE BEER, G. R. 1951. Embryos and ancestors. Rev. ed. Oxford. Laupon, L. R., and Bowsuer, A. L. 1949. Mississippian formations of southwestern New Mexico, Bull. Geol. Soc. Amer., vol. 60, pp. 1-87, 44 figs. Marue_r, K. F. 1915. The fauna of the Morrow group of Arkansas and Oklahoma. Bull. Sci. Lab. Denison Univ., vol. 18, pp. 59-284, 16 pls., 5 figs. M’Coy, F. 1844. A synopsis of the characters of the Carboniferous limestone fossils of Ireland. viii+207 pp., 29 pls. Dublin. NEwELL, N. D. 1931. New Schizophoriidae and a trilobite from the Kansas Pennsylvanian. Journ. Paleont., vol. 5, pp. 260-269, 1 pl. I4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I22 PrRisyL, A. 1946. Notes on the recognition of the Bohemian Proetidae (Trilobitae). Bull. Int. Acad. Tchéque Sci., 46th year, No. 10, pp. 1-41, 4 pls. I fig. 1947. Aulacopleura and the Otarionidae. Journ. Paleont., vol. 21, pp. 537- 545, I pl., 19 figs. IREED, oH ok. |G: 1942. Some new Carboniferous trilobites. Ann. Mag. Nat. Hist., ser. 11, vol. 9, pp. 649-672, 4 pls. 1943. Some Carboniferous trilobites from Scotland. Ann. Mag. Nat. Hist., ser. II, vol. 10, pp. 176-186, 2 pls. RicHTER, R., and RicHTErR, Emma. 1951. Der Beginn des Karbons im Wechsel der Trilobiten. Senckenbergiana, vol. 32, Nos. 1-4, pp. 219-226, 5 pls., 10 figs. STUBBLEFIELD, C. J. 1948. Carboniferous trilobites from Malaya. Appendix to “Malayan Lower Carboniferous Fossils,” by H. M. Muir-Wood, pp. 1-118, 17 pls., 3 figs. British Museum (Natural History), London. Warsurc, Exsa. 1925. The trilobites of the Leptaena limestone in Dalarne. Bull. Geol. Inst. Uppsala, vol. 17, pp. 1-446, 11 pls. WEBER, V. 1933. Trilobites of the Donetz Basin. Trans. United Geol. and Prosp. Serv. U.S.S.R., fase. 255, pp. 1-95, 3 pls., 33 figs. 1937. Trilobites of the Carboniferous and Permian system of U.S.S.R. Centr. Geol. and Prosp. Inst., Paleont. of U.S.S.R. Mon., vol. 71, fasc. I, pp. I-160, 11 pls., 78 figs. WELLER, J. M. 1935. Adolescent development of Ditomopyge. Journ. Paleont., vol. 9, pp. 503-513, 31 figs. 1936. Carboniferous trilobite genera. Journ. Paleont., vol. 10, pp. 704-714, TE pl WuittincTon, H. B. 1950. Sixteen Ordovician genotype trilobites. Journ. Paleont., vol. 24, pp. 531-565, 8 pls., 9 figs. WuittincTon, H. B., and Evirr, W. R. 1954. Silicified Middle Ordovician trilobites. Geol. Soc. Amer., Mem. 59, 137 pp., 33 pls., 27 figs. (Dated Dec. 18, 1953.) Woopwarp, H. 1883-1884. A monograph of the British Carboniferous trilobites, pp. 1-86, 10 pls., 8 figs. Palaeontographical Society, London. NO. IO TRILOBITES FROM WEST TEXAS—WHITTINGTON EXPLANATION OF PLATES PLATE 1 Figs. 1-6, 9 —Paladin (Paladin) morrowensis (Mather)...............05 I, 2, 3, Dorsal stereograph, left lateral, and anterior views of holo- type, Walker Museum No. 16174, X 3. 4, 5, 6, Dorsal stereograph, posterior, and right lateral view of pygidium, Walker Museum No. 16174, X 3. 9, Ventral view of cephalic doublure of holotype, posi- tion of left (right in picture) edge of rostrum dotted, * 74. Brent- wood limestone, Morrow Series, lower Pennsylvanian, Sawney Hol- low, head of Indian Creek, Okla., and 34 miles south of Evansville., Ark. Fics. 7, 8, 10-35.—Paladin (Kaskia) rarus Whittington, new species....... 7, 8, 10, 11, Dorsal stereograph, interior, right lateral, and anterior views of holotype cranidium, U.S.N.M. No. 116511, locality 3070-4, X 3. 12, 13, 14, Dorsal stereograph, posterior, and left lateral views of paratype pygidium, U.S.N.M. No. 116512a, locality 3070-2, < 3. 15, 18, Anterior view, dorsal stereograph of cranidium and free cheek, locality 3070-2, X 3. 16, 17, Dorsal and posterior views of pygidium, locality 3070-2, X 3. 19, Right lateral view of cranidium, original of figures 15, 18, X 3. 20, 21, 22, Dorsal, posterior, and ven- tral views of pygidium, locality 3070-2, & 3. 23, 24, Dorsal and right lateral views of cranidium, locality 3069-2, X 3. 25, 31, Left lateral and dorsal views of paratype free cheek, U.S.N.M. No. 116512b, X 3. 32, Interior view of same, X I0, locality 3070-2. 26, 27, 28, Dorsal, posterior, and left lateral views of pygidium, locality 3070-2 xX 4. 20, 30, 35, Ventral, interior, and left lateral views of paratype hypostome, U.S.N.M. No. 116512¢, locality 3069-4, X 3. 33, 34, Ven- tral and left lateral views of hypostome, locality 3069-2 *.3. Helms formation, Chester Series, upper Mississippian, Hueco Mountains, west Tex. Locality numbers are explained on page I. PEA 2 Paladin (Paladin) helmsensis Whittington, new species............+0.000 I, 5, 6, Dorsal stereograph, anterior view, anterolateral stereograph of holotype cranidium (U.S.N.M. No. 116513), and paratype free cheek (U.S.N.M. No. 116514a), locality 3070-2, & 3. 2, Left lateral view of holotype cranidium, U.S.N.M. No. 116513, locality 3070-2, X 3. 3, 4, Dorsal and left lateral views of free cheek, locality 3069-4, xX 3. 7, 8, Dorsal and right lateral views of cranidium, locality 3069-4, X 3. 9, 10, 14, 15, Dorsal stereograph, interior, posterior, and right lateral views of paratype pygidium, U.S.N.M. No. 116514b, locality 3069-2, X 3. 11, 12, Dorsal and right lateral views of cra- nidium, locality 3069-4, * 3. 13, 20, Dorsal and posterior views of pygidium, locality 3069-2, * 3. 16, 17, Dorsal and right lateral views of cranidium, locality 3069-4, < 3. 18, 19, Dorsal and pos- terior views of pygidium, locality 3069-4, 3. 21, 26, 27, Right lateral, ventral, and interior views of paratype hypostome, U.S.N.M. No. 116514c, locality 3070-2, X 3. S =shoulder; n= lateral notch. 16 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 Page 22, 23, Dorsal and right lateral views of cranidium, locality 3069-4, X 3. 24, 25, Dorsal and posterior views of pygidium, locality 3069-4, X 3. 28, 29, Dorsal and right lateral views of cranidium, locality 3069-4, X 74. 30, 31, Dorsal and posterior views of pygidium, lo- cality 3069-4, X 3. 32, 33, Ventral and right lateral views of hypo- stome, locality 3069-2, X 3. 34, 35, 36, Dorsal, right lateral, and an- terior views of cranidium, locality 3069-2, * 73. 37, 38, 43, Dorsal, posterior, and right lateral views of pygidium, locality 3069-2, 73. 30, 44, Left lateral and ventral views of hypostome, locality 3069-2, X 3. 40, 41, 42, Exterior, posterior, and interior views of paratype rostrum, U.S.N.M. No. 116514d, locality 3070-2, * 6. 45, Dorsal view of free cheek, locality 3060-4, X 3. Helms formation, Chester Series, upper Mississippian, Hueco Mountains, west Tex. Locality numbers are explained on page I. PLATE: 3 Paladin (Paladin) helmsensis Whittington, new species............e.eeeee 7) I, 2, Exterior and interior views of incomplete cranidium, showing the four pairs of glabellar furrows and the pits in the external sur- face, locality 3070-4, < 6. 3, Anterior view of broken edge of free cheek, showing thickness of exoskeleton, locality 3070-4, < 6. 4, 6, Exterior and interior views of paratype free cheek, U.S.N.M. No. 116514a, showing eye surface and Panderian notch (p), locality 3070-2, X 73%. 5, Interior view of incomplete pygidium, showing muscle scars as dark patches between ring furrows of axis, and thickness of exoskeleton, locality 3070-2, * 6. 7, 8, 9, Posterior, dorsal, and left lateral views of paratype segment, U.S.N.M. No. 116514e, locality 3070-4, X 3. 10, II, 12, Ventral, posterior, and an- terior views of paratype segment, U.S.N.M. No. 116514g, locality 3069-4, X6. rp=ring process; ap=axial process; as = axial socket; g—= groove in posterior edge of inner part of pleura. 13, Dorsal view of same, X 3. 14, Interior view of paratype incomplete segment, U.S.N.M. No. 116514h, locality 3069-4, 74, showing notch in doublure termed Panderian opening. 15, Dorsal view of paratype segment, U.S.N.M., No. 116514f, locality 3070-4, X 6. 16, Left lateral view of same, <3. 17, Interior view of right half of holotype cranidium, U.S.N.M. No. 116513, showing pit in boss formed by anterior pit in external surface, locality 3070-2, X 73. Helms formation, Chester Series, upper Mississippian, Hueco Moun- tains, west Tex. Locality numbers are explained on page I. mht A hates SMITHSONIAN MISCELLANEOUS COLLECTIONS PALADIN (PALADIN) MORROWENSIS AND PALADIN (KASKIA) RARUS (SEE EXPLANATION OF PLATES AT END OF TEXT.) SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122, NO. 10, PL, 2 PALADIN (PALADIN) HELMSENSIS (SEE EXPLANATION OF PLATES AT END OF TEXT.) ITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122, NO. 10, PALADIN (PALADIN) HELMSENSIS EXPLANATION OF PLATES AT END OF T MAPA a) nan PA A A oe FMR SNE Cee mE er OR SMITHSONIAN MISCELLANEOUS COLLECTIONS VOLUME 122, NUMBER 11 A REVISION OF THE SEA-STARS OF THE GENUS: TETHYASTER (Wits 12 PiatEs) BY AILSA M. CLARK British Museum (Natural History) AND AUSTIN H. CLARK Associate in Zoology, U. S. National Museum (PuBLICATION 4147) CITY OF WASHINGTON PUBLISHED BY THE SMITHSONIAN INSTITUTION APRIL 8, 1954 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOLUME 122, NUMBER 11 Pore VISION OF (THE SEA-STARS OF THE GENUS TETHYASTER (Wit 12 PLATES) BY AILSA M. CLARK British Museum (Natural History) AND AUSTIN H. CLARK Associate in Zoology, U. S. National Museum (PUBLICATION 4147) CITY OF WASHINGTON PUBLISHED BY THE SMITHSONIAN INSTITUTION APRIL 8, 1954 The Lord Baltimore Press BALTIMORE, MD., U. & A. A REVISION OF THE SEA-SPARSIO“ DEE GENUS EP EY AS LER By AILSA M. CLARK British Museum (Natural History) AND AUSTIN H. CLARK Associate in Zoology, U. S. National Museum (WitH 12 PLATES) The interrelationships of the sea-stars that we regard as constituting the genus Tethyaster have never been satisfactorily worked out. All the species are rare—at least few specimens have been collected—and no one museum has been able to secure a fully representative series either of the included species or of the growth stages of any single species. The growth stages in this genus are especially important, for the young may present an aspect quite different from that of fully developed individuals, and the adult characters are often late in making their appearance. In the preparation of this revision we have studied all the specimens in the U. S. National Museum, in the British Museum (Natural His- tory), and in the Museum of Comparative Zoology at Cambridge, Mass., for the loan of which we are greatly indebted to our friend Dr. Elisabeth Deichmann. Two of the species (canaliculatus and vestitus) have not previously been figured, the type specimen of another (magnificus) has not been figured, and of one (grandis) only a few details have been illustrated. Of the others, two (subinermis and aulophora) have been illustrated in satisfactory detail, and the last (pacei) has been figured sufficiently for purposes of identification. Thomas Say in 1825 (p. 143) described a very large sea-star from New Jersey under the name of Asterias vestita, as follows: 5. A. vestita. Disk broad, surface reticulated, covered by cylindrical promi- nences, margin articulated; rays depressed. The whole surface is covered by cylindrical prominences, which are placed near each other, truncated at their summits, and each summit crowned by from ten to eighteen small, equal, cylindrical fimbriae; wart-like tubercle [madre- SMITHSONIAN MISCELLANEOUS COLLECTIONS, VOL. 122, NO. 11 2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 porite] large, radiated, very conspicuous; margin articulated; each articulation with about four very much compressed, subquadrate, truncated spines or move- able processes, which are vertically adpressed to the surface of the segment, and are imbricated with respect to each other. Diameter 1 foot 2 inches. The locality was given as Cape May, N. J. Say said that it is “Allied to A. aranciaca Linn., but distinct by many characters, and particu- larly by the form and number of the lateral spines. It is very rare on this coast.”” The type and only known specimen disappeared, and the species has since remained an enigma. Dr. A. Philippi in 1837 (p. 193) briefly described Asterias subiner- mis from a specimen 14 inches in diameter from the coast of Sicily. This well-known but rare species has been recorded from both coasts of the Mediterranean as far east as Rhodes and from the Bay of Bis- cay southward to the Gulf of Guinea. It has never been confused with any other species and has no synonyms, but it has been assigned to various genera—Astropecten (Muller and Troschel, 1842), Archas- ter (Perrier, 1875), Gontopecten (Perrier, 1885), Plutonaster (Te- thyaster) (Sladen, 1889), and Tethyaster (Perrier, 1894), almost all these dispositions being followed by other authors. A detailed account of this species, under the name Plutonaster subinermis, with figures and bibliographic references, was given by Ludwig in 1897 (p. 105). Say’s Asterias vestita was listed, without description, as Astropecten vestitus by Liitken in 1859 (pp. 27, 54). Verrill in 1866 (p. 339) under Astropecten vestitus Litken said “Say’s specimen was from Cape May, collected by Mr. J. Robbins. I am not aware of any other being found.” In 1882 (p. 440) Prof. F. Jeffrey Bell described Archaster magnifi- cus from two specimens with R=207 and 138 mm., and r=50 and 37 mm., which had been presented to the British Museum some years before by J. C. Melliss who had obtained them at St. Helena. W. Percy Sladen in 1889 established, under Plutonaster, the sub- genus Tethyaster (p. 101) in which he placed Philippi’s Asterias sub- inermis and Diiben and Koren’s Astropecten parelii. He also (p. 192) diagnosed the genus Moiraster for the reception of Archaster magni- ficus Bell. In 1895 Verrill (p. 133) listed Astropecten vestitus Liitken and said “B. range, shallow water. Cape May (Say). It is not uncommon farther south.”