see pean PF ehetet etal twin ie! et a pte seicaet riod Piatt at tate anes ed eeetenetelanl stt or eme ads a iS ba a Sia heated el tne oar reer wee ere al mite mete ee Tato eae eet etl Pr ah gat ee whaler eter" fie tne | eases wo we et: wide dnd a ipedetnte r la Wine re eet a anna Sad ee nn hand aoee aioe eels! st — sag a at ae NO ne hai aa eer = ee aeietied ree ee maha ee a peel a * ers ated oes Ag ene phenetntete: ‘pate derers eam Daher -¥— aes aden nat ote cananecreteie viotebatatolaler esi oi aiatada ete aa os mn etennierrets haa) bp es Paseiwietshedy ami wes UM ee Wee | eae eh at Vy aa Aa aanprrAr” | AAAR apa aa WamaA saan, Anh Aa ue sigh, scammmersennt creens Ce Saytee ana ata aM, Aa 2» » > » ae ¥ loa a _ 3 a ~ PaAnA AD A oe [ener AAan See ry a, os ac NO 3 ay Nol aben x Se oe oe PA AAA ost re oe Be ie Br tek yt Sis a? PE apts conyers ‘ TTT cea eet eas siete ¥ Vas) pRONARAS Ein AAs RAM AGS aBapanm nn AAi Rn \AAeags AAA” aaa we ape aannaaars AASa2., rt Py} a ] AA _ agin , a an im AA + y vee ey naan PP tt aaa AA 2 Aas / pane nm gas Aan pA an SAR A m nana Kiecsrveces peer ty ef el = AMAA p Aa ae - s ant 2 prrr,asl ‘ TR Af he Rap aa ea dads ae TAs mm am a TAN yalh aa Ae eer naan .- » » >» py >» > oe >> 2 »» > y , ’ >» 4 Ail oh 201 204 ORGURRSRAR BE AAAS mn BREE uae aA sNanaes 7 ARRAAAR, Pre ay = tetas , A Ama, Bree A An v lal “Wi het “a ie Ree i Aaa mahan anne napit? a A Ma a AAMAAPAA, : Apr Cee eo ; AaAAIA F eee baat Anas ALLVTY aA aan An- Am Pes 2 UP Pies s “KAS att pana: tha Ap AAAAR ARB ANAC Ranh ae A oi 3224 ABABA Ree ae senmmeccee eae unitate ance eae ra ‘ A, ry | Ae Ano ase os a nA Aa rn” AR aA A | PAAR ater Reet nan, AAA, (AAMAaam wai ai peo oh a es sAnAaa A ann aa ¥ “0 ie" f ‘ : hy Pe. Yee: ; z Ls ‘ - oe a Wg soy: a f ss « . ies ia a ae ‘es b. SS “Sf (U.S. DEPARTMENT OF AGRICULTURE, aN BUREAU OF ENTOMOLOGY—BULLETIN No. 76. | L.O. HOWARD, ‘Entomalieist and Chief of Bureau. FUMIGATION FOR THE CITRUS WHITE FLY, AS ADAPTED TO FLORIDA CONDITIONS. BY A. W. MORRILL, Pu. D. Special Field Agent. IssuEeD OcToRER 31, 1908. - WASHINGTON: Al GOVERNMENT PRINTING OFFICR. BOZ4A0 1908. Y Ni 4 Latins ry feo. DEPARTMENT OF AGRICULTURE, BUREAU OF ENTOMOLOGY—BULLETIN No. 76. L. O. HOWARD, Entomologist and Chief of Bureau. FUMIGATION FOR THE CITRUS WHITE FLY, AS ADAPTED TO FLORIDA CONDITIONS. ( BY A; W. MORRILL, Pu. D. Special Field Agent. ISSuED OCTOBER 351, 1908. WASHINGTON: GOVERNMENT PRINTING OFFICE. 19:08. a ==) a BUREAU OF ENTO MOLOG Y. L. O. Howarp, Entomologist and Chef of Bureau. C. L. Maruarr, Entomologist and Acting Chief in absence of Chief. R. 8. Cuirron, Chief Clerk. F. H. CuitrenveEN, in charge of truck crop and special insect investigations. A. D. Hopkins, in charge of forest insect investigations. W. D. Hunter, in charge of southern field crop insect investigations. . M. Wesster, in charge of cereal and forage plant insect investigations. . L. QUAINTANCE, in charge of deciduous fruit insect investigations. . F. Putuuies, in charge of apiculture. . M. Rocers, in charge of gipsy moth and brown-tail moth work. . F. Fiske, wm charge of gipsy moth laboratory. . A. Hooker, engaged in cattle tick life history investigations. A. C. MorGan, engaged in tobacco insect investigations. R. 8. Woeium, engaged in hydrocyanic acid gas investigations. R. P. Currts, assistant in charge of editorial work. Mase. Coucorp, librarian. Ser sy aa as Wuarire Fry INVESTIGATIONS. C. L. Maruarr, in charge. A. W. Morritu, E. A. Back, W. W. Yoruers, special field agents. ) a LETTER OF TRANSMITTAL. U.S. DEPARTMENT OF AGRICULTURE, Bureau or ENTOMOLOGY, Washington, D. C., June 11, 1908. Srr: I transmit herewith, for publication as Bulletin No. 76 of this Bureau, a report on fumigation for the white fly, as edapted to Florida conditions, by Dr. A. W. Morrill, special field agent. The investigation of the white fly problem in Florida is now in its second year, and the results gained of immediate practical importance are those which indicate best methods of control. Fumigation with hydrocyanic-acid gas during the short dormant period in winter, when there are no winged insects, seems to afford the greatest measure of control or possible extermination. Gas fumigation under the horticul- tural conditions obtaining in Florida orange groves and the peculiari- ties of climate presents rather a distinct problem. This bulletin gives the results of the fumigation experiments of two winters in Florida, and demonstrates the entire applicability of this method of control to the white fly. This investigation has been under the general direc- tion of Mr. C. L. Marlatt, Assistant Chief of this Bureau, with Doctor Morrill in field charge. The latter was aided during the winter of 1906-7 by Mr. Stephen Strong, formerly horticultural commissioner of Los Angeles, Cal., and an experienced fumigator, and Mr. A. C. Morgan, and during the winter of 1907-8 by Messrs. E. A. Back, W. W. Yothers, and R. S. Woglum. The white fly is the big insect problem of Florida and other citrus districts on the Gulf coast, and the information given in this bulletin will be of immediate practical value to all citrus growers of the region indicated. Respectfully, L. O. Howarp, Entomologist and Chief of Bureau. Hon. JAMES WILSson, Secretary of Agriculture. ; ‘eam CONTE NAS: Page. Maremma petra = 5 SE. OP oe oe ee eae et ee ec ee 7 Conditions favoring or necessary to good results. ........------------- Pee ss 9 HOlAn ION: OL PTOVG 25 Re nach reese g erate Sas anor eyo ee eer ean el 9 @onicervedsaACttO mes. oa No Seer. Se ett stecta Scere np re Scheel ated tee eer ie 9 Absence or elimination of food plants other than citrus.......----.-------- 9 SEasOnkOls ii enyjenin stein eer sere. Sy as See eee eee eerie 10 Metecralosiealtelementse 5. 9. =< 122: Ss - Sas eee See iit Size on treesanumeertlatihyOr SCbing. =+.. 2 225s 22s a e222 2 - meetont e ee 14 fie aap et eae eee ete 2 Se oe nee eee a 14 ENS 2 crook cess WaseSe ROSES BOSE ee Ree ae ORE AE arte enor 14 SWIG? G06, TITAS oc cena ee eee ee Soe 20 Miccellaneoadreqiirements: 2.241.522 2 22 32 ace ats wep Sc oes ate a 22 NE GSEOR ES 2 chee ols ee eg se 25 Merreciompuminy TeQuUined..,.-. 22. /0r= 2452s See ieee hs oe G oe eos See See ee 25 Handling, and necessity for protection from moisture. ....-.-...--.------ 25 gREDOR OM Ol- Water ANG ACG...) 75. > Af. de hoa as pee Dees os Se 25 Aeraa CHIT Nese he a oe eens! te ite is Mee Ae Oe hse os we ee oie 27 Reged som Mancino GEMS. yee con SAG evo a ee oe mil JOOS TINTS TRS S aS OES Se ae Ae eee aire noes Sener = 8 52 Sten Serr 30 Meprodkarceneratme the Pas. 5.2 sats Jo S)-s avin <5 - See ota eee eee 35 Work routine....--- See tee ie Ses eS anes AiR Spee Pe See SA Se 36 Estimation of time required for fumigation of grove.............-.---------- 38 Methods of computing approximate dimensions and cubic contents. ......---- 39 Dusacemeduirements for the white fly... +... - £0. .5--0l<5¢ 50. -2 sus e-s tz ee 40 Heamcnumentaawinl sheet tent... .. 5.5.22. -5. 21S cbs cesses esos eee we 40 Beperinents wat bellior hoopitent.. 222-2... 2.2 et Es ese 49 Miscellaneous experiments and observations..............--.----------+---- 50 Appearance of larvee and pupze of the white fly when destroyed by fumiga- LO Weta Oe yeversiaieis sciet=avaereteta tA Save eee phates 5, ED een Sri tees eels ates 50 Density of the gas at various heights above the ground.............------ 51 Mecho Mme MON OM .UNG LTGeSs .. eos. 2 ogous soe e oe es wee ea alse 51 Bupecsiions forthe tumigation of small tréees....-22.-.2.-, 222... 3.25. 22s see 5 54 [si (NS! CRON Ei Ee ea a gem ee A Te ays ing ihteemurseryecme ser saa we Rs ie Se Se aS es Satee ae 54 Mursery. shock 1Or cimpMeMt = 9-228. 0-2 See See Ses. Ses en dees mae eee 54. Bsr eecierteiciia meee ae ee eet! ns fe Se ee eS SS at Soc eae ae 55 Remnern ero humnn oa ION <> sarees See ss SEA SD oo Socew eaten as 2 56 DiSTE S:B UT OUP TUT IS ERO oO 8 ee ae i Sn am eS 56 LOTS GIVSOUUICHY SS) eat en 8 SO a ae eA a en ee eS See 58 CSOT ENG ELE Ee RR SS PER ee, 1 ek ae Re ee Fs 58 Hecnuiingotiresjinent by, fumigation... 2.0.22 2..-.-----2220--2.ss-sneet= se 59 USE ES LEIS SOUS ee em Na ee 59 Cosmowmmiationicompared with spraying.......--....------+-.--Gs The number preceding the decimal point indicates the length of exposure. CONDITIONS FAVORABLE OR NECESSARY. 13 On several occasions it was observed that the tent felt somewhat damp when being handled, although the humidity recorded by a standard sling psychrometer had not reached complete saturation. On other occasions, as shown by the above data, the foliage was covered with a dew like a fine mist when the sling psychrometer indicated as much as 6 per cent below complete saturation. For practical purposes, however, the moisture on the leaves may be considered as indicating a condition of 100 per cent atmospheric moisture. Blank spaces in the table indicate that no note was made concerning this particular point, although the tent was evi- dently ‘“‘wet”’ in experiments 40.2 and 50.2 and the leaves were evidently ‘“‘dry”’ in experiments 45.21 and 45.22. In the experi- ments summarized in Table I the possibility of reducing the efficiency of the gas through absorption by the moisture on the leaves and tent had to be taken into consideration. To eliminate this feature and to determine the effect of the gas on larve and pupz of the white fly when leaves are wet artificially, tests were made by wetting the leaves both by dipping and by means of an atomizer. The results are summarized in Table II. Taste Il.—Effect of artificially wetting leaves on efficiency of fumigation. Per cent | Total Amount Number : a soa earpa|| aallu eal] oes nol eae = of insects) Peper) air nu- | Amount of cranid of insects eG cent [OF sets killed on | Method of No midity. | used mended | Under | ‘Lilled. | wet arti-| leaves wetting. : ~ |in table. | ObServa- : ficially. | wet arti- ie tion. “* | ficially. Per cent.| Ounces. | Ounces. 30.6 | 20 29 242 71 21 | 95.2 | Dipped. 40.6 47 | 173 21 392 88 149 | 90.6 | Sprayed. 40.7 55) | 8h 13 132 80 40 87.5 Dipped. 40.8 61 174 293 223 96 93:.| 98.9 Sprayed. 40.9 54 12 27 342 93 20 | 95 Sprayed. 40.13 63 24 28 736 - 100 567 | 100 Dipped. In the above experiments—omitting the last one, in- which all insects were killed—1,331 insects were under observation. Of these, 323 were on leaves wetted artificially. The weighted average of the insects killed on these leaves is 92.5 per cent. Of the 1,008 insects on the dry leaves 852, or 84 per cent, were killed. This seems to be of considerable significance in view of the fact that in every instance where less than 100 per cent of the insects were killed, the percentage of killed was greater on the artificially wetted leaves than on the dry leaves. Taken as a whole the results summarized in the two foregoing tables show conclusively that moisture on the leaves in the form of dew does not reduce the efficacy of the gas in destroying the insects, but possibly increases it. In the experiments in which moisture was a factor no injury to the foliage followed, even when the dosage was increased fully one-half above the amount called for by the table in the appendix of this bulletin. The results give no justification to 14 FUMIGATION FOR THE CITRUS WHITE FLY. the practice of some fumigators who, as has been stated, increase the dosage when the tents and foliage are wet with dew. It seems that the difficulty in handling wet tents is the only consideration for which it is necessary to cease work on foggy nights, everything else being favorable. SIZE OF TREES AND REGULARITY OF SETTING. While it is true that it is possible to piace a fumigating tent over any citrus tree regardless of size, the author strongly recommends that orange growers make a practice of pruning large seedling trees so that they will not exceed 28 or 30 feet in extreme height. Such pruning will greatly reduce the cost of labor in fumigating and will be of considerable advantage from the standpoint of picking the fruit. It is probable that the now generally recognized all-around advantage of low-pruned fruit trees applies equally well to citrus as to other kinds of fruits. Another consideration of importance is the regularity in the setting of orange groves and the proper spacing of trees. In Florida various factors have resulted in many groves being too crowded or too irregularly set to permit of the easy handling of fumigating tents. While it is well to bear these things in mind to the end that all Florida groves may gradually be adapted to reduce the labor and expense of fumigation, yet even under present conditions it is exceedingly rare that fumigation is rendered abso- lutely impracticable by the size of trees or the irregularity of their setting. EQUIPMENT. TENTS. Styles of fumigating tents—Two styles of tents are now in use for orchard fumigation, the bell or hoop tent (PI. I.) and the sheet tent. The first is bell-shaped and held open at the mouth by a hoop of $-inch gas pipe. Tents of this style are preferable for use only when the trees in a grove are uniformly less than 12 feet in extreme height. Sheet tents are made in the form of flat octagons and, being adapt- able for trees of all sizes, are in California used almost exclusively. Plate I, figure 3, shows a tree which is 14 feet in extreme height and 14 feet in extreme expanse, covered by a hoop or bell tent. When the tent is in position covering the tree the measurements are: Height, 13 feet, and diameter, 12 feet. Hoop tents are not always easily placed in position over trees of this size, and it is believed that ordi- narily a sheet tent is more desirable for trees of all sizes. A third style of tent which will be found useful in fumigating small trees is the box tent in the form of a rectangular prism. This will probably prove advantageous for trees 5 feet or less in height. The light wooden framework supporting the cloth cover gives a form to the Bul. 76, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE |. Fias. 1-3.—METHOD OF COVERING SMALL TREE WITH BELL OR Hoop TENT. (ORIGINAL.) TENTS. 15 inclosed space which permits of economical use of chemicals with greater uniformity of results. “onstruction of tents.—The construction of the box covers such as rested in the foregoing paragraph is a simple matter and con- _...ent patterns will suggest themselves at once to anyone desirous of fumigating small trees. The framework should be light but well braced, and for a covering either 64-ounce drill, painted to render it 1s nearly gas-tight as possible, or oilcloth is recommended. Prof. C. W. Woodworth, of the California experiment station, gives the following directions for cutting the cloth for bell tents: 4 All of these tents are made in the same manner, and are the most economical in cloth of any tents made. Commonly the tent is made by the ‘“‘cut and fit” method. These tents may be made with scarcely any loss, if cut according to the following directions: Measure off strips of a length equal to twice the height plus one-tenth the diameter of the tent desired. These will make two strips each by marking the exact middle and measuring off on one edge from the middle line one-quarter of the diameter of the tent and on the other one-half the diameter. Now, take a long strip of molding and bend it so as to touch these three points and mark off the curve so produced. This allows for the seam. In making up, sew the two cut edges together in each pair of strips. As has been stated, sheet tents, or more properly covers, are flat, regular octagons. The dimensions are sometimes stated in terms of the true diameter (i. e., the distance between opposite corners), but for practical purposes the distance between parallel sides should represent the size of the tent, for the reason that this represents within about 2 feet (which must be allowed to rest on the ground) the distance over the tallest tree that a given sheet can cover meas- uring from the ground on one side to the ground on the other, over the center of the tree. Hereafter in this bulletin the size of octagon covers as stated should be understood to refer to the distance between parallel sides. The specifications should be carefully worked out before beginning the construction of a sheet tent as well as of other styles. First, the dimensions of the tallest tree which the tent is required to cover should be estimated. This may be accomplished by throwing a tape attached to a reel over the top of the tree and measuring from ground to ground. When covered, the weight of the tent will reduce the extreme height of the tree~in most cases by from 2 to 4 feet, according to the weight of the tent and form of the tree. It will be well to allow at least 4 feet of the tent to rest on the ground when covering the largest tree. The desired size having been determined, a diagram of an octagon should be constructed on paper, as indicated in figure 1. Each side of the octagon when constructed will be equal approximately to two-fifths of the distance between the parallel @ Circular No. 11, Cal. Agr. Exp. Sta., pp. 9-10. 49918—Bull. 76—08——2 16 FUMIGATION FOR THE CITRUS WHITE FLY. sides of the octagon. The number of square yards of cloth required is about 18 per cent, or between one-sixth and one-fifth less than for a square the sides of which are equal to the distance between parallel sides of the octagon. In California 8-ounce army duck has been used almost exclusively for making sheet covers, while in Cape Colony, South Africa, a No. 10 duck ranking in weight between 12-ounce and 15-ounce is commonly used. The heavier weights are not only more durable but presumably confine the gas better. A good grade of 63-ounce drill, however, as shown later by the results obtained with a bell tent of this material, seems to be fully equal to the 8-ounce duck commonly used in Cali- forma. Until careful experiments shall have determined the relative tightness of various weights of duck it is recom- mended that sheet tents be constructed throughout of 8- ounce duck or of 8- ounce duck in combi- nation witha “skirt” of 64-ounce drill. The author has seen a sample of 8-ounce drill which is no more expensive than the best brands of duck of this weight, but is evidently far superior Fic. 1.—Plan for construction of octagonal sheet tent 50 feet across, showing lines used in constructing octagon: A, C, sidesections; B, gs regards tightness. central section of full-length strips; E, Z, so-called ‘‘ends” of tent; 7 S, S, so-called ‘‘sides”’ of tent; R, R, reinforcements; 1-21, strips Anyone contemplat- of duck 29% inches wide, overlapped 4 an inch at the seams. ing the ordering of (Original.) 5 : a fumigating outfit should procure as many samples as possible of different brands of suitable cloth and select the closest woven brand. The strips when cut should be overlapped three-eighths or one-half inch and double stitched and all raw edges should be hemmed. In calculating the number and length of strips the overlapping will reduce the width of the cloth from three-fourths inch to 1 inch. As an illustration of the method of calculating the length of the strips used in making an octagonal tent of S-ounce duck, 50 feet may be taken as the desired size. This is equal to 600 inches and the width of the cloth, if 29.5 inches, will be reduced to 28.5 if overlapped one- half inch at the seams. By dividing 28.5 inches into 600 inches the TENTS. A ( nearest multiple is found to be 598.5 inches, or 49 feet and 104 inches, which is sufficiently close to the desired width for practical purposes. The number of strips in a tent 598.5 inches wide is 21. The middle section B (fig. 1) is approximately two-fifths the entire width, or 239.5 inches. Deducting this from 598.5 inches, the entire width, the remainder, 359, equals the sum of the widths of sections A and C. These sections being equal, the width of each is 179.5 inches. The number of strips in each section can now be readily calculated. The 21 strips should be numbered on the diagram from left to right. Section A requires six strips and 8.5 inches of the seventh. Simi- larly, section C requires six strips, beginning at the right (twenty-first to sixteenth, inclusive), and 8.5 inches of the fifteenth. Section B requires the remaining 20 inches of strip No. 7, 20 inches of strip No. 15, and seven entire widths, thus making the total of 21 strips required. The cutting of the cloth can be done without waste if the details of construction are well planned. In the above tent seven strips 50 feet long (49 feet 104 inches) should first be cut for section B. Strips Nos. 7 and 15 are next cut and the outside corners cut at an angle of 45 degrees, as indicated in the diagram. Each strip for sections A and C is cut shorter by its own width outside at each end than the strip preceding it. Thus the required lengths of the side strips are found by matching the inner edge of the new one to the outer edge of the one before it. It is desirable to have the central section, B, made up entirely of full-length strips so that the stress will not be across seams. The stress is so slight, comparatively, in the side sections A and C, that this is not an important point. Shrinkage of the goods after being thoroughly wet is an impor- tant consideration in the economical construction of fumigating tents. In order that the tents approximate a regular octagon, after having been used for fumigating purposes, it is necessary either to have the goods thoroughly shrunk before cutting or to make allow- ance for subsequent shrinkage by cutting the strips longer. i 129 adX.6 45h | 53 3, 272 TGrH |} eee Or 174 189 | 27% 119 eX.5 473 54 3, 713 Weer 1:2.09 | 244 151 30 123 fX.3 473 54 3, 713 Ie 1:2.09 | 283 130 30 || 123 a One of several trees fumigated on nee of Hiei 1,1907. U Baaiierotory aig) SGamneate to ie ie to poor quality of acid. b Exposure, 1 hour and 45 minutes. ¢ Exposure, 2 hours and 50 minutes. d Exposure, | hour and 30 minutes. exposure, 1 hour and 35 minutes. # Exposure, 1 hour and 55 minutes. For purposes of comparison with Table V, the data on the dosage experiments in which all of the insects were believed to have been killed in forty-five-minute exposures are given in Table VI, which, like the preceding, includes the rate and amount of dosage calculated according to the dosage recommendations hereinafter given. 44 FUMIGATION FOR THE CITRUS WHITE FLY. Taste VI.—Data concerning dosage in those experiments in which 100 per cent of white Jlies were destroyed. Measurements | Amount! Rate: Experi-| of tented tree. SDE Approx- | Ratio of | Rate: | cyanid | Number CN) |= eorsraevei: Nae leakage | anton Number | recom- cubic feet No. Dis- Cire An enue lasienes surface | ecyanid |cubicfeet | mended per ounce (series ¢once lcumfer-| closed peers to cubic | used. jper ounce} in table | cyanid Ho |) asso. |) eae ane contents. cyanid. | given in | recom- ; aa DUCE: appendix | mended. | | | Feet Feet Cutts |) Sq- ft: | Ounces. Ounces. 30 20% 30 735 683 1:1.08 | 6 118 os 77 13 31 38 1,149 754 1:1.52 114 100 11 104 19 | 314 39 1,219 779 1:1.56 144 84 114 106 26 | 33 46 1, 656 855 1:1.93 13 127 14 118 33 | 344 36 1,224 935 1:1.31 10 122 13 94 12 343 43 1,620 935 UE Tes 153 103 14 116 24 343 47 1,855 935 1:1.98 153 119 154 119 17 363 455 1,888 1,043 1:1.81 21 90 17 lil 9 364 48 2,049 1, 048 1:1.96 21 98 17 120 1 37 47 2,075 1,075 1:1.93 21 99 17 122 34 40 44 2, 092 1, 256 1:1.66 21 100 184 113 1 0235) tis 40 47 2,341 1, 256 1:1. 86 20 117 20 117 6 433 56 3, 412 1, 482 1:2.35 224 151 264 129 8 443 58 | 3,691 1,554 1:2.37 27 136 29% 125 4 45 57% 3, 732 1, 589 1:2.34 23 162 28% 131 10 453 67 4,665 1,625 1:2.87 35 133 344 132 23 463 56 3, 556 1,697 122.15 29% 124 30 118 25 483 57 4,095 1, 846 ley ApAL 333 122 33 124 7 504 56 | 4,275 2,002 12513") 36 119 34 125 These tables show that with tents of 8-ounce duck and untreated with paint or sizing there is little or no advantage in exposures of more than 40 minutes. The results with exposures of 30 and 40 minutes compare favorably with those ranging from 45 minutes to 2 hours and 50 minutes. It is evident that the gas escapes rapidly and that in the course of a period of 30 to 40 minutes at the most the gas from a dosage of maximum utility is so diluted as to be practically ineffective. On the other hand, the table shows con- clusively that the experiments afford no justification for reducing the dosage on account of lengthening the exposure from 45 to 60 minutes or longer. Everything considered, the writer adopted the 40-minute period of exposure as probably affording the greatest benefit from a given amount of cyanid. As an aid in determining the rates of dosage which could be safely recommended for the various ratios of leakage surface to cubic con- tents, the experiments referred to in Table V were arranged in accord- ance with the ratio, and in each case the writer estimated the amount of potassium cyanid which it seemed evident would have been ample for the destruction of all the insects. The degree of success obtained with the amount of potassium cyanid actually used was taken mto consideration in estimating the amount needed. The data thus arranged, together with calculations of the rate, or number of cubic feet of space per ounce of potassium cyanid, are given in Table VII. DOSAGE REQUIREMENTS. TasBLeE VII.—Study of dosage rates. 45 Ratio of | Amount | Rate: Number cubic square feet ‘cyanid esti-| feet of space per in leakage | Amount of | Percent of| mated as ounce of cyanid. surface to | cyanid | white flies | necessary r cubic feet used. destroyed. for Estimated of successful Used. as contents. results. necessary. Ounces. Ounces 1:2.65 25 99. 2 27 171 159 1:2. 56 302 98. 4 34 174 157 1:2. 49 263 98.9 29 160 146 1:2. 38 303 98.6 33 160 144 1:2. 30 174 97 20 207 179 1:2. 29 25 97.6 28 127 108 1:2. 28 164 98. 6 19 148 128 132.17 124 99. 5 14 149 133 1:2. 09 243 99. 7 27 151 138 1:2. 09 284 99.6 | 30 130 124 1:2. 08 15 99.8 16 126 118 1:2. 01 174 98.8 20 189 | 163 1:1. 95 22 99. 5 24 154 141 1:1. 88 244 99. 5 27 130 118 1:1.88 20% 97.7 24 148 127 1:1. 83 134 99.8 15 154 | 138 1:1. 83 134 95. 7 17 146 122 1:1. 47 8s 97 11 152 | 118 From a study of the data in the Table VII the writer concluded that for a ratio of 1:1.5 the cyanid should be used at a rate very near to-1 ounce to 110 cubic feet of space. Owing to the fact that in all cases tented trees include less inclosed space than would a regular figure which for purposes of approximate calculations has been considered as equivalent, this rate would be higher for a reg- ularly shaped inclosure whose cubic contents could be definitely cal- culated. Probably 1 ounce to 100 cubic feet of space is nearer the actual rate which the experiments indicate is necessary with the ratio mentioned. This, however, is of little consequence in dealing with sheet tents, for only the comparative volumes and dosage rates for trees of different dimensions are required for practical purposes. Having decided upon the adoption of 1 ounce of potassium cyanid per 110 cubic feet of space with the ratio of 1:1.5, calculations were made for tents with different ratios up to 1:3.6. Professor Gossard reports” that 1 ounce to 170 cubic feet of space destroys all white fly pupe in an air-tight fumigatortum. Considering that this rate is approximately correct, an equivalent rate for the volume inclosed by a sheet tent covering a tree would be more than 170 cubic feet in the ideal form of inclosure upon which the calculations are based. Experiments numbered X.3 and X.4, however, show that a rate not less than 1 ounce for 126 cubic feet of space should be used when the ratiois 1:2. When the ratio is increased from 1:1.5 to 1: infinity? and the rate of dosage for this latter ratio is considered as 1 ounce a¥Fla. Exp. Sta. Bul. 67, p. 652. >It is evident that if the number of cubic feet of space were infinitely greater than the number of square feet of leakage surface, the rate of dosage required for an air- tight fumigatorium would be sufficient. 46 FUMIGATION FOR THE CITRUS WHITE FLY. for 170 cubic feet of space, all of the rates are more or less greater than those used in the experiments in which from 95 per cent to 99.9 per cent of the insects were killed. It is evident that the increase in number of cubic feet per ounce of potassium cyanid from 110 to 170 must be calculated at a rate which is in direct proportion to the percentage of increase in cubic contents. The method employed in these calculations is shown in Table VIII, which gives the figures with the ratios ranging from 1:1.0 up to 1:3.6. TasiLeE VIII.—RKates of dosage as affected by ratio of number of square feet in surface to the number of cubic feet in volume. Differ- ee | | Differ- | ees Percent | Number | ence be- | MerTease Per cent | Number | ence be- | 12¢rease ofin- | ofcubic | tween aR CaBIG ofin- | of cubic | tween Be ees | Ratio. | crease in| feet per | number feet per Ratio. | crease in| teet per | number feotepert cubiccon-| ounce /|cubicfeet arias cubic con-| ounce | cubic feet) Bais tents. | cyanid. |per ounce Cuanid tents. | cyanid. per ounce} C anid | anid 1708 pce a |r erud 1708 |no) caer 1S) Woe | Pees Pee 76.8 O32 iAlligee pees ae 1:2. 4 4.34 | 183.5 36.5 rd, ETE 10 86.1 83.9 9.3 1:2.5 4.16 135 35 1.5 ges 9. 09 93.7 76.3 7.6 1256 4 136. 4 33.6 1.4 PIES Sy 8. 33 100. 1 69.9 6.4 132.7 3.85 137.7 32.3 1.3 ae 7.69 105. 4 64.6 5.3 1:2.8 3.7 4138. 9 31.1 1.2 SE Sie 7.14 110 60 4.6 1:2.9 3.6 140 30 1.1 1:1.6 6. 66 114 56 4 1:3.0 3. 44 141 29 1. 03 sila y/ 6. 25 117.5 52. 5 Brie) (fealieghs al a 3.33 142 28 Sil 1:1.8 5. 88 120. 6 49.4 ah il 13:2) | 3. 26 142.9 27.1 91 1159 5. 55 123.3 46.7 Pit eS von 3. 12 143.8 26 85 1:2.0 5. 26 125.8 44.2 225 1:3.4 | 3. 03 144.5 25. 4 79 1% Al 5 128 2 2.2 123.5. | 2.94 145.3 24.7 75 129.9 4.76 130 40 2 1:356)0\|) 222,86 146 24 71 1:2.3 4. 54 131.8 38. 2 1.8 | | | | | In Table VIIT the number of cubic feet of space per ounce of potas- sium cyanid increases toward 170, representing the rate when the ratio is 1 to infinity, and the dosage increases in rate (= decrease in the number of cubic feet per ounce of potassium cyanid) as the units of cubic contents become infinitely small in number as compared with the units of square measure of leakage surface. Using the above rates as a basis, the doses for trees measuring from 10 to 76 feet over the top have been calculated. The dimensions of the tented trees and volumes of the inclosed spaces have been calculated in accordance with the formule given in the preceding pages. Table IX gives the original calculations, while in the appendix the recommended doses alone are given, in a form more convenient for practical use in the field. DOSAGE REQUIREMENTS. TaBLE I1X.—Recommended dosage, with 45-minute exposures. = Measurements of | Height Diameter Rate of of regular of regular Ratio of | dosage, Pope tees. Area of | figure figure leakage | number Fee leakage ‘ with | with | Volume. | surface cubic feet |°" (0m ay 4 surface. | foregoing foregoing to cubic |space per 5 Distance uae measure- measure- contents.) ounce | ™ended. OWES ONES, | ments. ments. eyanid Feet. Feet. | Sq. feet. Feet. Feet. Cu. feet. Ounces. 10 15 78 3.6 4.7 48 TOs Gls eer sy 1.0 20 78 3.2 6.4 69 TSOP SOI nl erreryectas. 1.0 12 15 113 4.6 4.8 65 IESG eon laser cteerc ee 2.0 20 113 4.2 6.4 101 Ue On89Ol | PSee ee ee 2.0 14 15 154 5.6 4.8 85 EONS. eee ececer 20) 20 154 Sn2) 6.4 133 ORS Owls ese sere 205 25 154 4.7 8.0 171 ileiieibl 76 2.5 16 20 201 6.2 6.4 165 1:0. 82 62 3.0 25 201 5.7 8.0 221 IPI aI) 88 3.0 30 201 5.3 9.5 276 BUSBY / 100 3.0 18 20 254 ee? 6.4 197 1:0. 77 56 4.0 25 254 6.7 8.0, 271 1:1.06 74 4.0 30 254 6.3 9.5 347 1:1. 36 102 4.0 35 254 5.8 ial 406 1:1. 60 114 4.0 20 | 20 314 8.2 6.4 229 1:0. 73 54 4.2 25 314 deuth 8.0 321 132502 76 4.2 30 314 7.3 9.5 418 Ted 33 100 4.2 35 314 6.8 ile at 500 1:1.59 112 4.4 22 25 380 8.7 8.0 372 1:0. 97 75 4.9 30 380 8.3 9.5 489 128 96 Sal 35 380 7.8 ileal 594 1:1. 56 lit 6.3 40 380 7.4 LOT 670 1:1. 78 118 5.9 24 30 452 9.3 9.5 550 Wei leaal 93 5.9 35 452 8.8 aii eat: 688 NeeGy 110 6.2 40 452 8.4 IPA TE 797 Tei 117 6.8 45 452 7.9 14.3 927 1:2. 05 128 2 26 30 531 10.3 9.5 621 ili a7 89 7.0 35) | 531 9.8 ili il EP | ey 107 75S} 40 | 531 9.4 12.7 924 1:1. 74 118 7.8 45 531 8.9 14.3 1,046 GNA YS 124 8.4 28 30 615 11.3 9.5 692 Te deal2) 86 8.1 35 615 10.8 ible 876 1:1. 42 105 8.3 40 615 10. 4 PAYS 1,051 1:1. 70 117 8.9 45 615 9.9 14.3 1, 206 1:1. 96 124 9.7 30 é 30 707 12.3 9.5 763 1:1.08 80 | 9.0 35 707 11.8 itil al 70 Me By! 100 9.7 40 707 11.4 IPE TA 1,178 1:1. 66 114 10.3 45 707 10.9 14.3 1, 364 1:1. 93 123 i ea 32 30 804 13:3 9.5 834 1:15.03 79 10.5 35 804 12.8 ike ih 1, 067 1:1. 32 100 10.7 40 804 12.4 IPA TE 1, 305 1:1. 62 114 11.4 45 804 11.9 14.3 Loz 1:1. 90 123 12.4 50 804 15 15.9 1,750 WERE AI / 129 13.6 34 30 908 14.3 9.5 906 1:1. 00 76 4.9 35 908 13.8 11.1 1,161 1:1. 28 95 12.0 40 908 13.4 1a 1, 433 1:1. 58 112 12.8 45 908 12.9 14.3 1, 684 1:1. 85 121 13.9 50 908 12.5 15.9 1,951 1:2. 14 128 NEP. 36 35 1,018 14.8 ie 1, 265 1:1. 24 95 13.3 40 1,018 14.4 WEE 1,560 Peles3 110 14.2 45 1,018 13.9 14.3 1, 844 1:1. 81 120 115}583 50 1,018 13.4 15.9 2,149 Galil 128 16.7 55 1,018 13.0 15 2, 428 1:2. 38 132 18. 4 38 35 1, 134 15.8 Titel 1, 360 1:1. 20 93 14.6 40 1,134 15.4 12.7 1, 688 1:1. 48 107 Wont 45 1,134 14.9 14.3 2,005 P56 118 17.0 50 1, 134 14.4 15.9 2,348 1:2. 07 126 18.7 55 1,134 14.0 We5 2, 668 1:2. 35 132 20. 2 40 40 1, 256 16. 4 Pav é 1,816 1:1. 44 106 17.0 45 1, 256 15.9 14.3 2,165 Eo 117 18.5 50 1, 256 15.4 15.9 2,546 12502 125 20.3 55 1, 256 15.0 17.5 2,909 Le2roL 131 22.2 60 1, 256 14.5 19.1 3, 256 1:2. 59 135 24.1 42 40 1, 385 17.4 AP 1, 943 1:1. 40 105 18.5 45 1, 385 16.9 » 14.3 2, 326 1:1. 68 115 | 20. 2 50 1, 385 16. 4 15.9 2,745 1:1. 98 124 22.1 55 1, 385 16.0 Uf fe'5) 3,149 UPAR Y | 130 24.2 60 1, 385 15.5 19.1 3,542 Us2555 135 26. 2 44 45 1,520 17.9 14.3 | 2,486 1:1. 63 114 21.8 50 1,520 17.4 15.9 2,944 1:1. 93 123 23.9 55 | 1, 520 17.0 Lied 3, 389 IP ROA 130 26.1 60 1,520 16.5 197A By lertsseaip Ibe ee 135 28.3 65 1,520 16.1 20.7 4, 254 1:2. 80 138 30.8 49918—Bull. 76—08——4 48 FUMIGATION FOR THE CITRUS WHITE FLY. Taste IX.—Recommended dosage, with 45-minute exposures—Continued. Measurements of Height | Diameter | Rate of tented trees. of regular of regular | Ratio of dosage, | , t Area of | figure | figure leakage | number etal 2 leakage ; with : with | Volume. surface cubic feet, en: ; + 4m. | Surface. | foregoing) foregoing 0 cubic space per 5 mistanca:) ets measure-| measure- conteriiam-ataicens| eadad. ver. © ments. | ments. eyanid. Feet. Feet. Sq. feet. Feet. Feet. | Cu.feet. | Ounces 46 50 1, 662 18. 4 5), 9) 3, 183 1:1. 88 121 25.9 : 55 1, 662 17.9 17.5 3, 630 1:2.18 129 28.1 60 1, 662 17.5 19.1 4,115 1:2. 47 134 30. 7 65 1, 662 17.0 20.7 4, 591 1:2. 76 138 33. 2 70 1, 662 16.6 22.3 5, 038 1:3. 03 141 35.7 48 50 1, 810 19. 4 15.9 3, 332 1:1. 84 121 27.5 55 1,810 18.9 17.5 3, 870 1:2.13 128 30. 2 60 1,810 18.5 19.1 4, 401 1:2. 43 133 33. 1 65 1,810 18. 0 20. 7 4,927 1:2..72 137 35. 9 70 1,810 17.6 22.3 5, 428 1:3. 00 141 38.5 50 55 1,964 19.9 17.5 4,111 1:2. 09 127 32.4 60 1, 964 19.5 19.1 4, 687 1:2. 38 132 35.5 65 1,964 19.0 20.7 5, 264 1:2. 63 136 38. 7 70 1, 964 18. 6 22.3 5, 828 1:2. 96 140 41.6 75 1, 964 18.2 23.9 6,358 1:3. 24 142 44.7 52 55 2,123 20. 9 17.5 4, 351 1:2. 05 126 34.5 60 2,123 20.5 19.1 4,974 1:2. 34 132 37.6 65 2, 123 20. 0 20. 7 5, 600 1:2. 63 136 41.1 70 2,123 19.6 22.3 6, 217 1:2. 92 140 44.4 75 2,123 19.2 23.9 6, 805 1:3. 20 142 47.9, 54 55 2, 289 21.9 17.5 4, 591 1:2. 00 125 36. 7 60 2, 289 21.5 19.1 5, 261 1:2. 30 131 40.1 65 2, 289 21.0 20. 7 5, 936 1:2. 60 136 43.6 70 2, 289 20. 6 22.3 6, 607 1:2. 88 138 47.8 75 2, 289 20. 2 23.9 7, 252 1:3. 16 142 byloal 56 60 2, 462 22.5 19.1 5, 547 1:2. 25 130 42.6 65 2, 462 22.0 20.7 6, 273 1:2. 54 135 46.4 70 2, 462 21.6 22.3 6, 997 1:2. 84 138 50.7 7 2, 462 21.2 23.9 7, 700 1:3. 12 142 54.2 80 2, 462 20. 8 25.5 8, 459 1:3. 43 144 58. 7 58 60 2, 641 23.5 19. 1 5, 834 1:2. 20 130 44.8 65 2, 641 23.0 20. 7 6, 609 1:2. 50 135 * 48.8 70 2, 641 22.6 22.3 7, 396 1:2. 80 138 53.6 75 2, 641 22.2 23.9 8,147 | 1:3.09 141 OETE 80 2, 641 21.8 25.5 8, 971 1:3.39 144 62. 3 60 60 2, 826 24.5 19.1 6, 120 1:2. 16 128 47.8 65 2, 826 24.0 20. 7 6, 945 1:2. 45 134 51.8 70 2, 826 23.6 22.3 7,786 1:2. 75 138 56. 4 75 2, 826 23. 2 23.9 8, 595 1:3. 04 141 60.9 80 2, 826 22.8 25.5 9, 483 1:3. 35 144 65. 4 62 60 3,018 25.5 19.1 6, 406 TEDL 128 50.0 65 3,018 25.0 20.7 7, 282 1:2. 41 133 54.7 70 3,018 24.6 22.3 8, 176 ie yt 137 59.6 75 3, 018 24. 2 23.9 9, 042 1:3. 00 141 64. 1 80 3,018 23.8 25.5 9, 995 1:3. 31 143 69. 2 64 60 3,215 26. 5 19.1 6, 693 1:2. 08 126 53.1 65 3, 215 26. 0 20. 7 7, 618 PAC Yi 132 57.7 70 3,215 25.6 22.3 8, 565 1:2. 66 136 63.0 75 3, 215 25: 2 23.9 9, 489 1:2.95 140 67.7 80 3, 215 24.8 25.5 10, 507 1:3. 26 143 73. 4 66 60 3,419 27.5, 19.1 6,979 1:2. 04 126 55. 4 65 3, 419 27.0 20. 7 7, 955 1:2. 33 131 60. 7 7 3,419 26.6 22.3 8,955 1:2. 61 134 66.8 75 3, 419 26. 2 23.9 9, 937 1:2.90 140 70.9 80 3, 419 25.8 25.5 11,019 1:23.22 142 77.6 85 3,419 25.3 Dail 11, 939 1:3. 49 144 82.9 68 60 3, 630 28. 5 19. 1 7, 266 1:2. 00 125 58. 1 65 3, 630 28. 0 20.27 8, 290 1:2. 28 130 63.7 7 3, 630 27.6 22.3 9, 345 V2 2057. 135 69. 2 75 3, 630 27.2 23.9 10, 384 1:2. 86 139 74.6 80 3, 630 26.8 25.5 11, 531 WER wAli/ 142 81.1 : 85 3, 630 26. 3 PA al 12,513 1:3. 45 144 87.5 70 60 3, 848 29.5 ° 19.1 7, 552 1:1. 96 123 61.4 65 3, 848 29. 0 20. 7 8, 627 1:2. 24 130 66. 3 7 3, 848 28.6 22.3 9, 734 1:2. 53 135 72.1 75 3, 848 28.2 23.9 10, 8381 1:2. 81 138 78.5 80 3, 848 27.8 25. 5 12, 043 1:3. 10 142 84.8 85 3, 848 27.3 Die 13, 088 1:3. 40 144 90.9 72 60 4, 069 30.5 19. 1 7, 838 1:1. 92 123 63.7 65 4, 069 30. 0 20. 7 8, 963 1:2. 20 130 68. 9 70 4, 069 29.6 22.3 10, 124 1:2. 49 134 75.5 75 4, 069 29.2 23.9 11, 278 EP ATIC 137 82.3 80 4,069 28.8 | 25.5 12, 555 1:3. 08 141 89.0 85 4, 069 28.3 | 27.0 13, 662 1:3. 35 144 94.8 90 4, 069 27.8 | 28.6 14, 829 1:3. 64 146 101.5 if i a ea DOSAGE REQUIREMENTS. 49 TasLe IX.—Recommended dosage, with 45-minute exposures—Continued. Rate of Measurements of Height |Diameter é tented trees. of regular|of regular Ratio of | dosage, | 4 ount Area of | figure figure leakage | number i GaG lela ; with with | Volume. | surface |cubicteet °° /V 0" : . _ | surface. | foregoing) foregoing to cubic | space per | D uae eae measure-| measure- contents.| ounce - _ mended. Mh : ments. | ments. cyanid. Feet. Feet. Sq. feet Feet Feet. Cu. feet. Ounces. 74 60 4,299 31.5 19S 8,125 1:1.89 121 67.1 65 4, 299 31.0 20.7 9, 300 1:2. 18 129 71.3 70 4, 299 30. 6 22.3 10, 513 1:2. 45 134 78.4 75 4, 299 30. 2 23.9 11, 726 1:2. 72 137 85. 6 80 4, 299 29.8 25.5 13, 067 1:3. 03 141 92.7 85 4, 299 29.3 27.0 14, 237 1:3. 31 143 99.5 90 4, 299 28. 8 28. 6 15, 471 1:3. 60 146 106.0 76 60 4, 534 32.5 19. 1 8, 411 1:1. 85 120 70.0 65 4, 534 32.0 20. 7 9, 635 1:2: 12 128 75.2 70 |, 4,534 31.6 22.3 10, 903 1:2. 40 133 82.0 75 4, 534 31.2 23.9 12,173 1:2. 66 136 89. 4 80 4, 534 30.8 25.5 13,579 1:2. 99 140 97.0 85 4,534 30. 3 27.0 14, 812 1:3. 26 143 103.5 90 4,534 29. 8 28.6 16,113 1 3n00 145 111.1 2 i EXPERIMENTS WITH BELL OR HOOP TENT. The bell or hoop tent used in these experiments was one constructed of 64-ounce drill of the brand most commonly used in California. Owing to the form of the tent the leakage surface is far less in propor- tion to the volume than in the sheet tent. The data concerning the experiments and the recommended dosage based upon the experi- ments with the sheet tent are given in Table X. TABLE X.—Experiments in fumigation with bell-shaped tent of 64-ounce drill. Measurements of | | Amount of Ex. tented trees. Number of cyanid eri- Amountof; white |Percentof| recom- Le eel ee ine cyanid | flies un- | white flies | mended in No Distance Cirecumfer- used. der obser- killed. table for 3 over. ence. vation. 45 minutes’ exposure. Feet. Feet. Ounces. ; Ounces. 30.3 28% 35 4 555 88 9 40.5 27 38 4 138 88 83 40.7 334 38 83 132 80 13 40.16 20 23 + 300 100 4} 40.17 253 27 7 476 100 7 40.19 24 20 4 209 100 53 40.22 20 22 2 162 97.4 43 45.2 28 29 7 427 100 84 45.11 26 313 43 284 100 73 45.14 31 35 102 289 100 104 45.16 274 29 63 431 100 83 45.18 27 345 4 595 100 8 45.29 293 30 6 530 100 gh 45.31 23 24 3t 376 98.7 6 50.3 244 313 4 128 97.6 7 50.4 343 37 84 990 100 14 60.8 26 31 4 42 85. 7 74 xe 33 35 11 200 100 123 In these experiments a dosage sufficient to destroy all pupx was used in eleven instances. The total amount of cyanid used in the eleven experiments was 78? ounces, whereas the doses recommended in the tables, based upon the experiments with the sheet tents of 8-ounce duck, together amounted to 96 ounces. The average of the amounts used in the eleven tests was 7.2 as against 8.7 recommended 50 FUMIGATION FOR THE CITRUS WHITE FLY. in the tables. It is evident from the results summarized in the fore- going table that prolongation of the period of exposure beyond 40 minutes produces no noticeable increase in effectiveness. It is also evident that the dosage recommended for use with sheet tents of a good quality of 8-ounce duck is ample for bell tents of a good quality of 64-ounce drill. The smaller amount of leakage surface with bell tents as compared with sheet tents may be entirely responsible for the apparently wide margin between the recommended dosage and the dosage actually required for efficiency, but it seems safe to conclude that the 64-ounce drill used in the bell tent held the gas approxi- mately as well as the 8-ounce duck, the difference in leakage surface considered. MISCELLANEOUS EXPERIMENTS AND OBSERVATIONS. APPEARANCE OF LARVZ AND PUP# OF THE WHITE FLY WHEN DE- STROYED BY FUMIGATION. The opportunities for studying the efficiency of the gas against citrus pests are far superior with the white fly as compared with the true scale insects. While it requires considerable skill in the examinations, the vital conditions of the larve and pupe, both before and after treatment, can be recognized with practical cer- tainty without removing the specimens from the leaves. When in a normal condition the insects in the stages mentioned appear green, owing to their translucence, and paired yellowish spots, due to inter- nal organs, are sometimes visible in the abdominal region. As the pupa reaches maturity the reddish eyes of the adult become conspicuous and the location of the developing adult wings is indicated by whitish patches on either side of the body. When destroyed by fumigation with hydrocyanic-acid gas the larve and pupz usually turn more or less brownish in the course of a few days. This brownish discolora- tion is most pronounced along the middle of the body. Frequently, however, two or three weeks may elapse before they can be positively determined as dead. In the first examinations made by the author, pupx on fumigated trees were classed as alive, doubtful, and dead. It was afterwards determined that in practically every case those classed as doubtful were in reality dead. Examinations under a compound microscope were found to be of some assistance at times, but on the whole unsatisfactory. In such cases movements of the internal organs furnish positive proof that the insect is alive, but when these movements can not be detected there may still be doubt concerning the condition of the specimen unless granulation or dis- coloration of the body contents is evident. The most satisfactory method of observing the results of fumigation is to examine the insects with a hand lens of 1 or 14 inch focal distance without dis- APPEARANCE OF LARVH AND PUPH WHEN DESTROYED. 51 turbing the insect or detaching the leaf from the tree. String tags attached to leaves upon which are specimens classed as doubtful will enable examinations of such specimens from time to time until their condition is positively determined. A careful examination of normal specimens and direct comparisons of these with those on leaves of fumigated trees will assist in the ready identification of the dead insects. DENSITY OF THE GAS AT VARIOUS HEIGHTS ABOVE THE GROUND. It is natural to presume that owing to the fact that hydrocyanic- acid gas is lighter than air, its density during the process of fumiga- tion is greater toward the top of the tree. In four of the nine obser- vations on the comparative effect of the gas at different heights above ground the results of this variation in density are not evident. In the other five observations the results are quite striking. In the six experiments in which observations were made 10 feet or more from the ground, the average percentage of insects killed up to 6 feet above the ground was 64, while from 10 to 18 feet above ground the average percentage killed was 71. The data concerning the effectiveness of the gas at various distances from the ground is sum- marized in Table XT. Taste XI.—E ficiency of gas as affected by height above ground. a = = - Ex- : Number of Ex- - tance | Number of peri- Distance white fly | Percent peri- Distance white fly | Percent ment Ps oa pupe ex- killed. ment ee pupe ex- killed. No. Br0 amined. No. SUID EG amined. Feet Feet 30. 4 46 427 89 30.1 46 | 74 21 14-15 244 98. 3 12-14 909 36 i8 120 100 40.3 |. 46 | 822 80 20.1 4-6 687 91.9 12-14 | 445 90. 8 12-14 1, 000 90.8 30.3 2 396 92.8 20.7 453 222 77 = 7a 159 78 10 306 60 40.7 PA il 93 80.6 40.12 2 112 64 46 | 139 79.2 31-5 728 98. 4 46 541 26. 4 14-16 136 50 The results show that when examining for the results of fumigation, the most significant effects are those within a few feet of the ground. The observations concerning the results of the experiments upon which the recommendations in this bulletin are based were made in all cases within 7 feet of the ground, and included examinations of insects on leaves closest to the ground in all cases. EFFECT OF FUMIGATION ON THE TREES. During the months of December, January, and February, until the appearance of the new spring growth, fumigation for the white fly with the dosage herein recommended will rarely occasion appreciable 52 FUMIGATION FOR THE CITRUS WHITE FLY. injury to orange trees and apparently never to tangerine and grape- fruit trees. The liability of injuring trees through the emptying of the contents of the jars after fumigation close to or upon the base of the trees will be referred to under the subject of precautions. The injury to orange trees from the gas itself has never in the writer’s experience been sufficient to offset the benefits of destroying the white fly and scale insect pests. Nevertheless the subject is one of considerable importance. The experiments conducted in January and February, 1907, demonstrated the practicability of destroying the white fly with hydrocyanic-acid gas without injury to citrus trees. The fumigation of nearly 4,000 trees in the winter of 1907-8 has greatly extended our knowledge of the effect of fumigation upon the trees, but there remain several unsolved problems in this connection which it is hoped will be elucidated by future experience. The work of fumigating a grove should be completed if possible before the new growth appears in the spring. Under certain temperature conditions successful fumigations may occasion no injury to new growth, but there is danger of destroying the first spring shoots which normally produce the greater part of the blooms. When affected by the gas new shoots wilt and turn dark, appearing as though affected by frost. Under certain conditions there is more or less shedding of the old leaves following fumigation. The loss of 10 or 15 per cent of the old foliage can not be considered an injury, inasmuch as even more than this proportion is usually shed during the winter or in the spring. _ In fact, it has been demonstrated by experiments conducted by Mr. Yothers and the writer in February, 1908, that the leaves shed by fumigation when the percentage of the whole does not exceed 15 per cent are among the leaves which would normally drop in the course of a few weeks. In the experiments with the sheet tent of 8-ounce duck summarized in Table IV, the most extensive shedding occurred in experiments 40.14. In this it was estimated that about 50 per cent of the leaves were shed. The tree was fumigated on January 29, beginning at 4.07 p. m., about one-half hour before sunset. No shedding was observed until the morning of February 2, when it was estimated that from 15 to 20 per cent of the leaves dropped. On February 4 it was estimated that 50 per cent of the leaves had fallen, after which date the amount of the shedding was inappreciable. The winged petioles of the leaves remained attached to the tree in most cases and the fallen leaf blades showed distinct brownish areas due to burning by the gas. The tree consisted of five stems growing from the roots of a tree frozen to the ground in 1895. One of these stems was affected by foot rot or mal-di-gomma, and the defoliation of this was nearly complete, materially increasing the percentage of shedding from the EFFECT OF FUMIGATION ON TREES. De tree asa whole. This tree was observed in full bloom on April 4, and ten months after the treatment appeared as vigorous as any tree in the grove and bore more than the average crop of fruit. In the experiments with the bell tent of 64-ounce drill, shedding of conse- quence occurred only in the case of experiment X.2. This tree was fumigated on January 29, beginning at 4.41 and ending at 7.50 p. m. It was estimated that the shedding amounted to about 30 per cent in this case. In experiment 45.36 the exposure began at 3.07 p. m. in bright sun- light with the temperature at 75° F. The tent had been in position for thirty minutes preceding the introduction of the chemicals, and the inside temperature was 44° higher at the beginning than the out- side temperature mentioned above. The tent was in direct sunlight during the entire forty-five minutes of exposure, and doubtless the inside temperature rose to 82° or 83°. As shown in Table IV, the amount of potassium cyanid used was 44 ounces less than the amount recommended in the table given in the appendix. The leaves were curled as a result of drought at the time of the fumiga- tion and no shedding of leaves or injury of any kind to the tree could be detected by subsequent examinations. An overdose is indicated by the scorching of the foliage on entire twigs. This is more likely to occur near the tops of the trees. In such cases several twigs, each 6 inches or a foot in length, may be entirely killed, the leaves, instead of dropping within a few days, turning brown and remaining attached to the dead twig. This is not necessarily accompanied by excessive shedding of the foliage. The physiological condition of the trees seems to have a marked effect on their lability to shed foliage. Vigorous trees are less susceptible than weak, poorly nourished ones. Trees in the same grove but growing under different conditions as regards the nature of the soil and the amount of soil moisture show differences in this respect. In most groves trees will not shed leaves excessively if the dosage is increased 25 per cent above the recommended amounts. Frequently there will be no shedding at all following such a course. In other citrus groves the recommended dose is as large as the trees will stand without shedding to an injurious extent. The likelihood of damaging citrus fruits by fumigation is such that it is strongly advisable to pick the crop before starting to fumigate. . In January, 1908, many seedling trees were fumigated which held from five to eight boxes of oranges per tree, without any injury whatever following the treatment. In other cases a small percent- age of the fruit developed sunken areas or “‘pits’”’ which turned dark and ruined the affected fruit for shipping purposes. Fumigation, in midwinter, using the dosage table given in the appendix, does not seem to affect the fruit of Hart’s Lake, Lamb’s Summer, or Valencia 54 FUMIGATION FOR THE CITRUS WHITE FLY. varieties. Grapefruits are slightly susceptible to this injury, while tangerines appear not at all susceptible, although considerable shed- ding of the fruit occurred in one instance when the recommended dosage was doubled. SUGGESTIONS FOR THE FUMIGATION OF SMALL TREES. IN THE GROVE. In discussing the style of fumigating tents desirable for use against the white fly the author has referred to the advantages of the use of box covers for small trees. In many cases complete defoliation of the trees during the winter months would be the best method of checking the pest, but fumigation is preferable under most circum- stances. The dosage with box covers will depend upon the tightness of the cloth used. It has been recommended that the cloth be made as nearly air-tight as possible by means of paint, or that air-tight oilcloth be used. The rate of dosage can be readily determined by means of a series of tests, beginning with 1 ounce of potassium cyanid for each 170 cubic feet of space (0.00588 ounce per cubic foot) and decreasing the number of cubic feet per ounce 10 feet for each experiment until the results are satisfactory and uniform. No experiments have thus far been conducted by the author along these lines, but it is expected that in the course of the investigations of the white fly now under way in Florida this phase of white fly con- trol will be given consideration. IN THE NURSERY. Several square yards, including many trees, can be covered in the nursery by a single tent. If the cloth is unpainted, the dosage for a first trial can be calculated by first determining the ratio of the leak- age surface to the cubic contents and referrmg to Table VIII in this bulletin, where the recommended rate of dosage will be found for the various ratios. The results of the preliminary tests should be care- fully observed before fumigating on a large scale, in order that the rate of dosage may be adjusted to suit the tightness of the cloth used as a cover. NURSERY STOCK FOR SHIPMENT. Prof. H. A. Gossard, formerly of the Florida experiment station, has determined that in an air-tight fumigatorium 1 ounce of potas- sium cyanid for each 170 cubic feet of space“ is sufficient to destroy all «One gram to 6 cubic feet of space,’’ he reports, ‘‘seemed sufficient to kill every- thing, but to make the dose more certain 1 gram to 5} cubic feet was adopted as the standard dose and has been repeatedly tried, always giving the uniform result of kill- ing all larvee (pup) and adults.’’