Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. MG F OSGaR No. a ae My <2 o at fe al. Ss > 2) ©, HOWARD, tomo and Chi of Bureau . | ap bint \ Mie ea ae ;: ss - * ak: HIBERNATION OF THE MEXICAN | — COTTON BOLL WEEVIL. ee = BY Ww: E.. HINDS-anp- W.’ W. YOTHERS i | : ! UNDER THE DIRECTION OF W.D. HUNTER. IssuED OctoBER 18, 1909. : . H ; 1a * WASHINGTON: ; GOVERNMENT PRINTING OFFICE. 1909. 2 rh ene Gee ea Shee eae | Sia a His © atin Bott on Sig On Ae of Oe Sie IIRRO eae M Lnee OR. 8. Curron, Executive Assistant. sa Sas eee Rene Pee eeu eee : a Ue See as “3 : he, Ee = ates Ie er Ade CHITTENDEN, in chargé of truck crop and stored product insect oop OPKINS, in charge of forest insect investigations. _ Say HUNTER, in charge of southern field crop insect investigations. te = SF "EBSTER, in charge of cereal and forage insect investigations. os ae sus F ee os AUnP Nab s HBO el eae eg ae Quarntance, 7 an charge of deciduous Sruit: insect investigations. Fae 7a re i. F. RHIiups, in charge of bee culture. Stes So a Pee . _D.M. Rocers, in charge of gipsy moth field work. NaS ON PES ab ge _W. F. Fiske, in charge of gipsy moth laboratory. - Tease Ut als ae ot pene = S. WouLun, in charge of hydrocyanic acid gs investigations. PEO ee ae _R. P. Currte, in charge of editorial work. eee ee eT | Mase Coxcorp, Wbrarians Se Oe ee oe t= Sovrmens ‘Prey nor seer INvEsmiGations, ee ates ae i - tay he trig cng Shae “WD. Hunter, Gechaige BOM Fo é ow. D. Prerce, R. A. CUSHMAN, CG. ‘EL. Hoop, E. =B. ‘TueKer, engaged i in cotton toll ae nee : “weevil investigations. e ed IEC. BIsHOPP, J D. Mone, H P. Woon, engaged in cattle tick life history investi- | =~ gations. ~ : oe AC. Monean, G. rs Se eee vauaete im ‘ebaicks treoet investigations. 3 ee: Ee aS ~D. L. VAN Dine, engaged in sugar cane and rice insect investigations. = Spar Bt a EAU -Prart, engaged in cactus insect ‘investigations. oe ee eee $3 2 "eOneasieaton of the bureau on September 1, 1909. ~ p ; . eee. as =n -: f eres ~ < 5 : = : *s his fe) < "7 af > = ei Se Pe “ ; “ Cons ee x7 > 28 — a EX gnke — eo. VEPARTMENT OF AGRICULTURE, BUREAU OF ENTOMOLOGY—BULLETIN NO. 77. L. O. HOWARD, Entomologist and Chief of Bureau. HIBERNATION OF THE MEXICAN COTTON BOLL WHEVIL. BY W. EH. HINDS ann W. W. YOTHERS, UNDER THE DIRECTION OF Wi. De HUNTER. IssuepD OcTroBER 18, 1909. Se ie: = {= : 4 = = eg Avis Hii \ TAL > OSA" = »> , oO WASHINGTON: GOVERNMENT PRINTING OFFICE, L909, — oe J 4 LETTER OF TRANSMITTAL. U.S. DEPARTMENT OF AGRICULTURE, BurREAU OF ENTOMOLOGY, Washington, D. C., October 6, 1908. Sm: I have the honor to transmit herewith for publication as Bulletin No. 77, of the Bureau of Entomology, a manuscript prepared by Dr. W. E. Hinds and Mr: W. W. Yothers under the direction of Mr. W. D. Hunter. This manuscript deals with the hibernation of the Mexican cotton boll weevil. The winter season is a critical period in the life history of this very destructive pest. An exact knowledge of its hibernation throws much light on practical control. For this reason careful experimental studies have been carried on for several years. On account of their importance the results are pre- sented somewhat in detail. The illustrations will add greatly to the clearness and force of the text. Respectfully, L. O. Howarp, Entomologist and Chief of Bureau. Hon. JAMES WILSON, Secretary of Agriculture. 2 7 Entrance GEST IIS tells elle ae i fae a ee ea ‘Supply of weevils to enter hibernation. . ERA pega area A IEE ETN CE GION Songs oe win ee nee ee ee ee Time of entering hibernation. . ennai PES ee eee Proportion of each sex among w reevila 3 in fail Meee etre | tae ic Se eats oie Se Number of adult weevils entering hibernation..................-.------- Temperature conditions producing hibernation......................---- ISS ILCTRUTOR 1 oo) del ea ela ie ew i ie ee ee eee SoS ld ee Ra BaF Be OE Re Hibernation shelter other than bolls within the field. . Hibernation shelter outside of cotton fields...................2-2..-.-..-- Smmpernation experiments in small cages._.......-......--.----------------+-- STEEL SILLS 28 SS = a ERENCE! LES SOE a Fg IS A ON Ee GT Sy TO eg — Hibernation experiments in small cages, 1905-6...........--..----.------ meamure-cape experiments, Keatchie, La., 1905-6 ..........-....-.--..-----.--- Reeemereunaitions tor hibernation.....-2---.------------------++----- Effect of acclimatization upon survival and emergence.....-..-.----..---- Relation of emergence to effective temperatures...............---------- Relation of time of entrance into hibernation to survival and emergence. . The relationship of accumulated effective temperature to emergence. ...-- Longevity of weevils after emergence in Keatchie experiments. ........--- peree-care expermients Dallas, Tex., 1905-6 ...............-+--.----+-------- Nature of weevil activity following emergence from hibernation. .......-- a Climatic conditions producing emergence from hibernation at Dallas, Tex., @merzence in tne field at Victoria, Tex., in 1906..-.........-..--..-..--...- 7 Large-cage experiments, 1906-7, Dallas, Calvert, and Victoria, Tex....-.....-.. + Se TT a aR Climatic conditions producing hibernation and activity of weevils during SEPMNELEITOUNDGTION | v2 - 2 os see ek ee ee ee eee ene ra EMER COOMMION f. 9-2 sn nk ie ee 2 be eee ee te . Activity during normal period of hibernation...................-.------- ay a fe ae Activity as shown by development during normal hibernation period. . Activity in the field during normal hibernation period...................- EEEEIEOML MIDCERSMON, LOOT «6.25. 22-2 eee oe ewe eee ee eee Relationship of emergence from hibernation to climatic conditions........ Effect of time of entering hibernation and nature of shelter upon the per- RM eRe as. Sete a RS aaa ns wan x52 aod Hea ee swale Se ae Survival of weevils by localities and cage sections. .....................-- Monthly summary of emergence records................-.2--22222--20--- SEE FS SC oe a pees of unfed weevils after emergence e from Giberaad, Longevity of fed weevils after emergence from hibernation..............., Bearing of observations on fed and unfed weevils on the possibility of avoid-_ ing damage to cotton by late planting........--.---------------------- 9 Sex of weevils surviving hibernation. 7: 2:02 22-5 caeneee ees eee 91 Secondary sexual characters....- 4.1. -2y.22 esses genet ee Proportion of sexes surviving hibernation.....--------------------------- i Relation of hibernated weevils to food supply....-.--.-------------------- 98a Summary and conclusions: 202 22-- secre es ee ee Selo Sone 95 Prats I. ON IIL. IV. We VI. VII. VIII. IX. ILLUSTRATIONS. 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- C2 SAE ICON ea \C7o8 IS ale a AO ON Sea OE ent Oe Favorable shelter conditions in and around fields. Fig. 1.—Cotton field adjoining grove of trees laden with Spanish moss ( T%/landsia 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- pM MSO aie os Par ce Nei ce icles ee noo oe le eat 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 1 ...............-------- 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 EE tal IT IEE pele OY 2 0 ee 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 RE MRNA EU lame moc en eee ot ow oc ee ot Sots ee Sk eh ws deere 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 percent. 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 Exceptionally favorable conditions and boll experiment. Fig. 1.— Section 10, a, bolls exposed on surface; 6b, 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 Pere RIVA Vl oO.0o PEP CONL sy. 522 4 eae oodles oot enue e- Page. 30 30 38 50 50 56 64 74 74 6 Fia. 1 2, 3 ie ay HIBERNATION OF THE COTTON BOLL WEEVIL. TEXT FIGURES. . Chart showing mean average temperature, rainfall, and weevil emer- gence, Keatchie, La., March to June, 1906-, -- 22-0 cee e cree eee . Chart showing mean average temperature, rainfall, and weevil emer- gence, Dallas, ‘Tex., March to May, 1006... --- 2-5 ase e oe ee eee . Chart showing mean average temperature, rainfall, and weevil activity, Dallas, Tex.; ‘October; 1906; todfanch, 190722 oe ene . Chart showing mean average temperature, rainfall, and weevil activity, — Calvert, Tex.; October, 1906. to March’ 1907. -So7 so ese ee eee . Chart showing mean average temperature, rainfall, and weevil activity, Victoria, Tex., October, 1906; to March, 1907-222 eee . Chart showing mean average temperature, rainfall, and emergence from hibernation, Dallas, Tex:, Mareh-to June, 190 7222-2 35 oe eee eee . Chart showing mean average temperature, rainfall, and weevil emer- gence, Calvert, Tex., March to June, 1907. 23 sean eee . Chart showing mean average temperature, rainfall, and weevil emer- gence; Victoria, “lex., Maren to Jume, 1907-2 2-- 2.25 eae eee ee . Secondary sexual characters of Anthonomus grandis....-..-..--------- v ‘ Peer AC i: 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 spring. In 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. 8 HIBERNATION OF THE COTTON BOLL WEEVIL. Foremost among the pomts of immediate practical application shown in this bulletin is the enormous importance of the fall destruc- 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 into condensed form. PREFACE. 8) 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 y 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 during 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 11 — ee re 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 bemg 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 defohated 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. 1 er | St | OF | FE | 8S | SZ | LF | LE | OF | ZF | FE | 09 | GF | FF | 9E | 9E | 98 | TE | OF | OF | tien ip Cnet ie 7 S| ed aS Se ae tee |e at ff ff PR OR CIC pe ae eee @ OEYqI Oye PNONE eee ae in *xOy, ‘Tota, |-- | A 08 | #2 | 08 | #9 | #2 / ZZ | #8 | G8 | 08 | 89 | TZ] 92/28 | SF | 6Z | 22 | ZL] OL | Lo | TS | es q 3 pegs Nextag e : Ege | ze | se | ee | se! zo | ob | cr | a | oe | 9¢ | ze | ze | oF | zo | og = ea Ge Se | ae | 2 | ot EIGIONY ODO FSIGE OSES TIEN CI FATALE IOS Cia hoes iat pice ()O—GTme\ O Nii | eta ate ne ie ames "XO, ‘BIIOJOIA |-- '% #9 | 69 | 89 | 99 | 89 | 69 | OL | G9 | 89 | 99 | ZO | 6G | BF | 9g | 98 | 98 x ete a ch a ; fe] See Ze | $8 | Gr | Fo | FF | GF | FF | OOF | BZ | «22: OF | L¢ a BP Mn ee” (ey lieice || oem | eee te Saas ae eee ch See ee Ba? = 3 SS) ee la eee ee cheat eek CZ-GT *AO XO ‘W0I}B1S aZo][0;F 9 19 | 09 | 99 | ZL | #2 | 89 | 6G | TS | SF | Se | OZ | €8 | g8 _ eageittan 2) || iu) ee Pe | YE Ty SS a pe Vf) a (a (a F OF | 66 | 8% | LZ | 9G | GS | FS | ES | GS | Te | OZ | GT | ST | ZT | OL | ST | FL | ST | cL | TL | OT | 6 ‘HOTJVUIOdIY, SUlI9JU0 JO Pollo *AU[VIO'T "IVOK —J0q ULaAON, a , ‘saunpoiod uw} fipop pun uoynusagry 072 aouns}Ua fo aU Uaanjag UOYD]IAY— A AIAVY, "XO, ‘BIIOJOL\ IO] Sp10deI JoqUTeDa(T {OIOND 10} Sp10IEI IAQ UIBAON 9 “Sp10del “XO, ‘VURIISION q ‘sp1oo01 “xa, ‘o1eNnd o { bees ee eee eee eee eee eee TZLOOGIRG2AONT | iS ce SOT SOOT AN eee wre soo eer oa SuJdWaGie SON Is ie 7 mies eg eo t onal SO, SSBTTOT weet eee tence eee eee eee ST 08-08 "AOND [777° art too scree, “epIOJOTA i Neh Sa a og BR OU=hc COON thou | eS ose oh, ed SELECT veneer eee ete e cere ress § “O8C-Il “AON, |-"7 "777777 o “KOL, “BEIOROTA Siok ts Re rea eee gg pare eet G-DeG=np AON raises ba. Ss. QL, Ome, ‘MOT]VUId TY SUl1e} U0 JO pore 24 HIBERNATION OF THE COTTON BOLL WEEVIL. This table serves to show in a graphic way the extent of the period of entrance into hibernation, the varying duration of the period for the same locality in different seasons, and the generally later date of entrance in southern localities as compared with more northern localities in the same season. It also shows the duration of the period as compared with the mean average temperature prevailing. In general it appears that the greater the drop in temperature the shorter will be the period of entrance into hibernation. TasBLe VI.—Periods of entrance into hibernation, and temperatures. | Period. Temperature. Year. | Locality. F Mean | 4 | Limits. Days average. Effective.a 1903..-.| College Station, Tex.......-..-..-.------cs-2- Nov. 15-27. .._.- 13 49.5 6.5 1903....) V ictoria, PO a ERROR yas a he ae ee ee Nov. 15-30_....- 16 53.0 10.0 19942 2% 41 | Corsicana, sl Nc). dN a eon Oe Ree eed ied Nov. 10—Dee. 5 26 55.0 12.0 1904. Victoria, jhe en EE A RN TREE RNS 2 Nov. 11-Dec. 8 28 57.5 14.5 1905....| Dallas, Pests. = Bisa ee cae te ame Nov. 29-Dee. 8.. 10 40.5 None. 1905. . 25) Victoria, Mex oa ees ee ee ee oe Nov. 30-Dece. 18. 19 50.0 7.0 1906 eel Dallas, Tex RS AE ism 2 LAS BON Ie eons et Nov. 12-Dee. 8... 27 53.0 10.0 1906... . _ Victoria, OK eee St oa See en ea Nov. 9-Dee. 21... 43 60. 4 17.4 aIn studying the relationship of temperature conditions to weevil activity the term ‘‘effective tem- perature”’ is used to designate the excess of temperature above 43 degrees F. It has been estimated that 43 degrees marks approximately the beginning of activity with most animals, and experiments have shown that this is equally true of the boll weevil. Below this temperature the weevils are usually inactive. Above it they may move, feed, and reproduce with increasing rapidity as the temperature increases. From this explanation it may be readily understood that the column showing the decrease of efiective tem- perature is really the most significant in connection with the inactivity or hibernation of the weevil. It is undoubtedly true that minimum temperatures have a special influence in checking the activity of the weevil in spite of the fact that they may be below 43 degrees F. When the temperature falls to 32 degrees or lower the food supply of the weevils is usually rather completely destroyed, and this fact may serve to discourage subsequent activity on the part of the weevils, even though the temperature conditions might otherwise favor it. From this table it may be seen that the shortest period of entrance into hibernation of which we have record is ten days. This occurred at Dallas, when the mean average temperature was 9 degrees lower than that for any other period iia has been studied. In regard to the limits assigned to the period for Victoria in 1906 it may be stated that iver was probably only partial at that place at any time during the winter of 1906-7. The limits of the period that have been given are based on field notes made about the middle of November indicating the beginning of the period, and temperature records covering the coldest period that occurred during December. The mean average temperature during November for Vic- toria was 60.4 degrees, the range being from an absolute minimum of 27 degrees to an absolute maximum of 84 degrees. The temperature | ee -e 4 3" SHELTER DURING HIBERNATION. 25 fell below 32 degrees only once during this month. From December 1 to 21 the mean average temperature wes also 60.4 degrees. In this case the range of temperature varies from an absolute maximum of 83 degrees to an absolute minimum of 82 degrees, the latter occur- ring only once. From these records it is apparent that the climatic conditions were not sufficiently severe either to destroy absolutely the food supply of the weevils or to insure the continued inactivity of those which may have sought shelter during the short periods of cool weather. Sprout cotton was exceptionally abundant throughout the winter and weevils were found feeding upon it almost continuously. From these facts we may be justified in concluding that a mean average temperature of 60 degrees is too high for the complete hiberna- tion of the weevil; that hibernation usually takes place coincidently with the decrease in mean average temperature to about 55 degrees; and that it remains complete until the mean average temperature subsequently rises to above 60 degrees. SHELTER DURING HIBERNATION. While many weevils seek hibernation shelter outside the field it is certain that a considerable number of them remain very near their food supply—that is, in the cotton fields and in the immediate vicinity. Because of the differences in the nature of the weevil shelter and in the possibility of destroying or removing such favorable shelter, within and without the cotton fields, these two conditions will be considered separately. SHELTER IN BOLLS. Within the cotton fields weevils are sheltered primarily in the hanging cotton bolls, the fallen foliage, and grass or other rubbish which may have accumulated upon the surface of the ground. Attention has already been called to the fact that many stages enter the period of hibernation in an immature condition in unopened bolls. (See p. 14.) That many adult weevils hibernate entirely within the protection afforded by the bracts and hulls of bolls has been abundantly demonstrated (PI. II, fig. 3). Rather extensive experiments have been made upon this point in a number of localities during several seasons. The principal data resulting from these investigations are presented in the following two tables. Table VII shows a comparison of the records for several localities during four months of the winter of 1904-5. During this period the prevailing climatic conditions were the most severe that the weevil has en- countered since invading Texas. The table shows therefore a eradual decrease in the number of living stages present as the season advanced. Taste VII.