* In 1899 Verrill (p. 210) proposed the new genus Sideriaster, based upon a new species, S. grandis, from Albatross station 2378. The description was brief, but he figured the actinal side 1 Possibly here confused by Verrill with Astropecten cingulatus Sladen. NOs, Tt SEA-STARS—CLARK AND CLARK 3 of a part of the middle of a ray, an adambulacral plate, and an abactinal paxilla. In 1908 Dr. René Koehler described in detail and figured a small specimen of Motraster magnificus with R = 62 mm. from Pointe Pyramid, Ascension, in 40 fathoms. In 1914 (p. 21) Verrill discussed Sideriaster(?) vestitus (Say). He said that the type of Sideriaster, S. grandis, does not agree suffi- ciently well with vestitus to be identified as the same species, but it seems almost certain that it is congeneric. He added that when more specimens can be obtained it may prove to be the same species. In 1915 (p. 191) Verrill republished his diagnosis of Sideriaster and (p. 192) his description of S. grandis, also republishing the fig- ures of details previously given. He also discussed (pp. 193-195) Sideriaster (?) vestitus (Say) Verrill at considerable length. He noted that “Probably the type is lost. It is probably not an Astro- pecten. In having a large disk, and especially in having four appressed spines in a transverse row on the inferomarginal plates, the Sideriaster grandis V. agrees, perhaps, with Say’s species. But he gives too little, as to other characters, to enable me to say whether they are related.” In 1916 (p. 52) A. H. Clark described in detail, but did not figure, Sideriaster canaliculata from Albatross station 2998, Gulf of Cali- fornia, in 40 fathoms. Dr. Walter K. Fisher in 1911 (p. 417) published a diagnosis of a new genus, Anthosticte, based upon a new species, A. aulophora, described from a single specimen from Albatross station 5420 in the Philippines. In 1919 (p. 140) he republished the diagnosis of Antho- sticte, redescribed and figured A. aulophora, and discussed the rela- tionships of the new genus. Dr. Th. Mortensen in 1925 (b, p. 147) described and figured Anthosticte pacei from South Africa. He wrote that “from the type species A. aulophora, the only species hitherto known of the genus An- thosticte, the present species is easily distinguished through the lower paxillae and the complete lack of pedicellariae.” In 1933 (p. 422) Mortensen.recorded three specimens of Moiraster magnificus that he dredged off Egg Island, St. Helena. In these R = 160-179 mm. He gave various details of the specimens. In 1947 Sefiorita Maria Elena Caso described and figured Moiraster gigas from a very large specimen with R = 205-245 mm. from Santa Rosalia, Baja California, on the western shore of the Gulf of California. In 1950 (p. 302) A. H. Clark recorded under the name of Moiraster magnificus a specimen with R = 168 mm. from off the western coast 4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 of Puerto Rico. This specimen we now consider as representing vestitus. As for the interrelationships of these genera, they were discussed in some detail by Fisher in 1919 (p. 143). He said that Moiraster, Tethyaster, Sideriaster, and Anthosticte agree in having unarmed supermarginals, inferomarginals with a few small enlarged spines, naked madreporite, large actinal interradial areas, and intermediate plates far along the ray, marginal and actinal fascioles, true paxillae, stellate abactinal plates, an astropectinid adambulacral armature, and probably also in having the single papulae uninterrupted all over the dorsal surface. He said that the first two seem to be a little more closely related than either is to the last two, while Sideriaster and Anthosticte are possibly also nearly related. He noted that unfortunately there is but one species in each genus, and it is difficult to ascertain what char- acters are of generic importance. He remarked that, according to the standards used in other larger genera, Anthosticte differs from Tethy- aster chiefly in having very deep marginal fascioles, gonads to the end of the ray, and no midradial series of enlarged paxillae. Anthosticte has taller and more delicate paxillae, but this may not be of generic importance. Its special points of agreement in addition to the char- acters listed are the deposits in the tube feet (not recorded for Moiraster and Sideriaster) and shallow interambulacral fascioles, and an incipient interradial series of actinal intermediate plates, less prominent and regular than in Tethyaster. He said that Anthosticte differs from Sideriaster in having very deep marginal fascioles and no distally enlarged subambulacral spines. Neither the deposits in the tube feet nor the gonads of Sideriaster are described. He considered that the fascioles between the adambulacral plates which he examined in the type specimen of Sideriaster grandis form one of the most striking features of the genus. They are densely lined with small, delicate spinelets, and are therefore similar to marginal fascioles. Such is not the case, he said, in Anthosticte, Tethyaster, or Moiraster. Mortensen in 1933 (p. 424) also discussed these four genera. He wrote that the knowledge now acquired of the characters of Moiraster (from his three specimens from St. Helena) makes it clear that the four genera are even more closely related than Fisher thought them to be—so closely, indeed, that it seems scarcely possible to maintain them all. He said that Tethyaster is well characterized by its mid- radial row of enlarged paxillae, the shallow marginal fascioles, and the low paxillae, so it may justly be maintained as a separate genus. He noted that Fisher’s statement that its gonads do not extend to the NOS DE SEA-STARS—CLARK AND CLARK 5 ends of the rays is a curious mistake, “in flat contradiction to the description given by Ludwig.” As for Anthosticte, he said that it is now seen that the only character by which it differs from Moiraster is the absence of enlarged spines on the ventrolateral plates. In regard to fascioles between the adambulacral plates he said there seems to be a very gradual passage from Anthosticte to Moiraster and Sideriaster. He noted that Sideriaster, which is still imperfectly known, would likewise seem to differ from Moiraster only in lacking enlarged spines on the ventrolateral plates. He said that it is, of course, a matter of taste whether this character, the presence or absence of enlarged spines on the ventrolateral plates, affords sufficient reason for generic dis- tinction. But, he added, this is all the difference there is. In 1950 the question of the identity of a specimen taken by the M.V. Rosaura off the mouth of the Orinoco in 75 meters was raised between the two present authors. Dr. Dilwyn John has provisionally attributed the specimen to Sideriaster, but investigation seemed to show that it also had some affinity with Bell’s Moiraster magnificus from St. Helena. At about the same time the M.V. Oregon dredged 10 specimens of Sideriaster grandis off Corpus Christi, Tex., another was dredged by the yacht Triton off Sombrero Key, Fla., and still another was received by the U. S. National Museum from off the coast of Tamaulipas, Mexico. Furthermore, the Museum acquired a very large sea-star from the coast of North Carolina that agrees com- pletely with the meager description of Say’s Asierias vestita, but is slightly larger. There seems to be no doubt that it represents Say’s long-lost species. . With this additional material available it has seemed advisable to review the status of Tethyaster, Moiraster, Sideriaster, and Antho- sticte. We have personally examined specimens of all the species described in these genera except Anthosticte pacei, which was briefly, though sufficiently, described and figured by Mortensen. We can see no valid reason for not considering all these species congeneric and we therefore unite them all in the genus Tethyaster, of which we regard Moiraster, Sideriaster, and Anthosticte as synonyms. Genus TETHYASTER Sladen Asterias (part) SAy, 1825, p. 143.—Puitprt, 1837, p. 193. Astropecten (part) MULter and TroscHeEL, 1842, p. 74, following authors. Archaster (part) PERRIER, 1875, p. 3690, and following authors. Goniopecten (part) PERRIER, 1885, p. 71. Plutonaster (subgenus Tethyaster) (part) SLADEN, 1889, p. 101 (diagnosis; genotype Asterias subinermis Philippi). 6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 Moiraster SLADEN, 1889, p. 192 (diagnosis; genotype Archaster magnificus Bell). —FISHER, I919, pp. 143, 144 (discussion).—MoRTENSEN, 1933, Pp. 424 (discussion). Tethyaster PERRIER, 1894, p. 322; 1896, p. 50.—KOEHLER, 1896a, pp. 56, 57; 1896b, Pp. 450, 451.—GREGORY, 1900, p. 251.—FISHER, I910, p. 143.— KOEHLER, 1921, P. 53; 1924, p. 190.—RIVERA, 1930, p. 105—MORTENSEN, 1933, D. 424. Plutonaster (part) Lupwic, 1897, p. 105—CUENOT, 1927, p. 295.—NosrRE, 1931, figs. 42, 43. Sideriaster VERRILL, 1890, p. 210 (diagnosis; genotype Sideriaster grandis, sp. nov.) ; I9I4, p. 21; 1915, p. 191.—FISHER, 1919, p. 143.—MORTENSEN, 1933, p. 424. Anthosticte FISHER, I9II, p. 417 (diagnosis; genotype Anthosticte aulophora, sp. nov. ).—MOoRTENSEN, 1933, Pp. 424. Thetyaster NoBrE, 1931, p. 62. Thethyaster Nore, 1931, p. 176. Diagnosis —A genus of Astropectinidae with both series of mar- ginal plates large and conspicuous, equally developed, the superomar- ginals granulated or with numerous short spinelets, the inferomar- ginals with a median row of usually about five enlarged and flattened appressed spines; actinal intermediate areas large with numerous intermediate plates arranged in definite series with an incomplete un- paired median row; the inferomarginals separated from the adambu- lacrals by a series of actinal intermediate plates for most of the ray ; fascioles between the marginals, adambulacrals, and actinal inter- mediate plates; madreporite large and bare; adambulacral armature astropectinid; abactinal plates with paxillae having high columns; gonads extending far along ray. Geographical range.-—From New Jersey south to the mouth of the Orinoco ; Gulf of Mexico; St. Helena and Ascension; Bay of Biscay south to the Gulf of Guinea; Mediterranean east to the Aegean Sea; South Africa; Philippines ; Gulf of California. Bathymetrical range.—From 44 to about 1,400 (?1,425) meters. Remarks.—Presumably the most specialized species of Tethyaster are those with the spines on the inferomarginal and actinal intermedi- ate plates wide, rectangular, and broadly truncated, as these depart most widely from the generalized astropectinid type. Although our knowledge of this genus is admittedly meager, these species appear to be primarily American, ranging from New Jersey to Venezuela (vestitus), occurring at St. Helena and Ascension (magnificus), and found also in the Gulf of California (canaliculatus). This group in its distribution would parallel roughly the genera Encope, Mellita, and Leodia among the echinoids, the Marginatus group of Astropecten, and Asirocaneum in the Gorgonocephalidae. It should be noted that NO. II SEA-STARS—CLARK AND CLARK A the crinoid genus Crinometra so very characteristic of the Caribbean area is also represented at St. Helena. A more generalized type with less strongly modified spines on the inferomarginals, which only very rarely extend on to the actinal inter- mediate plates, is widely distributed, occurring in the Gulf of Mexico (grandis), in the Mediterranean and east Atlantic from the Bay of Biscay to the Gulf of Guinea (subinermis), off South Africa (pacer), and in the Philippines (aulophora). At the same time aulophora is distinguished from the other members of this group by the relatively tall and slender dorsal paxillar columns, such as are found also in vestitus and magnificus. However, this character is probably less fundamental than the shape of the inferomarginal spines. Other differences between the species are shown in the key. KEY TO THE SPECIES OF TETHYASTER (This key is adapted for fully developed specimens with R = 100 mm. or more.) a1, Actinal intermediate plates each with an enlarged, broad, flat- tened, and broadly truncated procumbent spine directed out- ward (if these are undeveloped the inferomarginal spines are broadly truncated) ; enlarged and flattened spines on the in- feromarginals broad, usually approximately rectangular or scoop-shaped with broadly truncated ends, rarely tapering ; R = 200-250 mm, in fully grown individuals. b1, Enlarged spines on actinal intermediate plates fan-shaped or scoop-shaped with divergent sides and broadly truncated ends; spines on the inferomarginals similar (may be tapering in young individuals: pl. 3; fig. 1, c) (Gulf of Galton ies a he ee NOES 5 Mee Ce RS RN Te canaliculatus b2. Enlarged spines on actinal intermediate and inferomarginal plates rectangular, rarely scoop-shaped. ci, Enlarged and flattened spines in fully grown individuals 6-7 mm. long, first appearing when R—=about 70 mm. (plig) (St. Helena and Ascension) 25) ...s.2..025 000. magnificus c?, Enlarged and flattened spines in fully grown individuals reaching only 4 mm., first appearing when R= about 150 mm. (pl. 6; fig. 1, d) (New Jersey south to off the MOET RAVE eae acta © Ga orci c Sasa Sco Sia wae see acpiaee a aise vestitus e”, Actinal intermediate plates without a central enlarged spine (there may be a very few pointed spines in some specimens of grandis) ; enlarged and flattened spines on inferomarginals sharp-pointed. G4. Columns of paxillae slender, high, about 4 times as high as thick; most of paxillae with a pedicellaria of 2-4 valves WE MGpines Reraes soso os alck eo Paes Hose eee bae leaned cmeee aulophora b2. Columns of paxillae stout, low, not over twice as high as thick; no abactinal pedicellariae, so far as known. 8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 cl. Marginals short, 68-85 in number; rays fairly broad, width of rays at base=r; paxillae of median row on rays sometimes larger than others (Bay of Biscay to Gulf of Guinea and most of Mediterranean) ...........eee2eeeee subinermis c?. Marginals longer, up to 65 in number; rays narrow, width at base less than r; paxillae of median row on rays not larger than others. d1, Rays very narrow, R= 4.3 1; first series of actinal in- termediate plates reaching to about outer third of ray, second only in proximal third; intermarginal fascioles deep, extending inward for about two-thirds the proxi- mal and distal sides of marginals (South Africa)........... pacei d?, Rays broader basally, R=3.2 to 3.5 r; first series of actinal intermediate plates reaching to about outer fourth of ray, second to well beyond middle; intermar- ginal fascioles shallow, extending inward for less than one-third the proximal and distal sides of marginals Cols: 15,782). ACGulivok Mexico)! ii nrrss 2. Seem: ote ovis sore grandis TETHYASTER CANALICULATUS (A. H. Clark) Plates 1-4; text figure 1, c Sideriaster canaliculata A. H. CiarK, 1916, p. 52 (description; Albatross station 2908) .—ZIESENHENNE, 1937, p. 212 (notes; Zaca stations 136, D-19; 142, D-3; 146, D-1; 147, D-2; 150, D-9).—Caso, 1947, p. 225 (listed). Moiraster canaliculata Caso, 1947, p. 225 (listed). Motraster gigas CAso, 1947, p. 225, fig. 1, p. 226, fig. 2, p. 227, fig. 3, p. 228, fig. 4, p. 229 (description; Santa Rosalia, Baja California). Diagnosis —Enlarged spines on the inferomarginals and actinal intermediate plates scoop-shaped with divergent and convex sides, broadly truncate, the outer portion commonly with a broad, shallow groove and the distal end slightly notched ; size large, R up to 250 mm. Type.—tIn the U. S. National Museum (No. 36951). Type locality —Albatross station 2998, Gulf of California west of Culiacan, Sinaloa (lat. 24°51’00” N., long. 110°39’00” W.); 73 meters ; bottom temperature 64° F.; March 16, 1889. Additional localities —Santa Rosalia, Baja California (Caso, 1947). Zaca station 136, D-14; Arena Bank, Gulf of California (lat. 23°29'30” N., long. 109°25’ W.) ; 82 meters; April 20, 1936 (Ziesen- henne, 1937). Zaca station 142, D-3; Santa Inez Bay, Gulf of California (lat. 27°04’ N., long. 111°53' W.); 73 meters; April 11, 1936 (Ziesen- henne, 1937). Zaca station 146, D-1; Santa Inez Bay (lat. 26°52’ N., long 111°53’ W.) ; 64 meters; April 16, 1936 (Ziesenhenne, 1937). NO: Tt SEA-STARS—CLARK AND CLARK 9 Zaca station 147, D-2; Santa Inez Bay (26°57’30” N., long. 111°48’30” W.) ; 110 meters; April 17, 1936 (Ziesenhenne, 1937). Zaca station 150, D-g; Gorda Banks, Gulf of California (lat. 23°04’ N., long. 109°30’30” W.); gI-109 meters; April 22, 1936 (Ziesenhenne, 1937). Geographical range-—Central and southern part of the Gulf of California. 5 mm Es y Sy © vy) Qe gO OL) 20, = 090 0006 = 0 OCOO9° = O00 oO SURI. Ate soQ00°08 aceecose GH 00 9 920% Ss 00992000 ar OF99g0 co > 29,000 0 OO? 20 99 9 90° ° = S$ 5009050 QD 2009°909 9 0°09° = 2000 02 959900 9 [a] 00009 d é a b c d Fic. 1—Adambulacrals, intermediate plates, and inferomarginals of a, Tethy- aster subinermis (R = 86 mm.) ; b, T. grandis (R = 59 mm.) ; c, T. canaliculatus (R= 64 mm.) ; d, T. vestitus (R= 70 mm.). The adambulacral plate is at the top in each case and is about the tenth, while the inferomarginal corresponding is about the seventh. Bathymetrical range.—From 64 to 110 meters. Remarks.