-—Bul. 67, Fla. Exp. Sta., p. 652. One aunce is equal to 28.35 grams, from which it is calculated that 1 gram for 6 cubic feet of space is equal to 1 ounce for 170 cubic feet and 1 gram for 5} cubic feet is equal to 1 ounce for 163 cubic feet. NURSERY STOCK FOR SHIPMENT, 55 larve and pupz of the white fly. To destroy the eggs, however, he found that a larger dose was necessary. The author fully concurs with Professor Gossard in his recommendation to defoliate completely all white fly infested nursery stock before shipping, and, as an extra precaution, to fumigate. The almost invariable experience of Florida nurserymen, however, shows that citrus trees should not be fumigated with roots bare. The fumigation is far less necessary than when the insects concerned are true scale insects and are attached to the stems. White flies have never been known to reach maturity except on the leaves, although eggs and crawling larve may occasionally be found on young growing shoots. It is safe to presume that there are no unhatched eggs of the white fly on anything other than leaves and young succulent growth of stems. When these are completely re- moved there need be no fear that the pest will be carried by means of the trees. The entire leaves, including the winged leaf petioles, must be removed, and when large shipments are concerned careful attention must be given to this. A greater danger than the trees themselves is found in the packing. This, as Professor Gossard points out, might be a possible source of danger if infested citrus leaves were allowed to get into the moss or other material used in packing. The danger is, of course, slight, but should nevertheless be borne in mind by shippers and buyers of nursery stock. PRECAUTIONS. As is customary in publications on entomology in which the use of potassium cyanid is recommended in combating insect pests, atten- tion is directed to the extremely poisonous nature of this substance. There are on record no fatalities due to the use of potassium cyanid as an insecticide against orchard pests, but this is because the danger from careless use was well known and simple precautions were observed. In weighing the doses it is recommended that the hands be protected by leather gloves, and after starting the generation of the gas the operator should avoid breathing until he is outside in the open air. A slight choking sensation experienced when standing close to the tents during the fumigation acts as a danger signal, and one should not persist in remaining where the gas is dense enough to produce this result. The acid should always be handled with great care. In addition to precautions necessary for the safety of the operators, care should be taken to avoid the scattering of small parti- cles of the cyanid where fowls or other animals might become poisoned. As this substance is readily soluble in water and is deliquescent, or capable of liquefying through the absorption of moisture from the air, small particles accidentally dropped soon disappear. 56 FUMIGATION FOR THE CITRUS WHITE FLY. Other precautions which it seems desirable to emphasize at this time concern the avoidance of damage to the tents and trees. Tents should never be dragged over the ground where the residue of the jars has been poured out on the surface or where the material has boiled over during the generation of the gas. The safest rule is to avoid entirely the dragging of tents across sections of the grove which have been recently fumigated. The residue or contents of the jars after fumigating is very destructive to citrus trees if emptied against the base of the trees. When emptied 3 feet or more from the base of the trees there seems to be no danger whatever unless roots are exposed, but to avoid all risk it is recommended that the practice be adopted of burying the residue halfway between the rows, as described under the subject of methods of procedure. Tents should not be left during the day covering trees which are to be fumigated at night, for the inside temperature is quite likely to be raised to a point where the gas will cause excessive shedding of the foliage. EXPENSE OF FUMIGATION. FOR EQUIPMENT. The cost of the equipment, aside from the fumigating tents, is of. little importance. In procuring a set of tents one may either pur- chase the material and arrange for the construction to be done by a tentmaker according to directions, or the maker may provide the material and furnish the tents according to specifications at regular prices. It will be found advantageous to obtain quotations from sev- eral tentmakers before placing an order. To give an idea of the usual cost of fumigating tents in California, the following schedule of prices recently quoted by a leading maker of fumigating tents in that State is given: TaBLE XII.—Schedule of prices for sheet and bell fumigating tents. Sheet tents, 8-ounce || Bell tents, 63-ounce duck. drill. Diameter. Price. Dimensions. Price. Feet. Feet. 17 $6.12 6by 7 $2. 66 24 12.24 8by 9 4.55 30 18.90 6 by 12 5.72 36 27.00 || 9% by 11 6. 76 41 34. 20 103 by 14 9.10 43 41.40 12 by 15 13.00 45 43.74 48 47.70 52 59. 40 55 65.70 64 86. 40 COST OF EQUIPMENT. 57 Pa The cost of the sheet tents would be considerably reduced by the use of one or two widths of 64-ounce drill, sewed around the margin as a skirt, as described under the subject of construction of fumigat- ing tents. The difference between the cost of tent materials in Cali- fornia and in eastern citrus-growing States, owing to the greater distance of the former from the factories, should result in a reduction of from 2 to 5 per cent in the cost of an outfit at any point in the GulfStates. In Florida theseason for fumigating against the white fly extends over fromseven to ten weeks. During this time a fumigating tent, used between thirty-five and fifty days on an average of eight hours per day with forty-five minute exposures, would be used to cover between 280 and 400 trees. | en hon. een oe leo DEL esl ee sae ae eae SecA Re ees | ee ees re 901 F101 | 86 16 | ¥6 i0 LEE oe eben (ota eel in | pee ae IIR OI 09 8 AM Lie al 1S 168 - u : 1G ia 4 ey a iS Loma : nn NN REIS | es ey | NA ir 2c ae Rema (Fagen pee panther ae ePaenl Soa Tel pa eminence (es Ship mee alba Soe en Aun (ede Sales Geel ohonac|eesmv [Sema Dc cegscllasccalloe Sbeelle seta eck eral PS Zeee 8 RIS ea A el aes Bt ee eke LN ae eee [eo el eel eae eee errr Pentre e. se) Lamp eA : ts q : ist fcc a Lela Rae ese (Oy esos : Suite Ohl idameo gallina lore eee Vissi tats hcectetocs = 5aoaee) ame Gp. \ertecs|ess=s|ecceec|eon as Sb sea eae ee aera a Ol | cat i Tr |¥0T a SS (TES Gi eee | cag eis Ss ! ee a 8 £Q 8 ee ee ieee sas Wes a L fis, oo eee ; Oe ee ee 9 9 OM kGnes lies a ae aca CG GR ee Zola, arg i ea iP iP fr 86teC&\ S | eee lie, eae 7 F 7 P 2 30 SURES ESBS Geiss aca 8h Bes apallsoneee peat [pres [*eore hm pears Perse base bat re igen | sch os g Soe alate Saba | saad to © al es ee & aaameael ea as | a nee aoe || ede | ee ESS CSI EO ea Pes Ceacwer al eaten Maeemales ace 4% ite i Ey Se ese) ees oe Z z Rte ees fico alee ane | eco emcee | eens SSoaad peButn [bosses [yared|ppopce Banged oelesel Beceud sarteea| bstcosallagasar pobdlss|nmari<| anc pone le 7 | | | : sil || ——_— | —— = = — | —— —=| |= = = = — = = = = == = | = = — = — — = = — — 06 | #28 | GSI | eee Ome ee 2 GZ cela | Oe ELO | WSO Mae ¢C9) NOON eto CO mee eCCin OG sles SPann OP ee SEan tl OG | SGe | OGuyeccen gOr = - = . = “19AO DDUBYISTCT “90U0IOT UMA (ee) : ' ‘ to) ‘9ad) paqua) ayy fo “qaaf ur ‘aouasafunadno ay) PUD sad0 BoUDIsYp ay? Wodn pasng ‘Gurywbrunf sof (pruvfia wnissvjod fo ‘savuno ur ‘fjpjyunnh) abosop ladoug INDEX. Ash, prickly. (See Xanthoxylum clava-herculis.) ALMospherne humudity as atlectine fumigation +2 .5-..22..--2--.--:-.+-cs25: 12-14 Banana shrub. (See Magnolia fuscatum. ) Bay, sweet. (See Magnolia virginiana.) Box tents or covers for fumigating small trees in grove...............---.-.-- 54 Cactus, prickly pear. (See Opuntia sp.) Cape jessamine. (See Gardenia jasminoides. ) Sirowiren sor UimipaiOn COStas.« ca) o2-.45- Scare sce eie< 22.68 S504 me Pane 58 handling, and protection from moisture............. 25 WLOPONLOUNOle waALeranduacid sss soe ee nee 25-27 | ONDTETH NYO [Th 36 A ete el ed 25 Cherry laurel. (See Prunus laurocerasus.) Chinaberry. (See Melia azedarach and M. a. umbraculiformis.) Chrysomphalus ficus, losses prevented by fumigation.................--.-.-.- 61 Gienepiogd. plantsrerwititedivic oo) ool rN ee cent ee a 10 IMSCeheMIStOnynOl PUMUSALION =. Ne 2 ate ae ea) ec oe ene es =e 7-8 PMO MOL On AOGMeplAmiLOr Wilbert yj so 5 soos Bh cee nl So ts Ok Sew cre ss 10 white fly. (See White fly.) Concerredsaction javorne fumipation.o2 045.2242. eso. eo veo ase s ooo Sao 9 Conditions favoring or necessary to good results in fumigation ...............- 9-14 Control. natural: of-white fly, versus fumigation. .)2_.02..-.2.. 2.022.226. s5<: 63-65 Cosoliumucation compared withepraying ... 22.22.22... . 2.52022 b ee lke 62-63 Cubic contents of tented tree, methods of computation in fumigation.........- 39-40 Cyanid of potash. (See Potassium cyanid. ) Derricks. (See Uprights. ) Wiemeantamec fun HNN OAIIOM 2. 42h et are open oe oka tee a bent coe es dee ee 12-14 Diagram of grove as guide in fumigation...... SEE Moet SAL aces 23-24. 38 Dimensions of tented tree, methods of computation........................... 39-40 Diospyros kaki, food plant of white fly....-. pesos eve iy NL ie Aor ae a 10 inguin, Joa plamtiotawhitetlvs=s—052 26 fase. She ae Se sa 10 Dosage requirements in fumigation against white fly......................-.- 40-50 tablettortumuiucationsapamst white fly. 5.2222.) c2-eehessece ess ---- 66-68 Peonomys Olireatment Dy AUMIPaAhON. 2 926 cet 52 0cen Ge bec Sedat et ese nee 59-63 Bamupinemitortuniigaitone v.22). 528 ie a sae oleae ress. 14-24, 56-58 ES SETUSLOVEI TONG GTI EUG Ba eae ee 56-58 Ficus. (See Fig.) CivissinideOoGep lamp Olswbite tH yacse ee 0 sae sc cars e ses oe ede eee ee: 10 niererepotied ood plamtoLwhibe ty). 0- 0.502.222 ee ee ee eee et a 10 DOG) CLEDUS Gl WAS Uy et hoon oe ee Se ee ae 10 Food plants, other than citrus, of white fly, absence or elimination favoring SOUUDa) Oh? TERT Oe gee a ae Ee ee ee rr eae ne 9-10 Fumigating tents. (See Tents.) 70 FUMIGATION FOR THE CITRUS WHITE FLY. Page. Fumigation against citrus insects, history 2=---==-eese sees eee ee 7-8 white fly, absence or elimination of food plants other than citrus fayorable:3-2--sses eee eee ee 9-10 appearance of dead larvee and pupe.....-----.. 50-51 chemicals; cost:..2...c2 2255 ee ee eee 58 handling, and protection from mois- TUTE: ees rg eee eee 25 proportion of water and acid......... 25-27 purity required 2-222. -o22- soe ee 25 concerted action favorable:..-..- 2422-252) -pere 9 conditions favorable or necessary to good results.. 9-14 cost compared with spraying...-.---- .. 62-63 density of gas at various heights oe prea : 51 dosage requirements with bell or hoop tent....-- 49-50 sheet tent............. 40-49 ECONOMY Oltrealtinentts- eee ee ee 59-63 effect on trees and fruit:...--252 2. aea5 5-52 Soe oe EQ ipment so Nes See ee ee ee eee 14-24 ExPensesesee-eeee SE SSR Rh Sa eee ee 56 histonye ct es see eee ee OO 7-8 isolation of prove favorable... 42 S23 sees see 9 losses: prevented. thereby-=i22=o.-..45-e ee ee 59-60 MeCASUTIMG MES... se- = oe 30-35 meteorological elements favorable............... 11-18 method of generating’ gas. .-<. 7/2 2-45 eee 39-36 handling bell tents22:5.-253 se ene 29 sheet ‘tents 2325/0 s2seeeee 27-29 methods of computing cubic contents of tented (ARES ona se . 39-40 hiner of enrede trees 39-40 miscellaneous experiments and observations. ... 50-54 TeqUITeMen isis 22-5 nee eee nursery stock for shipment--...--.-.....--....--. 54-55 poles!fors handlimestentstes. 2-2 eee Oe PRECAUTIONS 2355-4 One ane eee ae 55-56 procedures: 22.552 se ase eae ee eee 27-38 proportion of water and acid.................... 25-27 season-of ‘year favorable: 5-5-2 dS eee 10-11 | table of dosages: ..<:352.35,) 20 otee UEMUS Cares sciat seen e ae ee eee 19-20 CONStTUCTION 2A a eee eee eee 15-19 mildew-proofing, oiling, and painting..... 19-20 shrinkage-c. Spec asse ee eee 17-18 stylesees StS oo oe eee eee 14-15 time required? eee ee ee eee 38-39 trees, regularity of setting favorable...........-- 14 size lavorables na tee ee: 00 ot ee 14 era) Singiheyenoviesees ssn ee 54 IMUTSCLY..c: ase eee eee 54 uprights-tor hand lime fents-::.2---- eee 21 Versus naturaly control. 2:5. es 1s eee ee 63-65 WOrkroulin es shiv Se ee eee ee ...-- 36-38 Fungous,diseases inicontrol of-white tye nss2 225-0320 9 oa eee 64-65 ee ee a ee ee INDEX. (ial Page. Gudemajasmeuovdes, food plant of white fly.:..-2.2222c0s--2-.22-04--c 2.0. 10 Gan! density at various heights above the ground....:.4-<-.:--:.----.--.-..... 51 ive Here CHETAN. mene oe cictaseee os SE Oe I eee arnt as canis d) 35-36 ERIMeImUc as aAneCted Diy LUMMPAllON=: 22.2222 2 oe = sae eee eee eee ot ees oe 54 pees as wield by TUMIPALION. -o Pee meme eee ea yoo sk le oo, 52 iomive, diagram as euide in fumigation: — =o...) .2 wee ek eee soc eee 23-24, 38 PAMIGUivaS AEC UNO TIMMNGAON es 02 alee ee Soak ses os gee Meer ewe ss 12-14 Hydrocyanic-acid gas. (See Fumigation.) . Bee pur Chast, CONLEOL Diy TUMMPATION. 222s ..26s.cenceee oe ae eaten ce ees e oa. if Peo ton OMorove ta VOrue LUMIPAtION: <222.2.-.-< sss 0s ese. oe cee bad lee es eee 9 Jessamine, cape. (See Gardenia jasminoides.) ee LNA | C Tea epeeete mn cent teeta sis teeta oan Sie bso s aie eet UE Sato S wide RG le ee ER 18 {DBI C(Gie Pore IRVETEN FECTS LOST ACG 0.51 ae ih ae ESE ag es 58 Laurel, cherry. (See Prunus laurocerasus.) Lepidosaphes beckii, losses prevented by fumigation............--.---..---.- .. 61-62 Light as affecting fumigation against white fly..................---------+---- Alt PU uaUuTes pp, TOO plants OL WMIte dine. 25.002. sees =. See ok eee tse n es ds 10 Bia BOOd spl ani Ol white thy oie see sce see wie Se circ cn se Se ele eo ee ee Sms 10 Losses from scale insects prevented by fumigation...............----.---..... 60-62 wiitestiy prevented byetumipations 2.2.9.2. 2-.2=. 22-12-25 2.seees 59-60 Panamera, ood plant of white tly >....0-<0.'. is toe vent eset eee 10 DinGuOni ne soon Plant Of White Hives ronsssss cca besos wea cee ee 10 Measurements of trees, necessity in fumigation................-.------------ 30-31 Melia azedarach and M. a. umbraculiformis, food plants of white fly..-..-.-....- 10 Meveorolozical-elements favoring fumigation... 2... 1 222<- cence ene cee neces 11-13 Moisture. (See Humidity.) Mold, sooty, resulting from white-fly attack............-.-.-. SESE /atseve Serato - 64 cmmnoreanden. 100d plant. on white tly... 2 -.25.. 59.22.65. 0.2le tea es ew bee 10 Nursery stock for shipment, fumigation against white fly..............-.....-. 54-55 CLECs UIC At ONsACAImMstswMiteMthy== ess se cee 2 seme Jone 22 oes < = J 54 Oak, water. (See Quercus nigra.) Oleander. (See Nerium oleander.) Opuntia sp., use of juice for painting fumigating tents............--.--.-.-.-- 19 Pameerriitasatiected by aumMieation. S62. toe cea ee hee he Se sae seek uses 53-54 PeCa as aeCled. DY LUMP ATION ag. eee cee ee cee Seles es eeieed yaee 6+ 01-08 Palmetto, scrub. (See Sabal megacarpa.) cae eodepmani Oiwhite ty: Aa: etoee ees cae qh ete eee boise see eke les 10 Persimmon, Japan. (See Diospyros kaki.) wild. (See Diospyros virginiana.) BanerOr Mandiine fUMNCAtINe TOMS .—\sosc+se20 nec ease nce eke ee ee neenems os 20-21 Pine valid Tor Mimivatlon, COSt.2...22 3.22.22 55-2 = Ses eee ee 29 WOK; =] 2 eee eee Secondary sexual. characters: i222. i-4..2ce ee eee ee ee Proportion of sexes surviving hibernation....-.2-<-52- <= -= 222-7 s=- eee Relation of hibernated weevils to food supplyc_.5--4 2222 --2-¢ -s-5-e eee ee Summary and conclusionst:2c22-4---.10-- 22 ae e See ee eee i Pirate I. cE, TEL. rv: NV; VI. VIL. VIII. IX. LELUST RATE GIN Se PLATES. Weather-recording apparatus and fence-row shelter. Fig. 1.— Weather apparatus used in recording temperature and humidity conditions. Fig. 2.—Typical weedy fence-row, affording excel- lemigsheliteniorkwiee vill sissies sss esc ot oe erste ote ee ee eet Favorable shelter conditions in and around fields. Fig. 1.—Cotton field adjoining grove of trees laden with Spanish moss ( T%llandsia usneoides). Fig. 2.—Near view of moss. Fig. 3.—Cotton stalk having many bolls infested by weevils at hibernation time....-..-- Seed house and hibernation cage, Keatchie, La. Fig. 1.—Seed house opposite which the first sign of weevil work was found at Keatchie, La.,in 1905. Fig. 2.—Large cage built for hibernation experi- PETS Te RENAN Ah neo eter nn oh aay Wierda eit B Sch sre mee Scere Hibernation experiments, Dallas, Tex., 1905-6. Fig. 1.—Four-section cage used for experiments, built over cotton. Fig. 2.—Shelter con- ditions as occurring naturally in section | -.........------------- Shelter conditions in Dallas, Tex., experiments, 1905-6. Fig. 1.— Piled cotton stalks and piled boxes in section 2. Fig. 2.—Stand- ing cotton stalks versus piled leaves, section 3..........-.-.------ Cages for hibernation experiments in Texas, 1906-7. Fig. 1.—Dallas, Tex., cage on flat, black-waxy land. Fig. 2.—Calvert, Tex., cage on slightly sloping, sandy land in post-oak region. Fig. 3.— Victoria, Tex., cage on sandy-loam slope: between bottom and (ol ents hoe ae ee ee Bs BRS SEO ee eee oe ee eee Shelter conditions, Dallas, Tex., cage. Fig. 1.—Active weevils try- ing to escape through wire on October 20, 1906. Fig. 2.—Section 1, in which weevils were placed October 13, 1906, 2.61 per cent surviving. Fig. 3.—Section 4, started October 16, 1906, 4.07 per FES EXTANT LIN VLLGI Se a0 RN F N ae ee Hanging moss as affecting hibernation and emergence. Fig. 1.— Section 7, with hanging moss in top of cage. Fig. 2.—Same sec- tion, ground conditions, started October 24, 1906, 6.95 per cent surviving; emergence ceased June 17, 1907..........-..---------- Shelter conditions producing average survival at Dallas, Tex. Fig. 1.—Section 8, started October 30, 1906; emergence ceased June 15, 1907; survival, 8.85 per cent. Fig. 2.—Section 5, started Novem- ber 5, 1906; emergence ceased May 15, 1907; survival, 12.22 per cent. Fig. 3.—Section 3, started November 12, 1906; emergence ceased May 21, 1907; survival, 14.74 per cent......--.----:------ . Exceptionally favorable conditions and boll experiment. Fig. 1.— Section 10, a, bolls exposed on surface; 6, corner where bolls were buried 2 inches deep, started December 6, 1906; emergence ceased May 2, 1907; survival, 4.51 per cent. Fig. 2.—Section 9, stalks left, started November 13, 1906; emergence ceased June Pome eVEY i oo PCr COM o- 22... 2 22 = os sls ce ocincaeecnaee Page. 30 30 38 50 50 64 74 74 Fie. 1. HIBERNATION OF THE COTTON BOLL WEEVIL. TEXT FIGURES. Chart showing mean average temperature, rainfall, and weevil emer- gence, Keatchie, La., March to/Jime 906 22e 2p eecce meet . Chart showing mean average temperature, rainfall, and weevil emer- gence, Dallas, Tex., March to; May, SISOG2 ee hore ere eee ete . Chart showing mean average temperature, rainfall, and weevil activity, Dallas, Tex., October; 1906, ‘to\March, 19072. 22.5 eee eee . Chart showing mean average temperature, rainfall, and weevil activity, Calvert; ‘Tex:, October, 1906, to: March, 1907222 <2... 2-2 eee . Chart showing mean average temperature, rainfall, and weevil activity, Victoria, Tex., October, 1906, to March, 1907-222 225s) 226 eee . Chart showing mean average temperature, rainfall, and emergence from hibernation, Dallas, Tex, March to June, 1907-2: 322-2) sees . Chart showing mean average temperature, rainfall, and weevil emer- genee, Calvert, "Tex, March tor dimme, 907. --2e. 2-2-2 ena ee . Chart showing mean average temperature, rainfall, and weevil emer- pence, Victoria, lex. Marchi to Wimes O01 oem cee ttre . Secondary sexual characters-of Anthonomus grandis....-.------\.------ Page. 41 53 59 60 61 69 70 “il 91 Jeg eee Natural conditions annually reduce enormously the numbers of the cotton boll weevil. Although no two seasons are exactly alike, never more than a small percentage of the weevils in the fields in the fall is permitted to survive until sprmg. Jn fact, winter is the most critical season in the whole life history of the weevil. Any steps in control of the weevil during the winter are therefore much more important than those which can be taken at any other season of the year. To destroy ten weevils in the winter is much better than to destroy many thousands in the summer. The cotton boll weevil is now causing a damage in the United States each year of at least $25,000,000. The indications are that this amount will continue to be lost for some time at least on account of the difficulties in control which will be encoun- tered in the Mississippi Valley. For these reasons the Bureau of Entomology has conducted careful investigations of the hibernation of the weevil and presents the somewhat detailed results in this bulletin. Until this time the hibernation of the boll weevil has been less understood than any other phase of its life history. This was due to the great difficulty in obtaining the necessary data and the fact that the phenomena of hibernation are not necessarily identical in different seasons. In fact, it will be seen from the following pages that there have been very important dissimilarities between the years when special observations have been under way. The necessary repeated -work in large cages in different localities has now been carried on and extensive field observations have been made in various representative parts of the infested area as to the natural situations in which the hibernating weevils occur. As a result, the present bulletin will make the life history of the boll weevil during the winter season at least as well known as any other portion of its biology. In the work leading to this bulletin practical considerations have always received primary attention. However, it has repeatedly been shown that careful detailed investigations of injurious insects may result in important suggestions for control that are not foreseen at the beginning of the work. Therefore the topic of the hibernation of the boll weevil has been investigated from every possible standpoint. Its importance, as a critical period in the life history of a most injuri- ous pest, has abundantly warranted this work. 7 8 HIBERNATION OF THE COTTON BOLL WEEVIL. Foremost among the points of immediate practical application shown in this bulletin is the enormous importance of the fall destrue- tion of the plants. This has been one of the recommendations of the Bureau of Entomology for some years. Its importance will increase rather than diminish in the regions now invaded by the insect. The cage experiments at Dallas, Calvert, and Victoria, Tex., in the winter of 1906-7 have given most important and accurate data showing exactly what may be accomplished by the fall destruction of the plants at various dates. This bulletin, moreover, shows the most favorable and least favorable conditions in the hibernation of the weevil. This information can be put to practical use by every farmer in the infested area. It shows exactly where the most effective work can be done. A not unimportant feature is the showing of the abso- lute impracticability of late planting to obviate damage by the boll weevil by reason of the remarkable longevity of hibernated individuals without any green food whatever. The information included in this bulletin has been accumulated through the investigations and observations of the numerous agents connected with the work during the seasons of 1902-1907. Some of the facts have been briefly stated in previous publications, particularly Bulletins 45 and 51. The manuscript for the present publication was prepared during the summer and fall of 1907, and since that time some of the conclusions drawn from this study have been published in connection with other bulletins and circulars relating to the weevil and its control. But in no other instance have all of the facts been considered or their complex, intimate, and important co-relationships studied as in this work. On account of the large amount of work that has been done and the practical importance of many of the conclusions drawn it has been considered that full indication should be made in the bulletin of the methods by which the conclusions and recommendations are reached. Therefore special pains have been taken to give all essential data and to represent by charts matter that can thus be graphically expressed. It will be noted that the various experiments dealt with in this bulletin are taken up according to the years in which the work was carried on. The result is that some special topics, such as time of entrance into hibernation, will be found discussed in several places. It has been found entirely impracticable to follow a strictly topical system and discuss each point connected with hibernation with refer- ence to the work of the various years. This impracticability is due principally to the great natural variations in the seasons. Never- theless the first part of the bulletin discusses the general feature of hibernation and the summary at the end has been written in such a way as to bring the principal conclusions on the various topics mto condensed form. PREFACE. 9 The question of credit to the various investigators who have con- tributed to this bulletin is rather complicated. Mr. E. A. Schwarz studied carefully the hibernation of the weevil at Victoria, Tex., in the winter of 1901-2 and his observations have been utilized. Later Mr. Wilmon Newell, secretary of the State Crop Pest Commission of Louisiana, assisted by Mr. J. B. Garrett, planned and executed a series of experiments in the hibernation of the weevil which was much more extensive than any similar work that had been done up to that time in this country. This work was done in cooperation with the Bureau of Entomology, and the results, through the liberality of Mr. Newell, have been largely incorporated into this bulletin. Mr. J. D. Mitchell contributed important facts from observations during several seasons, especially with reference to actual winter field con- ditions. Many of the details in the plans for the extensive work of 1906-7 were worked out by Dr. W. E. Hinds, who also superintended the extensive tedious work necessary during the following spring. Jn all this work Doctor Hinds was assisted by Mr. W. W. Yothers, by Mr. A. C. Morgan, who had charge of the work with the large cage near Victoria, and by Mr. C. R. Jones, who was located at Calvert. Mr. Yothers collaborated with Doctor Hinds in the arrangement and correlation of the data obtained at the places mentioned and in placing in manuscript form the records of many of the experiments of previous years. For two winters Mr. Yothers carried on special observations, largely of his own planning, as to actual field conditions. In this work he collected large quantities of bolls and various forms of trash in and about cotton fields, and from careful examinations of this material in the laboratory he was able to determine many very impor- tant facts in regard to the several classes of rubbish, or winter shelter, which are most likely to protect weevils and to insure their successful survival through the winter season. W. D. Hunter, In Charge of Southern Iield Crop Insect Investigations. HIBERNATION OF THE MEXICAN COTTON BOLL WEEVIL. ENTRANCE INTO HIBERNATION. In the study of hibernation of the Mexican cotton boll weevil (Anthonomus grandis Boh.) we shall first consider the factors affect- ing the abundance of weevils which may enter hibernation, the dependence of the number of weevils present upon preceding con- ditions of food supply, the climatic conditions accompanying or producing the beginning of hibernation, and other biological facts which may be of interest or value in connection with this division of the subject. SUPPLY OF WEEVILS TO ENTER HIBERNATION. The common name ‘‘cotton boll weevil,’ which is uniformly applied to this insect, may be in part at least responsible for a mis- leading impression in regard to the most common point of attack and place of development of this weevil. The common name was first applied because of the fact that in the first recorded case of this insect attacking cotton the specimens were found in bolls. It is a fact, however, that by far the greater number of weevils to be found in any field at any season of the year have really developed within the buds or squares rather than within the bolls. In the first place, it is perfectly evident that durmg the entire growing season of the plant, in the infested area, probably not much more than 10 per cent of the squares which form ultimately produce bolls. For this reason the weevils find opportunities for reproduction many times greater in squares than in bolls. In the second place, a careful study of the habits of the weevils shows that they prefer squares both for feeding and for reproduction. In the third place, the average period required for development in squares is only one-half to one-third as great as it is in bolls which become more than one-half grown. These three considerations insure a far more rapid and abundant multiplication of individuals through the medium of squares than through bolls. Wherever weevils have been present in average abundance at the beginning of the season, unless they have been unusually checked by climatic conditions unfavorable to their development, a condition of total infestation of squares is usually reached between August 1 ll Po, HIBERNATION OF THE COTTON BOLL WEEVIL. and 20. By this time practically all of the crop which can be expected will have been set and many of the oldest bolls will be found maturing. If a moderate crop of bolls is being matured the formation of squares usually ceases, almost if not entirely, for a period of several weeks. Whereas in the early part of the season female weevils could find abundant opportunities for depositing their eggs in previously unin- fested squares, after the time of total infestation is reached such opportunities practically cease to exist. The available supply of squares and bolls becomes too small to support the large number of weevils which may be present, and conditions become decidedly unfavorable for their further multiplication. It is at this season of the year, usually from August 15 to September 20, that the largest general dispersion movements of the weevils take place. It is at this season also, during recent years, that the cotton leaf-worm has become sufficiently abundant to secure a partial or complete defolia- tion of the plants. While the occurrence of the leaf-worms is by no means regular, the effect of their work is to still further limit the available food supply of the boll weevil and to force them into a more general dispersion from the defoliated plants. On account of the reduced supply of squares, the increased period of development in bolls, and the extensive dispersion movements of the weevil at this season of the year, it usually happens that the actual number of individuals in a field becomes greatly reduced. Following the maturity of a considerable portion of the crop of bolls, and usually in connection with the occurrence of a heavy rain- fall, a renewed growth of the plant commonly produces an abundance of squares. It is this late top growth of the plant, which serves no good purpose so far as further production of cotton is concerned, that is primarily responsible in most fields for the needlessly large number of weevils produced between the time of maturity of the crop and the usual time of destruction of the plants by frost. a CD er are * WEATHER-RECORDING APPARATUS AND FENCE-ROW SHELTER. Fig. 1.—Weather apparatus used in recording temperature and humidity conditions. Fig. 2.— Typical weedy fence row, affording excellent shelter for weevils. (Original. ) Bul. 77, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE |] FAVORABLE SHELTER CONDITIONS IN AND AROUND FIELDS. Fig. 1.—Cotton field adjoining grove of trees laden with Spanish moss ( Tillandsia usneoides). big. 2.—Near view of moss. Fig. 3.—Cotton stalk having many bolls infested by weevils at hibernation time. (Original.) SHELTER DURING HIBERNATION. 31 One fact should be emphasized in regard to practically all classes of shelter which have been mentioned as occurring within cotton fields, i. e., that it is possible as a rule to destroy or remove practi- cally all of them. Undoubtedly the burning of cotton stalks, weeds, erass, and other rubbish is the easiest and most effective method of destruction where it can be practiced. Next to this in importance would be the destruction of the stalks by a stalk chopper and plowing under all the rubbish. In the latter case it must be stated that many weevils which may be buried to an average depth of 2 inches will be able to escape through the soil and may then find shelter around, if not within, the field. HIBERNATION SHELTER OUTSIDE OF COTTON FIELDS. Unquestionably timber fringes skirting cotton fields are exceed- ingly important because of the shelter which the fallen leaves and undergrowth provide for weevils during the winter. The conditions to be found here are so exceedingly favorable that a majority of planters seem to recognize that the most severe infestation of young cotton in the spring may be expected to occur near such timber. Where the moss (PI. II, fig. 1) occurs abundantly it is second only in importance to the fallen leaves as a shelter for weevils. The fact that weevils have been taken early in the spring upon trees at a dis- tance as great as 2 miles from a cotton field shows the extent to which they may possibly scatter during the fall or seek for cotton during the sprmg. The planter need not, however, be alarmed by these facts, inasmuch as it is certain that but. few weevils hiber- nating away from the immediate vicinity of cotton fields will sur- vive to find food supply upon emergence. Cornfields adjoining cotton or cornstalks scattered throughout cotton fields may shelter many weevils. This was first noticed by Mr. E. A. Schwarz at Victoria in the winter of 1901-2 and has since been corroborated by a number of observers. Several examina- tions have been made of haystacks in the vicinity of cotton. This is a task quite comparable with that of seeking for the proverbial needle and it is not surprising that the results have been very meager. The fact, however, that traces of weevils have been found in these examinations indicates that weevils may find shelter under such conditions. Farmyards, seed houses, barns, ginneries, and oil mills also afford exceptionally favorable shelter for weevils. Especially in ginneries and seed houses (PI. III, fig. 1) the weevils become concentrated with the concentration of the cotton or seed and frequently may be found in large numbers within or around these buildings. In con- nection with this subject the reader is referred to a fuller discus- 32 HIBERNATION OF THE COTTON BOLL WEEVIL. sion of the significance of ginneries and oil mills in the distribution of weevils and of the methods recommended for controlling them which may be found in Farmers’ Bulletin No. 209 of the Department of Agriculture, “Controlling the Cotton Boll Weevil in Cotton Seed and at Ginneries.’’ Numerous observations have shown that weevils have been taken into new localities through the agency of shipments of cotton seed and cotton-seed hulls from ginneries and oil mills handling infested stock. Definite observations have been made showing that living weevils may occur in cotton seed at planting time. While it is probable that few would survive in a large mass of seed it is certain that some might do so and be distributed in the planting of the seed. TaBLe XI.—LEuxperiments of 1904 to 1906 to test hibernation in cotton seed. y 7 ral When | Weevils | When | Weevils | Weevils Locality. 1 oe i i exam- found found hiberna- | hiberna- | jheq slings eal tion. tion. is : : 1904. 1905. Terrell, Wexss le. S sees wee hs ote ac eee Ree neeaee Nov. 13 200 | Apr. 20 } 0 154 DDO Eee he ts 2s de ..-| Nov. 30 200 | Apr. 21 0 139 DO RSA Ao a se ee ky er ne = leDecr 15 PANO. I Nyohey PP 0 170 Gorsicanay Tex (nye Se ee Ne ee ..-| Nov. 14 150 | Apr. 19 0 127 G@alwert tle xe.) s Sine Ss Si en ee eee Nov. 15 200} Apr. 7 0 152 1 Dok a Sea nes =e aoe Eee Serene oes See be bhp ame Nov. 30 200 | Apr. 8 0 176 DD Oia tent pitt Rao aycimts Payette che Syn tec ees as eee Rea Dec. 15 PANO ae solas.§ 2) 0 142 Victorian exes oe pd See ee ee en Sey! Nov. 10 200 | Apr. 3 0 130 Do Nov. 17 200'=-=COs=ee~ 0 144 Do 200 | Apr. 1 0 150 Do 200 | Mar. 31 0 115 Do 200 | Mar. 29 1 149 Do 200 | Mar. 28 1 123 TO talcte tee eh ae ee a ts Se es oa | cae ee 25600M| teseeees ce a2 1,871 : 1905. 1906. TOT UR EEA No A Sus eer ea aes NOTES apse, a ary Weenie At ain en? | Nov. 1 100 | Apr. 28 0 92 STD OE OR ee Se eae he Se oe ee A ee RL te oe | Nov. 18 } 200 | Apr. 30 0 160 IYO RSE eens See ee ere ere es Bees aul etre Oe Dec. 4 | 200 | May 3 0 181 | Xo Rte a are er SES et ei ates eet en Dec. 15 900 | May 4 0 862 ERO HES SPS eles ee ee ee es Fe Se dh eer | eee | 1400S eae aoe 0 1,295 VACLOPIO A DORA: ose eR he tet ae ENS Se opt ee eas ea | Nov. 7 100 | Apr. 2 0 93 Oi cey 8 ate ee aN. eae WN cee haaeaty SBN Oe Me Roe AO alIE ak O ama 100 | Apr. 7 0 93 DOR ra Sree Stee ee ee Be a RX ee ee: Nov. 13 100 | Apr. 3 0 97 DOS ES ae etiis cat Sates Se Saree ae eS ee ee | Nov. 30 100) )5=-doLs-=- 0 100 ID OSS SHG eh usenten nese tomes dace gee eee saree | Dec. 11 100 | Apr. 5 0 96 Totals oF a. oa ee eee ee Oe Ae aoe eee eee SOOM sas ae one 0 479 aQOn January 27 47 dead and 18 living weevils were removed, and on March 4 4 dead and 1 living weevils were removed. While the number and percentage of weevils surviving in these experiments is very small indeed, the fact that some do survive is the special point having significance. The occasional occurrence up to planting time of living weevils among seed from infested localities is alone sufficient justification for every quarantine restriction which has been placed upon cotton seed and other cotton products by uninfested territory. The Mexican entomologist Prof. L. de la Barreda, under the direc- tion of Prof. A. L. Herrera, of the Comisién de Parasitologia Agricola, HIBERNATION EXPERIMENTS IN SMALL CAGES. 33 has made some very pertinent observations on the occurrence of boll weevils in cotton seed intended for planting.“ In January, 1903, this entomologist examined a number of sacks of seed received from the infested area of Texas for planting in the Laguna region in Mexico. Six sacks from one consignment were selected. In these, 12 living weevils were found, together with 56 dead ones. Later examinations were made of a number of shipments of seed from the infested por- tions of the United States. In every case living weevils were found. This work was done in the month of January. These observations show clearly the real danger that exists in the shipment of cotton seed from infested localities to those where the weevil does not occur. HIBERNATION EXPERIMENTS IN SMALL CAGES. In many ways it is possible to obtain more accurate data upon hibernation of weevils through cage experiments than through field observations. In the cages conditions may be prepared which are typical of those to be found in the fields. The number of weevils ~ within a given space can be largely increased without overcrowding, so far as the possibility of their finding shelter is concerned. The action of the weevils in seeking and in leaving shelter can be deter- mined more accurately in cages than in the field. The food condi- tions may be varied to represent various field conditions and, finally, knowing definitely the number of weevils placed under certain con- ditions, it is possible to follow them closely enough to determine with a great deal of accuracy the proportions surviving. From a com- yarison of the results obtained under various experimental condi- tions those conditions which are most favorable as well as those which are least favorable to successful hibernation may be determined with considerable certainty. In all of our experimental work of this nature the cage results have been checked so far as has been possible by field observations. With the continued study of the boll-weevil problem the necessity for increasingly comprehensive experiments upon hibernation has become apparent. The work thus shows from year to year a growth in complexity with the constant purpose of increasing the accuracy of results by making the experimental conditions conform as closely as is possible to field conditions. In the early stages of the work the hibernation cages were small and portable. Some were placed out of doors where they would be fully exposed to prevailing climatic conditions; others were placed in the shelter of buildings or under similar conditions where the favorable nature of the shelter provided might be determined. 2 Boletin de la Comision de Parasitologia Agricola, vol. 2, No. 2, pp. 45 to 61. 90317—Bull. 77—09——3 34 HIBERNATION OF THE COTTON BOLL WEEVIL. CAGE EXPERIMENTS OF 1902-3. In the experiments made during the season of 1902-3 most of the weevils used were collected in the field at Victoria, Tex., about the middle of December. Some, however, were reared weevils which during the months of September and October previous had become adult. They were confined in boxes and jars covered with cheese cloth. Various kinds of rubbish were placed in the cages, some of which were placed in the fields and some in a building. These cages were all examined between April 15 and 30, 1903. Among the 25 lots tested, including 356 weevils, it was found that an average of about 11 per cent had survived. None of those which were adult before November 1 was living on April 15, while nearly 16 per cent of those taken in the field about the middle of December were still alive on April 27. A slightly higher percentage had sur- vived in the inside tests, and it appears that a considerable degree of dryness favored survival. One-half of all the weevils surviving were found in the folds of dead banana leaves on April 15, while the balance were scattered among hay, dried cotton leaves, empty bolls, and in or under earth. CAGE EXPERIMENTS OF 1903-4. During the season of 1903-4 450 weevils were tested in lots of about 50 each. From October 21 to December 16 one or more lots were started each week, part of them being placed outdoors and part indoors. In addition to the confinement of adults, about 400 infested squares were picked from the ground about November 15 and kept until the following March. These squares were examined on March 18. It was found that most of the stages had perished while yet larve. Nearly one-fifth of the squares contained dead adults. In the lot among 128 stages there was one adult which was still alive. Examination in April, 1904, accounted for all but 15 of the 450 weevils confined, but one weevil was found alive, and that one was placed in hibernation on October 29 in a cage out of doors. The results during this season seem to contradict in some respects those obtained during the preceding year, which indicated the favorable nature of inside shelter. CAGE EXPERIMENTS OF 1904—5. The work of the season of 1904—5 was planned to include a number of localities representing in a general way the various portions of the weevil-infested area. In all cases the cages consisted of boxes about 1 by 2 feet in size and covered with 14-mesh galvanized-wire screen- HIBERNATION EXPERIMENTS IN SMALL CAGES. 35 ing. These were all placed out of doors at various dates between November 3 and December 15, 1904. The examinations were made during April, 1905. TaBLE XII.—Summary of hibernation experiments, 1904-5. 3 Total number of weevils found— al ms 4 : a Ss Te les We 4 a 8 gi * Bas! Zz co iso | st ~~ 2 . 16 qd Locality. rae) a ajay 2 |e 2s te eal) AS al tea Se — as | 2 12] 3sid/_ Hig iZid|jel fs ie - SE WRB) yiceh || SS Sia} s | ° 2 Sel eeitodt St dl Rey stele |ieicey i te) |p cstollemie eee hl l= a = ea eset se | eke tN) Seal teae Westen) Ue els eee re | is Eo) e |S eie | Slay as Pee lie) lS 2 g One a m/2\/o/a2/5/5]6 Bikes BLE IES S/aisisisis|siais jalé Mornrelle Mexa se dose ca asa ae access 715 | 244] O /108 | 68 | 13 Li 3 Lela ou eis) loeee epee eee RAIS LO Xe eee eee were Seen 650} 254] O |116/ 58} 14) 0} 8} 0] 23 Soliks eo) (19) Pees Reenihnvillesbars....22 ) 54 | 75 | 25 | 32 12 | The most striking point shown in this table is the fact that no weevils survived except at Victoria. Even there the percentage was very small. Undoubtedly from 5 to 10 per cent of the weevils placed in the cages must have escaped through the wire before the season became cold enough for all to hibernate. The explanation for the death of all weevils confined north of Victoria, Tex., may be found in the exceptionally severe climatic conditions occurring during this season. These have already been indicated in Table VIII, page 27. It should be stated, however, that while weevils were scarce in the spring of 1905 in all of these localities they were not exterminated in Texas except at Paris. At this place examinations made during the season of 1905 failed to show any weevils in a field which had been quite heavily infested late in the season of 1904. HIBERNATION EXPERIMENTS IN SMALL CAGES, 1905-6. Tests were made at Dallas, Calvert, and Victoria, Tex., representing the northern, central, and southern sections of the infested area. Owing to the increased complexity of the experiments and the more valuable character of the results obtained, it seems advisable to present the data in a somewhat more detailed manner. 36 HIBERNATION OF THE COTTON BOLL WEEVIL. TasLe XIII.—Summary of hibernation experiments in boxes at Dallas, Calvert, and Victoria, Tex., in 1905-6. DALLAS. Number of wee- Out- | Wee- vils found— When ¥4 doors | vils | When ex- Per- put in Kind of rubbish. or in- | put | amined con iaee Remarks. GGBab fet Rttee| ede ee 1905. 1906. Nov. 1] Corn shucks, grass, | Out...} 100 | Apr. 27 0 92 0 cotton leaves. Do...| Cotton leaves. ......- jie sie LOO;|eed Oseces 0 80 0 In chicken house. Dove. |hoaen GOs Se caeneeeee Ibnbsaeee 1003 |Ezedose- ee 0 64 0 In seed house. Do...| Sack of cotton seed...| In..... 100 | Apr. 28 0 92 0 Do. Nov. 17 | Grass,leaves, rubbish.| Out...} 100 | Feb. 19 3 82 3 IDOL Ns aera Glo a seeperce sae nisscae 100 CISAGs 0 57 0 Do. Nov. 18 | Cotton seed.........- nee: 200 | Apr. 30 0 160 0 Do. NOV.) 261)" Only orasse eee oeee Out...} 200 | May 0 165 0 Do...| Grass, seed, cotton...| In..... 2009 Sen Osesee 0 165 0 Do. Dee: -4 | Cottoniseed -— 222222: Iineeces 200 | May 0 1sl 0 Dec. 11 | Corn shucks, leaves. .} Out...| 200 |...do..... 0 140 0 Dosen ss GOL ae frees messes 200 | May 1 0 195 0 : Dec. 15 | Cotton seed.........- nies 900 | May 4 0 862 0 300 in each of 3 sacks. Out GOO) Ses cae 2. 3 479 0.5 Total....-..... AES etn eae 0| 1,886 | 0.0 CALVERT 1905. 1906. Nov. 7] Corn shucks, grass, | In..... 100 | Apr 18 0 98 0 cotton. Dose leere OS ae cee aHBAd Outs 945 doses. 1 45 1 INOVis oie loeeee Oot es ee aeeseees Tneiee 2: 205s|\paeGOnsece 0 205 0 Dosaleaaes GOs se eeaneec cents Out...| 200] Apr. 19 40 145 20 Out.. 294A ene 41 190 14.0 Total.......-.. {fn ieee? snd cae toer 0} 303| 0.0 VICTORIA. 1905. 1906 INOWen Os eviixedieseee soe e es oe | Out 100 | Apr. 6 2 43) 2 INOW) OG)|os eee GOs seen et ws | Out 100) || Apr: 7 1 23 Ht Doves ators GCOzP eee ee Ibdle—s= - 100 doses 0 73 0 NoveSileeses Ne Seer eee Out. 100 | Apr. 4 4 53 4 Os lneere On enantio ne lhgles= 100 | Apr. 5 0 97 0 NoversOll|pecee GOs Sechce oe eeeee Out. 100 GChoyeon 1 39 1 Dorealeeens GO ssaert hacks eset mee 100 dOnescs 0 94 0 Decs ieee. GOeaexer soe casunts Out. 100 | Apr. 7 3 51 3 Dor cela. (Ie S66 deacacnonels Insss. 3 112 edOnese- 4 100 3.57 Out GU De eesorck 11 209 2.21 Total...-.....- Nr Biot ieee! 4| 3641 .97 Total of 3 local- |fOut...|1,394 |.......... 55 878 3.9 ThLES aes \\iraeeeee DOU Talc cwamewere 4 2,553 .14 In the small-cage experiments of 1905-6 but three localities were tested. In the 26 experiments were placed 4,211 weevils, of which number 1,394 were out of doors and 2,817 indoors. In only one cage did weevils survive within doors, and that was at Victoria, where it would seem that such protection was least needed. The two most striking results were the small survival at Dallasand the remarkably large survival in one of the outdoor experiments at Calvert. In the outdoor tests an average of 3.9 per cent survived, HIBERNATION EXPERIMENTS IN SMALL CAGES. oh while in the others but 0.14 per cent survived. In an average of all tests the survival was 1.4 per cent. The nature of the shelter failed to show any significant influence in these small-cage experiments. The relative favorableness of outside conditions is shown in the following table by a comparison of the data in each of the three localities. This table does not include the experiments with cotton seed: TABLE XIV.—Comparison of survival records outdoors and indoors for three Texas localities in 1905-6. Outside. Inside. Locality. Weevils Weevils survived. Weevils Weevils survived. put in ore HOY | |} ——$——— hiberna- hiberna- ; - Percent- 7 Percent- tion. Number. age. tion- Number. age. WHCEOD Ae cher oe cpr ae teem i city ee 500 11 Dn, 412 4 0.97 Malivieni Nein ek cae cement a4 294 41 14.0 305 0 0 PAIS eM exceee ce MO ktm se ae oe her x Ns 600 3 -o || 2,100 0 0 Motales= ce. SSBC ROE COG AAA ABA 1,394 55 3.9 2,817 4 0.14 During this season it is very evident that in all localities outdoor conditions were decidedly more favorable for successful hibernation. Upon the average the survival out of doors was twenty-eight times as successful as in the tests made indoors. Grouping the experiments according to fifteen-day periods from November 1 to December 15, when they were instituted, the most favorable time for entering hibernation seems to be indicated. TABLE XV.—Comparative favorableness of periods for entering hibernation, 1905. g ) | : Total Period. survival. Nov. 1-15, 1905. Nov. 15-30, 1905. Dec. 1-15, 1905. Locality. Weevils Weevils Weevils INum-| Per Weevils) Survived. Weevils) Survived. |Weeyils| survived. eral licearea put in put in put in hiber- hiber- | hiber- nation. |Num-| Per | nation.|Num-| Per | nation.|Num-) Per ber. | cent. ber. | cent. ber. | cent. Waichonia WDexs. ue o28 ete 500 CaN alee! 200 On 212 7 | eke! 15} 1.60 Malwertwlexrs 0 ss seco 194 1 aD 405 AMHISLOSO! | Warsecmes| seamen are ccclere 41 | 6.80 Malas exer © 326 cet ee Se 300 0 0 600 3 aD 400 0; O 3 23 Motels secesetecesees 994 | 8 -8 | 1,205 44 Sadi 612 if ial 59 2.10 This table does not include the experiments in cotton seed. The comparisons show that during the fall of 1905, November 15 to 30 was more favorable than either an earlier or later period at Calvert 38 HIBERNATION OF THE COTTON BOLL WEEVIL. and Dallas, while at Victoria the period between December 1 and 15 was more favorable. The shelter conditions within which weevils survived was also determined in these experiments, and the principal points are shown in the following table, which again does not include cotton-seed tests: Taste XVI.—Shelter in which surviving weevils were found in April and May, 1906. 3 ; Corn ermuda shucks, old Locality. grass and | Excelsior. Paper. ae cotton Total. hay. deat, stalks, and bolls. Wile tora, Moxteserm same ste cites 5 4 1 1 4 15 (OF bi) a aie! We). ee ae eee ie al See OSE A |Soccine acaroc GG BOOOCGRe ladacpasaacoe 41 41 Dallas WMexse oo sce ssoeeeeee 3) paSeceeeei sls Lae oe tecinsre|lleeecinns see masenetnemeree 3 Mofale x a3sss oC ee 8 4 | 1 1 45 59 This shows the favorable nature of old corn and cotton stalks, among which the survival in one cage at Calvert was surprisingly large. It also indicates that weevils may survive in varied shelter, and that in all probability the temperature and moisture conditions experienced may be as important as the nature of the shelter in determining survival. LARGE-CAGE EXPERIMENTS, KEATCHIE, LA., 1905-6. With the work of 1905-6 a change was made in the method of carrying on the hibernation experiments. Instead of using numer- ous small boxes in a number of places, large screen-covered cages were utilized in the fields at Keatchie, La., and Dallas, Tex. The Keatchie cage (Pl. III, fig. 2) was constructed under the direction of Mr. Wilmon Newell, secretary of the State crop pest commission of Louisiana and special field agent, cooperating in the boll weevil investigations. It was probably the largest structure of its kind that has ever been built for an entomological investigation. The interior was divided by partitions into eighteen sections. The shelter conditions for the weevils and the dates upon which weevils were inclosed were planned to represent the extremes of field condi- tions as to shelter and date of entrance into hibernation. The gen- eral plan of the experiment is shown in the first section of Table XVII, and in the last section are included the emergence records for the cage. Before entering upon a discussion of the work at Keatchie special credit should be given Mr. Wilmon Newell and his assistant, Mr. J. B. Garrett, who were particularly concerned in the execution of the work at Keatchie. Much work has also been done by Mr. W. D. Hunter upon the reports of the Keatchie experiments in arranging the data so as to show the most significant facts. Bul. 77. Bureau of Entomology, U. S. Dept. of Agriculture. PLATE III. SEED HOUSE AND HIBERNATION CAGE, KEATCHIE, LA. Fig. 1—Seed_ house opposite which the first sign of weevil work was found at Keatchie, La., in 1905. Fig. 2.—Large cage built for hibernation experiments in 1905-6. (Original.) ot hea DF LARGE-CAGE EXPERIMENTS, KEATCHIE, LA., 1905-6. 39 Taste XVII.—Summary of installation and emergence records in cage at Keatchie, La. Installation records, 1905. Emergence records, 1906. 3 re = d ne =e = ; g Pats B. E Es 3 March April. May 1-14, q BS Base c| sa = 3 ° = ae a rae Shelter in cage section. ao") Ss Pale eae q Pr) o Oo, o ie] o q o q a2) og °3 rales = Ss 2 8 : sy e| se eee eae 20)) |e Sara Beta a a = = fa PA || i A egal | tee 1..| Louisiana.| Nov. 29 | 1,200 | Brush, leaves, moss, stumps, logs;} 2 | 0.166| 3] 0.25] 4 0. 33 stalks removed. 2..|...do.......| Nov. 25 | 1,000 | Same, but stalks standing........ (Oe = ae 7 aie LO, 1.0 Bes so2dOl cc. e Pe (Ceeeee 1,000 | Cotton seed piled; plants left} 1] .1 4 .4 Oiieeken standing. AE GOe cas onl 5 300 n~o 2: 1,C00 | Same, but seed left uncovered....| 2| .2 5 -5 Oe eeecns Jaen GOP) eae pee Onose= #(000)|) Absolutely bare-...--2- 5.5.21... Us| ait 1 Sal Onieest2 Ga5|-iexas ass NMoven23:) L000) Ordinary field. . 5... 52.2 252.5-22- 5 | 25 18} 1.8 4 .4 Stalks, grass, etc.: Wee bee Oeeese a aN OWmeon |i-2) 100 ATMOS Ul ee ace ce eee 2512 Oe Ay -81 | 16 - 76 See pad Ose oe |eNOVe zo | 15500 ISEUITIOT AS Ne onmta ens ore Sore caanciels PA \VewealeS lei || PEELE als 1.0 ee Eee dO seoeee | eae Ose || 2000 HAMelaS aay eee eae. see cnss Parl gz 9 at) 3 .3 ORS EEE donee | end Oree ce 1, 000 SamMeras ae hee Acciona P HAL ees (Gy) BGS One S53 LI ek ots Co ae al Ieee aa (eee 1, 000 SHAME SNe ve Sar a Aee Seaeabee OVE eee iM |) 260 4 .4 ee | Pend Ose=senei NOV. 25 | (1,000 SAMS Ones aree See ee amen ae On ees TEA ile ee 1) 0 11092 13_.