—Decrease in percentage of stages surviving in holt from Decem to March, 1905. December. ; January. Stages alive. ot Stages alive. G : Adults. | a | sb Adults. | © - Locality. ; A 5 : a a i J) < bo ue) E Pie) 8) 8] @ ele | & | 8 -@ S id = o 3 5) ro 2 S w . fs [3 ars w A E [2] ts} = rb) 2) j 5 ob a n oO g gj 3 a as) a 4 - a. 4S 3) ma S| oe penta, (3) Z| 5 — +a = me a — = ° a. [| ne Waele 3 o a es =| ° S A | A |A| A A] A] A |x |e] a2] ca ie ie are ae Pichs\ “Peer Perich |b ener Terrell, Tex... .- 300 | 113 | 30 9| 0 48 92 | 3,678 | 38 | 16 3 6 1.98 | 7.3 Keatehie, Wa:-25)25--2- eee eRe [eset al eee acne coe 8 Ua aad 1 120 ser 20 2 3 -10 | 26.0 Dallass Dexa =. ; ice {cc wasles sol teeta fe hel iee oot [ See NUS tel Un eae | ee 2 a Calvert, Tex. T5On ee LOn eet 0|/ 0 7 OI 2 100], SOR 1 10 50 | 10.0 Palestine, Tex.) 2- -|cccsachos c| fel Sys | eoS es slp 2 3S Raed ie Se Sie ee Victoria, (sys nal Uae le eee Se dee oe ere elle mere cea BE iy | | IHU Ne V/ 9 18 L3T | 61.0 | | I Totals and averages..| 450} 123} 31 9/ 0 36 91 | 10,155 | 52 | 24 15 37 1.15 11.8 February. March. Stages alive. | ae Stages alive. = I | & g Adults ee sb Adults a 8D Locality. ; | a | FI | uo) 8 IE £ cs 8 AZ E q J ‘so = 5 3 en = q & | 3 & q 9 & | s B= 8 . elg| -& & s al es & na RB © = Dn = n = & © B D Ss = IS Qa} » = Sy = iene = a re) algsaleo ie ° 5 o Bu leshl os ee ° 5 es) Hila) oc = ian) pea ep eet (2 2a) & \ Per ct. | Per ct. ‘Per'cts|\ ber ce. Merrell, 'Tex=:/.: GOO ||) Pal 0| 0 0. 26 SST | ee ee ee el fered tee ee oe Keatehieslasy | 15450) | 2)" 2 0) . 34 25 208} 0O| 0 0; O 0 0 Wallas .Memsr esse sac Staelin So) Seco esee seeds seca 100; 0}; O 0} 0 0 0 Calvert, Tex.... 800} 0; O Os O 0 0 2,176 |) .0) 0 0; 0 0 0 Ralestiness Mex s hoe <8 22 |e el eee ee ge ere er eee 1,599} 0} O 0|-0 0 0 Victoria, Tex....| 2,746 | 4] 0 35| 3 36 8.6 | 1,488] 0 | (1) 0; 0 0 0 Totals and averages..| 6,496 | 8] 4 4| 3 29 ACO; Oo le her On|) eat 0| 0 0 0 aIn Tables VII and IX the designation ‘‘not emerged”’ is used for those stages and adults which have not left the cells in which they developed. Adults which have previously left the cells within which they Bare and have subsequently sought shelter within any part of the bolls are designated as ‘“‘emerged.”’ Besides showing that large numbers of weevils entered hibernation in or upon these bolls, this table shows that bolls do not provide sufficient shelter to insure the survival of hibernating weevils in a winter so severe as was that of 1904—5. SHELTER DURING HIBERNATION. aT TasLe VIII.—Climatic conditions at Dallas, Calvert, Palestine, and Victoria, Tex., and at Keatchie, La., December 1, 1904, to March 81, 1905, producing complete mor- tality of weevils hibernating in bolls. DECEMBER, 1904, Temperature. Rainfall. Locality. Times | Absolute) Average | yron¢nty |, Depar- Depar- below mini- mini- mean Y | ture from | Depth. |ture from 32° F. mum, mum. * | normal. normal. °F. pe git he Inches. Inches. SSO LST RTS i eae or 15 20 33. 1 46.6 — 12 0). 74 —1.40 Tcty crn CS 0 Gt ar 6 22 39. 4 48.9) — .5 9. 62 +4. 94 ONO WL) at l4 21 | 37.6 50.0; + .1 2. 58 — .04 PORT MIE BRS x vias anos oc coe ae ewe 5 22 40.1 49.6] — 1.8 4,08 + .27 VW Oi CE): a ee 5 30 44.1 54.8 ak ez 1.59 — .26 SS A re Se ean | 38.8 50. 0 | mates | 3.70| + .702 JANUARY, 1905. ESR Se eee 24 12 27.8 38.7 | — 6.2 3. 05 +0.3 Laird leg ee rr 12 17 33. 6 41.0 — 4.9 4.13 — .47 OAD od oy 8 ES ee 13 16 34.1 44.8 — 3.1 2.01 _ POSE eDakUe ete ek. ce 11 18 34.7 | 43.0 — 2.8 2.06 2.25 WAC ET NT. cl ih 6 25 43.1 | 538.0] — .6 3. 84 + Ls lhe a | 13 | Renee ase 34. 66 | 44.1| — 3.52 Ss02 |e = eee | | | FEBRUARY, 1905. WEARS eee coho as 30 2 24.6 35.2 | — 9.4 2. 81 +1. 11 AS DATING, Mr. ee, ote eo a. aid 19 6 31.4 39. 4 —11.8 4.12 — .04 Galyert, Wee Of sy mE et So: | 21 10 28. 2 39.2 | —10.7 3. 02 +1. 20 PPRIOSWITID OR? beset ss etait 21 6 31.9 40.0 | —11.0 2.47 —1.00 WHEMITIE DORA ite. take. loo sce 10 20 34.7 44.1} — 9.9 | 3. 62 +1.42 eenraee (te, 2. - 20 a8 30.2 Baga 10 Ge le) estar | + .59 MARCH, 1905 ILI RCNA S a 0 35 47.1 59. 6 + 4.0 4.44 +1.29 LATE) can) 0S ae 0 42 3:0 62.6 + 5.0 5. 03 + .39 RUSVENU EOS. Clee eee a 0 35 51.6 62.1] + 4.4 4.95 +2. 34 ECU) hbels) l/h < e 0 37 38. 0 62. 4 + 2.5 3. 95 + .14 WAGED NOR. ote ty fds. 3 0 46 | 57. 2 65.8 | + 3.1 5.04 | +3.52 ere ty 0 | chore | 52. 6 62.5| + 3.8 4.68 | +1.54 a Temperatures for Shreveport, La. b Temperatures for Hearne, Tex. An examination of this table shows that the temperature went below freezing with remarkable frequency during this period. The most severe cold weather occurred during February, when the temperature averaged 10 degrees or more below normal throughout the State of Texas. The absolute minimum for this season at the five points mentioned is recorded by the Weather Bureau as being 2 degrees above zero at Dallas. At Calvert the minimum temperature was 10 degrees and at Victoria 20 degrees. In most of the localities there was an excess of rainfall, so that the winter as a whole may be characterized as having been unusually cold and wet. 7 2 Oe ne ey he ee 28 HIBERNATION OF THE COTTON BOLL WEEVIL. While these records show that few if any weevils survived in the shelter of bolls during this season it must be remembered that the weevils were not exterminated in all of these localities. Other con- ditions of shelter were evidently so much more favorable than bolls as to have enabled the weevils to survive this severe winter. It is true, however, that in the spring of 1905 weevils occurred in much smaller numbers than is usually the case. Other examinations of bolls show that in the northern portion of the infested area of Texas there is a smaller percentage of living stages in the bolls than in the southern portion. The data for three seasons are compared in Table [X. The periods selected are during the last of the winter season in each year. Taste IX.—/Jncrease in percentage of survival in bolls from northern to southern Texas. March, 1904. February and March, 1905. Stages alive. Stages alive. Section. Adults. | Bolls Adults. | Bolls noe having| Living] Bolls |__| H's: | having | Living mcd living | forms. imed —| living | forms. J = | forms. Fim linee | 3 | forms. 8 | g |S bo] & 81 g [Sb 2 | > | Oo ‘a Ma i) | B |S \72! & B| SA! & | =| Ay o| il a o| & Perict. | Penick: Per ct. | Per ct. Northern....---.-.- 2,600} 0} 0} 0} O 0 Oj 35258) 4 A a 0.27 0. 026 Gentrali eens h ees TBOM BO NORTON eat Oats}, || eee oe 4,575 | 0} 0] O| O . 00 . 000 Southem=.2--2---: ZOOL) Ol e235 e285 ene eee oe 9,589 | 4] 1] 4] 14 .24 . 096 Brownsville. .....- cee |e (ares) A tel eres be See a ee} [eee Sa a 809} 0; Oj; 4] 11 1.80 . 833 ; = | | | February and March, 1906. Total. Stages alive. Section. Adult Bolls Bolls | Adults. having | Living| Bolls | Stages eae Tyinealtocnieal ae ona ined. ; : = "| ined. | alive. esa) as F ie 3 forms. pee] 8 1 Sen |e a ewe ae 4 am o = Per ct. | Per ct. : INOLth ers ost he eka Soe see areas 6, 186 0 0 1 2 0. 04 | 0 | 12,044 12 Gen tral oe oh) Sa Ge ee eee 6, 650 0 0 5 1 24 | 0) 11,405 17 SOW eM fete. ee er eee eee 1, 410 0 0 1 10 - 78 | 0 | 11,249 | 85 IBroWwuS Ville © < 332.32) os ae eae ree eames Recoepeareceee (eee ony | pe 8 ee! [PAE ape ier eee | 809 | 15 It is noticeable that there is a gradual increase in the living stages from north to south, and that toward the end of the hibernation period nearly all of the living stages are adults, most of which had matured before the beginning of hibernation. That the increased mortality found in bolls during the winter of 1904—5 can not be attributed entirely to the exceptional severity of that season is shown by the fact that a similar decrease in the per- neces aia ; ene HELTEE t DURING HIBERNATION. 29 sent of living stages was found in examinations during January and February of 1906. In January among 1,933 bolls examined in several localities 86 adults and stages were found. In February 14,246 bolls were examined and only 30 adults were found. The | - lowest temperature experienced during January was 12° F. at Dallas, | with the mean temperature of 49.6° F. in an average of the eight locali- ties where the examinations were made. During February the abso- Jute minimum was 15° F. at Dallas and the average minimum 38.5° F. ‘During these two months in the localities where examinations were made the minimum temperature went below 32 degrees on an aver- age of only nineteen days TasLe X.—Climatic conditions at eight points in Texas, January to March, 1906. JANUARY. Temperature. Precipitation. Locality. Times | Absolute | Average a Monthl Depar- | Depar- below mini- mini- | mean: Y |ture from Depth. ture from | 32°F, mum. mum, is normal. | normal. | fh shit aie ah, Inches. | Inches. os 8 Ae ile 18 12 30.8 44. 4 —0.5 1.98 —0.74 SRRO MOMMIES Cher 2 oe. otis... 2... 12 19 35.4 48.6 | +1.7 1.97 | —.67 UTE) ee aE nS ee ee | 15 21 36.6 49.9 +2.0 .S1 —1.65 a CAS aoe 2 Ua 10 21 39.2 49. 6 +3.8 1.92 —2.39 UVC Ree 2 11 22 36.0 Olea +3.1 1.38 — .55 Nacogdoches 22 aie een gle ee 16 19 34.9 47.4 — .8 4.85 +2.11 CEL Es GN ee: fe Ss | 3 26 41.6 51.4 +2.7 . 81 —1.67 GHOTIC gata, ye es mn. 3 25 42.1 54.4 + .8 1.34 —1.09 Fa Ae Sin il | ee ak 37.1 49.6 | +1.6 1.88] —.83 > a FEBRUARY. 5 | LDS DDS ES i a IS 4 15 | 32.6 46.0 +1.4 2. 23 +0. 53 RGOrSiculistn ee cose Ss 9 19 | Ole 58. 0 +1.9 2.61 + .49 . UTES eee oie 7 23 37.2 49. 4 — .5 4.22 +2. 40 LES in a ee Toe 22 38.7 48. 6 —2.4 3. 06 — .45 WUTC AS ES 2 a op ee 8 20 svi: 50.8 — .8 2.65 + .72 i. IACOSMORHOESC cence. | %'9-.2-. 10 20 36.7 48. 2 — .4 176) —2.09 y Ie rer Mork 2). tS. 6 26 43.9 bent — .6 1. 29. — .59 ‘ Aina bie. So. 0S kn a | || 28 44.3 54. 4 + .4 2.01 + .19 . oa | Rae eee 38.5 | 51.0 | 112) 248) + 015 , ee, MARCH UV Gy: see, ie OS gee 11 20 | 38.9 50.8 —4.8 3. 24 +0. 09 ON SIG ie 3 aie a ee 5 27 | 39. 7 49.9 —7.6 2.10 —1.25 LISS Re ee Ce 2 26 43. 4 55. 4 —2.3 1.97 | . — .64 LIES 2 Ee Se a 2 28 |, 44.1 53. 4 —4.2 1. 24 —2.74 WL 0) Gets: Oe, Satay ae an 3 27 43.2 57.5 —1l.1 2.95 — .09 ; Nacogdoches.............- Sra 3 27 | 44.0 54. 3 —3.2 1.63 —2. 82 * oa) en one ak 1 32 | 47.8 56.8 | —3.4 2. 47 + .25 ° \Witaeug lp AS ies ae a Ll 31 DOFon} 61.0 —1.7 2.24 + .72 3 ol 2 a en ee iia eee 4.0, 5.0 | —3, 54 | 2.23} — .94 “a A comparison of the principal points shown in Tables VIII and ' X indicates the relative severity of the two seasons, especially in be the columns showing absolute minimum and average minimum | 30 HIBERNATION OF THE COTTON BOLL WEEVIL. temperatures and departures from normal. The records for February are especially significant. In 1905 this month was unusually cold throughout the State. The absolute minimum for the five local- ities considered in that year was 2° F. at Dallas and the average mini- mum was 8.3° F. below that occurring in 1906. In 1905 the mean average temperature for the month was 10.6° F. below the normal while in 1906 it was but 0.12° F. below normal. It was during this month of extreme cold with excessive rainfall in 1905 that the great- est mortality among weevil stages occurred. HIBERNATION SHELTER OTHER THAN BOLLS WITHIN THE FIELD. During an ordinary season it can not be doubted that a large majority of the weevils which survive find some other shelter than the bolls hanging upon the plants. It is not, however, as easy a matter to find weevils in rubbish scattered upon the ground as in bolls. It is necessary to collect the rubbish very carefully and sift it over cloth or paper to separate the weevils from the trash. In this way it has been found that weevils hibernate extensively in the leaf and grass rubbish distributed throughout the field. Naturally the cleaner the field in the fall the smaller will be their chances of finding favorable shelter during the winter. Standing trees are a common sight in cotton fields, and while the records of weevils found hibernating under bark are but few they are sufficient to indicate that these trees may be a rather important factor where they occur in considerable numbers. Where the Spanish moss (Tillandsia usneoides) (Pl. II, fig. 1) occurs, as in the bottom lands in the coast section of Texas and in the southern por- tions of the Gulf States, weevils find exceptionally favorable shelter within this moss. On January 18 Mr. J. D. Mitchell cut down a moss-covered tree rowing in a large cotton field in the vicinity of Victoria, Tex. Between 400 and 500 pounds of moss growing on this tree was collected and examined very carefully. Three living specimens of the boll weevil were found. On February 5, 1907, a similar experiment was tried. One thousand pounds of moss was obtained from a tree standing in the midst of cotton fields. The moss was situated from 7 to 15 feet above the ground. Among a large number of other insects found hibernating in the moss there were ten living boll weevils. The weevils seem to prefer the festoons of green hanging moss to the bunches of dead matted moss (Pl. I, fi, 2). The turnrows and ditches throughout the fields and the fence rows (Pl. I, fig. 2) surrounding them present exceptionally favorable con- ditions for successful hibernation. It has been noticed frequently that early in the season the most severe injury may occur on the edge of a field adjoining a fence row where weeds and grass abound. Bul. 77, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE |. 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. ~ ~™ ‘ Bureau of Entomology, U S Dept of Agr culture. PLATE l FAVORABLE SHELTER CONDITIONS IN AND AROUND FIELDS. Fig. 1.—Cotton field adjoining grove of trees laden with Spanish moss ( Tillandsia usneoides). Fig. 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- eally all of them. - Undoubtedly the burning of cotton stalks, weeds, grass, 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 spring. 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- oe 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 X1.—Ezxperiments of 1904 to 1906 to test hibernation in cotton seed. When | Weevils | when | Weevils | Weevils Locality. Ae eae hubeena exam- found found re ; ined. alive. dead. tion. tion. 1904. 1905 Merrell cMex sre eh ole ee =, eee ee ee eae Nov. 13 200 | Apr. 20 0 154 Oe ys Se Siete As Sys Spy LEO yen Pte PEE Nov. 30 200 | Apr. 21 0 139 A) Os aes eye epee, ae cee ea ee a ee Dec. 15 250 | Apr. 22 0 170 Corsican ay exes ie Sealey 6 ae ee ee eke ee Nov. 14 150 | Apr. 19 | 0 127 Oalvert ail Gas ee eo aoe een ac eal = ee Re ene ge ee Nov. 15 200 | Apr. 7 | 0 152 DY Oe er Se Sn Se ES SR ne age ee ae meas epee Nov. 30 200 | Apr. 8} 0 176 ead a ner NO tec ee Dee. 15 200 Gorze=e) 0 142 WViCtOrian Tem: = seen ges. 2 59225. eee a ee ee eee Nov. 10 200 | Apr. 3 0 130 ORE ie ee: Me ings Ot et Sa ee ee Nov. 17 200 a2 d0es= = 0 144 DOs es as Ie a i ee ee ee ee Nov. 25 200 | Apr. 1 0 150 I) OR cere Mey ee Oe EE See. icy yee cee eee Dec. 1 200 | Mar. 31 0 115 ST) OS ASE Sa foln oe chs ts ee ee tt ee ee ee Dec. 8 200 | Mar. 29 1 149 1D Yo fees 5 er ee care earn CSW et ee A a Dec. 15 200 | Mar. 28 1 123 Dota tele. fs ON Face. doh CR ee ea | a 22600 he ee a2 1,871 1905. | 1906. Wallace Rexere sar, cst ask ase Plt ee ee ee eee | Nov. 1 | 100 | Apr. 28 0 92 DO eee ace en ee ee eee ee eee ore Nov. 18 | 200 | Apr. 30 0 160 DD Oe inh RE ee ee RE Dec. 4 | 200 | May. 3 0 | 181 DOS Ase ee eee ee ne a ae hee ee alae eee ee Dec. 15 900 | May 4 0 862 Mo tale ant Alene cL Ae Ses Re oe Mee eee Je fico ae L400 Set ee ec 0 1,295 WiCTOLIA WD OxAe 5 oe ec eR 5 ST Re eee ere | Nov. 7 100 | Apr. 2 0 93 1 pe ay SEROUS Wan AU ar Dee! Gag Ca ee a (2 ee dotese: 100 | Apr. 7 0 93 DO ary eee A Pe SBS ES GS ee a rn ee Nov. 18 100 | Apr. 3 0) 97 DOES See ay eee ee ap ete ee Nov. 30 TOO eadio eae 0. 100 DOO it Se ai terre Reg ae ie Se tS en eS ee ciate | Dec. 11 100 | Apr. 5 0 96 MO tal: eee 8 oo te ety Oe a [eae BOOM Eee eee 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. oo 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 Comisién 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. | 2 Total number of weevils found— : mA has 2 3 & |e erie wee lh xt = es eo | leg © | go $ B fg/ 38 |g |§o . Cea Da b= | Localit 2eo!| g@ | ala. So} .(/812/818 18. = “ Ss 3 =| reales Cte eal eee eos eal - og iS) = eT is SAP es biter Tee Seed Real eed. che lo = |= |lnel ag i etl = | om | BS ing . a n n |\Ae a1, elie lial! s&s SalHui% 3 = 3 ae 5 re ay gs Be "SD = | vy ‘ob 5, = e e Pld Bl BISi ni Sia! so |‘a |* 3 | 6, > ral ral 3 g Mim | oI A Oo 5) Ot ~ a » » » — | } = | PF EF IPESO/F a 8 8/8184 /8i8 | aio = ry. 2, a Ge ee ee ae a ry Terrell, UGC eS SS es 715 244 0 |108 | 68 | 13 1 3 atietsa |) On Std | baal gemteleawe Paris, Tex ie eee 650 254 0 116 58 | 14 0 8 0|23| 8 3} 5119] Dds lapel or 489 229 OF1209) GE 10" 0. 0} 0} | 4 124 Otltee aheces oo EE ee Be ete ONOK 1 OD Wao lien alee a'<|accs|ins oe [cS Eee oe eae Lo ee POW PAD Osean A eA |e} 2k 2 of AB |e. .-[see5| ME} 12 Wt OD Pal See ee POO GOL UL 190 /290))) 6 OL |... .|-...fo- sf...) 48 | 12 |. as). | - bot ay be eng ff Lt | et MDa ee wee eevee. 5. -c...jo,020 |1, 946 | 11 |785 49) 111 | 92 | 35 7 | 51 | 54 Le ee Ms 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. TaBLe XIII.—Summary of hibernation experiments in boxes at Dallas, Calvert, and Victoria, Tex., in 1905-6. DALLAS. Number of wee- Out- | Wee- vils found— | p When = doors | vils When ex- Pease put in Kind of rubbish. orin- | put | amined. centage Remarks. doors in : alive. Alive. | Dead. 1905. 1906. Nov. 1] Corn shucks, grass, | Out...| 100} Apr. 27 0 92; 0O cotton leaves. | Do...| Cotton leaves......-.- nue 100 |-- do. <2 0 80; 0O In chicken house. 1B Ye sina (a isa do. Se eee i Cohtaaee TOO Vie=-da-= 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 1D Ye ie | eee (a (1 pane at oe meee LOO Se dole se 0 37 |. 0 Do. Nov. 18 | Cotton seed..-..---.-- nee a 200 | Apr. 30 0 160; 0O Do. INow.26 |-Only, grass, 5-224-25-2 Out...| 200 | May 1 0 165) 0 Do...| Grass, seed, cotton...