—Our reasons for considering Sefiorita Caso’s Moiraster gigas a synonym of the previously described but much smaller Sideri- aster canaliculatus are the following. The supermarginals of the type of canaliculatus (R = 64 mm.) number 45, those of the type of gigas (R = 205-245 mm.) 58-62. Considering the discrepancy in size this difference is negligible. In canaliculatus R:r = 3.4: 1, in gigas (aver- age) 3.6:1. This difference is not significant. The paxillae on the rays in canaliculatus are in three regular alter- nating rows in the midradial region, and from these central rows diago- IO SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 nal rows run out at an angle of 45° to the superomarginals. Judging from Sefiorita Caso’s figure (fig. 3) there is the same arrangement in gigas, though here the lateral rows make a larger angle with the median. In canaliculatus the enlarged and flattened spines in the infero- marginals are broad, broadly truncate, about half as broad as long, or even shorter, with convex sides, the outer half commonly deepened in the middle or broadly grooved. In gigas these spines are “espa- tuladas, truncadas, aplanadas, ligeramente henidas en sus extremos libres.” In the type of canaliculatus most of the actinal intermediate plates carry one or two enlarged tubercles somewhat swollen in the outer half and frequently somewhat flattened. These resemble the less- developed of the corresponding spines on the actinal intermediate plates in the young specimen of vestitus from Puerto Rico. In the type of canaliculatus all the plates bordering the adambulac- rals and mouth plates, and a few of the other actinal intermediate plates, bear pedicellariae with three or four valves. In gigas also “Todas las placas que limitan a las placas adambulacrales y las placas bucales y alguna que otra placa intermediaria, estan provistas de pedicelarios espiniformis, trivalvados, de forma irregular ; en general, unos son pequefios y otros grandes.” In the largest specimen collected by the Zaca (M.C.Z. No. 36232; pl, 3) R= 95.mm., r= 726 mm.; Rerj=32:6:1.. The ipaxilise have cylindrical columns which are about half again as high as thick and rather slender. The crown consists of 8-10 subcapitate peripheral spinelets, mostly about twice as high as thick at the base, with one or two usually much more slender than the others, and most frequently a single central spinelet which resembles the larger peripheral. There are 54-58 marginals. The superomarginals resemble those of the smaller type specimen (R = 64mm.,r = 19 mm.). The infero- marginals have usually two flattened, tapering, and pointed spines which at the base of the rays are 3-4 mm. long and about 0.75 mm. broad at the base. Each actinal intermediate plate carries in the middle a strongly flat- tened wedge-shaped or narrowly fan-shaped spine with straight sides and a gently convex tip which is usually about twice as broad as the base. These flattened spines, which are mostly 1-1.5 mm. long, lie parallel with the surface of the plate, directed toward the infero- marginals. In addition to these central spines the plates bear a few much smaller subcapitate spines and numerous fine lateral spinelets. The enlarged spines on the actinal surface of the adambulacral NO: LI SEA-STARS—CLARK AND CLARK itil plates are somewhat flaring, abruptly truncated, and broadly grooved or chisel-shaped. A number of the plates in the inner part of the interradial areas, especially those adjoining the adambulacrals, bear pedicellariae of three, sometimes four, valves which resemble stout subcapitate spines, one of which is commonly smaller than the others. This specimen is intermediate between the smaller type specimen and Sefiorita Caso’s much larger type of gigas, resembling the latter in having enlarged and flattened spines on all the actinal intermediate plates. So far as can be judged from the published figure, these spines resemble those of gigas. The spines on the inferomarginals, however, are tapered and pointed and resemble those of grandis more nearly than those of the type of gigas. In a specimen from Arena Bank in 4o fathoms (M.C.Z. No. 3447; pl. 4, upper) with R= 41 im, f=.15 mnt.,.Rir =2.7: 1, the paxil- lae are very low, the thick columns being about as high as broad. The crown consists of 6-7 peripheral granules and one central elongated capitate granule, all similar. There are 39 marginals. The inferomarginals are mostly on the actinal surface, the outer ends curving upward to meet the supero- marginals. In lateral view they are at the arm bases about half as high as the superomarginals, but the height of the superomarginals de- creases so that in the outer half of the ray the two series are, in lateral view, of about the same height. The marginals and the actinal intermediate plates have a similar covering of granules with swollen tips which are not higher than thick, largest and lowest in the center of the plates, becoming more slender along the edges. The spines on the adambulacral plates resemble those of the larger specimen. The very few pedicellariae are in the inner part of the interradial areas. A specimen from Santa Inez Bay in 35 fathoms (M.C.Z. No. 3448; pi 4, lower) with R’=="32°mm:, r= rr mm.,’Rir'='2!9: 1,"and 34 marginals, resembles the preceding, but there are no pedicellariae and the adambulacral spines, though similar, are not so stout. A specimen (M.C.Z. No. 36251) with R = 30 mm., r= 11 mm., R:r=2.7:1, and 30 marginals, resembles the preceding, as does anoter (SCZ: No, 36251) with R*="18'mm., fr ="7 mm. Rer = 2.6: 1, and 27 marginals. In five small specimens from Gorda Bank (M.C.Z. No. 3449) R = 7-10 mm., r = 3.5-4.5 mm. The spines on the adambulacral plates are slender, cylindrical or slightly swollen in the outer part, and little if at all flattened ; they bear numerous fine serrations. All the granules on I2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 both surfaces are more slender, relatively higher, and less crowded than in the larger specimens, and bear very numerous fine serrations. In a specimen from Santa Inez Bay (M.C.Z. No. 3450) with R = 4 mm., r = 2.7 mm., there are 8 marginals. The terminal plate is very large. All the spines and the slender elongate granules are spinulose. With decrease in size the madreporite decreases in relative size and in the smaller specimens cannot be distinguished. In nearly all the specimens we have seen the rays differ somewhat in length, as was the case in Sefiorita Caso’s type of gigas. Specimens examined.—All known specimens except the type of gigas. TETHYASTER VESTITUS (Say) Plates 5-8; text figure 1, d Asterias vestita Say, 1825, p. 143 (description; Cape May, N. J.). Astropecten vestitus LUTKEN, 1850, pp. 27, 54 (listed).—VERRILL, 1866, p. 339 (Say’s record) ; 1895, p. 133 (Say’s record ; “not uncommon farther south.”’) Sideriaster (?) vestitus VERRILL, 1914, p. 21 (identity of Say’s species) ; 1915, PP. 193-195 (discussion). Moiraster magnificus A. H. CLARK, 1950, p. 302 (off Puerto Rico) (not magnifi- cus Bell, 1882). Diagnosis—Enlarged spines on the inferomarginal and _actinal intermediate plates rectangular, sometimes tapering distally, broadly truncate, in fully grown individuals up to 4 mm. long, first appearing when R is about 150 mm.; size large, R up to 250 mm. Description —The paxillae are compact and in contact, with a slen- der tall pedicel 3-4 mm. high and four or five times as high as broad, crowned by a floriform group of usually 20-30 peripheral and 5-15 or more central, terete, slightly tapering, blunt spinelets 0.5 to I mm. long and 3-5 times as long as broad at the base. On the disk and arms they are arranged in rows at an angle of approximately 75° to the midradial line ; in the middle of the interradial areas of the disk there are 4 or 5 usually irregular rows that do not reach the interradial border. The paxillae are largest on the disk, slowly and gradually becoming slightly smaller with more slender, more pointed, and rela- tively longer spinules toward the interradial margins and on the rays. The madreporite is very large, 17 by 16 mm., slightly sunken below the summits of the surrounding paxillae, slightly concave with very numerous and fine, regularly radiating striae. The marginal plates correspond throughout the ray. They are high and narrow with very deep fasciolar channels between them, the chan- NO. II SEA-STARS—CLARK AND CLARK 13 nels being roughly twice as deep as the width of the summits of the marginals or even deeper. The superomarginals, 78 in number, are in the interradial arcs flat and 13 mm. high, decreasing in height to 6 mm. and becoming slightly convex on about the sixth, then remaining simi- lar to near the arm tips. They bear about four rows of elongated granules or short spinelets. The two outer rows are regular and are composed of slightly tapering spinelets, resembling those of the paxil- lae in the center of the disk, and about three times as long as broad at the base; the two median rows are irregular and are composed of shorter and stouter spinelets. On the high, narrow superomarginals in the interradial arcs there are only two rows of spinelets, or an irregular single row, these spinelets resembling those of the outer rows of the outer superomarginals. The inner rows first appear on about the eighth superomarginal. The superomarginals are bordered on each side by an irregular double row of from 30 to 40 slender tapering spinelets which just meet those of the neighboring superomarginals. The lower end of the superomarginals is bordered by a row of about 6 stout spinelets directed diagonally outward. The inferomarginals are about the same size as the superomarginals in the interradial angles but, being more uniform in size, are slightly larger elsewhere. In the interradial arcs they are flat and make a considerable angle with the superomarginals, but they soon become convex, continuing the curve of the superomarginals to the flat actinal surface. They bear a median row of usually four broad, flat, trun- cated, appressed spines 3 to 4 mm. long and 1.25 to 1.50 mm. wide, which overlap the bases of those succeeding. These are flanked by much smaller flattened and truncated spines mixed with more or less terete spinelets. The plates are bordered laterally by very numerous fine, laterally directed spinules resembling those bordering the supero- marginals. Toward the ends of the rays the enlarged spines become very short, not much longer than broad. The terminal plate is rather large, swollen, heart-shaped, with the distal end deeply notched and the proximal end broadly truncated. It overlies about 4 superomarginals. The actinal intermediate areas are large. One series of plates ex- tends to within about 20 mm. of the end of the ray, a second to within about 40 mm., and a third to about the middle. An incomplete and usually irregular row extends from a pair just beyond the mouth plates to about one-third the distance to the inferomarginals. Between the first inferomarginal and the second adambulacral the series con- tains 9 or 10 plates. Deep channels lead from the marginal fascioles to the fascioles between the adambulacrals, these being separated by single 14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 regular rows of actinal intermediate plates. Each of these intermediate plates bears a tall, stout, laterally compressed column somewhat broadened at the summit, which bears a large, flattened, truncated spine 4 mm. long and about 1.3 mm. broad resembling the large spines on the inferomarginals. This spine lies parallel with the surface of the plate and is directed toward the inferomarginals. Occasional plates may carry two or even three of these spines. The median spine is accompanied by a few much smaller, flattened spines or stout spinelets, and the border of the summit of the plate carries a large number of fine, laterally directed slender spinelets directed laterally and arranged in an irregular double row. Ina single interradius seven of the actinal intermediate plates carry a fine, somewhat scattered granulation in- stead of the large flattened spine and the accompanying smaller ones. Many of the actinal intermediate plates adjoining the adambulacrals carry spiniform pedicellariae with usually two, sometimes three, blades. The adambulacral plates are broader than long. The inner half forms an acute angle of roughly 60° and the outer half has parallel sides. At the apex of the furrow angle there is a stout, sharp, pris- matic, slightly recurved spine which in the basal part of the ray is 7 or 8 mm. long. On the sides of the angle are two, sometimes three, similar but much flattened sharp spines of about the same dimensions. The actinal surface of the plate carries usually 4 or 5 spines as stout as the marginal spines but slightly shorter, flattened, broadly truncate, and fluted in the outer half. Each adambulacral plate therefore carries a more or less compact group of usually 9 or Io generally similar con- spicuously large and stout spines. The plates are bordered laterally by an irregular double row of fine spinules similar to those on the actinal intermediate plates. The mouth plates are densely covered with spines, larger on the inner third (toward the mouth) than elsewhere. There are about 6 enlarged and strongly flattened marginal spines which are placed far down on the side of the plate, with a second series parallel with them along the edge of the plate. Beyond the marginal spines the mouth plates carry along their border very numerous, very fine, laterally directed spinules arranged in about three rows. Type—Lost; the specimen described above, from the coast of North Carolina, may be regarded as a neotype. Type locality—Cape May, N. J.; the type was collected by J. Robbins. Additional localities—Twelve miles west-southwest of Diamond Shoal, N. C.; 44 meters; February 6, 1951 (U.S.N.M. No. E.8000). NO. II SEA-STARS—CLARK AND CLARK 15 Caroline station 35; off the west coast of Puerto Rico (lat. 18°24'45” N., long. 67°14’15” W.) ; 146-329 meters; 1933 (U.S.N.M. No. E.3963). Rosaura station 35 ; off the mouth of the Orinoco River ; 86 meters (B.M. No. 1949.1.19.18). Geographical range-—From New Jersey south to the mouth of the Orinoco River. Bathymetrical range.—From 44 to 146 (?329) meters. Remarks.