| Louisiana.| Dec. 18 1,000 | Stalks left; leaves, etc., added; | 1) .1 2 By) 1 ai shaded. HAPs ROXAS... 2 Dec. 3 | 4,000 | Same as 13, but not shaded....-.-. CN il 29 TPA At -42 Hse As Sa Cie ease ee 0 (0 eae ASOOON| sam erasnia so ae. a aeemet me os a 9} .22 | 94] 2.35 | 28 ot LOPS doves. Dee: + '8\/ 15000) |/2---. CLONE eA a tones ees il ll 15 1.5 5 -O 17..| Louisiana.; Nov. 28 it(0,0, 0) ees OFLA ea Eee ok Re FS 4) .4 iW) alee al) 1.0 18..!...do.......! Nov. 18 | 1,000 | Check on 13; stalks, grass, leaves, | 0 |.....-- 15e|) ale5 8 -8 not shaded. Ropalsiandiaverages. 25,800) lacs ssesenirnae eceaacte ce aie ae secre ease | 38 LS SSI ee S37 53 Installation records, 1905. Emergence records, 1906. Ss a> | n na } w b= ae iS “ane ean tee Marchlto | 3 | © ae al eS 38 res Maye ee) ae SiS g | Eas) = cate 53 og ae a| 3 Fa | ey | #8| 28 | 23 r= os go » B, Shelter in cage section. a nS a Rl oes a ai 2 Qa 3 Piro R= ellos at Meee 2 | of °3 =| = s oO = = iD | oe cap pole, = Ber il 3 aa cle = i, i, a |e = me | 1..| Louisiana.) Nov. 29 | 1,200 | Brush, leaves, moss, stumps, | 9 0.75 26 2.16 11 logs; stalks removed. 2..|.-.do.......| Nov. 25 | 1,000 | Same, but stalks standing..-.. 17 iy 25 PA 9 Seen Ones. o2|- 5-00... 1,000 | Cotton seed piled; plants left 5 -5 6 -6 16 standing. 4_.|_..do_......|...do.....| 1,000 | Same, but seed left uncovered . i sit 8 8 15 eee dO sc ese 21 dlc .. 1000") A bsoluteliysbaret.\s_- 2:2) 02 2 2 a2 4 4 17 Gea ReKAS! =< Nov. 23 | 1,000 | Ordinary field............/...- 27 2.7 38 3.8 6 | Stalks, grass, ete.: fee eee GOlse... |) NOV. 429) |022100 Samevasallsseo see eerc Miayob see ee sha ee nas ote a eee 1,350.8 1,362. 4 417 48 56.8 87.2 May AG 13 ees cee ee ree as es eee ene 1,526.8 151252 466 48 63. 4 87.2 Miaiy 242235 2208 Sar ae eet a ce BI ee 1,865.8 | 1,812.4 639 55 87.0 100. 0 May? 24-200 S80: BS tee SAS ee ee eee 2,066.8 | 2,009.2 662 55 90:10) |bs2eeeeaee May 30=Jmer hehe cae see See ee 2,479.8 | 2,487.6 727 55 9970) |Paoeeaeee TMING W230 SSS ae ee ee eae eras 3,146.8 | 3,188.0 734 55 100:\0))|23oeecneee Emergence at Dallas became complete with the accumulation of slightly over 1,800 degrees of effective temperature, while at Keatchie complete emergence required slightly over 3,000 degrees of effect- ive temperature. At Dallas 87 per cent of weevils had emerged when 1,512 degrees of effective temperature had accumulated and the same percentage had emerged at Keatchie with 1,865 degrees effective temperature. For the last 13 per cent of weevils emerging but 300 degrees of temperature accumulated at Dallas, while at Keatchie nearly 1,300 degrees accumulated. It is probable that at Dallas during this season the emergence in the cage was completed somewhat sooner than would have been the case normally, on account of the late period of starting the experiments, LARGE-CAGE EXPERIMENTS, KEATCHIE, LA., 1905-6. 47 At Victoria in the spring of 1904 the period of emergence from hibernation was determined in the field under exceptionally favor- able conditions. A severe drought, occurring immediately after most of the cotton had been planted, so retarded germination that the sprout cotton developed nearly two months in advance of the planted. Large numbers of weevils emerged before most of the planted cotton was through the ground. Practically the only food supply afforded these weevils was found in the sprout cotton. By reducing the number of sprout plants upon a field of 65 acres it was possible to examine at frequent intervals all of the plants. Since all weevils found at each examination were collected and removed from the field those found at the next subsequent examination may be considered as having emerged in the interval. The development of squares upon the most advanced plants was not sufficient to make it possible for any weevils of the first generation to have become adults before June 1. The collections from the sprout plants were continued until May 26, and it is probable that some weevils emerged from hibernation after this date. Our knowledge of the weevils at that time was not such as to enable us to distinguish accurately between hibernated and recently emerged adults after that date. For that reason May 26 was considered as representing the conclusion of emergence from hibernation, although it probably continued longer. TasBLE XXIV.—kelation of accumulated effective temperature to accumulated emergence in field observations at Victoria, Tex., in 1904. Accumu- Accumu- Accumu- Accumu- lated ale! Accumu- ee lated number | Percentage lated percentage Periods. effective of plants of plants number of of weevils tempera- | of cotton eb oaeh weevils |2t.each date ture ‘ sprouts to entire found to entire eae d number number © * | examined. found. id Oe NOOO, Te Se CUS SB Baan SE SESE no Benen eae 508. 0 None. None. None. None Mar. US beace 2s aacencneebsbpeaee a aaponeaee 585. 5 250 4,2 19 2.93 UT UDG ee a ee ee Se ean eg Dealsli(are 650 11.0 39 6. 01 LuLSiiy OTR ST Le Re Oat ies CE eee eee See 1,240.0 1,190 20.1 65 10. 03 Apr. U5). odcraconcouswids sehode Gr Sonee an aae 1,378.5 1,720 29.1 100 15. 40 AMO GED ee SS ee ad ee One ee EBS ye) 25120. 35.9 160 24. 60 adore, UGGS. Sa POG ae i a ee Reto oer an 1,656. 0 2,320 39.3 200 30. &C ANfovES AE he ee eae te oe ee ey 2,104.0 2,570 43.5 224 34. 56 WEN FST ea ee Se © Ae Ne ee A 8 Re oe 2,374.0 2,990 50. 6 376 58. OC NEG TIDE IG Se Se oa he ane el 2,584. 0 4,163 70.5 521 81. 0F Wiley PAG Se a ep es See Be Ree ee 2,814.5 5,900 100.0 648 100. 00 A comparison of Tables XXIII and XXIV shows that there was a much greater accumulation of temperature at Victoria for the same percentage of emergence than occurred at either Dallas or Keatchie, although the Keatchie record appears to exceed the Victoria record in the amount of accumulated temperature accompanying complete emergence. It seems very probable that in the field records the accumulations are excessive because of two facts; first, at each 48 HIBERNATION OF THE COTTON BOLL WEEVIL. examination all weevils were considered as emerging upon the date of the examination, whereas in the cages the weevils were collected daily. The second reason is that upon plants in the field there was a much greater possibility of overlooking weevils which were present and which might be found and counted as having emerged upon some succeeding examinations. Table XXIV is, however, of value in supporting the records given in Table XXIII, especially because similarly favorable conditions for determining the full period of emergence in the field may rarely occur. LONGEVITY OF WEEVILS AFTER EMERGENCE IN KEATCHIE EXPERI- MENTS. For determining longevity after emergence the weevils emerging during short periods were placed together in a smaller cage provided with a variety of rubbish but with no food. Examinations of the small cages were made at frequent intervals and the period between the average date when weevils were placed in the cage and the aver- age date of examinations was recorded. The figures are arranged chronologically according to emergence. Taste XXV.—Longevity of weevils after emergence from hibernation, without food, at Keatchie, La., 1906. | | : Average || Average Number Sees 5 Number yea Date of emergence. | of weevils wee a pues " || Date of emergence. |ofweevils bs een Ben steers emerged. ASS ou ays emerged. days. | of days lived. es lived. 1906. 1906. Marchi26een-sencse- 1 62.0 CPO Mulbhye (Gencocenacaass 16 292.5 18.2 Jost NOS Breas ae 44 905.5 i PAM any Sa eters see etiee 16 262.0 16.3 vXy0h all lila eee oe Serres 35 751.0 240) | Mia yelOleeeeeme asses 1 1.0 1.0 PG gl ee ere 29 678.5 23540 eMail ee eesceee 6 54.5 9.0 Atrial Secs cence 8 261.0 S210) Mayle eee eee 5 13.0 3.2 iMprillae sae. here 7 169. 0 SAG eMiavalaaeeseee ee oeee i let) ile Poni Messe 8 eee a 5 100. 5 20.1 || May 8 58.5 | 3 April Geese eeeeere 2 59. 0 29. 5 | 2 26.0 13.0 ADRS Taj ates nae line eee ecci' ee cee eee Mie eee, 13 169.5 13.0 April Oper cscs 2 55. 0 27.5 6 58. 0 9.6 April 20 11 119.0 10.8 4 48.5 eae April 21 9 92.0 10.2 2 23.5 WS 7h April 22 23 378.5 16.4 2 29.0 14.5 April 23 6 132.5 22.0 2 26.5 13.2 April 24 4 36.0 9.0 1 1.5 1.5 Aronia me eere sea 9 83.5 9.2 1 Te) 7.5 sAprili2Geaceee epee 3 24.0 8.0 4 35.0 8.7 ANDI 28 ee oe he St Su 46 855. 0 18.5 1 7.0 7.0 Mprilis0 Sees eee 18 313.0 W723 1 4.0 4.0 May, lise sece sateee | 2 15.0 7.6 Mayi2ie een eeere® 15 173.0 11.5 Totals and Mayas pecunen | 28 431.0 15.3 average... . 418 | 7,155.0 17.11 May 520. enna | 19 342. 0) 18.0 a{n the third column of the table the expression ‘‘weevil-days”’ is used to signify the total number of days lived by the total number of weevils recorded for a certain date. For example, if one weevil had lived 10 days, a second 15 days, and a third 23 days the total number of weevil-days for these 3 individuals would be 48 and the average number of days lived would be 16, It is noticeable that weevils emerging early in the season survived far longer than the average period, while those emerging toward the end of the season survived for less than the average period. For the 418 weevils tested the average duration of life without food proved to be slightly over seventeen days. LARGE-CAGE EXPERIMENTS AT DALLAS, TEX., 1905-6. 49 LARGE-CAGE EXPERIMENTS AT DALLAS, TEX., 1905-6. The work at Dallas for 1905-6 was planned especially to check the results of the experiments at Keatchie which have been described. The cage used (Pl. IV, fig. 1) was divided into four sections, each having a ground area of 100 square feet. In one section the natural conditions of shelter were left unchanged (Pl. IV, fig. 2). There was practically no grass upon the ground, but the growth of stalks was quite heavy. In the other three sections the shelter provided (Pl. V, figs. 1 and 2) for the weevils was arranged in such a way that it might be possible to divide each section into two parts by a middle partition. Unfortunately the first cold weather occurred before the weevils could be placed in these sections, and it was neces- sary to keep the weevils confined in boxes for several days until it became sufficiently warm to render them active so that they might find shelter in the cages. The weevils were liberated at approxi- mately the center of each section and allowed to move in any direc- tion they might choose. The object of this was to determine whether particularly favorable rubbish might exert a special attraction for the weevils. About three weeks after the weevils were liberated an examina- tion was made of each section and the number of weevils crawling actively upon the wire was determined. An examination of the boxes from which the weevils were liberated and which had been left undisturbed in the cages during this period showed that a large mortality had occurred before the weevils really entered hibernation. Table X XVI shows the principal points in regard to the beginning of the experiments and the emergence of the weevils during the following spring. TaBLe XXVI.—Large-cage experiments in hibernation at Dallas, Tex., 1905-6. sed | Weevils Percent- | Percent- Active | found | ageot | ago-ot | Dato! | Day of Section ze saree Weevils | i? | dead, | weevils | living anees of cage Kind of shelter. putin. | Decent: | Decem- | active, | among | ©™er omer: Re | ber 26, | Decem- | those ex- SOE O06. eek | 1905. | ber, 1905.| amined. ae : i Sato ee Cotton stalks...... 2,600 375 615 14.4 | 38.0 | Apr. 4] May 2 ; Pt. 1...| Cotton stalks re- 2,500 200 | 515 8.0 28.0 | Mar. 22] Apr. . 9 moved March : 22, 1906. | Vig od Al COforiZeyat Rie ALPE Tayo lal Mae ke SL a a a a eee ee ee Apr. 4) | Apr ait leaves. | | 580 pales NBATOLe sense oon SS 2,500 260 1,205 10.4 | D727) Apr. 23; |\-Aipr. 923 = JPlip BS 3) TRIER as ce eee Ske ent eee bec See at [a ee labocensee May 14| May 14 Pt. 1...| Piled boxes....... 2,500 238 | 1,625 9.5 12.7] Apr. 4| Apr. 11 LPL BAS eoal A Cror malay a¥o lf eceLoy f oyaty| [Ay ant oh pk | ee eee BH (ie ey gn (ee Ee eas a Apr. 9| Apr. 9 stalks. Total and 10,100 1,073 3,960 10.6 21% average. 90317—Bull. 77—09——-4 50 HIBERNATION OF THE COTTON BOLL WEEVIL. Taste XXVI.—Large-cage experiments in hibernation at Dallas, Tex., 1905-6—Con. Emergence by periods. g y Pp Per Hank ear | Total | °°" | cages Been Kind of shelter. sur- | "© | on OSCE Se Mar. | Apr. | Apr. | Apr. | May | May | May | vival. oe basis 22-31.) 1-10. |11-20.|21-30.) 1-10. |11-20./21-31. 2 ofsur- vival. sell 1 ee ae Cotton'stalkseeeeseece: 0 1 2 4 4 2 0 13 || 05 2 TT: Pt.1...| Cotton stalks removed 2 3 0 3 0 0 0 8 | 1.04 4 March 22, 1906. Pt. 2...) Cotton stalks and leaves... 0 6 7 3 1 1 0 Ss | eee 1 Ill: Piteet Bare ees ae ents eee tee 0 0 1 0 0 0 2 12 5 Pt. 2 HAY? este pee eee 0 0 0 0 0 1 0 is pen 7 LV; Rial eee | eeiledsboxesee= esse esas 0 4 SH 2 07 1 2 128 eDO) 3 Pt. 2...) Corn and cotton stalks... -- 0 2 0 | 0 0 0 0 7p lees Sr 6 Total and average. -- 2 7 ate 13 5 5 2 56 5 The division of sections 2, 3, and 4 was made by inserting a par- tition of cheese cloth early in the spring of 1906 before any weevils became active. The percentage of survival has been based upon the total number of weevils placed in the four sections: It should be borne in mind that the conditions at the time of entrance into hibernation were decidedly unfavorable for the weevils, as is shown in the fact that about 35 per cent had died before December 26 and under such conditions as to indicate that they were very weak at the time they were placed in the cage. No allowance has been made for the escape of weevils through the wire. It thus appears that approxi- mately 1 per cent of the weevils which really may be said to have entered hibernation survived and emerged between March 21 and May 31. The survival in the bare section was less than one-fourth of the smallest survival in the sections provided with rubbish. For the sake of comparison with the records at Keatchie, La., some data from the Dallas experiments have been used in connection with those at Keatchie in several of the tabies which have already been given. NATURE OF WEEVIL ACTIVITY FOLLOWING EMERGENCE FROM HIBER- NATION. In following the activity of emerged weevils it was deemed advis- able to pursue a very different method at Dallas from that which has been described at Keatchie. Instead of removing weevils from the sections in which they had emerged, each weevil was marked in such a way as to make it possible to recognize it individually and the weevils were allowed to remain practically undisturbed in the sec- tion where they had spent the winter. In making the daily exam- inations record was kept of the appearance or disappearance of each individual weevil. No food was supplied in any of the sections until Bul. 77, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE IV. HIBERNATION EXPERIMENTS, DALLAS, TEX., 1905-6. Fig. 1.—Four-section cage used for experiments, built over cotton. Fig. 2.—Shelter conditions as occurring naturally in section 1. (Original.) Bul. 77, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE V SHELTER CONDITIONS IN DALLAS, TEX., EXPERIMENTS, 1905-6. Fig. 1.—Piled cotton stalks and piled boxes in section 2. Fig. 2.—Standing cotton stalks versus piled leaves, section 3. (Original.) Aa t on Ta cer LARGE-CAGE EXPERIMENTS AT DALLAS, TEX., 1905-6. DL toward the close of the experiments in May, when seed was planted and cotton began growing before the last weevils emerged. Some very interesting results were obtained from this method of observa- tion. A majority of the weevils were seen a second time, and some disappeared and reappeared as many as eight times. The longest period between the first and second appearances of any individual was forty-three days. Taste XXVII1.—IJntermittent activity of unfed weevils after emergence, at Dallas, Tex., 1906. ee a: D2 Weevils ‘‘rehibernated ”’”— 5 3 Number of weevils seen— aan — ———__——| A Once. Twice. Three times.| “e 2 om — — She) | - | Payee lt Meee al S36 na an | | 2 2 g lb eo | = og | ae 5 | ao 43 =| ie. || i a o® mete |!» sed AS| 4 6 3 o | o | 2 Spe 7 | fo} 8 A eRe Sites al | Se ¢/¢q|¢|¢ cae o 22 oD | 8 2) = ) S| z \) & | eels | S| LE lapegiee Wetepe | Te SIRO ee ee oe eke ine Smee ie | eae ee ele: fea le loa. oe) ie Pe “oe |e | Ke a 2 = 5 ae re 46 26 a ie 6 2 2 1 17 8.7 a (ee 2 BF): OS As has been previously shown, entrance into hibernation is a gradual process and weevils which have first become quiet may sub- sequently become active and seek other shelter before finally hiber- nating. In a very similar way emergence from hibernation is gradual but extended throughout a longer period of time than is entrance into hibernation. The observations recorded in Table XXVII also show conclusively that weevils may leave their winter quarters during warm days and, failing to find food, they may again become quiet and emerge again after a considerable interval. This fact has an important bearing upon the proposition which is fre- quently advanced by planters of starving the weevils in the spring by deferring the time of planting. While many weevils might perish in this way, it is certain that many more would be able to survive and reappear at intervals, so that there would be plenty of weevils to infest the crop, even though this might be planted as late as is possible to secure any yield. Other observations were made upon the intermittent activity of unfed weevils during the spring of 1906. Weevils from Calvert, Victoria, and Brenham, Tex., were tested. The weevils from Cal- vert and Victoria, Tex., had been confined in hibernation cages throughout the winter. Those from Brenham were collected in the field early in March. None of these weevils had tasted food after emergence. In these tables the date of death, unless otherwise indi- cated, is considered as having been the middle date between the last examination at which a weevil was found alive and that at which it was found dead, 52 TasLe XXVIII.—Jntermittent activity of unfed emerged weevils, 1906. HIBERNATION OF THE COTTON BOLL WEEVIL. When r : Date of enn When Wien! removed Whee Weevils first ex- Locality. eollected put in hi- rromeis rehiber- | put in rehi- sata ~~" | bernation. | y¢mation nated. bernation. re out 1905 1905 1906 1906 Calvert; Tex..22 sete eeee eee Nov. 25 Neve 27) Apr. 19 | Apr. 23 20| May 10 Toatoria. | Nov. 7,13 | Nov. 7,13 }\ , lea Victoria, Tex... 2 232-52 eeeceeee {Den Teel ioe, cilil \Apr. 63), Apres.) 16 7 | Apr. 24 1906 Brenham), Mex ees sees sere eee Noy. Hillis ro cere tee Mar. 1 | Mar. 7 8| May 11 i Average Weevils | Date of | Weevils | Date of | weevils | Date of length of rie ah second : third death of an Locality. inhi | Aer || Sime | ascaear. || Sbbeahye || aoa life in ing. ere ing. Sere ing. BES rehiber- nation. nation. survival. mation | Days. G@alvert, Dex cs.nt occu ese 10 | May 22 6| June 8 | 0| June 8 30.4 Wictoria exe. 2o6 sae. mcesteecee 3 | May 10 ON eee Re pe Netese May 10 19.1 Brenham lex.) s5 oe eee ae 2| May 23 1} May 31 0} May 31 67.4 The records for Calvert and Brenham show a very remarkable power of endurance in some weevils, the average survival for the two lots of 20 and 8 weevils being over thirty and sixty days, respectively. CLIMATIC CONDITIONS PRODUCING EMERGENCE FROM HIBERNATION AT DALLAS, TEX., IN 1906. In the figure given below, representing climatic conditions and the emergence at various dates, the temperature line given repre- sents only the mean average effective temperature. In this case, as at Keatchie, the emergence occurred especially dur- ing four well-defined periods and the conclusions stated in connection with figure 1 apply equally well to the results shown in figure 2. EMERGENCE IN THE FIELD AT VICTORIA, TEX., IN 1906. The observations upon emergence in the field at Victoria, Tex., in 1906, were begun too late in the spring to indicate the limits of the first part of the period of emergence. For this work a field of about one-half acre was selected in which it was apparent early in May that there would be a large number of hibernated adults. The observations were planned to furnish information particularly upon two points under field conditions: (1) The determination of the period of emergence and (2) the period of activity of emerged wee- vils. The work was done by Mr. A. C. Morgan, who devoted par- ticular attention to a study of this field throughout the season of 1906. The method followed was to examine every plant and every square or boll throughout this area, After the first two examina- EMERGENCE IN THE FIELD AT VICTORIA, TEX., IN 1906. 583 tions had been made it became apparent that some method must be adopted to enable the weevils found at each examination to be dis- tinguished. At each subsequent examination, therefore, the wee- vils found were marked with a paint of a different color. Early in the season the weevils emerging from hibernation were sufficiently numerous to practically prevent the setting of fruit upon this area. The first weevils of a new generation did not begin to appear until APF/L [a el ECS ee ee Ja eae eee ey, DEGREES e's Eee eerie pee >) NUMBER OF WEEVILS EMERGED ph VERAGE TEMPERATUF: i) PRE oe an PC 2 Dee | eS Fig. 2.—Chart showing mean average temperature, rainfall, and weevil emergence, Dallas, Tex., March to May, 1906. about June 20. It was then easily possible to distinguish between hibernated adults and those which were not more than two or three weeks old. It is probable that the oil paints which were used may have been responsible for the death of many of the weevils marked, since it was hardly possible in the field to apply the paints with the necessary care. 54 HIBERNATION OF THE COTTON BOLL WEEVIL. Taste XXIX.—Emergence records for one-half-acre field at Victoria, Tex., 1906. Number of weevils found. ato axamina- so] Ke ue) so] * Date prexamine 2 Os! s = Ey Rerianicel : & aS Aq Ade as = Ho en HD =2 =I 3 oe ac 3X a aq a oo p S = = aa 1906 ot IW SS | Vxee I] Mayu Que as ae sates BO ere see noe sce nace ....| 3846 | Weevils not removed. May Q5ep cee sees 35S | ays | A | eee a |e FEA 358 Do. May 28.a JUNE B=He = sees see On ee Eee See brocc (eeee ..--| 492 | Weevils marked yellow=492. June sas eerese ene 22G60\12001| eee eee eee | eee ..--| 355 | Weevils marked blue=226. June 23-July 5..... 165 | 27) 9|18] 9|..-..|..-.| 228 | Weevils marked red=87. Tuly23—26 see ee see | 731! 3] 0] O| 1] 2] 2] 739 | Weevils marked white=78. Totale=soen=- 2,318 |159 9 | 18} 10 2 2 |2,518 a Righty-seven weevils removed from field May 28 for other experimental work. It is evident from an examination of the number of weevils found that the number in the field increased steadily until after June 5. Between June 5 and 13 a large number of previously marked weevils appeared, all of which were undoubtedly hibernated. The very small number of first-generation weevils which was found upon the examination made between June 23 and July 25 was due primarily to the exceptionally severe hot dry weather which had prevailed for several weeks. The gradual decrease in the number of living hiber- nated weevils was greater than the increase in the number of first- generation weevils. During the period between the middle of June and the middle of July the plants rapidly increased their fruiting activity and there was a decided decrease in weevil injury. It is interesting to note that in spite of the large number of hibernated weevils occurring in this field, which threatened early in the season to prevent entirely the setting of fruit, the weevil injury and devel- opment were so checked by the heat and drought that after the middle of July these plants set fruit rapidly and the field produced an average yield of cotton. The most plausible explanation of the late period of emergence for weevils found in this field is the existence in its immediate vicinity of a large number of trees which were loaded with long Spanish moss. (See Pl. II, figs. 1,2.) The explanation of the effect of this moss in producing late emergence from hibernation will be considered more particularly in connection with the cage experiments in hibernation for 1906 to 1907. LARGE-CAGE EXPERIMENTS, 1906-7. 5o LARGE-CAGE EXPERIMENTS, DALLAS, CALVERT, AND VICTORIA, TEX., 1906-7. PLAN OF EXPERIMENTS. Profiting by the work done during former seasons, plans were made by Mr. W. D. Hunter, in charge of the investigations, for much more careful and extensive work during the winter of 1906-7 than had ever been undertaken. Three localities for the experimental work were selected representing in a general way the northern, central, and southern sections of the State. In these localities, also, much work had previously been done and the results for more than one season could therefore be used in a comparative way. At Dallas, Calvert, and Victoria screen-covered cages were erected, each being 20 feet wide, 50 feet long, and about 64 feet high. (PI. VI, figs. 1, 2, and 3.) These cages were divided into ten sections by partitions, each section having a ground area of 100 square feet. The three localities selected offered a considerable range in geographical and climatic conditions. Each section of the cage was provided with a door opening to the outside through which access could be had to a section without disturbing the conditions in any other section. It was planned to provide similar conditions of shelter in corresponding sections and to confine weevils in corresponding sections at as nearly the same date as mignt be possible in each of the three sections. The weevils used were collected in the immediate locality where they were placed in hibernation. In this way it was anticipated that data might be obtained bearing especially upon the following points: (1) The effect of the time of entrance into hibernation upon the survival of weevils. In the experiments first started it was necessary to force entrance into hibernation, if possible, or starvation by the destruction of the food supply. The geographical range was expected to increase the interval between the beginning of the experiment in each locality and the time when weevils would normally hibernate. (2) The effect which the complete destruction of food supply at varying dates might have upon the success of hibernation. For these experiments the shelter conditions were as uniform and as favorable as it was possible to make them in the different localities. It was hoped through these tests to determine the minimum interval which must elapse between the destruction of stalks and the successful hibernation of the weevils. (3) To determine the effect of exceptionally favorable and unfavor- able conditions of shelter upon the hibernation of weevils placed in the cages upon the same date. It was intended that the shelter conditions provided should be so exaggerated as to represent the extremes of conditions which might naturally occur in the field. 56 HIBERNATION OF THE COTTON BOLL WEEVIL. (4) To determine the effect which different depths and classes of shelter might exert upon the success of hibernation and also upon the time of emergence and the range of the emergence period. (5) To test the power of adaptation which the weevils might have acquired to varying climatic conditions by bringing weevils from widely separated localities for comparison with weevils collected at Dallas. In each test similar conditions of food and shelter should exist in each locality. (6) To determine upon a large scale, in very widely separated localities, the proportion of weevils entering hibernation which might survive. (7) To determine the relation between climatic conditions and the emergence period in each locality. To provide suitable and reliable data for this study, standard Weather Bureau instruments were secured and temperature, humidity, rainfall, and other records were kept in each locality throughout the period covered by the experi- ments. (8) To determine the longevity of hibernated weevils, especially after emergence. Since all weevils used in this work were collected promiscuously in the field immediately preceding their confinement in the cages, all figures showing their longevity must be based either upon the date when they were placed in hibernation or upon the date of their emergence. In the latter case it would be distinguished as longevity after emergence. It was planned to use from 2,500 to 3,000 weevils in each section of the cages, although difficulties in the collection of the desired number for the particular dates when experiments were to be started occasionally caused some variation in this number. Adult weevils only were used in sections 1 to 9, inclusive, in each cage, while in sec- tion 10 the hibernation of weevils in bolls was tested. One-half of the bolls were buried under 2 inches of dirt. The other half were exposed upon the surface of the ground. (PI. X, fig. 1.) It is generally understood that the principal factor producing a hibernation period is the lower temperature occurring during the fall and winter months. Jn its effect upon the survival during this period moisture is also an important factor. As a rule, in studies of these factors investigators have been obliged to rely upon the climatic reports published by the United States Weather Bureau for the par- ticular locations desired. It happens frequently, however, that there may be no report from the Weather Bureau for-the particular locality desired. Both temperature and rainfall are liable to con- siderable variation within comparatively short distances. In order that the data for these studies of the hibernation of the boll weevil might be complete and thoroughly reliable, we have kept full climatic records in the immediate vicinity where experiments and cage obser- Bul. 77, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE VI CAGES FOR HIBERNATION EXPERIMENTS IN TEXAS, 1906-7. Fig. 1.—Dallas, Tex., cage on flat, black-waxy land. Fig. 2.—Calvert, Tex., cage on slightly sloping, sandy land in post-oak region. Fig. 3.—Victoria, Tex., cage on sandy-loam slope between bottom and upland. (Original.) LARGE-CAGE EXPERIMENTS, 1906-7. Sit vations have been made. The instruments used are of standard Weather Bureau type (PI. I, fig. 1) and, as the records extend over several years, reliable data have been secured upon the following climatic factors which may affect hibernation: Maximum and mini- mum temperatures supplemented by a continuous temperature record made by a recording thermograph; the actual rainfall as meas- ured in a standard type of rain gauge; the atmospheric moisture exist- ing at 8 or 9 o’clock a. m. and 5 to 6 o’clock p. m., supplemented by a continuous record of the moisture in the air furnished by a hygro- graph. TABLE XXX.—Outline of hibernation experiments in 1906-7. Date of starting experiments | No. in 1906. ot See | Character of shelter supplied. Food supply. Dallas. | Calvert. | Victoria. | | 1 | Oct. 13 | Oct. 13 | Oct. 25 | Leaves and grass, 4 to 5inches --..} Allfood removedafter two days. Aa OCh mG OCha Ol dO meee (6 (ESP Sees Meee eee ae Stalks cut down and left to dry. 2} Oct. 19 | Nov. 26 | Oct. 28 |....- (0 LEP FES ee er eee ee Allfood removed after two days. 7 | Oct. 25 | Oct. 25 | Nov. 6 | Spanish moss hung on string at | Stalks cut down and allowed to top of cage; loose bark on dry. ground. 8 | Oct. 31 | Oct. 31 | Nov. 10 | Leaves and grass 4 to 5 inches | All food removed after two days deep. SreNov.. <6) Novi, 5) | Nov. 14 )2.-2- GOP St name tee oe iste ys since Cotton cut down and allowed to dry. 3 | Nov. 12 | Nov. 14 |} Nov. 21 | Leavesand grass, 2inches......- Do. SII) eee oe eee NOV Zils adores Leaves and grass, 10 inches. .....- Do. 6 | Nov. 28 | Nov. 25 | Nov. 28 | Ground absolutely bare. ....._-- No food supply. 10 |} Dec. 6] Dec. 3 | Nov. 29 (2) and 10 a Tn this section, 3 bushels of probably infested bolls were exposed on the surface of the ground in one half of cage, and 3 bushels were buried under 2 inches of dirt in the other half. The dates given in Table XXX are the actual dates of beginning the experiment in each locality. The arrangement of the experiments shown in the table is primarily chronological, without regard to the sequence in the number of sections. Some knowledge of the plan of this work is essential to a clear understanding and a correct interpreta- tion of the results obtained from it. CLIMATIC CONDITIONS PRODUCING HIBERNATION AND ACTIVITY OF WEEVILS DURING NORMAL HIBERNATION PERIOD. The climatic records are started with October 1, 1906, in order to show a comparison between temperature conditions under which weevils are normally very active with those under which they become inactive. The termination of what is considered as being the hiber- nation period is rather arbitrarily set at the time when weevils begin to emerge in considerable numbers. It should be stated that in each locality the climatic records for the winter of 1906 were very unusual. The principal points of variation will be noted in subsequent para- graphs in their most important connections. In each chart (figs. 3-5) showing temperature conditions it has been deemed advisable to show only the line representing the mean average temperature. 58 HIBERNATION OF THE COTTON BOLL WEEVIL. While it is probable that a study of maximum and minimum tem- peratures is really more accurate, from a scientific point of view, the mean average temperature, representing one-half of the sum of the maximum and minimum for each day will be sufficiently exact and a more simple manner of expressing the relationship existing between temperature and weevil activity. The significance of the term ‘effective temperature ”’ has previously been explained (p. 24). Upon the temperature charts the line representing 43 degrees is therefore exceptionally emphasized. Wherever the temperature line is above this point it represents effective temperature. Whenever it falls below the 43-degree line it is possible that frosts may occur if other atmospheric conditions are coincidently favorable. Whenever the minimum is noted to be 32 degrees or below, the actual temperature occurring is given in its appropriate place upon the record. When the temperature rises above 80 degrees, establish- ing a new maximum, the occurrence is also shown by the actual record given upon the charts. Since it is impossible for weevil emergence to occur at any temper- ature below 43 degrees, that point is considered as initial in the lines giving the records of the activity of weevils. The actual number of weevils found active at various dates is shown at the top of the line in each case. ENTRANCE INTO HIBERNATION. In each locality there occurred a considerable decrease in tempera- ture during the month of October, the mmimum being reached about the 31st. This, however, was not sufficiently cold to cause weevils to hibernate in considerable numbers. During the following two weeks the temperature ranged as high as the average for October. After November 15, however, there occurred a very marked fall of tem- perature, the minimum even as far south as Victoria establishing itself at about 25 to 27 degrees. All cotton was killed by this freeze. The count of weevils found active early in November indicated merely that few weevils had entered hibernation at that time. Fur- ther counts, made about November 30,showed that even so severea drop in temperature as had occurred did not immediately drive weevils into hibernation. During the succeeding two or three weeks the temperature again ranged fully as high as durmg October, and apparently many weevils which had sought shelter after the freeze of the night of November 19 again became active. This was indicated by the large number of weevils found active at Calvert and Victoria about December 10. About the middle of December another period of low temperature occurred, which was followed by decreased activity among the weevils, many of which did not, even then, seek shelter. During the first three weeks of January the exceptionally warm weather experienced throughout Texas drew a considerable number 5G LARGE-CAGE EXPERIMENTS, 1906-7. DECEMBER FEBRUARY 10152025 fe) er) oa x S = yj & nN w ) y & M Q ¢ RK xX t by 8 ey ae SC Los Sane dene Fy i i ee 2 ee MEAN AVERAGE , 0.50 |). Seep Shine Tee aaa eae eee ee O50 e oA EU OS || | Pa Pe ed FP Fig. 3.—Chart showing mean average temperature, rainfall, and weevil activity, Dallas, Tex., October, 1906, to March, 1907. HIBERNATION OF THE COTTON BOLL WEEVIL. 60 “LO6T ‘YorIe 04 “Q06T ‘10q0400 “xa, “WoATeD ‘AIATIOR JIAVAA puR ‘[[RJUIeI ‘oInzeiodure] osvIAR ULEUL SUIMOYS WLYO—F “DIA nod TINGE SIHIN) NI TTRIN: o ay SZHIN/ NL 7 : Ss 2 $2 RF & aie Ha FAL Ve FAN ZL 0 8 NY m y : mN NS ins o 8 N NY MIFHNFSAH GS SFITALIA oe St ol YSIGWIIII SAFIN ZFAON 61 LARGE-CAGE EXPERIMENTS, 1906-7. NOVEMBER DECEMBEF SANUARY FEBRUARY 100 (OmeISeereO mere) 5 (Oe Saee Ones [Oem Sime20 1Sieeed 29 dead '/ deaa rue —-4+—-—-4 7/7924 D8alive I5deap 95 BESEeR SS Se Rew ese eae eee eee ees 90 B | s oS EEVILS ACTIVE I | a o We SSS ~ | SEE Eee eS Se ee eee bok TEST Re Ps Fa aE Fs a Se (SEZ Seen (SE sai P| Fig. 5.—Chart showing mean average temperature, rainfall, and weevil activity, Victoria, Tex., October, 1906, no March, 1907. 62 HIBERNATION OF THE COTTON BOLL WEEVIL. of weevils from shelter. During the last week of January and the first week of February the lowest temperatures of the winter occurred at Dallas and Calvert. The counts made immediately after this period showed the smallest number of active weevils recorded at any time during the winter for those two localities. At Victoria the tem- perature was not sufficiently low to produce any marked decrease in weevil activity. During the remainder of February there was a rather steady rise in temperature throughout the State and many weevils continued active. The figures show that during the last week of the month considerable numbers were emerging from their winter shelter; and beginning with March 1 the period of general emergence is considered to have begun. While these three charts show plainly the conditions existing during the winter of 1906-7, proving beyond question that during this season there was no such thing as complete hibernation of the boll weevil in Texas, it must not be understood that this is frequently the case. Noothersuchseason has occurred since the weevil entered Texas. As arule, hibernation is complete during the period of from four to six months. It is certain that weevils may continue their activity throughout the season wherever climatic conditions are not sufficiently severe to entirely destroy the growth of cotton. ACTIVITY DURING NORMAL PERIOD OF HIBERNATION. The general impression as to the activity of weevils during the normal period of hibernation has been shown in figures 3 to 5. A summary of the records for the three locations, with the temperature conditions prevailing at the time of each examination, is shown in Table XXXT. TasLeE XXXI.—Aetivity during normal hibernation period, 1906-7. DALLAS. Weevils counted in section— Total Terres P weevils ; We =a : r | coun anes TM FOR ane Paina eee fC Pe am | 10. | ©4- | Max. Mean, 1906. | oF. oan INOW) Die cre eee 230) | 290 a eeee ae NOD ere eee SL Di ee eee ee terete steentne 937 79 64.0 INOW Ose eos | 62 | boa (IS ee I a Lo cee ne eecions fseasoc||odeint s||-oa¢58 158 86 67.5 DO wa Ne Ps 4 TIT arouse eke Seeks 1 pa eee ane Uy eee Joos Seellosorce 28 51 38.0 IN OWA 28ers Jae eee aber 130 il Donleeene. a eh Be cells eee 175 62 | 54.0 Dees 2s ie ee 5 ae 19 2 Gy eee 9 ita 12 114 66 48.0 IDCs Diss Seas aos 8 | 10 48 5 JOIN | eveicre lc 8 7 19 | 25 150 73 64.0 1907 | Jani eee ee 9 18 39 Uf DO ialleeie se 7: 13 11 43 80 248 75 69.5 Achat ee a ee 15 24 68 15 Ben |lsraraes | 15 15 55 70 310 82 68. 0 ViaMes2e esata ocean 4 D 255) 3 17 21 45) Sere 16 14 109 73 48.5 Helos Leek ee aes 1 4 hi) 2 | 9 4 4 1 Pi 2 54 64 45.0 Repos see 33 4 7 3) 21 7 | 14 5 50 9 123 80 65.0 Motes! 341 {S86 3H | 140 18S 32 386 | 57 217 218 | a2 406 hh — 22 eee a This total represents 7.8 per cent of all the weevils put in the cage. LARGE-CAGE EXPERIMENTS, 1906-7. 63 TaBLE XXXI.— Activity during normal hibernation period, 1906-7—Continued. CALVERT. Weevils counted in section— Total eg weevils) ss Date. = count.) —<$<$<$<<$——— Perea den lees We. | ol teeenGs, utd | Ol Ives: | Mean. 1906 oF | oF iti nea leg ee 7 averse liek eee Danaea le te |. Gil Set Gl | seme tenet ne AGT be eens MovIge4. 06 le. 3] 214 | 55 9 Gales. Bll i) |W) WES) eee TGS REE FS ap Mee oo ees 4| 47 4 Suis] o| 17| 69 i 397 | 60 | 48.0 1907. RY raripecliaenan es 0! Ne TG WAESt Nh Metall tah) Ol. 90 S11 mls eb 0 2 299 | 82] 70.0 Waneeiptes cess: 8 ll Bo ee 7 ma GS 2 4} 20 1 159 | 62! 47.0 Ufa Gs eae ee aN tee 13 7 1 gil) ey 1 Bia ly 1 86 | 56) 39.0 Metin. see 3 Bil betas 5 0 1|, 28 1 4| 21 0 75| 75 | 52.0 1a a ifaleets 6 Op meen eas ll 9 2| 22 0 91| 79| 62.0 OS ae Bei KG) | 0 2| 36 1 Ne pie 0 69| 74| 65.0 Total........ 46| 407| 171) 61| 272| 514| 44] 216| 349 FP te eee (ee VICTORIA. 1906. Nominee ahs. 139) 200 ec. s4 (IG\s]-| seat | SON he | HRs el sees A 496 | 74] 66.5 TDYS 11 4 eae a knee B15) Od | ee. G4 | 1546)| g23) | 0 oad 1,782 | 73| 59.5 Dic, eee eo ie ly tel ee ed Pe iT fee ae lps (od age |e 236 | 19 418 | 47| 40.0 WGI ON ec . SG ea ease 66 | 186| 8i| 18| 200|...... oo 708 | 65| 51.5 1907. | See ae Ue TOR Rectal ne Uae ge Ral rats silted Pil 134 | 253 | 77| 73.0 sat (eae aie 1A Gel ee8O) |e Dike ote. PGB! bis oes ioe ea [tte pe 404| 77| 72.0 peels tees | 68)| 50: 423 27 | 69'| 76) 16 | 106) 189] 5 729| 66] 52.5 Tas) cu eee ge eah 48| 55| 89| 40] 85 | 46| 43| 67| 123 3 599 | 60) 50.0 Meh Asses Bor ea40i|_/- 90 | ON 650) 46.) ~18:| 20/74.) 8 442| 74! 62.0 RahenGe cease es 205 |inOR tte 7oAl| ABhhes (664)') BU.) 7.50! | uc. {Smoke el ae 312| 70| 66.5 Potale ss... - 562 | 561| 994| 388| 975| 386 | 209| 948 /1,079| 41(|66,143 |......|.....- | | a This total represents 10.5 per cent of all the weevils put in the cage. b This total represents 27.7 per cent of all weevils put in the cage. It is hardly probable that a majority of the weevils may have been counted upon two or more dates, but the fact that dead weevils were found clinging to the wire (PI. VII, fig. 1) at the time of each examination indicates a considerable mortality among the active weevils and that the places of the dead ones in successive counts were taken by weevils which had become active since the preceding examination. The percentages of active weevils for the three local- ities show a rather significant difference, and are given for the sake of this comparison without presuming to state correctly the actual percentage of weevils placed in hibernation which remained active during the winter in the respective localities. At Dallas the 2,406 weevils counted during the winter constitute 7.8 per cent of the total number placed in hibernation. At Calvert the 2,085 active weevils constitute 10.5 per cent of the 19,408 placed in the cage. At Vic- toria the 6,143 active weevils constitute 27.7 per cent of the 22,463 in the experiment. Since approximately the same number of exam- inations were made in each locality the differences in percentage indicate in a general way the relative activity in these sections of 64 HIBERNATION OF THE COTTON BOLL WEEVIL. the State. Thus at Dallas 8, at Calvert 11, and at Victoria 28 out of every 100 weevils placed in hibernation might have been active during the winter. Of course, it is likely that many weevils were counted twice. On the other hand, to counterbalance this duplica- tion in the number recorded, it should be stated that undoubtedly | many weevils were active at intervals between the counts which were either upon the ground or had returned to the ground before the examinations were made. Only those weevils which were found crawling upon the wire covering of the cage were recorded. The temperature conditions as shown for the dates of examination indi- cate that there would be no physiological difference in normal weevil activity upon those dates. The sectional totals indicate that vari- ations in the class of shelter in the different sections exerted little, if any, effect upon the activity of weevils during the winter, with the exception that Spanish moss seemed to keep more weevils from becoming active than did any other shelter. WINTER ACTIVITY. In most instances when the active living weevils were recorded those which were found dead clinging to the wire were collected and counted for each section. Undoubtedly a great many weevils fell from the screen before or after dying, so that the records are very conservative in showing the mortality occurring between exam- inations. These records should be considered in connection with weevil activity, since the collection of dead stages prevented their accumulation upon the wire, and the number found at each exam- ination must be considered of those surviving and remaining on the wire from a‘preceding examination and those which emerged subse- quently thereto. TasBLE XXXII.—Summary of winter activity as shown by counts of dead weevils. DALLAS. Number of dead weevils found in section— ' Total a x = ts num- | | ber Date. | of 1 2 ile anne 6 oral as 9. | 10 Gee | | vils. | | = é ie = = aa DE | BES: 1907. | | Januanyibs te acess et eee eee ee 2 2 || an 1 Bah | ators 10 7 10 4 75 JANUALY 122 eee eee 0 UN epee al eee 7A Eee ee eeean peli ten Silks, 3\ 3 VANUATYL2Q4 Aes Seperate orate pte ete 2 2 Ps Spee 2) (GOT 25 | Aer |e ey 2 5 | @ 687 MEDEA Dae eee a eee | 1 3 | 4 | 1 5 7 3 iy 6 7 38 Hebruary 19. 22 ss. sce cheieeecee eae picts ees 3 1 3 5) Die $e | 3 | 1 13 Total). bane eee eee 6) giles |) 3 46 | esor lle adie ya) eat ei ie | | | a Of these, 622 were on cloth on ground, having fallen from the wire. -b This total represents 2.6 per cent of all the weevils put in the cage, Bul. 77, Bureau of Entomology, U.S. Dept. of Agriculture. PLATE VII. SHELTER CONDITIONS, DALLAS, TEX., CAGE. Fig. 1.—Active weevils trying to escape through wire on October 20, 1906. Fig. 2.—Section 1, in which weevils were placed October 13, 1906, 2.61 per cent surviving. Fig. 3.—Section 4, started October 16, 1906, 4.07 per cent surviving. (Original. ) Beare a) Me a a LARGE-CAGE EXPERIMENTS, 1906-7. 65 TasLe XXXII.—Summary of winter activity as shown by counts of dead weevils—Con. CALVERT. Number of dead weevils found in section— Total num- ber Date. aot % ea 1 2 3 4 5 6 a 8. 9 10 ae vils 1906. MNOVeMmbeLr Wie )s Soto s oe Seeks SB eslale DOI Ee cetsecisase 36 Cha] Bapaac 6 47 293 MMOVEMIDER 29" ies enc sso beece sec 14 2 101 il 39 1 2 20 220 ID yereres call 0%) oO OCS Sees 1 3 16 7 5 2 0 4 47 1907. Meee Mye M4 ey een Sata secciec cee tae 5 4 3 2 5 10 0 3 10 1 43 emipretayae ley. be cata Sse avmcilos aa = OM eeate 128 | Svein 5 12 0 0 6 0 35 USN BIN, 216 oe oes osterascesseedss Ul gees elleceose Ui eee Sec|5oscse 0 O} Emer 0 | 1 IMelomiary: Ween == = Jeneoo Segoe 0 5 5 2; O 12 0 3 one 30 ebruary W852. jo2--2< Jeeteeeesas 1 4 3 0 | 0 4 0 2 9 | 0 23 MODNUWAL YA 20 ms ainise = = ioctersissee = == = Oli are Asr 1 0 | 0 0 1 On| eeeee 0 2 ROGAN re cereniCisia share Stecrercic 2 143 18 | 141 54 | 137 41 9 79 69 | 3 | 2694 VICTORIA November 25. 35 December 10. - 29 December 19. - 5 December 24 51 January 7... ees SAS oes OW eer cael ees PSone teak 0 0 0 January 14. . 3 | BA ae nye ee Das. -anctal teresa steamers ere Steree 14 January 21. . 6 10 12 | 6 12 | 4 2 12 | 5 2 71 February 4. - 9 | 8 9 2 10 | 1 2 14 | 11 1 67 February 18. c 6 | 2 7 8 4 1 | 0 127) ld 0 51 HMebrUaty 26ee sci o- cies Geeie cease 9 11 4 5 11 5 | 08 eee eeeeee oa 45 Matalienssee on. She estes 44| 55) 37) 59) 54) 13) 11| 60) 32) 3) 5368 | | | | a This total represents 3.6 per cent of all the weevils put in the cage. b This total represents 1.7 per cent of all the weevils put in the cage. In the section of the table containing the records for Dallas the large number of weevils found dead in section 6 on January 24, 1907, may be explained by the statement that no previous collection of dead weevils had been made in this section. All but 50 of the wee- vils found were upon cheesecloth stretched horizontally across the section above the ground. The full number is included merely to indicate the proportion of weevils which probably fall to the ground upon dying. In this section less than 20 per cent remained upon the screen, and it is reasonable to suppose that a similar proportion may have existed in other sections. The percentage of mortality in each place is much smaller than the percentage of living weevils. Upon the charts shown in figures 3 to 5 the number of dead collected is indicated by a broken line extending beyond the line representing the number of living weevils. 90317—Bull. 77—09——5 66 HIBERNATION OF THE COTTON BOLL WEEVIL. ACTIVITY AS SHOWN BY DEVELOPMENT DURING NORMAL HIBERNATION PERIOD. Under the heading “Stages entering hibernation” the principal data bearing upon developmental activity during the winter have been given. (See pp. 13 and 14.) Additional data have also been given in connection with “Shelter during hibernation.”” (See Table VII, p. 26; also Table IX, p. 28.) To these records for seasons pre- ceding 1906-7 may be added the results of an experiment in collec- tion of infested squares during this season. On November 23, 1906, Mr. J. D. Mitchell collected 100 fallen squares which were supposed to be infested. These were placed in the small cage under shelter and out of the reach of sunshine. On February 10, 1907, he found that 45 squares showed weevil emergence hulls, and the full number of adults was found; however, all were dead at that time. An exam- ination of the remainder of the squares revealed but one dead larva. The others, apparently, had contained no weevil stages. Exception- ally warm weather had prevailed during December and January, as has been shown in figure 5. This had enabled the weevils to com- plete their development and emerge, but all had starved to death in the absence of any food supply. Some very interesting facts are also brought out by a closer study of the records in connection with section 10 of each cage. As has been shown, the experiment in these sections consisted of the collec- tion of large numbers of unopened bolls probably infested. Several of the bolls were buried under 2 inches of dirt and the remainder were exposed upon the surface of the ground (PI. X, fig. 1). No partition was inserted to separate the weevils emerging from these two lots of bolls, but in the case of section 10 at Dallas the first lot of bolls was buried and a considerable period elapsed before the bal- ance of the bolls, which were left upon the surface, was placed in the cage. It was estimated that 3,000 bolls were buried at a uniform depth of 2 inches under cover of heavy black soil. An examination of 100 bolls showed 8 recently transformed but unemerged adults in the bolls and 8 adults which had emerged were hibernating within the protection afforded by the bolls. On this basis it appears that about 480 weevils were buried in this lot of 3,000 bolls, half of them being unemerged adults and half hibernating adults. No other mate- rial was placed within this section, so that all’weevils which were subsequently found upon the screen must necessarily have found their way through the 2 inches of soil under which the bolls were buried. Counts made before the bolls to be placed on the surface were put into the cage showed that 65 weevils at least had escaped from the bolls to the screen forming the cage. This shows that fully 13.5 per cent of all the weevils buried, emerged and unemerged, had EMERGENCE FROM HIBERNATION, 1907. > 67 succeeded in escaping. Undoubtedly part of these had left their cells in the bolls after they were buried, as it is very likely that the burial of the bolls in moist soil may soften the hulls so as to enable the weevils to escape through them as readily as though they remained dry upon the surface of the ground. ACTIVITY IN THE FIELD DURING NORMAL HIBERNATION PERIOD. For a number of years it has been known that, in southern Texas especially, weevils may frequently be found moving actively in the field during the winter, but the observations made during the season of 1906-7 extended the range of such occasional activity even in northern Texas. Taste XXXIII.—Outdoor activity of weevils during winter of 1906-7. = eer eee sue eevils Dlants gules Locality. Date. niridt ences Remarks. ined. | 1907 Dallas Mex =. occ. fedlesaly. al eles ere Found on awning rope. ID) E See 5 ne See | Jan. 11 1a | es eae Found on window screen; temperature 74° F. IDYOoS ao See nee Feb. 12 il Wiener ee ee Found on outside of hibernating cage; tempera- ture 75° F. College Station, Tex....| Feb. 22 LL Seen Ske Do. IDOE Sse Seen ee Jan. 17 Dil eons oe eH Feeding on sprout cotton. 1906. Wighoriashexs-6 5.20 ce. Dec. 29 Om aA ae || When given sprouts, all were feeding in 80 min- utes; temperature 82° F. WO See ease seat ee 2dOr a. Ob tS ease Mere When given sprouts, all were feeding in 45 min- utes; temperature 82° F. 1907 1D Yo) 2s8 Ms SEA Ree WeAJE} ola ts} 9 (a) Mean temperature, January 1-8,=67.76° F. WOES Cees Eo oe Jan. 9 20 (0) On black land. ID) Feces See Oe eee Jan. 12 7 6 IDO Fare ee ease Jan. 16 1 50°| 10 weevils in bolls on the same plant. iD) OME nee ae oe pe doenc: 2 30 | IDO) Mien Senet | Jan. 17 4 8 JOD ied eee Jan. 18 1 17 1D\O) 5 Soe see So meaee Feb. 14 1 25 | Upland sprouts not killed as in bottoms. IDOE eacesae seme Feb. 21 3 50 | Very dry for sprout growth. a Record not kept, though plants were examined, 6 Sprout cotton on six farms examined. From the Victoria records it appears that between January 8 and February 21, at a time when weevils should normally have been in complete hibernation, 48 adults were found feeding on about 200 sprout plants. This record is unique for the United States, and a similar activity in the field may not be duplicated except under very rare conditions. EMERGENCE FROM HIBERNATION, 1907. As is plainly shown by figures 3 to 5, the actual period of general emergence from hibernation began in each locality about February 20. As has been previously stated, the actual date of the beginning of emergence can not be positively given. It can be better expressed as a period of “beginning emergence,’’ and for this reason this period seems to lie between February 20 and March 1. Owing to the excep- 68 HIBERNATION OF THE COTTON BOLL WEEVIL. tional earliness of the season preparations for the regular observations upon emergence from hibernation were not sufficiently complete for beginning the work until March 1 and in each locality this date may very reasonably be considered as the beginning of the emergence period. Previous experience having demonstrated the necessity of keeping the records upon this work according to a uniform system in each locality, the preparations were much more elaborately made than for any previous work. Comprehensive forms upon which the records might be entered with a minimum of labor were prepared covering five distinct divisions of the work: (1) Meteorological record; this record covered maximum and minimum temperatures, atmospheric humidity, rainfall, sunshine or cloudiness, and winter conditions. (2) Emergence record; this record showed the emergence in each section for each date. The records for one week were placed upon a card so that the totals for emergence for each day, and also for each section for each week, could be very readily ascertained. (3) Section record; this covered in more detail the emergence in each section and indicated the sex of emerging weevils and what disposition was made of them, in such a way that their records could be followed until the time of death. (4) Longevity records for fed weevils. (5) Lon- gevity records for unfed weevils. This systematization of the record work has proved an invaluable help in compiling the results of this extensive series of observations. The general facts regarding the relationship existing between climatic conditions and weevil emergence are indicated graphically in figures 6 to 8. The most important conclusions upon special points can only be shown by special arrangements of the data in each case. These tables have been made as concise as seems possible. Practically each line in the tables expresses only the summary of a large number of compiled records. The magnitude of the work mvolved in the com- pletion of such data can be appreciated only by one who has under- taken a similar task.? RELATIONSHIP OF EMERGENCE FROM HIBERNATION TO CLIMATIC CON- DITIONS. Figures 6 to 8 have been prepared in the same form as figures 3 to 5, since they express a continuation of similar facts. In former reports,’ dealing especially with the life history of the boll weevil, it was stated that emergence began about the time when the mean temperature rose above 60° F. The more complete a The senior author desires to express particular appreciation of the great amount of detail work which has been done by the junior author (Mr. W. W. Yothers) in the prep- aration of the summaries covering this work. bU.S. Dept. Agr., Bur. Ent., Buls. 45 and 51. EMERGENCE FROM HIBERNATION, 1907. 