| In..._. 200) |2-:dos.25: 0 1653)" 6 Do. Dec. 4] Cotton seed.......... ine. 200 | May 3 0 181] 30 Dee. 11 | Corn shucks, leaves. .| Out...| 200 |...do-..... 0 140; 0O 1B (0 a femme domo fe ee eee icieeaes 200 | May 1 0 195} O Dec. 15 | Cotton seed.........- it he 900 May 4/| 0 862) 0 300 in each of 3 sacks. | | Oat...)\-600) |. eo. | 3| 479| 0.5 Total...-.---.- {mn ra D!A00 eee 0} 1,886| 0.0 | CALVERT. 1905. | | 1906 Nov. 7 | Corn shucks, grass, | In...-.-. 100 | Apr 18 0} 98 0 cotton. | nae eae dow yee ee Out 940). dores.3 1 | 45] 1 Nov. 27 |... ghee eres ae 205 |...do..... 0 | 205| 0 OSes 0 fo re ee ee Out 200 | Apr. 19 | 40 145 | 20 |fOut. - 204 a ee eee 41 190 14.0 Total. ------.-- {mn Bik: B05 | seeds ae | 0| 303) 00 } | | | VICTORIA. 1905. | | 1906. INOVes 5) | Mixed=2.-2 0 secs Out. 100 | Apr. 2 43 2 INOW Est, |-2=- 2 COE 2 see Out. 100 | Apr. 7 1 23 1 DOs eee GO eae eee Imees 100 d0s-2=- 0 73 0 INOVverios|=- oes OlWameoscean sans Out. 100 | Apr. 4 4) 53 4 Ont |Penee G02 52 ssi ee sees: mens 100 | Apr. 5 0 | 97 0 Noy a0i/22--- dO. eee ae Out. 100 d@-<2-- 1 39]. Neel oes co es ee ee sine | 100 does. 0 94] O 1B Yer We ee GO! Sscoee os ee Out. 100 | Apr. 7 3 51 3 | ee GOs cn ecereeeesce inee- _ 112 |...do.....| 4 100 Shy | Out BOD i eee ee Pee 209 | 2.2 Total...-..--.. i Sis B1D| see ee | 4| 364 97 Total of 3 local- |fOut-..|1, 394 |......-.-- (S51 sed gas9 ities cores In.... 12,817 |......2..- | 4) 2553) 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. $7 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: Tasie XIV.—Comparison of survival records outdoors and indoors for three Texas localities in 1905-6. Outside. Inside. : Weevils survived. Veevils survived. Locality. Weevils eevils s ived Weevils Weevils survived put in - put in hiberna- Sarnany. | hiberna- ae tion. |Number.| Petcent | “tion. | Number.| Percent age. | age. | TE a a | LV od We 500 11 232: 412 | 4 0.97 Cy STH oot see tl le a 294 41 14.0 305 0 | 0 PIR es I ye ee een 600 3 ahs, 2,100 0 | 0 8 SRDS hep eae | 1, 394 55 SG “287: | 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. Taste XV.—Comparative favorableness of periods for entering hibernation, 1905. ari Total Herod. survival. | | Nov. 1-15, 1905. Nov. 15-30, 1905. Dee. 1-15, 1905. ls Locality. | Weevils Weevils | Weevils Inum-| Per Weevils) survived. Weevils survived. |Weevils| survived. Rerelcare ut in | Paoli gh 1) putin | niber- ] hiber- | | hiber- nation. Num- Per | nation. Num- Per | nation.|Num- Per ber. | cent. ber. | cent. ber. | cent. oy | | VO jo Da a | 500 | 2 gel Was 200 | 1] 0.5 212 Tale ores 15| 1.60 SHUMO EULER ow fost. ac 2. - 194 1 5 | 405 ADP LORON Kronen see | ercteesedll aero 3 4] 6.80 OPEC) GO Vy a ee ee 300 0 .0 600 3 5 400 0; 0 3 23 Daya eo = 994 8 8 1,205 | 44 | 3.7 | 612 | 7 | Wo | 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 88 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. Bermuda manna nC old | Locality. grass and | Excelsior. Paper. Tonwes cotton Total. hay. * | stalks, and bee bolls. MICTOUIA LOS. = = eee eee 5 =4 aL 1 4 | 15 Calwert, Dek: oo. 2 ssdi see Sao i oe Asean ee cae een tee eee el eee ee 41 41 Mallac! Tex. rio kclee tee | CM PSM ae tai MR ieRit Gin Ee Ye he ee 3 ip talss seen oe | 8 4 1 | 7 45 59 This shows the favorable nature of old corn and cotton stalks, amone 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.) bd bie XVII. Reds of installation and emergence records in cage at Keatchie, La. 5 ey E d : 6 March, April. | May 1-14. = ES Be | Ss r=} oS a & “cs Shelter in cage section. ad ee ae Oe ee eee ee r= | & =) ey e = @ q © = Ss ° 2 o% =r 2 g 2 g 2 . hs i ed lad a] 3 |3/ 8 |8| 8 a = = Zz Be Bae am Bas ee | ee 1.. Louisiana.) Nov. 29 | 1,200 | Brush, leaves, moss, stumps, logs;}. 2 | 0.166 | 3} 0.25] 4 0. 33 stalks removed. pnp fe do.......| Nov. 25 | 1,000 | Same, but stalks standing........ il eot en as i te. ha 1.0 ee aC 1,000 | Cotton seed piled; plants left | 1 1 4 A res standing. a EE B@teeee, sina. cox. 1,000 | Same, but seed left uncovered....| 2 | .2 5 6 Olieeese oe 1p!) Rey | aia OTe aes ,Q00'| Absolutely bare... 2.00.6... lg) |) >oaal 1 unl OF seer Giclee Orns: -. 2, Mave ws: | 1,000} Ordinary held... 2. 0icwnccenecs 5 5 18 | 1.8 4 4 Stalks, grass, etc.: “oS Me Ra can Nov. 29 | 2,100 DAIMB AINE bo oe ok duu ct ene 2 .09 17 -81 | 16 . 76 eee Osecat | INOV..20 | 1,500 RGINOnSaiwe Recs ect cose 2 a LE Baal Qe Plo 1.0 Melee. eee 2t.200..<..| 1,000 BUI ONES eles tasers es cos seis Aa SY? 9 9 3 .3 Be Fenn dO. .<.«..|...00..... 1,000 TEAS es eho egn 5 eke 2| .2 15) 1.5 tej ee iy ed ieee Olen ns / 1,000 POLUO MS Mee ee ican nd enk 3 ae (0 eee 1071) 230 4 4 1 ea do-......| Nov. 23 | 1,000 ATURE Nace ee ress See WO) e uss Li see ke 12 13..| Louisiana., Dec. 18 | 1, 000 ee lett, leaves, etc., added; } 1) .1 2 2 1 1 shaded. 745.) -LOxas. ...- Dec. 3 4,000 | Same as 13, but not shaded....... yO (ae | 29 1@4,\(alv¢ .42 i ery ee Ouse SO. <<.4| SU} MOIS ats ce Jee oes o cleecacicc'e co 9 one 94 2.35 | 28 Py, Cs oe do.......| Dec. 8 | 1,000 |..... EL yay Soak aes OR ih A Dileeieey dbo), clabe |oee 5 17..| Louisiana.; Nov. 28 | | 00 Oe eee Co Lope tg eS nee esi ee Re ae | 4| .4 Ligeia fe LO 1.0 ch ey ia G0 -csuaeu! INOV.'18 _ 1,000 Cheek on 13; stalks, grass, leaves, | 0 |.....-- Ufa) |} es 8 AS not shaded. MREEIMRIEPOR 25, 800"|. 2: 2 va. 2c ne cae ce ee ceeccccs| Si) 18 [aut TD Dy 53 Installation records, 1905. Emergence records, 1906. 33 > 7 aor 2 | db ky = z si a ae a : Marchito | 2 BE Sh = 3s 25 * May 14. = Miia ara SS 5 Bs Pen Se OY Sioa Seemed tS ee Wa et = = oo a= = a Shelter in cage section. Ai aS oe st S'S “3 8 ss os | ce Ain Se coe e ys ei SE #3 ia | | = aa a| - = Z Z a |e a mo ae. ! Genisians. Noy. 29 1,200 | Brush, leaves, moss, stumps, | 9 0.75 26 2.16 11 | | logs; stalks removed. Pe ae do.......| Nov. 25 | 1,000 | Same, but stalks standing..... jeer "7 LNT 25 2.5 9 OrrisasUswe-won)- G0. --.s 1,000 | Catton seed piled; plants left | 5 a) 6 -6 16 | standing. | eS ee G0ie. ne -|--.00. 2c.- 1,000 Same, but seed left uncovered. 7 7 Bo 8 15 Jae) ae Geen ete alO. >= 1,000 | Absolutely bare............... 2 2 4 | -4 17 Gist Dexas 2. cc owes Wa OO bOrdinary field.;...25.0.-02..52 27 2k. 38 3.8 6 | Stalks, grass, ete.: (eles s0Ousse-.) NOV. 29") 2,100 Sa Te eR 35 | .66 | 44 2.09 13 8..|...do.......| Nov. 25 | 1,500 Marne Ae Oat ac ek 50| 3.33| 64| 4.26 3 Seedy. 2.4141. 40... “Fh Og Sc a a i as Ped a Pa 4 10.-|.- do... AO. 2) rug e Manis as4.c.-,./....2.0.... Dit ley dl RDO NL obo 10 ve le 1 EE ee geet: (ee / 1,000 | BAMIG ASO ere ets ee! 14 1.4 26 2.6 8 ho, NOV. 28 | 1, SANTO ASO sete ie ee 29 2.9 55 5.5 1 ie Louisiana. Dec. 18 | 1,000. Btalks left; leaves, etc., added; 4 4 8 if 15 shaded. 14_.| Texas..... Dec. 3 4,000 | Same as 13, but not shaded....| 50 ecole TSG 2.15 12 Repre e see CLO cia a ee WMO GINO GS 14.0 oo. oak ek coeice BPA eB Bete ab oally(O) 4.25 4 ioe oe. foe! 1, 000°). 2.:- ORR ete re tence ats Ee se 21 2.1 35 3.5 7 17..| Louisiana.| Nov. 28 | 1,000 |..... it ee ae oes eee BSE Se fal 41 4.1 5 a ae do....... Nov. 18 | 1,000 | Check on 13; stalks, grass, 7 a 53| 5.3 2 leaves, not shaded. Dotais and averages. |25,800 |.............--..----2- eae 487 | 1.5 TOS he Dae (eee | Installation records, 1905, emergence records, 1906. 40) HIBERNATION OF THE COTTON BOLL WEEVIL. The beginning of this work occurred so late in November that none of the sections can be considered as having been placed in hiberna- tion early. Cold weather occurred between about November 30 and December 3, during which time the majority of weevils entered hibernation. Emergence appears to have begun on March 22, and the last weevils emerged on June 28. The emergence during April and May was quite uniform, while during June it decreased rather steadily. In these records no allowance has been made for the escape of weevils through the wire on the cage. Using the number placed in the cage (25,800) as a basis, the 728 weevils which emerged con- stitute a survival of 2.82 per cent. It is impossible to call attention to all of the many interesting points shown in this table. Special emphasis, however, will be given several points through the rear- rangement of the significant data in succeeding tables. Since climatic conditions are primarily responsible for hiberna- tion and the emergence of weevils therefrom, the records should be studied in relation to a chart of the temperature conditions, such as is given in figure 1. No climatic records are available for Keatchie previous to the beginning of these observations upon March 15. The emergence of weevils may well be shown in relation to the range in temperature upon the same chart. In studying the effects of temperature variations upon weevil activity it has been found that those temperatures which are about 43° F. alone produce activity among the weevils. Because of this fact 43° F. is regarded as the starting point in emergence records, and all temperatures above 43 degrees may be spoken of as “‘effective temperatures” upon the following diagram; the average between the maximum and minimum extremes for the day is recorded as the mean average temperature. While it is probably true that maximum temperatures have a special significance in their effect upon emergence from hibernation, and that minimum temperatures have a special effect upon entrance into hibernation, it will be more simple and sufficient in this study to use the single line representing mean average temperature during the emergence period. From this diagram it will be seen that the emergence at Keatchie in 1906 occurred practically during four rather clearly defined periods. These periods are separated by marked declines in the mean average temperature. It will be noticed that as it became warmer following these cold periods there was an increased emergence of the weevils. After the middle of May so large a proportion of the living weevils had emerged that the number recorded became gradually smaller, although the temperature rose still higher. Some of the special facts demanding attention are those relating to the effect of the various conditions of shelter upon the survival of weevils, the relation of emergence to effective temperature in LARGE-CAGE EXPERIMENTS, KEATCHIR, LA., 1905-6. 41 various periods, the relation of the time of putting into hibernation to the time of emergence therefrom, the relation of accumulated effect- 8 EAE 7 onerets TNE s DE EOREE: Ss bi 17 oO —— | | “Sannin rye fi acl a ES See “‘Q06L ‘OUNL 07 YolvPY “eT ‘olyoyvoy ‘oousZIOULO [I1AooM pue ‘[[esUles ‘oIN{BOd ULE] OF¥IOAB UBIUI SULMOYS yIBYD—'| “OL =. ~~ = a ace IN WCHES o wm ° i) ° NUMBEF OF WEEV/LS EMERGED ive temperatures to emergence, and the longevity of the emerged weevils. These subjects will be considered under succeeding topics. FAVORABLE CONDITIONS FOR HIBERNATION. For a study of favorable conditions for hibernation those sections have been selected which are most strictly comparable in respect to 49 HIBERNATION OF THE COTTON BOLL WEEVIL. the time weevils were placed therein, the source of the weevils, and the nature of the shelter. Practically one-half of the weevils used were collected in Texas and sent to Keatchie for this work. The sections used in this comparison received weevils between Novem- ber 23 and 29. Tasie XVIII.—Favorable conditions for hibernation determined by rank in percentage of weevils surviving at Keatchie, La., in 1905-6. Weevils survived. Weevils |_ : | Rank of put in. section. Number. | Per cent. Section num- ber in cage. Nature of shelter. band 122-2. Ordinary field stalks, grass, etc............-...- 2,000 93 4.65 1 and 8.2222 Brush, leaves, stumps, logs; stalks standing. ... 2,500 99 3.56 2 NANCY onan ora Same as above, but stalks removed..........-... 3,300 70 2.12 3 Aand 0. 2.5.2 Cotton seed, piled but uncovered; stalks stand- AN Phos hee econ tae eee Seen ae eens eee 2,000 30 1.50 4 nat ib Soa APSO ye bare Ground = ass ee eee 2,000 30 1.50 4 Spraats WORE Cotton seed piled and covered; stalks left stand- ING? Sooke Soin esaacee eee eee mere cee ee ee ee eer 2,000 23 115 5 It is evident that ordinary field conditions where stalks are allowed to stand together with the grass and leaves littered over the ground are as favorable for successful hibernation as any conditions. It must be admitted that the shelter conditions in the bare sections (5 and 11) are not such as would occur in a field plowed in the fall because of the fact that the inclosed weevils could still find shelter in the structure of the cage itself. This will undoubtedly explain the survival of 1.5 per cent in two sections having no rubbish on the ground. It is apparent, however, that even with this advantage of cage structure over bare ground, slightly more than three times this percentage of weevils sur- vived where ordinary field conditions existed. Without the shelter afforded by the cage this difference would undoubtedly be very much ereater. In 9 sections which contained rubbish, among 15,500 wee- vils, 567, or 3.66 per cent, survived. The shelter may therefore be held accountable for increasing the survival at least 2.1 per cent. Thus upon an area where no more than 15 weevils might survive with- out protection, 36 at least might be expected to survive with the pro- tection. } EFFECT OF ACCLIMATIZATION UPON SURVIVAL AND EMERGENCE. It has already been mentioned that about one-half of the weevils used in this work were collected in Texas and one-half at Keatchie, La. In order to determine whether this difference in the geographical sec- tion in which the weevils developed might exert an influence upon their survival and emergence the records for a number of comparable sections are combined. These weevils were all placed in hibernation between November 25 and 29, 1905. LARGE-CAGE EXPERIMENTS, KEATCHIE, LA., 1905-6. 43 TabLe XIX.—Comparison of emergence records at Keatchie, La., for weevils collected in Louisiana with those collected in Texas. . Percentage of emer- gence during each month based upon total emergence of— Date. 6,200 wee- | 6,600 wee- vils col- vils col- lected in lected in Louisiana. Texas. 1906. | i Ce tS a ee oe oe die nctaw awwawaldpacesaccecienewcue 9.09 4.6 ON et oe og ee oe oe Soe cameleiss leaUdeuweecceccucecnes 33.63 48.6 ae 5 IS RS RS SL 21.82\.0 |f 21-945 9 eT SECM RES ree es eee i ee ee cs dcucecacds RY aca Wie CET a RR Nd eg ae cane ewcewendenue ce eee 7.28 4.6 | 100.00 | 100.0 Altogether in these sections 110 of the Louisiana weevils and 173 of the Texas weevils emerged, making a percentage of total survival in the former case of 1.77 and in the latter case of 2.62. On the whole the Texas weevils emerged slightly earlier than did those collected in Louisiana, but the records are too nearly similar to indicate that such would regularly be the case. RELATION OF EMERGENCE TO EFFECTIVE TEMPERATURES. The practical point in these studies of temperature and emergence relationships is to ascertain the facts upon which emergence depends, so that it may be possible from a study of temperature records for any locality to form fairly reliable conclusions as to the effects which those temperature conditions may have had upon weevil activity. In this way it may be possible to determine approximately the time when weevil emergence begins, the time when the majority of weevils will probably have left their hibernation quarters, and approximately the time at which emergence becomes complete. In this connection it will be profitable to compare the records for Dallas, Tex., with those for Keatchie, La., for the same periods. The total effective temperature is obtained by computing the sum of the mean average effective temperatures for each of the days included within the period shown. For example, if the mean average temperature for the first day of a period is 60° and for the second day 68°, the average effective temperature for the two days is 17° and 25°, respectively. The sum of these, or 42°, is the total effective temper- ature for those two dates. 44 ’ HIBERNATION OF THE COTTON BOLL WEEVIL. TaBLeE XX.—Relation of effective temperatures to emergence at Keatchie, La., and Dallas, Tex., 1906. Total effective Average effective Number of weevils tem perature. temperature. emerging. Periods of emergence. a Keatchie.| Dallas, | Keatchie.| Dallas. | Keatchie. Dallas. } | | 2 Se ee we oF. MSE Latif oS ese cok nea coe CE ape eNe 12.0 5.5 1.7 0.78 0 0 1 CY (te a AP Ae Re RR ie nm 141.0 151.8 23.5 25.3 25 2 Mars 28-ADY 2. -scsnc2 2s -tiese a eeeee eee 37.0 66.6 7.4 A 12 0 28) 0) Fo dS See SR Pe ee Ree Ets en 275.5 243.6 25.0 22.14 165 28 DXi oy a od eee PEAR ae F 118.5 124.1 16.9 Ey 28 0 ADE. 2I-Mayi5- 2 ssa) e ee eee mae eee 484.7 435.8 32.3 29.0 187 18 MAW GI oe c tc Sat ack en ee See eaten 176.0 159.8 22.0 19.9 49 0 May AAn2S. 2 oi ahs Pee hee ee ae eal nee 339.0 300. 2 33.9 30.0 173 7 May 24-29 ok aia ste cone San uetee ee See ae 201.0 196.8 33.5 32.8 23 0 May S0=JUNGHiLe Soot eee a: nee eee 413.0 478.0 Aon | aes og Se 65) |.2-5 536-55 MUNG M20. sa Sean ce re neers Rene 667.0 700.0 5}! Bra aera, Si 8 ieee see An examination of this table shows three very distinct periods of emergence, the first being from April 3 to 13, inclusive; the second from April 21 to May 5, inclusive; and the third from May 14 to 23. No weevils emerged from the Dallas cages after May 23. At Keatchie a fourth period may be considered as occurring between May 30 and June 11. In this place the emergence ceased on June 28. It is noticeable that between June 20 and 27 no weevils had emerged. It will be noticed in the table that the periods of largest emergence are separated by periods having decidedly lower temperatures, during which emergence was decreased, although it did not cease entirely. The relation of emergence to 5-degree increments in effective tem- perature is shown in Table X XI. TABLE XXI.