—We have no hesitation in identifying the specimen from North Carolina with Say’s Asterias vestita for the following reasons. The distinctive features in Say’s brief description are (1) the paxil- lae on the abactinal surface ; (2) the large and very conspicuous mad- reporite; (3) the occurrence of about four very much compressed, subquadrate, truncated, and imbricated spines on the marginals; (4) the size; and (5) the comparison with [Astropecten] aranciaca. All these features are equally distinctive of the specimen from North Carolina, but of no other species known from the western Atlantic. The only species that might be considered in this connection is Ver- rill’s Sideriaster grandis, but this is smaller and the spines on the marginals are tapering and pointed, not subquadrate and truncated. In the specimen from Puerto Rico (pls. 7, 8) R = 160 mm., r = 45 mm.; R = 3.6 r (R = 3.9 r in the large specimen from North Carolina). The abactinal paxillae have short, stout, cylindrical col- umns 1.25 mm. high and 0.75 mm. in diameter. The marginals are 75 in number. The superomarginals are densely covered with low, somewhat flattened granules, largest in the middle, and resemble those near the tip of the rays in the large specimen in which, however, the granules are higher. The enlarged spines on the inferomarginals are small, mostly 1.5 to 2 mm. long by 1 mm. wide. Many of the actinal intermediate plates, in some interradii more than half, in others fewer, show the enlarged and flattened spines in various stages of development ; most of them are about two-thirds the size of those on the inferomarginals and of the same shape. A few scattered paxillae on the disk and arm bases carry pedicel- lariae with usually 3, occasionally 2 or 4, blades which are scarcely more than slightly modified spines. A number of the actinal inter- mediate plates of the inner row, especially in the second fourth of the ray, carry a pedicellaria, sometimes two, consisting of scarcely modified spines. The specimen taken by the Rosaura has R= 75 mm. It has not yet developed the enlarged spines on the actinal intermediate plates, but the inferomarginal spines (see text fig. 1, d) are broadly truncated 16 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 or spatulate in shape. There are some actinal pedicellariae. The col- umns of the midradial proximal dorsal paxillae are about 0.35 mm. in maximum thickness, measuring 0.75 mm. in height, or 1-2 mm. including the basal part. The paxillar spinelets are about 0.45 mm. long. The marginals are 52 in number. Specimens examined.—All those known. TETHYASTER MAGNIFICUS (Bell) Plates 9, 10; text figure 2, e-g Archaster magnificus BELL, 1882, p. 440 (description; St. Helena). Moiraster magnificus SLADEN, 1889, p. 193 (reassignment of Bell’s species) .— KOEHLER, 1908, p. 630, pl. 12, figs. 107-110 (Ascension; notes).—MorTEN- SEN, 10933, Dp. 422, text figure 6, pl. 21, figs. 1, 2, pl. 22, fig. 1 (Egg Island, St. Helena; notes).—Caso, 1947, p. 225 (listed). Diagnosis—Enlarged spines on the inferomarginal and _actinal intermediate plates rectangular or even with divergent sides, rarely somewhat tapering distally, broadly truncate, in fully grown individ- uals 6-7 mm. long, first appearing when R = about 70 mm. ; size large, R up to 220 mm. at least. Types (2).—In the British Museum (Nos. 68.6.15.1 and 68.6.15.2). Type locality—St. Helena, collected by J. C. Melliss; no further details. Additional localities —St. Helena, Egg Island; about 73 meters (Mortensen, 1933). Ascension, Pyramid Point; 73 meters (Koehler, 1908). Geographical range.—St. Helena and Ascension. /———— lind =p Imm ed Bll Fic. 2.—a-d, Tethyaster subinermis. a-c, specimen from Naples with R= 55 mm.; a and b, dorsal views of proximal midradial paxillae with and without hiss c, side view of a complete paxilla; d, side view of a paxilla without spinelets from a specimen from Senegambia with R= 72 mm. e-g, Tethyaster magnificus, alcoholic specimen from St. Helena with R = 215 mm. e, paxillar spinelet; f, dorsolateral view of a paxilla without spinelets, and single lobes of two adjacent ones; g, lateral view of two adjacent paxillae with- out spinelets, showing their position in the skin. Drawings by A. M. Clark. NO: II SEA-STARS—CLARK AND CLARK 17 Bathymetrical range-—The only definite records are 73 meters. Remarks.—There are three specimens of this species in the British Museum, all collected at St. Helena by J. C. Melliss, although Bell mentioned only two. The third (B.M. No. 67.12.30.1) is preserved in alcohol but possibly spent some time in formalin since it is in a very flaccid state. The two types are both dry. The larger of the types has R = 215, 213, 222, and 214 mm. on the four entire arms (Bell gives 207 mm.). In the alcoholic specimen R = about 215 mm. Mortensen and Koehler have added considerably to Bell’s original description and the only further points to be made here concern the paxillae and the relative size of the actinal intermediate spines. A strip of the dorsal skin with paxillae from the midradial base of a ray of the alcoholic specimen shows considerable overlapping of the bases of consecutive dorsal plates, although this may have been exag- gerated by the contraction under preservation. In dorsal view the bases of the plates are seen to have much more prolonged lobes than in T. subinermis. The height of the columns relative to their minimum width (4 or 5:1) is also greater than in T. subinermis, but comparable to the proportions found in T. vestitus. The smaller type, with R = 138 mm., has the paxillar columns only two-and-a-half times as high as wide. Its actinal intermediate spines are already large and overlapping, averaging 3.5 mm. in length. The two larger specimens have these spines 5 to 7 mm. long. In Koehler’s specimen from Ascension and Mortensen’s from St. Helena with R about 65 mm. the spines are just beginning to make their appearance but do not much, if at all, exceed their breadth in length. It therefore seems that in T. magnificus the development of the actinal intermediate spines is accelerated so that they first appear when R is about 60 mm., whereas in T. vestitus they begin to develop only when R is about 150 mm. Specimens examined.—The type and paratype and a third specimen also collected by J. C. Melliss at St. Helena. TETHYASTER GRANDIS (Verrill) Plates 11, 12; text figure 1, D Sideriaster grandis VERRILL, 1890, p. 220, pl. 30, figs. 8, 8a, 8b (description; Albatross station 2378) ; 1914, p. 21 (discussion) ; 1915, p. 192, pl. 12, figs. 5-5) (redescription, with the original figures republished). Diagnosis —Enlarged spines on the inferomarginals narrow and sharp-pointed, in some specimens a few also on the actinal inter- 18 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I22 mediate plates; columns of the paxillae low, not over twice as high as thick; no abactinal pedicellariae (on any of the specimens ex- amined) ; rays broad at the base, tapering, the width at base equal to, or greater than, r; first series of actinal intermediate plates reaching to outer fourth of the ray, second to about the middle; superomargi- nals up to 65 in number; paxillae with coarse, elongated granules ; granulation of actinal intermediate plates coarse, coarsest in the center ; conspicuous fascioles present; R up to 160 mm. Description—The paxillae are compact and in contact, with a low, stout pedicel about 1.5 mm. high, less than twice as high as thick, hav- ing a rather strongly concave profile, crowned by a group of slightly elongated, well-separated granules, usually 15-20 peripheral which are about twice as long as thick, cylindrical with broadly rounded tips, and usually 7 stouter and shorter central granules, one in the middle sur- rounded by 6 others. The paxillae are largest on the disk, gradually decreasing in size and with fewer and smaller central granules out- wardly along the rays and toward the superomarginals. In the central part of the rays they are arranged in regular longitudinal rows, on the sides in rows at right angles to the superomarginals, three rows to each two superomarginals. The median row on the rays is some- times slightly larger than the others. The madreporic body is large, approximately circular, Io mm. in diameter, wholly exposed, flat, with numerous fine prominent radiat- ing ridges. It is situated somewhat nearer the interradial border than the center of the disk. The marginal plates correspond throughout the ray. They are high and narrow with shallow fasciolar channels between them which at the base are about half as deep as the exterior face of the plates, be- coming shallower distally. The superomarginals, 65 in the specimen described, are high and narrow in the interradial arcs, 6 mm. high and 1.5 mm. wide, but gradually become wider, after the tenth being 6 mm. high and 2.5 mm. wide, the relation of height to width then remain- ing essentially the same to the arm tips. The superomarginals in the interradial angles bear about 5 irregular columns of granules, those in the middle of the plate the largest, the lateral about half as large; on succeeding superomarginals the granules become smaller and usu- ally more uniform, in 6-8 irregular columns, though often the central granules are enlarged. The superomarginals are bordered on each side by a somewhat irregular row of very fine, closely set spinelets extending laterally over the fasciolar grooves. The inferomarginals are confined to the actinal surface. They are NO. II SEA-STARS—CLARK AND CLARK 19 everywhere of about the same size and shape as the superomarginals. They bear a dorsoventrally median row of usually 4, sometimes 5, tapering, pointed, and flattened spines about 4 mm. long which in- crease slightly in length from the lowest to the uppermost and are ap- pressed to the surface of the plate, each overlapping the base of the one next above. On either side of this median row of spines, and also between them, there are numerous much shorter, more or less flat- tened, truncated spinules. The outer edges of the inferomarginals, like those of the superomarginals, are bordered with an irregular row of very fine, closely set spinules extending outward over the fascioles. The terminal plate is of moderate size, heart-shaped, with the distal end deeply notched and the proximal end slightly truncated. The actinal intermediate areas are large. The innermost series of plates extends to about the outer fourth of the ray (to about 25 mm. from the tip), the second to well beyond the middle (to about 45 mm. from the tip), and the third to about the tenth inferomarginal. Be- tween the first inferomarginal and the second adambulacral the series contains about Io plates. In each interradius there is a median un- paired row of 1-5, commonly 3, plates. The actinal intermediate plates bear 6-12 well-spaced, coarse, elongated granules, which are cylindri- cal with broadly rounded ends, not over twice as high as thick, and are bordered with an irregular row of fine spinules extending laterally over the rather deep fascioles. On the interradial areas the elongated granules are irregularly arranged, but on the rays they become aligned in two or three irregular rows parallel to the axis of the ray. In some specimens some of the actinal intermediate plates in the outer part of the interradial areas may bear an enlarged, flattened, outwardly di- rected appressed spine similar to those on the inferomarginals but smaller. The adambulacrals are at first broader than long, later becoming squarish or even slightly longer than broad; the inner end forms an obtuse angle ; in the middle of the inner edge there is a broad, strongly flattened, recurved spine with a broadly rounded tip; on each side of this, on the edge of the plate, are two flattened but straight and slightly smaller spines. Behind these, on the actinal surface of the plate, there is a row of usually 3 similar spines, and behind these two more, slightly smaller. In the outer part of the ray the median spine in the row of three gradually enlarges, and toward the tip of the ray the median spine becomes long, stout, and conspicuous. The adambulacrals are bordered with numerous fine spinules extending laterally. Each mouth plate bears about a dozen short, stout, somewhat flat- tened spines resembling those on the adambulacrals which they adjoin; 20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 on the border abutting on the adambulacrals the mouth plates are bordered with numerous very fine spinules. The gonads extend almost to the tips of the rays. The occurrence of pedicellariae in this species is very erratic. None of the specimens have any pedicellariae on the abactinal surface, and some have no pedicellariae at all. The one described has a few pedicel- lariae consisting of three blades of slightly modified spines situated on some of the interactinal plates from about the tenth adambulacral to about the middle of the ray. Type.—Presumably in the Yale University Museum. Type locality—Albatross station 2378, off Mobile, Ala. (lat. 29°14’30” N., long. 88°09'30” W.) ; 124 meters; gray mud; Febru- ary II, 1885. Additional localities —Off Sombrero Light, Fla.; 110-128 meters ; yacht Triton, 1951 (1 specimen). M.V. Pelican, between Pensacola and Mobile; March 1, 1939 (1 specimen). M.V. Oregon, southeast of Corpus Christi, Texas (lat. 27°25’ N., long. 96°13’ W.) ; 139 meters ; bottom temperature 60.5° F.; Novem- ber 27, 1950 (10 specimens). Off Tamaulipas, Mexico (lat. 24°10’ N.); 64-67 meters; Hilde- brand, March 1951 (1 specimen). Geographical range-—Known only from the Gulf of Mexico. Bathymetrical range —From 67 ( ?64) to 139 meters. Remarks.—In a specimen with R = 145 mm. some of the supero- marginals in the second quarter of the rays carry small pedicellariae at one or both of the lower angles. The inferomarginals from about the fifth outward carry mostly two pedicellariae, one at each upper angle, occasionally three or only one. The intermediate plates of the inner row from about the eleventh to about the middle of the ray carry usually two pedicellariae, one at each outer angle, occasionally only one. The pedicellariae have usually three, rarely two or four, subequal valves which resemble short spines with a swollen tip. A small specimen from off Tamaulipas, Mexico, with R = 58 mm. and r = 18 mm., is in general similar to the one described. The en- larged spines on the inferomarginals are apparently just beginning to appear. They are mostly about twice as high as the maximum diame- ter, which is usually halfway to the tip, and are stumpy, subconical, slightly flattened, with a subacute tip; a few have acute tips; some are circular in cross section, and some are simply much enlarged granules. There are no pedicellariae. Specimens exanined.—All known specimens except the type. NO. ITI SEA-STARS—CLARK AND CLARK 21 TETHYASTER SUBINERMIS (Philippi) Text figures I, a, 2, a-c Asterias subinermis Puttippi, 1837, p. 193 (description; Sicily) —LAMARCcK, 1840, p. 258 (from Philippi) —MULLER and TroscHEt, 1840, p. 324 (listed). —PreyER, 1886, p. 32 (Naples; rare in about 100 fathoms). Astropecten subinermis MULLER and TROSCHEL, 1842, pp. 74-75 (Sicily ).—Sars, 1850, p. 48 (Messina; 100 fathoms).—DuyarpiIn and Hupé, 1862, p. 425 (coasts of Sicily)—Prrrier, 1875, p. 369; 1876, p. 289 (Nice; Algeria; Mediterranean).—StupeEr, 1884, p. 46 (off Liberia, lat. 4°40’ N., long. 9°10'06” W., 59 fathoms).—Carus, 1885, pp. 90-91 (summary of localities). —PreveEr, 1886, p. 32 (Naples; rare in about 100 fathoms) —Cu£nort, 1888, p. 134 (Banyuls)—Cotompo, 1888, pp. 47, 66 (Naples)—Sruper, 1889, p. 28 (lat. 4°40.1' N., long. 9°10.6’ W., 108 meters).—von MARENZELLER, 1895, pp. 125, 127, 145 (Adriatic Sea, east of Pelagosa, lat. 42°23'00” N., long. 16°21’59” E., 131 meters, sand and mud).—NosrkE, 1903, p. 155 (Setubal) ; 1904, p. 133 (Setubal). Astropecten crenaster (part) DujarpIn and Hupf, 1862, p. 414 (according to Cuénot, 1912).—?FIscHER, 1869, p. 364. Astropecten aranciaca FiscHeEr, 1860, p. 363 (not of Linné = subinermis accord- ing to Cuénot, 1912) (Bassin d’Arcachon). Archaster subinermis PERRIER, 1878, pp. 33, 57, 88 (Mediterranean). Goniopecten subinermis PERRIER, 1885, p. 71. Plutonaster (Tethyaster) subinermis SLAvEN, 1889, pp. 82, 83, 101, 102, 722. Tethyaster subinermis PERRIER, 1894, p. 323; (Talisman station 5, Baie de Cadix, lat. 36°26’ N., long. 8°47’ W., 60 meters, mud and shells; station 15, coast of Morocco, lat. 33°57’ N., long. 10°47’ W., 1,283-1,425 meters, mud, coral; station 66, off Cape Bojador, Morocco, lat. 26°13’ N., long. 17°10’ W., 175 meters, mud, coral). —KoEHLER, 1896b, pp. 450, 451 (Caudan, lat. 45°18’ N., long. 5°23’ W., 180 meters; lat. 45°52’ N., long. 6°03’ W., 250 meters; lat. 46°40’ N., long. 6°30’ W., 300 meters; Talisman, Baie de Cadix and coast of Morocco, 60-1,425 meters); 1806a, pp. 56, 124 (Caudan station 17, lat. 45°18’ N., long. 5°23’ W., 180 meters, gravel and sand; station 20, lat. 45°52’ N., long. 6°03’ W., 250 meters, mud; station 27, lat. 46°40’ N., long. 6°30’ W., 300 meters, mud).