69 records now at hand indicate that emergence may take place when- ever the mean average temperature exceeds 55° F. It is certain that weevils may be active at a temperature considerably lower than this, but the records do not indicate that there is a general RAINFALL IN INCHES | » MEAN AVERAGE TEMPERATURE, DEGREES FAHMRENHElT = : | ; = aii anal “L061 ‘oung 09 Wore “Xap ‘sejeq ‘WoNeUIEqIY Woy VdUeSIOMIa pue ‘Treyuyes ‘oinzeriaduie} esvIoAe URIUL SUIMOYS JIVYQ—'9 ‘DI emergence from hibernation at a lower temperature. After having left their winter quarters, weevils may continue active at considerably lower temperatures than are required to draw them out from their shelter. This statement may, in part at least, explain the continued 70 . HIBERNATION OF THE COTTON BOLL WEEVIL. activity of weevils during the winter of 1906-7 and the early beginning for the period of emergence for that season. CISYIWT STAZIM IO SIGHNN S. 8. BUR eee ean Oe PS ea a a a COE Se eee ie a sar eae Ml T7TCINIVY, (> Mt 3 ey SG) 110 10 is) SULY ae i Be ae Bi Sate aeee ee] DAA Gale ae rae ie rch | Eevee a PAL ABE f A [ | ira i faba niene ere alc eet | ies i i ad efollett IS ete en a ae, Fic. 7.—Chart showing mean average temperature, rainfall, and weevil emergence, Calvert, Tex., March to June, 1907. | Meee aie aura rial P| Sife [Oe oe (ea ese) ae I mui oO Bis iho Man ins in (Oy OTS i) Soran nOm Mm Toman NOR A = = so SZHIN/ Ni TTMIN Fes ro) SH BH OD © o oO Ww YHYS STITHIIO “FINLVHFTASAWFL IOVYFIAY NYFW + A comparison of figures 6, 7, and 8 indicates that the period of great- est emergence in each locality occurred during March, 1907. The abnormal nature of temperature conditions is shown by the fact that EMERGENCE FROM HIBERNATION, 1907. dali at Dallas the mean average temperature for the month was over 11 degrees above the normal. At Calvert the departure was about the a See IN INCHES ie a ae eg TEMPER AT URE, oe = | Beata <2 aie ia esses = il I ANE AY Beeeee eres maedal | "1061 ‘oUNnL 0} YOR, “Xoq, “VII0JOTA ‘OOUSSIOUIE [LAGOA pUe “[[eyUTeI ‘oIN}eIOdUIO] OSBIDAG UBT SUTMOYS JIBYO—'S “DIT | | a o 2 ro) 3 RAINFALL /N INCHES NUMBER OF WEEVILS LIVER GED same, and at Victoria it was but slightly less than 10 degrees above normal. Such high temperatures do not often occur before the latter part of April and the 1st of May. The temperature for April was 12 HIBERNATION OF THE COTTON BOLL WEEVIL. unusually unfavorable, but in all sections it ranged from 3 to 5 degrees below the normal. This decrease was not, however, sufficient to check the emergence of weevils, although undoubtedly it served to extend the period of emergence in an unusual degree. The abnormal nature of the temperature conditions for the spring of 1907 may be understood from a comparison of the mean monthly temperatures for these four months in each case. The normal is determined by the Weather Bureau records from an average of the mean monthly tem- peratures for the entire period during which records are available. The departure of each season, therefore, affects the normal for the following season. The general impression in regard to the exceptionally high tem- perature experienced during the winter of 1906-7 is confirmed by a comparison with the average records for a number of seasons. Tem- perature alone need be considered in making this comparison, although rainfall has an important direct effect upon temperature conditions. For the following comparison the records given by the United States Weather Bureau are used. As there is no report for Calvert the average of two points about equally distant on opposite sides of that place is used. TaBLE XXXIV.— Mean monthly temperatures and departures from normal at Dallas, Calvert, and Victoria, Tex., November, 1906, to February, 1907. November. December. January. February. | Locality. Monthly | Depar- | Monthly | Depar- | Monthly | Depar- Monthly | Depar- mean, ture. mean. ture. mean. ture. mean. ture. oH: oF. oi wae in de wats wae ait Dallas -yse fore seeaee = 54.3 —0.6 51.6 +3.8 53. 4 +8.5 51.2 +6.6 Calvertiscce: aeeenen 59.1 + .1 56.8 +4.1 59.8 +9.6 54.8 +2.8 Wittoniaies 9:52 oe 62.9 —1.8 59. 2 +1.4 63.4 +9.8 | 60. 2 +6.2 It will be noted that the departure from normal during November was very slight. The temperature conditions, therefore, during the usual period of entrance into hibernation were practically normal, the rise occurring during December and January, especially when weevils should normally have been in complete hibernation. Table XXXV continues the same study throughout the period of emergence from hibernation. TaBLeE XXXV.— Mean average temperatures and departures from normal at Dallas, Calvert, and Victoria, Tex., March to June, 1907. March. April. | May. June. Locality. if P | P Monthly | Depar- | Monthly | Depar- | Monthly | Depar- | Monthly | Depar- mean. ture. mean. ture. mean. ture. mean. ture. ike He eS milite Sts os or °F. Dallas: oe aeoseessseee 66.7 411.1 61.4 —4.2 65.8 —7.7 78.8 —1.9 GCalverts2: saencecse ee 70.0 + 9.2 62. 2 —5.9 66. 6 —7.3 76.6 —4.4 WMictoriasseresssscese 72.4 + 9.7 69. 4 —3.3 73.0 —5.0 81.6 — .6 EMERGENCE FROM HIBERNATION, 1907. 73 The unprecedented emergence during March is very easily explained by the remarkable temperature conditions during that month. In spite of the fact that emergence began earlier than had ever been known previously, it continued later also because of the exceptionally low temperatures prevailing during April, May, and June. A com- parison of figures 1 and 2 with figures 6 to 8 is interesting and shows how strikingly the nature of the emergence movement may vary in respect to difference in climatic conditions. The careful examina- tions made to discover the termination of the emergence period were continued for fully two weeks after the last weevil was found. It seems impossible to explain the long-delayed emergence of some individuals. The lack of an explanation, however, does not alter the fact that emergence is probably not generally complete until after the middle of June. TABLE XXXVI.—General summary of experiments of 1906-7 on emergence from hibernation. Number of weevils— Lee umber Percent- ; sed as : age Locality. basis for a emer- Put in | percent- ial ging. cages. age of ging emer- gence.@ PV ATPASE Oma miners tec epeaisiann hayes eee ea cee alah cise ain eo Bcbisie bee 32, 439 30, 864 3, 464 11. 22 Calwenty Rexmeree a mmne e ao ne: Bae Rous ee PE EE ee 20, 430 19, 408 1, 842 9.49 WAKELIOSCIE, 14 NDS os epee RSS eerie oe tea eae ee ee Oe 23, 645 22, 463 b 3, 026 13. 47 Rotalpandiaveraees ssa. osc cree ses te ia oe areas tee 76, 514 72, 735 8, 332 11.45 aBasis for computing the percentage of emergence is 5 per cent less than the number of weevils put in cages owing to the escape of some weevils through the meshes of the wire. 6 Two weevils not in summary. A deduction of 5 per cent from the number of weevils placed in the hibernation experiments is made to furnish a more correct basis for determining percentages, on account of the fact that experiments have shown that about 5 per cent of a miscellaneous collection of weevils may be able to escape through 14-mesh wire (Pl. VII, fig. 1), such as was used in the construction of these cages. The percentage of survival is strikingly similar in each locality. The average sur- viving hibernation—approximately 11 per cent—is probably the highest that has ever occurred since the weevil entered Texas. Although observations have indicated that occasionally the per- centage of survival may be as high as this in the field, it is fortunate for the cotton planter that such is very rarely the case. 74 HIBERNATION OF THE COTTON BOLL WEEVIL. EFFECT OF TIME OF ENTERING HIBERNATION AND NATURE OF SHELTER SURVIVAL. UPON THE PERCENTAGE OF One of the most important pomts upon which information was sought throughout these experiments was the effect of time of enter- ing hibernation and nature of shelter upon the percentage of survival. The first confinement of weevils in the fall occurred fully a month. earlier than the beginning of similar experiments the previous year, and it was expected that the imtervals between their confinement in the cage and the time for successful hibernation might be sufficient to plainly reduce the proportion of weevils surviving. TaBLE XXXVII.—Chronological arrangement of sectional records showing relative survival at Dallas, Calvert, and Victoria, Tex., 1906-7. DALLAS. | Sec- Date of Basis ; sis Total | Percent- | Rank of When tion Character of shelter and food. last number weevils age of | section in started. | num- emer- of al eal ial ber. gence. | weevils. | ™ersed. | survival. | survival. 1906. 1907. Oct. 13 1 | Leaves and hay, 4 inches deep, cot- tonistalksilett asa saeeeee eee May 21 3,800 99 2.61 12 Oct. 16 4 | Leaves and hay; stalks cut and left : four daySioy. hens ann oseen oer peer May 6 2,090 85 4. 07 il Oct. 20 2 | Leaves and grass 4-5 inches deep; NO; TOO Ge) ee Sas 5 Seer ee eee May 19 3,610 226 6. 26 7 Oct. 24 7 | Spanish moss and chips;¢ cut food..| June 17 3,325 231 6. 95 6 Oct. 30 8 | Leaves and grass 2-3 inches deep; no foodiG te. 2s. kee en eee June 15 2,850 250 8. 85 5 Nov. 5 5 | Leaves and grass 9-10 inches deep; ; stalksicutand lefties: 322: ees see May 15 3,135 383 12. 22 4 Nov. 12 3 | Leaves and grass; no foods .......-. May 21 3,040 448 14. 74 3 Nov. 13 9 | Leaves 8-10 inches deep; green cot- ton/cut and Jeftigs2e22 sae ...| June 19 3,040 788 25. 92 2 Nov. 15 11 | Leaves 3-4 inches deep: stalks left Standingece 2. pee cote eee eee June 4 2,565 804 31. 34 1 Nov. 21 DD terre a Osea sgee eee es Scene June 8 1,570 65 h4.14 10 Nov. 28 6 Bate fuitayotovols aaveysiovo(ol4 2 2 eee A Apr. 29 975 46 4.72 8 = | OUSPMoniSuTaAceis eas eee eee | E ‘ Ber 16! 10 eens wosisdt ae ee a a \May 2 S64 39} 4.51 9 | Total and average: ......2...- |e eee ett 30, 864 3,464 D122) | see eee CALVERT. Oct. 13 1 | Food, two days; grass and leaves 4-5)inGhes:GGep as ears eee eee June 12 | 2,375 75 3.15 7 Oct. 19 4 | Grass and leaves 4-5 inches deep..-.| May 30 | 2,375 116 4.88 5 Oct. (25 (ais Danishamoss-sChipSssessee=eseeeeee July 1 2,375 105 4.42 6 Oct. 31 8 | Food two days; grass and leaves 4-5 inGhesrdeepenscesac creer oer eens May 30 2,375 63 2. 65 8 Nov. 5 5 | Food dry; grass and leaves 4-5 INnchesideep se sacs eee eee Apr. 26 2,375 45 1.89 9 Nov. 12 9 | Food cut down, left dry; 10 inches STS Spel Clel CVS eres ere ee June 12 2,375 438 18. 44 3 Nov. 14 3 | Stalks cut down, left dry; 2 inches STaASsanGieagvessere vies avec cence May 31 2535 253 10. 65 4 Nov. 25 | 6 | Field protection or bare; some grass-| May 16 1,425 359 25.19 2 Nov. 26 | 2 | No food; leaves and hay...-.-...--- June 12 1,358 380 27. 98 1 Dec. 3 LO! BOS seas Reet eee oe ee nel Tee ce Mar. 24 | (k) ioth| BAe See 10 No tvalvandiavenrage se ane c--s2. ass occ cee 19,408 1,842 9.49525 ae aSee Pl. VII, fig. 2. b See Pl. VIL, fig. 3. ceSee Pl. VIII, figs. 1, 2. dSee P1. IX, fig. 1. eSee Pl. IX, fig. 2. f See Pl. IX, fig. 3. 9See Pl. X, fig. 2. h The weevils put in on November 21 were brought from Brownsville, Tex. The low percentage of survival doubtless resulted from their weakened condition, owing to insufficient food during transportation. i Bolls presumably infested. jSee Pl. X, fig. 1. k No estimate made. Bul. 77, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE VIII. BS ai Mey pas aii =a, ve HANGING Moss AS AFFECTING HIBERNATION AND EMERGENCE. Fig. 1.—Section 7, with hanging moss in top of cage. Fig. 2.—Same section, ground conditions, started October 24, 1906; 6.95 per cent surviving; emergence ceased June 17, 1907. (Original.) Bul. 77, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE |X. SHELTER CONDITIONS PRODUCING AVERAGE SURVIVAL AT DALLAS, TEX. Fig. 1.—Section 8, started October 30, 1906: emergence ceased June 15, 1907: survival, 8.85 per cent. Fig. 2.—Section 5, started November 5, 1906; emergence ceased May 15, 1907; survival, 12.22 per cent. Fig. 3.—Section 3, started November 12, 1906: emergence ceased May 21, 1907; survival, 14.74 per cent. (Original. ) Bul. 77, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE X. EXCEPTIONALLY FAVORABLE CONDITIONS AND BOLL EXPERIMENT. Fig. 1.—Section 10, a, bolls exposed on surface; b, corner where bolls were buried 2 inches deep, started December 6, 1906; emergence ceased May 2, 1907; survival, 4.51 per cent. Fig. 2.— Section 9, stalks left, started November 13, 1906; emergence ceased June 19, 1907; survival, 25.92 percent. (Original.) EMERGENCE FROM HIBERNATION, 1907. 75 TaBLE XXXVII.—Chronological arrangement of sectional records showing relative sur- vival at Dallas, Calvert, and Victoria, Tex., 1906-7—Continued. VICTORIA. Sec- Date of Basis A Total Percent- | Rank of When | tion Character of shelter and food. last number weevils age of | section in started. | num- emer- of Gal Fal wal : nan gence. | weevils. |°™ersed. | survival. | survival. 1906. 1907. Oct. 25 1 | Weeds and grass 5 inches; stalks left.| May 11 2,375 201 8. 46 7 Mose: 4 | Weeds and grass 5 inches; stalks | POIMOV OC meses aire oe sscts Aan a May 15 2,375 105 4. 42 9 Oct. 28 2 | Weeds and grass 4-5 inches; stalks | CULMleiiaane ese fe ee ee May 11 2,375 134 5.61 8 Nov. 6 7 | Moss, bark, chips, ete.; no food.._.. | June 15 2,850 674 23. 65 1 Nov. 10 8 | Grass and weeds 5 inches; stalks | MEMO VCOMME Noe ha oo ue. esa | May 6 2,850 362 12.70 6 Nov. 14 5 | Stalks pulled, left; grass and weeds DUC HES n | et neater Apr. 28 2,850 449 15. 86 3 Nov. 21 9 | Grass and weeds 10 inches; stalks Dulledrandwleltaesa. eee so eee | May 23 2,850 374 13.19 4 Do. 3 | Weeds and grass 2 inches; stalks ¢ MuvedtandMetiy 228.222 52.5005. Pl Ovens 2,850 588 20. 63 2 Nov. 28 G4) Ground bare-.nofood!s.-.. 222. 2... May 11 1,088 139 12.78 5 Nov. 29 LOR OSes ate et ers se Je 2S Mar. 4 (@) 7 Sen ees oe 10 Motaland average-.....!..--.|-..---2-+- 22,463 3,028 13. 47 | be ed a Three bushels of bolls on the surface, and 3 bushels covered with 2 inches of earth. The results of this work are exceptionally striking in the case of the Dallas record. The Calvert record ranges between that of Dallas and Victoria in regard to the clearness with which comparative effects are shown. In each case there is, however, a general tendency toward more successful hibernation as the season advances after the middle of October until the time when frosts occur. . In the case of the Dallas records there occurred an almost uninterrupted increase in percentage of survival with each date upon which experiments were started. The apparent exceptions are readily explainable by other facts than the time of starting the experiment. Section 12, which ranged sixth, received weevils collected at Brownsville, Tex., which made it neces- sary to ship for a long distance. During this shipment their food supply became poor, and the weevils were undoubtedly much weaker upon being placed in the cage than were those which had been col- lected in the immediate vicinity of Dallas. Section 6 was not provided with any shelter for the weevils, and the percentage of survival was smaller on that account than in other sections started at about the same date. Section 10, which ranged ninth, received only infested bolls, upon and within which weevils were hibernating. From October 13 to November 15, under approximately similar conditions, the percentage of survival increased from 2.61 to 31.34. (See Pl. VIL, figs. 2,3.) A more forceful argument than this for the destruc- tion of the food supply as early in the fall as is possible could hardly be given. A combination of the records for those localities at which experi- ments were started upon the same or approximate dates, grouping them so that the chronological sequence is most clearly shown, adds additional emphasis to the statements which have just been made. 76 HIBERNATION OF THE COTTON BOLL WEEVIL. TaBLE XXXVIII.—Comparison of sectional records grouped by approximate initial dates. Basis Rank in A : Total | Percent- Date. Locality. eee ea number | . age of si 5 weevils, | Merged. | survival. survival. 1906. Ot. “13. Dallas: paar ase ee eee ete Cease 1 3, 800 99 2.61 DO)..-=:| Calvert---s-.2ssconmceck ers mane eee ee eas 1 2,375 75 Sal5 8 OCE. EUG" || Dallas. 2255 Se aera ene aed Senn 4 2, 090 85 4.07 | Totalandiaveraceseetcee set eee eee pees 8, 265 259 3.12 Oct: :19)) Calverti2 Seas iter son eesnn cee eee ee ae 4 2,375 116 4.88 7 Oct... 20") Dallas2 ose e Bae face sas sees oe ee eee 2 3,610 226 6. 26 \ Notalandvaverage:-sasee se seas eee lee eee 5, 985 342 5.71 Oct. e245) Dallase cae teen ase = terete eae atone 7 3, 325 231 6.95 Octi- 225") "Calventiso= ste ee. ace ees aiene eee 7 2,375 105 4.42 5 Do sss Victorias jes oee Sen eee poner eee 1 2300 201 8. 46 Doss GOR SL Sie Race Se ea EE 4 2,375 105 4. 42 Totaliandsaverage:.-2=c24-e-ss-te ec seeee secre 10, 450 642 6.15 Oct. 284 | Wictoriat=so-ses2ssos5eeees nara Boe tee sal a 2 2, 389 134 5.61 Oct, B05 MDallasss: = hoSy eee Bees aa: Coote eee ee 8 2, 850 250 8.85 6 Octe 3) |i Calwentic sss eeee sam = sae eee eee ar 8 2,375 63 2.65 Totaland average: 2a scr saeco eee eee 7,614 447 5. 87 Nov. 5 5 3, 135 383 12. 22 Do. 5 2,375 45 1.89 4 Nov. 6 i 2, 850 674 23. 65 Totallandiaverages. -- Ssase-c ee asses) aot eee | 8, 360 1, 102 13.18 Now; 1OulAvietorlans | Movecee se ee hs eee ee 8 2, 850 362 | 12.7 Now. 125| Dallastox. aoc. o eee eee eee eee seca 3 3, 040 448 14. 74 INOWas 14 Calvert Sess So-c B52 pa eet isersoe ane ae 9 2,375 438 18. 44 9 INOVs, dos] Dallasto25 foce see eee eeeee ee elite al ere 9 3, 040 788 25. 92 INOWe 4s WaCtOniaseee cesses se eee eee eee eeera 5 2, 850 449 15. 86 | INOwWs W153) Wallases e252. seseasen sence se eee ear 11 2, 565 804 31. 34 | Totalian diavergge.= 2 saa scsene eerste eee 16, 720 3, 289 19. 67 | Nova 21GDallasics pete he ys ene ae eee see 12 1,570 65 a 4.14 IDO.) S| WWiletoriata.2 | Sass Sood ses ees scaileseme: = 9 2, 836 374 13.19 3] Does .e ee OO asset eee eset eeeewh ease Bao 3 2, 850 588 20. 63 Total and average.......--...------.|.--------- 7, 256 1,027 | 014.15 Nowe onl Calvertiece. qaeenee taste erro ae aaeret cere 6 1, 425 3590s 25198) INOWa 260) |Gaeee Oz ieee ees eS pasoee ne Bawls este smear 2 1, 358 380 27.98 1 INOWe J288N Dallasee ties Sach Be ann eeinareseeteee eos 6 975 46 c 4.72 DOS A VAC TONS oe oe eee ca sete asaie late eerste 6 1, 088 139 c 12.78 Totaliand averages so. 2 set Ses ose ee oases 4, 846 924 d 19.07 a Brownsville, Tex., weevils. d FURR? eh Geo weevils, 16.91 per cent. d Average without Dallas cage, 22.7 per cent. In this table it may be seen that, taking all localities together, whenever experiments were started upon approximately the same date there is a most striking increase in successful survival at inter- vals between the middle of October and the middle of November. This table may be safely considered as representing in the most general way possible the facts in regard to this point. An interval of about eleven days between October 14 and 25 practically doubled the percentage of weevils surviving. Again, in an interval of about ten days between October 25 and November 5 the percentage was again EMERGENCE FROM HIBERNATION, 1907. rh doubled, and an increase of 50 per cent was observable between November 5 and 14. After November 14 hibernation might have been successful for practically the maximum possible proportion of weevils. The relation of these figures may be most simply expressed in the following manner: Under similar conditions of shelter, but without a food supply, if the survival of weevils in Texas for October 15 is one, for October 25 it will be two; for November 5, four; and for November 15, six. These figures make it evident that from October 15 to November 15 constitutes the strategic period for attack upon the boll weevil. The attack can be made in two ways: (1) By the destruc- tion or removal of the conditions favorable for the shelter of the weevil through the winter; (2) by the destruction of the food supply. These conclusions have frequently been stated and are here repeated because the facts here presented prove more conclusively than have any other data heretofore obtained the unquestionable importance of fall work in combating the boll weevil. The benefit, obviously, will always be realized during the following season by a much smaller injury to the crop. Considerations, both of minimum expense and of maximum effectiveness, emphasize this conclusion. SURVIVAL OF WEEVILS BY LOCALITIES AND CAGE SECTIONS. In practically all of the sections it may be considered that the emergence period began during the last few days of February and the first few days of March, March 1 being, approximately, the average date in each case. In the following table the summaries of the sectional records in each locality are given, together with the data necessary to show the maximum length of the hibernation period and the percentage of survival in each section: TaBLE XXXIX.— Maximum hibernation period and percentage of survival by sections, 1906. DALLAS. Number | Date of = : used as ; Total Percent- Section number. Bula Weruls basis of et weevils | age of * | percent- é emerged, | survival. gence. age. 1906. 1907. Un - oc ae SO aCaeE SD EC HEHE OOo OR EE BEE Saas Oct. 13 4, 000 3,800 | May 21 99 2. 61 Pe RO OS SA eee oP Ore De Oe ae Oct. 20 3, 800 3,610 | May 19 226 6. 26 ee eee hee eT Cee A rele Oe oe Nov. 12 3, 200 3,040 | May 21 448 14. 74 He Je cS ce See CORO ESE Eee Boe aa eee Oct. 16 2, 200 2,090 | May 6 85 4. 07 Poe SABE AB SABE RO TEE eee Ee eae Nov. 5 3, 300 3,135 | May 15 383 12. 22 Oe Sede SSE eee ae one ae Noy. 28 1,025 975 | Apr. 29 46 4.72 fodnaksOSeSr eH ee REE O RnR SNe ns ane Oct. 24 3, 500 3,325 | June 17 231 6. 95 Ree eta eS eee Le eee oe f Oct. 30 3, 000 2,850 | June 15 250 8.85 Oeste ne 2 At Atenas eee ape. - ates Spar Nov. 13 3, 200 3,040 | June 19 788 25. 92 NO. 2 acy eee ate ere Sa Cee ae Ee ean ee Dee. 6 864 864 | May 2 39 4.51 Lien a seit a aE Oe SE ae Seed ae I a a | Nov. 15 2, 700 2,565 | June 4 804 31. 34 Tse cco CRORE OS OE ee ne ne eee Nov. 21 1,650 1,570} June 8 65 | 4.14 Movalvand averages. pos ee oss eel Cancion 32, 439 BOF864 hes ase 3, 464 | 11. 22 78 TABLE XXXIX.— Maximum hibernation period and percentage of survival by sections, 1906—Continued. HIBERNATION OF THE COTTON BOLL WEEVIL. CALVERT. Number : Date of r eons used as : Total | Percent- Section number. eh ui coms basis of ey weevils age of Te ae “| percent- gence emerged. | survival. age. 1907. 2, 500 2,375 | June 12 75 3.15 1, 480 Looe ee sed O sees 380 27. 98 2, 500 2,375 | May 31 253 10. 65 2, 500 2,375 | May 30 116 4.88 2, 500 2,375 | Apr. 26 45 1.89 1, 500 1,425 | May 16 359 25. 19 2, 500 2,375 | July 1 105 4. 42 2, 500 2,375 | May 30 63 2. 65 2, 500 2,375 | June 12 438 18. 44 Bolls. (a) Mar. 24 8) |e eeeceeee 20, 4380 1OVAOB i occas ce 1, 842 9.49 VICTORIA. | 2, 500 | 2,375 | May 11 201 8. 46 Gs Glin) Pee eM ae (0 KOS} 134 5. 61 3, 000 2,850 | May 23 588 20. 63 2, 500 2,375 | May 15 105 4. 42 3, 000 2,850 | Apr. 28 449 15. 86 1,145 1,088 | May 11 139 12. 78 3, 000 2,850 | June 15 674 23. 65 3, 000 2,850 | May 6 362 12. 70 2, 985 2,836 | May 23 374 13.19 (0) | (6) Mar. 4 2): lactase Seer Motaliand!average.# =e Sseeee 2 eee ac leeee aaese 235 645n | 22 40d eee 3, 028 13. 47 b Three bushels of bolls on surface and 3 bushels covered with earth. a No estimate made. The longest period of hibernation occurred at Calvert among the weevils placed in section 7 on October 25, the last weevil emerging from this section being taken on July 1, 1907. During this period of over eight months this weevil survived without a particle of food. This may be considered as representing the maximum hibernation period, and in the case of an insect producing numerous generations during each season it is surprising that the hibernation period can be so greatly prolonged. The largest average percentage of survival occurred at Victoria, although the variation between the three localities was not unex- pectedly great. The nature of the shelter provided in each section has been indicated upon page 57. A comparison of the records for section 7 for Calvert and Dallas with those for the same section at Victoria shows that at the last-named place the survival was four times as great as in the average of Dallas and Calvert. The shelter provided was as closely similar in the case of this section as in any of the series, and the significant point of difference appears, there- fore, to be the time when weevils were inclosed. At Dallas and Cal- vert this occurred on October 24 and 25, respectively, while at Victoria weevils were not placed in the cage until November 6. Apparently, therefore, the much larger survival at Victoria was due EMERGENCE FROM HIBERNATION, 1907. 79 primarily to the starting of the experiment about twelve days later than in the other two localities. The significance of the time of beginning the experiments is well emphasized by the records for sections 2 and 6 at Calvert. These two sections furnished by far the highest percentages of survival at that place, and apparently the only fact explaining this is that the experiment was started in each case at the time which was most favorable for successful hibernation, i. e., about November 25. This date was ten or twelve days later than those for sections 3 and 9, which present the next higher percentages of survival. An average of these two sections shows that among the weevils starting hiber- nation about November 12, 14.5 per cent survived, while among those starting hibernation about November 25, about 26.5 per cent survived. The records for Dallas show that the three highest percentages of survival occurred in sections 11, 9, and 3, which were started between November 12 and 15. In each locality the average date for the termination of emergence occurred between May 22 and 29. It is evident, therefore, that during 1906 the period of emergence from hibernation covered practically three months for an average of all of the sections and slightly more than four months for the last emerged weevils. MONTHLY SUMMARY OF EMERGENCE RECORDS. While it is important to know, approximately at least, the maxi- mum limit of the emergence period, it may seem more desirable to determine the time at which a majority of weevils surviving had emerged. It is more convenient in using the records to compare them in four-week periods rather than according to calendar months. Tasie XL.—Emergence in 1907, by four-week periods. | Mar. 1-28, wee- | Mar. 29-Apr. 25,| Apr. 26-May 23, | May 24-July 1, vils emerged. |weevilsemerged. weevils emerged. weevilsemerged. E cee ees | TO tal Locality. | | emer- Per Per Per Per | gence. Noe cent of Nuits cent of | ie | cent of Se cent of | : total. ; total. | ry total. ; total. Tee CR ee Se eee ee 2,486 | 71.8 4s4| 14.0] 452 | 13.0 42 1.2| 3,464 CAIN GR poet ERS sae eee aaa e 1,053) 57.1 410 2203) | 284) 15.4 95 5.2 1, 842 MNGLOR es 225 oo et Sooke 2, 399 79.3 476 15.7 119 3.9 32 iy 3, 026 Total and average... 5,988 | 71.3| 1,370] 16.4] 9855| 10.3 169 P| ts 88i U | WEEKLY EMERGENCE RECORDS. The following table presents a summary of the daily emergence records for each section during seven-day periods from March 1 to the end of the hibernation period. These records are particularly inter- 80 HIBERNATION OF THE COTTON BOLL WEEVIL. esting in showing the variation occurring in emergence in the same section and locality during the different periods. TABLE XLI.—Summary of emergence of weevils in cage sections by weekly periods, March 1 to June 20, 1907. DALLAS. Weekly period. Number of weevils emerged in section number— ie 2. ay 4. 5. 6. Uo 8. 9. 10. Lie 12s Mars le ae cere 40 69 155 36 151 21 73 79 212 12 |... 535] eseeee Mars (8-14) ase sass 8 36 51 10 46 if 25 31 120 7 65 7 Mar Sl b=21ce pete shee se ane 17 39 85 ig 89 11 64 35 202 13 145 10 Mar.222-28 26k etek las 10 21 38 8 51 2 25 22 123 4 189 11 Mari29=Apr4e > 2a seesecee 4 20 19 3 8 1 4 15 7 1 49 4 ADTs b=Uliss a tcaanseckeee-s df 13 30 7 10 3 7 10 17 1 78 11 Apri J2-18 322 oc er ae acacee 1 6 12 1 7 0 8 5 10 0 55 6 HS \yo) oa ee ee ee ee 1 5 8 0 1 0 2 3 6 0 15 0 ADT e2G—Miaive ers eeeee nee 5 10 16 3 5 1 2 20 8 1 27 1 Miaiyn3=9) me ptassaccmere eaee 2 3 21 3 di 0 7 14 26 0 40 6 May 10-165294 2222525 2 2 10 0 8 0 2 i 29 0 58 3 IM aiyali=23% ae eee Aaya eee 2 2 3 0 0 0 8 3 16 0 67 2 Miay324=302 8. 3c cece oe 0 0 0 0 0 0 0 3 4 0 12 1 Mayisl—Junel6s esses. sae 0 0 0 0 0 0 1 2 4 0 4 2 DUNGy/ loess ee eee eee 0 0 0 0 0 0 1 0 3 0 0 i June 14-2 ss sk se sek A hee Pee een ele eel eel 2 il 1S eee) eee cS 3625/5 Nota ss 7 seeoe eeeee 99 226 448 82 383 46 231 250 788 39 804 65 CALVERT. a Ey gay C7 eae te, pee tea 25 99 54 23 15 136 9 Ul 49 3: )|2cnc8a Sees IM aT soa ld es eee eee a rae 9 39 23 10 6 47 4 2 20 Ty | ioe lees Mian! 1 5=21 ee eet Sone 9 54 37 12 9 45 2 3 55 pA Et er Mar aeoa2Snpe eee cette 7 41 36 22 6 57 5 ili} 50 2 | oeso!l ere Mars 29=Avpr:t4 os ec eae oe 2 23 18 4 4 22 3 5 47 OS eeecellse coos NYO) Dayton 0 14 9 Uf 3 21 6 il 44 Ouse a2 Seer Dor ped eh ee ee eae 8 28 24 9 1 16 6 3 39 0: | 25283 See IAD TS 19-25 eee eies cane ee 2 6 2 1 0 6 1 2 13 (Oelasceecilesose = Apra-26—-Mayi2: 52 o --3 5) so eee 11 —12 Mauritius.2_.2=2 _. 33s 203" ee eee i Reunion =--— 2.22 ee ee eee ee eee eee ¥ United: States, history +2) = eee 9 a loss ‘in: United |States: =" 2.2 ee ee eee 9-14 Ttalyst ooo es oe ec 1113 mosquitoes. (See Anopheles mosquitoes and Mosquito, malaria.) + - prevention: <—- = =s2 "225 Se Se eee ee eee 14: relation to agriculture and other industries of the South_______ 13-14 ! Suppression in) Havana,2 8252.8 2 Se ee eee 17 Panama 2-2 eo See ee ee 21-23 Selangor, Federated Malay States_____________ 15-16 ; Manure; disposal; sto) avoid house wiies=2 325 ee 32-83 ; horse, breeding, placevor house hy =. ae ee eee 31) a rabbit, in ash pits, breeding place of house fly____________ aren ae aL 8 Markets, regulation, to) avoid: houseiflics===3= ee a Milk.*sources of bacteria therein=2 4 3= a eeeee 28-3 MIOSOUTCOMATSS SMT AO TE OL ATM ey TT STs ee iM malaria: ===. 63 Ree ee 7 4 yellow teveri2 2. Sz seet ee e 7 malaria (see also Anopheles mosquitoes). SUPDLession MeaSsures==— 2 ses ee 52 oe ee 15-17 yellow fever, Suppression. measures 222252. ==. sae ee eee 19-23 | Mosquitoes, losses in general which they occasion_____________-________ 8 ; through malaria which they occasion_____________-__ S-17 yellow fever which they occasion____________ 17-21 | Suppression Inv Panama 22> ee eee 21-23 Nations, endemic disease asvatiecting progress Ses ss eee ee B6-38 Ophthalmia; purulemis Carniaee: Diy, LO UW Se rfl yee eee eee eee eee ee ee 6 y Raper old, sbreeding: placexot NOUS: ily ss 31 q Finkweye; carriage by Eippelates files =o = ee eee if | Plague, bubonic. (See Bubonic plague.) 1 ay Poultry-house bedding, breeding place of house fly______________________ a2 j Progress of nations as affected by endemic disedse____________________ = 36-38 : aes; old, in ash pits) breeding) placeior housefly ee eee 31.5 testaurants, reg PUM ALLON UO, VOLO: MOUSE MT CS See 3 Sanitation, rural, necessity for government support_____ 330 See 35 Slaughtered cattle paunches, breeding places of house fly___________--_ 3 Sleeping Sickness, (carriage by: Ditine tes! == a= eee iG “spotted: fever? carriage toy: ticles oe eee ee eee pees ec ae aes Stable inspection against house flies, probable cost______--______________ 33-34 Siablessreculation, tovavyoid: house pics! 222s = eee 32-33 Stegomyia calopus (see also Mosquito, yellow fever). disseminator of myellow evens] 2.2 ee 7, 19-20; Stores; reculation, to,avoid house pilies= "> 28 Ee Straw, old, in ash pits, breeding place of house fly-_________________=— Mallow vats; breeding places) o£ house Ty 2222 eee Mick, carrier o£ spotted tever, 32-86 e wee eh ee Muberculosis, dissemination: by, house: fy 2] eee (7 Typhoid Lever, a sNationaleReproach”’ 25-2 252s a eee GisSemim atone by; LOUSE weliy = eee ee ene ene 7, 23-27, B4 in concentrationucamps, We S.eAriy eee eee loss in United Sintes... °. 55a. ne Ar Vegetable refuse, fermenting, breeding place of house fly________________ Yellow fever, cause, history of investigation_-—=52252 ) see deaths in New Orleans:<-<.---*_ Seo. 8 Saas eee WnitedP States. 222205 2: eee ee eee CisseMminationeDymNosguilO== == ee history in vAmeri¢a i= 22 sso). ee eee Se eee loss\in, UniteduStaltes: 2222 =. 52). 2 eae ee eee mosquito. (See Mosquito, yellow fever. ) suppression in Havana and New Orleans_____________-__ Pabapia._.--.... Ase eee O Paes DIV. INSECTS. U.S. DEPARTMENT OF AGRICULTURE, BUREAU OF ENTOMOLOGY—BULLETIN No. 78 (Revised). : L. O. HOWARD, Entomologist and Chief of Bureau ( AS ECONOMIC LOSS TO THE PEOPLE OF THE UNITED SPATES THROUGH INSECTS THAT CARRY DISEASE R a e,! on Bed "a a ee et fore ae 5 ey Se SS a eee se : PEGS = rane —s ne 5 BY L. O. HOWARD, Pn. D. Entomologist and Chief of Bureau. N IssurD May 27, 1909. les “fj PT a iy) akg = Re i! : avet Ke ae Si SIA Aina Scan A \\ ‘000M i iF ys WASHINGTON: % hi GOVERNMENT PRINTING OFFICE. 1909. liek a eee Por oEPART MENT OFF AGRICULTURE, BUREAU OF ENTOMOLOGY—BULLETIN No. 78 (Revised). L. O. HOWARD, Entomologist and Chief of Bureau. ECONOMIC LOSS TO THE PEOPLE OF THE UNITED STATES THROUGH INSECTS THAT CARRY DISEASE. BY L. O. HOWARD, Pu. D. Entomologist and Chief of Bureau. ISSUED May 27 1 L909: FN " p Reels eo we NW Lgy a Ona ara ieS> Wiice< WASHINGTON: GOVERNMENT PRINTING OFFICE. 1909. BUREAU OF ENTOMOLOGY. L. O. Howarp, Entomologist and Chief of Bureau. C. L. Maruarr, Entomologist and Acting Chief in absence of Chief. R. S. Crirron, Executive Assistant. C. J. Giuuiss, Chief Clerk. F. H. Currrennen, in charge of truck crop and special insect investigations. A. D. Hopxins, in charge of forest insect investigations. W. D. Hunter, in charge of southern field crop insect and tick investigations. F. M. Wesster, in charge of cereal and forage plant insect investigations. A. L. QuainTANcer, in charge of deciduous fruit insect investigations. EK. F. Puiuures, in charge of apiculture. D. M. Rogers, in charge of gipsy moth and brown-tail moth field work. A. W. Morritu, in charge of white fly investigations. W. F. Fiske, in charge of gipsy moth laboratory. F. C. Bisnopp, in charge of cattle tick life history investigations. A. C. Moraan, in charge of tobacco insect investigations. R. 8. Woeivum, in charge of hydrocyanic-acid gas investigations. R. P. Currin, in charge of editorial work. MABEL Co.Lcorp, librarian. 2 LETTER OF TRANSMITTAL. U. S. DeparTMENT or AGRICULTURE, Bureau or Entomowoey, Washington, D. C., April 20, 1909. Sir: i have the honor to recommend for publication as Bulletin 78, revised, of this Bureau the accompanying slightly revised copy of the Pasta edition of this bulletin, entitled “ Economic Loss to the People of the United States Through Insects that Carry Disease,” the supply of which is now almost exhausted. The United States is just awakening to a knowledge of the disas- trous results following a lack of appreciation of the danger arising from the unchecked development of mosquitoes and the typhoid fly, and it is hoped that this bulletin will not only emphasize this danger, but will also lend support to movements, both local and widespread, toward the destruction (often so easy) of these carriers of disease. Respectfully, L. O. Howarp, Entomologist and Chief of Bureau. Hon. James WItson, Secretary of Agriculture. OO vhs te eee ei, " ict ch a 5 a 1 a ne {Ubi cs MERA At. ASU beni ae hie tees 5 Pea ye a OR ve ae } Pas, pay ad, weg Marie “é ; ; eri ho MASULS. AN Pea A, ‘y sae wigan He we me my Lh dune do hee TTY sey nn ee, Vi By T PG : po / VG! ot tic Ah mad oy i ny ht ie ro} p 4 x i ie ‘\ ‘ ; : ary Fe a J TAL Wek “4 fy if ‘ah Ces Fey 2 hoo : ‘ that PANG 3 ti be SAY, ib} ine robin cages 4 vi nN (vgea ln ff Rapes veoh a? AL beat ayes Cnty ae ta, ss dy . } MOU 41 tik oh ae ch Meee a ‘ na “ie v ‘vt ie | hi ' Wi i Ch) et 4) 7 Tinea pat i * ¥ 1 ‘ i) 5 " Lg = ! ‘ak : ay My Ay é fa a Mey iy itt : ’ ‘ ) e's Gilead Ly dy DATO Mest ww lie eylye hee hes ; v7, ; ‘, Cia) 8 a ey ola The ee fy, OV 7 (Ae aE FP aye : h Peery DOr veh Laying sn A tI LO) As Ra enare seen! ba Nie i Pe Ye test ' rh ian Ay 2008) aU ty B hi Bs AT as aK ‘ae i Hii Hae 4 Sean tig Teeaaae , Ce yy a A r i‘ Z . iM iA SIGE CHCNET (a Lal CELE RE onsets An eA nl ee eee eA OR Oe Ae Se eee Bs ORa UTE Chee ee nan es A ie ee ee ee ee JANET AZT Ca SA le ee Ae ae en es ee ete ee ek A ces TIVO (ESE os A ES Es ae ge oe eee, Oe se el ES ee Le 5 : ) | Aa gee i my x ( eh a wey Ft idgie 1 LOPS ne i , - a YF aT, ee kk a “y*) an My } Rnke ie wy ' : 4 . | it. r - pie : ‘ . 7 rv ; 9 ‘ me ‘ ‘ ; . MN ECONOMIC LOSS TO THE PEOPLE OF THE UNITED STATES THROUGH INSECTS THAT CARRY DISEASE. INTRODUCTION. It has been definitely proven and is now generally accepted that malaria in its different forms is disseminated among the individuals of the human species by the mosquitoes of the genus Anopheles, and that the malarial organism gains entrance to the human system, so far as known, only by the bite of mosquitoes of this genus. It has been proven with equal definiteness and has also become generally accepted that yellow fever is disseminated by the bite of a mosquito known as Stegomyia calopus (possibly by the bites of other mos- quitoes of the same genus), and, so far as has been discovered, this disease is disseminated only in this way. Further, it has been sci- entifically demonstrated that the common house fly is an active agent in the dissemination of typhoid fever, Asiatic cholera, and other intestinal diseases by carrying the causative organisms of these dis- eases from the excreta of patients to the food supply of healthy indi- viduals; and that certain species of fleas are the active agents in the conveyance of bubonic plague. Moreover, the tropical disease known as filariasis is transmitted by a species of mosquito. Furthermore, it is known that the so-called “spotted fever” of the northern Rocky Mountain region is carried by a species of tick; and it has been dem- onstrated that certain blood diseases may be carried by several species of biting insects. The purulent ophthalmia of the Nile basin is carried by the house fly. A similar disease on the Fiji Islands is conveyed by the same insect. Pink eye in the southern United States is carried by minute flies of the genus Hippelates. The house fly has been shown to be a minor factor in the spread of tuberculosis. The bedbug has been connected with the dissemination of several dis- eases. Certain biting flies carry the sleeping sickness in Africa. A number of dangerous diseases of domestic animals are conveyed by insects. The literature of the whole subject has grown enormously during the past. few years, and the economic loss to the human species through these insects is tremendous. At the same time, this loss is entirely unnecessary; the diseases in question can be controlled, and the suppression of the conveying insects, so absolutely vital with certain of these diseases and so important in the others, can be brought about. -1 8 LOSS THROUGH INSECTS THAT CARRY DISEASE. MOSQUITOES. Entirely aside from the loss occasioned by mosquitoes as carriers of specific diseases, their abundance brings about a great monetary loss in other ways. Possibly the greatest of these losses is in the reduced value of real estate in mosquito-infested regions, since these insects render abso- lutely uninhabitable large areas of land available for suburban homes, for summer resorts, for manufacturing purposes, and for agricultural pursuits. The money loss becomes most apparent in the vicinity of large centers of population. The mosquito-breeding areas in the vicinity of New York City, for example, have prevented the growth of paying industries of various kinds and have hindered the proper development of large regions to an amount which it is difficult to estimate in dollars and cents and which is almost inconceivable. The same may be said for other large cities near the seacoast, and even of those inland in low-lying regions. The development of the whole State of New Jersey has been held back by the mosquito plague. Agricultural regions have suffered from this cause. In portions of the Northwestern States it has been necessary to cover the work horses in the field with sheets during the day. In the Gulf region of Texas at times the market value of live stock is greatly reduced by the abundance of these insects. In portions of southern New Jersey there are lands eminently adapted to the dairying industry, and the markets of New York, Philadelphia, and the large New Jersey cities are at hand. In these localities herds of cattle have been repeatedly estab- lished, but the attacks by swarms of mosquitoes have reduced the yield of milk to such an extent as to make the animals unprofitable, and dairying has been abandoned for less remunerative occupations. The condition of the thoroughbred race horses at the great racing center, Sheepshead Bay, Long Island, was so impaired by the attacks of mosquitoes as to induce those interested to spend many thousands of dollars a few years ago in an effort to abate the pest. All over the United States, for these insects, and for the house fly as well, it has become necessary at great expense to screen habitations. The cost of screening alone must surely exceed ten millions of dol- lars per annum. MALARIA. The west coast of Africa, portions of India, and many other tropi- cal regions have always, at least down to the present period, been practically uninhabitable by civilized man, owing to the presence of pernicious malaria. The industrial and agricultural development of Italy has been hindered to an incalculable degree by the prevalence of malaria in the southern half of the Italian peninsula, as well as in MOSQUITOES AND MALARIA. 9 the valley of the Po and elsewhere. The introduction and spread of malaria in Greece is stated by Ronald Ross, and with strong reasons, to have been largely responsible for the progressive physical degen- eration of one of the strongest races of the earth. In the United States, malaria, if not endemic, was early introduced. The probabilities are that it was endemic, and it is supposed that the cause of the failure of the early colonies in Virginia was due to this disease. It is certain that malaria retarded in a marked degree the advance of civilization over the North American Continent, and particularly was this the case in the march of the pioneers through- out the Middle West and throughout the Gulf States west to the Mis- sissippi and beyond. In many large regions once malarious the disease has lessened greatly in frequency and virulence owing to the reclama- tion of swamp areas and the lessening of the number of the possible breeding places of the malarial mosquitoes, but the disease is still enormously prevalent, particularly so in the southern United States. There are many communities and many regions in the North where malaria is unknown, but in many of these localities and throughout many of these regions Anopheles mosquitoes breed, and the absence of malaria means simply that malarial patients have not entered these regions at the proper time of the year to produce a spread of the malady. It has happened again and again that in communities where malaria was previously unknown it has suddenly made its appearance and spread in a startling manner. These cases are to be explained, as happened in Brookline, Mass., by the introduction of Italian labor- ers, some of whom were malarious, to work upon the reservoir; or, as happened at a fashionable summer resort near New York City, by the appearance of a coachman who had had malaria elsewhere and had relapsed at this place. In such ways, with a rapidly iner easing population, malaria is still spreading in this country. To attempt an estimate of the economic loss from the prevalence of malaria in the United States is to attempt a most difficult task. Prof. Irving Fisher, in one of his papers before the recent Inter- national Tuberculosis Congress, declared that tuberculosis costs the people of the United States more than a billion dollars each year. In this estimate Professor Fisher considered the death rate for con- sumption, the loss of the earning capacity of the patients, the period of invalidism, and the amount of money expended in the care of the sick, together with other factors. In making these estimates he had a much more definite basis than can be gained for malaria. The death rate from malaria (as malaria) is comparatively small and is apparently decreasing. Exact figures for the whole country are not available. From a table comprising 22 cities it appears that two- thirds of the deaths from malaria in the United States occur in the South—one-third only in the North. The death rate from malaria 83434—Bull. 73—09——2 10 LOSS THROUGH INSECTS THAT CARRY DISEASE. by States is available only for the following registration States: California, Colorado, Connecticut, District of Columbia, Indiana, Maine, Maryland, Massachusetts, Michigan, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, South Dakota, and Vermont, all of which are Northern States. For these States the census reports from 1900 to 1907, inclusive, give the following death rates: TABLE I.—Deaths due to malaria in the registration States, 1900-1907. Number Number efdeaths| ota etdeathe] nota Year, laria per deaths Year, laria per deaths 100,000 from ma- 100,000 from ma- ail laria. 1 Jaria. popula- popula- tion. tion. AQQO Deis cosace gece cece eee 7.9 DASE 1 GOB ais so Sateen eee cele ee aareee 3.9 1,321 W9OM: Shi heiie seco eocseeincsieness 6.3 TCO |} D906 so iro tarc osc cicicioin steinsreterosies 3.5 1,415 O02 semen tale ce ecm sei ebiece cee , 5.4 RT al te RS Urs sc Abra se codreaccas cao se 2.8 1, 166 TIS AB iseeespe AE oe oma pA A 4.3 1,410 —————— TOO G eee eg claret Ceeratcinelsiee mee 4.2 iS) | ee ne i ieee Oo Meee eS 12, 666 Estimating, from the preceding table, the average annual death rate due to malaria at 4.8 per 100,000 population, and considering that the registration area includes only 16 of the Northern States (assuming fairly, however, that the death rate in the other Northern States is the same), it seems reasonably safe to conclude that the death rate from malaria for the whole United States must surely amount to 15 per 100,000. It is probably greater than this, since the statistics from the South are city statistics, and malaria is really a country disease. Thus it is undoubtedly safe to assume that the death rate for the whole population of the United States is in the neighborhood of 15 per 100,000. This would give an annual death rate from malaria of nearly 12,000 and a total number of deaths for the 8-year period 1900-1907 of approximately 96,000. But with malaria perhaps as with no other disease does the death rate fail to indicate the real loss from the economic point of view. A man may suffer from malaria throughout the greater part of his life, and his productive capacity may be reduced from 50 to 75 per cent, and yet ultimately he may die from some entirely different immediate cause. In fact, the predisposition to death from other causes brought about by malaria is so marked that if, in the collection of vital statis- tics, 1t were possible to ascribe the real influence upon mortality that malaria possesses, this disease would have a very high rank in mor- tality tables. Writing of tropical countries, Sir Patrick Manson declares that malaria causes more deaths, and more predisposition to death by inducing cachectic states predisposing to other affections, than all the other parasites affecting mankind together. Moreover, it has been shown that the average life of the worker in malarious | MOSQUITOES AND MALARIA. iT places is shorter and the infant mortality higher than in healthy places, But, aside from this vitally important aspect of the subject, the effect of malaria in lessening or destroying the productive capacity of the individual is obviously of the utmost importance, and upon the population of a malarious region is enormous, even under modern conditions and in the United States. It has been suggested that the depopulation of the once thickly settled Roman Campagna was due to the sudden introduction of malaria by the mercenaries of Scylla and Marius. Celli, in 1900, states that owing to malaria about 5,000,000 acres of land in Italy remain—not uncultivated, but certainly very imperfectly cultivated. Then also, in further example, in quite recent years malaria entered and devastated the islands of Mauritius and Réunion, practically destroying for a time the productiveness of these rich colonies of Great Britain and France. Creighton, in his article on malaria in the Encyclopedia Britannica, states that this disease “ has been estimated to produce one-half of the entire mortality of the human race; and inasmuch as it is the most frequent cause of sickness and death in those parts of the globe that are most densely populated, the estimate may be taken as at least rhetorically correct.” @ Is it possible to make any close estimate of the ratio between the number of deaths from malaria and the number of cases of the same malady? No perfectly sound basis for such an estimate is apparent. In the English translation of Celli’s work on “ Malaria According to the New Researches,” published in London in 1900, it is stated that the mortality from malaria in Italy from 1887 to 1898 varied from 21,033 in the first-named year to 11,378 in the last-named year, and the mean mortality for the period is assumed to be about 15,000. In 1896 a count of the patients in the hospitals in Rome was made, and the mortality rate of 7.75 per thousand of the actual patients was established. Calculating then on this basis, and at this rate, the num- ber of cases per year for Italy was placed at about 2,000,000. Accord- ing to this estimate, and with the average mortality for the United States of 12,000 as above indicated, the approximate number of cases for the United States would be about 1,550,000. It seems obvi- ous, however, that Celli, in using the basis of hospital patients only, must have underestimated the number of cases for the Kingdom, since of the people in the country suffering from malaria the propor- tion entering the hospital must be relatively small. Therefore the death rate from malaria of malarial patients in the hospital must be greater than the death rate from malaria of the people who suffer from this disease in the whole country. In fact, so great must this L @See “Darwinism and Malaria,’ by R. G. Eccles, M. D., Medical Record, New York, January 16, 1909, pp. 85-98. 12 LOSS THROUGH INSECTS THAT CARRY DISEASE. discrepancy necessarily be that it would not seem at all unlikely to the writer if the number of persons suffering from malaria in Italy were in reality nearer 3,000,000 than 2,000,000. The same argument will hold for the United States, and more especially so since as a rule malaria in this country is of a lighter type than in Italy; in fact an estimate of 3,000,000 cases of malaria in the United States annually is probably by no means too high. It will not be an exaggeration to estimate that one-fourth of the produc- tive capacity of an individual suffering with an average case of ma- laria is lost. Accepting this as a basis, and including the loss through death, the cost of medicines, the losses to enterprises in malarious regions through the difficulty of securing competent labor, and other factors, it is safe to place the annual loss to the United States from malarial disease under present conditions at not less than one hundred millions of dollars. Celli has shown that in Italy the great railway industries, for example, feel the effect of malaria greatly. Accord- ing to accurate calculations one company alone, for 1,400 kilometers of railway and for 6,416 workmen in malarious zones, spends on ac- count of malaria 1,050,000 frances a year. The same writer states that the army in Italy from 1877 to 1897 had more than 300,000 cases of malaria. The loss to this country in the way of retardation of the develop- ment of certain regions, owing to the presence of malaria, is extremely great. Certain territory containing most fertile soil and capable of the highest agricultural productiveness is practically abandoned. With the introduction of proper drainage measures and antimosquito work of other character, millions of acres of untold capacity could be released from the scourge at a comparatively shght expenditure. These regions in the absence of malaria would have added millions upon millions to the wealth of the country. Drainage measures are now being initiated by the United States. Parties of engineers are being sent by the Government to make preliminary drainage sur- veys in the most prominent of these potentially productive regions. The following statement concerning the effect of malaria on the progress of this work has been made to the writer by Dr. George Otis Smith, director of the United States Geological Survey : “Tn one of the Southern States 11 topographic parties have been at work during the past field season. The full quota for these parties would be 55 men, but I believe that something over 100 men have been employed at different times during the season. While I have not exact figures before me, I feel warranted in the statement that at least 95 per cent of these employees have been sick, for periods rang- ing from a few days up to two weeks, in the hospital. Many of them have been able later to return to work, but at least 30 per cent had to leave the field permanently. Bv reason of this sickness the effi- MOSQUITOES AND MALARIA. 