—The relation of emergence to increase in effective temperature at Keatchie, La., and Dallas, Tex., 1906. Keatchie, La. | Dallas, Tex. | Range of | : Total num-| Per cent, effective | | ber of based on tempera- | Number of Per cent of Number of Percent of, weevils | grand total tures. weevils total weevils total | emerged. | emerged. emerging. emergence. | emerging. | emergence. | | | a. IE: See 20 | Qi 0 0 20 Oto 15-20 pone 52 (ail 2 3.6 54 6.8 DI 20cm eee 116 16.0 25 45.5 141 17.8 26s 0neee 127 | 17.5 18 SPATS 145 18.5 SHES eo a= 309 | 42.4 10 | 18.2 319 40.7 36-40°. . -- 84 1D 0 0 84 10.7 41-50°.... 20 ids 0 0 20 2.5 Total. 728 | 100. 0 a0) 100.0 783 100.0 The number of weevils emerging under 14 degrees of effective temperature, or 57° F., is very small indeed. From that point the emergence increases with the increase in temperature until after a majority of the weevils have emerged. Most weevils left their winter quarters during an effective temperature averaging between LARGE-CAGE EXPERIMENTS, KEATCHIE, LA., 1905-6. 45 21 and 35 degrees. At Keatchie 75 per cent and at Dallas 96 per cent of the total emergence took place between these limits. At Dallas the largest emergence occurred between 21 and 25 degrees of effective temperature, while at Keatchie the largest emergence occurred between 31 and 35 degrees. In considering the effect of temperature upon emergence it must be remembered that the nature of the shelter within which the weevil hibernates must inevitably have an important bearing on the time at which the weevil becomes active. RELATION OF TIME OF ENTRANCE INTO HIBERNATION TO SURVIVAL AND EMERGENCE. It has previously been stated that none of these experiments was instituted more than about a week before it became cold enough for practically all weevils to hibernate. For this comparison it is pos- sible to use only the data for those sections having similar conditions as to (1) the source from which weevils were obtained, (2) the time when they were placed in the cage, and (3) the general nature of the shelter afforded. TaBLeE XXII.—Relation of time of emergence in 1906 to time of starting hibernation un 1905. Percentage of total emergence, 1906, occurring in— Section When wee- Per cent number in| vils were of sur- Remarks. Fh putin. | March. | April. |May 1-14. ae 15— |Tune 2-30.) Viel. une 1. 7 and. 8....- Nov. 25 Bnd 46.3 28.7 1557 oD 3.0 and 29. Texas weevils 14, 15, and | Dec.3and 4.8 47.4 17.1 24.7 shy 3.23 7 ; 16. 8. Dre de dh. Nov. 28.. 9.7 41.4 24.4 22.0 2.4 4.1 |) pee a a Ree ft. . Nov. 18.. 0 28.3 15.0 32.0 24.5 5.3 |; Louisiana weevils. In the first section of the table, among weevils collected in Texas, it is apparent that there was practically no difference in the time of emergence between those placed. in hibernation from November 25 to 29 and those started December 3 to 8. - In the second part of the table, among the Louisiana weevils, those entering hibernation November 18 emerged more slowly than did those placed in the cage November 28. The explanation of this may probably be found in the fact that the first date was not sufficiently early to insure the death of many weevils by starvation before they could hibernate. It did, however, allow a larger proportion of them to penetrate deeply into the shelter than in the case of weevils placed in the cage ten days later, which was only one day before a marked decrease in tempera- ture. The weevils placed in the cage on December 3 and 8 experi- enced warmer temperatures than those placed in on the 28th of November, and, therefore, found conditions more favorable for their 46 HIBERNATION OF THE COTTON BOLL WEEVIL. . entrance into hibernation. The records indicate that there is a most favorable time for entrance durmg which weevils may find shelter from which they will emerge rather later than the average during the following spring. THE RELATIONSHIP OF ACCUMULATED EFFECTIVE TEMPERATURE TO EMERGENCE. In studying the relationship of accumulated effective temperature to emergence the initial point has been set arbitrarily at February 1. It would be both interesting and profitable if we could determine positively the exact effective temperature conditions under which emergence from hibernation begins. This point will be further dis- cussed in the light of the additional records obtained in Texas in 1907. The object in this particular study is to determine the relation of accumulated effective temperature to the accumulation in emer- gence. The records for both Keatchie and Dallas are included for the sake of comparison. TaBLE XXIII.—Relation of accumulated effective temperature. to the beginning and accumulation of emergence, Keatchie, La., and Dallas, Tex. Accumulated ef- Accumulatednum-| Accumulated per- fective tempera- ber of weevils centage of total Beidnsolemerecnee ture. emerged. emergence. Keatchie.| Dallas. Keatchie.| Dallas. Keatchie. | Dallas. 1906 oF, oF, | jot] eee ee OD Retck Loi t itis eu 145.6 208. 6 0 | 0 | 0 | 0 i aa oY Ree ee RR EC A OR Lad 282.1 325.0 0 | 0. 0 | 0 Wite ib ot sue sea ee ete 294. 1 330. 5 0 | 0 0 | 0 i EN py 7 SRO eRe SS Jal SRI R TUBS 435.1 482. 3 | 25 | 2 | 3.4 3.6 Rieig OG™ Avorn ae eRe OEE hs 472.1 548. 9 37 2 5.0 3.6 Apr siya ee 22 ee bt ee 747.6 792.5 202 30 27.5 54.5 Mor aon 28 ke tees eed 866.1 916.6 | 230 | 30 31.3 54.5 sj 0) cope’ al ES es) a i en eH 1,350.8 | 1,362.4 417 | 48 56.8 87.2 CE cS bake ea eet Se ip 1,526.8] 1,512.2 466 48 63. 4 87.2 Maal dogs ce ey 0 eee tren ee 1,865.8 | 1,812.4 639 55 87.0 100.0 May od dite ot, Seen ee a tee 2,066.8 | 2,009.2 662 55 ON: 0} a see Mays0-tine Wi. ee. eee or eee ee 2,479.8 | 2,487.6 | 727 5) 99: 0p eee ose BTS 12 SUC ea ete ke een | 3,146.8 | 3,188.0 734 55 00:0 ee eee _ 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 fram 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. Taste XXIV.—Relation of accumulated effective temperature to accwmulated emergence in field observations at Victoria, Tex., in 1904. _ | Accumu- Accumu- Accumu- ated lated Accumu- lated 5 lated number percentage | ~ lated percentage Periods effective of plants of plants number of of weevils d t : examined rapa at each date empera- of cotton toventire weevils LorantirG ture. Roe number found. number * | examined. found. He Lilsja Uke 2a 2 Oe ie ee i a eee 508. 0 None. None. None. None APR ee eee ee ee he: 585. 5 250 4,2 19 2.93 La LET je lead Thoda bets 650 11.0 39 6.0) LA a 2 2 a een eee 1,240. 0 1,190 20.1 65 10. 05 co Ls aed Oe a eee 1,378.5 1,720 29.1 100 15. 40 Le PLR SSIS 0) ne ES ea ae ee 1,537.0 2,120 35.9 160 24. 60 ere ee eo, be ee tc. 1,656.0 2,320 39.3 200 30. AC So UDR SS ae ee 2,104.0 2,570 43.5 224 34. 56 Learnt ee ee eee 2,374. 0 2,990 50. 6 376 58. OC LO LAS Lt 8 Mite tS pe ae a } 2,584. 0 4,163 TOS5N 521 SL. 0C Cy UAL eea Dogs he id re | 2,814.5 5,900 100. 0 648 100. 00 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. TaBLE XXV.—Longevity of weevils after emergence from hibernation, without food, at Keatchie, La., 1906. | i j Number | ....; Average || | Number| .,.._., | *Yerage Date of emergence. | of weevils| Wess iT oes || Date of emergence. of weevils | yulesau pena emerged.| C2YS- At AS lemerged.| ays: of days 1 dived: om || | = lived. 1906. 1906. | WWE A oe Bees ae 1 62.0 | G25 Oe Ma ygiaee seen ae 16 292.5 18.2 Arlo esc 2. os: 44 905.4 QU 7, Naas = eee aor 16 262.0 16.3 SA TULA Se es 35 751.0 14 | May Ole eee 1 1.0 1.0 AM TIF 2S: 255.255. 29 678.5 Bea Mey eee eet 6 54.5 9.0 aris ea 8 261.0 S06 i|eMayiD te hee 5 13.0 3.2 Mprileise se as 7| 169.0 244 -|| Mayas) ese 1 1.5 1.5 Aprildssc-0 5s 5| 100.5 O01 May 14) ree 8 58.5 73 Morigen a 2 | 59.0 DO Sci Mary si56 22 tae en 2 26.0 13.0 raril digs ey Ph ore ee eal Mek ee I) Way 160502 me: 13 169.5 13.0 pri) os kek 2 55.0 2735 |\sMay gsc eee | 6 58.0 9.6 Apri0eses ote) 3 11 | 119.0 10:8 le May 18.323 | 4 48.5 12.1 Seri oie 9 | 92.0 | 10527 |W Miry 20) 8 eae 2 23.5 11.7 Apropos. 25 ee 23:| . $378.5 | 1622;,| |p Mayes ones. ee | 2 29.0 14.5 pra ses a 6] 1825 |. e2ak0 Hania Db eee ete | 2| 26.5 13.2 Mpris =? oes 4) 36.0 | 930))| May 28.2 * enc is"s 1) 1.5 1.5 ADTs = pase sete 9 | 83.5 | Shel elu ert See RS aoe 1 | 7.5 7.5 April 26..........-- 3 | 24.0 | 310 || Way 30.2 esels ee 4|/ 35.0 S27 pRUIZS eee tee 46 | 855.0 | TS<5)i|| ene Ose ee ee iy 7.0 7.0 Ljovail i). sae ee seas 18 313.0 Diesel) une oo ee et i) 4.0 4.0 Mad: Mac aae 2 15.0 7.5 = Mayr 352 15 173.0 1185 Totals and Mayra: <5. ace seo 28 431.0 IS}, average 418 | 7,155.0 17.11 Mayibs i. 4 ee tans 19 342.0 18.0 | aIn 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 lfe 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- ticn 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. Tabie XXVI 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. | | Netive | Weevils | Percent- | Percent- Date of Daviot Stee ee em OULT CL ageof | ageof ena) odes Section | ae Bethe, Weevils weevils, | dead, weevils | living first largest of cage. Kind of shelter. putin. | pacers | Decem- | active, | among Saar Sonica 1905 ’ | ber 26, | Decem- | those ex- e006 ? e006 : | : 1905. | ber, 1905. | amined. ‘ ; 1 hy, | PLAT ay” 1 ap ee | Cotton stalks...... | 2,600 375 615| 14.4 38.0] Apr. 4| May 2 1 Uf Pt.1...| Cotton stalks re-| 2,500 | 200 515 | 8.0 28.0 | Mar. 22| Apr. 9 moved March 22, 1906. EMMI PUOMOSEALES ANG | 2.25226 |lfs22 222-2 |e. cee ee ee|- soc oe ees Ieee vee Apr. AS kAvpre aul leaves. | ILI: tie of eat Oa 2s 42. Se 3. oe 2,500 | 260 1,205 10. 4 | TATA | 3%) 9) EPS Ns oy el ood: ek ee oe ary. Doi lds ith oR, eee Pn |e May 14| May 14 eV | Piakos.| Liled boxes... .-.. 2,500 238 1,625 | 9.5 12.7 | Apr. 4) Apr. 11 Ree R IE RIMCARICRE CIULOLI I eo iow cl oie ne in| sin wales og n|aaceunowcs|CSccceecue Apres. 9s) Apr 9 stalks. | Total and 10,100 1,073 | 3,960 10.6 213 average. | | | 90317—Bull. 77—09——4 50 HIBERNATION OF THE COTTON BOLL WEEVIL. TaBLE XXVI.—Large-cage experiments in hibernation at Dallas, Tex., 1905-6—Con. Emergence by periods. Rank Per- of whe l Total | °&2* | cages eer Kind of shelter. | | | sur- | 96° | i hts Mar. | Apr.| Apr.| Apr.| May | May May | vival fey basis 22-31.) 1-10. 11-20. 21-30.| 1-10. 11-20.'21-31.| vival ofsur- | | | | * vival ee Cotton stalks.............. of at* ol) el teeth An Sigmar 2 ; 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 IS dee 1 FUT: PEs. | SBaret sot bee eee 0 | 1] 0) ey 0 0 0 2 12 5 te Pt 2 =: 2| Hay.) ee eee 0 | 0 0 | 0 0 A 0 t Ue) Fe ea ‘3 m } PEA Piled*boxes:. 4.5 3 -- 0 | 4 3 2 0 1 Bi, Weal 3 ie Aa Corn and cotton stalks... ..| 0 2 0 0 0 0 0. 7 lel Re 6 Total and average...| 2 17 12 13 5 5 2 561 .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. Anode ; : . + ; : a . ‘ 7 -¥ > ey a Plat cae Mahe tg i} " ew ef ,, Levan —_ Ped Tul LN + Raa 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.) LARGE-CAGE EXPERIMENTS AT DALLAS, TEX., 1905-6. 51 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. TaBLE XXVII.—Jntermittent activity of unfed weevils after emergence, at Dallas, Tex., 1906, ' - ‘ Weevils ‘‘rehibernated ’— = ~ Number of weevils seen a Once. | Twice. Three times. ee | ~ -« | | = 8 SEE ee 2 | id | = = : A - bs | | 2 rf R : ~ o risa | = = eo n S| =| : ' . = 5 = = © a A= L _ L o & | ~ — = = — = 2 Y > Te PS bap a om an = a Veg vi = w = as z : S ® & > ~ | ot | n =| a = wi S = = = 34 v > ce) 5 rae 4 sy = ay 2 o re May on 2 | wes "as ~ ea ~ S a 2) a _ -- & | mM nm |R| G i=) 4. io va Q 4 | Ez amorie A & CVE “eg Hd ng as = i 5 22 an ne | a= = a los =) = = a |eA LS eee aa en BEES eae 4 Ge Beet Base cate _ 346 | Weevils not removed. MAY oo eos ee BGS Hl eS peers |e ee AE | Bee | 358 Do. May 28.4 | JUNC Bose 4s eee cag eae Uaeaeney (pees [Ee es es 492 | Weevils marked yellow= 492. Ne NS. ae sae Pew) a8 fd bie Dee (an 28 YE al a 355 | Weevils marked blue=226. June 23-July 5..... 16S 27. Ot St OO eee 228 | Weevils marked red=87. July 23-26---.---..- 73 SO 160 ea ce 2| 739 Weevils marked white=78. Dotak. <%= .2. 2,318 |159| 9]18|10| 2] 2 2, 518 | | | | | a Kighty-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 humber 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. 55 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 might 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. (Pl. 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. In 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. between bottom and upland. (Original.) 9 ” .—Victoria, Tex., cage on sandy-loam slope Liteon hak sheets fi qa + =epowiell @ aA ihha > LARGE-CAGE EXPERIMENTS, 1906-7. 57 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. TaBLeE XXX.—Outline of hibernation experiments in 1906-7. Date of starting experiments No. in 1906. of sec- Character of shelter supplied. Food supply. Dallas, | Calvert. | Vietori, | 1} Oct. 13 | Oct. 138 | Oct. 25 Leavesand grass,4to5inches ...| Allfood removed after two days. a ope a er, 10. |..-do.2..)....- “a Lo SPF eh Si aa eye ee ee ee Stalks cut down and left to dry. 2} Oct. 19 | Nov. 26 | Oct. 28 |....- OCR Se See Uk a ale eee | All food 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 | ae and grass 4 to 5 inches | All food removed after two days deep Beaver G jiNov, 6°) Nov. 14 |... -- CLO ass ede ea Oe creak ss _ Cotton cut down and allowed to dry. 3 | Nov. 12 | Nov. 1 Nov. 21 | Leaves and grass, 2inches....... | Do. et | Nov. 12 |...do..... _ Leaves and grass, 10 inches....... Do. 6 | Nov. 28 | Nov. 25 | Nov. 28 | Ground absolutely bare......... | No food supply. 0 Dee. 6] Dec. 3 | Nov. 29 (a) a In 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 im 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 during 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 = i 1906-7. b E-CAGE EXPERIMENTS LARG a m 35 =30 25 > 4 / VEAL RECENT 4 FEBRUARY IOS 1522120 (Dee Sieee20 SS Rae SE eee eee ee ee Fic. 3.—Chart showing mean average temperature, atttall. and weevil activity, Dallas, Tex., October, 1906, to March, 1907. ies: 050 30 : g & HIBERNATION OF THE COTTON BOLL WEEVIL. 60 “LO6T “Youle 07 ‘906T ‘100900 “Xa, “WaoATeD ‘APTATIOV [[A0OM puB ‘][VJUIeL ‘ornye10d U9} OSLIOAR UBOUL SUTMOYS JAVYO—'f “DIT TeIN/ ee Ni 7 a= ogee 8 RY m 3 ‘ il CUA ial S7T/AZIM o : ahh it yg 1L ie Ht ZA | \Y ol S\ ? SIGWIIIO lili ie ae par OA DP S (AF he a7 02. aa Ef cet | | | Ss! ol 02 9 EW AON w w w wo to < pas S7349.90 DHL FANT FIY AT. 7 s, 1906— ty RIME CPE E 4s AGE Cc LARGE NOVEMBEF DECEMBEF SANUARY FEBRUARY 10 15 20 10 / deqa coe ee i Oo 96 a: 7 pea (si i ( 90 ara Van A A VW 60 ion aanm a ee a ipa aa GE TEMPERATURE, DEGREES FANRENHEIT BS) MARCH 25 5 | | ' 3 WEEVILS ACT/VE Ses ee ee ee ee See | Wee N45 > 43| UAL EFFACTIVE TEMPERATURE L/NE| | ON | A SS EE Se a NUITBEFR OF | lc Fic. 5.—Chart showing mean average temperature, rainfall, and weevil activity, Victoria, Tex., October, 1906, to 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. Durmg 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 XXXI. TaBLE XX XI.—) | On black land. UU Ge ee ei | Jan. 12 7 6 | Mo 2 a ae Jan. 16 1 50 | 10 weevils in bolls on the same plant. ONS oe eee eed: 2 30 | a ee ae Sie | Jan. 17 4 8 | ee ea. | Jan. 18 1 17 | PE ere es | Feb. 14 1 25 | Upland sprouts not killed as in bottoms. 3 50 | Very dry for sprout growth. 2 Record not kept, though plants were examined. +» 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 demonstr nia the necessity of keeping the records upon this work Scene 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, raimfall, 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 involved 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. Pi more © complete « The senior author desires to express partic alae appreciation of fee 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. 6U.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 = UNF 1LL IN INCHES Piatt AVERAGE TEMPERATURE, DEGREES FANRENHET? . i oi ~ De ss Et |mt ene ay ees es Feminist SO Ma OL es ee ome oem ee 4 =e ee ICE eee een oe iia maeaiaea aa Semen ote reseed onic! ; Host Ce oe ee eo tea earamies ! CP ee Bey eae ieee. AMS a a sa SS a eo "L061 ‘ouns 09 Youre “XO ‘seyfeq ‘UoeuseqrYy UlolJ dos IOUIN puB ‘[[esUTeI ‘oIN{eJedule} OFRIOAB UvEU FULMoYsS weyo—'9 Dlg So eee coo Ii\ _ _ in ~m ik, In (CHES 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 begmning for the period of emergence for that season. CISYLFIWFT SHAZIM SO APEHWNN ft i Se Ee ee 3 SZAON NI TIAN 2 8 3 8 Sem Hiro lia. 7.—Chart showing mean averave temperature, rainfall, and weevil emergence, Calvert, Tex., March to June, 1907. coe mae nnn 3 oS 4 wo ° = SZFHON Ni T7KINI FS 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 SO 0 w w Y a» S @ = KR n wo wo w wo WH SITHADIO ‘SFAH/NLVATIWIL IOVSTIAY NYFW _ Ss 2 EMERGENCE FROM HIBERNATION, 1907. 71 at Dallas the mean average temperature for the month was over 11 degrees above the normal. At Calvert the departure was about the g | RAINFALL IN INCHES MEAN AVERAGE TEMPERATURE, F — ron So ea oo), wm o ieces cn EEVILS EMERGED “ERATOR = | | ! | SSS SS SS EE SS A es a . CASTER Se Se 2 ee a ee v, So Sw on ee -—=—— DIE eee or A SSS SS, PS SE nt ET SS Cen oe ee ! —_——_—— 7 as Me (Hie eS oP eee | ey | —}—} _| aa ————_—— ' = = eeeeh | owt taal) aes au S=sSc5 5) aay coe ‘iilease aie | I “2061 ‘ouNnL OF YOUVAY “XO, ‘BOJOTA ‘ooUSFZIOUIN [TACOAA PUB “[[esUTVI ‘oINGVIOdUIO} OFBIBAG UBEUT ZUTMOYS JALYO—s “D1 aa [ee ames | | ™m Ww oO oO ro) NUMBER OF WEEV/LS E/IERGED 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 72 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 condiiecel 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- | Morita, Depar- mean. ture. mean. ture. mean. ture. | mean. ture. ID allasmer tee ae oe 54.3 —0.6 51.6 +3.8 53. 