—Perrier, 1896, p. 50 (Bay of Biscay, station 44, 166 meters; station 46, 155 meters)—KoEHLER, 1021, p. 54, fig. 40 (range); 1924, p. 200, pl. 7, fig. 4 (range).—MorTENSEN, 1925a, p. 178 (Atlantic coast of Morocco).—CuEnot, 1927, p. 295 (from Cuénot, 1912).— KoEHLER, 1930, figs. I-3 (principally Mediterranean; Portugal; Cadix; coasts of Morocco and Liberia).—RIvERA, 1930, p. 105, fig. 4, p. 106 (Cadiz). —CuMANO, 1934, p. 138 (north of Berlengas )—NobereE, 1938, p. 55 (LeixGes, Bacia do Tejo, Sezimbra), pl. 30 (apparently from Ludwig, 1897), p. 105 (west of Sezimbra) ; TorToNEsE, 10947a, p. 18 (Rodi [Rhodes] ).—Mapsen, 1950, p. 186 (Atlantide station 120, lat. 2°09’ N., long. 9°27’ E., 650-260 meters ; station 163, lat. 13°43’ N., long. 17°23’ W., 65-89 meters; about lat. 30°30’ N., long. 10° W., 100 to 120-500 meters). Plutonaster subinermis Lupwtc, 1897, pp. 105-118, pl. 1, figs. 1, 2, pl. 6, figs. Io- 24 (detailed description; range).—Lo Branco, 1899, p. 473 (Gulf of Naples, very rare, on muddy bottoms, rarely on bottoms of other types).—KoEHLER, 1909a, p. 7; 1900b, p. 22 (Princesse-Alice station 1447, lat. 45°21' N., long. 22 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 2°39’ W., 130 meters, fine sand, July 23, 1903).—-CUENOT, I912, pp. 28, 109 (range) .—GoT0, 1914, p. 3590.—CUENOT, 1927, p. 205.—NoprE, 1931, figs. 42, 43, p. 62 (probably from Ludwig). Thetyaster subinermis NoprE, 1931, p. 62 (west coast of Portugal). Tethyaster Tortonese, 1947b, p. 888 (Rhodes). Diagnosis ——Enlarged spines on the inferomarginals narrow and sharp-pointed, none on the actinal intermediate plates ; columns of the paxillae low, not over twice as high as thick; no abactinal pedicel- lariae; rays broad at the base, tapering, width at base equal to, or greater than, r; first series of actinal intermediate plates to outer fourth of ray, second to about the middle; superomarginals short, 68-85 in fully developed individuals; granulation of superomarginals and actinal intermediate plates fine, uniform, and crowded; size large, R up to 275 mm. Description—This species was described and figured in detail by Ludwig (1897, p. 105). Type.—We have no information regarding the type. Type locahiy.—Sicily. Geographical range——From the Bay of Biscay (lat. 46°40’ N.) south to the Gulf of Guinea, off Spanish Guinea (lat. 2°09’ N., long. 9°27’ E.) ; Mediterranean, east to Rhodes in the Aegean Sea. Bathymetrical range—From about 50 to about 1,400 (possibly 1,425) meters. Remarks.—In a specimen from Algiers (B.M. No. 1947.6.24.1) with R = 110 mm. there are 73 superomarginals. In a specimen from Naples (U.S.N.M. No. E.8001) with R = 86 mm., r = 21 mm., there are 72 superomarginals; in this specimen the mouth plates are fol- lowed by I pair of plates in three interradii, and by 2 pairs in two; these are followed by a midinterradial unpaired row of 5 plates in three interradii, of 4 in two, that reach to the suture between the interradial pair of inferomarginals. In Ludwig’s figure this unpaired median row consists of 5 plates, but reaches only to about two-thirds the distance to the inferomarginals. In a specimen from off Gambia (Alflantide station 163, lat. 13°43' N., long. 17°23’ W., 69-89 meters) (B.M. No. 1950.3.18) with R = 72 mm, there are 62 superomarginals. In a specimen from off Spanish Guinea (Altlantide station 120, lat. 2°09’ N., long. 9°27’ E., 650-260 meters) (B.M. No. 1950.7.3.26) with R= 71 mm. there are 68 superomarginals. In a specimen from Naples (B.M. No. 98.5.3.105-6) with R = 50-57 mm. there are 48 superomarginals. In individuals of this species the rays may be of slightly different lengths. NO. II SEA-STARS—CLARK AND CLARK 23 In some specimens from Naples the paxillae of the midradial row on the rays gradually become enlarged in the outer part of the ray, but this does not seem to be the case in specimens from Algiers or from the Atlantic. Specimens examined.—Five, listed above. TETHYASTER PACEI (Mortensen) Anthosticte pacei MortENSEN, 1925), p. 147, fig. 1, p. 148, pl. 8, fig. 3 (descrip- tion; “Off South African Coast”). Diagnosis.—Enlarged spines on the inferomarginals narrow and sharp-pointed, none on the actinal intermediate plates ; columns of the paxillae low, not over twice as high as thick; no abactinal pedicel- lariae (in the single known specimen) ; rays narrow, width at base markedly less than r; first series of actinal intermediate plates to about the outer third of the ray, second only in the proximal third ; ies E20 Sarl. Type.—tIn the Zoological Museum, Copenhagen, Denmark. Type locality—“Off South African Coast.” Remarks.—This species is known only from the type specimen, which we have not seen. TETHYASTER AULOPHORA (Fisher) Anthosticte aulophora FISHER, 1911, p. 417 (description; Albatross station 5420); 1910, p. 140, pl. 17, fig. 1, pl. 18, fig. 2, pl. 10, fig. 2, pl. 38, fig. 3, pl. 30, figs. 1, 1a-d (redescription).—MorTENSEN, 1925b, p. 148 (com- parison with A. pacei). Diagnosis —Enlarged spines on the inferomarginals narrow and sharp-pointed, none on the actinal intermediate plates ; columns of the paxillae slender, high, about four times as high as thick; most of the paxillae with a pedicellaria of 2-4 valves; R = 162 mm. Type.—lIn the U. S. National Museum (No. 28656). Type locality—Albatross station 5420, between Cebu and Bohol, Philippines (lat. 9°49'35” N., long. 123°45’00” E.); 232 meters; bottom temperature 59° F.; March 25, 1900. Remarks.—This species is known only from the type specimen which we have examined. BIBLIOGRAPHY Bett, F, JEFFREY. 1882. Description of a new species of the genus Archaster from St. Helena. Ann. Mag. Nat. Hist., ser. 5, No. 48, pp. 440-441 (December 1881). 24 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 Carus, J. V. 1885. Prodromus faunae Mediterraneae, vol. 1. Stuttgart. Caso, MAria ELENA. 1947. Estudio sobre astéridos de México; descripcion de una nueva especie del género Moiraster de Santa Rosalia, Golfo de California. An. Inst. Biol., vol. 18, No. I, pp. 225-231. CxiarkK, Austin H. 1916. Six new starfishes from the Gulf of California and adjacent waters. Proc. Biol. Soc. Washington, vol. 29, pp. 51-62, April 4. 1950. A monograph of the existing crinoids. U. S. Nat. Mus. Bull. 82, vol. 1, the Comatulids, Pt. 4c, Superfamily Tropiometrida (the families Thalassometridae and Charitometridae). pp. i-vii, 1-383, pls. 1-32. Cotomso, A. 1888. La fauna sottomarina del Golfo di Napoli. Rivista marittima, Roma (1887). CueEnort, L. 1888. Contribution a l’étude anatomique des astérides. Arch. Zool. Exp. et Gén., ser. 2, vol. 5, suppl.-bis, pp. 1-144, pls. 1-9. 1912. Contributions 4 la faune du bassin d’Arcachon. V, Echinodermes. Bull. Stat. Biol. d’Arcachon, 14° année (I1QII-1912), pp. 17-116. 1927. Contributions a la faune du bassin d’Arcachon. IX, Révue générale de la fauna et bibliographie. Soc. Sci. d’Arcachon, Stat. Biol., Bor- deaux, vol. 24, fasc. 2™°, pp. 229-305. CumaANo, H. 1934. Contribuigao para o estudo da fauna equinologia portuguesa. Arq. Mus. Bocage, No. 5, pp. 137-141. Lisboa. Dujardin, F., and Hup®, H. 1862. Histoire naturelle des zoophytes, Echinodermes, pp. 1-627, pls. 1-10. FISCHER, PAUL. 1869. Echinodermes de la Gironde et du sud-ouest de la France. Act. Soc. Linn. Bordeaux, vol. 27 (ser. 3, vol. 7), pp. 358-376. FISHER, WALTER K. 1911. New genera of starfishes from the Philippine Islands. Proc. U. S. Nat. Mus., vol. 40, pp. 415-427, May 17. 1919. Starfishes of the Philippine Seas and adjacent waters. U. S. Nat. Mus. Bull. 100, vol. 3, pp. i-xi, 1-712, pls. 1-156. Goto, SEITARO. 1914. A descriptive monograph of Japanese Asteroidea. Journ. Coll. Sci., Imp. Univ. Tokyo, vol. 29, Art. 1, pp. 1-808, pls. 1-19, December 17. Grecory, J. W. 1900. In F. A. Bather, A treatise on zoology, ed. by E. Ray Lankester, pt. 3, The Echinoderma, pp. i-viii, 1-344, 309 text figs. London. GruBe, ApoLPH E. 1840. Actinien, Echinodermen und Wiirmer des Adriatischen und Mittel- meers. K6nigsberg. KoEHLER, RENE. 1896a. Resultats scientifiques de la campagne du “Caudan” dans le Golfe de Gascogne. Ann. Univ. Lyon, vol. 26, pp. 33-127, pls. 1-4. [Also published separately, Paris, 1896.] NO. II SEA-STARS—CLARK AND CLARK 25 1896b. Rapport préliminaire sur les échinodermes. Dragages profonde ex- écutés a bord du “Caudan” dans le Golfe de Gascogne (Aoit- Septembre 1895). Rev. Biol. Nord France, 7 année, pp. 439-496. Lille. 1908. Astéries, ophiures et échinides de l’expédition antarctique nationale écossaise. Trans. Roy. Soc. Edinburgh, vol. 46, pt. 3, pp. 529-649, pls. 1-16, December 16. 1909a. Astéries recueillies par l’investigator dans l’Océan Indien. I, Les astéries de mer profonde. Echinoderms of the Indian Museum, Pt. 5, Asteroidea (1). Calcutta. 1909b. Echinodermes provenant des campagnes du yacht Princesse-Alice (astéries, ophiures, échinides et crinoides). Resultats des Cam- pagnes Scientifiques Accomplies sur son Yacht par Albert I** Prince Souverain de Monaco, fasc. 34, pp. 1-317, pls. 1-32. 1921. Faune de France. I. Echinodermes, pp. 1-210, figs. 1-153. 1924. Les échinodermes des mers d’Europe, vol. 1, pp. i-xiii, 1-362, pls. 1-9. 1930. Faune et flore de la Méditerranée. Commission internationale pour l’exploration scientifique de la mer Méditerranée, No. 11, unnum- bered loose-leaf page. Lamarck, J. B. P. A. de. 1840. Histoire naturelle des animaux sans vertebres, ed. 2, vol. 3. Paris. Lo Branco, SALVATORE. 1899. Notizie biologiche riguardanti specialments il periodo di maturita seesuale degli animali del golfo di Napoli. Mitt. Zool. Stat. Neapel, vol. 13, Heft 4, pp. 448-573, April 21. Lupwic, HuBERT. 1897. Die Seesterne des Mittelmeeres. Fauna und Flora des Golfes von Neapel. Monogr. 24, pp. i-x, 1-491, pls. 1-12. LUTKEN, CHRISTIAN FREDERICK. 1859. Bidrag til Kundskab. om de ved Kysterne af Mellen- og Syd- Amerika levende Arten af Sdstjerner I. Naturhist. Foren. Vidensk. Medd. Kj¢benhavn. MapseENn, F. JENSENIUS. 1950. The echinoderms collected by the Atlantide-Expedition 1945-46. At- lantide Rep. No. 1, pp. 167-222, pls. 14-16. MortENsEN, TH. 1925a. Echinodermes du Maroc et Mauritanie. Bull. Soc. Sci. Nat. Maroc, vol. 5, Nos. 4-5, pp. 178-187, pls. 32-34. 1925b. On some echinoderms from South Africa. Ann. Mag. Nat. Hist., ser. 9, vol. 16, No. 91, pp. 146-154; fig. 1, p. 148; pl. 8, fig. 3, July. 1933. The echinoderms of St. Helena. Vidensk. Medd. Dansk Naturh. Foren., vol. 93, pp. 401-472, 29 text figs., pls. 20-22, October 24. Mutter, J., and Troscuet, F. H. 1840. Ueber die Gattungen der Asteriden. Arch. Naturg., Jahrg. 6, vol. 1, pp. 318-326. 1842. System der Asteriden, pp. i-xx, 1-134, pls. I-12. Nosre, AUGUSTO. 1903. Subsidios para o estudo da fauna marinha do sul de Portugal. Ann. Sci. Nat. Porto, vol. 8, pp. 152-160. 26 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 1904. Fauna Portugueza. Ann. Acad. Polytechnica, Porto, 1903-1904, pp. 86-146. 1931. Echinodermes de Portugal, pp. 1-176, pls. 1-14, 74 text figs. Inst. Zool. Univ. Porto. 1938. Echinodermes de Portugal, ed. 2, pp. 1-215, pls. 1-42, Porto. PERRIER, EDMOND. 1875. Reévision de la collection de stellérides du Muséum d’histoire naturelle de Paris. Arch. Zool. Exp. et Gén., vol. 4, pp. 265-450. 1876. Révision des stellérides du Muséum. Arch. Zool. Exp., ser. 2, vol. 5, Pp. 209-304. 1878. Etude sur la répartition géographique des Astérides. Nouv. Arch. Mus. Hist. Nat., Paris, ser. 2, vol. 1, pp. 1-108. 1885. Premiére note préliminaire sur les échinodermes recueilles durant les campagnes de dragages sousmarins du Travailleur et du Talisman. Ann. Sci. Nat., ser. 6, vol. 19, Art. 8, pp. 1-72. 1894. Expéditions scientifiques du Travailleur et du Talisman. Echinodermes. I. Stellérides, pp. i-iv, 1-431, pls. 1-26. Paris. 1896. Contribution a l’étude des stellérides de l’Atlantique nord (Golfe de Gascogne, Acores, Terre-Neuve). Resultats des Campagnes Scientifiques du Prince de Monaco, fasc. 11, pp. viii + 73, pls. i-ic, November. Puriprl, A. 1837. Ueber die mit Asterias awranciaca verwandten und verwechselten Asterien der sicilianischen Kiiste. Arch. Naturges., vol. 3, pp. 193- 194. PREYER, W. 1886. Ueber die Bewegungen der Seesterne. Mitt. Zool. Stat. Neapel, vol. 7, Pp. 27-127. RIVERA, VICTORIANO. 1930. Algunos astéridos de Espafia. Bol. Real Soc. Espafiola Hist. Nat., Madrid, vol. 30, pp. 101-112. Sars, M. 1859. Bidrag til Kundskaben om Middelhavets Littoral-Fauna. Nyt Mag. Naturv., vol. 10, pp. 1-99. Say, THOMAS. 1825. On the species of the Linnaean genus Asterias inhabiting the coast of the United States. Journ. Acad. Nat. Sci. Philadelphia, vol. 5, pp. 141-154. SLADEN, W. PErcy. 1889. Report on the Asteroidea collected by H.M.S. Challenger during the years 1873-1876. Report on the scientific results of the voyage of H.M.S. Challenger during the years 1873-76. Zoology, vol. 30. Stuper, TH. 1884. Verzeichniss der wahrend der Reise S.M.S. “Gazelle” um die Erde 1874-1876 gesammelten Asteriden und Euryaliden. Akad. Wiss., Berlin, Abh. 2, pp. 1-64, 5 pls. 1889. Die Forschungsreise S.M.S. Gazelle in d. Jahren 1874 bis 1876. III Thiel. Zoologie und Geologie, pp. i-vi, 1-322, pls. i-xxxiii. Berlin. NO. II SEA-STARS—CLARK AND CLARK 27 ToRTONESE, ENRICO. 1947a. Note intorno alla fauna e flora marina dell’Isola di Rodi (Mar Egeo). Boll. Pesca, Piscicoltura e Idrobiologia, Roma, Ann. 23, vol. 2 (n. s.), fase. I, pp. 13-20, January-June. 1947b. Biological investigations in the Aegean Sea. Nature, vol. 159, No. 4052, pp. 887-888, June 28. VERRILL, A. E. 1866. On the polyps and echinoderms of New England, with descriptions of new species. Proc. Boston Soc. Nat. Hist., vol. 10, pp. 333-357. 1895. Distribution of the echinoderms of northeastern America. Amer. Journ. Sci., vol. 49, pp. 127-141, 199-212, February-March. 1899. Revision of certain genera and species of starfishes with descriptions of new forms. Trans. Connecticut Acad., vol. 10, pp. 145-234, pls. 24a-30, August. 1914. Revision of some genera and species of starfishes, with descriptions of a few new genera. Ann. and Mag. Nat. Hist., ser. 8, vol. 14, No. 79, PP. 13-22, July. 1915. Report on the starfishes of the West Indies, Florida, and Brazil. Bull. State Univ. Iowa, Bull. from Lab. Nat. Hist., vol. 7, No. 92, (n. s. No. 1), pp. 1-232, pls. 1-29, March 20. VON MARENZELLER, FMI, 1895. Berichte der Commission fiir Tiefseeforschungen. XVI. Zoologische Ergebnisse V. Echinodermen gesammelt, 1893, 1804. Denkschr. Akad. Wien, Math.