105} ciency of the parties was reduced, at a very conservative estimate, by 25 per cent. “Tn my recent visit in this field I found one man sick in each of the parties I saw and one man who had just returned from the hospital leaving the field for good. A similar state of things was reported from the other parties. I regard the sickness as practically all of a malarial nature, as extreme care was taken in all the camps to use nothing but boiled water except in a few instances where arte- sian water from great depths was available. In all the camps the tents have been screened, and in every case where the topographer has lived for any time ‘on the country’ there has been infection. As illustrating the value of the precautions generally taken by our camp parties, I might cite the fact that last year in West Virginia with 30 men living in camp, with typhoid fever prevalent in the neighborhood, no cases developed, while with 6 men living on the country where the same care could not be taken regarding the water supply, two cases of typhoid developed.” In estimating the weight of Doctor Smith’s statement, it must be borne in mind that the men of his field parties are exceptionally in- telligent and prepared to take all ordinary precautions. Throughout the region in question malaria is practically universal. The railroads suffer, and at the stations throughout the territory it is practically impossible to keep operators steadily at work. ‘This re- duction in efficiency in the surveying parties and in the local railroad officials is moreover probably very considerably less than the reduc- tion in the earning capacity of the entire population, which, however, is necessarily scanty. In an excellent paper entitled “ The relation of malaria to agricul- tural and other industries of the South,” published in the Popular Science Monthly for April, 1908, Prof. Glenn W. Herrick, then of the College of Agriculture of Mississippi, after a consideration of the whole field, concludes that malaria is responsible for more sick- ness among the white population of the South than any disease to which it is now subject. The following forcible statement referring to the States of Louisiana, Mississippi, Alabama, Georgia, and South Carolina is in Professor Herrick’s words: “ We must now consider briefly what 635,000 or a million cases of chills and fevers in one year mean. It is a self-evident truth that it means well for the physician. But for laboring men it means an immense loss of their time together with the doctors’ fees in many instances. If members of their families other than themselves be affected, it may also mean a loss of time together with the doctors’ fees. For the employer it means the loss of labor at a time perhaps when it would be of greatest value. If it does not mean the actual loss of labor to the employer it will mean a loss in the efficiency of 14 LOSS THROUGH INSECTS THAT CARRY DISEASE. his labor. To the farmers it may mean the loss of their crops by want of cultivation. It will always mean the noncultivation or imperfect cultivation of thousands of acres of valuable land. It means a listless activity in the world’s work that counts mightily against the wealth-producing power of the people. Finally it means from two to five million or more days of sickness with all its attendant distress, pain of body, and mental depression to some unfortunate individuals of those five States.” Referring to the Delta region in Mississippi, which les along the Mississippi River in the western part of the State of Mississippi, extending from the mouth of the Yazoo River north nearly to the Tennessee line, Herrick says that it is the second best farming land in the world, having only one rival, and that is the valley of the Nile. “ Still,” says Herrick, “ this land to-day, or at least much of it, can be bought at ten to twenty dollars an acre. Thousands of acres in this region are still covered with the primeval forest, and the bears and deer still roaming there offer splendid opportunities for the chase, as evidenced by the late visit of our Chief Executive to those regions for the purpose of hunting. Why is not this land thickly settled? And why is it not worth from two to five hundred dollars an acre? If it produces from one to two or more bales of cotton to an acre, and it does, it ought to be worth the above named figures. A bale of cotton to the acre can be produced for thirteen dollars, leaving a net profit of twenty to forty dollars for each bale, or forty to eighty or more dollars for each acre of land cultivated. Moreover, this land has been doing that for years, and will do it for years to come, without the addition of one dollar’s worth of fertilizer. Land that will produce a net profit of forty to eighty dollars an acre is a splendid investment at one, two, or even three hundred dollars an acre. Yet this land does not sell in the market for anything like so much, because the demand is not sufficient, for white people positively object to living in the Delta on account of malarial chills and fevers. A man said to me not long ago that he would go to the Delta that day if he were sure that his own life or the lives of the members of his family would not be shortened thereby. There are thousands exactly like him, and the only reason that these thousands do not go there to buy lands and make homes is on account of chills and fevers. But there is a time coming, and that not far distant, when malaria in the Delta will not menace the would-be inhabitants. When that time comes it will be the richest and most populous region in the United States.” Malaria is a preventable disease. It is possible for the human species to live and to thrive and to produce in malarious regions, but at a very considerable inconvenience and expense. The Italian inves- tigators, and especially Celli and his staff, have shown that by MOSQUITOES AND MALARIA. 6) screening the huts of the peasants on the Roman Campagna and by furnishing field laborers with veils and gloves when exposed to the night air, it is possible even in that famous hotbed of malaria to conduct farming operations with a minimum of trouble from the disease. Moreover, Koch and his assistants in German East Africa have shown that it is possible, by stamping out the disease among human beings by the free use of medicine, that a point can be gained where there is small opportunity for the malarial mosquitoes to become infected. Moreover, the work of the parties sent out by the Liverpool School of Tropical Medicine and other English organizations to the west coast of Africa has shown that by the treatment of malarial- mosquito breeding pools the pernicious coast fever may be greatly reduced. Again, the work of Englishmen in the Federated Malay States has shown that large areas may be practically freed from malaria. The most thorough and the most satisfactory of all meas- ures consists in abolishing the breeding places of the malarial mos- quitoes. In regions like the Delta of the Mississippi this involves extensive and systematic drainage, but in very many localities where the breeding places of the Anopheles mosquitoes can be easily eradi- cated, where they are readily located and are so circumscribed as to admit of easy treatment, it is possible to rid the section. of malaria at a comparatively slight expense. With a general popular appreciation of the industrial losses caused primarily by the malarial mosquito and secondarily by the forms which do not carry malaria, as indicated in the opening paragraphs, it is inconceivable that the comparatively inexpensive measures neces- sary should not be undertaken by the General Government, by the State governments, and by the boards of health of communities, just as it is inconceivable that the individual should suffer from malaria and from the attacks of other mosquitoes when he has individual preventives and remedies at hand. Large-scale drainage measures by the General Government involving large sections of valuable terri- tory have been planned and are practically under way; certain States, notably New Jersey and New York, are beginning to work ; communi- ties all over the country through boards of health are also beginning to take notice, while popular education regarding the danger from mosquitoes and in regard to remedial measures is rapidly spreading. But all of this interest should be intensified, and the importance of the work should be displayed in the most emphatic manner, and relief from malaria and other mosquito conditions should be brought about as speedily as possible. A few excellent examples of antimalarial work may be instanced. The latest reports on the measures taken to abolish malaria from Klang and Port Swettenham in Selangor, Federated Malay States, indicate the most admirable results. These measures were under- 16 LOSS THROUGH INSECTS THAT CARRY DISEASE. taken first in 1901 and 1902, and have been reported upon from time to time in the Journal of Tropical Medicine. The expenditure undertaken by the Government with a view to improving the health of the inhabitants of these towns has been fully justified by the results, which promise to be of permanent value. The total expendi- ture for the town of Klang down to the end of 1905 was £3,100 ($15,086), and the annual permanent expenditure is about £60 ($292) for clearing earth drains and £210 ($1,022) for town gardeners. For Port Swettenham the total expenditure to the end of 1905 was £7,000 ($34,065), and the annual cost of keeping up the drains, etc., is ap- proximately £40 ($195) for clearing earth drains, and £100 ($487) for town gardeners. The careful tabulation of cases and deaths and of the results of the examination of blood of children in especially drained areas indicates the following conclusions: (1) Measures taken systematically to destroy breeding places of mosquitoes in these towns, the inhabit- ants of which suffered terribly from malaria, were followed almost immediately by a general improvement in health and decrease in death rate. (2) That this was due directly to the work carried out and not to a general dying out of malaria in the district is clearly shown by figures pointing out that while malaria has practically ceased to exist in the areas treated it has actually increased to a considerable extent in other parts of the district where antimalarial measures have not been undertaken. The statistics for 1905 are even more favorable than those for 1902, which gives a very strong evidence in favor of the permanent nature of the improvement carried out. In fact it seems as though malaria has been permanently stamped out at Klang and Port Swettenham by work undertaken in 1901, and this experience in the Malay States should be of value to those responsible for the health of communities similarly situated in many other parts of the world. Another striking example of excellent work of this kind is found in the recently published report on the suppression of malaria in Ismailia, issued under the auspices of the Compagnie Universelle du Canal Maritime de Suez. Ismailia is now a town of 8,000 inhabit- ants. It was founded by De Lesseps in April, 1862, on the borders of Lake Timsah, which the Suez Canal crosses at mid-distance be- tween the Red Sea and the Mediterranean. Malarial fever made its appearance in very severe form in September, 1877, although the city had up to that time been very healthy, and increased so that since 1886 almost all of the inhabitants have suffered from the fever. In 1901 an attempt to control the disease was made on the mosquito basis, and this attempt rapidly and completely succeeded, and after two years of work all traces of malaria disappeared from the city. The work was directed not only against Anopheles mosquitoes, but MOSQUITOES AND YELLOW FEVER. Ay against other culicids, and comprised the drainage of a large swamp and the other usual measures. The initial expense amounted to 50,000 frances ($9,650), and the annual expenses since have amounted to about 18,300 frances ($3,532). The results may be summarized about as follows: Since the be- ginning of 1903 the ordinary mosquitoes have disappeared from Ismailia. Since the autumn of 1903 not a single larva of Anopheles has been found in the protected zone, which extends to the west for a distance of 1,000 meters from the first houses in the Arabian quarter and to the east for a distance of 1,800 meters from the first houses in the European quarter. After 1902 malarial fever obviously began to decrease, and since 1903 not a single new case of malaria has been found in Ismailia. A very efficient piece of antimalarial work was accomplished in Havana during the American occupation of 1901 to 1902, incidental in a way to the work against yellow fever. An Anopheles brigade of workmen was organized under the sanitary officer, Doctor Gorgas, for work along the small streams, irrigated gardens, and similar places in the suburbs, and numbered from 50 to 300 men. No exten- sive drainage, such as would require engineering skill, was attempted, and the natural streams and gutters were simply cleared of obstruc- tions and grass, while superficial ditches were made through the irri- gated meadows. Among the suburban truck gardens Anopheles bred everywhere, in the little puddles of water, cow tracks, horse tracks, and similar depressions in grassy ground. Little or no oil was used by the Anopheles brigade, since it was found in practice a simple _ matter to drain these places. At the end of the year it was very difli- cult to find water containing mosquito larve anywhere in the suburbs, and the effect upon malarial statistics was striking. In 1900, the year before the beginning of the mosquito work, there were 325 deaths from malaria; in 1901, the first year of the mosquito work, ‘171 deaths; in 1902, the second year of mosquito work, 77 deaths. Since 1902 there has been a gradual though slower decrease, as fol- lows: 1903, 51; 1904, 44; 1905, 32; 1906, 26; 1907, 23. These results, although less striking than those from Ismailia, involved a smaller expense in money and show surely an annual saving of 300 lives, and undoubtedly a corresponding decrease in the number of malarial cases, which may be estimated upon our earlier basis at something less than 40,000. YELLOW FEVER. Yellow fever has prevailed endemically throughout the West In- dies and in certain regions on the Spanish Main virtually since the discovery of America. Barbados, Jamaica, and Cuba suffered epidemics before the middle of the seventeenth century. There were $3434— Bull. 78 —09——3 Mss LOSS THROUGH INSECTS THAT CARRY DISEASE. outbreaks in Philadelphia, Charleston, and Boston as early as 1692, and for a hundred years there were occasional outbreaks, culminat- ing in the great Philadelphia epidemic of 1793. Northern cities were able, by rigid quarantine measures, to prevent great epidemics after the early part of the nineteenth century, but from the West Indies the disease was occasionally introduced and prevailed from time to time epidemically in the Southern States. In 1853 it raged through- out this region, New Orleans alone having a mortality of 8,000. The last widespread epidemic occurred in 1878, chiefly in Louisiana, Ala- bama, and Mississippi, but spreading up the Mississippi Valley as far as Cairo, UL, and attacking with virulence the city of Memphis, Tenn. In this year there were 125,000 cases and 12,000 deaths. In 1882 there were 192 deaths at Pensacola; in 1887, 62 deaths in the Southern States; in 1893, 52 deaths; in 1897, 484; in 1898, 2,456 cases with 117 deaths; in 1903, 139 deaths were recorded, mostly at Laredo, Tex., and in 1905 there was a serious outbreak at New Orleans and in neighboring towns, including one locality in Mississippi, in which 911 deaths were recorded for the whole country. The actual loss of life from yellow fever during all these years, when compared with the loss from other diseases, nas been compara- tively slight, but the death rate is perhaps the most insignificant fea- ture of the devastation which yellow fever epidemics have produced, and the disease itself has been but a small part of the affliction which it has brought to the Southern States. The disease once discovered in epidemic form, the whole country has become alarmed; commerce in the affected region has come virtually to a standstill; cities have been practically deserted; people have died from exposure in camping out in the highlands; rigid quarantines have been established; inno- cent persons have been shot while trying to pass these quarantine lines; all industry for the time has ceased. The commerce of the South during the epidemic of 1878, for example, fell off 90 per cent, and the hardships of the population can not be estimated in monetary terms. With such industrial and commercial conditions existing from Texas to South Carolina, many industries at the North have suffered, and, in fact, the effect of a yellow fever summer in the South has been felt not only all over the United States, but in many other portions of the world. All these conditions, as bad as they have been, do not sum up the total loss to the national prosperity during past years. Cities like Galveston, New Orleans, Mobile, Memphis, Jacksonville, and Charles- ton, subject to occasional epidemics, as they have been in the past, have not prospered as they should have done. Their progress has been greatly impeded by this one cause, and thus the industrial development of the entire South has been greatly retatded. MOSQUITOES AND YELLOW FEVER. 19 Physicians have been theorizing about the cause of yellow fever from the time when they began to treat it. It was thought by many that it was carried in the air; by others that it was conveyed by the clothing, bedding, or other articles which had come in contact with a yellow-fever patient. There were one or two early suggestions of the agency of mosquitoes, but practically no attention was paid to them, and they have been resurrected and considered significant only since the beginning of the present century. With the discovery of the agency of micro-organisms in the causation of disease, a search soon began for some causative germ. Many micro-organisms were found in the course of the autopsies, and many claims were put forth by investigators. All of these, however, were virtually set at rest by Sternberg in his “ Report on the Etiology and Prevention of Yellow Fever,” published in 1890, but a claim made by Sanarelli in June, 1897, for a bacillus which he called Bacillus icteroides received con- siderable credence, and in 1899 it was accepted in full by Wasden and Geddings, of the United States Marine-Hospital Service, who re- ported that they had found this bacillus in thirteen or fourteen cases of yellow fever in the city of Havana. There is no evidence, how- ever, that this bacillus has anything to do with yellow fever. In 1881 Finlay, of Havana, proposed the theory that yellow fever, whatever its cause may be, is conveyed by means of Culex (now Stegomyia) fasciatus (now calopus). Subsequently he published several im- portant papers, in which his views were modified from time to time, and in the course of which he mentioned experiments with 100 indi- viduals, producing 3 cases of mild fever. None of the cases, however, was under his full control, and the possibility of cther methods of contracting the disease was not excluded. Therefore, his theory, while it was received with interest, was not considered to be proved. In 1900 came the beginning of the true demonstration. An army board was appointed by Surgeon-General Sternberg for the purpose of investigating the acute infectious diseases prevailing in the island of Cuba. The result achieved by this board, consisting of Reed, Carroll, Lazear, and Agramonte, was a demonstration that yellow _ fever is carried by Stegomyia calopus, and their ultimate demonstra- tion was so perfect as to silence practically all expert opposition. The Third International Sanitary Convention of the American Republics unanimously accepted the conclusion that yellow fever is carried by this mosquito, and that the Stegomyia constitutes the only known means by which the disease is spread. To-day, after abundant addi- tional demonstration, the original contention of Reed, Carroll, and Agramonte (Lazear having died in the course of the experiments) is a part of the accepted knowledge of the medical world. The im- portance of the discovery can not be overestimated, and its first demonstration was followed by antimosquito measures in the city 20 LOSS THROUGH INSECTS THAT CARRY DISEASE. of Havana, undertaken under the direction of Gorgas, with startling results. Yellow fever had been endemic in Havana for more than one hun- dred and fifty years, and Havana was the principal source of infee- tion for the rest of Cuba. Other towns in Cuba could have rid themselves of the disease if they had not been constantly reinfected from Havana. By ordinary sanitary measures of cleanliness, im- proved drainage, and similar means the death rate of the city was reduced, from 1898 to 1900, from 100 per thousand to 22 per thou- sand; but these measures had no effect upon yellow fever, this disease increasing as the nonimmune population following the Spanish war increased, and in 1900 there was a severe epidemic. Stegomyia calopus was established as the carrier of the fever early in 1901, and then antimosquito measures were immediately begun. Against adult mosquitoes no general measures were attemp- ted, although screening and fumigation were carried out in quarters occupied by yellow-fever patients or that had been occupied by vellow-fever patients. It was found that the Stegomyia bred prin- cipally in the rain-water collections in the city itself. The city was divided into about 30 districts, and to each district an inspector and two laborers were assigned, each district containing about a thousand houses. An order was issued by the mayor of Havana requiring all collections of water to be so covered that mosquitoes could not have access, a fine being imposed in cases where the order was not obeyed. The health department covered the rain-water barrels of poor fami- lies at public expense. All cesspools were treated with petroleum. All receptacles containing fresh water which did not comply with the law were emptied and on the second offense destroyed. The result of this work thoroughly done was to wipe out yellow fever in Havana, and there has not been a certain endemic case since that time. In the New Orleans epidemic of 1905, a striking illustration of the value of thisrecently acquired mosquito-transmission knowledge is seen. The presence of yellow fever in the city was first recognized about the 12th of July, and the plan of campaign adopted by the Board of Health under Dr. Quitman Kohnke, from the beginning was based on the mosquito conveyance of the disease. Available funds were rapidly exhausted, however, and on the 12th of August the Public Health and Marine-Hospital Service was put in charge of the situation and pro- vided with ample means. By that time the increase in the new cases and deaths rendered it practically certain that the disease was as wide- spread as during the terrible epidemic of 1878. There had been up to that time 142 deaths from a total of 913 cases, as against 152 deaths from a total of 519 cases in 1878. The work for the rest of the sum- mer was continued with great energy under Doctor White, and the measures were based almost entirely upon a warfare against the yel- low-fever mosquito. The disease began almost immediately to abate, and the result at the close of the season indicated 460 deaths, as against 4,046 in 1878, a virtual saving of over 3,500 lives. The WORK AGAINST MOSQUITOES IN PANAMA. PAS following table of deaths from yellow fever in New Orleans from 1847 to 1905 points out most strikingly the value of this antimosquito work: TABLE II1.—Comparative table of deaths from yellow fever in New Orleans dur- ing various years. , Year : Month. = a SSS SS 147. 1848. | 1853. 1854. | 1855. | 1858. 1867. 1878. 1905. WDA GS SEB RSS Sato aS CREE CECE eee | eee + Ai Sis RA | MPN a ES | epee ech oe a Ol ae ee Se IS) = je eee Noose ccs 4 | 31 2 5- 2 Or iecees tet RaSee ce Linky 5 Rae ES ee eae aaa | 74 33 | 1,521 29 382 132 11 26 35 MTEUIS Gy is 4 a ahs Searc 965 200 5, 1383 | 532 1, 286 1,140 255 1, 025 236 DODICMIDER sc osc cals secioc- 4S 1,100 467 982 | 1, 234 874 2, 204 1, 637 1,780 107 CCPSERCT Cf) ie a ne ney ae oa a 198 126 147 | 490 97 ali ye) 1, 072 1, 065 59 WOmenIDer cate loose eee ok 12 20 28 | 131 19 224 103 147 23 MeCOntpernas- Us ee tee ass. LOW eece eae 4 | 7 vi 15 26 Oe Months unknown.......... 445 VA lege ees eee te see eae Rr el la ee 2p ge bo ME Lee aor ito) C2 ae ieee ae era 2, 804 | 872 | 7,848 | 2,425 | 2,670] 4,854] 3,107] 4,046 460 The epidemics of 1848, 1854, and 1855 are least comparable with that of 1905 because they immediately succeeded severe epidemics to which were due very many immunes. The population of New Orleans by the United States Census was 130,565 in 1850; 168,675 in“1860; 191,418 in 1870; 216,090 in 1880, and 287,104 in 1900. WORK ON THE ISTHMUS OF PANAMA. The United States Government has very properly used the services of Colonel Gorgas, who was in charge of the eminently successful work at Havana, by appointing him chief sanitary officer of the Canal Zone during the digging of the canal. In 1904 active work was begun, and Colonel Gorgas was fortunate in having the services of Mr. Le Prince, who had been chief of his mosquito brigades in Havana, _and therefore was perfectly familiar with antimosquito methods. In Panama, as in Havana, the population had depended principally upon rain water for domestic purposes, so that every house had cis- terns, water barrels, and such receptacles for catching and storing rain water. The city was divided up into small districts with an in- spector in charge of each district. This inspector was required to cover his territory at least twice a week and to make a report upon each building with regard to its condition as to breeding places of mosquitoes. All the cisterns, water barrels, and other water recepta- cles in Panama were covered as in Havana, and in the water barrels spigots were inserted so that the covers would not have to be taken off. Upon first inspection, in March, 4,000 breeding places were reported. At the end of October less than 400 containing larve were recorded. This gives one a fair idea of the consequent rapid 22 LOSS THROUGH INSECTS THAT CARRY DISEASE. decrease in the number of mosquitoes in the city. These opera- tions were directed primarily against the yellow-fever mosquito, and incidentally against the other common species that inhabit raim-water barrels. Against the Anopheles in the suburbs the same kind of work was done as was done in Havana, with exceptionally good results. The same operations were carried on in the villages between Pan- ama and Colon. There are some twenty of these villages, running from 500 to 3,000 inhabitants each. Not a single instance of failure has occurred in the disinfection of these small towns, and the result of the whole work has been the apparent elimination of yellow fever and the very great reduction of malarial fever. The remarkable character of these results can only be judged accu- rately by comparative methods. It is well known that during the French occupation there was an enormous mortality among the European employees, and this was a vital factor in the failure of the work. Exact losses can not be estimated, since the work was done under 17 different contractors. These contractors were charged $1 a day for every sick man to be taken care of in the hospital of the company. Therefore it often happened that when a man became sick his employer discharged him, so that he would not have to bear the expense of hospital charges. There was no police patrol of the territory and many of these men died along the line. Colonel Gorgas has stated that the English consul, who was at the Isthmus during the period of the French occupation, 1s inclined to think that more deaths of employees occurred out of the hospital than in it. A great many were found to have died along the roadside while en- deavoring to find their way to the city of Panama. The old superin- tendent of the French hospital states that one day 3 of the medical staff died from yellow fever, and in the same month 9 of the medical staff. Thirty-six Roman Catholic sisters were brought over as nurses, and 24 died of yellow fever. On one vessel 18 young French engi- neers came over, and in a month after their arrival all but one died. Now that the relation of the mosquito to yellow fever is well under- stood, it was found during the first two years under Doctor Gorgas that, although there were constantly one or more yellow-fever cases in the hospital, and although the nurses and physicians were all non- immunes, not a single case of yellow fever was contracted in that way. ‘The nurses never seemed to consider that they were running any risk in attending yellow fever cases night and day in screened wards, and the wives and families of officers connected with the hos- pital lived about the grounds, knowing that yellow fever was con- stantly being brought into the grounds and treated in near-by build- ings. Americans, sick from any cause, had no fear when being treated in beds immediately adjoining those of yellow-fever pa- tients. Colonel Gorgas and Doctor Carter lived in the old ward THE TYPHOID FLY, OR HOUSE FLY. 23 used by the French for their officers, and Colonel Gorgas thinks it safe to say that more men had died from yellow fever in that build- ing under the French régime than in any other building of the same capacity at present standing. He and Doctor Carter had their wives and children with them, which would formerly have been considered the height of recklessness, but they looked upon themselves, under the now recognized precautions, as being as safe, almost, as they would have been in Philadelphia or Boston. No figures of the actual cost of the antimosquito work, either in Havana or in the Panama Canal Zone, are accessible to the writer, but it is safe to say that it was not exorbitant, and that it was not beyond the means of any well-to-do community in tropical regions. THE TYPHOID FLY, COMMONLY KNOWN AS THE HOUSE FLY. The name “typhoid fly” is here proposed as a substitute for the name “house fly,” now in general use. People have altogether too long considered the house fly as a harmless creature, or, at the most, simply a nuisance. While scientific researches have shown that it is a most dangerous creature from the standpoint of disease, and while popular opinion is rapidly being educated to the same point, the retention of the name house fly is considered inadvisable, as perpetu- ating in some degree the old ideas. Strictly speaking, the term “typhoid fly” is open to some objection, as conveying the erroneous idea that this fly is solely responsible for the spread of typhoid, but considering that the creature is dangerous from every point of view, and that it is an important element in the spread of typhoid, it seems advisable to give it a name which is almost wholly justified and which conveys in itself the idea of serious disease. Another repul- sive name that might be given to it is “manure fly,” but recent researches have shown that it is not confined to manure as a breeding place, although perhaps the great majority of these flies are born in horse manure. For the end in view, “ typhoid fly ” is considered the best name. The true connection of the so-called house fly with typhoid fever and the true scientific evidence regarding its réle as a carrier of that disease have only recently been worked out. Celli in 1888 fed flies with pure cultures of the typhoid bacillus, and examined their contents and dejections microscopically and culturally. Inocu- lations of animals were also made, proving that the bacilli which passed through flies were virulent. Dr. George M. Kober, familiar with Celli’s researches, in his report on the prevalence of typhoid fever in the District of Columbia, published in 1895, called especial attention to the danger of the contamination of food supplies by 24 LOSS THROUGH INSECTS THAT CARRY DISEASE. flies coming from the excreta of typhoid patients. The prevalence of typhoid fever in the concentration camps of the United States Army in the summer of 1898 brought about the appointment of an army board of medical officers consisting of Drs. Walter Reed, U. S. Army, Victor C. Vaughan, U. 8. Volunteers, and E. O. Shakespeare, U. S. Volunteers, to investigate the causes. The abstract of the report of this board, published in 1900, contains (p. 183) the following conclu- sions with regard to flies: “Flies undoubtedly served as carriers of the infection. “Flies swarmed over infected fecal matter in the pits and then visited and fed upon the food prepared for the soldiers at the mess tents. In some instances where lime had recently been sprinkled over the contents of the pits, flies with their feet whitened with hme were seen walking over the food. “Tt is possible for the fly to carry the typhoid bacillus in two ways. In the first place, fecal matter containing the typhoid germ may adhere to the fly and be mechanically transported. In the second place, it is possible that the typhoid bacillus may be carried in the digestive organs of the fly and may be deposited with its excrement.” Doctor Vaughan, of the board just mentioned, in a paper read be- fore the annual meeting of the American Medical Association at Atlantic City, N. J., June 6, 1900, gives the following additional rea- sons for believing that flies were active in the dessemination of typhoid fever: “Officers whose mess tents were protected by means of screens suffered proportionately less from typhoid fever than did those whose tents were not so protected. “Typhoid fever gradually disappeared in the fall of 1898, with the approach of cold weather, and the consequent disabling of the fly.” There were also many important conclusions which bear upon the fly question. For example, it was shown that every regiment in the United States service in 1898 developed typhoid fever, nearly all of them within eight weeks after assembling in camps. It not only appeared in every regiment in the service, but it became epidemic both in small encampments of not more than one regiment and in the larger ones consisting of one or more corps. All encampments located in the Northern as well as in the Southern States exhibited typhoid in epidemic form. The miasmatic theory of the origin of typhoid fever and the pythogenic theory“ were not supported by the investigations of the commission, but the doctrine of the specific @This theory is founded upon the belief that the colon germ may undergo a ripening process by means of which its virulence is so increased and altered that it may be converted into the typhoid bacillus or at least may become the active agent in the causation of typhoid fever. THE TYPHOID FLY, OR HOUSE FLY. 25 origin of the fever was confirmed. The conclusion was reached that the fever is disseminated by the transference of the excretions of an infected individual to the alimentary canals of others, and that a man infected with typhoid fever may scatter the infection in every latrine or regiment before the disease is recognized in himself, while germs may be found in the excrement for a long time after the apparently complete recovery of the patient. Infected water was not an important factor in the spread of typhoid in the national encampments of 1898, but about one-fifth of the soldiers in the national encampments in the United States during that summer de- veloped this disease, while more than 80 per cent of the total deaths were caused by typhoid. In 1899 the writer began the study of the typhoid or house fly under both country and city conditions. He made a rather thorough investigation of the insect fauna of human excrement, and made a further investigation of the species of insects that are attracted to food supplies in houses. In a paper entitled “A Contribution to the Study of the Insect Fauna of Human Excrement (with special refer- ence to the spread of typhoid fever by flies) ,” published in the Pro- ceedings of the Washington Academy of Sciences, Volume II, pages 541-604, December 28, 1900, he showed that 98.8 per cent of the whole number of insects captured in houses throughout the whole country under the conditions indicated above were J/uscu domestica, the typhoid or house fly. He showed further that this fly, while breeding most numerously in horse stables, is also attracted to human excre- ment and will breed in this substance. It was shown that in towns where the box privy was still in existence the house fly is attracted to the excrement, and, further, that it is so attracted in the filthy regions of a city where sanitary supervision is lax and where in low alleys and corners and in vacant lots excrement is deposited by dirty people. He stated that he had seen excrement which had been deposited over- night in an alleyway in South Washington swarming with flies under the bright sunlight of a June morning (temperature 92° F.), and that within 30 feet of these deposits were the open windows and doors of the kitchens of two houses kept by poor people, these two houses being only elements in a long row. The following paragraph is quoted from the paper just cited: “ Now, when we consider the prevalence of typhoid fever and that virulent typhoid bacilli may occur in the excrement of an individual for some time before the disease is recognized in him, and that the same virulent germs may be found in the excrement for a long time after the apparent recovery of a patient, the wonder is not that ty- phoid is so prevalent but that it does not prevail to a much greater 26 LOSS THROUGH INSECTS THAT CARRY DISEASE. extent. Box privies should be abolished in every community. The depositing of excrement in the open within town or city limits should be considered a punishable misdemeanor in communittes which have not already such regulations, and it should be enforced more rigor- ously in towns in which it is already a rule. Such offenses are gener- ally committed after dark, and it is often difficult or even impossible to trace the offender; therefore, the regulation should be carried even further and require the first responsible person who notices the de- posit to immediately inform the police, so that it may be removed or covered up. Dead animals are so reported; but human excrement is much more dangerous. Boards of health in all communities should look after the proper treatment or disposal of horse manure, primarily in order to reduce the number of house flies to a minimum, and all regulations regarding the disposal of garbage and foul matter should be made more stringent and should be more stringently enforced.” In the opening sentence of the paragraph just quoted attention was called to the activity of bacilli in excreta passed by individuals after apparent recovery from typhoid. Since the paper in question was published, more especial attention has been drawn by medical men to this point, and it has been shown that individuals who are chronic spreaders of the typhoid germs are much more abundant than was formerly supposed. Dr. George A. Soper recently discovered a strik- ing case of this kind in the person of a cook employed successively by several families in the vicinity of New York City, with the result that several cases of typhoid occurred in each of these families. In a paper by Doctor Davids and Professor Walker, read before the Royal Sanitary Institute of London during the present season, the history was given of four personal carriers of typhoid who had com- municated the disease to a number of people. These four carriers were detected in one city within a few months, and from this fact it can be argued with justice that such cases are comparatively numer- ous. This being true, the presence of unguarded miscellaneous human excreta deposited in city suburbs, in vacant lots, and in low alleyways intensifies to a very marked degree the danger that the food will become contaminated with typhoid bacilli by means of the ty- phoid or house fly. It is known, too, that the urine of persons who have suffered from typhoid fever often contains active typhoid bacilli for several weeks after the patients have recovered ; consequently this also is a source of danger. The importance of the typhoid fly as a carrier of the disease in army camps, as shown in the Spanish war and in the Boer war and in the ‘amps of great armies of laborers engaged in gigantic enterprises like the digging of the Panama canal, is obvious, but what has just been stated indicates that even under city conditions the influence of this fly in the spread of this disease has been greatly underestimated. It is not claimed that under city conditions the house fly becomes by this argument a prime factor in the transfer of the disease, but it must obviously take a much higher relative rank among typhoid conveyers THE TYPHOID FLY, OR HOUSE FLY. 27 than it has hitherto assumed. Perhaps even under city conditions it must assume third rank—next to water and milk.¢ It is not alone as a carrier of typhoid that this fly is to be feared. In the same way it may carry nearly all the intestinal diseases. It is a prime agent in the spreading of summer dysentery, and in this way is unquestionably responsible for the death of many children in sum- mer. One of the earliest accurate scientific studies of the agency of insects in the transfer of human disease was in regard to flies as spreaders of cholera. The belief in this agency long preceded its actual proof. Dr. G. E. Nicholas, in the London Lancet, Volume IJ, 1873, page 724, is quoted by Nuttall as writing as follows regarding the cholera prevailing at Malta in 1849: “ My first impression of the possibility of the transfer of the disease by flies was derived from the observation of the manner in which these voracious creatures, present in great numbers, and having equal access to the dejections and food of patients, gorged themselves indiscriminately and then disgorged themselves on the food and drinking utensils. In 1850 the Superb, in common with the rest of the Mediterranean squadron, was at sea for nearly six months; during the greater part of the time she had cholera on board. On putting to sea, the flies were in great force; but after a time the flies gradually disappeared, and the epidemic slowly subsided. On going into Malta Harbor, but without com- municating with the shore, the flies returned in greater force, and the cholera also with increased violence. After more cruising at sea, the flies disappeared gradually with the subsidence of the disease.” Accurate scientific bacteriological observations by 'Tizzoni and Cattani in 1886 showed definitely active cholera organisms in the dejecta of flies caught in the cholera wards in Bologna, Italy. These observations were subsequently verified and extended by Simonds, Offelmann, Macrae, and others. With tropical dysentery and other enteric diseases practically the same conditions exist. In a report by Daniel D. Jackson to the committee on pollution, of the Merchants’ Association in New York, published in December, 1907, the results of numerous observations upon the relation of flies to intestinal diseases are published, and the relation of deaths from intestinal diseases in New York City to the @Dr. John R. Mohler, of the Bureau of Animal Industry, U. S. Department of Agriculture, informs the writer that investigations made in his office show that typhoid bacilli will live in butter under common market conditions for 151 days and still be able to grow when transferred to suitable conditions. In milk under market conditions they retain active motility for 20 days, after which time there is a gradual lessening in numbers until, on the forty-third day of the test, they disappear from view. Atcertain seasons_of the year large num- bers of flies collect upon the vats in which milk and cream are being stored in dairies and creameries. Many of the flies fall in, their bodies being strained out when the cream is sent to the churn. If any of these flies carry typhoid bacilli these are washed off by the milk and remain in the butter or cheese made from it. Thus the eating of butter contaminated in this way may account for very many cases of typhoid fever the cause of which can not be otherwise traced. 28 LOSS THROUGH INSECTS THAT CARRY DISEASE. activity and prevalence of the common house fly is shown not only by repeated observations but also by an interesting plotting of the — curve of abundance of flies in comparison with the plotted curve of abundance of deaths from intestinal diseases, indicating that the greatest number of flies occurred in the weeks ending July 27 and August 3; also, that the deaths from intestinal diseases rose above the normal at the same time at which flies became prevalent, culmi- nated at the same high point, and fell off with shght lag at the time of the gradual falling off of the prevalence of the insects. Similar studies have been carried on during the summer of 1908 in the city of Washington, and the curve of typhoid-fly abundance for the whole city, as well as that for a district comprising eight city squares in which intensive studies have been made both of flies and of disease, will be plotted at the close of the season. At the time of present writing this work has not been completed. The typhoid fly also possesses importance as a disseminator of the bacilli of tuberculosis. In a papet by Dr. Frederick T. Lord, of Boston, reprinted from the Boston Medical and Surgical Journal for December 15, 1904, pages 651-654, the following conclusions are reached : “1. Fhes may ingest tubercular sputum and excrete tubercle ba- cilli, the virulence of which may last for at least fifteen days. “2. The danger of human infection from tubercular flyspecks is by the ingestion of the specks on food. Spontaneous liberation of tubercle bacilli from flyspecks is unlikely. If mechanically dis- turbed, infection of the surrounding air may occur. “As a corollary to these conclusions, it is suggested that— “3. Tubercular material (sputum, pus from discharging sinuses, fecal matter from patients with intestinal tuberculosis, ete.) should be carefully protected from flies, lest they act as disseminators of the tubercle bacilli. “4. During the fly season greater attention should be paid to the screening of rooms and hospital wards containing patients with tuberculosis and laboratories where tubercular material is examined. “5. As these precautions would not eliminate fly infection by patients at large, foodstuffs should be protected from flies which may already have ingested tubercular material.” From all these facts it appears that the most important part played by the typhoid fly or house fly in the human economy is to carry bacteria from one place to another. The following table and com- ments are taken from Bulletin No. 51 (April, 1908), of the Storrs Agricultural Experiment Station, Storrs, Conn., entitled ‘“ Sources of Bacteria in Milk,” by W. M. Esten and C. J. Mason: THE TYPHOID FLY, OR HOUSE FLY. 29 Tasie I]1.—Sources of bacteria from flies. ' ee apa ; Baa B em Coli-xro- . - Tota Total aci iquefy- iquetfy- as genes. Date. Source. number. | bacteria. | ing bac- | ing bac- Geant Group A. teria. teria. Glaser Class 2. 1907. July 27 | (a) 1 fly, bacteriological | la DOLaLOLY jo a-c-e ice = c= 3, 150 250 600 TOO! ards ood dis eeiloeeeee cra July 27 | (b) 1 fly, bacteriological lEN DOME Aas -opeeaneonee 550 100 0 Qi ligase sal Beecaesee Aug. 6 | (c) 19 cow-stable flies ..... 7, 980, 000 220, 000 0 205000) 2s -kb sesee Se BPE ae Average per fly...... 420, 000 11, 600 0 LE OOO) |!) so2tss reac Sz eosccces Aug.14 | (d) 94 swill-barrel flies. .../155, 000,000 | 8,950,000 0 0 | 4,320,000 | 4,630, 000 Average per fly...... 1, 660, 000 95, 300 0 0 46, 000 49, 300 Aug.14 | (e) 144 pigpen flies -....... 133,000,000 | 2,110,000 | 100,000 | 266,000} 933,000 | 1,176, 000 Average per fly...... 923, 000 18, 700 700 1, 150 6, 500 12, 200 Sept. 4 | (f) 18 swill-barrel flies. -../118, 800, 000 |40, 480, 000 0 14, 500, 000 |10, 480, 000 |30, 000, 000 Average per fly....-. 6, 600, 000 | 2, 182, 000 0 804, 000 582,000 | 1,600,000 Sept.21 | (g) 30dwelling-house flies.| 1, 425, 000 125, 000 0 IBA G 0 Dl ease See eel sere cacioc Average per fly...... 47, 580 4, 167 0 Bie || Na cene etme 4 | eae sets Sept.21 | (h) 26dwelling-house flies.| 22, 880,000 |22,596,000 | 120,000 S45000)) Se emir J 53| 5 Sxteeerae Average per fly...-... 880, 000 869, 000 4, 600 SOO GE te cee 2 te ceemoeee Sept.27 | (¢) 110 dwelling-house flies.| 35, 500,000 |13, 670, 000 |8, 840, 000 ADH OOO See Sat cede Saas Average per fly.....- 322, 700 124, 200 80, 300 WL OOW ssteiercterteleclisie ote cees Aug.20 | (7) 1 large bluebottle LOW dl Wists Clone sas cis seine 308, 700 (Gyre ER Se er ethene ecard cle area acet lo scieammcers Total average of 414 flies..| 1,222,570 367, 300 | 7,830 | TOON Nene eea: koma meee Average per cent of 414 fiieatee ey. eck ee seen ce Bs Espen ae 30 6 3 esas cere Bese Average per fly of 256 flies, experiments (d), (Gwandi Gf) eees 3, 061, 000 765, 000 230 | 268,700] 211,500] 553,800 Average per cent of 256 flies, experiments (d), He MCE) SIT OUN Gf ecm seer cal ome ncice eae e | DA pte seater 8 a) 18 «2,200 mold spores. “ From the above table the bacterial population of 414 flies is pretty well represented. The domestic fly is passing from a disgusting nui- sance and troublesome pest to a reputation of being a dangerous enemy to human health. A species of mosquito has been demon- strated to be the cause of the spread of malaria. Another kind of mosquito is the cause of yellow fever, and now the house fly is con- sidered an agency in the distribution of typhoid fever, summer com- plaint, cholera infantum, ete. “The numbers of bacteria on a single fly may range all the way from 550 to 6,600,000. Early in the fly season the numbers of bac- teria on flies are comparatively small, while later the numbers are comparatively very large. The place where flies live also determines largely the numbers that they carry. The average for the 414 flies was about one and one-fourth million bacteria on each. It hardly seems possible for so small a bit of life to carry so large a number ofi organisms. The method of the experiment was to catch the flies from the several sources by means of a sterile fly net, introduce them into a sterile bottle, and pour into the bottle a known quantity of steril- ized water, then shake the bottle to wash the bacteria from their bodies, to simulate the number of organisms that would come from a fly in falling into a lot of milk. In experiments ‘d,’ ‘e, and ‘f’ 30 LOSS THROUGH INSECTS THAT CARRY DISEASE. the bacteria were analyzed into four groups. The objectionable class, coli-wrogenes type, was two and one-half times as abundant as the favorable acid type. If these flies stayed in the pigpen vicinity there would be less objection to the flies and the kinds of organisms they carry, but the fly is a migratory insect and it visits everything * under the sun.’ It is almost impossible to keep it out of our kitchens, din- ing rooms, cow stables, and milk rooms. The only remedy for this rather serious condition of things is, remove the pigpen as far as pos- sible from the dairy and dwelling house. Extreme care should be taken in keeping flies out of the cow stable, milk rooms, and dwell- ings. Flies walking over our food are the cause of one of the worst contaminations that could occur from the standpoint of cleanliness and the danger of distributing disease germs.” The danger of the typhoid or house fly in the carriage of disease has thus been abundantly demonstrated. Further than this, it is an intolerable nuisance. With mosquitoes it necessitates an annual out- lay for window and door screens in the United States of not less than ten millions of dollars. As a carrier of disease it causes a loss of many millions of dollars annually. Dr. G. N. Kober, in a paper pre- pared for the Governors’ Conference on the Ceres vor of Natural Resources, held at the White House in May, 1908, entitled “ The Con- servation of Life and Health by Improved Water Supply,” presented figures showing that the decrease in the vital assets of the country through typhoid fever in a single year is more than $350,000,000. The house fly, as an important agent in the spread of this disease, is responsible for a very considerable portion of this decrease in vital assets. As an agency in the spread of other intestinal diseases, this sum must be greatly increased, and yet it is allowed to breed unre- stricted all over the United States; it is allowed to enter freely the houses of the great majority of our people; it is allowed to. spread bacteria freely over our food supplies in the markets and in the kitchens and dining rooms of private houses, and, to use the happy phraseology of Dr. Theobald Smith, “ when we go into public restau- rants in midsummer we are compelled to fight for our food with the myriads of house flies which we find there alert, persistent, and invincible.” Even if the typhoid or house fly were a creature difficult to de- stroy, the general failure on the part of communities to make any efforts whatever to reduce its numbers could properly be termed criminal neglect; but since, as will be shown, it is comparatively an easy matter to do away with the plague of flies, this neglect becomes an evidence of ignorance or of a carelessness in regard to disease- producing filth which to the informed mind constitutes a serious blot on civilized methods of life. THE TYPHOID FLY, OR HOUSE FLY. 31 Strange as it may seem, an exhaustive study of the conditions which produce house flies in numbers has never been made. The life history of the insect in general was, down to 1873, mentioned in only three European works and few exact facts were given. In 1873 Dr. A. S. Packard, then of Salem, Mass., studied the transformations of the insect and gave descriptions of all stages, showing that the growth of a generation from the egg state to the adult occupies from 10 to 14 days. In 1895 the writer traced the life history in question, indicating that 120 eggs are laid by a single female, and that in Washington, in midsummer, a generation is produced every 10 days. Although numerous substances were experimented with, he was able to breed the fly only in horse manure. Later investigations indicated that the fly will breed in human excrement and in other fermenting vegetable and animal material, but that the vast majority of the flies that infest dwelling houses, both in cities and on farms, come from horse manure. In 1907 careful investigations carried on in the city of Liverpool by Robert Newstead, lecturer in economic entomology and_ para- sitology in the School of Tropical Medicine of the University of Liverpool, indicated that the chief breeding places of the house fly in that city should be classified under the following heads: (1) Middensteads (places where dung is stored) containing horse manure only. (2) Middensteads containing spent hops. (3) Ash pits containing fermenting materials. He found that the dung heaps of stables containing horse manure only were the chief breeding places. Where horse and cow manures were mixed the flies bred less numerously, and in barnyards where fowls were kept and allowed freedom relatively few of the house flies were found. Only one midden containing warm spent hops was inspected, and this was found to be as badly infested as any of the stable middens. A great deal of time was given to the inspection of ash pits, and it was found that wherever fermentation had taken place and artificial heat had been thus produced, such places were infested with house-fly larvee and pupze, often to the same alarming extent as in stable manure. Such ash pits as these almost invariably contained large quantities of old bedding or straw and paper, paper mixed with human excreta, or old rags, manure from rabbit hutches, etc., or a mixture of all these. About 25 per cent of the ash pits examined were thus infested, and house flies were found breeding in smaller numbers in ash pits in which no heat had been engendered by fermentation. The house fly was also found breeding by Mr. Newstead in certain temporary breeding places, such as collections 32 LOSS THROUGH INSECTS THAT CARRY DISEASE. of fermenting vegetable refuse, accumulations of manure at the wharves, and in bedding in poultry pens. Still more recent investigations were carried on during 1908 by Prof. S. A. Forbes, State entomologist of Illinois, who has reared it in large numbers from the contents of paunches of slaughtered cattle, from refuse hog hairs, from tallow vats, from carcasses of various animals, miscellaneous garbage, and so on. All this means that if we allow the accumulation of filth we will have house flies, and if we do not allow it to accumulate we will have no house flies. With the careful collection of garbage in cans and the removal of the contents at more frequent intervals than 10 days, and with the proper regulation of abattoirs, and more particularly with the proper regulation of stables in which horses are kept, the typhoid fly will become a rare species. It will not be necessary to treat horse manure with chlorid of lime or with kerosene or with a solution of Paris green or arsenate of lead, if stable men are required to place the manure daily in a properly covered receptacle and if it is carried away once a week. The orders of the health department of the District of Columbia, published May 3, 1906, if carried out will be very effective. These orders may be briefly condensed as follows: All stalls in which animals are kept shall have the surface of the ground covered with a water-tight floor. Every person occupying a building where domestic animals are kept shall maintain, in con- nection therewith, a bin or pit for the reception of manure, and pend- ing the removal from the premises of the manure from the animal or animals shall place such manure in said bin or pit. This bin shall be so constructed as to exclude rain water, and shall in all other re- spects be water-tight, except as it may be connected with the public sewer. It shall be provided with a suitable cover and constructed so as to prevent the ingress and egress of flies. No person owning a stable shall keep any manure or permit any manure to be kept in or upon any portion of the premises other than the bin or pit de- scribed, nor shall he allow any such bin or pit to be overfilled or needlessly uncovered. Horse manure may be kept tightly rammed into well-covered barrels for the purpose of removal in such barrels. Every person keeping manure in any of the more densely populated parts of the District shall cause all such manure to be removed from the premises at least twice every week between June 1 and October 31, and at least once every week between November 1 and May 31 of the following year. No person shall remove or transport any manure over any public highway in any of the more densely populated parts of the District except in a tight vehicle, which, if not inclosed, must be effectually covered with canvas, so as to prevent the manure from being dropped. No person shall deposit manure removed from the THE TYPHOID FLY, OR HOUSE FLY. 33 bins or pits within any of the more densely populated parts of the District without a permit from the health officer. Any person violating any of these provisions shall, upon conviction thereof, be punished by a fine of not more than $40 for each offense. In addition to this excellent ordinance, others have been issued from the health department of the District of Columbia which provide against the contamination of exposed food by flies and by dust. The ordinances are excellently worded so as to cover all possible cases. They provide for the registration of all stores, markets, cafés, lunch rooms, or of any other place where food or beverage is manufactured or prepared for sale, stored for sale, offered for sale, or sold, in order to facilitate inspection, and still more recent ordinances provide for the registration of stables. An excellent campaign was begun during the summer of 1908 against insanitary lunch rooms and restaurants. A number of cases were prosecuted, but conviction was found to be difficult. For one reason or another, the chief reason being the lack of a sufficient force of inspectors under the control of the health officers, the ordinance in regard to stables has not been carried out with that perfection which the situation demands. In the summer of 1896, the health officer of the District, Dr. W. C. Woodward, designated a region in Washington bounded by Pennsylvania avenue, Sixth street, Fifteenth street, and the Potomac River, which was to be watched by assistants of the writer. Twenty-four stables were located in this region and were visited weekly by two assistants chosen for the pur- pose. The result was that on the whole the manure was well looked after and the number of flies in the region in question was very con- siderably reduced during the time of inspection. Were simple inspection of stables all that is needed, a force of four inspectors, specially detailed for this work, could cover the District of Columbia, examining every stable, after they were once located and mapped, once a week. The average salary of an inspector is $1,147, so that the total expense for the first year would be something lke $4,500. But the inspectors’ service is complicated by the matter of prosecution. Much of the time of inspectors would be. taken in the prosecution of the owners of neglected premises. Moreover, the health officer has found during the summer of 1908, in his prosecution of the owners or managers of insanitary restaurants, that his inspectors were practically sworn out of court by the multiplicity of opposing evi- dence. This means that it will be necessary in such cases to send two inspectors together in all cases, so that the testimony of one may be supported by the testimony of the other. This, perhaps, would double the number of necessary inspectors, making the expense of the service something over $9,000. It is reasonably safe to state, however, that 34 LOSS THROUGH INSECTS THAT CARRY DISEASE. with such an expense for competent service, or perhaps with a slightly added expense, the typhoid fly could be largely eliminated as an ele- ment in the transfer of disease in the District of Columbia, and the difficulty which the authorities have had in locating the cause of a very considerable proportion of the cases of typhoid in the District for the past two or three years indicates plainly to the mind of the writer that the typhoid fly is a much more important element than has been supposed. It is a comforting although comparatively insig- nificant fact and a matter of common observation that in certain sections of the city the typhoid fly has been much less numerous dur- ing the past summer than in previous years. The writer is inclined to attribute this to the gradual disappearance of horse stables in such sections, brought about by the rapidly increasing use of motor vehicles. A significant paragraph in Mr. Newstead’s Liverpool report, re- ferred to above, contains the following words: “The most strenuous efforts should be made to prevent children defecating in the courts and passages; or that the parents should be compelled to remove such matter immediately; and that defecation in stable middens should be strictly forbidden. The danger hes in the overwhelming attraction which such fecal matter has for house flies, which later may come into direct contact with man or his foodstuffs. They may, as Veeder puts it,‘ In a very few minutes * * * load themselves with dejections from a typhoid or dysenteric patient, not as yet sick enough to be in hospital or under observation, and carry the poison so taken up into the very midst of the food and water ready for use at the next meal. There is no long, roundabout process involved.’ ” The writer has already referred to this general subject in his re- marks on the depositing of excrement in the open within town or city limits, but Newstead’s specific reference to children reminds one that in the tenement districts of the older great cities of England and other parts of Europe there occur opportunities for transfer of disease which, while probably less numerous in the newer cities of the United States, nevertheless must still exist and be a constant danger. We have thus shown that the typhoid or house fly is a general and common carrier of pathogenic bacteria. It may carry typhoid fever, Asiatic cholera, dysentery, cholera morbus, and other intestinal dis- eases; it may carry the bacilli of tuberculosis and certain eye diseases; it is everywhere present, and it is disposed of with comparative ease. It is the duty of every individual to guard so far as possible against the occurrence of flies upon his premises. It is the duty of every com- munity, through its board of health, to spend money in the warfare against this enemy of mankind. This duty is as pronounced as though the community were attacked by bands of ravenous wolves. THE TYPHOID FLY, OR HOUSE FLY. oO" As a matter of fact, large sums of money are spent annually in the protection of property in the United States. Large sums of money are spent also in health matters; but the expenditure for protection from flies is very small and is misdirected. There is much justifica- tion for the following criticism published editorially in the Journal of the American Medical Association for August 22, 1908, under the caption, “ National Farm Commission and Rural Sanitation :” “The President calls attention to the fact that all efforts to aid the farmers have hitherto been directed to improving their material welfare, while the man himself and his family have been neglected. Nowhere is this more marked than in the attitude of the General Government in matters relating to sanitation. It is a trite saying that whereas the Government, through the Department of Agricul- ture, aids the farmer generously in caring for the health of his hogs, sheep, etc., it does nothing for his own health. The Government issues notices to the farmer of the injury done to his crops by the cotton-boll weevil and the potato bugs and how to combat them, but the injury the mosquito does in spreading malaria to the people who pick the cotton and hoe the potatoes is not impressed on him. The fact that horseflies may carry anthrax to his cattle is dealt with at considerable length, but the diseases which the house fly spreads to the milk and to the farmer’s family attract practically no attention. How to build a hogpen or a sanitary barn is the subject of a number of government publications, but how to build a sanitary privy which will prevent the spread of typhoid, hook worm, and many other dis- eases is regarded as of strictly local interest.” But this criticism is not entirely justified, since there was published by the Bureau of Entomology of the United States Department of Agriculture, in 1900, a Farmers’ Bulletin, entitled “How Insects Affect Health in Rural Districts,’* in which all of these points men- tioned by the editor of the Journal of the American Medical Asso- ciation have been touched upon, and at the date of present writing 192,000 copies of this bulletin have been distributed among the people. Moreover, a number of years ago a circular? was published on the subject of the house fly, calling attention to its dangers and giving instructions such as are covered in a general way in this article, and some 18,000 copies of this circular have also been dis- tributed. This is an indication that the General Government is by no means blind to the people’s needs in such matters as we have under consideration, but further work should be done. That the English Government is awaking to the same need is shown by the fact that, in the parliamentary vote of the present year in aid of *Farmers’ Bulletin No. 155. 5 Circular No. 35, Bureau of Entomology, 1891, afterwards reissued in revised form as Circular No. 71. 36 LOSS THROUGH INSECTS THAT CARRY DISEASE. scientific investigations concerning disease, one of the projects sup- ported by the General Government was the investigation of Doctors Copeman and Nuttall on flies as carriers of disease. A leading editorial in an afternoon paper of the city of Washing- ton, of October 20, 1908, bears the heading, “ Typhoid a National Scourge,” arguing that it is to-day as great a scourge as tuberculosis. The editorial writer might equally well have used the heading “ Ty- phoid a National Reproach,” or perhaps even “ Typhoid a National Crime,” since it is an absolutely preventable disease. And as for the typhoid fly, that a creature born in indescribable filth and absolutely swarming with disease germs should practically be invited to mul- tiply unchecked, even in great centers of population, is surely nothing less than criminal. ENDEMIC DISEASE AS AFFECTING THE PROGRESS OF NATIONS. In referring to the spread of malaria in Greece, the relation of this disease to the rise and fall of national power has been touched upon in an earlier paragraph of this bulletin (p. 9). The subject is one of the widest importance and deserves a more extended consideration. The following paragraphs are quoted from Ronald Ross’s address on Malaria in Greece, delivered before the Oxford Medical Society, November 29, 1906: “ Now, what must be the effect of this ubiquitous and everlasting incubus of disease on the people of modern Greece? Remember that the malady is essentially one of infancy among the native population. Infecting the child one or two years after birth, it persecutes him until puberty with a long succession of febrile attacks, accompanied by much splenomegaly and anemia. Imagine the effect it would produce upon our own children here in Britain. It is true that our children suffer from many complaints—scarlatina, measles, whoop- ing cough—but these are of brief duration and transient. But now add to these, in imagination, a malady which lasts for years, and may sometimes attack every child in a village. What would be the effect upon our population—especially our rural population—upon their numbers and upon the health and vigour of the survivors? It must be enormous in Greece. People often seem to think that such a plague strengthens a race by killing off the weaker individuals; but this view rests upon the unproven assumption that it is really the weaker children which can not survive. On the contrary, experience seems to show that it is the stronger blood which suffers most—the fair, northern blood which nature attempts constantly to pour into the southern lands. If this be true, the effect of malaria will be constantly to resist the invigorating influx which nature has provided ; and there are many facts in the history of India, Italy, and Africa which could be brought forward in support of this hypothesis. ENDEMIC DISEASE AFFECTING PROGRESS OF NATIONS. 37 “We now come face to face with that profoundly interesting subject, the political, economical, and historical significance of this great disease. We know that malaria must have existed in Greece ever since the time of Hippocrates, about 400 B. C. What effect has it had on the life of the country? In prehistoric times Greece was certainly peopled by successive waves of Aryan invaders from the north—probably a fair-haired people—who made it what it became, who conquered Persia and Egypt, and who created the sciences, arts, and philosophies which we are only developing further to- day. That race reached its climax of development at the time of Pericles. Those great and beautiful valleys were thickly peopled by a civilization which in some ways has not been excelled. Everywhere there were cities, temples, oracles, arts, philosophies, and a population vigorous and well trained in arms. Lake Kopais, now almost deserted, was surrounded by towns whose massive works remain to this day. Suddenly, however, a blight fell over all. Was it due to internecine conflict or to foreign conquest? Scarcely; for history shows that war burns and ravages, but does not annihilate. Thebes was thrice destroyed, but thrice rebuilt. Or was it due to some cause, entering furtively and gradually sapping away the energies of the race by attacking the rural population, by slaying the new-born infant, by seizing the rising generation, and especially by killing out the fair- fe descendant of the original settlers, leaving behind chiefly the more immunised and darker children of their captives, won by the sword from Asia and Africa? * * * “T can not imagine Lake Kopais, in its present highly malarious condition, to have been thickly peopled by a vigorous race; nor, on looking at those wonderful figured tombstones at Athens, can I ‘imagine that the healthy and powerful people represented upon them could have ever passed through the anemic and splenomegalous infancy (to coin a word) caused by widespread malaria. Well, I venture only to suggest the hypothesis, and must leave it to scholars for confirmation or rejection. Of one thing I am confident, that ‘auses such as malaria, dysentery, and intestinal entozoa must have modified history to a much greater extent than we conceive. Our historians and economists do not seem even to have considered the matter. It is true that they speak of epidemic diseases, but the endemic diseases are really those of the greatest importance. The “The whole life of Greece must suffer from this weight, which crushes its rural energies. Where the children suffer so much, how can the country create that fresh blood which keeps a nation young? But for a hamlet here and there, those famous valleys are deserted. I saw from a spur of Helikon the sun setting upon Parnassus, Apollo sinking, as he was wont to do, towards his own fane at Delphi, and pouring a flood of light over the great Kopaik Plain. But it seemed 38 LOSS THROUGH INSECTS THAT CARRY DISEASE. that he was the only inhabitant of it. There was nothing there. ‘Who,’ said a rich Greek to me, ‘would think of going to live in such a place as that?’ I doubt much whether it is the Turk who has done all this. I think it is very largely the malaria.” In considering carefully this suggestive argument of Major Ross does it not appear to indicate the tremendous influence that the prevalence of endemic disease must exert upon the progress of mod- ern nations, and does it not bring the thought that those nations that: are most advanced in sanitary science and preventive medicine will, other things being equal, assume the lead in the world’s work? Who van estimate the influence of the sanitary laws of the Hebrew scrip- tures upon the extraordinary persistence of that race through cen- turies of European oppression—centuries full of plague years and of terrible mortality from preventable disease? And what more striking example can be advanced of the effect of an enlightened and scientitically careful attention to the most recent advances of preventive medicine upon the progress of nations than the mortality statistics of the Japanese armies in the recent Russo-Japanese war as compared with the corresponding statistics for the British army during the Boer war immediately preceding, or for the American Army during the Spanish war at a somewhat earlier date? The consideration of these elements of national progress has been neglected by historians, but they are nevertheless of deep-reaching importance and must attract immediate attention in this age of advanced civilization. The world has entered the historical age when national greatness and national decay will be based on physical rather than moral conditions, and it is vitally incumbent upon na- tions to use every possible effort and every possible means to check physical deterioration. EN Die Page. APAGLOMms sresilavione to avoid house flies: ee ee a 32 Anopheles mosquitoes (see also Mosquitoes, malaria). CUSSEmMinatons: Of ma laisse ee ia Suppression: inanimate 22 Ash pits containing fermenting material, breeding places of house fly____ dl Bacilli, typhoid, longevity in milk, cream, butter, and cheese___________ PA - Bacillus icteroides, not proven to be causative germ of yellow fever_____ 19 EAClebiAmnroOmp ties MCCNSUS. 8:72 2c As eae ee ree St 29-30 YD TIA UU oo SOIT COS Lancs oe Th AS Ee ae eee eee Re I, 28-30 eRe AmGCAbhiCrnOtuGisea ses 220 Ves 22 eee ee ee Se ee 7 Bedding, old, in ash pits, breeding place of house fly____________________ 3 BUvoOMesplasie: conveyance. by fleas = ssa ee ee ee a Caresmreculationeto: avoid house fliesos2. 2... see eee 33 Careasses of animals, breeding places of house fly_.____________________ 32 ChioleraeAsiahic. carriage. Dy house fly. 2s Sse ee 1, 20, 34 HUE AHS Chupakixen| one MUR hye eee A ee Le 29 MGLDUS TGArTIAge “Dy, HOUSE dy ..5o22 = See ee ee ee eee 34 COUECTMUSCLALUS—SLEGOMIYIG! CALOPUS. 2 == eee 19 MeTIiSsiEroOMamMalariay inv United Statest2. 2222 2 a ea eee 9-10 typhoid fever in concentration camps, U. S. Army_________ 24-25 Vvellowsreveryin Uniteds States 222. aoe a 22 eee ee Swe! Disease, endemic, as affecting progress of nations_______________________ 36-38 Diseases, intestinal, dissemination by house fly_________________________ ie DySenieny.sumMmmMmer/-carriage by, housefly. 9 2) ee eee 27, 34 tropical wcarrince by, NOuUse lye =o es yee eee eee 27, 34 Hndemie disease as affecting progress of nations_______________________ 36-38 lxcrement, human, breeding place of house fly_________________________ 31 HyVexGiseasess carriages py house My2e= =) 22s e = ee ee eee od Fermenting animal and vegetable material, breeding places of house fly__ 31-82 HiUlaALiasis, transmission pyoapmMOosqultoh= == === 22s ee ee ee ee 7 Mieas conveyors) Of Dubonie=plasues {9 ae hee ae we ee te eee 7 Hes pine Carriers Of sleeping. SICKNESS 2 == =. = De eee Te i LEN Ges EKO Sebo | oy rere theta a) Fee syS Pei ae ee a ee ee 31-32 qisseminatorohcholera. -Astatic= as. 3s se ese ee Ti Pals Be TAM GU sees Le Pee eee aes 29 TOC | 0) DS as al ee a ee 34 GYSEMCET Year SUNN re he be 27, 34 CrOpLCAl Dae Ae wGy 9s Sah a) Pil CY CROISCASCS pistes Eee) ee ee ee 34 ANTES TMA CISCASESE Ms = he Sees ea es es 7, 27-28 purulent opithalmiae sw eS eee eae i bypHOIGS fever < se es keel eae ee eee So 1G GUD ETRCUULO SIS pt sees ne ed 7, 28, 34 NCES AVY a Vp Se i eg NIE Ue Se ee 2-36 RMR INTS EO Te yee eee hs eee a oe See Pee IES ee ee 3 LelatLOncOmby MNO he verses es ee a eRe ed ee 282 suppression feasible and all-important ________________-___ 30 MAME Name One NOUNCe tl ya ae ae eee ee a 23 CVO Eh aIMe AORN OUSCRIhy= ==e enue ae At alse ae 23 Gira ew ireccinewplaCenOle ll OUSE mflyse™ sae ee eee Be a ee 32 COMECCHONECOCAVOlOgn OUSEsi eS a eure ei sy) D1 a ee 32 Np Pelates Mies SCarriersuah pinke ey eee === es bees ee ee t Mo hairs; refuse, breedine place of house fly +--+ ---=---------2== 32 MEO VSs spenis sbreedinesplacelor house mly2=22— st 31 Insects affecting health, publications by Bureau of Entomology_-—— ~~~ 35 Pincherooms. resulations to avoid house flres= 22 1.225522) eee oe ia iMG etch S aii UIMLCGIaNtategme see Win: t= Fo eta bee ee ee 9-10 Gissenunationieby. mosquitoes" o St es ee ee tT, 8-17 Cradicationsat ismailian suez, Canalo. = =-2 3 eee 16-17 TNC MECC Ommnnee neater sn ees Sa 2 ee ee ee ee ee 36-38 ee Be Pe ae 4 , ¥ Nei ride Wt i Mas! a 40 LOSS THROUGH INSECTS THAT CARRY DISEASE. Page. Malaria, in’ Italy, Joss therefrom22- <2 =22 42323 eee 11-12 Mauritiuss0 226 2h ee ES ee ee Li Reunion 2s ot A ae eee a ee eee 119 United States, history) 22s 22223 ee loss in Wnited (Statess222542 22 hse ee ee ee 9-14 Ttaliy oe See eS a ee 11-12 mosquitoes. (See Anopheles mosquitoes and Mosquito, malaria.) prevention. <2 2 S28 58 et oe ee 14.17 relation to agriculture and other industries of the South_____ __ 18-14 SUPPRESSION dn HAVaNa, 202 bot Tee ee eee Rana a) 322 22 oe Se ee eee 21-23 Selangor, Federated Malay States__-_---_----_ 15-16 Manure; disposal, tolavoid house tliless= == =e ee 32-33 Markets, regulation, to avoid house flies Milk ‘sourcesiiof bacteria: therein]. 2222) 2 eee 28-30 Mosquito; disseminator of filaridsiS ==") eee jnavlamial Le se ee ee yellow, feveri24 8 Se eee malaria (see also Anopheles mosquitoes). Suppression medsires= 2 ee ee ee 15-17 yellow fever, Suppression measures .2. 22 ee eee 19-28 Mosquitoes, losses in general which they oceasion_________-_--_____----~~ through malaria -which they oceasion__.______________ 8-17 yellow fever which they occasion____________ 17-21 Suppression in) Panama 4252 ee ee ee ee 21-23 Nations, endemic disease as affecting progress_______________-=________= 36-88 Ophthalmia. purulent, carriage by housemly 22222 oe ee eee fs Paper, old, breeding placevot housegilve= 3-3-2 3. eee 31 pink eye, carriage by Euppelatesiites®-- 22228) eee 7 Plague, bubonic. (See Bubonic plague.) Poultry-house bedding, breeding place of house fly______________________ 32 Progress of nations as affected by endemic disease___-_______________-~~ 36-88 Rags, old, in ash pits, breeding place ofvhouseily____ -_ = ee 31 Restaurants, reculation:, to avoid) house flies= eee 33 Sanitation, rural, necessity for government: support____________________ 35 Slaughtered cattle paunches, breeding places of house fly_-____________ 32 Sleeping sickness; carriage by bitingwilies® =) ee T co Spotted! fever,” carriage by ticki 2st 2) ee eee eee fe Stable inspection against house flies, probable cost__________________-____ 33-34 Staples; sreculation, to avoid howseghies 2222 222 eee 32—30 Stegomyia calopus (see also Mosquito, yellow fever). disseminator of yellow +fever________=______ "32 = 7, 19, 20 Stures, reculation, to avoid Nhousemties: = §) se ee eee 33 Straw, old) in ash pits, breedingaplace;ofshousesfily_=—--=_--_-__=* ==2e ees fol Mallowavats,, breeding. places of housesly-22- 2 eee 82 highs. carrier of “spotted fever’ _.--2 2 es) 1 oe eee Ti thiberculosis; dissemination by, house fly22=- 2-2 = eee eee 7, 28, 34 My phoid, fevers a) aeNational Reproach?=__=-) 22.2) ee ee 36 dissemination by house. dye 22a ee a ee 7, 23-27, 34 in .concentrationsecamps,; U.4S.cAnmy= ee eee 24-25 loss). ins WnitedStates<.—_ <4 oc» DE ee ee eee 30 Vegetable refuse, fermenting, breeding place of house fly__.__.__-_______ 32 Mellow.dtever,, cause, history.otinvestigaiens 22> eee eee 19 deaths cinwNewa@ cleans << 55 = se ee eee ee Pal Wnited= States. oy See ee 18 dissemination by.mosqwito- 22 Weeks eee eee € history.dm Americas = So 2o2 SE UE ee ee 17-18 leSstinwiinited Slates. 2 bls ee eee 18 mosquito. (See Mosquito, yellow fever.) suppression in Havana and New Orleans________________ 19-21 PPT Au os ss hs Sk nee 21-23 ‘ aR my “mae, y e cf os -_ U.S. DEPARTMENT OF AGRICULTURE, BUREAU OF ENTOMOLOGY BULLETIN No. 79. ia : ae L. O. HOWARD, Entomologist and Chief of Bureau -FUMIGATION INVESTIGATIONS ' __IN CALIFORNIA. By R. Ss. WOGLUM, Special Field Agent. [CHEMICAL WORK PERFORMED BY THE MISCELLANEOUS DIVISION OF THE BUREAU OF CHEMISTRY.|] Issurp JuNE 11, 1909. ipa ‘4 = WASHINGTON: % ; GOVERNMENT PRINTING OFFICE. 1909. DP dr ORS yap ot Bo Se ARS Shoo e eee BUREAU OF ENTOMOLOGY. L. O. Howarp, Entomologist and Chief of Bureau. C. L. Maruarr, Entomologist and Acting Chief in Absence of Chief. R. 8S. Currron, Executive Assistant. . mi C. J. Ginurss, Chief Clerk. . Hopxins, in charge of forest insect investigations. . Hunter, in charge of southern field crop insect and tick investigations. . WEBSTER, 7 charge of cereal and forage plant insect investigations. . QUAINTANCE, tn charge of deciduous fruit insect investigations. . Paiuies, in charge of apiculture. . Rogers, in charge of gipsy moth and brown-tail moth field work. . Morritt, in charge of white fly investigations. . Fiske, in charge of gipsy moth laboratory. . BrsHorp, in charge of cattle tick life history investigations. . Moraan, in charge of tobacco insect investigations. . WoaLuM, in charge of hydrocyanic acid gas investigations. . CURRIE, in charge of editorial work. BEL CoLcorD, librarian. 3 . CHITTENDEN, in charge of truck crop and stored product insect investigations. y te U.S. DEPARTMENT OF AGRICULTURE, BUREAU OF ENTOMOLOGY— BULLETIN No. 79. L. O. HOWARD, Entomologist and Chief of Bureau. FUMIGATION INVESTIGATIONS IN CALIFORNIA. By Fi.( So Wa@ Grin: Special Field Agent. [CHEMICAL WORK PERFORMED BY THE MISCELLANEOUS DIVISION OF THE BUREAU OF CHEMISTRY.] Issuep JUNE 11, 1909. WASHINGTON: GOVERNMENT PRINTING OFFICE. EOOS. LETTER OF TRANSMITTAL. U.S. DEPARTMENT OF AGRICULTURE, BurkEAv OF ENTOMOLOGY, Washington, D. C., February 6, 1909. Srr: I have the honor to transmit herewith a manuscript entitled ‘‘Fumigation Investigations in California.’ It is a preliminary report on the subject, and contains much information which will be of direct practical value to citrus growers. The report is one of progress, and much of the information has already been made available to the public by means of lectures and field demonstrations, but it is important | that it should be put in published form so as to give it wider cur- rency. The subject is one that requires abundant illustration, and the figures and plates submitted are all deemed necessary for the full understanding of the text. Respectfully, L. O. Howarp, Entomologist and Chief of Bureau. Hon. JAMES WILSON, Secretary of Agriculture. bo PRIERA CRs Fumigation under tents with hydrocyanic-acid gas has been the principal means of controlling scale-insects on citrus fruit trees in California for many years. Most of the commercial orchards in the State are fumigated at intervals of one or two years, at a cost rang- ing from 25 cents to $1.50 a tree, or a probable total annual expendi- ture of about $1,500,000, on the basis of fumigation of 50 per cent of the trees each year. It becomes, therefore, a matter of very great importance to conduct the operation of fumigation in the most effect- ive and economical manner. The work being done on the subject in California by this Bureau is aimed to thoroughly standardize the proc- ess. It was undertaken in response to urgent demands from the hor- ticultural commissioners of the principal citrus-fruit-producing coun- ties of California, and of many prominent growers. The need of this investigation was most urgently championed by Mr. J. W. Jeffrey, for- mer secretary of the Los Angeles County horticultural commission and now State commissioner of horticulture of California. Recognizing the general usefulness of the process of fumigation, Mr. Jeffrey called attention strongly to the unevenness of results in the work of differ- ent manipulators and against different scale pests, and that the whole practice had grown up experimentally without ever having been given thorough scientific examination. He urged that such an examina- tion necessitated carefully conducted and recorded field work, sup- plemented by chemical tests of ingredients and the determination of reactions, and expert study of the physiological effect of the gas on the trees and fruit; in other words, to remove the process from the mere guesswork of the field man and to place it on an exact scientific basis. This investigation has been under the direct charge of the writer, who made a personal study of the situation in southern California in September and October, 1907, and planned the work to cover the fol- lowing subjects: (1) Dosage, or the amount of gas and duration of exposure neces- sary for different purposes. The strength of gas necessary to effect- ively control the three prominent scale pests of citrus trees in Cali- fornia, namely, the red scale, the purple scale, and the black scale, under different climatic conditions, as in the drier foothills regions and 3 4 FUMIGATION INVESTIGATIONS IN CALIFORNIA. the moister coastal strip; for different seasons of the year; and for the different growing conditions of the tree, as whether in fresh leafage, or in bloom, or with different stages of the developing fruit. (2) Physiological effect on the tree and fruit. There is some eyi- dence to show that the gas may have a stimulating effect on the tree. (3) Mechanical equipment. An important economical considera- tion in gassing is the employment of the most suitable tent cloths, and their treatment to give durability and imperviousness; also, the best mechanical means of hoisting tents over the trees. To be determined under this heading also are the most economical methods of generating the gas, and an indication of the quality of chemicals best suited for the purpose. In connection with this experimental work the scale species them- selves are being given a careful study in the field to determine their exact life history as a basis for the intelligent application of the remedy. This investigation was started in July, 1907, under the field charge of Mr. R. S. Woglum, who first made himself thoroughly familiar with the problem by a personal examination of conditions throughout the citrus-growing regions of southern California. The direct work of investigation began as soon as the fumigation season opened, and later Mr. Frederick Maskew was employed to assist in the work. The experimental work as planned has been conducted on a commercial scale, so that the conditions and results will be those normal to the ordinary care of citrus groves. To carry out all the lines of experi- ment indicated above, and the subsidiary ones which have developed in the course of the investigation, takes a good deal of time, and will probably occupy two or three years with the money and force now available. Nevertheless, very considerable progress has been made, and the preliminary report herewith submitted covers the general features of fumigation procedure. Improved methods have been devised, and these are being very rapidly adopted throughout southern California. These improved methods make it possible to do much more uniform work and greatly simplify the method of estimating the proper dosage. Full advantage has been taken of the fumigation work conducted in Florida against the white fly under the field direction of Dr. A. W. Morrill, and the Morrill system of marking tents for the ready determination of dosage has been introduced, with modifications, into California. C. L. Maruart, Entomologist and Acting Chief of Bureau in Absence of Chief. COT ENGELS. Page Bins ome OM ey) ete ia et info Eee means oe ete nid vw a ln 9 BPGre Hinwtredes OLE MOTOS. eter Ges ee ae lak bees sO SoS ie ee 10 sp DIPOLE SOE SES Se, Ea SOR PRR ca SES A Ena a ea SR ee SO 10 Insect enemies of citrus fruits, and their distribution. ..................-. 10 Injury resulting’ to seale-infested trees... 0. 2 4... 4.2.22. ce eee ele 14 Method of propagation of the more injurious scale pests ...............-. 16 Methods used in the control of scale pests of citrus trees... ...........--- 16 [SATE SSE NTIS, 3 ier al Spe a eee Re ahh) a Te ce a a 17 SUG SU SITS PRS RNS OA ee gee NE PRR Oe ee TO 17 seid eOMN EO CROURGr eect ee ace ate cise ales ena. oa eis shew ean. 18 Dosage schedules of the more important writers on fumigation............ 19 The present system of scheduling dosage. ....................2.22------ 23 The initial problem confronting this investigation.......................- 24 Method of computing volume and dosage for tented trees. .............-. 25 Methods for obtaining the measurements and dosage of trees...........--- 26 ie chemicals required im-fumipation «. o.../.< 25-20-24 s cade qe ne ceihccine ects 30 EO ORT TMM ATA Se Lot eects ae He at de lychee) .n ns pact chalet oreo 2A 30 SHEUTO) TSE ESTE: 1G SRA EP aan ONS Ce et ONE Ae AS ATG ee A En 30 Proportion of chemicals used by fumigators....................---2-,---- 32 ihe amount of sulphuric’acid necessary..:-. 2.2 ...20..5.¢...00e.-82- 32 The. ettect/ol too great.an excess’of acid... . 60.0. /eae chee ees noee 34 Waters ariactor am fumigation. 202.2220: 20 seernnes vive «ci 34 The effect of different proportions of water on the apemume On the BS Gt Ge Se Para aS GOS O SS OOO Oe SOE ee Ee Ee Te aah sae 30 The temperature of the gas where large and small dosages are used... - 36 The effect of different proportions of water on the amount of available I CECRE NENG -ACLOVORS apie Sais or Seer ea Ca le 37 Thercorrect; proportion of water... 0.2.5.2 2 sek oetee cece nse Jeter he 38 The most economical proportion of chemicals to use in generating lined Roe etn Iicee C1 UPAS ek ce eens s 2 oN hye, SL en sk 39 iM BLS EWg RP (GL AVES CEL NSS 1a CET ESD PR rer ag An ee a 39 Fae plle seaten (MPA MOREnet fas cece cas Deine oie. ee/e es le ee eent ow e- : 40 Preliminary experiments for the control of the purple scale.............-. 40 The leakage of gas in fumigating small trees. . .........2..2.......-.-.-. 43 See Meath et TO ONTING Sete en Pe en nk oR bee tie dia es 5k 4 Mradication oftnerpurple scales bes.) Se. ese Sa ee 46 Diticulty of destroyine the seale on the fruit. 2. 2..2.2..-.....-.-.2626% 46 Beate recomend ions mer mm remnmer ere Gee a 47 Reticame Omeas MumnorOnera tienes soe ee I Soe we wks a weeks 47 Mimicienthe year tortunmention.. 8) 8s o.oo ee eke £2 ot 48 Fumigation during the blossoming period. .................-.------ 49 Fumigation while the fruit isiof small size...................-s00--0- 51 6 CONTENTS. General considerations—Continued. Simple method of removing acid from drums and carboys. - ..-.--------- lhe. protection of cyamidss. 221.22 fees 3 se eo eee ee ee Hydrocyanic-acid’gas am drumss 2.22 Ses ye eee ee ee eee The marking of tents* Yes ee see eee eee eee a eee eee Wdevaice for covermetumicatiomysenera tons: a aa eee An Improved system of fami gations. cas aces py sees eee se ee Supply carte 22% sibs Se ee ie ee es oe eer ge aor ee Procedures pyro aa Ss eer tes ete ree ee ae ae ree ce Advantages“under {his system! _ 252.350 se wes Siete ee ee Dosage schedules Co. cose ses ee che. k Set ae a Neen = Pies ee The improved :system-im Usess24.2 0528 sees se ee ik SER eae Fuinigationysim plified ete cio Sine, roe Satta epee nee Tride@xs. S25 dees, Seiten is = aise eae ere Se ee ae eager Oe eee bo ra PED Esk tLONS:. . Map showing principal localities in southern California where citrus THURLES) BA B9 OT a 9 AE Crey 6 ekg eager 2 ee Se ee . Leaves and branch of orange infested with purple scale (Lepidosaphes ‘hash eae pe ae On Pn a . Fruit of orange infested with purple scale.......2..............----- . Branches of orange infested with black scale (Saissetia olex) ......... . Leaves and branch of orange infested with red scale (Chrysomphalus (PT PTA eke ES Sy ea et AD ee | eS si A Sea SS oe a a . Orange tree almost destroyed by red scale......................----- . Orange tree showing branches at center partly destroyed and stripped Ginter vecibyapurple Bealess see as Ne ee eis het . Tray commonly used for carrying the chemicals of fumigation from UITEXES TO) WUE ss Se te pe AS Re Oe Oe ee ees ae CE BOE pee mam Nate Pree PMan carnyine tray. and water bucket... . 2-6-2474 -< 25.2 eee woe onn . A typical California lemon orchard with row of fumigation generators placed ready for use the following night....................--.--. . Outline of a fumigation tent marked according to the Morrill system. 2. A fumigation tent marked after the Morrill system...............-. . Chart showing total amount of gas evolved when different propor- HHOMEKOMRW ALE LIAN OaUINe Gla. clave eo ot ne nS Ba ae Rall va . Orange blossoms at an early stage of development..........-.--.---- . Lead-lined tank used in San Bernardino County for removing sul- phuric:acid: fromdrums;and for filling jugs .......02 2.2... 22.22.2240 . An improved pipe for removing acid from drums..............---.-- . Siphoning acid from a drum by means of a rubber hose.....-...--.--- . Carboy resting against a heap of dirt to facilitate pouring the acid... . . Carboy with handles attached to facilitate pouring the acid and carry- AMELIE CAND OMS ceo) ast =e er ttafore cco ahsietare tac kin 8S es Sac isla pale . Zinc-covered top for protecting cyanid in the field...-.............- . A cover device attached to a fumigation generator. -.............--- . Difference in the direction taken by gas escaping from an open gen- erator and from one covered with the corrugated lid..........-..--- . Cart used with the improved system of fumigation...............-.. . Harthenware acid jar with attachments for field use.........----.-.:-- . A table which can be used instead of a cart in fumigation over very TROMUEE| Perera WICC ISS Sep eee Ne On ee ee . A row of tented trees, and cart at one end ready for dosing.........- EN] DIGSHTa i Niger ee SAN ee Ee Ose Be ROr Spe ee ie eee Beem csa So SENeO Ml On N OMe sere ee eae kee a o/c coc de cna e's cles ss Se aiee Page. FUMIGATION INVESTIGATIONS IN CALIFORNIA. INTRODUCTION. Early in July, 1907, the writer received a commission to investi- gate the use of hydrocyanic-acid gas in the control of insect pests of citrus trees in southern California. Acting under detailed instruc- tions from Mr. C. L. Marlatt, the Assistant Chief of the Bureau of Entomology of the United States Department of Agriculture, he spent the latter part of July and the following three months in a thorough field investigation to acquaint himself with the condi- tions of citrus culture throughout southern California, the distribu- tion of the different citrus pests and the damage caused by them, the existing methods for their control, and the status of fumigation as then practiced in the various citrus districts. During this period all the important citrus-producing sections south of Santa Barbara were visited, and local conditions were carefully examined. This work was greatly facilitated by the hearty cooperation of the differ- ent county horticultural commissioners, who gave their time freely and greatly assisted the writer in becoming familiar with all the features of the problem in their respective counties. The writer desires to acknowledge his indebtedness to the many people who have assisted him during this investigation and facilitated the progress which has been made. To Mr. C. L. Marlatt, Assistant Chief of the Bureau of Entomology, he is especially indebted for valuable assistance and advice. It is also the writer’s great pleasure to acknowledge his appreciation of the work of Mr. Frederick Maskew, who has most capably assisted him in the performance of many of his experiments. Mr. Maskew also prepared several of the illus- trations used. To the Hon. J. W. Jeffrey, State commissioner of hor- ticulture of California, credit is due not only for his activity in paving the way for this investigation but also for the able support given since field work was commenced. To Mr. William Wood, of Whittier, Cal., the writer acknowledges his indebtedness for assistance in intro- ducing the improved system of fumigation in the region adjacent to Whittier, as well as for practical advice with regard to citrus insects and their control, a subject about which he is especially well informed. This occasion is also taken to thank the various horticultural officers of southern California, packing-house managers, and the many citrus growers who have assisted and supported this investigation. 9 10 FUMIGATION INVESTIGATIONS IN CALIFORNIA. EXTENT OF CITRUS ORCHARDS.«4 The production of citrus fruits in southern California is confined to the narrow stretch of land south and west of the Sierra Madre Range, extending from Santa Barbara on the north to the Mexican border. Although citrus plantings are located here and there through- out this territory, in reality only a small proportion of the land capable of cultivation is devoted to this industry. The most promi- nent centers of production (see fig. 1) are in the foothills region and lower land of the San Gabriel Valley; the corresponding regions of the San Bernardino Valley, including the Redlands-Highland, the Riverside, and the Corona districts; and the coast region of Orange SAN BERNARDINO g Qsge ow B SESE , & Pa0e 8 neo gn 8 OOO Son ie) gall ot 0 REDLANDS of 5 200 a O ORIVERSIDE S ° ‘Ko CARLINGTON #7) Onan, RIVERSIDE O£SCONDIDG™ SAN DIEGO OLANE SIDE O£L CAON ee a Fic. 1.—Map showing principai localities in southern California where citrus fruits are produced. (Original. ) and Los Angeles counties. Regions of smaller production are found in southern Santa Barbara and Ventura counties, in the San Fer- nando Valley, and in western San Diego County. CITRUS PESTS. INSECT ENEMIES OF CITRUS FRUITS, AND THEIR DISTRIBUTION. The larger number of the pests most injurious to citrus fruits in southern California belong to the Coccide, a group of insects popu- larly known as scale-insects. Among the scale-insects which are a For a general description of the California citrus-fruit industry, see Bulletin 123, Bureau of Plant Industry, United States Department of Agriculture, which may be obtained for 20 cents from the Superintendent of Documents, Government Printing Office, Washington, D. C. INSECT ENEMIES OF CITRUS FRUITS. Hig generally so destructive as to require extended efforts for their control are the purple scale (Lepidosaphes beckii Newm.), the red scale (Chrysomphalus aurantit Mask.), and the black scale (Saissetia olee Bern.). The yellow scale (Chrysomphalus citrinus Coq.), con- sidered a variety of the red scale, is much less destructive generally, though sufficiently troublesome in some localities to be considered a pest of primary importance. Other scale-insects attacking citrus trees, which are so perfectly held in control by their natural enemies and other causes as seldom to become very destructive, are the soft brown scale ( Coccus hesperidum L.), the hemispherical scale (Saissetia hemispherica Targ.), the oleander scale (Aspidiotus hedere Val.), Fic. 2.—Leaves and branch of orange infested with purple scale (Lepidosaphes beckii). (Original.) and the cottony cushion scale (Jcerya purchasi Mask.). Mealy bugs (Pseudococcus spp.) are quite generally prevalent. The most important pests other than scale-insects are to be found among the mites, of which the rust mite of the orange or silver mite of the lemon (Phyllocoptes oleivorus Ashm.) and the citrus red spider ( Tetranychus mytilaspidis Riley) are highly injurious. The orange aphis (Aphis gossypii Glov.) becomes very numerous during some seasons but is soon attacked by its natural enemies and held in con- trol. A species of thrips worked quite extensively in some localities on ripe oranges during the first months of 1908, removing the coloring matter from beneath the epidermis, thus giving to the fruit a spotted appearance which lowered its market grade. The purple scale (figs. 2 and 3) appears to prefer the more moist regions in the vicinity of the ocean. It is found in Santa Barbara r2 FUMIGATION INVESTIGATIONS IN CALIFORNIA. and Ventura counties; in Los Angeles County, inward from the coast as far as Hollywood and Whittier, and in the lower part of the San Gabriel Valley at Covina and Duarte; throughout Orange County; and in San Diego County in the region about San Diego city. Thisinsect confines its attack to citrus trees. The black scale (fig. 4) is also considered as partial to the more moist regions, and with- out doubt is able to mature more freely here than in the hot interior country. It is distributed, however, throughout the citrus-growing localities with the exception of the Rialto-Highland-Redlands region of San Bernardino County. At Redlands this scale is found on olives and some ornamental plants; yet, to the best of the writer’s knowl- edge, it has not been reported from citrus orchards. Even as far inland as Ontario and Riverside the black scale is) capable of breeding freely during some parts of the year, but the hot days of summer destroy a large percentage of the eggs and_ especially those young scales which are exposed to the sun’s rays. This destruction was espe- cially noticeable in the summer season of Fic. 4.—Branches of orange infested with black scale (Saissetia olex). (Original.) Fic. 3.—Fruit of orange infested with purple scale. (Original.) 1907, when the writer was engaged in an examination of different localities. During the first part of July occurred a few days of very hot weather. About INSECT ENEMIES OF CITRUS FRUITS. 13 a month later inspections were made throughout the lower San Gabriel Valley, at Pomona, Ontario, and Riverside, and in Orange County. Throughout this valley a large majority of the young insects which had hatched were dead at this time while fully 50 per cent of the eggs had dried up. At Pomona, Ontario, and Riverside almost all the young insects had been destroyed, and fully 90 per cent of the eggs beneath the old scales. In Orange County near the coast a very small per- centage of eggs was affected by this hot period, while recently hatched young scales were much in evidence. The black scale occurs cn a wide range of hosts, including trees, shrubs, and herbaceous plants. The red scale (fig. 5) thrives exceedingly well in the drier interior regions of southern California. It can be found within a few miles Fic. 5.—Leaves and branch of orange infested with red scale (Chrysomphalus auranti7). (Orisinal.) of the ocean or as far inland as Redlands. The limits cf its distri- bution are much the same as for the black scale. This species can be found on several host plants other than citrus species. The yellow scale is even more of a heat-withstanding form than the red scale. Infestation by this insect appears to be most marked in the foothills region of the San Gabriel Valley, and along the Sierra Madre Range through Upland and Cucamonga. It is also broadly dis- tributed at Redlands, where it has become a more serious menace than elsewhere in southern California. ‘That it is capable of withstanding excessive heat is demonstrated by its prevalence in citrus orchards in the San Joaquin Valley, at Marysville, Oroville, and other parts of the hot interior valleys of northern California, where the purple scale and to a large extent the black scale appear unable to survive. 14 FUMIGATION INVESTIGATIONS IN CALIFORNIA, Mealy bugs occur in various parts of the southern end of the State. Their appearance is usually spasmodic and in restricted areas. These insects are at present more serious than elsewhere in Ventura County, where they occur in great numbers. The citrus red spider is general in distribution, whereas the silver mite is restricted to the region about the city of San Diego. INJURY RESULTING TO SCALE-INFESTED TREES. In scale insects the mouth is an elongated beak or tube. This tube is inserted into the bark or covering of the host plant when the insect is feeding, and is used to draw up the plant juices, which are the scale- insect’s only food. When great num- bers of these insects draw sap from the tree, even though they are very mi- nute, the tree’s vitality is greatly reduced. This ef- fect is very marked in the attacks of the red and purple scales. Both of these species cause much destruction, yet the writer is of the opinion that the red scale will de- stroy a citrus tree in less time than will the purple scale, all other fac- tors being equal. Trees have been noticed from two to three years after planting which had been killed by the red scale. Large orchard trees are frequently destroyed by the pest (fig. 6), while it is a very common sight in regions of severe infestation to see large branches killed back to the trunk. Although no trees have ever come to the writer’s attention which were completely killed by the purple scale, severe infestations result in the destruction of many branches (fig. 7), and cause such a drain on the tree that the produc- tion of fruit is greatly decreased. Moreover, the purple scale spreads Fic. 6.—Orange tree almost destroyed by red scale. (Original.) INJURY RESULTING TO SCALE-INFESTED TREES. 15 to the fruit, as does also the red scale, resulting in expense for the cleaning of fruit or rendering it of a lower grade and, in extreme cases, entirely valueless. The black scale, although a much larger insect than either the red scale or purple scale, appears to have, generally, little effect on the vitality of the tree. Trees severely infested with the black scale may appear as healthy as neighboring trees which are clean. Branches are seldom if ever destroyed by its attacks alone. The commercial importance of the black scale arises largely from its habit of secreting honeydew, which spreads over the leaves, fruit, Fic. 7.