4 +8. 5 | 51.2 +6.6 Calver(aes seas seen 59. 1 + .1 56.8 +4.1 59.8 +9.6 | 54.8 +2.8 WiGtOTI aS ses see sae 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. TaBLE XXXV.— Mean average temperatures and departures from normal at Dallas, Calvert, and Victoria, Tex., March to June, 1907. March. April. May. June. } | Locality. ; ul ae 7 Monthly | Depar- | Monthly | Depar- | Monthly | Depar- | Monthly | Depar- mean, ture. mean. ture. | mean. | ture. | mean. ture. |} oR, oF, oF. oF. i oP oF. oF. Dallas. 0h. dees s tees 66.7 +11.1 61.4 —4.2 65.8] | —7.7 | 78.8 —1.9 Galvertees oo. eee | 70.0} + 9.2 62.2 | —5.9 | 66. 6 | —7.3 | 76.6 —4.4 WVICTOLI asa. = ee sae 72.4] + 9.7 69. 4 —3.3 73.0 | —5.0 | 81.6 — .6 | } eal acs" ey! ri] 7 ms, --«- EMERGENCE FROM HIBERNATION, 1907. 73 [ne ,. UDhe 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. Taste XXXVI.—General summary of experiments of 1906-7 on emergence from hibernation. Number of weevils— Used “two. | Percent- ‘ sed as i age ONE basis for shed emer- Putin | percent- ia ging. cages. age of ging emer- gence.@ (UE) ies Soe og i SS Se 32, 439 30, 864 3, 464 bee, Oo re UES ot 0S ER a ae 20, 430 19, 408 1, 842 9.49 ot ie Devi 0 BE ee eee ee a 23, 645 22, 463 b 3, 026 13. 47 cst aa eee Ei le ia 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 (PI. 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. ———— SS aw Ve Ss ee eee ee 74 HIBERNATION.OF THE COTTON BOLL WEEVIL. = EFFECT OF TIME OF ENTERING HIBERNATION AND NATURE OF SHELTER UPON THE PERCENTAGE OF SURVIVAL. One of the most important points 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 intervals 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 . : : | Total | Percent-| Rank of When | tion Character of shelter and food. last | number | yeevils | age of |section in started. num- | emer | Of | tal keeioal gal ber. | gence. | weevils. | ee E | Urvival. | SUrvivel. } 1906. | 1907. Oct. 13 1 | Leaves and hay, 4 inches deep, cot- | ton stalksilefte-*--3-2-2) ee | May 21 3,800 99 | 2.61 12 Oct. 16, 4); Leaves and hay; stalks cut and left | |, « COUR AYS 0-2 Ss Cee Re eee ee May 6 2,090 85 4. 07 Bl Oct. 20 2 Leaves and grass 4-5 inches deep; | 710 T00d- ssh es 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 food Gs." ee ee , June 15 2,850 250 8.85 | 5 Nov. 5 | 5 | Leaves and grass 9-10 inches deep; | | stalks cut andJeffie = = es = | May 15 3,135 383 12. 22 4 Nov. 12 3 | Leaves and grass: ro foods ........ | May 21 3,040 448 14.74 | 3 Nov. 13 9 | Leaves 8-10inches deep; green cot- | tonicut andileitg ere ee June 19 3,040 788 25. 92 2 Nov. 15 11 | Leaves 3-4 inches deep: stalks left standing )> 262 35. ee ee June 4 2,565 804 31.34 | 1 Nov. 21 iby Cee dosh eee ee June 8 1,570 65 h4.14 | 10 Nov. 28 | 6 Bare grou, ae 100025. See es ee Apr. 29 75 | 46 4. 72 | 8 olls2‘onsuniace jy. 20 eee = = 3 Bere Gil 40 Wc ies aeica sa aes eee pee \May* 2 S64 39] 4.51 9 Total andtaverave> == et ee 30, 864 3,464 | pA bak (ee oe CALVERT. Oct. 13 1 | Food, two days; grass and leaves | | 4-5\inGhes deep st. sen) eae 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 7 | Spanish moss; chips22. = 2 -. 2222 July i Zsato 105 4.42 6 Oct> 31 8 | Food two days; grass and leaves 4-5 | inches .deepe 4.- 2-5) - 2. ee eee | May 30 2,375 63 2. 65 8 Nov. 5 5 | Food dry; grass and leaves 4-5 | inches. deepl 2 eee Apr. 26 2,375 45 1.89 9 Nov. 12 9 | Food cut down, left dry; 10 inches | : eTasSand leavess soot ee eee | June 12 | 2,375 438 18. 44 | 3 Nov. 14 3 | Stalks cut down, left dry; 2 inches PrTassiand lea vessae- eee eee eee May 31 2,375 253 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. 3 107); Bollss. = eee apes Ae en | Mar. 24 (k) 8 | EA fs Se 10 Total and average. .........--|...--.---- 19,408 1,842 | O40 hes 2a a See Pl. VII, fig. 2. b See Pl. VII, fig. 3. ¢See Pl. VIII, figs. 1, 2. d See P1]. IX, fig. 1. ¢See Pl. IX, fig. 2. f See Pl]. IX, fig. 3. 9 See 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. eee Bul. 77, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE VIII. 1 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. ) — sahen awe rn y hy ial Scene ye ti ” i , ew main tee ow ean ire SS . Poe apne ’ } Bul. 77, Bureau of Entomolo gy, U.S. Dept. of Agriculture we . “iL Sg Peak ev TS. re PLATE |X. SHELTER CONDITIONS PRODUCING AVERAGE SURVIVAL AT DALLAS, TEX. Fig. 1.—Section 8, started October 30, cent. Fig. 2.—Section 12.22 per cent. Fig. 3 survival, 14.74 per cent. Original. ) 1906: emergence ceased June 1), 5, started November 5, 1906; emergence ceased May 15, 1907; survival, Section 3, started 1907: survival, 8.85 per November 12, 1906; emergence ceased May 21, 1907; ———— EMERGENCE FROM HIBERNATION, 1907. 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 Mate PCE. hy re oe When | tion Chetan Sahelian: last number ek ahaa Rank of started. | num- iaracter of shelter and food. anata of weevils age o section in | gence. | weevils. emerged. | survival. | survival. 1906. 1907. Oct. 25 1 | Weeds and grass 5inches; stalks left. May 11 2,375 201 &. 46 7 B30... 4 | Weeds and grass 5 inches; stalks HW lvga(0)\'62)6 bes ee Sa ee May 15 Zyat0 | 105 4.42 9 Oct. 28 2 | Weeds and grass 4-5 inches; stalks “Ui pl ge May 11 2,375 | 134 5. 61 8 Nov. 6 7 | Moss, bark, chips, ete.; no food.....) June 15 2,850 | 674 23. 65 l Nov. 10 8 | Grass and weeds 5 inches; stalks PENT OGL te wee ein rata a arse ats ule me 6 May 6 2,850 362 12. 70 6 Nov. l4 5 | Stalks pulled, left; grass and weeds ERTL erin a es © Soe oe eae Apr. 28 2,850 449 15. 86 3 Nov. 21 9 | Grass and weeds 10 inches; stalks hohe Me vee Uy (:) 1 pS ee May 23 2,850 374 13.19 4 DBDs: 3 | Weeds and grass 2 inches; stalks | Moledand left. .t. 2... eee. LES(s Koh tue 2,850 588 20. 63 Z Nov. 28 6.) Ground bare; no food.............. | May 11 1,088 139 12.78 5 Nov. 29 ROMMMSGUS Ne. fo ite coi ant acc cce we ol Mar. 4 (a) ON ee see 10 = “steel | abemeiee MGual ANG BVETASS........----|---.-0---- 22,463 3,028 | 1a Gl ere ee 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. VII, 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. ——— = Ja 76 HIBERNATION OF THE COTTON BOLL WEEVIL. TaBLeE XXXVIII.—Comparison of sectional records grouped by approximate initial dates. Basis Rank in : Total | Percent- Date. Locality. Section | number | number | age of ne ae emerged. | survival. | Bea 1906, | Ooi Naa ID alas tie. S285 be ee aie eee ee 1 3, 800 99 2.61 Dor iCal verbo = or ieee me nee ee ne aaa 1 2,375 75 6-15 | 8 @aty 16,| Dallas’..2 20 oe 5 ee aye epee eae aT ae 4 2, 090 | 85 4.07 Total: and averave: 7 soc oe eee ae ee eee 8, 265 | 259 3.13 Orie 19 | \Calverts..7-p2e ee ee ee PG et 7 eines «5 ag or Ort =20)| Dallas: :2 Joe) toe, We ieiae eee Seer 2,|. '3,610 2% 6. 26 } 7 Pe SS EL) PNAS eas 2S J a | eee ee Totalian disivenrare.s vss) soe eee eee a 5, 985 342 Seyi Mero. | Dallas ced. se een! seen aeons eee ; 7| 3,325 | 231 6.95 Oeve Jo: |) Calvert. wee tee ae ee een ee ee 7 2,375 105 4. 42 Moe-6 | Victorian. scar eo oe teen eee 1 2) 375 201 8. 46 5 Does re OSLER A Ase ee eee 4| 2,375 105 4. 42 Totaliandaverage:.<- 3323-6 See ee 10, 450 642 6.15 OE 98.) Wictorials ence. abet le ee 2| 2,389 | 134 5.61 OCH S0)) | AD all as ere eo ee ee te ee cere eres 8 2, 850 250 | 8.85 | 6 Ochoasls | Calvertst oe. ae ase ee eee pect ne eee 8 2,375 63 | 2.65 | Totalandiaveragece seccen ss. e5 a6 =| eee ee 7,614 | 447 5. 87 | Nogigha| (Dallag cw tana, Remo amen see BoP tald35 383 | 12.22 | Do Calvert. 22-02 eee op oe eee eh cee 5 2,375 45 | 1. 89 4 INOW enO) | VAC LORI A eter cit neler ee ae ee ele i 2, 850 674 23. 65 Total and averages 22-0. heehee | Senet 8/360: |())" Peip2) |e" aaras INOive el OVI CLOT sens eases tee eee eee 8 2, 850 362 12.70 INOW. ele Dallas 6 eo ea oe eee = ete eee 3 3, 040 448 14.74 INOWsel4e | Calvertesss. i. 0. oo ae aac eetice ceils 9 2,375 438 | 18. 44 9 INOSV Ay lia el) SU AS ere re ee nr e re eeee e ee erere 9 3, 040 788 25. 92 Ona de! |) WAGON Bee as ooo ae AR an oea setae ssbossetooe 5 2, 850 449 15. 86 INOVWE IDA) IDPIIER Ja sScan teebn6acus bos asescouessee= 11 2, 565 804 | 31. 34 Total andjaveraper- ces es. .6 es eae -5| eterno 16, 720 3, 289 | 19. 67 | NOVEROtDallase 2 2..30t oe ee eee oe eee ee 12 1,570 65| 4.14 Do. WACTOLIA: Sones Sere ae ee eee eee eae 9 2, 836 374 13.19 3 IDS s\P oes Oe eae ete eer oe 3 2, 850 588 20. 63 | MNotaltandiaveras elses eae ene ae eee 7, 256 1,027 614.15 INOW 250d CalWert=-ce2ccres ca. Se See oe ieee. 6 1, 425 359 25.19 INOve 26. |e Co ees eee Ue ee ee eee 2 1, 358 380 |: 27.98 1 INOW 28) |e Dallas. 23 Sono. Bea ee eth cestcle eee orate 6 975 46 c 4.72 Do WVAICTONIGS A aches nee eee se Se eee mace 6 1,088 139 | ¢12.78 Potalvand averagesesrs a2 sees | eres 4, 846 924 | 419.07 | | 2 Brownsville, Tex., weevils. 4 Teor eas nme ah ae 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. 7 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: a TABLE XXXIX.— Maximum hibernation period and percentage of survival by sections, 1906. DALLAS. Number | | | Date of : eet || LLSC Gl) 2S pas Total Percent- Section number. ‘ en Wes rf basis of ay | weevils age of Tak a hala al percent- Saas |emerged. survival. : gence. | age. 1906. 1907 ey eee dee a | Oct. 13 4, 000 3,800 | May 21 99 | 2.61 boat Se ie eS RS a ee 1 Oct. 20 3, SOO 3,610 | May 19 226 | 6. 26 mre Pe Ae ke - | Nov. 12 3, 200 3,040 | May 21 448 | 14. 74 cl Sel, lll Ae SE ea nn ne ce a Oct. 16 2, 200 2,090 | May 6 85 4.07 De Mh oe ne oO ee Nov 5 3, 300 3,135 | May 15 383 12. 22 Uo ue Co oe SS ae a ee es Nov. 28 1,025 975 | Apr. 29 46 4. 72 Cd sa EL ed ee Oct. 24 3, 500 3,325 | June 17 231 6.95 on a Le Sale on ee Oct. 30 3, 000 2,850 | June 15 250 8. 85 Ui LD ME? Se: COE aie eee ee Nov. 13 3, 200 3,040 | June 19 788 25. 92 EE eee! Ti el: Dec. 6 864 864 | May 2 39 4.51 RM ee Pd Nov. 15 2, 700 2,565 | June 4 804 31. 34 Ce es ee ee ee ee Nov. 21 1, 650 1,570 | June 8 | 65 4.14 MOLAN SUG AVOPACG.: 0. lk... -- ee | eee 32, 439 30, 864 | seranatre ote 3, 464 11. 22 78 HIBERNATION OF THE COTTON BOLL WEEVIL. TaBLE XXXIX.— Maximum hibernation period and percentage of survival by sections, 1906—Continued. CALVERT. | Number Datoof : used as aos Total | Percent- Section number. ees Weave | basis of foc weevils age of ra * | percent- gence emerged. | survival. | age. — — 5 —EEE 1906. 1907. 1 12 ON an Sea, Se.) tee ES Sg Oct. 13 2, 500 2,375 | June 12 75 2.15 Re Mk ag PALS A ce Sh RE OR, NOM CREE Nov. 26 1, 480 TS S08) en Ores 380 27.98 et Or Be Soe ca ea Leer a en Nov. 14 2, 500 2,375 | May 31 | 253 10. 65 Ub A eee Ae RE ery Ferm eo by Oct] 19 2, 500 2,375 | May 30 116 4. 88 Py i tse tees Se ee oe ee ee Noy. 5 2, 500 2,375 | Apr. 26 45 1.89 GUS EES. SSE ie Betas Se a ere Ae Os So eee Noy. 25 1,500 | 1,425 | May 16 359 25.19 1 fae ES a RE eT SI ee mee aE Och, 25 2, 500 2 Sfo| lye at 105 4. 42 Sere oa NEE 8 oe ee ee sae ee Octirst 2, 500 2,375 | May 30 63 2. 65 Ot eee oe aye Sea eeuet eee ee eee es Noy. 12 2,500} 2,375 | June 12 438 18. 44 0), Meme Mee er eae aE AES AS An iets 2 Dee. 3 Bolls. | (a) Mar. 24 8) ee Totaland-averagess2* == a. oer ee ee eee 20, 430 1OS408 Set eet 1, 842 9. 49 VICTORIA. J, ME ee Nee cits Sime Sti aoe on aes ee Be Oct. 25 2, 500 2, 375 | May 11 201 8. 46 See ee Taek FEO 028 ole ey pea Oct. 28 2,515 D388 Edessa 134 5.61 Be SS ee ee arene i SRE Py Se Noy. 21 3, 000 2,850 | May 23 588 20. 63 SPAR ee oes ake We Ste cs Sh eee MR a Oct. 25 2, 500 2,375 | May 15 105 4. 42 ee Tt SoS a a pe ge he Same) ae ce Noy. 14 3, 000 2,850 | Apr. 28 449 15. 86 Ger eras Ae entries ae oe Sen Screen Nov. 28 1, 145 1,088 | May 11 139 12. 78 UfhA is 5 ch AN ORs SRE RI aes SRM Dp) yy tO Nov. 6 3, 000 2,850 | June 15 674 23. 65 Ch a. A SA a ey me RT ae oe ea ea, Nov. 10 3, 000 2,850 | May 6 362 12. 70 O RN Ret ee uae ios ic eats eae ee Nov. 21 2,985 2,836 | May 23 374 13.19 i ety ee 5 el 2 YL oe ee Nov. 29 (0) (0) Mar. 4 | Dik. meee Motaleandiayverages <5. eer se ee eee O35 645: |b 122,463 4| eee eee | 3,028 | 13. 47 ; | | a No estimate made. b Three bushels of bolls on surface and 3 bushels covered with earth. 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. 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. TaBLE 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. Wweevilsemerged.| fe A eeas ats = : ; Total Locality. | | | emer- a Ol alice | Per Z Reta tne Per gence. vl goe cent of | eas cent of Alum cent of | Bune cent of Z total. | eal total. ste total. . total. ia | | igasos as CU Us ee eee 2, 486 71.8 | 484) 14.0 52 13.0 42 1.2 3, 464 MERU E en ne ce! one 1, 053 Syn 410 | 22.3 284 15.4 95 77 1, 842 RETA Eth is Sere ee cre eS, 2, 399 79. 3 | 476 it 7 119 3.9 32 L.1 3, 026 Total and average. .... 5, 938 71.3 1,370 16. 4 855 10.3 | 169 2.0] 8,382 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. Taste XLI.—Summary of emergence of weevils in cage sections by weekly periods, March 1 to June 20, 1907. DALLAS. Number of weevils emerged in section num ber— Weekly period. a ae ae ain eS ale 2 | 3 | 4 | 5 6 ‘ 8 Oo: 71) 440 11 12 ————————— py Sa | 1) ES Aas ia 40/ 69] 155] 36] 151 21 73| 79] 212 1D ix, eee 1S co ee aes hee OES Ben 84), "S64, sep) 10| 46 Vl 2b Vah-ieie0 es 7 Mart haob 22 oie res Sere 17 39)| ° 85 11 89 11 64| 35] 202 13 | 145 10 Mar 20-08. Joe ence 10 21 38 Si) 5 2] 25) 2 etes 4) 189 11 Maro 29=Apr 4... een: 4 20 19 3 8 1 4 15 7 1 49 4 PATA La: Sot bee eee 7 13 | 30 7 10 Soleo tsa 10 17 1 78 11 Apelea18- 05 bees 1 6 12 i} 7 0 8 5} 10 0} 55 6 TING) 2h ge 1 5 8 0 1 0 2 3 6| 0 15 0 Apr. 26-May 2............- 5 10 16 3 5 1 2 20 Ste ay 27 1 Mista 0 Sa 2 techn e anes 2 SA 2 3 7 0 7 14] 26} 0 40 6 MayglO=16-.05. ) ia eee | 2 2 10 0 8 0 2 Tle 329 0 58 3 May R095 20 22> en nee eee 2 2 3 0 0 0 8 3 16 0| 67 2 May 4280's 2a. 2 eee | 0 0 0 0 0 0 0 3 4 0 12 1 May 31-June 6............. 0 0 0 0 0 0 1 2 4} 0 4 2 JUNC el Sheet e eee eens 0 0 0 0 0 0 1 tt) 3 | 0) 0 1 MEN 4=20 204 (See BOR ee eee eee ReSeeael bra ee tees Bs Sl bash boone tis 2 1 1 let cb ee eee —— ———— eee) EES ee Titel es ty ee 99 | 226 | 448| 82| 383 46 | 231 | 250| 788| 39] 804 65 CALVERT. [MIE ey an a a a 25 99 54| 23 15) 1362) OPS eae 49 fl ee Ber Mar ARI ae 8 ek 9 39 | 23 10 6| 47 4 A NT Viel aaee ae Mar Gov Si Po ei 9 54| 37 12 9) 45 2 3| 55 7 ease hy (RSE Tn Mar, 20-08W!o (ote ., FZ u a: i 41 | ~36:| 22 6h 5G) eben ad 50). eat ee ae Mare 20[A pr: 4s ee Dan 18 4 An) SDDS 5 47 ie Peres ee Apr te eee 0 14 9 7 3| 21 6] 11 44 i ene ae INDY gO 1 88 ee ye ee ES Sil a2Set eos. 9 1 16 6 2 (kee a [sc (age Bee pre ooob eee alee 2 6 3 1 0 6 1) "2 EB Waa Vg eee cae (aE Ap En2G—Miays2 ee bee ee: 2 9 9 6 1 3 5 Oy UD ae eee Mayan 98 fess Santee eee Shim ede ae ees 16 0 3 5 7 BO PONG ec pees MayMO-IGbs 25-2220 ee 1 12 9 2 0; 3 7 nee Si ya oer 1 top | (a Mayeii=o58. 2 8c 2 i eed 5 17 6 2 0 0 Salers 13 el Pee es peed May 24-30....-.....-- asec 1 8 2 2 0 0 16 37) 2A. Os | ees May ol Junel6n sees 0 3 1 0 0 0 16 0 10 | OS (peak 8 GSE ee AfitoVs) YONG}. Se eee seen cue as 1 3 0 0 0 0 4 0 | 7x Ue ets (Sse See ives) Ih Ue See earns 0 0 0 0 0; O by 200) 20 el rs eee [ee UNG 21 pe ries. Se ees Sole oe loa oe | ee ee ee eee | eee Saectose Seen ee RE eRe ae PtMeN2S— Ml yok se oe SS eee Re ee | were | eee at me oe 1 eee = sescesleuke kc aes oe Motal ces: eet pee ens 75 | 380} 253} 6} 45) 359) 105) 63 1, -@88\) Se) ate ee | 1 ! VICTORIA. a ae a ed | Aes] = a Lae = | Hebe 28en pakke etn mas 39 24 69); 13] 60) 35] 29) al i a eee el fe Se eae Marlee aes muse © aac ns I B21 235) P95 a = 90 | os80 hie 120s ee COMM ODM mere 2r Seae Mar) S-lae sas oot ees | 54 36] 130] 22] 103 24/ 63 107 76 Ob. 28 Races Maral sola: eens | 36] 18] 94 19| 88| 25] 124] 72] 67 Oe ot ee Mar g00-08 gue Eee ee | 18| 10 54 13°|' (58 18} .170| 26 30 0: ete. ee Mar 20 DL. ce se eee ea 9 | 6 51 Oh 21) ab) eeelo 15 16 OMe orleans Apr alleen eee i= “S41. “85-44 0} 26; O| 64] 8 12 Uh Riser (i St Apr. A218 soe eee 5 5 | 28 5 Toe a0 a7) Poe eed Oj: eee Ar 10 Oteae meee en | 4 1 ee es 9 ie Ys Pe en ae Rake be Ar 26—-May 24s ee P15) 80 4 1|: .4 0 144; 1 1 by ee (aes 2 MayisaOos mies tse i) oon we 8 o| 0 Of) sah. 3 4 Td ie ree May d0-1Gne tee ae eee oe be eae 1 De OW) EL ye coOF li me 0 Ol cecetl seme May 1709 5 oe ee ae 0}; oO 1 0; o| oO 14; O 2 One meclessees Mayr24-30 ye peer 0 0 0 0}; oO 0 Boe ath 0 Quine ater May 31-June 6.......-..--- Oss Or Fa8 0! oO 0 Ai <0 0 Ty aerated Wis |v" TUNES 1 ae te ae eee 0| 0 0 ol o| 0 241) PEO 0 il (ere | (ere Terie 14-90 os Wet ee teins S| eee |e ee Nee perce Niet ke A Feaapepee see ere (ee es (ot SS leeee UM We] £1 Wee eee OY 201 | 134] 588] 105 | 44) 137] 674 | 362 | 374 pA SRE = LE eh EMERGENCE FROM HIBERNATION, 1907. 81 There is no indication that the time at which an experiment was begun affected essentially the nature of the emergence movement. The nature of the shelter, however, does seem to have an important influence. This is most clearly marked in section 7, where the ex- perimental shelter was Spanish moss. At Victoria after about the 12th of April more weevils emerged from this section than from all others combined. This effect was less marked in the other localities, but in each case there appeared to be a considerable delay in emer- gence, due to the nature of this shelter. Owing to the fact that this moss is living and growing while hanging in the cages or on the trees, it takes up moisture as no other class of shelter does. The evapo- ration of this moisture during the daytime then serves to keep the mass of moss cool, and it is a well-known fact that the temperature in bunches of this moss is several degrees lower than that of the air during the daytime. Undoubtedly the lower temperature in the moss is the factor which retards the emergence of the weevils so decidedly. This factor may also be considered responsible for the smaller activity of weevils shown in the moss sections during the winter. (See Table XXXI, p. 63.) A somewhat more detailed statement of the emergence shows more plainly the peculiar manner in which this was distributed during 1907. The figures are arranged for seven-day periods, and show the average temperature conditions prevailing as well as the percentage total of emergence occurring during each week. Taste XLII.