-Naturw. Cl., vol. 62, pp. 123-148, 1 pl. ZIESENHENNE, Frep C, 1937. The Templeton Crocker Expedition. X. Echinoderms from the west coast of Lower California, the Gulf of California, and Clarion Island. Zoologica, vol. 22, pt. 3, No. 15, pp. 209-239, text figs. 1 and 2, October 7. * 1 Nai ws | ane , hoe ats sty ; ) , r iy ay } ae i ft ‘ 4 SMITHSONIAN MISCELLANEOUS COLLECTIONS WO, ava, INKS atl, TPL al Tethyaster canaliculatus (A. H. Clark), the type specimen from Albatross station 20908, Gulf of California, in 73 meters; abactinal view, X 2. (U.S.N.M. No. 36951.) SMITHSONIAN MISCELLANEOUS COLLECTIONS VOE. 122; NO: 11, PES a 38 = lh ha! 2. : bsp rage erga? ~ Tethyaster canaliculatus (A. H. Clark), the type specimen from Albatross station 2908, Gulf of California, in 73 meters; actinal view, X 2. (U.S.N.M. No. 36951.) SMITHSONIAN MISCELLANEOUS COLLECTIONS VOLE. 222) NOS 1) PES 3 i od PUTAS oe! 4 Lee, Se ad i “as bet: ee Tethyaster canaliculatus (A. H. Clark), the specimen with R95 mm. from Zaca station 142, D-3, Santa Inez Bay, Gulf of California, in 73 meters; actinal view, X 2. (M.C.Z. No. 36232.) SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122, NO. 11, PL. 4 Tethyaster canaliculatus (A. H. Clark): Upper, the specimen with R=,t mn from Zaca station 136, D-14, Arena Bank, Gulf of California, in 82 meters: actinal view. (M.C.Z. No. 3447.) Lower, the specimen from Zaca station 146, D-1, Santa Inez Bay, Gulf of California, in 73 meters; abactinal view. (M.C.Z. No. 3448.) Both figures < 2. SMITHSONIAN MISCELLANEOUS COLLECTIONS VOLES 1227 3NOs 22, PES Tethyaster vestitus (Say), specimen from off Diamond Shoal, North Carolina, in 44 meters; abactinal view, natural size. (U.S.N.M. No. E.8ooo.) SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1227, NOP da Riese Tethyaster vestitus (Say), specimen from off Diamond Shoal, North Carolina, in 44 meters; actinal view, natural size. (U.S.N.M. No. E.8000.) SMITHSONIAN MISCELLANEOUS COLLECTIONS WOE. aban Nol Mabe Teles 7/ Tethyaster vestitus (Say), specimen from off Puerto Rico in 146-329 meters; abactinal view, natural size. (U.S.N.M. No. E.3963.) SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL i227 INO a Plas Tethyaster vestitus (Say), specimen from off Puerto Rico in 146-329 meters; actinal view, natural size. (U.S.N.M. No. E.3963.) Tl bs) NO. ‘he > abactinal view, VOL. 122, ov 68.6.15.1.) No. (B.M. . ot . Stee bewtng ca ws natural size. hes & * a o = vo — v 3) UY} a S =} u Gat v a jan cal ~ ro) = v on wu iss) — v ae) fe) —~ = = vo wy — YS 6 S Se = > DS 8 = nm a ~ ~ Ka S (=9) ~ — ~~ aS sy SMITHSONIAN MISCELLANEOUS COLLECTIONS SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL 1227 NOs sa Pie Tethyaster magnificus (Bell), the larger cotype from St. Helena ; actinal view, natural size. (B.M. No. 68.6.15.1.) SMITHSONIAN MISCELLANEOUS COLLECTIONS VOES 22 INOS Tai Pies a Tethyaster grandis (Verrill), from off Corpus Christi, Tex., in 139 meters ; abactinal view, natural size. (U.S.N.M.) VOLE. 122, NO. 11, (Pian SMITHSONIAN MISCELLANEOUS COLLECTIONS in 139 meters; i, Tex., 1 M.) ist N CUS: 1Ze€ , natural si iew errill), from off Corpus Chr lv randis (V actina gl thyaster ‘eC il oan Sere Persear eee y Pe ee 5 tw S SMITHSONIAN MISCELLANEOUS COLLECTIONS VOLUME 122, NUMBER 12 _ THE REPRODUCTION OF COCKROACHES (Wrre 12 Pirates) BY LOUIS M. ROTH AND EDWIN R. WILLIS Pioneering Research Laboratories U.S. Army Quartermaster Corps Philadelphia, Pa. RE INC RS ay LSM VIG AIS s\g0e SHON er Se *) y § ji 4 (Pustication 4148) CITY OF WASHINGTON PUBLISHED BY THE SMITHSONIAN INSTITUTION JUNE 9, 1954 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOLUME 122, NUMBER 12 fe REPRODUCTION OF COCKROACHES (Wirth 12 PLATEs) BY LOUIS M. ROTH AND EDWIN R. WILLIS Pioneering Research Laboratories U. S. Army Quartermaster Corps Philadelphia, Pa. 83 “S Ax S8eceece® (PusticaTion 4148) CITY OF WASHINGTON PUBLISHED BY THE SMITHSONIAN INSTITUTION JUNE 9, 1954 The Lord Baltimore Press BALTIMORE, MD., U. 8 A. fi REPRODUCTION OF ‘COCKROACHES* By LOUIS M. ROTH anv EDWIN R. WILLIS Pioneering Research Laboratories U.S. Army Quartermaster Corps Philadelphia, Pa. (WITH 12 PLATES) INTRODUCTION Cockroaches are important for several reasons. As pests, many are omnivorous, feeding on and defiling our foodstuffs, books, and other possessions. What is perhaps less well known is their relation to the spreading of disease. Several species of cockroaches closely associated with man have been shown to be capable of carrying and transmitting various microorganisms (Cao, 1898; Morrell, 1911 ; Herms and Nel- son, 1913; and others). Recently there has been a resurgence of inter- est in this subject, and some workers have definitely implicated cock- roaches in outbreaks of gastroenteritis. Antonelli (1930) recovered typhoid bacilli from the feet and bodies of Blatta orientalis Linnaeus which he found in open latrines during two small outbreaks of typhoid fever. Mackerras and Mackerras (1948), studying gastroenteritis in children in a Brisbane hospital, isolated two strains of Salmonella from Periplaneta americana (Lin- naeus) and Nauphoeta cinerea (Olivier) that were caught in the hos- pital wards. Graffar and Mertens (1950) isolated Salmonella typhi- murium from Blattella germanica (Linnaeus) captured in a hospital in Brussels. These latter workers were only able to check the epidemic of gastroenteritis among children by ridding the hospital nursery of cockroaches. Bitter and Williams (1949) have isolated three species of Salmonella from the hind gut of P. americana captured in a hospi- tal, private home, and sewer manholes. It is significant that four strains of poliomyelitis virus have recently been isolated from Periplaneta americana, Supella supellectilium (Serville), and Blattella germanica, which were collected on the prem- 1 This study was made by the Army Quartermaster Corps as part of a re- search program that includes the investigation of the biologies of insect pests of economic and medical importance to the armed services. SMITHSONIAN MISCELLANEOUS COLLECTIONS, VOL. 122, NO. 12 2 SMITHSONIAN. MISCELLANEOUS COLLECTIONS VOL. 122 ises of paralytic poliomyelitis patients (Syverton et al., 1952). In addition to harboring bacteria and viruses, cockroaches also harbor pathogenic protozoans and nematodes. The Surinam cockroach, Pye- noscelus surinamensis (Linnaeus), is the vector of the eyeworm of poultry (Fielding, 1926), and the American cockroach can carry, me- chanically, hookworm of man (Porter, 1930) ; the latter species can also transmit, experimentally, intestinal flagellates such as Giardia from man to rat (Porter, 1918). Although these examples could be multiplied, it is apparent that, as Bitter and Williams (1949) have stated, tolerance of cockroaches around man’s habitations is unwar- ranted ; it may even be dangerous. There are about 450 genera and more than 3,500 species of cock- roaches (Rehn, J. W. H., 1951). Practically nothing is known of the biology of most species. Very little is known of the biologies of the cockroaches associated with man, except for the more common pests such as the German, American, and oriental cockroaches. Yet less than 1 percent of the known species are domiciliary pests (Rehn, J. A. G., 1945). This is a fertile field for future work. Reproduction, enabling the individual to increase its kind many times, is a vital factor in the biology of an insect species. Only rarely do swarms of insects invade a locality from a distant point ; each com- munity usually raises its own insect pests (Metcalf and Flint, 1939). Cockroaches illustrate this principle perfectly. Hence the reproduc- tion of cockroaches is a subject of more than academic interest. Re- production is a phase of cockroach biology that demonstrates the di- versity of behavior that has evolved in this relatively ancient group. In the following pages we shall describe, among several species of cockroaches, these aspects of reproduction: courtship, copulation, re- productive organs and fertilization, parthenogenesis, the ootheca, ovi- position and hatching, and egg parasites. COURTSHIP In general the courting behaviors of the species of cockroaches that have been studied appear to be similar in many respects ; characteris- tic differences, however, lend interest to the study of each additional species. The writers (1952) have studied Blattella germamica, Blatta orientalis, and Periplaneta americana and have analyzed the stimuli involved in the courting behavior of the German cockroach. We could not demonstrate distance attraction between males and females of B. germanica; yet, when a sexually active male comes in physical con- tact with the female he responds with a characteristic courting behav- NO. I2 REPRODUCTION OF COCKROACHES—ROTH AND WILLIS 3 ior. The male turns around so that his terminal abdominal segments are toward the female, and he raises both front and hind wings to an angle of 45° to go° (pl. 1, fig. 1). In this way he exposes glandular areas on his abdominal terga which emit a secretion that attracts the female when she is close to him. A responsive female will feed (pl. 1, fig. 2) on the male tergal-gland secretion, and as she does, the male pushes backward and grasps the female genitalia. In B. germanica the male must make contact with the female before he will court. Mutual sparring with the antennae between the sexes and movement by the female are important actions in stimulating the male to court. The male courting response (i.e., raising the wings) is the overt ex- pression of male sexual stimulation ; it can also be induced by stroking or touching a receptive male’s antennae with antennae (pl. 1, fig. 1), legs, abdomen, or wings, which have been removed from a female. The raising of the male’s wings during courtship, or just prior to copulation, apparently is characteristic of those species of cockroaches in which the males have wings. Raising of the wings has been ob- served in the three domestic species previously mentioned and also in Leucophaea maderae (F.) (Sein, 1923); Blaberus craniufer Burm. [= B. fusca Brunner (Rehn and Hebard, 1927)] (Saupe, 1928; Nutting, 1953) ; Supella supellectiium (Roth, 1952) ; Blattella vaga Heb. and Nauphoeta cinerea (Roth and Willis, unpublished data). Chemical as well as mechanical stimuli are involved in the courting behavior of Blattella germanica. This is shown by the fact that a substance that is sexually stimulating to males can be isolated from females. The cuticular surface of the cockroach is covered with a freely exposed grease (Ramsay, 1935; Kramer and Wigglesworth, 1950). Presumably the sex substance is present in the cuticular grease, because this material can easily be rubbed off from females onto males to make the latter sexually stimulating to other males. The available evidence indicates that sex discrimination by the male German cockroach is mainly effected by contact chemoreception. The sexual behavior of Blattella germanica, in terms of stimulus response and releaser mechanisms, may be summarized as follows: Male courts=raises wings (releaser =| 7 Male makes anten- : mutual antennal fencing between sexes; nal contact with|—> chemical stimulus on the female; move- the female ment of the female) Female feeds on the tergal-gland Copulation (releaser feeding by secretion of the male (releaser—=|——*> the female on the male’s tergal- tergal-gland secretion) gland secretion) 4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 The male receives the female sex stimulus by means of receptors that are present on his antennae and probably on his mouthparts. It is highly probable that in those species of cockroaches in which only the males have a distinctive, externally visible tergal gland, the function of this gland is to entice the female into a position in which mating can occur. Feeding by the female on the glandular secretion or over the dorsal abdominal surface of the male cockroach has been observed in Blattella germanica (Sikora, 1918; Wille, 1920; Roth and Willis, 1952) ; Blatta orientalis (Roth and Willis, 1952) ; Ecto- bius lapponicus Linnaeus and Ectobius sylvestris (Poda) (Koncek, 1924) ; Supella supellectilium (Roth, 1952) ; Blattella vaga, Eurycotis floridana (Walker), Nauphoeta cinerea, and Leucophaea maderae (Roth and Willis, unpublished data). The external appearance of the tergal gland may vary considerably between species and genera (cf. pl. 2, figs. 6-8); this structure has considerable taxonomic value (Hebard, 1917; Rehn, J. A. G., 1931; Ramme, 1951). Frequently the glandular area is a depression in one (pl. 2, figs. 7, 8) or some- times two (pl. 2, fig. 6) of the abdominal tergites and has a mass of secretory cells lying beneath the epidermis. Groups of setae or hairs are often present (pl. 2, fig. 8). In B. orientalis the female moves her mouthparts actively over the male’s dorsum; yet the source of the male’s secretion (if any) is still unknown. Tergal glands are found on the dorsum of the male, female, and nymphs of the oriental cock- roach (Minchin, 1888), but they apparently have nothing to do with sex behavior. The contents of these glands have the distinctive odor of the oriental cockroach (Haase, 1889). In Hawaii, Bridwell (1921), while walking in Palolo Valley at night, saw 50 to 75 Periplaneta americana performing their “mating dance” in the middle of the road. In this species the male sexual be- havior is released by an odorous material secreted by the female. The source of the sex attractant in the female is unknown, but it is a mate- rial that readily rubs off from the female and can be perceived by the male at a considerable distance. By keeping unmated females in con- tainers lined with filter paper, we have collected the attractant on the paper from which the active material was extracted in crude form with petroleum ether. The attractive female odor alone suffices to stimulate the male of P. americana to overt sexual activity. Males will even attempt to mate with pieces of paper or glassware that have been in contact with virgin females. Paper taken from jars containing old, nonvirgin females did not stimulate males, indicating that the sex attractant is produced chiefly by unmated females (Roth and Willis, NO. 12 REPRODUCTION OF COCKROACHES—ROTH AND WILLIS 5 1952). However, it is possible that a mated female may again become attractive (i.e., secrete the attractant) sometime during her lifetime. Neither we nor Gupta (1947) have observed males of the American cockroach courting the female prior to copulation, as is done by the German and oriental males. The male American cockroach is much more direct in his approach, and the female appears to be relatively passive ; movement of the female’s mouthparts over the male’s dorsum is not a necessary stimulus for the male to attempt to copulate, as in the other two species. Summarized, the sexual behavior of Periplaneta americana is as follows: o Male raises wings | Male searches | = Male in the Bee formate (re. and attempts to Copulation H es vicinity of|—> leaser = sex-|—> clasp female’s gen- mae (releaser = the female Saokot teat tee italia (releaser = sex-odor LA) sex-odor from fe- from female) male) In the behavior of Blattella germanica there was a succession of releasers that alternately brought forth responses from both partners before culmination of the sexual act. In contrast the sex odor from the female seems to be the only mechanism involved in releasing a chain of responses by the male of P. americana that ends in copulation. However, the female of P. americana may or may not be receptive to the male’s advances. Perhaps there is an as-yet-undetermined releaser that regulates the female’s response. The males of some species of cockroaches perform characteristic body movements during courting behavior. The male of Leucophaea maderae stands near the female and rapidly moves his body up and down. According to Sein (1923) the male raises the anterior section of his body and strikes his abdomen against the ground producing a prolonged tapping sound. However, we have seen males