—Orange tree showing branches at center partly destroyed and stripped of leaves by purple scale (Lepidosaphes beckii). (Original.) and branches, furnishing a growing medium for a black or sooty-mold fungus, resulting in a black coating throughout the tree. This coating is removed from the fruit by washing, or in light attacks by brushing. In the investigation by Mr. G. Harold Powell® of the causes of decay of oranges while in transit from California, it was shown that the decay was greater in washed than in unwashed fruit. To avoid the washing of fruit it is necessary to destroy the scale in the orchards. @ Bul. 123, Bur. Plant Industry, U. 8. Dept. of Agriculture, 1908. 16 FUMIGATION INVESTIGATIONS IN CALIFORNIA. The black scale confines its attack mainly to the branches, yet it is commonly found on the leaves during its earlier stages of develop- ment and sometimes matures in this situation. Seldom does it mature on the fruit. The red and purple scales infest the branches, leaves, and fruit. The yellow scale occurs on the leaves and fruit. Occasionally it is found to a very slight extent on the branches. The more directly injurious effect to the tree resulting from the attacks of the red, purple, and yellow scales appears to the writer to be due to their ability to produce some toxic effect in the host plant in addition to the injury caused by the removal of sap. These scales cause a discoloration of the plant cells at the place where the sap is extracted, whereas the larger black scale causes no discoloration whatever. METHOD OF PROPAGATION OF THE MORE INJURIOUS SCALE PESTS. The young purple and black scale-insects hatch from eggs deposited by the adult, while the red and yellow scales produce their young alive. The red and yellow scales are thus susceptible to the applica- tion of remedial measures at any time throughout the year. The ege's of the purple scale are much more difficult to destroy than the insects, for the latter can be killed readily in any stage of develop- ment although more easily in the early stages. The black scale is capable, after it has reached its mature and leathery condition, of resisting extreme insecticidal applications. Its eggs, also, are quite as resistant as the mature insect, if not more so. In its early stages, however, it can be readily destroyed by the proper insecticides. In all species the different broods on citrus trees are seldom, if ever, distinct, but overlap one another to varying degrees. At certain periods the breeding is more marked than at others for each of these insects; yet it is possible to find adult red, yellow, purple, or black scales in the egg-laying stage at any time throughout the year in any extensive citrus locality in southern California containing thrifty trees and in which these scales are known to thrive. This over- lapping of broods is due largely to the forcing and artificial conditions of citrus culture. : METHODS USED IN THE CONTROL OF SCALE PESTS OF CITRUS TREES. The methods generally resorted to in the control of citrus insect pests are (1) fumigation, (2) spraying, and (3) the use of beneficial insects. The question of beneficial insects is too large for discussion in this limited report; suffice it to say that their work is of the highest importance in many respects. Sulphur sprays are employed against the red spider and the silver mite of the lemon. SHEET TENTS. iy Distillate sprays have been employed by southern California horticulturists for many years, and at one time very extensively in the control of citrus scales. The accumulated experience with these sprays appears to have demonstrated that the results secured are not entirely satisfactory. To-day distillate sprays are used only on a small acreage of citrus groves, having been supplanted by the more satisfactory fumigation with hydrocyanic-acid gas. Nothing illus- trates more distinctly the superiority of fumigation over spraying with distillate oils than the readoption of fumigation by the more successful citrus growers, and the attitude of the officials of the county horticultural commissions of this region who, almost to a man, now recommend fumigation for the control of scale-insects. A kerosene-water spray has found a limited use during the past year in Riverside and Ventura counties. FUMIGATION. Fumigation with hydrocyanic-acid gas originated and was first practiced in California by Mr. D. W. Coquillett, of the Bureau of En- tomology, in 1886, in combating citrus insect pests. Since that time it has gradually risen in favor as a means of destroying scale enemies of citrus plants until to-day it is in use in almost all the important citrus-producing countries of the world. The apparatus first used in fumigation was somewhat complicated and cumbersome, making the operation very expensive.? As the use of this gas became more widespread a gradual improvement in equipment as well as methods has taken place, so that to-day the process is comparatively simple. SHEET TENTS. Sheet tents exclusively are now used in southern California. The manipulation of sheet tents and the general procedure in fumigation have been so clearly explained in Bulletin No. 76 of this Bureau that it will not be necessary to devote space to them here. The tents are octagonal in shape, the standard sizes being 17, 24, 30, 36, 41, 43, 45, 48, 52, 55, and 64 feet, but larger ones up to 72 or 84 feet have been employed. The size of this style tent’is properly based on the dis- tance between the parallel sides, not on the distance between opposite corners. The materials especially recommended, and now generally used for fumigation tents in southern California, are 64-ounce special drill and 8-ounce special army duck, although 10-ounce special army duck is sometimes used in very large tents. The 64-ounce special drill is made of single threads twisted hard and closely woven. It is light, strong, and flexible. The special army duck is made of double «See Ann. Rept. U. S. Dept. Agr. for 1887, p. 123, 1888. 77488—Bul. 79—09——2 18 FUMIGATION INVESTIGATIONS IN CALIFORNIA, threads twisted hard and woven fairly close. This double-twisted material is heavier and much stronger than the special drill, but not so closely woven; consequently it is somewhat more porous. In field work the special drill will adapt itself more closely to the irregularities of the ground than the army duck, and particularly if the tents become damp. ‘The special 64-ounce drill is generally con- sidered the best obtainable for use in all fumigation tents up to 45 feet standard size. Special 8-ounce army duck is rec- ommended for use in tents of larger size. Prob- ably the most sat- isfactory method of making large tents is to have the center of spe- Fig. 8.—Tray commonly used for carrying the chemicals of fumigation cial duck and the from tree to tree. Cans above contain cyanid; pitchers below contain sides of special erate n a drill. This dis- tributes the heavy material at the points of greatest wear, while the drill makes the tent much lighter and more flexible. POINTS ON PROCEDURE. The number of men making up an outfit varies from three to six. Tn San Bernardino County most of the outfits consist of six men; else- where they more commonly consist of four. Tn estimating the dosage, the usual method is to make the estimate before the trees are covered with a tent. Sometimes this scheduling is done in the daytime, sometimes by night. The schedule for a row of trees to be fumigated having been given, either one of two methods of procedure is followed. In the first and more common method the dosage of cyanid and acid for each tree of the row is measured. out into small cans and pitchers, which are placed in a tray after the man- ner shown in figure 8. When ready for use this tray is carried from one tree to the next down the row (fig. 9). Frequently two trays are necessary to carry the material required for the entire row or set of trees. The water is carried in a pail and measured at each tree. The receptacles in which the gas is generated consist of earthenware jars holding 14 to 2 gallons, having the handle on the side (fig. 10). If dosages in excess of 16 ounces are used in a 14-gallon generator or DOSAGE SCHEDULES OF MORE IMPORTANT WRITERS. 19 in excess of 20 ounces in a 2-gallon generator, the contents will fre- quently boil over, especially if the cyanid is in small lumps or is powdered. DOSAGE SCHEDULES OF THE MORE IMPORTANT WRITERS ON FUMIGATION. Since the publication by Morse, in 1887, of the first dosage schedule for use in fumigating citrus trees with hydrocyanic-acid gas, a great many tables of dosage have been recommended through publica- tions in this coun- try and abroad. Among the more authoritative contributions on this subject are those of Coquil- lett, Morse, Craw, Marlatt, Johnson, Havens, |. Wood- worth, Pease, and Morrill, of this country; C.. P. Lounsbury, of South Africa, and W. J. Allen, of New South Wales. A careful study has been made of the dosage sched- ules proposed by these different in- vestigators with a result most surprising. In the first place, we must consider that uniform dosage will not be given to trees unless based directly on their cubic contents when covered with a tent. Secondly, dosage tables prepared for trees merely with regard to their cubic contents and without regard to the varying pro- portions of leakage surface present in trees of different sizes are faulty to a large degree. Of all the dosage tables which have come to the writer’s attention only those by Lounsbury, in South Africa, by Morrill, in Florida, and a recent one by Woodworth in California, have been based on the proper assumptions. The other tables were either based directly on the cubic contents without regard to leakage surface, or were prepared without amy knowledge whatever of the cubic contents represented by trees of given dimensions. Several Fria. 9.—Man carrying tray and water bucket. (Original. ) 20 FUMIGATION INVESTIGATIONS IN CALIFORNIA. belong to the latter class. The following statement and comparative table have been prepared which indicate the wide range of variation in these schedules: Dosage schedules—For the information of those who may be inclined to doubt the writer’s contentions in this bulletin with relation to the generally chaotic con- dition of fumigation schedules published in the interests of California citrus growers, a table has been prepared which includes nearly all of the more important sched- ules, together with a comparative analysis of the same. The dosages for trees of given dimensions were duly computed. Having this data at hand and utilizing the dosage allotted to each individual tree, it was possible to work out the rate of Fig. 10.—A typical California lemon orchard with row of fumigation generators placed ready for use the following night. (Original.) dosage per 100 cubic feet of inclosed space at which that particular tree was being fumigated. This has been done for all trees in the schedules proposed by several writers, and the results have been arranged in the latter half of the table. A glance at this table will show that the schedules of Morse, Coquillett, and Wood- worth were all based on the cubic contents of the trees, which were dosed at a uni- form rate, but without regard to the leakage of gas. Large trees are dosed at the same rate as small ones, thus giving a lack of uniformity in results. All of the other schedules detailed in this table were apparently prepared with little or no regard to the cubic contents represented by trees of different dimensions. Although it would appear from the table that leakage was taken into account, inasmuch as the smaller trees receive a greater rate than the larger ones, proper allowance could not be made for this factor without definite consideration of the cubic contents. Con- sequently the decrease of rate recommended is in all cases irregular and widely removed from a rate proportionate to the actual leakage. The fact that trees in- DOSAGE SCHEDULES OF MORE IMPORTANT WRITERS. 21 crease in dimensions much more rapidly than in cubic contents is seldom taken into consideration. The result is that the larger trees receive a relatively smaller dosage than they should. Morse’s schedule was prepared especially for the cottony cushion scale and probably for the redscale. Theschedules of Coquillett and Pease, and doubtless that of Craw, were prepared for the red scale. Those of Johnson, Woodworth, the Riverside Com- mission, and the Rural Californian were intended especially for use against the black scale. The red scale was generally known to be harder to destroy than the black scale. In Morse’s schedule all trees receive practically three-fourths ounce per 100 cubic feet of inclosed tent space; in Coquillett’s, practically one-half ounce to 100 cubic feet; in Woodworth’s schedule they receive one-third ounce for the same space. | In Craw’s table, the smallest tree receives approximately 9 times as great a dosage rate as the largest; in Johnson’s table, the smallest receives about 44 times the rate of the largest; in that of the Riverside Commission, the smallest is allowed about 13 times that of the largest; in that of the Rural Californian, the smallest receives about 8 times that of the largest; while in that of Pease, the smallest receives a dosage rate about 144 times as great as the largest tree. This short analysis seems sufficient to call attention to the irregularities of these schedules. A study of the following table will reveal many other interesting points, Dosage schedules recommended by several recognized authorities, with computed dosage rates per 100 cubic feet of space inclosed by tent. AMOUNT OF CYANID (OUNCES) PER TREE RECOMMENDED. } i | | é | River- Cubie | : 6 : ; = de Hor-) Rural Height| Width| con- yrore.a\ Coauil- | craw.c | Wood- | | Bur : > i d cultural) Cali- Pease.h of tree. | of tree. tents | | lett. roe | worth.e Commis-| fornian.¢ | aby sii Guuley. Ounces. Ounces. |Ounces.| Ounces. | Ounces. | Ounces. | Ounces. | Ounces. 4 5 5 5 6 4 6. 5 6 6 7 7 8 54 8 6 8 8 9 9 10 63 10 8 10 10 11 11 12 8 12 10 12 12 12 14 13 13 14 10 14 12 14 14 15 10 15 15 16 14 16 16 17 1% 18 14 18 16 18 18 19 19 20 134 20 16 20 18 20 20 20 22 22 18 a Bul. 71, Univ. of Cal. Agr. Exp. Sta. (1887). e Bul. 115, Univ. of Cal. eee Exp. Sta. (1896). b Insect Life (1889). f Farmers’ Bul. 127, U. S. Dept. Agric. ¢ Destructive Insects (1891). g From “Fumigation Methods, ” by W.G. Johnson. dCal. State Bd. of Horticulture (1896). h California Cultivator (1908). 22 FUMIGATION INVESTIGATIONS IN CALIFORNIA. Dosage schedules recommended by several recognized authorities, with computed dosage rates per 100 cubic feet of space inclosed by tent—Continued. AMOUNT OF CYANID (OUNCES) PER TREE RECOMMENDED—Continued. | | F | River- Cubie E : rs c = de Hor-| Rural Height| Width | con- | Coquil- | , Te Wood- | 5! : of tree. | of tree. one Morse. lett. Craw. Johnson. |} worth Meuiia te pte, Pease. i sion. Feet. | Feet. |Cubicft. Ounc es.| Ounces. ltneed Ounces. | Ounces. | Ounces. | Ounces. | Ounces. 24 18 55340) Soon eerie eee eeone es eek Sh ER ee eee 14 \\=./secese'le ae eee 24 20 Ck4O0 RI Ae ete lioeicfenyentres | 13 PAU en noes 16 2 fal ee eee = 24 2 4 7735 oe eeen (eee eee {eee RE a Oeee - SUE ce epee | 14 || tee eel 24 28 WED OOO sleet ree ree es eal en ae cee) hae he oe ao ee | 16) |). i. Sees shee 26 DXA | weasels Werte eal 3 Des TST eC Mis [eee Ea estos a SiR eo ne 30 20 Rev loeaeosee [Peeled Sek dia TE eee eee GN amma 16 Salle: nice 30 O57 el 2A680n eee aeaee [2s Ataed Slane poeta (Lewes 6 Sees eg 24'|_..-<0ee | ee 30 28:)]/ LAS S65 PE Bey eee aes Nal yo eet eee | ei ne 16: |.2332 05-0 eee 30 30 1656753 |SiecPa ell eee oe cl aya once lCae eee eee Pecan oaee, 24.) 22 ook lad eee 36 25 BSAC a Se 0 | Searels es es oe ery a ne ie |e ke ane 24 en oe eee eee 36 SOs ede Ol ain eee ae NS hm RET ec eee | pe Meee ea BS eS 2h 24) | coeds ee | COMPUTED DOSAGE RATE (OUNCES Ce PER 100 CUBIC FEET OF INCLOSED EK. i] . River- | Cubic A | - =e ; - de Hor-} Rural | Height} Width| con- Coquil- TSB Wood- |‘! areal of tree. | of tree. ay Morse. | “jett. | CTW- | Johnson.| worth. | eta a Pica | Pease. C 4 sion. Feet. | Feet. | Cubicft. Ounces.| Ounces. Ownces.| Ounces. | Ounces. | Ounces. | Ounces. | Ounces 4 4 40 (00 AT nS ar De ae | er PR eee ee ee Sees aoa Sdoodosas 4 5 COU een Leelee aacicistos SE ne Panne isd aera corpo cA lamin ejce | 6.6 5 5 80 Bey eee oaosod [5 Seke a hvnrs'lhateveye = Svopd Slam Slate re ragere ell oclenste cere aioe peepee \:.32 3 ere 6 4 MONEE Ree ale ce macteeree 1.4 AS ths Bs eee 1.4 On7T We eaecseeee 6 5 5010 ees ee See Pees! (Neen sn ce ares th ere Sew rie SS IIE Sel tr ey 4 6 6 140 (PM Bret e Sa elle So ea Sere 0: 360 Sree meeeeeoee 3.6 7 7 225 (A Oe eS et (ee ee ee Ne ee albacsonaecs lace cei Sidi Ramee reese tele eee 8 54 (Gl eteeocon|bectineo ca Garseeoslotsaascooe OP oo je reroll! Sree cieee ee eee eee 8 6 740 0) (aes Ae ee LS Pe il iP AV EeaGoeceee 75 . 63 | 2.5 8 8 335 (2 IE 25 eee a a ek ee Says | anes). Apa ob eee 2.1 9 9 475 Fo Wess A Ae eee eek a Gall eee Sy ela lee Sesto ne ee |e 10 63, STON Es MSIE hoe ee ea ee | Ce ey eae a 302, Socmcm cee alee soseen es Eee eee 10 8 435 rae 0.50 76 SBS Al oak tele BUY . 46 1.6 10 10 645 La Nine Me 5s Cee off HOME | CR eteteereinies| Spores eer 1. 25 11 11 870 SH an Re (Se Sareea Le oe ee a Ae oe anee cod lGaae noc oalloosce cre os 12 8 Ui Lal een ae Wa ee Sales er Ree Aero Eo BC YAH Rae Reece ooo oo ees 5s 12 10 10,0) Segoe Se 56 aO2 ABZ Sarno ee ae - 56 1 12 12 1,130 Vil race tsk sai seers | Meee eee Cin eet scoasSacas . 88 12 14 PAGO) cre sicne. H 58 AY RATE Eafe enters -33 fOr oll easeeeeree 13 13 1,440 71 | BSBA er Beene S| Saas ae | eee Cee eee Pe ete Goallbcocontecs 14 10 G60), eee. Ht: itl ee ee | ee eyo Pee ANN De looscegcess 14 12 ho Sy" eee tO heme te oe Bets Uy | See a Venn Are eS 14 14 14 1,790 Ait | BE Mai - 45 {45 ill ok wcese cule enue .28 . 67 15 10 TERIOR Bes eee eee ee ee te Sean, seen Abts Re eee eneecoohacarllarcoccccse 15 15 2,210 STALLS | eee eee ee ae fee Oy een (30) 'Seeciece oe cl ane deacon eeeeeeee 16 14 2 OS |eesaemes | Saal Romeraae Se een AE alee seasdatelasosencsT 57 16 16 2,680 | Ay | SR ere, Sea 34 JOSH [ara eee 3 yal 52 17 17 3,215 | TEA ee Ae oi ccscll fats yo tee etcetera | Cee ee eee 18 14 Ee BE ae ane oe an ne oar e TP MES Isa fal Swpecdlscoscecs - 18 16 S3080W oo eae cle eee ee 507 ee Ieee Ae aoe a2: -45 18 18 3,815 yA Os eae nes (eee eee IER See EOS mae oobsc ode oc 19 19 4,470 AST no oe: 2.) | eee aerate ee ERE ak NE lif eRgueeete ree AEE sce cose: 20 Tee (OsavGy Aa oe - ee ree rs 8 | ere Dee Ae en! AG] See MRA Rare ailomoasss+s 20 16 Os ASOEl eee ee | eeciemraetae Apil ODIs Sewebeininee .29 2 1Q)\| 22-222 20 18 4,325; |on.cinss col Sacer | eet owns 0h | erie Seen 502) Ils cose acces |S 20 20 5,235 78) a eee eel isaeewredelomecae cen pea eee A a BAER esr (sscocrs esc 20 22 564010) eaen eee Ree ese 2 he sok ele RN See |e caeite i eR Ec icscoo7 22 18 4 B50n|sseeenes AES... 5bi0 Da See ae | aesecsoosa aoe speesc AMS) |Eaascoscuc 24 18 eGYAl) Snes eae |? : eR ee es 3345 eee (2642 22 hao cece | Seeeeeeeees 24 20 6,490 Reese ea ec ceeeere - 20 STs |e pteese ce 225 SI |Saossecce= 24 22 TO TOD Aaa eee ee aes) 3 | Nr A ena le a pet Ml peceeeee lscecce cons 24 28 125900" seg ss cle Soe eke Rees ee Selb ae ae eeeeee aoe Filet eosaaesen soos soss ac 26 20 CEA Vid eee cea (Meee aes eres EL OM Ih 2 ycrctck coe lle eee Og | em ae Ba Ags = 5555 30 20 833754 S22 et salen il Gil Pecan AeA Se et .19 a) 30 25 lal 2 680i 2 seen ate e eee eee eee rca Oe TER Be So Pe ea Bot eco. 30 OS NW ACS SBB. |i heh tee leak Wo cel Neen, rty Boe Ut eee MAT ss. c0 sce Seen 30 30 V6; 675i lin: Soa. 2 este eet broee aoes | Genes cee ame eee fe eee ae arias ce damsc 36 25 153630 ioe 2:58) Asse tees | Reet ee eee ale Soe eee eee v1b5| 522 yea Ses 36 30: || 21 9LS NC eae Be ee ee eee a ciete eters ate | enero sree pp I Re ee crc fs . ———— PRESENT SYSTEM OF SCHEDULING DOSAGE. 23 THE PRESENT SYSTEM OF SCHEDULING DOSAGE. When we understand that up to the present time only one approx- imately accurate dosage schedule has been proposed by the fumiga- tion experts of California, and, what is more confusing, that no two tables agree in all respects, we can not wonder that the practical fumigator has turned from them in perplexity. Finding the tables of little assistance, the fumigator has had to determine his own dosage from practical experience and the results secured. If he failed to destroy the scale on a 6-foot tree in using 1 ounce of cyanid, he increased his dosage for the next 6-foot tree, and so on. He has also learned that the dosage required to: destroy some scales is greater than that for other species. Under the system at present in vogue the dosage is usually estimated in the daytime. The estimator, who ordinarily is the man in charge of the outfit, starts out in an orchard equipped with cross-section paper or a schedule sheet. He walks between two rows of trees, jotting down in the corresponding squares of the schedule sheet the dosage which he believes the trees should receive. If he is a careful scheduler he will look at the trees from different sides before indicating the dosage, as trees are sometimes more compact on one side than on another. Less careful men set down the dosage for the two rows of trees while moving along as fast as they can walk. The writer has seen some schedulers walk through the field at a rapid pace, taking four rows at a time. The estimation of dosage in this manner is mainly guesswork. Measurements of the trees are made by the eye; consequently, suc- cessful results depend very largely upon the accuracy of the estimator’s eye-measurement, supported by his experience in fumigation. The most careful of estimators are very irregular in their scheduling. ° This point has already been mentioned by Professor Woodworth.@ From measurements taken after many fumigators, we have found none who did not at times vary more than 50 per cent in dosage esti- mates for trees containing exactly the same cubic contents after being covered with a tent. Frequently the variation is as high as 100 per cent. The results secured by a few of the more careful and expert schedulers have been good as a whole. These men, however, can cover but a small portion of the citrus groves of southern California in one season. The writer has been shown orchards in which it was stated that all the scale had been destroyed by the use of heavy dosages. Even if this were the case it would show that the smallest percentage or strength of dosage used on any tree in those orchards was sufficiently large to destroy the scale. Since, as we have found, expert fumigators @ Bul. 152, Univ. of Cal. Agr. Exp. Sta., 1903. 24 FUMIGATION INVESTIGATIONS IN CALIFORNIA. vary considerably in their estimates, many trees in the above-men- tioned orchards must have received a much greater dosage than was necessary for scale eradication, thus resulting in a waste of cyanid and acid. In Table I have been arranged the dosage estimates which were scheduled in different orchards by three different fumigators. After the trees had been covered with tents the exact contents were com- puted by the writer from actual measurements. The dosages given in these tables are not for scattered individual trees selected because of their irregularity in size, but each table embraces a continuous number in a single row taken at random, regardless of the size or regularity of the trees. As great a lack of uniformity as that shown -in each table might be looked for throughout the orchard. These schedules of dosage were used against the red and purple scales, species considered by most fumigators to be about equally resistant to the gas. The reader will note the wide difference in the dosage in the estimates of the different fumigators. TaBLe I.— Variation in the dosages estimated for several consecutive trees by three different Jumigators. Work of first fumigator. | Work of second fumigator. W ork of third fumigator. | Volume | | Volume Volume Actual Actual | aes Actual rar Dosage | volume orepee Dosage | volume ohepae Dosage | volume ore ar recom- of t e h | recom- of to each | recom- Co) : es mended. | treated c eee mended. | treated oe mended. | treated g eae area ounce of eae ounce of ae ounce of f dosage. dosage. dosage. | | Ounces. | Cubic feet. Cubicfeet.| Ounces. | Cubic feet., Cubic feet.| Ounces. | Cubic feet.| Cubic feet. 11 1,690 150 lal 1, 000 90 6 1, 500 250 12 2,050 170 Th 400 60 4 | 1, 100 275 10 1, 369 135 15 1, 800 120 4 809 200 10 | 1, 663 165 10 600 60 5 | 1, 200 | 240 10 1,516 150 16 | 2,200 140 4 | 1, 100 275 12 1, 440 120 15 1, 800 120 4 | 900 225 12; ° 1,663 140 16 | 2,400 150 5 | 1,300 260 12 1, 755 145 16 | 2,000 125 5 1,150 230 12 | 1,350 110 18 | 2, 200 120 5 | 950 190 9 1,175 130 17 | 2, 200 130 4 | 950, 238 BS Spits Sie coett ty ost nant eral S Sierra 12 1, 250 105 5 900. 180 Bene ee ee ne eee oe tal 16 2, 500 156 6 1,550 258 THE INITIAL PROBLEM CONFRONTING THIS INVESTIGATION. After becoming acquainted with the existing methods of fumiga- tion, it was realized that one of the first problems to be solved was to devise some accurate system of determining dosage which would obviate the errors due to guesswork. It at once became apparent that the only way in which this result could be attained was by determining accurately the cubic contents of the space inclosed by the tent and giving the tree a dose proportionate to the contents. It was also apparent that before such a system could be put into operation, after having been worked out in practice, it would be COMPUTING VOLUME AND DOSAGE FOR TENTED TREES. 25 necessary to determine by an extensive series of experiments the dosage required for different-sized trees for the various scale pests infesting the citrus orchards. METHOD OF COMPUTING VOLUME AND DOSAGE FOR TENTED TREES. Although most citrus trees possess a certain general similarity in shape, they are nevertheless somewhat irregular, no two ever being identical in all respects. This renders it impracticable to determine the exact contents of any given tree. For field work, however, this is unnecessary, and all that is needed is to approximate it with a fair degree of accuracy. In order to calculate the cubic contents of an object, it must be considered as shaped like some regular geomet- rical figure or figures. The figure which most closely approximates in shape an orange or lemon tree before it has been pruned is a cylin- der surmounted by a hemisphere, and in computing the volume we have considered them of this shape. If we know the height and width of a tree covered with a tent, it is a comparatively simple matter to calculate its contents. In the past in California work the dosage has been based upon these two measurements. After a tree is covered with a tent it is a matter of some difficulty to determine the height and the width. By using as factors the distance around the bottom of the tent and the longest distance over the top of the tent we arrive at a more prac- ticable method by which to compute the cubic contents of a given tree. Using these measurements as a basis the writer has invented a formula * by means of which the cubic contents of a tree may be computed. To avoid computation work in the field as far as possi- ble, the writer has formulated a table approximating the cubic con- tents of trees of different dimensions, which is, he believes, sufl- ciently extensive to include any citrus tree in southern California. During this investigation no tree has been found whose dimensions did not fall within the limits given in this table. The distance a Professor Woodworth (Bul. 152, Univ. of Cal. Agr. Exp. Sta., p. 5, 1903) was the first to propose a formula for obtaining the contents of tented trees by computing the distance around the bottom and over the top. An analysis of this formula during the early part of the writer’s field work proved that it was inaccurate, thus necessi- tating the determination of a new formula. The writer has worked out a formula based on the two measurements above mentioned. It is as follows: CO C3a—4) Foe i a) In this formula C=the circumference of the tree. O=the distance over the top of the tree. ; C? C(3xz—4) If a person works out and notes down in a chart the values of 4, and — y= for different values of C' of which he is apt to make common use, it is possible by its use in connection with the formula to determine the contents of trees with fair rapidity. 26 FUMIGATION INVESTIGATIONS IN CALIFORNIA. around and over a given tree being known, the table will show the approximate cubic contents of the tented tree. The dosage can then be applied in proportion to the contents and at any strength desired. A lemon tree, after being pruned, is flat on the top. Therefore we can not consider the geometrical figure which is applicable to an orange or unpruned lemon tree as also applicable to a pruned or flat- topped lemon tree. The figure which approximates the latter is a cylinder. Now it so happens that the contents of a cylinder having certain dimensions over its top and around its bottom are almost the same as for a figure of the same dimensions composed of a cylinder surmounted by a hemisphere. This is a great advantage inasmuch as the schedule of dosage proposed for orange trees may also be used for all lemon trees, thus obviating the necessity of preparing two different schedules. METHODS FOR OBTAINING THE MEASUREMENTS AND DOSAGE OF TREES. WITH APPARATUS. Of the various methods suggested for obtaining the measurements of tented trees, the first was naturally by the use of a tapeline. It was an easy matter to ascertain the distance around the tent with a tape, but to measure the distance over the top was much more diffi- cult. This required the services of two men and repeated efforts. For field work on a commercial scale this was impracticable. Woodworth” explains a method of securing measurements, which consists in the use of a fishing rod and a wire line, the latter marked off by knots into 1-meter Terai be: His Hecerip aon of this method is as follows: Having first attached the line at about its middle to the end of the rod, one end of the former is made fast to the tent. The most convenient way to accomplish this was found to be by means of a hook, like a fishhook from which the barb had been removed. The most convenient place of attachment was at a point 1 meter from the ground. After attaching one end of the line to the tent the rest of that half is caused to lie up to and over the center and top of the tent by means of the rod. The one making the measurement then walks around to the opposite side of the tent, rod in hand, holding the line constantly in position over the top. The other end of the line is carried around the tent at the same time and is then drawn taut, measuring the last fraction of a meter by means of the graduation on the lower joint of the rod. Adding now | meter, the distance the first end is from the ground, we have the measurement of the distance over the top of the tent from the ground on one side to the ground on the other. A second measurement was then taken by throwing the line off the top of the tent by means of the rod and holding it so that as the measurer proceeds around the tent to the point where the line is attached, it will encircle the tent at a point about1 meter from the ground. The end of the rod is again brought into requisition and the last fraction of meter read in centimeters. Both measurements are thus made by one person in a single trip around the tent. a Bul. 152, Univ. of Cal. Agr. Exp. Sta., 1903. METHODS FOR OBTAINING MEASUREMENTS AND DOSAGE. rae This method might be practicable with a medium-sized tree, but for trees of large size, especially seedlings, which are sometimes more than 30 feet in height, its use would doubtless prove difficult, and for field operations multiplication of apparatus should be avoided as far as possible. WITHOUT APPARATUS. The Woodworth system.—The first scheme, so far as the writer’s knowledge goes, for obtaining the measurements and dosage of trees without the use of apparatus was suggested by Professor Woodworth.¢ This method consists of marking on the tent, on two opposite sides and parallel with the edge, a series of limes which are placed at such distances from the center of the tent that they will correspond with differences of 1 ounce in the dosage of trees of the average shape. Upon each of these lines are marked three num- bers; the first indicating the dose (in ounces), the second the cir- cumference on which the dose is based, and the third the amount the dose must be varied when the actual measured circumference is greater or less than that marked on the tent. For trees having a circumference greater than the average between the second figure on the line that is nearest the ground on one side of the tent and the second figure on the corresponding line on the opposite side, the average dose is increased for each additional yard of circum- ference by the amount (in ounces) given by the third figure on the line; for trees having smaller circumferences the figures are corre- spondingly decreased. Although the system is fairly accurate, its adaptability for use under the present condition of fumigation in southern California is somewhat questionable. The amount of calculation required to ascertain the dosage for each tree gives large chance of error and is wasteful of time. The possibility of error is still further increased through the necessity of varying the dosage for different species of scale-insects. | The Morrill system.op—Dr. A. W. Morrill, in the course of his work against the white fly (Aleyrodes citri R. & H.) in Florida, has devised a method of marking tents which is easily the most practi- cable yet proposed for obtaining the distance over the top of a tented tree. Although apparently a modification of the idea presented in the Woodworth method, it is really quite different. In the Wood- worth system the actual dosage is calculated from the figures on the tent. The Morrill system is merely a rapid and simple way of obtaining the distance over the top of a tented tree. @ Bul. 152, Univ. of Cal. Agr. Exp. Sta., 1903. 6 Bul, 76, Bur. Ent. U. 8. Dept. Agr., 1908. 28 FUMIGATION INVESTIGATIONS IN CALIFORNTA, In figure 11 is shown an outline of a regulation fumigating tent marked after the Morrill system. Three parallel lines and one line at right angles to them are indicated on the tent. The middle one of the three parallel lines passes through the central point in the tent canvas, running lengthwise of the central section or strip of which the tent is made and passing over the top of the tent from the edge on one side to the edge on the opposite side; these lines Fia. 11.—Outline of a fumigation tent marked according to the Morrill system. also run in the direction in which the tent should be pulled on or off a tree. The single line at right angles to the parallel lines passes through the central point, as does the middle one of the three parallel lines, and extends also from the edge on one side to the edge on the opposite side. Beginning at the center these lines are graduated in feet toward either edge of the tent, after the manner shown in the diagram. For tents above 36 feet (average size) it is unnecessary to commence the graduation nearer than 5 feet from the center of the canvas. When one of these lines is over the middle of the tree METHODS FOR OBTAINING MEASUREMENTS AND DOSAGE. 29 (fig. 12), the distance over can be calculated by merely adding together the two numbers on the opposite sides of the tent where the edge touches the ground. For instance, suppose that on the line over the center of the tree 12 is nearest the ground on one side and 15 on the other. The distance over the center of this tree would be the sum of these numbers, which is 27 feet. With the lines graduated after this manner it makes little difference in determining the distance over the top of the tree whether or not the geometrical center of the tent is at the center of the tree, the single requirement being that some part of one of the graduated lines approximates the center of the tree. Fig. 12.—A fumigation tent marked after the Morrill system. (Original.) The two lines running parallel to this central line should be about 4 feet distant from it in the larger fumigating tents. The reason for using these auxiliary lines is, that in practice the center of the tent is very often pulled considerably to one side, especially in covering small trees. If the middle line does not fall immediately over the center of the tree, one of the other two lines is quite likely to do so, and that one should be used in obtaining the distance over. The cross line running at right angles to the three parallel lines also passes through the center of the tent and is marked like the others. In case of an irregularly shaped tree, by the use of this line the distance over can be taken in two different directions and the average taken for use in determining the cubic contents. In field work, however, this cross line is unnecessary, as measurement over the top in one direction is sufficient. 30 FUMIGATION INVESTIGATIONS IN CALIFORNIA. The measurement around the bottom of the tent can be obtained by the use of a tapeline or by pacing. Under this system the work is facilitated by having a chart or table of figures showing the cubic contents corresponding to different dimensions. THE CHEMICALS REQUIRED IN FUMIGATION. For the generation of hydrocyanic-acid gas in fumigating, potas- sium cyanid, sulphuric acid, and water are necessary. The hydro- eyanic-acid gas is produced by the action of the sulphuric acid on the eyanid of potassium. Under the early methods of generating hydro- cyanic-acid gas the cyanid was dissolved in water before being used. At the present time cyanid is used in the crystal form entirely. The water is first measured out and poured into the generating vessel. The required amount of acid is then added to the water, producing a great increase in the temperature of the mixture. While the mixture is hot it should be placed beneath the tree and the cyanid added. If permitted to cool before the cyanid is added, the generation of gas will not only be slower than with the heated mixture, but the amount of available gas will be decreased, thus making the operation more expensive, and necessarily less efficient. POTASSIUM CYANID. An imported cyanid designated as 98 to 99 per cent pure is used almost exclusively for fumigation purposes in southern California, under the popular belief that it is superior to American cyanids for this purpose. There seems to be no real basis for this common belief, - and, in fact, experiments conducted by Prof. Wilmon Newell while State entomologist of Georgia demonstrated that certain brands of American cyanid met all the requirements necessary for fumigating nursery stock, and it seems reasonable to believe that these will also be equally available for citrus-orchard fumigation. A series of laboratory and field tests has been planned to demonstrate the use- fulness of all the available brands of potassium cyanid. In the field investigation reported in this bulletin the 98 to 99 per cent imported cyanid commonly used in southern California has been employed throughout and, although no chemical analysis was made, the results proved entirely satisfactory. SULPHURIC ACID. Too much stress can not be placed upon the quality of sulphuric acid used in fumigation. Operators have repeatedly informed the writer of much burning of fruit and foliage which occurred during the season of 1905, owing to the use of a grade of acid differing from that ordinarily employed. An analysis of the acid used that season THE CHEMICALS REQUIRED. ok showed that it contained traces of nitric acid, the presence of which might explain the burning. Nitric acid is one of the most active of chemicals and is unstable as well. When heated it readily volatilizes. By adding sulphuric acid to water a great amount of heat results. If nitric acid be present in the sulphuric acid as an impurity it would be far more volatile than under ordinary circumstances. The addition of the cyanid increases the heat, at the same time causing hydro- cyanic-acid gas to be violently thrown off. This gas assists in carry- ing off the volatilized nitric acid, which, condensing on the cool, moist surfaces presented by the fruit and leaves of the citrus trees, might result in burns or pits. In procuring sulphuric acid for fumigating purposes, only that should be purchased which is entirely free of nitric acid, and which is guaranteed 66° (Baumé), or 93 per cent pure. Some commercial sulphuric acid on the market meets all the requirements of fumigation, while much can be found which does not. To enter fully into the reason for this would be out of place in this bulletin. All that is necessary is to mention briefly the char- acter of the material and processes used by various manufacturers, some of whom strive to place a better grade of acid on the market than do many others. ) In the manufacture of sulphuric acid, sulphur may be considered the basic element. This is obtained from one of two sources, viz, from free sulphur, known commercially as brimstone, or from sulphur in combination with a metal, as iron or copper pyrites. Brimstone is comparatively pure sulphur, containing little or nothing which would reduce the grade of the acid manufactured from it. It some- times contains a very small quantity of ash. Pure iron pyrites con- tains about 53 per cent of sulphur and about 47 per cent of iron. Copper pyrites contains much less sulphur. Ordinarily the pyrites used in making acid contains small quantities of other elements, as arsenic, zinc, lead, etc. To manufacture sulphuric acid, it is neces- sary to convert the sulphur into a gas, sulphur dioxid, which is brought about by burning the crude product in a retort. The sulphur dioxid thus formed is conducted into certain chambers where it is mixed with fumes of nitric acid, air, and steam, the resulting product being dilute sulphuric acid. Where brimstone is used comparatively pure sulphuric acid is formed. When, however, pyrites are burned, other elements present in the ore (as arsenic, etc.) are volatilized, pass along with the sulphur dioxid, and are present in the crude acid. That which concerns us most vitally in fumigating is the presence of nitric acid. A much greater proportion of nitric acid becomes mixed with the products of combustion from pyrites than from brim- stone, resulting in the presence of a larger amount of this undesirable 32 FUMIGATION INVESTIGATIONS IN CALIFORNIA. acid in the sulphuric acid. The impurities, including nitric acid, may be eliminated by refining. This, however, requires extra expense, and, as these impurities are of little or no importance in some of the lower uses to which sulphuric acid is put, the acid is not usually refined. Such acid is unsuitable for use in fumigation. Taking all things into consideration it is safer, in purchasing ordinary commercial sulphuric acid on the market, to order that made from brimstone rather than that made from pyrites ore. It is possible, however, to secure quite as good a product from pyrites as from brimstone, if the former be sufficiently refined. If the fumi- gator demands that it be free from nitric acid, arsenic, etc., and refuses to accept it unless the product is of the grade required, there is no reason why he should not be able to secure satisfactory material. PROPORTION OF MATERIALS USED BY FUMIGATORS. With each dry ounce of potassium cyanid most fumigators use 1 fluid ounce of sulphuric acid, although some use 1} ounces. The proportion of water used varies all the way from 2 to 8 times the amount (by bulk) of acid, the majority using between 3 and 4 parts of water. THE AMOUNT OF SULPHURIC ACID NECESSARY. Chemical combinations take place with definiteness; that is, when one chemical acts on another in the production of a third substance, the proportion between the first two chemicals is always the same. Such is the case when sulphuric acid acts upon potassium cyanid in producing hydrocyanic-acid gas. A given amount of cyanid requires a certain amount of sulphuric acid of a fixed degree of purity to carry the reaction to completion. A quotation from a letter received from J. K. Haywood, of the Bureau of Chemistry of this Depart- ment, illustrates this point: In the action of sulphuric acid on potassium cyanid approximately four-fifths of an ounce (avoirdupois) of 93 per cent acid is used up for every ounce of 98 per cent cyanid.@ Expressed in fluid ounces four-fifths of an ounce avoirdupois equals about 0.42 of a fluid ounce. We may say that theoretically 1 ounce avoirdupois of 98 per cent potassium cyanid needs 0.42 of a fluid ounce of ordinary commercial sulphuric acid (93 per cent) to convert it entirely to hydrocyanic acid. Since it is always best to have some excess of the acid to carry the reaction to completion, it is probable that three-fourths of a fluid ounce of commercial sulphuric acid is ample in practice to convert 1 ounce avoirdupois of 98 per cent potassium cyanid to hydrocyanic acid. If 1 fluid ounce of the commercial sulphuric acid is used it will certainly leave a con- a The reaction is as follows: 2KCN+H,SO0,=K,S8S0,+2HCN. PROPORTION OF CHEMICALS. 33 siderable excess of sulphuric acid present. It is perfectly possible, however, that this excess of sulphuric acid is of value in heating up the mixture so that more of the hydrocyanic acid is liberated and not absorbed by the liquid. The results of some tests serve as a further illustration of this point. It was desired to determine by experiment if 1 fluid ounce of acid to each ounce (avoirdupois) of cyanid would be sufficient to carry the reaction to completion in the liberation of hydrocyanic- acid gas. It is to be understood throughout that the cyanid ounce is avoirdupois and the acid and water is the fluid ounce. For this test two series of ordinary 14-gallon fumigating vessels were placed in line. In one series equal parts of acid and cyanid were used. Three parts of water were used in all cases. The amounts of cyanid used ranged from 1 to 10 ounces, that is, in one generator were placed 1 ounce of cyanid, 1 ounce of sulphuric acid, and 3 ounces of water; in the next of the same series, 2 ounces of cyanid, 2 ounces of sulphuric acid, and 6 ounces of water, and so on in the same pro- portion up to 10 ounces. The second series was identical with the first except for the use of one-fourth more acid than cyanid. After generation had taken place for about one and one-half hours an examination was made of the residue. In the first series, in which equal parts of acid and cyanid were used, the residue was in the form of a liquid. In the second series, in which 1} ounces of acid to 1 of cyanid were used, the residue in several pots had collected in a mushlike mass. Being puzzled at first over this phenomenon, in order to ascertain if cyanid still remained unchanged in the residue the writer added more sulphuric acid, but there was no further evolu- tion of gas. This at once demonstrated that all the available cyanid had been dissolved. Analyses of this residue by J. K. Haywood of the Bureau of Chemistry showed that the reaction was complete both when 1 ounce of acid and when 1} ounces of acid to 1 of cyanid were used. In submitting the result of these analyses, Dr. H. W. Wiley, Chief of the Bureau of Chemistry, wrote: The amount of cyanid present in these samples is so small that it does not indicate to us incompleteness of reaction, but rather indicates the amount of hydrocyanic acid dissolved in the residue. This view of the case is strengthened by the fact that increasing the amount of sulphuric acid in the cases above did not decrease the amount of cyanogen present in the residue. From our work, therefore, we are of the opinion that the same amount of sulphuric acid as of potassium cyanid is sufficient to carry the reaction to completion. «In an address printed in the Proceedings of the Thirty-fourth Annual Fruit Grow- ers’ Convention of California, p. 103, the proportion of chemicals spoken of appears somewhat different from that mentioned in this publication. This is due to the fact that the parts mentioned in that address were based on parts by weight of acid and cyanid, both of which are chemically pure—not the commercial product as given in this bulletin. 77488—Bul. 79—09——3 34 FUMIGATION INVESTIGATIONS IN CALIFORNIA. Sumining up, it may be said that 1 fluid ounce of commercial sul- phuric acid (93 per cent) to 1 ounce (avoirdupois) of 98 per cent potassium cyanid is certainly enough to carry the reaction to com- pletion in the liberation of hydrocyanic-acid gas and is perhaps an unnecessarily large amount. In practical field work where dosages of varying sizes are constantly being used, it is very convenient to reckon the acid in the same number of parts as the cyanid. The use of 1 part (fluid measure) of acid to each part of cyanid is there- fore recommended. The commercial potassium cyanid sold on the market is usually 96 to 100 per cent pure. The commercial sulphuric acid on the market is sold as 66° Baumé and should contain 93.5 per cent sulphuric acid. In California fumigation work, these grades are used and are to be understood wherever cyanid or acid is mentioned in this bulletin. In the dosage allotments cyanid is always measured in ounces or parts dry weight, while the acid is measured in fluid ounces or parts. THE EFFECT OF TOO GREAT AN EXCESS OF ACID. In the experiment mentioned, in which two series of hydrocyanic- acid gas generations were completed, the question immediately arose, why the residue in some generators, in which 1} parts of acid were used, congealed, while in the case of those in which equal parts of acid and cyanid were used no such result was noted. The explanation is simple: When sulphuric acid acts on potassium cyanid, hydrocyanic acid, a gas, and potassium sulphate, a solid, are formed. , If sufficient water is present, the potassium sulphate dissolves and there is no solid residue. This was the result when equal parts of acid and cyanid were used. When one-fourth more acid than cyanid is employed, there is a large excess of acid. The potassium sulphate is not as soluble in water containing excess acid as it is in water alone; hence it undergoes partial crystallization, resulting in a mushlike residue or congealing into a solid mass. WATER AS A FACTOR IN FUMIGATION. There are several reasons why water should always be employed in fumigation: It is very useful in dissolving the potassium cyanid and hastening and completing the chemical reaction with the acid. A piece of cyanid thrown into a mixture of acid and water imme- diately gives up a portion of its mass in solution. Scarcely has the cyanid dissolved when it is partially converted into gas. The heat liberated during this process assists in forcing the solution of more cyanid, which is also partially converted into gas. This continues until the chemicals are exhausted and the reaction stops. Potassium sulphate, a solid, is the by-product resulting from the reaction by which hydrocyanic-acid gas is produced. Water dis- PROPORTION OF CHEMICALS. 35 solves the potassium sulphate as it forms and prevents it from coating the cyanid not yet in solution. In the presence of an insufficient amount of water, the potassium sulphate is not completely dissolved, but forms a coating on the pieces of cyanid, preventing the sulphuric acid from penetrating to it, and thereby retarding, or even in part preventing, the reaction. In such cases this undissolved potassium sulphate usually congeals, causing the pots to “‘freeze.’”? The phe- nomenon always occurs where the formula is 1-1-1, or where the same amounts of water, acid, and cyanid are used. On agitating the congealed residue by stirring, it is almost always possible to find small pieces of undissolved cyanid enveloped in a coating of the potassium sulphate. Ordinarily, when the residue is stirred the particles of cyanid are removed, to some extent, from this envelope of potassium sulphate, allowing some of the unused acid to reach them, and thus evolving a small amount of gas without the addition of more acid. Under these conditions, however, the reaction is never complete, and it is highly desirable therefore to add sufficient water at the beginning to dissolve all the potassium sulphate. From this last statement, as well as the data presented under the heading “The effect of too great an excess of acid”’ (p. 34), it is seen that the congealing or ‘‘freezing”’ of generating jars is due to either or both of two conditions: (1) An insufficient amount of water to completely dissolve the sulphate of potassium, or (2) a large excess of sulphuric acid, whereby the water is rendered less capable of taking into solution the same amount of sulphate as it otherwise would. Another very important function of the water in the reaction is the heat produced by the union of the sulphuric acid and water. Potassium cyanid introduced into this heated mixture gives off hydro- cyanic-acid gas much more quickly and thoroughly than at a lower temperature, and in field work rapid generation of gas is essential. THE EFFECT OF DIFFERENT PROPORTIONS OF WATER ON THE TEMPERATURE OF THE GAS. Anyone who has watched the escaping gas and steam from the reaction of potassium cyanid and sulphuric acid wherein different proportions of water were used could not fail to notice that the violence with which the generation starts and the gas is given off is apparently greatest with the smaller proportions of water. Fumi- gators are aware of this, and commonly increase the proportion of water when using large amounts of cyanid. Practice has demon- . strated that with a greater proportion of water the injurious effect of the resulting gas on the leaves and fruit is materially lessened. The lessening of the injury has been attributed to the fact that the escap- ing gas was less heated when large proportions of water were used. In order to clear up this point an experiment was performed, the results of which are given in Table IT. 36 FUMIGATION INVESTIGATIONS IN CALIFORNIA. TaBLE I1.—Experiment to determine the effect of different proportions of water on the temperature of the resulting gas. | { ‘ : | Amount of chemicals used. : Tempera- Tempera- ae ture of the | vpeid and. | ture of the | fos ove water mix-| __hydro- from start Cyanid.