—Weekly summary of emergence records, showing relation to effective tem- peratures, 1907. Mean Percent- average | Number | age of Date. Locality. effective jof weevils} total tempera-|emerged.| emer- ture. gence. 1907. | ou Calvertist roa Cray s 30. 0 420 22.8 = ‘ IDE ANG Re ae Se eet iets, eee 19.7 848 24.5 Mar. 1-7......--..---.-.-----------++++++-+- N victoria | oie { a 363 a 12.0 ececiue Shao ea eel 481 15.9 WalVOrheoe et ce ce ae! | PATH 168 9.1 are Pee ee So {Data Sen hy ee eM i SHY 21. 413 11.9 WictOriass sek eS ee | 30.5 609 20.3 1 RSS ie ie ee ee Pes, Soe 30.5 228 12.4 Join Riv Pes eS ier a ee es {Pals fo RO te eng ee 27.0 721 20.8 NUNMACLONMGz Se tans Oe as 5 29.0 049 18.0 MOAIVODE a cc et ere. He. 2 36.6 237 12.9 PT Pr EE oy fT oe ee {Dalla lsc Jah iar side SEN RE ARSE hn 33.0 04 14.6 WLWietoria: £0202 Je te O20 04] 397 ale fat |fEalvert See ee ee phe 23.0 | 128 7.0 Oo SUL opt es ie a TD) ASP ee os ope a Te oe 17.5 | ibshs 4.0 eat ae ae oe ae 22.8 | 147 1.8 Calvert At te seus swe eee | 28.8 115 | 6.2 See ae ee ee EVAL LASS tot eyes ooo Peerp tn AS ay: 24.0 | 194 5. 6 Wietoriac 2:28 o¢tbo con 31.9 165 | 5. 4 Calvertwer ss ak 25 fe oe 24.9 134 rhs: 2 SUA a ee ee Dallasi suerte Fi ee ae ee 20, 0 | 111 5. 2 Mipheyrcts (et 9 Sasaamunlee ata anaa es 28.7 127 4,2 CALVELt sae oe ice oe oo ee st 17.8 33 1.8 os I ee 2 ee ee DSSS ee eh he ee apes 13.0 14 io l\ ICLOLI eects Sea eee os 19.0 37 Mees ME ald ad Se epee ie eae 24.8 | 58 | 3.1 So Lek I gS ge DEE 2 oe eee ee tee Dee es 16.3 | 99 | 2.9 l Victoria eee ae RES 26.3 26 .86 a On February 28. 90317—Bull. 77—09——-6 SE A a eae ee 82 HIBERNATION OF THE COTTON BOLL WEEVIL. TasLte XLII.—Weekly summary of emergence records, showing relation to effective tem- peratures, 1907—Continued. Mean Percent- average | Number]! age of Date. Locality. effective jof weevils) total tempera- | emerged. | emer- ture. | gence. 1907. | | om, Calvert... 2): 55.052 ese 26. 4 113 | 6.1 DLA Da. AS ee. SE ee eee Dallas. Joh os tee 20.2 129 | 5 By | Wielorias.. 2 eee 29.3 50 | 1.6 (Calvert... : 52% 8) 2ce Cee 31.9 59 | 3.2 Way 10-16 290 20 eee ee Data Sa ae hen ee el 24.0 121 | 3.5 |(Victoria..-...............-..| 32.5 26 | 86 {Calvert Se) eee et oe | 35.5 54 3.0 [LES fl 203 ne Se od EO ere Weh ey Pi eDalbicy 3 ec lee 31.2 | 103 3.0 [Victoria a ae MODE Sao, EE eS 31.8 | 17 . 56 ‘Caly Cliee s-s eho ee 33.0 49 2.6 ERY OBO ee a Te ke a cer et Dallas (ha ea: Sie ee eee 23.3 | 20 -6 NaCtGnia 236) eee Pe ee 33.4 | 8 . 26 | (Galivente- see 220s ee 30.7 30 1.6 May 3 Jiimne 6. < oo. 2- 2226 soe eee eee 1D EAU Epa le Nie Sed oF eas 38. 0 13 4 | Victorias. 00-22 oe eee 30.9 | 21 “| N{Gatyertia= sh ie aes. 43.2 | 10 5 JUNG N= loss. Se a es eee Dallaso = Ae ee eee 38. 0 5 aD Victoria=:< 2232425 tae 40.0 | 2 - 07 Calvert et eens: Sees 7.4 5 a3; afb h a (eta: E22. | een aren Bee eae ce A age Oe fn Dallas hves eh Mi See 36.0 4 Ea2 MictOnide sss 4-2 eee ee 36.8 1 . 03 jCalv eTriere so. eee ee ee 39.4 1 .01 ibe a\e 473 [2 / oe en Ske eres ae ee Daitas 7 ae a eee ‘<6. 2 ee eee Victoria-: <3 2 - o se B Se ee e ee Total emergence: Calvert... ..2'- 2s. SBC ce ee ek oe ee ee 1,842 Dallas: Fw A Sct ck eet dk os ee Ey Re © ee ee eee a 3, 464 WiCloria. 26 5 22 ce on Oe ee oe Re in Oe ee er ee ee a 3,026 Grand total. = 222 .2s28 4222S. 68 cok to Pe ee BA ee Se ee ee a ee ee eee 8,332 The large percentage of total emergence occurring during the first week of March is very striking and unquestionably also very excep- tional. Only the extremely high range in temperature can explain this unusual record. Taking the average of the three locations, practically one-fourth of the total emergence occurred during the first week of March. Durmg the followimg two weeks more than another one-fourth also emerged. During this period the tempera- tures averaged as high as they: do ordinarily in May; and owing to the fact that a considerable majority of weevils had left shelter before the end of March the number emerging after that time shows a marked decrease. It must not be supposed that these statements represent anything like usual conditions, although they unquestionably represent the facts in regard to emergence in 1907. The comparison of these records with those for Dallas and Keatchie (see p. 44) in 1906 will show clearly the exceptional nature of the variation. It should be stated that when the emergence takes place as rapidly as was the case in March, 1907, the actual number of living weevils in the field may be expected to increase for some time because of the fact that a larger number of weevils is added to the total living on account of continued emergence than is lost on account of death among weevils which have previously emerged. wr =e § LONGEVITY OF WEEVILS AFTER EMERGENCE. — 83 LONGEVITY OF WEEVILS AFTER EMERGENCE FROM HIBERNATION. Preceding records have shown that on the average the weevils sur- viving hibernation had lived for over five months before their emer- gence. It is impossible to determine even approximately how old weevils may have been at the time they were placed in the hiberna- tion cages. The longevity records here shown must, therefore, be very conservative. They may indicate very closely the average length of life of weevils which survive hibernation, but should not be considered as showing actually the maximum longevity. It has seemed advisable, therefore, to base the studies upon longevity after emergence from hibernation, since the exact dates for emergence and for deaths have been carefully determined. As the weevils were collected daily from the cages, those found at each date must have emerged practically upon that date. It was the general practice to divide the weevils from each section of the cage into two lots of approximately equal numbers, one lot being placed in a series in which they received no food and the second lot being placed in a series which was supplied whatever stage of cotton was then available to weevils in the field where the experiments were being made. Thus, early in the season at Dallas, all weevils were necessarily placed in unfed series, since no cotton existed in the field. In each locality the first food consisted of the tender leaves of volun- teer or sprout plants. As soon as squares were formed in the field these were supplied to the weevils in the fed series of experiments. As a general rule the weevils emerging upon three consecutive days were placed in a cage bearing the same series designation, and the average date of emergence was considered as applying to the entire lot. This arrangement was necessary to reduce the amount of work required in caring for so many cages as would be needed to keep each day’s weevils entirely separate. In both the fed and unfed series frequent examinations were made to determine the time of death of each weevil, and fresh food was supplied to weevils in the fed series. Upon the death of a weevil its sex was determined and its period of life after emergence was also recorded. The manner in which sex can be positively determined is described in succeeding paragraphs. (See p. 91.) In this way the records for each lot bearing a serial number were kept by themselves and the results for each series are comparable with all others. While it would be most significant to present the records in the form of a summary of each series which would allow these comparisons to be seen, the necessity for abridging the tabular matter, so far as may be possible, prevents our doing so. Therefore for both the “unfed”’ and for the ‘‘fed’’ experiments we can give only the grand totals and averages with general statements based upon the tabular studies from which these figures are obtained. 84 HIBERNATION OF THE COTTON BOLL WEEVIL. LONGEVITY OF UNFED WEEVILS AFTER EMERGENCE FROM HIBERNATION. Since the duration of life of unfed weevils was so much shorter than for fed weevils, the records of the former will be considered first. The principal object in the experiments with unfed weevils was to determine the time which they might survive while waiting for the growth of a food supply in the spring. The results have a most important special bearing upon the advisability of hastening or deferring the time of planting of cotton, especially when considered in connection with the period of emergence from hibernation. The figures given are based upon completed records only, all partial records having been discarded. Taste XLIII.—Longevity of unfed weevils after emergence from hibernation, March to July, 1907. : A : 2 Weevils in series lots. | Maximum life. | Average duration of life. Number Pes Totaly i|iese ees re : Locality. uf ea weevils ae ke — unfed. emerged. Total. rea 2 Pot Q 3 Q | eae Texas: | Days. | Days. | Days. | Days. | Days. Calvert-:.._- 25 1,085 1,079 585 494 | 48 26) |. 8505 8.09 | 8. 07 Dallas. == 19 ArOsial, 2a Onl, cL Sele OCoR| 90 88 | 13.00] 11.09 | 12.50 WVictoria-= 4. 17 1,418 1,360 875 485 | 44 40 8. 00 7.40 | 8.20 Total and | | | re average . 61 4,820 | 4,618 | 2,638 | 1,988 90 88 | 10.30 9. 80 | 10.10 The records both for maximum and average duration of life are very important. In the record showing maximum and average duration of life for each sex in each locality the time at Dallas exceeds by 50 per cent the time at either Calvert or Victoria. It should be stated that when weevils are kept in confinement it is probable that the most favorable conditions which can be furnished them can hardly be sup- posed to prolong their life beyond the normal condition in the field. Any unfavorable conditions in the cages will shorten the period. It was found in the course of the work that whenever sunshine was allowed to strike directly on the lantern globe breeding jars in which the weevils were for the most part confined, the heat and excessive humidity generated within the globe caused an abnormal activity among the weevils, and if prolonged or frequently repeated, it resulted in their early death. It was also found that in the breeding cages among the unfed weevils the degree of moisture was less than would normally occur on plants or at the surface of the ground in the field. This dryness also naturally shortens the life of weevils. In an experiment at Dallas series 14 was kept with plenty of moisture while series 15 was dry. Otherwise conditions in the two series were identical. The average life in the wet series was 20.3 days while in the dry series it was but 7.1 days. Other experiments pointed to the same conclusion. D LONGEVITY OF WEEVILS AFTER EMERGENCE. 85 These facts indicate that the records for Calvert and Victoria are probably considerably below the normal survival period for emerged weevils in the field, and the records for Dallas are at least conserva- tive. The difference in duration of life between the males and females was but slight, but rather uniformly in favor of the males. In each locality the maximum longevity was shown by males. This fact agrees with previous conclusions regarding the relative duration of life of the two sexes. Apparently copulation does not materially affect the longevity of either sex. In this connection it may be stated that unquestionable instances of mating were found among weevils immediately after their emergence and before there was any possibility of their having fed. This was of rare occurrence, and the question of fertility resulting was not positively determined. From the records it becomes evident that many emerged weevils may survive from six to twelve weeks without food and that the average survival for all weevils may be between one and two weeks. \) There is some evidence to show that it is possible for these unfed i weevils to move rather extensively in search of food, and undoubtedly q this is done in many instances. Other observations, however, indi- cate that if food is not found in the vicinity of emergence the weevils may become quiet for a considerable period before again seeking food, and in this way their movement may occur only through compara- tively short distances. It is also probable that when they first find a food supply they do not intentionally leave it in search of other plants which may be in a more advanced stage of growth. As to the proportion of each sex among the weevils surviving in these experiments it appears that 57 per cent were males. The maxi- mum longevity of any weevil was ninety days. This was a male which was kept under outdoor conditions from March 1, when it emerged, to May 30, when it died. The maximum life for a female was eighty-eight days. This weevil emerged April 25 and died July i) 20. The average temperature under which this lot of weevils was kept ranged between 45 and 60 degrees and the average length of life | for all of the 55 weevils tested in series 17 at Dallas was slightly more , than thirty days. This emphasized the important effect of tempera- ture upon the period of survival without food. The grand total for average duration of life shows 10.1 days for more than 4,600 weevils. The males lived on an average one-half day longer than did the females. if It would be both interesting and valuable if the records showing a I summary of the results for each sex in each series of experiments could be presented in full. It is thought, however, that the corre- sponding records for the fed weevils have a greater value and it may be allowable to present in place of the full records for the unfed weevils merely a brief statement of the most important facts as to the survival of each sex. | | 86 HIBERNATION OF THE COTTON BOLL WEEVIL. The most apparent fact is that there is a consistent increase in duration of life without food in both sexes in a northern locality, as at Dallas, as compared with a southern locality, as at Victoria, while Calvert occupies an intermediate position both in the starvation period and geographically. Lower temperatures are obviously directly correlated to the degree of activity of the insects and thus determine directly the limit of endurance without food. But in no case is there any very marked variatign between the sexes in the same locality. It appears that practically two-thirds of all weevils died during the first ten days after their emergence. One-fourth of the total num- ber tested lived to between eleven and twenty days. Beyond twenty days the percentage surviving becomes comparatively small, and between fifty and ninety days the percentage for each ten-day period is rather surprisingly uniform. It is very evident, however, that even in a season when the bulk of emergence may occur as unusually early as it did in 1907 it would be absolutely impossible to exterminate the weevil by any possible delay in the time of plant- ing cotton. LONGEVITY OF FED WEEVILS AFTER EMERGENCE FROM HIBER- NATION. The records indicating the longevity of weevils which were fed after their emergence from hibernation have been prepared in a similar way to show results comparable with those for unfed weevils which have just been given. They form the second part of the com- parative series of experiments to determine longevity. The condi- tions of food supply, while kept as favorable as was possible, could not at best equal the natural conditions in the field, although the weevils were evidently saved the trouble which they might have experienced in the field of finding their first food supply. The con- siderations which have previously been mentioned in regard to the effect of high temperature and excessive moisture in the jars when exposed to sunshine apply with fully as much force to the fed as to the unfed series of experiments. Taste XLIV.—Longevity of weevils fed after emergence from hibernation, March. to September, 1907. | Number of weevils in series. | | Maximum life. | Average duration of life. | Number | motay | Locality. of series weevils = SSS - - tested, | omerged fod. y Cugteed Total = O Both | | Cee Oe c + C ¥ sexes. Texas: | Dallass 2.2 tal 998 901 190 411 130 108 38.4 38.0 | 38. 2 Galvert-2--- 26 | 740 | 7k) 363 352 g2 118 | 29.2 30.7 30.0 Victoria. .... 20 1,450 1, 349 785 564 S4 86 15.1 14.2 | 14.7 Total and average .| 53 3,188 | 2,965} 1,638} 1,327 130 | 118 25.2 | 25.9 25.5 | | | | | LONGEVITY OF WEEVILS AFTER EMERGENCE. 