of this species move the anterior parts of their bodies up and down rather than their abdomens. The male of Blaberus craniifer raises himself on his legs and makes trembling movements with the abdomen (Saupe, 1928) ; we have observed the male of this species behave in a similar manner and also butt the female with his head or pronotum. The wingless male of Eurycotis floridana stands near the female, repeatedly vibrates his body from side to side, and extends his abdomen slightly revealing the light-colored, intersegmental membrane between the sixth and seventh tergites (pl. 1, fig. 3) ; the female then behaves as described earlier for the other species, applying her mouthparts to the male’s dorsum starting near the end of the abdomen (pl. 1, fig. 4) and ) SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 working up to the first abdominal tergite (pl. 1, fig. 5), on which is located a small glandular area bearing a patch of setae. COPULATION The terminal abdominal segments are modified to form the male ex- ternal genitalia, which consist of genital lobes or phallomeres that are associated with the opening of the ejaculatory duct. These structures are described by Snodgrass (1937) and van Wyk (1952). Certain phallomeres of the adult cockroach form highly complex structures with horny processes or hooks. In the female the external genitalia include the ovipositor and associated sclerites and the openings of the oviduct, accessory glands, and spermathecae (Snodgrass, 1937). As we mentioned earlier, while the female Blattella germanica feeds on the male’s glandular secretion, he pushes his abdomen backward so that the female is directly above him. This is the position (pl. 1, fig. 5) just prior to copulation, and it is assumed by most, if not all, species of cockroaches. We have seen this method of initiating copula- tion, in the female superior pose, in these genera: Blatiella, Blatta, Periplaneta, Eurycotis, Nauphoeta, Supella, and Leucophaea. Saupe (1928) and Nutting (1953) observed that the female of Blaberus crantfer also straddles the abdomen of the male just prior to success- ful copulation. Because this behavior is so similar among different genera, we are convinced that it is a regular feature in the copulation of Leucophaea although we have seen it only once. However, Pessoa and Correa (1928) state that the male of L. maderae “draws near [the female] and turns his body in an opposite direction, to that of the female, placing the posterior extremity of his abdomen against [the] posterior extremity of the abdomen of the female.” We cannot reconcile their statement with our observations and those of van Wyk (1952) who saw “that the male carries the female on his back at the beginning of copulation with their heads in the same direction and the venter of the female resting on the dorsum of the male and that they later assume an end to end position.” The relationships of the external genitalia during copulation have been studied in Blattella germanica (Khalifa, 1950), Periplaneta americana (Gupta, 1947), and Polyzosteria limbata Burm. (Chopard, 1919). As the male German cockroach pushes backward under the female, he extends his hooked left phallomere. This appendage clasps a large sclerite located near the female’s ovipositor. If a hold is se- cured on the sclerite, the male moves out from under the female, and the couple assume the opposed position in which their heads face in NO. 12 REPRODUCTION OF COCKROACHES—ROTH AND WILLIS 7, opposite directions. This is the copulating position (pl. 3, figs. 9-14) assumed by all species of cockroaches in which the act has been ob- served ; we have also seen Nauphoeta cinerea in this position, and it has been observed in Polyzosteria limbata (Chopard, 1919) and Par- coblaita pensylvanica (Rau, 1940b). Once in the final opposed posi- tion, two lateral hooks lying on either side of the anus of the male hold the ovipositor near its base. A small crescentic sclerite, which lies on one side near the right phallomere, grips the ovipositor firmly in a medial position (Khalifa, 1950). In successful matings cockroaches remain in copula in the end-to-end position for at least 30 minutes. Usually copulation lasts more than an hour, and Nutting (1953) noted many pairs of Blaberus cranifer that remained joined for 4 hours or more. Statements in the literature to the effect that copula- tion is rapid, lasting only a few seconds or less, were based on observations of unsuccessful matings. INTERNAL REPRODUCTIVE ORGANS AND FERTILIZATION The internal genital organs of male cockroaches consist of a pair of testes, genital ducts, accessory genital glands, seminal vesicles, and a phallic gland (Snodgrass, 1937). In Blattella germanica each testis consists of four rounded sacs or vesicles which open into a common genital duct. Each vesicle is divided into several zones which contain sex cells in various stages of development; the spermatozoa are con- tained in the zone nearest the genital duct (Wassilieff, 1907). The testes of Blatta orientalis mature at the end of nymphal development and atrophy in the adult; hence the spermatozoa must be stored in the seminal vesicles before the testes degenerate (Snodgrass, 1937). The diploid number of chromosomes (including the X chromosome) has been determined during spermatogenesis for several species of cockroaches; Loboptera decipiens Germ. has 34, Blattella germanica 24, Periplaneta americana 34, Periplaneta australasiae (Fabricius) 28, Blatta orientalis 48, and Blaberus fusca [=B. craniifer] 74 (Suoma- lainen, 1946). All species of cockroaches that have been investigated are XO in the male (White, 1951). The sperm of cockroaches is transferred to the female by means of a capsule or spermatophore (pl. 4, fig. 17) formed from the secre- tions of the male accessory sex glands. Spermatophores have been found in males of Blatta orientalis (Zabinski, 1933) ; Blattella ger- manica (Khalifa, 1950; Roth and Willis, 1952) ; Periplaneta ameri- cana (Gupta, 1947; Roth and Willis, 1952); Leucophaea maderae (van Wyk, 1952) ; Eurycotis floridana and Nauphoeta cinerea (Roth 8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 and Willis, unpublished data); and Blaberus craniifer (Nutting, 1953). Presumably spermatophores are produced by other blattids as well. Nutting (1953) observed that the spermatophore of B. craniifer may be retained in the female’s genital pouch for several days, one female carrying her spermatophore intact for 5 days, whereas most of the cockroaches previously noted retain the spermatophore for a shorter period. The accessory glands (“mushroom-shaped gland”) in the oriental cockroach consist of 350 to 450 small, intermediate, and large-sized tubes. Based on their staining reactions, Jurecka (1950) distinguished 6 types of tubes in males of Blatta orientalis; their period of most active secretion occurs for several hours following metamorphosis into the adult. This is followed by a resting period from the time secretion ceases until copulation, at which time the secretions and the spermatozoa are ejected and molded into a spermatophore. The sper- matophore consists of a number of capsules full of spermatozoa (Qadri, 1938); the female carries it 2 or 3 days then drops it (Zabinski, 1933). Van Wyk (1952) described the male accessory glands in Leucophaea maderae. These are composed of approximately 30 to 40 tubules ar- ranged in three groups. He assumes that each group of glands is responsible for one of the three layers of the spermatophore. The spermatophore of L. maderae remains in the genital chamber of the female for about a day before it dries and drops from the female. If the males of Blattella germanica are prevented from mating, the larger accessory gland tubes (“‘utriculi majores”) become so distended with their chalk-white secretion (pl. 4, fig. 15) that they may fill most of the abdominal cavity. After copulation the tubes of the accessory glands are almost emptied of secretion (pl. 4, fig. 16) (Roth and Willis, 1952). The following description of spermatophore forma- tion is taken from Khalifa (1950). The spermatophore in B. ger- manica begins to form in the male as soon as the copulating pair are securely hooked together. In this species the layers of the sperma- tophore are formed from three protein secretions produced by dis- tinctly different groups of accessory gland tubules. The walls of the tubules consist of a layer of glandular cells surrounded by a muscular layer. The accessory glands open into the ejaculatory duct. The se- cretions from the various accessory glands pour into the pouch of the ejaculatory duct, and when the spermatophore is completely devel- oped, it distends the pouch. At one point in the formation of the sper- matophore, sperm flow from each seminal vesicle into a milky middle layer within the spermatophore ; each of the two sperm masses forms NO. 12 REPRODUCTION OF COCKROACHES—ROTH AND WILLIS 9 a separate sac. Following formation, the completed spermatophore descends the ejaculatory duct and is pressed by the male’s endophallus against three sclerites lying on the left-hand side of the spermathecal groove in the female serve for holding the spermatophore. The tip surround the opening of the common oviduct, and the spermathecal groove in the female serve for holding the spermatophore. The tip of the spermatophore, which contains the openings of the sperm sacs, is inserted into the spermathecal groove so that the two spermathecal pores of the female come in direct contact with the two openings of the sperm sacs. The spermatophore remains in the genital chamber of the female for about 12 hours, during which time the sperm mi- grate to the spermathecae. In B. germanica the sperm have to be chemically activated before they leave the spermatophore; probably the activating chemical originates from a pair of spermathecal glands which are associated with the spermathecae of the female. The empty spermatophore dries and shrinks and is eventually dropped by the female. During her lifetime a female may copulate and receive a sper- matophore more than once (Khalifa, 1950), and a male may also copulate and produce a spermatophore more than once (Cros, 1942; Roth and Willis, 1952). The work of the male is now done. The internal reproductive organs of the female cockroach consist of a pair of ovaries, oviducts, spermathecae, and specialized accessory (colleterial) glands which produce the various secretions that go to make up the odtheca or egg case (Snodgrass, 1937, 1952). In Peri- planeta americana each ovary usually consists of eight ovarioles. Each ovariole is made up of an elongated egg tube and a short pedicel which connects the basal end of the egg tube to the oviduct. The an- terior part of the egg tube consists of a germarium made up of odcytes or incompletely formed eggs in the early stages of differentiation, and the remainder or vitellarium contains odcytes in various stages of growth. In the newly emerged adult female all of the oocytes are relatively small, although a gradation in size is noticeable, the largest being at the base (pl. 4, fig. 18). About 8 days after copulation the basal odcyte reaches a final size of about 3 mm. in length; it is now encased in a chorion, and is ready for deposition (pl. 4, fig. 19). After oviposition of the basal odcyte (pl. 4, fig. 20), the next oocyte in line completes its growth; this cycle results in a succession of mature eggs about every 8 days (Gier, 1936). Actually by the time an oodtheca is completely formed and deposited, the basal oocytes of the ovary are already well developed (pl. 4, fig. 21). Scharrer (1943, 1946) found that the development of the eggs of Leucophaea maderae, at least for a certain period of time, is under the hormonal control of the corpora Io SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I22 allata, endocrine glands situated near the brain. Apparently the hor- mone from these glands is not required for the reproductive activity of the male (Scharrer, 1946). The external genital structures of the female cockroach lie con- cealed within a cavity at the end of the abdomen that is closed poste- riorly by the apical lobes of the seventh sternum (Snodgrass, 1952). This cavity is divided into a genital chamber, which lies proximal to the base of the ovipositor, and the odthecal chamber, or vestibulum, which is the posterior part of the cavity. The ovipositor is composed of three pairs of fingerlike valvulae and two pairs of valvifers (Brunet, 1951). The relation of the external genitalia to the forma- tion of the odtheca is discussed below. Dewitz (1885, 1886) described how sperm enter the eggs of Blatta orientalis. The eggs become bent in the oviducts and pass singly into the genital chamber where they approach the spermathecal opening. As the egg passes over the sensory hairs that are found mainly around the spermathecal pore, muscles of the spermatheca contract and force out the sperm. The numerous micropyles, through which the sperm enter, are found at the anterior pole of the egg and come in contact with most of the sperm. The sperm appear to be attracted to the sur- face of the egg and move clockwise rather than in a straight line. The eggs are fertilized as they pass along the vestibulum. PARTHENOGENESIS Parthenogenesis is considered to be a rare occurrence among cock- roaches. The best-known example of this type of reproduction in blattids is the Surinam cockroach Pycnoscelus surinamensis, which in the Indo-Malaysia area is bisexual; but in North America and Eu- rope, where it has been introduced, it is parthenogenetic, producing only females (Matthey, 1948). It is generally believed by most ob- servers that parthenogenesis does not occur in our domiciliary species or at most is a rare occurrence in the American cockroach. However, only recently we have found that some unfertilized eggs of four species of our common domestic cockroaches may complete their de- velopment, and that in two of the species some of the eggs may hatch. Normally, none of the unfertilized eggs of Supella supellectilium or Blattelia germanica hatch, and only a small number of the eggs in an odtheca sometimes complete development (pl. 6, figs. 36-40). How- ever, we dissected an egg case of S. supellectiliwm and removed a fully developed parthenogenetic embryo ; this individual shed its embryonic membrane while we photographed it (pl. 6, figs. 41-45) ; the nymph NO. I2 REPRODUCTION OF COCKROACHES—ROTH AND WILLIS Il was successfully reared, eventually becoming an adult female. On the other hand, some unfertilized eggs of Blatta orientalis and Peritplaneta americana do hatch normally. In fact in P. americana, which has been claimed to be a species in which parthenogenesis is a possible but in- frequent phenomenon (Griffiths and Tauber, 1942), we have found that hatching of unfertilized eggs is not uncommon; of 110 unferti- lized females, 94 (85 percent) have produced odthecae from which some eggs hatched (pl. 6, figs. 46-48). In our experiments, which are still in progress, we have obtained a total of 2,433 undamaged odthecae from unfertilized P. americana females ; from these odthecae at least some of the unfertilized eggs in 1,030 (42 percent) hatched and the nymphs left the odtheca; in 779 (32 percent) some of the embryos developed until their pigmented eyes were visible, or to an older stage, but failed to hatch ; and the eggs in 624 odthecae (26 percent) failed to develop. More