| Acid. | Water. ; a. eyanic-acid of sabes | Bas. ee | | Ounces. | Ounces. | Ounces. OUR wa, oh. | 5 orn) 5 180 124 115 | 5 Sue! 10 190 126 121 | 5 5 15 170 128 109 5 5 20 160 128 105 5 5 | 25 145 118 | 105 | 5 5 30 136 108 104 5 5 40 125 90 | 87 In this experiment 5 ounces (avoirdupois) of cyanid and 5 ounces (fluid) of acid were used for each test. The proportions of water were varied, 5, 10, 15, 20, 25, 30, and 40 ounces, respectively, being used. As a result the proportion of water to 1 part of acid or 1 part of cyanid was 1, 2, 3, 4, 5, 6, and 8, respectively, for the different tests. These generations were made in a 14-gallon fumigating vessel in a room. The temperature of the escaping gas was taken at the mouth of the pot. The temperature of the acid-water mixture was taken one minute after pouring the two together. The cyanid was then added. The maximum temperature of the escaping gas is always realized within the first minute, usually thirty to forty seconds after the gener- ation commences. Examination of the maximum temperature of the gas as noted in the third column of the table above indicates that the temperature of the gas is reduced when large proportions of water are used. When using from 1 to 4 parts of water, the temperature is nearly uniform, but with 5 parts of water the decrease becomes marked. Repetitions of the above experiment gave similar results. The violence of the reaction and the temperature of the gas are affected more or less by the size of the pieces of cyanid. A very violent reac- tion results from the use of eyanid in powdered form. We would expect that to increase the proportion of water would decrease the temperature of the gas. One reason is shown in this table under the column marked “Temperature of the acid and water mixture.” As the proportion of water to sulphuric acid becomes larger the resulting temperature of the mixture is lessened. Hence when the cyanid is added to the mixture as high a degree of heat to start the reaction is not developed as when the smaller proportion of water is used, and in consequence gas is evolved less violently. THE TEMPERATURE OF THE GAS WHERE LARGE AND SMALL DOSAGES ARE USED. In an experiment to determine the temperature of the gas result- ing from large and small dosages (Table III) the chemicals were used in the following proportions: Cyanid 1 part, acid 1 part, and water PROPORTION OF CHEMICALS. BIL _3 parts. The reactions were accomplished in 2-gallon earthenware fumigating vessels in a room where the air was moderately quiet. The temperature of the gas was taken at the mouth of the vessels. Tasie III.—Experiment to determine the temperature of the gas resulting from large and small dosages. | Amount of chemicals used. | : Time Time | mf aes after Temper- | Highest | after gen- enn | Temper | La mixing | ature of | tempera-| eration ae Seeree: | ture of an it t f ih gas one | gas two mixture wae TEU ure.0 wien | minute | minutes | eeacid tempera-| at end hydro- | tempera- | from (rom Cyanid.! Acid. | Water. | sath, ture of | of one | eyanic- | ture of nora SGirR eaten mixture | minute. | acid gas.| gasis | elon ae “* lis highest. | highest. me Roa? Ounces. | Ounces. | Ounces. RIE Seconds.| °F. ae Seconds. wat Sr on | 3 9 135 | 30 131 100 | 30 83 73 6 | 6 18 163 | Bie || 157 | 130 | 30 104 86 8 8 24 167 25 160 | 135 30 106 92 10 10 30 170 25 164 132 30 103 90 12 | 12 36 164 30 157 140 | 30 113 | 95 14 14 42 | 178 25 =. Lvar | 145 | 25 116 | 98 16 16 48 173 20: | 161 iy al 25 118 | 99 20 | 20 60 172 25 168 153 | 25 123 106 An examination of this table shows that the temperature of the escaping gas increases somewhat as the dosages become larger. Hence if heated gas is more injurious than cooler gas, we would ex- pect more burning as a result of the increased dosages. This is exactly what does happen to some extent in field operations. It is interesting to note that the highest temperature of the acid-water mixture occurs about one-half minute after the mixing takes place. The highest temperature of the hydrocyanic-acid gas occurs about one-half minute after the generation commences, and then the tem- perature of the gas rapidly decreases during two to two and one-half minutes, at the end of which time most of the gas has been evolved. At the expiration of from three to five minutes the generation of gas has practically ceased. THE EFFECT OF DIFFERENT PROPORTIONS OF WATER ON THE AMOUNT OF AVAILABLE HYDROCYANIC-ACID GAS. In the course of this investigation an experiment was made to deter- mine the amount of hydrocyanic-acid gas available when generated with different proportions of water. The results as determined by the Bureau of Chemistry of this Department are given in the accompa- nying chart (fig. 13). In these experiments commercial sulphuric acid, 66° Baumé or 92.77 per cent pure, and potassium cyanid 97.12 per cent pure were used. Three ounces (fluid) of sulphuric acid and 3 ounces (avoirdu- pois) of potassium cyanid were employed in each experiment, and 3, 6,9, 12, 15, 18, 21, and 24 ounces, respectively, of water were used in the different experiments. 38 FUMIGATION INVESTIGATIONS IN CALIFORNIA. From the following chart it is evident that with the acid and cyanid | mentioned the largest amount of gas is available from two parts of water. As the proportion of water is increased above two parts the avaliable gas is decreased until with eight parts of water we obtain only about 43 per cent of gas, or less than one-half as much as with two parts. In other words, 1 ounce of cyanid and 1 ounce of acid in combination with 2 ounces of water will produce much more avyail- able gas than 2 ounces of cyanid and 2 ounces of acid with 16 ounces of water. The cause for the smaller amount of gas with one part of water than with two parts has already been explained (see p. 35). We can see from the chart that the proportion of water used is one of the most important factors in fumigation practice; and many of PROPORTIONS OF PER CENT OF GAS GIVEN OFF CYAN/D| ACID |\WATER 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Fig. 13.—Chart showing total amount of gas evolved when different proportions of water are used. (Original. ) the poor results in field work can be directly attributed to the use of too much water. That the water should be measured as carefully as the acid is beyond question. Aside from variations in the amount of water used, due to lack of precision in measuring, the proportion of water recommended by dif- ferent authorities on fumigation has varied all the way from two to eight parts. It is no wonder we see widely differing results from the work of different men. It is a common practice with many fumi- eators to increase the dosage when fumigating a tree that is severely infested with scale. It is also a common practice—in fact, so com- mon as to be almost universal—to increase the proportion of water when using heavy dosages. This-is apparently done with a view to preventing injury to the fruit and foliage. In following out this prac- tice the fumigator has many times unconsciously prevented the very result he wished to accomplish—that of obtaining a more concen- trated gas. THE CORRECT PROPORTION OF WATER. The chart (fig. 13) shows that two parts of water to one part Db each of cyanid and acid will produce the maximum amount of avail- MIXING THE CHEMICALS. 39 able gas. It is impracticable, however, to use two parts of water in field work, for with this proportion of water the residue, especially where small dosages of powdered cyanid are used, will frequently con- geal within an hour’s time—the usual period for leaving the tents on the trees. Although this proportion of water is apparently sufficient to dissolve the sulphate at first so that a complete reaction takes place, it appears unable to hold the suiphate in solution long enough afterwards to prevent inconvenience in field work. It is of course evi- dent that a ‘‘frozen”’ generator does not always signify an unsatis- factory generation. With three parts of water, however, the residue seldom congéals, and this is the proportion we have used in all of our field work and which we recommend. The water should be meas- ured carefully with a glass or dipper graduated to ounces. THE MOST ECONOMICAL PROPORTION OF CHEMICALS TO USE IN GENERATING HYDROCYANIC-ACID GAS, In the preceding discussion it has been shown that for various reasons 1 fluid ounce of commercial sulphuric acid and 1 ounce (avoir- _dupois) 96 to 100 per cent potassium cyanid in combination with 3 fluid ounces of water give a complete reaction. Thus the 1-1-3 for- mula, hitherto recommended by the Bureau of Entomology, is fully indorsed. A review of the use of hydrocyanic-acid gas for fumigation, both in California and elsewhere, shows frequent divergence from the more economical and satisfactory proportion of chemicals indicated above. One book recognized as an authority on fumigation methods recom- mends the use of ‘‘one-half more acid than cyanid and one-half more water than acid.” Many of the entomologists and horticulturists in the eastern United States advise in their recommendations for nur- sery fumigation two parts of acid and four parts of water to each part of cyanid. MIXING THE CHEMICALS. It is preferable to pour the water into the generator first and then add the acid. The pouring of the water onto the acid is more likely to cause splashing of the acid from the jar onto the fumigator. When the acid and water are in readiness for generating the gas the fumi- gator adds the pieces of cyanid to the mixture and hastily retreats. As already stated, the cyanid should be added while the mixture of water and acid is hot. The advantage of this is shown in the fol- lowing experiments performed by the Bureau of Chemistry of this Department. One ounce of potassium cyanid, 1 fluid ounce of com- mercial sulphuric acid, and 3 fluid ounces of water were used in each case. : Experiment No. 1.—The potassium cyanid was added to a mixture of acid and water in which the heat was exhausted, and it was found 40 FUMIGATION INVESTIGATIONS IN CALIFORNIA, that 23.25 per cent of hydrocyanic acid remained in solution and was not liberated. Experiment No. 2.—The potassium cyanid was added to a mixture of acid and water when first combined, 1. e., when the heat was great, and it was found that only 10.68 per cent of hydrocyanic acid remained in solution, Caution.—The cyanid should never be placed in the water before the acid is added. If the acid is added to the cyanid in solution, a very violent reaction takes place, which will sometimes throw much of the liquid from the vessel. In one instance about 1 pound of cyanid was dissolved in water in a 2-gallon generator. Acid was then added, producing a disturbance so violent as to throw some of the liquid almost to the top of a two-story barn. A 14-gallon generator will serve for a dose of about 15 ounces of eyanid without boiling over, or a 2-gallon generator for approximately 20 ounces. The residue from the reaction contains more or less sulphuric acid which has not been used. This residue should never be deposited against or at the base of a tree, as it may penetrate to the roots, especially in light sandy soils, destroying a part if not the entire tree. PURPLE SCALE FUMIGATION. PRELIMINARY EXPERIMENTS FOR THE CONTROL OF THE PURPLE SCALE, During the month of November, 1907, experiments were under- taken at Orange, Cal., to determine the dosage required for the destruction of the purple scale (Lepidosaphes beckii Newm.) in all its stages, as well as to determine the effect of exposures of different durations. The orchard under treatment contained orange trees varying from 7 to 14 feet in height. The infestation with the purple scale was very severe on many of the trees. In the first experiment the duration of exposure was thirty minutes. In this experiment a series of tests was made to determine the effect of different dosages. These tests were as follows: One series of trees was dosed at the rate of three-fourths ounce of cyanid per 100 cubic feet of inclosed space; a second series at the rate of 1 ounce, a third at the rate of 14 ounces, and so on, increasing the dosage of each succeeding series at the rate of one-fourth ounce per 100 cubic feet. The largest dosage used was 24 ounces per 100 cubic feet. The second and third experiments were the exact counterparts of the first in all respects except that the duration of the exposures was respectively one hour and one and one-half hours. From the data secured from these experiments it should be pos- sible to determine the killmg dosage for the purple scale for that particular length of time, provided a sufficient strength of gas was reached. To insure that the dosage sought would fall within the FUMIGATION AGAINST THE PURPLE SCALE. 4] scope of the schedule, the limits were made very broad. From the difference in strength of killing dosage between these three experi- ments we would be able to determine the effect of length of exposure on results secured. To obviate as much as possible the leakage of gas, which would vary in trees of different sizes, trees were chosen of as uniform a size as could be obtained. The cubic contents of the trees chosen for the first two experiments did not vary greatly and the trees ranged between 11 and 14 feet in height. As in the first two experiments most of the larger trees had been used, for the third experiment we were compelled to utilize those remaining, which varied somewhat in size, and were also, for the most part, noticeably smaller than those represented in the first two experiments. During the latter part ot January an examination was made of the results of these experiments. Fully two weeks were devoted to this, and thousands of the purple scale were scrutinized. The method employed was a very careful one. In each case the scales were overturned and examined with a powerful hand lens. In those instances in which the entire contents of the scale were not at once revealed, the delicate ventral scale was ruptured and the contents scraped out. Through this method not a single egg could escape observation. Four trees were used in each test and an examination to deter- mine results was made of each. This examination included many infested leaves and branches taken as close to the ground as possible and up to 6 or 7 feet above the ground. Infested fruit was also examined when obtainable. The average condition existing in these four trees was taken to indicate the result of the test. The chemicals were used in the following proportion: Potassium eyanid, 1 part; sulphuric acid, 1 part; water, 3 parts. TaBLE 1V.—Fumigation for the purple scale, experiment No. 1. {Length of exposure, thirty minutes; height of trees, 11 to 14 feet.] On leaves and : } (alias ranichet On fruit. Number per 100 See SAT, if rth | aa %s trees pubic Insects Eggs Insects treated. ae alive, normal, alive, aie any BIN cn s of space. approxi- approxi- approxi- | Eggs normal, approximately. mately. | mately. mately. peeks us = hale ay = = Ounces. | Per cent.| Per cent. Per cent. 4 | 3 5-6 | Over 75. 0 | Fully 90 per cent. 40 1 0 About 75. 2 | Many normal eggs found under every | scale containing eggs. 4) 1} 0 15-20 | 0 | Some normal eggs found under almost | | __every scale containing eggs. 4 | 13) 0 2-3 0 | 15 per cent. 4 | 13 0 | Less than 1. 0 | 5-7 per cent. 4 | 2 0 0 0 | 1 per cent. 40 2} 0 | 0 0 | Two instances of apparently normal eggs. 4 | 23 0 | 0 0 | None. AQ FUMIGATION INVESTIGATIONS IN CALIFORNIA. In this experiment, when three-fourths of an ounce of cyanid per 100 cubic feet of space was used, live adult females were found on the leaves and branches, but the insects were killed by all greater dosages; normal eggs were found after the use of a dosage as high as 1? ounces per 100 cubic feet. Live insects were found on the fruit after both the three-fourths-ounce and 1-ounce tests, but were de- stroyed by the heavier dosages; normal eggs were found on the fruit after dosages up to and including the 2}-ounce rate; with 24 ounces per 100 cubic feet, all were apparently destroyed. This experiment indicates that for normally shaped orange trees, from 11 to 14 feet in height, situated in a region with conditions comparable to those at Orange, and exposed to the gas for thirty minutes, a dosage of about 2 ounces per 100 cubic feet is required for eradication of the purple scale from the leaves and branches. If the trees contain fruit infested with scale, it is necessary to increase the dosage rate to 24 ounces to accomplish the same result. TasBLeE V.—Fumigation for the purple scale, experiment No. 2. {Length of exposure, one hour; height of trees, 11 to 14 feet.] On leaves and branches. On fruit. Number eiae beeen Te f Stance 5 aed paubic eek ates Eggs normal, eae ie eeimonnial SHEE approxi-| approximately. approxi- 488 : mately. mately. Ounces. 4 z 0 1-5 per cent. 0 | Many instances. 4 1 0 1 per cent or less. 0 | Several instances. 4 11 0 2 doubtful cases. (a) (a) 4 14 0 0 0 | One doubtful case. 4 13 0 0 0 | Few instances of normal eggs on one fruit. 4 2 0 0 0 | No instances of normal eggs. 4 24 0 0 (@) (a) 4 2s 0 0 (@) (a) | | a No infested fruit on these trees. With an exposure of one hour all insects were destroyed on the leaves and branches at a three-fourths ounce dosage rate. All eggs were destroyed at the 14-ounce dosage rate. Since very few oranges infested with scale were found on the trees used in this experiment, it is considered that further investigation will be necessary before the effect of different dosages on scale infesting the fruit is definitely known. No live insects were found infesting the small amount of fruit available. Normal eggs were found after a dosage as high as the 12-ounce rate. This experiment would lead to the conclusion that for normally shaped orange trees, from 11 to 14 feet in height, exposed to the gas for one hour, and situated in a region with conditions comparable to those at Orange, a dosage rate of 14 ounces per 100 cubic feet will LEAKAGE OF GAS IN SMALL TREES. 43 destroy the purple scale in all its stages on the leaves and wood. If the tree contain fruit infested with this scale it will be necessary to slightly increase the dosage. The exact amount of this increase can not be stated with accuracy at this time, owing to the fact that in the single experiment performed very little infested fruit from which data might be secured was available. TaBLe VI.—Fumigation for the purple scale, experiment No. 3. [Length of exposure, one and one-half hours; size of trees mostly 7 to 10 feet; occasionally one 11 or 12 feet.) | Coania On leaves and branches. On fruit. Pee per 100 | ies a ee at | rea a > treated. pubic feet’ Insects alive, Eggs normal, Insects alive, | E | Ca SE AUC: approximately. approximately. | approximately. HASSE) Ounces | 4 2 3-5 per cent. 40-50 per cent. | 10-15 per cent. | Above 75 per cent. 4 1 | 1 live female. 20-25 percent. | 1-2 per cent. | 65-75 per cent. 4 13 |} 0 4-5 per cent. | (a) | (2) 4 13 |} 0 1-2 per cent. 0 | Two oranges examined; many normal eggs | | present. 4 13 0 | 3 instances of nor- 0 | A few normal eggs. | maleggs. 4 20 I 0 0 (a) | (a) 4 2a 0 0 (2) (a) 4 24 | 0) 0 (2) (a) a No material for examination. In this experiment live insects were found on the branches and leaves in the cases where three-fourths ounce and 1-ounce dosages were employed. Normal eggs were found up to and including the 13-ounce rate, but were destroyed by dosages exceeding this. As in the case of experiment No. 2, so little scaly fruit was available at that time that we are inclined to consider the results in this part of the test as yet incomplete. THE LEAKAGE OF GAS IN FUMIGATING SMALL TREES. When the results of experiment No. 3 are compared with those of experiment No. 2 we are at first led to believe that an error has been made. In experiment No. 2 it was found that the 14-ounce dosage rate destroyed all insects and eggs on the leaves and branches, whereas in this experiment it required one-half ounce more cyanid per 100 cubic feet, or a 2-ounce dosage rate, to accomplish the same result. Since the period of exposure was thirty minutes longer than that of experiment No. 2, we would naturally expect that the results accom- plished would be as good or better, all other conditions being the same. The apparatus and chemicals employed were identical in both cases; and the conditions under which the fumigation was conducted were practically the same. There was, however, one difference: The trees involved in the one and one-half hour fumigation were much smaller than those of the one-hour test. This fact accounts for the 44 FUMIGATION INVESTIGATIONS IN CALIFORNIA. less satisfactory results in eradicating the scale, in this experiment. We know that a leakage of gas takes place through the tent and that more gas will escape through 2 square feet of cloth than through 1 square foot in a given time. It will be shown in one of the following discussions that the leakage surface of tented trees is proportionately much greater for smaller trees than for larger ones. This would lead us to expect a greater escape of gas and consequently the requirement of a heavier dosage rate with the smaller than with the larger trees. The last experiment demonstrated the correctness of this deduction. THE LENGTH OF EXPOSURE. All considerations were the same in experiments Nos. 1 and 2 ex- cept the length of exposure. In using a 2-ounce dosage rate, we were able to destroy the purple scale in all of its stages on the leaves and branches with a thirty-minute exposure, whereas with a one-hour exposure we were able to accomplish the same results by using a 1}- ounce dosage rate. This demonstrates that decidedly better results can be secured by leaving the tents on the trees one hour than is possible with thirty minutes gassing. Whether more favorable results can be accomplished in one and a half hours than in one hour can not be determined from these experiments, since the trees in »xperiment No. 3 were of a smaller size than those in experiments Nos. 1 and 2. This matter of the large or small size of the trees is a vital factor in affecting the results obtainable. Judging solely from the data at hand, we are forced to the conclu- sion that one hour is the more satisfactory length of exposure. Fur- ther experiments may show that a longer exposure will produce better results, or even that a forty-five or fifty-minute exposure will produce results as satisfactory as are obtainable in one hour. We hope in the near future to be able to fully settle this question. Until this is done, however, it would appear advisable to adhere to the one-hour length of exposure which is now generally employed in southern California. The considerations upon which this conclusion is based are as follows: Experiments have demonstrated conclusively that with an expo- sure of one hour we can obtain decidedly better results than with an exposure of thirty minutes. If we give the tree an exposure of thirty minutes, it will require a considerably larger amount of cyanid to accomplish the same result. It requires approximately one hour for an outfit to go through the complete operation of preparing the chemicals and shifting 30 to 33 tents—the number usually employed. The tent pullers, by the time the end of the row is reached, are usually as much as five minutes, sometimes more, ahead of the one who handles the chemicals. As a result, the last trees of a row are ex- posed to the gas about fifty-five minutes, or a little less, under the DURATION OF EXPOSURE. 45 present system, whereas an hour is supposed to be the length of exposure throughout. Thus if fifty minutes is found to give as satisfactory results as an hour, it would be poor policy to reduce the general exposure to this basis, inasmuch as with a general exposure of one hour some trees are already receiving but little more than fifty minutes. As a rule, very little gas remains under the tent at the expiration of one hour. The amount is usually so small that the mortality among the scale-insects could be but slightly increased by greatly lengthen- ing the exposure. Various authorities have recommended two hours _ or more as the duration of exposure, and it is possible that these long ~ exposures would produce slightly better results than an exposure of one hour. From the standpoint of the fruit grower, who requires the best results at the least possible expense, the item of time is highly impor- tant. The question which must be considered is whether it is more advantageous to sacrifice time or cyanid. No doubt it is cheaper to sacrifice time up to a certain point, but beyond this it is cheaper to sacrifice cyanid. As previously stated, the mortality among scale- insects, when a two-hour exposure is employed, might be slightly greater than at one hour. Before advising a two-hour exposure, however, we must determine whether or not it would be more eco- nomical to employ an exposure of one hour and use sufficient cyanid to accomplish the same results secured by the longer time. Fumigators are usually paid by the hour. Where tents are left on the trees two hours, with the same number of tents the cost for labor is exactly twice that for one hour. From 4 to 6 men, at an average wage of 35 cents per hour, are used on an outfit (infrequently 3), making the hourly cost for labor from $1.40 to $2.10. This would purchase from 5 to 7 pounds of cyanid.* Under these circumstances, if we can obtain as good results in an hour by using 5 to 7 pounds more of cyanid—or a smaller amount, according to the number of men in the outfit—it would be more economical in the end to use the additional cyanid and expose for the shorter time. The writer’s own field experience leads him to believe that as good results can be accom- plished in one hour as in two hours by using an amount of cyanid costing far less than would the extra hour’s labor. It will be seen that the question before the fumigator is not simply one of using that length of exposure which will produce the best results, but that which will at the same time be most economical. From field experience and other considerations the writer is led to believe that this will be between fifty minutes and one and one-half hours. @ Cyanid is here considered as including acid, both costing about 28 cents per pound. 46 FUMIGATION INVESTIGATIONS IN CALIFORNIA. ERADICATION OF THE PURPLE SCALE. The foregoing experiments have shown that the purple scale can be eradicated from citrus trees, provided a dosage of sufficient strength be used with a sufficient exposure. This dosage strength is much greater than that at present used in fumigation. If the purple scale can be everywhere eradicated by using a dosage of definite strength (which we hope to determine in due time), the question will immediately arise in the orchardist’s mind whether it will be profitable to use this heavier dosage provided it can be em- ployed without injury to the tree and fruit. In deciding this ques- tion several practical considerations must be taken into account. The trees, as will be shown later, are in a condition to stand this heavy dosage without injury during but a limited portion of the year. It would be impossible for the number of outfits at present in exist- ence to fumigate the infested area within this limit of time. More- over, unless compelled to do so the orchardists in any locality would not all use this dosage. Whether it would be advisable for a grower to incur the additional expense for this heavier dosage in his orchard when the infested orchards on all sides of him are fumigated with lighter dosages, if at all, must be determined by large-scale tests. The foregoing are some of the difficulties in respect to the use of this heavy dosage. DIFFICULTY OF DESTROYING THE SCALE ON THE FRUIT. There is one more important point which must be considered in connection with fumigation for the purple scale. It will be seen in an examination of the data from the foregoing experiments that an orchardist, fumigating trees containing purple scale in its different stages on the fruit as well as on the leaves and branches, would, except with the heaviest dosages, leave on the fruit healthy eggs soon to hatch and infest other parts of the trees. It would be impractical under most circumstances to use a dosage heavy enough to destroy the eggs on the fruit. The cost of the extra cyanid required, above that necessary for the destruction of the eggs on the leaves and branches, would be more than the scaly fruit is worth. Therefore in fumigating for eradication it is advisable to remove the infested fruit, and it is advisable to remove the old scaly fruit in any fumi- gation. At picking, fruit badly infested with scale is usually left on the tree, and frequently from one to a half dozen or more old, scale-infested oranges per tree remain throughout an orchard. Even after a good fumigation one of these old fruits might carry more healthy purple-scale eggs than all the rest of the tree, and on the hatching of these eggs the insects will spread to other parts of the tree. The danger from old scaly fruit is evident and all such should be removed from the trees before fumigating an orchard. LEAKAGE OF GAS DURING OPERATIONS. 47 GENERAL CONSIDERATIONS. ; LEAKAGE OF GAS DURING OPERATIONS. One of the most important questions relating to the proper dosage in fumigation is that of the leakage of gas through the tent; in fact, the dosage depends directly upon the leakage. To measure with accuracy the amount of gas which escapes through tenting fabrics of various grades during a given length of time, or the rapidity with which the gas within the tent is diluted under different conditions, is a difficult problem. In this work, as far as we have progressed, no attempt has been made to measure directly with instruments the ‘rapidity with which the gas is diluted, but rather to measure it indi- rectly and roughly through determining the effect on insects by using different durations of exposure. The easiest and most practical method of determining the influence of leakage is by fumigating trees of the same size, in which all factors affecting the results are identical with the exception of the length of exposure. There is, however, one consideration of value relative to the leak- age of gas, which it is quite necessary to understand in successfully fumigating an orchard containing trees of a wide range of size. In geometrical figures which approximate in shape a citrus tree, the volume decreases at a more rapid rate than does the surface area. In order to bring out the relation of this fact to orchard fumigation, the followmg table has been prepared: . TaBLE VI1.—Leakage of gas from tents covering trees of different dimensions. Dimensions of tree. Contents 3 | Leakage eae eet or volume ebcer | surface as of tented capper 2 per cent of Around. Over. tree. ; | volume.@ | Feet. | Feet. | Cubre feet. | Square feet.| Per cent. 20. | 12 99 | 85 | 86 30 19 304 205 | 56 40 | 28 1,040 | 420 | 40 SOla 36 2,147. | 6251 4| 31 60 | 44 3,819 | 995 | 26 70 54 | - 6,605 | 1, 445 22 eee souiparisont here and in the discussion which follows is between square feet of surface and cubic Taking the first tree, 20 feet around by 12 feet over, representing a volume of 99 cubic feet and an exposed surface area of 85 square feet, the ratio of leakage surface to volume is 86:100. For each cubic foot of volume within that 20 by 12 tree there is 0.86 square foot of leakage surface in the tent. The tree 40 by 28 feet has 0.4 square foot of leakage surface for each cubic foot in the tent, while a tree 70 by 54 has but 0.22 square foot of leakage surface to each cubic foot within. Suppose that these tented trees were charged with gas and that all the gas were to escape through the tent. In the 48 FUMIGATION INVESTIGATIONS IN CALIFORNIA. first tree, 20 by 12 feet, there would be 0.86 of a square foot of tent surface for each cubic foot of gas to escape through; whereas in the last tree, 70 by 54, there would be only 0.22 of a square foot of tent surface for each cubic foot to escape through. This would mean that there would be about four times as great an opportunity for leakage, or that the leakage would be approximately four times as rapid in the smaller tent as in the larger one. There can be little doubt that the leakage of gas in tents covering different-sized trees is nearly in accordance with these figures. Hence it can be readily seen that, in order to secure uniformity of results, this leakage must be taken into consideration, and small trees must receive more cyanid per 100 cubic feet than do the larger trees. The correctness of the foregoing deduction has been frequently demonstrated in the field. In using on a smaller tree a certain dosage strength with which on large trees we were able to secure splendid results against the purple scale, we were always much less successful. In other words, if we used 1 ounce of cyanid per 100 cubic feet on the 70 by 54 foot tree, we would get far better results than had we used the same dosage rate on the 20 by 12 foot tree. A very forcible exemplification of this condition has been given in experiment No. 3, in fumigating for the purple scale. In this particular experi- -ment much less satisfactory results were secured on the small trees when using a one and one-half hour exposure than on the large trees of experiment No. 2, with a one-hour exposure. TIME OF THE YEAR FOR FUMIGATION. Although fumigation is carried on in California at all times of the year, there are certain periods in which the operations are more general. There are two main factors to be taken into consideration in fumigating, i. e., the species of scale-insect and the condition of the tree. As to he latter, it may be said that at certain periods of the year trees are in such a tender condition that they can not withstand a heavy dosage without injury, especially to the fruit. The bulk of fumigation in California at the present time is carried on between the latter part of August and December. Probably the principal reason for fumigating during this period is that at this time the black scale is most successfully reached. The eggs of the black scale, and the insects themselves when full grown or nearly so (commonly spoken of as in the ‘‘rubber”’ stage), require very heavy dosages. On the other hand, the young of the black scale, or those which have not reached the so-called ‘‘rubber’’ stage, can be destroyed with a moderate dosage. Although the life history of the black scale has never been thoroughly worked out for the region with which we have to do, it is generally understood that the majority TIME OF YEAR FOR FUMIGATION. 49 of the insects of the large and more regular brood are hatched and in their least resistant stage during September and October. In some favorable seasons the eggs are almost all hatched in August. Moderately light fumigation dosage may be used against the black scale during this period with success. The black scale occurs in practically every citrus-growing locality of southern California, while the purple, red, and yellow scales, the other principal citrus pests, are more localized. A heavier dosage is used for the latter insects than for the black scale. Where the other species occur in orchards infested with the black scale, it is a common practice to fumigate during the regular black-scale period, using the heavier dosage. The majority of these scale insects can thus be caught at one time. When fumigating for the purple scale alone, operations may be commenced as early in the season as the trees are in a condition to withstand the heavy dosage without injury, although probably it would be preferable to fumigate a little later in the fall. The purple scale is to be found in the egg stage throughout the year. There is a period in the fall and one in the early spring, however, during which the smallest proportion of eggs is to be found. With dosages lower than those of eradication, the best work can be accomplished at these times. The red and yellow scales are viviparous and can be successfully destroyed throughout the year. In fumigating for any of the scale-insects there is one point worthy of consideration. Aside from trying to save the tree from destruction or from having its vitality impaired by the attack of seale pests, the orchardist fumigates principally in order to have his fruit come into the packing house as clean as possible. It would be well, therefore, to fumigate as nearly as possible to the time which would insure him the cleanest fruit. Although lemons are gathered throughout the entire year, the bulk of the orange crop is taken during the first six months. Thus fumigation during the fall and early winter would be sure to place the cleanest fruit in the packing house. If carried on in the late spring or early summer, such insects as remain undestroyed would have the opportunity to breed through a period of several months and infest much fruit. FUMIGATION DURING THE BLOSSOMING PERIOD. The statements by experts on fumigation as to the amount of injury resulting from work while the trees are in blossom are very conflicting. Some fumigators hold that a very light dosage will destroy the tender blossoms, while others believe that the blossoms will stand a heavy dosage. In order to decide this point much experi- mentation was carried on and many observations made throughout 77488—Bul. 79—09—14 50 FUMIGATION INVESTIGATIONS IN CALIFORNIA. the blossoming period of 1908. Some of the results secured are given in the following paragraphs. Experiment No. 1.—On February 28 and 29 about one-third of an acre of mixed Valencia and Navel orange trees was fumigated at Upland, Cal., using dosage rates of 1 ounce and 14 ounces per 100 cubic feet. The trees. were about 12 feet in height. At this time the blossoms were just appearing on the trees, none of them being far enough advanced to open. The general conditions of the blos- soming may be understood by an examination of figure 14. This Fig. 14.—Orange blossoms at an early stage of development. (Original.) may be considered the tenderest stage of blossoming. An examina- tion of these trees two weeks later showed that no apparent jury had resulted and that the trees at this time contained as heavy :z set of blossoms as the surrounding unfumigated trees. Experiment No. 2.—On March 30 fully 1 acre of Navel and Valencia orange trees about 10 feet high were fumigated at Orange, Cal., using dosage rates of 1, 14, and 2 ounces per 100 cubic feet. The condition of blossoming at the time of fumigation ranged from no open blos- soms on some trees to full blossoms on others. An examination of these trees at a later date showed that with the 1 and 14 dosage rates no apparent injury had been done. The 2-ounce rate had caused FUMIGATION WHILE FRUIT IS SMALL. 51 a considerable percentage of the blossoms to drop, yet not enough to lessen the coming crop of fruit to any great extent, if at all. Experiment No. 35—During the months of April and May, 25 acres of Valencia and Navel oranges at Glendale, Cal., were fumigated by an expert under the direction ef the Los Angeles horticultural com- mission. While this fumigation was in progress, trees could be found in all stages of blossoming, from those with blossoms just appearing to those in full bloom. The dosage rate used was esti- mated to be from three-fourths to 1 ounce per 100 cubic feet. Of course this rate varied with different trees, since the dosage was estimated after the usual guesswork method. Several examinations of the orchard were made. A/though blossoms were injured on some of the trees, the number was so small as in no way to lessen the future crop of fruit. Other instances might be mentioned, but the results correspond practically with those in the three experiments already described. Trees in which there were blossom-shoots and tender leaf-shoots side by side would have the leaf-shoots burned back while the blos- soms remained uninjured. Also numbers of cases could be found where the tender leaves on the blossom-shoots were burned while the blossoms themselves remained uninjured. This, as well as the heavy dosage which the blossoms will stand without injury, would lead us to conclude that the blossoms will stand a heavier dosage than the tender leaves and leaf-shoots. These experiments also show that fumigation can be safely conducted during the blossoming season, using such dosages as are at present generally employed by fumigators, or are advised in dosage schedule 1 (p. 65). FUMIGATION WHILE THE FRUIT IS OF SMALL SIZE. Experiments and observations to determine the effect of fumiga- tion on fruits of various sizes, and more especially on small fruits, were made during the season of 1908. Conflicting opinions on this subject are prevalent. Experiment No. 1.—On June 16 two Valencia orange trees about 8 feet in height, in a healthy condition, and containing young fruit from three-eighths to one-half inch in diameter, were fumigated at the 2-ounce dosage rate. Fully 25 per cent of the fruits on these trees were pitted or burned. Experiment No. 2.—On June 24 a somewhat unhealthy Navel orange tree about 12 feet in height, with the fruits about one-half inch in diameter, was dosed at the rate of 14 ounces. Fully 50 per cent of the fruits were pitted. Two healthy Valencia orange trees about 10 feet in height, with fruits practically the same size as in the case of the Navel tree, received a dosage at the rate of 2 ounces. About 40 per cent of the fruits were burned. 52 FUMIGATION INVESTIGATIONS IN CALIFORNIA. Experiment No, 3.—On July 11 and 13, four Valencia orange trees were fumigated, using a 1}-ounce dosage rate, 4 trees receiving a 14-ounce dosage, 8 trees a 1?-ounce dosage, and 4 trees a 2-ounce dosage. These trees were in a perfectly normal condition, about 7 to 8 feet high, and contained young fruits fully three-fourths of an inch in diameter. With the 14-ounce dosage rate no fruit was burned; with the 14-ounce rate an occasional! orange was slightly burned; with the 12-ounce rate a very small percentage was burned, while with the 2-ounce rate a considerable percentage was injured. This demonstrates that a 2-ounce dosage rate could not be safely used on trees of this size. Experiment No. 4.—During the middle of July a large number of orange trees of all sizes were fumigated at Santa Fe Springs, Cal., using various dosage rates. The trees fumigated were of several varieties, in a healthy condition, and all well filled with fruits about the size of an English walnut and slightly larger. It was found from this experiment that a dosage rate of 1 ounce to 100 cubic feet could at this time be used without injury on orange trees 15 to 16 feet high. Only an occasiona! orange was burned by 1} ounces. Smaller trees proved able to stand a heavier dosage than larger ones without appreciable injury. On the basis of information obtained from experiment No. 4, dosage schedule 1 (p. 65) was prepared. This schedule was put into use during the latter part of July and has been in use, up to the time of writing, by two outfits, at Whittier, Cal. Although no noticeable injury to the fruit has resulted from the use of this dosage, the general effect on the tree has indicated that a heavier dosage could not have been used wich safety. A further example of the tender nature of small fruits was shown in some work done by an excellent fumigator at Downey, Cal., during the latter part of May. The fruits were for the most part three- eighths of an inch or Jess in size, while the trees were thoroughly infested with scale and in a generally unhealthy condition. So far as could be determined, a dosage rate of approximately three-fourths to 1 ounce was used. The larger percentage of the fruits on these trees was burned. Other instances of like fumigation, where the fruits were one-fourth inch or less in diameter, have been seen. The fruit at this period is very tender. Doubtless it is the most critical period of any during which fumigation is conducted. — From the foregoing, it is evident that heavy dosage can not be used while the fruits are small without more or less injury, and that the most critical period during which fumigation may be conducted is between the time when the fruits are set and the time when they attain the size of a walnut. HANDLING THE ACID. 53 SIMPLE METHOD OF REMOVING ACID FROM DRUMS AND CARBOYS. The writer has at times been obliged to employ rather awkward methods in drawing acid from drums and carboys, and other fumi- gators have doubtless met with the same trouble under like circum- stances. Brief mention will be made of some of the best methods which have been brought to notice to obviate this difficulty. From drums.—The best method of taking’ acid from drums known to the writer is that at present in use in San Bernardino County and is shown in figure 15. The apparatus consists of a lead-lined tank large enough to hold a drum of acid and having an outlet through Fic. 15.—Lead-lined tank used in San Bernardino County for removing sulphuric acid from drums and for filling jugs. (Original.) which the acid may be drawn into carboys, jugs, or whatever vessels are preferred for field use. A drum of acid is rolled from the wagon upon two parallel beams and along these beams onto a small turn- table at the tank. This turntable is then revolved through a quarter circle, permitting the drum to be rolled out over the lead-lined tank, into which the acid is then allowed to flow. The acid may be drawn as previously mentioned. The outlet is made of lead tubing, fitted at the tank end with a lead valve by which the flow is regulated. Another very satisfactory way of drawing acid from drums came to the writer’s attention in examining some operations at Glendale, Cal. It consists in the use of a short iron pipe threaded at one end 54 FUMIGATION INVESTIGATIONS IN CALIFORNIA. so as to fit the opening in the drum. The one difficulty with this device is that the flow of acid is uneven and spouting. To offset this, Mr. William Wood, of Whittier, Cal., has contrived a small copper tube for attachment to the pipe, one end of the tube being ex- posed to the open air, the other end extending up above the level of the acid within the drum, thus allowing an uninterrupted flow of air into the latter. This apparatus is illustrated in figure 16. A third method in use is to transfer the drums from the wagon to a platform 2 or 3 feet high. The acid may then be removed very easily by means of a piece of rubber hose employed as a siphon (fig. 17). Fic. 16.—An improved pipe for removing acid from drums. (Original.) AY BIN Fig. 17.—Siphoning acid from drums by means of a rubber hose. (Original.) From carboys—Two common methods used for removing acid from carboys in the field are shown in figures 18 and 19. In the first method a small amount of dirt is placed against one side of the car- THE MARKING OF TENTS. 5D boy, furnishing a sort of rest when the latter is tipped to remove the acid. It is well to scoop out a small pit below this ridge of dirt, into which the vessel receiving the acid may be lowered when the acid is so largely removed that it is necessary to turn the carboy far on its side in order that all may be withdrawn. In figure 19 the handles on the carboy are substitutes for the heap of dirt and the pit. They are also of service in carrying the carboy. THE PROTECTION OF CYANID. Many fumigators do not attempt to cover their cases of cyanid, but leave them open during the day. This not only constitutes a source of danger to various animals, but also during the wet season allows water to reach the cyanid. Fig- ure 20 shows a simple lid covered with zinc . which is suitable for placing on a cyanid _ case to protect its con- tents. HYDROCYANIC-ACID GAS IN DRUMS. Some discussion has arisen during the past year relative to the rie. 18.—Carboy resting against a heap of dirt to facilitate pouring possibility of introduc- pbeweds KONE) ing hydrocyanic-acid gas into drums under pressure, and using it directly from the drums, thus doing away with all generation in the field. The use of this gas under pressure from drums is impossible at the present time for two reasons: (1) No drums are made which will hold hydrocyanic-acid gas without corroding; (2) we know of no instrument which will measure gas accurately under varying degrees of pressure, such as would exist in removing a gas under pressure from drums. THE MARKING OF TENTS. Before new tents are marked they should have been in use for a short time, so that they will be thoroughly shrunken. This shrinking 56 FUMIGATION INVESTIGATIONS IN CALIFORNIA. may be accomplished, in regions of heavy dews or fogs, by simply leaving the tents exposed in the open for a few days. Dipping in water or sprinkling by means of a hose and then allowing the tent to dry in the sunshine will an- swer the same purpose if repeated several times. The shrinkage of a new 45-foot tent will some- times be as much as 3 feet. Tents marked be- fore being shrunk will have erroneous gradu- ations. The most satisfactory material to use in mark- ing tents is diluted printer’s ink. This ink is commonly used in Cal- ifornia in marking walnut bags. If the ink is too thick to mark freely, it may be diluted with kero- sene. Printer’s ink does not cause the cloth to de- teriorate. A mixture of lampblack and turpentine may also be used with entire safety. The latter, however, will sometimes rub off to a slight extent. Fig. 19.—Carboy with handles attached to facilitate pouring the acid and carrying the carboy. (Original.) A DEVICE FOR COVERING FUMIGATION GENERATORS. During the course of this investigation much effort has been directed toward perfecting a device for attachment to the top of the commonly used open-style fumigation generator that will serve to interrupt the direct rise of the hydrocyanic-acid gas. The result of these efforts, in which the writer was greatly aided by Mr. Frederick Maskew, is shown in figure 21. The device itself consists of a copper cover of such size as to make it available for use with any of the regular-pattern generators now employed by the fumigators of southern California. It is stamped in a concave form from a sheet of copper, with corrugations to permit the escape of gas. The shape is such as to conform to the size of the opening of generators of dif- ferent capacities and also to direct the course of the escaping gas downward and distribute it uniformly through the lower part of the, A COVER FOR FUMIGATION GENERATORS. Site tent. It is attached to the generator by hinges of stout copper wire secured by a key bolt passing through the handle. The cover is raised by a slight pressure of the thumb on a projecting piece which is curved in such a manner that the cover will remain in an upright position when so required. When the generator is emptied of its contents, the cover swings clear by its own weight. . 322. 5. ee 55 leakage during operations........----.....+-<- 47-48 in small trees: c. Ti.c fo ee 43-44 temperature as affected by different proportions OL Waker. ae Acs ee 30-36 where large and small dosages are Used 26552. SU aSh eee ee See 36-37 improved systema. 2 252.55. eee perc eae 58-68 advantages 2.2.45 =< <.5c. eee en OOO apparatus..¢ 22.25. -2-c%-.cc ee eae Oe dosage schedule............-....- 64-67 THYUSE.2 Site Sees le ee 67-68 procedure: oe 20ic et 61-63 Supply Cartsecs= 4b eee eee eee 59-62 method of computing dosage and volume for tented 122): a PIE ee ear At he ae Sa. 25-26 methods for obtaining measurements and dosage of trees with and without apparatus........-......- 26-30 procedure in improved system.........:-..-------- 61-63 present. system’. 423 se tes eae 18-19 proportion of materials used by fumigators.......-- 32-39 simplification by improved system.........--.----- 68 sulphuric acid, amount necessary.....-.-.-..------ 32-34 effect of too great am excess.....-..- 34 jamand: cover: s.2-0.29 0 eee eee 60-61 removal from drums and carboys... 53-55 supply cart: S25. sti ee ee eee er 59-61 table to replace supply cart on rough ground.....-. 61, 62 tents, marking. 7.2.05) ee ee eee 27-30, 55-56 shee tear eee is Oe SO Sel. ri 17-18 time of: yeahs ese Be ae ees ee 48-52 tray for carrying chemicals in present system .....- 18-19 Water ‘as alachores pace gd a ee eee ea Yo oL a 84san Correct Proportion. e212 yee ee oe a 38-39 effect of different proportions on amount and temperature of available gas.......-.--.---- 35-38 while fruit is smalli¢- 2) aoe ee eee ee 51-52 methods.of.control in California :~ 37-2234 2 5" eee ee Seo eee 16-17 Mauner OrceediNe ss. s46.<2.5.. 2. ss Sa ee i4 |S} 0] 0121-42119 (0) ene ee RL Se Se ek 16 Spider; citrus red; distributionin California .\.. ... 2 2.2eeeeeses 2a eee 14 enéniy of eltrus trmite5:2 6 eee SL ee ee 11 sulphurspray as tTemedy ....-.-..2.0 seer eee ee eee 16 Spray, kerosene-water, against citrus scales..-:-..... 22. 22@l acc ce eeee esse se 7; Sprays, distillate, aoainst citrus scales. 22 202 35. 5.2 ee 17 sulphursagainst/etirus Seales sii i522 20 oo Aa eee ee eee 16 Sulphuric acid for fumigation, amount necessary........-....--------------- 32-34 effect of too great an excess........----- Be ee 34 jarand cover 2... oo: S Sc ae eee eee 60-61 INDEX. ies Page Sulphuric acid for fumigation, purity required...............--------------- 30-32 removal from carboys and drums..............- 53-55 Sulphur sprays, against red spider and silver. mite of lemon ..............-..-- 16 PLU CANL Lor eg Om tOM as aap cotta ses olmree cee ieee eer Bele SG 59-61 Table to replace supply cart in fumigating on rough ground......-.......-.-- 61, 62 Tents, marking for estimating dosage..........-.-.-2--- Pa RA oe 27-30, 55-56 Tetranychus mytilaspidis. (See Spider, citrus red.) SRIAE ORs CHUAN ORCINUS TRUM S soc os Se soe. . SE ees canes eo eae eens 11 Toxic effect on citrus trees apparently produced by red, purple, and yellow Sees ie eerie tae Se) ee et Rea ah. alan eee oo Ya ole Se oleae 16 Tray for carrying chemicals in present system of fumigation.................. 18-19 NeemmrioreeLOr MN TUMMpAiON=ots: .. 28. Seo es ot kel 34-35 MeO eAAOM s: COLPECT PLOPOLWONG. =. oo... ote C oe Pore cite reed 38-39 effect of different proportions on amount and tempera- bure of available; pase wes. 4 i058 se Pe cis 35-38 Woodworth systems of measuring trees with and without apparatus............ 26-27 O ft 3 7 Ate yi ioeren wr ly y | i A wr iJ] eo Vwyrv ~~ aw we... oe t dyeoted Sudettunysyee | WET purvedevnde” ey V¥yser ANS We tet “yy uv ly ty Ww v PAPAS CAT AS tet vv pags heheh Abd dace TO vy wth My) Jia “Set TN ay PASAT te ee TET yyy VICES ld ht dead Wire Seen mt ww v hE AT ch dts Bysshe Se Jw prt OC dd uibenrecens veh: “ae ~ vy ad . ww i v oN anlaggdett ee ca: vowed eng oy = vive wore sue Vile. i ~ Ww —f Ye verre db ped Vv ¢ aces “pe de : : ; | g W WZ heel hed ~S lee J Viste yew “oven NWW ted eel US Se yee OES, ov¥ : tJ oy) CCUy Pah Sy Le eee | ‘wae y y | vate dae uc " Witenes vooreae” ~ ever ie Mlivave StSES ey i yovanere alla oe hi rw “ves eeuuy v Veweyy ved ‘ : ye" w Sd hd Te Ae) ws wwe Ver eLe < sisi hinaed i seen Wore Wee ye dy wus wry siete Doeeeree ey eee” e vow “Sige ere te es ced Oe “Weysele LIM AL Mtb wy tt ee oywuda¥ NM ne bo <30b0 bie SI : ew oa" v i = SMITHSONIAN INSTITUTION LIBRARIES wii iC 7522