87 Only about two-thirds as many weevils were carried through in the fed tests as in the unfed tests. Among the total of 2,965 weevils 55 per cent were males, while in the unfed experiments 57 per cent were males. The average duration of life shows but very slight variation between the sexes, both living between twenty-five and twenty-six days. This average is somewhat smaller than has pre- viously been obtained in similar experiments, and this is probably due to the greater exposure to sunshine of the cages in which the wee- vils were kept in this series of experiments. The average period of life with food was about two and one-half times that without food. Among the fed weevils, as among the unfed, the longest life occurred at Dallas. This also was a male weevil which emerged from hiberna- tion on May 6 and survived until September 13, or one hundred and thirty days. The greatest length of life for a female occurred at Cal- vert. This weevil emerged on April 11 and died on August 7, having been active one hundred and eighteen days. The full leneth of life of the last weevil dying in these experiments is also a matter of interest. This weevil was collected in the field at Dallas and placed in the hibernation cage on October 16, 1906. From that time until May 6, 1907, it had no food. The period from its collection until its death lacked but a day or two of being eleven months, during three-fifths of which period it existed without food. This is next to the longest lived boll weevil of which we have record, the longer record being slightly more than eleven months in the case of a male weevil hibernated at Victoria in 1903. In a study of the emergence movement and of the duration of life of fed weevils by ten-day periods we have used the total number of weevils of each sex observed in each locality as the basis upon which we have determined the percentage of mortality occurring in each succes- sive ten-day period. The full records for each locality have been omitted and only the totals for each sex in each locality have been included in Table XLV (p.88). The emergence from hibernation was distributed through four months, or slightly more, in 1907. A study of the omitted records shows that, as a rule, the weevils living longest emerged at approximately the middle of the emergence movement. It is probable that these weevils were among those which entered hibernation at the most favorable period during the preceding fall and that they found also the most favorable class of shelter conditions to protect them during the winter. The importance of breaking up this succession of conditions, so favorable to the survival of weevils, their maximum length of life, and, consequently, their greatest inju- riousness, need only be mentioned to be appreciated. That early fall destruction of stalks, the cleaning up of rubbish which might shelter weevils most favorably during the winter, and the early planting and uniform planting of the crop are all logical parts or steps ne A ce 88 HIBERNATION OF THE COTTON BOLL WEEVIL. in the rational method of fighting the boll weevil is plainly shown by these studies. Taste XLV.—Comparison of summaries for longevity of fed weevils, by ten-day periods, in each locality. MALE WEEVILS. Weevils dying within a period of— Number t Locality. atacavic lace days. | 11-20 days. | 21-30 days. | 31-40 days. | 41-50 days. | 51-60 days. in series. | ee ae Num-) Per |Num-| Per Num-| Per Num-) Per /Num- Per Num-| Per ber. | cent.| ber. | cent.| ber. | cent.| ber. | cent.) ber. | cent.| ber. | cent. Dallas es 5 Son 2 490 47 | 9.6 72 | 14.7 SH Wile 68 | 13.9 87 | 17.7 47 9.6 Calvert. 22222... 363 86 | 23.8 61 | 16.9 60 | 16.7 50 | 13.8 49 | 13.5 41 11-3 Vietoriae 2! 7. 7851 (371) 47.3.) " 216u 27. 6 IBN T4284) 5 392 Seo 140}. 18 13 Nay, Totaland apenas: 1,638 | 504 | 30.2 | 349 | 21.3) 263) 16.0] 157] 9.6) 150] 9.2) 101) 6.2 | | FEMALE WEEVILS. | ‘ AAS Sos 2 411 BPA ss 54} 13.1 91 | 22.1 46 | 11.2 91 | 22.1 37 9.0 . Calvert ...--2..- 352 67 | 18.8 GS elven 60 | 16.7 58 | 16.3 54 | 15.2 32 9.0 3 Wictotians ss 564 | 293 | oe Oh Ss e2se5 SS) (715.6 24404. 3 Lt, 280 104 as ’ Total and | | average. IBSPY/ | 3923) 29559) 250") 18.8)" 2398] 18200) 128) | 9-6.) 5 16a doz 79 5.9 WEEVILS OF BOTH SEXES. Total and average, 2007... 896 | 30.2 | 599 | 20.2 | 502 | 16.9 | 285 | 9.6 | 306 | 10.3 | 180 | 6.1 | MALE WEEVILS. Weevils dying within a period of— Locality Number | 61-70 days. 71-80 days. 81-90 days. | 91-100 days. see in series. Num- Per Num- Per Num- Per |Num-!| Per |Num-) Per ber. cent ber cent. ber. cent. ber. | cent.| ber. | cent. ID ALE Cee Ses 490 36 Usa: 31 6.3 5 1.0 1a\ leo 2, 0.4 Calvert.-2-.2.-: 363 7k 1.9 6 ety, 2 1.6 2 6 One = WiCTOnI AE ee 785 4 5 8 1.0 3 4 Ona] ee ee ee Total and average. 1, 638 47 2.9 45 2.8 10 6 9 6 2 1 FEMALE WEEVILS. WD allaseeeee -f. =e 411 32 7.8 | 22 5.4 4 1.0 1 | 0.2 | 1 0.2 Calvert—- =o 352 9 25 3 8 5 1.4 2 | 6 | 1 =o Victoria---.---- 564 4 stk | 1 2 1 2 Uy ae ie | 0 |.----- Total and average. 1, 327 45 OC 4a 20 2.0 10 8 3 =2 2 1 WEEVILS OF BOTH SEXES. Total and average, 2,065... 1 ii92 3.1 | 71 | 2.4 | 20) 0.7)". 12 | 0.4 | 4 | 0.1 ak ee ee ee + ed | {a "a: aes ae ¥ i te" "s - LONGEVITY OF WEEVILS AFTER EMERGENCE. 89 At Dallas the number of weevils surviving for two months or more amounted to 15.6 per cent of the total number observed. Prac- tically 50 per cent of each sex survived for more than six weeks. At Calvert 15 per cent of the total number of weevils survived over fifty days and 50 per cent for more than thirty days. The average life at Calvert was nearly ten days less than at Dallas. It is very noticeable that those weevils which lived longest at Calvert emerged during about the middle of the emergence period. The weevils which were very late in emerging survived for only a short time. The decrease in the percentage of survival is markedly regular from the first ten days to the end of the period. The most decided decrease occurs between sixty and seventy days. i The maximum longevity at Victoria fell considerably short of i that at Calvert and Dallas. In this case 15 per cent of the weevils I! survived beyond only about twenty-five days and nearly 50 per cent died during the first ten days. The reason for the marked shortening of life at Victoria was undoubtedly the greater exposure to sunshine of the jars in which the weevils were confined. This comparison shows that length of life uniformly averages longer in northern Texas than in either central or southern Texas. \) At Dallas 3 weevils, at Calvert 1, and at Victoria none lived more }) than one hundred days. At Dallas 11 weevils, at Calvert 5, and at | Victoria none lived more than ninety days. From the grand sum- mary of the records in both sexes it appears that among approxi- . mately 3,000 weevils 50 per cent died during the first twenty days. | Two-thirds of them died in the first thirty days and three-fourths of them in the first forty days. From these records it appears that any kind of a food supply will serve to maintain a majority of the emerging weevils for more than three weeks. This consideration has a special significance in southern Texas, where sprout and volunteer cotton usually occur. This sub- ject will be further considered in the relation of hibernated weevils to food supply. -a 7 7 | BEARING OF OBSERVATIONS ON FED AND UNFED WEEVILS ON THE POSSIBILITY OF AVOIDING DAMAGE TO COTTON BY LATE PLANTING. One of the most important features of the experiments on the long- evity, with and without food, of weevils that have survived the winter, is the bearing that the results have on the theory of late planting of cotton to avoid damage. This theory has been pro- pounded by numerous persons ever since 1895. In the series of experiments with unfed weevils 4,600 individuals were used; in the series with fed weevils 2,965. The unfed series is the more important with reference to late planting, The maximum length of life of the unfed weevils emerging in February, 1907, was ’ 90 HIBERNATION OF THE COTTON BOLL WEEVIL. 14 days; the average 6.9 days. The maximum of the individuals emerging in March was 51 days; the average 16.9 days. For the April-emerging weevils the maximum was 46 days; the average 21.2. For the May-emerging weevils the maximum 33; the average 15.8 days. Of the June-emerging weevils maximum 12 days; the average 7.4. It will be seen that even in such an abnormal season as 1907 weevils emerging any time during the month of May might be expected to live for at least 15 days and individuals emerging at any time during the month of June to live for more than 7 days. It is thus clear that many weevils emerging in May would survive without any food whatever until considerably after the middle of June and that those of the June emergence would survive in many cases beyond the first of July. It is important to note that a considerable percentage of the emerging weevils did not appear until late. For instance, 10.2 per cent of all the weevils which survived at Calvert did not appear until between May 10 and June 6. At Dallas the percentage for this period was 7.5, and at Victoria, 2.38. The observations on the longevity of the fed weevils also has a bear- ing on late planting, since there is always some volunteer cotton around seed houses and elsewhere that will be found by the weevils. The maximum length of life of the fed weevils which appeared in February was 47 days, the average 45 days; of March-appearing weevils the maximum 93 days, average 45.5 days; of April-appearing weevils maximum 82 days, average 46.5 days; of May-appearing weevils maximum 86 ‘days, average 55 days; of June-appearing weevils maximum 46 days, average 37.8 days. The longevity of the weevils emerging in May and June is most important. The average survival of 55 days in one case and the 37.8 in the other shows that with such food as can easily be obtained, at least some of the emerging weevils would be carried over until far into the summer, even if no cotton were planted. The records just referred to are, of course, a sufficient refutation of the theory that the weevil could be “‘starved out’’ by late planting. It has been proposed, however, that the number of weevils surviving to damage late-planted cotton would be relatively so small that such cotton would have a better chance to mature a crop than that planted earlier. In order to test this matter the Bureau of Entomology has conducted practical field tests in which cotton has been planted about the 10th of June. In one season four of these experiments were performed in parts of Texas showing distinct climatic features and one in Louisiana in cooperation with the State Crop Pest Commission. In every case the yield was cut down so severely by the weevils that survived the prolonged period in which no cotton was to be found that the impossibility of producing cotton in that way was fully demonstrated. female weevils without a partial dissection. In comparatively few SEX OF WEEVILS SURVIVING HIBERNATION. Q] SEX OF WEEVILS SURVIVING HIBERNATION. We found it possible to readily and accurately recognize male and species of weevils are the males and females so closely similar in gen- eral external character as in the case of the Mexican cotton boll weevil. It was found that size depended primarily upon the food supply of the larva and that it had no special significance in regard to sex, although it appears that the average male is slightly smaller than the average female. There exists a rather wide variation also in coloration, which also proved to depend upon food supply and age rather than upon sex. SECONDARY SEXUAL CHARACTERS. We are indebted to Dr. A. D. Hopkins, of the Bureau of Ento- mology, for indicating the most strongly marked points of difference in the secondary sexual characters of the boll weevil. The distinctive 6) ea ae eS — SBN ae : SPROPY ah. ae “Sp ¥G/D/U/4— S length 38mm. tip ro insertion /2mm. Q 27 47 7? Aas, 7 J8. n Fic. 9.—Secondary sexual characters of Anthonomus grandis. (After Hopkins.) characters (see fig. 9) are found upon the snout and upon the dorsal | side of the last two abdominal segments, which are normally almost i / | completely hidden by the wing covers. The differences are subject to | some variation but are still sufficiently constant to enable a close i observer to positively separate males from females with the aid of a hand lens. Since these points of distinction have not previously i been published it seems advisable to include them here, as they fur- | nish the basis for the determinations of sex which follow. i Female.—The snout of the female is slightly longer and more 1) slender than that of the male. It usually tapers slightly from each | end toward the middle when viewed from above. The antenne | are inserted slightly farther from the tip than is the case in the male. | The insertion is at about two-fifths of the distance from. the tip of i the snout to the eyes. As a rule the surface of the snout is more smooth and shining than in the male. A slight depression, rather elongated and much larger than any of the other punctures upon the 92 HIBERNATION OF THE COTTON BOLL WEEVIL. snout, occurs between the bases of the antenne. When the wing covers and wings are unfolded the abdomen shows seven distinct dorsal segments. The last segment visible from above in the female is called the propygidium. In the female this covers the terminal segment or pygidium, which can be seen only from the sides. Male.—Snout slightly shorter, thicker, and more coarsely punctured thaninthefemale. The depression mentioned in thefemale is lacking. The antenne are inserted at practically one-third of the distance from the tip of the snout to the eyes. The sides of the snout are very nearly parallel. In the abdomen the male shows eight distinct dorsal segments, the terminal segment (pygidium) not being covered by the propygidium as is the case in the female. In general practice an examination of the snout is sufficient to determine the sex of each weevil. PROPORTION OF SEXES SURVIVING HIBERNATION. The records here given as to the proportion of sexes surviving hibernation are confined to determinations of sex for positively hibernated adults. Taste XLVI.—Serx of weevils surviving hibernation in Texas. | Male. | Female. - | Year. Locality. | Number | Perce2t- | number | Pereent- deter- age of | “ deter- age of cand total ex . | total ex- * | amined amined ggNse oo hiGeveral places 02 4. 5 ae 2 | 269 60.7 174 39.3 1504222 | tCalvert 2-202" Oo Se2 22 ae ee es eee 40 60.0 27 40.0 ODA WAICLOLIAy: 2624.2 <8 5 2b) oe 2 ote en ee 42 66.7 21 33.3 O04 ey Ae One eet els Se ee 2 ee ee ee ee 161 55. 0 132 | 45.0 ROOGE ES eae Goes Eee SS ie te 8 ORs Ea Rp ree ee $4 59.6 57 40.4 1907 Daas Sa eee ak Ae ae = ee ee en eee 1,668 54.2 1, 412 45.8 1907 Calvert: 22222 2.520. Se 3 ee ae eee eee 948 53.0 | 846 47.0 1907 Wietonia e's <6 22 a eee Cee eee 1, 660 61.3 1,049 38. 7 Totaliand Average=-C- se ee oe 4,872 a 56.7 3,718 a 43.3 a Weighted average. While these records show considerable variation in the proportion of the sexes for different localities and during different seasons, there is a uniformity in the general preponderance of males. In the total of 9,000 weevils examined 53.6 per cent were males. This proportion corresponds quite closely to that found to exist among weevils enter- ing hibernation (see pp. 16-17). It is evident, therefore, that the pre- ponderance of males in the spring is not due to any superior power of endurance enabling them to hibernate more successfully than females. Apparently there is little, if any, difference in respect to the ability of the two sexes to hibernate successfully. i a ee ee al Pp “RELATION OF HIBERNATED WEEVILS TO FOOD SUPPLY. © 93 From a knowledge of the habits of the adults it appears that the preponderance of males in the spring is a favorable provision of nature, making it more certain for the sexes to mate and to insure reproduc- tion. Inspite of a number of attempts to obtain a definite answer to the question whether it is absolutely necessary for copulation to occur in the spring before females can reproduce, this point has not been positively settled. There are indications, however, that in most, if not all, cases this is essential. The fact that mating occasionally occurs immediately after emergence but before either sex has fed in | the spring has previously been noted. Unfertilized females at any k season of the year deposit nearly all of their eggs upon the outside of - squares or bolls, where they quickly dry up. No sign of partheno- I genesis has been found. The meeting of males and females is to a : large degree accidental, and during a season when weevils are com- paratively scarce it is likely that in very many cases the sexes fail to come together or the meeting may be delayed for a considerable period. { Experiments have shown that the male weevils do not actively seek the females. They seem to recognize their presence through a dis- tance of hardly more than aninch. The meeting of the sexes depends therefore largely upon their coming into close proximity upon a cot- ton plant. Since the males are less active in their movement than are the females, the value of the existence of a majority of males be- comes apparent. The larger number of males and the more active habits of the females serve to increase the chances for the meeting of the sexes in the spring without materially decreasing the power of multiplication of the species. RELATION OF HIBERNATED WEEVILS TO FOOD SUPPLY. § The relation of hibernated weevils to food supply is an important Be subject, since the reproduction and multiplication of the species de- | pend primarily upon this point. As has been shown in numerous places the emergence period of the weevil practically coincides with the average period in the planting of cotton. The long duration of emergence makes it practically impossible to secure the planting of the entire crop either earlier or later than the emergence period of the weevil. It has been found both from the study of the weevil and from large-scale experiments in the culture of cotton that during nearly every season there is a decided advantage in planting the crop as early as soil and climatic conditions