than 500 adult females have been reared from parthenogenetically developed eggs ; no males have resulted from the unfertilized eggs. These parthenogeneti- cally produced females lay relatively few eggs and these eggs usually fail to hatch. However, if mated, these females frequently produce eggs that hatch. Parthenogenesis in P. americana is certainly less im- portant than bisexual reproduction in the preservation of this species in nature. However, parthenogenesis could operate among the wild population, and in a temporary absence of males an unfertilized female could transmit some of her germ plasm beyond the end of her own life span. THE OOTHECA FORMATION Kadyi (1879) and others have described the formation of the ootheca of Blatia orientalis. The secretions from the colleterial glands flow out over the inner surface of the vestibulum or odthecal chamber in a sheet that surrounds and is stretched by the incoming eggs. The vestibulum is closed posteriorly by the apical lobes of the seventh sternum. As the forming odtheca presses against these lobes, a char- acteristic pattern (pl. 7, fig. 52) is imparted to the distal end of the odtheca (Wheeler, 1889). After a certain number of eggs have entered the vestibulum, the distal end of the ootheca emerges beyond the end of the abdomen. Pryor (1940a) has described the color changes: At first the projecting portion is an opaque white; within 3 or 4 hours it becomes transparent, changes first to pink, and then to reddish chestnut; the odtheca continues to darken after it is laid, I2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 becoming almost black in about 3 weeks. During formation the an- terior part of the odtheca remains soft and white, eggs still entering and being pushed to the rear. The similar formation of the odtheca by Blattella germanica has been well described by Wheeler (1889). The organic axis of the egg when it is still within the ovary and oviduct of the female is oriented with the cephalic pole directed toward the head of the mother ; the egg then emerges from the oviduct caudal end first and falls into the genital armature caudal end down (Hallez, 1885). Because the odtheca of the viviparous cockroach Diploptera dytiscoides Serville lies on its side within the brood sac, with the mi- cropylar ends of the eggs directed toward the left wall of the brood sac, Hagan (1951) stated, “This fact is of considerable historic interest since it causes the embryos to develop with an orientation contrary to the principles of Hallez’s law.” However, Hallez postulated the orien- tation of the eggs within the ovarioles and oviducts, en route, so to speak, to the odtheca; hence Hallez’s law is not applicable to a sec- ondary orientation of the eggs which depends on any future position of the odtheca. Wheeler (1889) demonstrated this clearly with odthe- cae of Blattella germanica in which embryos developed normally when the odthecae were oriented in five different positions; he concluded that gravitation has no perceptible effect on the development of the eges of this species, and that these eggs have their constituents pre- arranged and completely conform to Hallez’s “loi de orientation de loeuf.” As the eggs move posteriorly, the valvulae of the ovipositor move them into the odthecal chamber and in some way set them on end with their heads upward (Snodgrass, 1952). The eggs from the right ovary pass into the left side of the odtheca and vice versa (Kadyi, 1879; Wheeler, 1889; Wille, 1920). Gier (1947) found that some of the eggs of Periplaneta americana are placed wrong end up in the odtheca, and though development occurs normally, the nymphs cannot emerge from the egg case. We have seen this in Supella also. In the completed odtheca, the eggs are placed vertically and, except at the ends of the egg case, arranged in two rows with the axis of each egg in one row opposite the interval between adjacent eggs in the other row (pl. 4, fig. 24; pl. 6, fig. 35). Figures 25 to 34 (pl. 5) show the external appearance of an odtheca of Eurycoitts as it was being formed. From what we have seen of odtheca formation in so-called vivipa- rous cockroaches (see pp. 25-28), it is similar to that described above. The eggs of Pycnoscelus surinamensis, Nauphoeta cinerea, and Leu- cophaea maderae are erected vertically in two rows in the odtheca NO. I2 REPRODUCTION OF COCKROACHES—ROTH AND WILLIS 1 which stretches around them (pl. 11, figs. 74, 75; pl. 12, fig. 86) as in the oviparous species. In these three species the wall of the ootheca is relatively thin and membranous. The color varies from pale straw to amber. These odthecae do not darken and remain quite transparent as does the odtheca of Blaberus cranifer (pl. 4, figs. 23, 24; pl. 11, fig. 82; pl. 12, fig. 94). The odtheca of P. surinamensis is complete, and although there is no differential keel, such as occurs in the ovip- arous species, there is a narrow, longitudinal slit between the thick- ened edges of the wall of the odtheca along its dorsal surface. The odtheca of N. cinerea is incomplete, similar to that of B. cranifer, and usually does not cover the micropylar ends of the eggs or parts of the sides of the last three eggs deposited. We have seen some egg cases of N. cinerea with eggs attached along the outside, apparently rolled back by the walls of the brood sac from the imperfectly covered ante- rior end of the egg case, as the female retracted the odtheca into the brood sac. Shelford (1906) found that the ootheca of the viviparous cock- roach Panchlora virescens is represented by a complete, thin, trans- parent membrane. However, the membrane forming the odtheca of B. craniifer is incomplete ; as Saupe (1928) and Nutting (1953) point out, the edges of the odtheca are separated by the micropylar ends of the eggs (pl. 4, fig. 24). In Diploptera dytiscoides the odtheca is re- duced to a thin membrane that covers no more than half of the egg mass (Hagan, 1951). Riley (1891a) dissected an “egg cluster” of Panchlora viridis and reported that the ootheca was only a membra- nous sheath enclosing about half the length of the eggs. He reported that in some egg cases of this species the eggs were arranged in a double row side by side, with no visible enveloping membrane. This latter condition seems doubtful ; the membrane may have been so thin and colorless as to be nearly invisible. Or perhaps this was an abnor- mal condition ; Gould and Deay (1940) and we have seen egg masses of Periplaneta americana deposited without an ootheca (pl. 7, fig. 58). Among cockroaches that do not carry the odtheca internally during embryonic development, the hardened odtheca resembles insect cuticle. Both have been shown to be scleroproteins which are very similar if not identical chemically (Pryor, 1940a, b). However, the oothecae of Periplaneta americana and Blatta orientalis contain no chitin (Camp- bell, 1929; Pryor, 1940a), a compound found in varying amounts in insect cuticles. Most of the materials which go to make up the ootheca are secreted by the colleterial glands (Pryor, 1940a; Brunet, 1952). The left colleterial gland secretes a water-soluble protein (Pryor, 1940a) and an oxidase (Brunet, 1952) ; the right gland produces a 14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 fluid containing a dihydroxyphenol, specifically protocatechuic acid (3, 4-dihydroxy-benzoic acid) (Pryor et al., 1946). When the secre- tions from the right and left glands mix, the phenolic substance is oxi- dized, producing a quinonoid tanning agent ; interaction of the tanning agent with the protein gradually hardens and darkens the ootheca (Pryor, 1940a). The odtheca also contains crystals of calcium oxa- late (Kadyi, 1879) ; these crystals occur mixed with protein in the lumen of the left colleterial gland. When the diphenolic substances of the right gland mix with the protein of the left, the calcium oxalate may play a part in maintaining an optimum pH for the oxidation of the phenol (Brunet, 1952). Certain valvulae of the ovipositor of oviparous species are modified to mold the odtheca, especially the crista or keel. Wigglesworth and Beament (1950) have shown this clearly in Blatiella germanica. The chorion along the upper pole of each egg is expanded and forms a vacuolated ridge which lies below the crista of the odtheca of this species. In the keel above each egg, overlying the vacuolated ridge of the chorion, is a small, oval, air-filled cavity which has two lateral ex- pansions that pierce the crista and thus connect with the outer air. These cavities are respiratory chambers which, with associated ducts, convey air to the membranes around the eggs. From the roof of the genital chamber of the female, elongated fingerlike genital appendages project downward into the soft part of the forming odtheca and hold the latest egg in place. Near the base of these fingerlike appendages is a pair of thumblike projections directed backward, which serve to mold the upper cavity of the odtheca and to orient the egg within it. At the base of the thumblike lobes is a small median lobe with a tiny sclerotized horn projecting on either side, which has the exact form of the respiratory chambers and is the die on which they are molded. The colleterial glands discharge their secretions at the base of the geni- tal appendages, and the “horned die” molds the material providing a respiratory chamber and respiratory duct for each egg. In Periplaneta americana the third valvulae of the ovipositor are modified to form the “horned die” which molds the inner surface of the keel of the ootheca (Brunet, 1951). These respiratory structures in the odthecae of oviparous cock- roaches, because of their relatively small connections with the outer air, retard loss of water by the eggs. The importance of this function is emphasized when part or all of the keel has been eaten by the cock- roaches themselves (pl. 7, figs. 56, 57); the eggs in these damaged odthecae usually fail to develop at room humidities, or if they do, rarely hatch. Under these conditions death undoubtedly follows ab- NO. 12 REPRODUCTION OF COCKROACHES—ROTH AND WILLIS 15 normal loss of water. We have found that the rate of water loss from American cockroach eggs at low humidities is greatly accelerated after removal of the keel. Sometimes abnormal odthecae are deposited in which the respiratory chambers are not differentiated in the keel (pl. 7, fig. 60). The oothecae of different species of cockroaches are quite distinc- tive as they may vary in size, shape, and the number of enclosed eggs (cf. pl. 4, fig. 23; pl. 6, figs. 36, 39; pl. 7, figs. 49, 59; pl. 12, fig. 87). Lawson (1951, 1952, 1953) has studied the structural features of the odthecae of several species of oviparous cockroaches. Each egg cell in the odtheca is indicated externally by an evagination (forming half of the respiratory chamber) on each side of the upper part of the keel (Lawson, 1951). Thus the number of respiratory chambers and their corresponding canals (pl. 7, fig. 53), which show clearly in the keels of certain odthecae (e.g., Periplaneta americana, Blaita orientalis, pl. 7, figs. 49, 59, and Eurycotis floridana), is often a good criterion for the number of eggs in the odtheca. This relationship was recog- nized by some early workers. For example Sells (1842) described an odtheca of B. orientalis with 22 to 24 teeth along the serrated edge, which corresponded with the number of eggs contained within. This is rather a large number of eggs for the oriental cockroach, and Sells may have been dealing with another species. We have found that in abnormally small odthecae of P. americana, usually those containing fewer than eight eggs, the number of respiratory chambers and ducts is frequently not the same as the number of eggs in the odtheca (pl. 7, figs. 54, 55). Wille (1920) also found that the number of egg cells in the odtheca of Blattella germanica did not always correspond to the number of teeth in the keel. Occasionally, eggs may be deposited without the formation of a protective odtheca (pl. 7, fig. 58), or an odtheca may be formed which contains no eggs. REPRODUCTIVE POTENTIAL The maximum number of eggs deposited at one time by a cockroach is largely dependent on the number of ovarioles comprising the ova- ries. The number of eggs per odtheca varies with the species. In the oriental cockroach, a species which normally has 8 ovarioles per ovary, the normal number of eggs per odtheca has been stated to be 16 (Seiss, 1896; Rau, 1924; Gould and Deay, 1940). Because there are usually 8 ovarioles in each ovary, it is often stated that Periplaneta americana normally deposits 16 eggs. However, the odthecae of this species frequently contain fewer than 16 eggs. Disease or some ab- 16 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 122 normality of one or more of the ovarioles will reduce the number of eggs produced in an odtheca (Gier, 1947). We have records of one female American cockroach which consistently deposited six to eight fertile eggs per ootheca ; dissection revealed that she had one normal ovary, whereas the other had degenerated ; several eggs had been lib- erated into her body cavity. The number of eggs per odtheca that have been reported for various species of cockroaches are given in table 1. However, because this information is not available for many species, we have included some data on the number of nymphs hatch- ing per odtheca. Counts of nymphs are usually smaller than egg counts because the undeveloped eggs or unhatched eggs left in the odtheca are not included. Among the domiciliary oviparous cockroaches at least, the number of egg cases produced by a female during her lifetime is even more variable than the number of eggs per egg case. There is compara- tively little information about the egg-laying potential of other cock- roaches. Table 2 summarizes the more comprehensive data. Certain unique values have been included because they extend the range of observations. Temperature, fecundation, and age of the female influence the rhythm of egg and odtheca production of Blatia orientalis (Ricci, 1950) ; the rhythm accelerates with an increase in temperature, re- sulting in more odthecae in a given period of time. Diet may also affect the reproductive ability of blattids. Chauvin (1949) found that the fecundity of Blattella germanica decreased considerably on a diet deficient in sterols, and the reproductive ability of these insects dis- appeared almost entirely after two or three generations had been reared on the experimental diet. Noland et al. (1949) also found that the odthecae produced by German cockroaches reared on certain syn- thetic diets were often small, deformed, or shriveled, and only a small proportion of the eggs hatched. This nutritional effect on reproduc- tion could not be traced to any known deficiency in the diet, and these workers suggested that a “reproduction factor” was lacking from the diets. In Periplaneta americana specific diets such as peptone or dex- trose reduced the frequency of odtheca production as well as the num- ber of eggs in the odtheca (Gier, 1947). However, female adults of Blatta orientalis maintained on a diet containing only 2.5 percent pro- tein deposit normal odthecae (Lafon, 1951). The lack of vitamin E in the diet for periods of 4 to 8 months does not influence the vitality of mature sperm of B. orientalis (Kudrjaschow and Petrowskaja, 1937). 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