may permit. Too much empha- 4 sis can not be placed upon the fact that, at whatever time the cotton in a locality may be planted, there will be a decided advantage in hay- ing it all planted at as near a uniform date as is possible. It is obvious that this will entirely prevent the development of weevils until prac- tically all of the crop begins fruiting. In this way the fruiting of the ee) 94 HIBERNATION OF THE COTTON BOLL WEEVIL. plant may take place most rapidly during the period of development of the first and second generations of weevils. Early planted fields, although they may serve to attract, in some small degree, the weevils from surrounding fields, will almost invariably produce larger yields than later planted fields in the same locality. The reason for this is, primarily, the longer period which intervenes between the beginning of setting fruit with its coincident reproduction of weevils and the time when maximum infestation of the field occurs. Comparatively few weevils appear to move from one field of cotton to another until after maximum infestation takes place. Repeated experiments in deferring the planting time of cotton have invariably resulted in small and comparatively unprofitable crops. Extended observations made during the spring of 1906 showed that volunteer? cotton occurred very commonly in fields and yards, along roadsides, and around ginneries and seed houses in every one of the seventeen localities examined about the middle of May, representing territory then infested by the weevil and also extending outside the in- fested territory into Mississippi, Arkansas, and Tennessee. This makes it practically certain that volunteer® cotton occurs everywhere throughout the cotton-growing area, and it may therefore have con- siderable significance in supplying emerged weevils with their first food in spring. Extensive examinations have also shown that sprout% cotton com- monly occurs throughout the southern half of the weevil-infested area in Texas during the average season. As a rule the development of this takes place several weeks in advance of the average planted cot- ton, and it becomes therefore a very important factor in maintaining hibernated weevils and in the development of their first progeny. Although attention has repeatedly been called to this fact, large quan- tities of sprout cotton are still allowed to grow unchecked. It is doubtful whether it is advisable to cultivate this even where it amounts to half a stand. Wherever scattering plants occur in a field of planted cotton they should certainly be chopped out as quickly as they occur. The profit to be derived from them is nothing when com- pared with the great damage which their presence may inflict upon the remainder of the crop through providing the earliest opportunities for the reproduction and multiplication of the weevils. a The term ‘‘volunteer” is restricted to that class of cotton coming from the acci- dentally scattered seed of a preceding crop. Sprout cotton, also called stubble or seppa cotton, is a sprout growth from old cotton roots occurring during the winter or subsequent spring. EE ee ee) ’ «ff + % 4 SUMMARY AND CONCLUSIONS, Q5 SUMMARY AND CONCLUSIONS. Hibernation is the term used to designate those phases in the life and seasonal history of the boll weevil (or of any other animal or plant) which are concerned with its existence through the winter and the manner in which the species is protected or maintained in passing from one season to the next. Food, climatic, and shelter conditions are the principal factors concerned in hibernation. Food conditions in the fall govern largely the abundance of indi- viduals which may enter hibernation and therefore affect the abun- dance of the species in the following spring, since climatic and shelter conditions govern largely the proportion of the hibernating individ- uals which may survive. A large majority of the weevils developed in a field during the season are produced from squares. Weevils becoming adult comparatively late in the season are more likely to survive hibernation than are those which have been active for a number of weeks before the time arrived for them to hibernate successfully. It is possible that offspring of each of the four or five generations which are produced on the average may survive to enter hibernation. No ‘‘top crop” can reasonably be expected within the weevil- infested area. All stages of the weevil may enter hibernation and under excep- tionally favorable climatic conditions larvz which are more than half grown may complete their development if in bolls and become mature during the hibernation period. Immature stages in squares rarely survive. Nearly all of the weevils surviving were adult before the beginning of the hibernation period. The destruction of stalks in the fall, as long as possible before the normal hibernation time, is the most economical and effective method known for reducing the number of weevils entering hibernation. ‘Entrance into hibernation’’ denotes the beginning of the generally inactive period, but it does not necessarily imply a change of position for the individuals involved. For the species and often also for the individual it is a gradual process depending primarily upon tempera- ture conditions. The duration of the entrance period for the species depends upon the severity of the drop in temperature below about 43 degrees of mean average temperature. This period usually occurs coincidently with the first killing frosts and extends through a period of about twenty-five days. From close examination of 1,750 weevils it seems that about 60 per cent of those entering hibernation are males. The number of weevils per acre or.per plant which may enter hiber- nation depends especially upon preceding climatic and food conditions a i ee 96 HIBERNATION OF THE COTTON BOLL WEEVIL. and has been found to vary in different seasons and localities, occa- sionally being as high as 50,000 weevils per acre, or an average of from 7 to 10 weevils per plant. An average of the results in 17 of the most carefully studied fields shows 8,552 weevils per acre, or slightly more than 1 weevil per plant. The proportion between the numbers of weevils hibernating on the stalks and among rubbish scattered on the surface of the ground changes as the season advances, the number on the stalks decreasing. Great mortality occurs soon after the weevils enter hibernation, especially among those upon the surface of the ground. Hibernation usually takes place as the mean average temperature falls below 55 degrees and may remain complete until the mean temperature rises above 60 degrees. Weevils may avail themselves of almost any kind of shelter, and the favorable character of the shelter in relation to prevailing cli- matic conditions will influence the percentage of survival. Many pass the winter sheltered by the old bolls that remain hanging upon the stalks. The percentage of survival in bolls decreases generally from southern to northern Texas. Bolls are frequently so important a factor in shielding weevils from one season to another that it is advisable to destroy them as a regular practice even in northern Texas. Exceptionally cold and wet winter weather is most unfavorable for weevil survival. The destruction of possible shelter through clean culture in the fall is an effective way of reducing weevil injury to the following crop. The shelter to be found in timber fringes around cotton fields is much more difficult to remove or control than is that within the fields. The importance of such unavoidable conditions may be minimized by judicious cleaning up and by rotation of crops. Occasionally weevils may survive in stored cotton seed and be dis- tributed along with it at planting time. This fact justifies the main- tenance of quarantine regulations against the free movement from infested to uninfested territory of cotton seed and closely related cotton products which are apt to shelter weevils. Most of the information obtained in regard to the hibernation of the weevil has resulted from cage experiments in which the influential conditions could be separated and to some degree brought under control. During the winter of 1902-3, at Victoria, Tex., in the small-cage experiments with 356 weevils, an average of about 11 per cent sur- vived. During the following season, also at Victoria, among 400 weevils but one-fourth of 1 per cent survived. During the winter of | 1904—5 larger numbers of weevils were under observation at each of six localities ranging from the southern to the northern portions of SUMMARY AND CONCLUSIONS. Q7 the infested area. This was the season of most exceptional rainfall and cold, and it was not surprising that no weevils survived in the cage tests except at Victoria, which was the southernmost point of experiment. An average for the six localities shows a survival of less than two-thirds of 1 per cent. In the small-cage work of 1905-6 there was an average survival of 1.3 per cent, and practically all of this occurred in the outdoor cages. The most important work done in 1905-6 was in a large cage at Keatchie, La., where 25,800 weevils were placed in 18 compartments. The survival in this cage was 2.82 per cent, and the emergence oc- curred between March 22 and June 28, 1906. The cages having nearest to the ordinary field conditions with poor cultivation gave the largest percentage of successful hibernation. A study of the emergence and temperature records for similar experiments at Dallas, Tex., and Keatchie, La., shows that at the former place approximately 50 per cent of the emergence occurred while the temperature ranged between 58 and 68 degrees, while at the latter place one-half of the total emergence took place while the temperature ranged between about 65 and 75 degrees. Very few weevils emerged while the tem- ® perature was below 57 degrees. There is an optimum period for entrance into hibernation, and weevils entering during this period have a considerably better chance i . of surviving than do those which enter either earlier or later. If } | hibernation is begun earlier than this optimum period, it is likely that ! i$ emergence will be completed earlier during the following season, and 1] also if entrance occurs later than this period it is likely that emer- | gence will begin unusually early in the following spring. | Variation in the period of entrance into hibernation and the dif- ) ference in the nature of the shelter secured by the weevils may rea- | sonably account for the variations found in the amount of accumu- lated effective temperature required to produce complete emergence in the spring. Weevil emerging earlier in the season survived for a longer period than did those which emerged after the middle of the emergence period. It isa common occurrence for weevils to leave their winter quarters upon warm days in spring, returning again to a condition of inactivity for a period of several days or even weeks. Disappear- ance and reappearance in the case of plainly marked individuals has been observed to occur as many as eight times, and a maximum period of forty-three days between appearances has been recorded. These facts argue very strongly indeed against the proposition which is sometimes made by those who are not thoroughly familiar with the habits of the weevil, to starve the emerged weevils by deferring the planting of cotton in the spring. Two lots of 20 and 8 weevils sur- 90317—Bull. 77—09——7 ee etn ee a ee ae es 7 “2 ae LLL EL ee a ee 98 HIBERNATION OF THE COTTON BOLL WEEVIL. vived for an average of thirty and sixty days, respectively, after emer- gence without a particle of green food from the time of their entrance into hibernation to the time of their death. Other tests show simila results. ans The hibernation experiments of 1906-7 consisted of large-cage work in three localities representing the northern, central, and southern portions of the infested area. Each cage inclosed 10 sepa- rate experiments and the comparisons made possible by the three locations, the different-shelter conditions, and the different dates of instituting the experiments furnish the basis for the most complete and significant work which has been done with the hibernation of the weevil. Owing to the exceptional mildness of this season, complete hiber- nation did not occur at any time during the winter in any part of Texas. Emergence began during the last week or ten days of Feb- ruary, 1907.- At Dallas 7.8, at Calvert 10.5, and at Victoria 27.7 per cent of the total numbers of weevils placed in the cages were counted as being active at some time during the winter season when they should normally have all been in complete hibernation. About 13 per cent of the adult weevils buried with a lot of bolls under 2 inches of heavy, black soil escaped and were found upon the cage screen dur- ing the next few days. Weevils were active in the field as well as in the cages during this winter. The period of greatest emergence oc- curred during the latter part of March, which was undoubtedly from four to six weeks earlier than is usual. Succeeding low temperatures served to prolong the period of emergence until the 1st of July. In the three localities under observation an average of 11.5 per cent of the 75,000 weevils placed in the experiments survived and emerged in the spring of 1907. irouping the experiments in the three localities according to the dates of installation of the weevils and averaging the percentages of survival in each group, it appears that there was a steady increase in this percentage upon succeeding dates after the middle of October, when the experiments were started, to the end of November, when the last weevils were placed in the cages. This increase is so nearly regular as to prove conclusively that the date at which weevils are deprived of food in the fall, in its relation to the most favorable period for entrance into hibernation, has a most vital influence upon the prospect for survival. Among the weevils started October 14 but 3.14 per cent survived, while among those started just one month later an average of 19.67 per cent survived. These results prove absolutely the advisability of destroying the food supply of the weevils at least three weeks before the usual time for the first frosts to occur, and they show very plainly just why such a practice is the eel | | | SUMMARY AND CONCLUSIONS. 99 most effective method yet found for reducing the number of weevils that may survive the winter to attack the crop of the following sea- | son. This portion of the bulletin, especially, should be carefully studied in detail. The survival in the various sections of the cages in the three locali- ties ranged from 1.89 to 31.34 per cent. The average survival in each of the localities was as follows: Calvert, 9.49 per cent; Dallas, 11.22 per cent; Victoria, 13.47 per cent. At Dallas the largest percentage of survival occurred in a section of the cage having an abundance of fallen leaves, in which the weevils were placed on November 15 and with the cotton stalks left standing. The smallest survival occurred in a section having fully as favorable shelter conditions but in which the weevils were placed on October 13 and left without any food from October 15. At Victoria the largest survival occurred among weevils started on November 6 without food in the section provided with Spanish moss and_ bark. The winter was too mild to furnish any comparative test of the favorableness of various shelter conditions, but in general it appears that fallen leaves, Spanish moss, and a heavy growth of grass are most favorable to the weevils wherever they may occur. Temperature conditions were practically normal during November, 1906, and the most favorable time for entrance into hibernation was between November 12 and 15 at Dallas and slightly later at the more southern points. In each locality the maximum longevity was shown by males, and the average duration of life of that sex was also slightly in excess of that of females. The average survival of all weevils kept without food was about ten days, and a considerable number lived to between six and twelve weeks after emergence. The maximum survival for any unfed weevil was ninety days. Obviously there is no chance to starve out all weevils by any possible delay in planting. Among the fed weevils the longest-lived was also a male which was active for one hundred and thirty days after its emergence. The longest-lived female was active for one hundred and eighteen days. ‘The average active life for all fed weevils was 25.5 days after emergence. Practically one-half of all fed weevils lived for more than six weeks in the spring. The sex was determined for more than 8,500 weevils which had survived the winter, and it was found that 56.7 per cent of these were males. There is an invariable preponderance of males both in the fall upon entering hibernation and in the spring upon emergence therefrom. Reproduction can not begin until the first squares become at least half grown. At whatever date cotton may be planted in a locality, ) ae wipes le. 7: tule e¢ ly-p an od fie d n do those “ital Tater, but with similar nditions sed, soil, a d cultivation. All volunteer and sprout cotton dovalopeeeenn we a dvance of the main crop should be destroyed before it forms squares, — since otherwise it may furnish the weevils with opportunities for a reproduction for some time before squares become common and _ thereby unnecessarily, early in the season, increase their numbers and the resultant injury to the main crop. O f va -_ =