Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. bors © ' ‘MESSAGE FROM THE oe sige ; ys . z: : , TRANSMITTING A COMMUNICATION FROM THE Sy a . ee “OF AGRICULTURE > SUBMITTING A REPORT ON THE MEXICAN COTTON-BOLL WEEVIL meee WASHINGTON 1912 IWAN. COTTON: BOLL WEEVIL bulletin - “Ho: | ae ee PRESIDENT OF THE UNITED STATES x SF ba Bul. 114, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE I. : Hl | VAY / Wij AANA COTTON PLANT ATTACKED BY BOLL WEEVIL. a, Hanging dry square infested by weevil larva; b, flared square, with weevil punctures; c, cotton boll, sectioned, showing attacking weevil and weevil larva In its cell. (Original.) : ‘ DocuMENT SENATE alae ra MEXICAN COTTON-BOLL WEEVIL MESSAGE FROM THE PRESIDENT OF THE UNITED STATES TRANSMITTING A COMMUNICATION FROM THE SECRETARY OF AGRICULTURE SUBMITTING A REPORT ON THE MEXICAN COTTON-BOLL WEEVIL WASHINGTON 1912 LEITER OF TRANSMITTAL. To the Senate and House of Representatives: I transmit herewith for the information of the Congress a commu- ‘nication from the Secretary of Agriculture, accompanying the manu- -seript of a report on the Mexican Cotton-boll Weevil: A Summary of the Results of the Investigation of this Insect up to December 31, 1911. (Bulletin No. 114, Bureau of Entomology.) The report contains valuable information of great public interest to cotton planters of this country and those depending upon the —cotton-plant industry, and I cordially indorse the recommendation of the Secretary that the report be printed for distribution by Congress _as well as by the department. Wt, Es carr, Tue Wuite Howse, February 12, 1912. 3 * Oe tPA It BY V1 oO Peete hs! Wnt sone ola Me 2tit) J art 1 D ao nario rt! 7 7 fit vik taco Yr aera 10 Cle yt, ol} ee ade | a Hi WwUVABOUIO eM) , Ot { \ yy a istic x * or &p') i7 He reat hl oo } iia tog: 518) ay eixs biti ko 4 4 Lh cypcl Tinney: Gl (Us Tapenth 4 ay a0 AGE mivfea val “tha Fa ajiueoko (0 omit we fegtte au tl Mt. .07 oll ee vio; Shi ler ent ln’ poksHerereie: Atel wi ine aitedaegs ‘OQ G£ ee aan Ly) rier ene |e 4 > eine a ilies Peat te old 1a ero bituiaas nowenel iz | Sh) sarolietim ieee Burs velalieae ita be bie Wes: bvd- a0 rtted| Sethe, ca oT Joel eth ge rrraiTys 4 hy ad’ 7d @dt [fever 4 af. % . s@ )- i ae : } . . | } = 1 LETTERS OF SUBMITTAL. DEPARTMENT OF AGRICULTURE, OFFICE OF THE SECRETARY, Washington, February 8, 1912. To the PRESIDENT OF THE UNITED STATES. Mr. Presiprent: I have the honor te submit herewith, for your information and that of the Congress of the United States, a bulletin entitled ‘‘The Mexican Cotton-boll Weevil: A Summary of the - Results of the Investigation of this Insect up to December 31, 1911,” eee W. D. Hunter and W. D. Pierce of this department. s is an elaboration of a bulletin published in 1905 and of which a special edition was ordered by Congress. Since that date the weevil has spread throughout the State of Louisiana and has entered the States of Arkansas, Mississippi, and Alabama, and threatens to spread throughout the entire cotton-growing area east of the arid regions. In the course of this eastward and northward spread, new conditions have been encountered; the habits and life history of the weevil have undergone some change, and it has met with new parasites and natural enemies. There is a great demand among the cotton planters of this poautty and among those dependent upon the cotton-planting industry for the information contained in this bulletin, and, in view of this fact, I respectfully recommend that this report be transmitted to Congress, together with the maps, illustrations and diagrams accompanying it, to be printed by order of Congress; and I further recommend that not less than 10,000 copies be printed for the use of this department, in addition to such number as Congress may order for the use of its Members. I have the honor to remain, Mr. President, Very respectfully, JAMES WILson, Secretary. DEPARTMENT OF AGRICULTURE. BurEAU OF ENTOMOLOGY, Washington, D. C., January, 1912. Sm: I have the honor to transmit herewith and to recommend for publication a manuscript entitled ‘“‘The Mexican Cotton-boll Weevil: A Summary of the Results of the Investigation of this Insect up to December 31, 1911,” prepared by Messrs. W. D. Hun- ter and W. D. Pierce, of this bureau. This manuscript contains in the briefest possible space an account of the exhaustive investigations of the Mexican cotton-boll weevil which have been conducted by this bureau for some years past. The last comprehensive bulletin on this subject was issued in 1905 and is now far out of date. There is urgent demand for information on this important pest, and this demand will undoubtedly continue as the insect invades new regions. Respectfully, L. O. Howarp, Entomologist and Chief of Bureau. Hon. JAMEs WILSON, Secretary of Agriculture. wos te aon wil Aiiwernt i" ; shah baat di iit ee Hedin’ aah f Dd OD ag SilinG ot, Cay ronal ad? to 100 mb 0 Vina: Da trne W Le eH ShieT LAL aIY (Fi vk ty ele ee 6 ae Ae lane esis jo base COED an bode aa gif tf a hin inka cin : , a) Pits thes ay ctte4 hat etd +e fixiotits Puy? wi): Blow oe ead Dot sv Etg rade rept 2) onii.tey ust 5 fuodyporah & | eric’ bre teeny bina een ete ibe Ae i (uw? To teas yon matters Os ake ne 3 ‘ slat Ga biew deat bok Daveeeieke Ble paeeey hs OPE AL Lae Ttrlyest abt’ : bi sa Aang OP i 1 Woel fy Pal St. wi. Fe tea opcduttteh MMe mie ny it Seti en Taek 1OrrT-a al view! AAT, + tu yip es ly -inrt at) Geek? iwrare see cane Week sft: rh svets (aed ae ayaa 4 tot oe oa sae PhP Toilet) 234 a TORT? ry git DOSE OSE "PLiLGS soghen Dy ali fc oo 7 , a Wee SUS gta Am holy, Pipes ene + | , mapa rt) Vy t3alHa VG re os Cy - (hy ‘oe 2 a "AAT OT HoH AP wr) Eoicro DUE seel?. aes host? rl | JajegE ae ¥ isa; f Panye eR. wala mabe of. neomiba . rece tytal ey ~wviotath- ohh 7 Seu art 20% ae Ss ¥ iBOLT) od nous ah) wre iniisaqy eat eae TOs). he aaa) l oe Ole A oe : | FF wu um AC ieee t ti sadmmanatl. of fname L i Ue Ph - : teeth r «a + ~ ¥ i} sree js #44 | sre , tar! Er rape ae 1 Tu) “a1 Ae ~~ Tie wn ee vid Ww ti | GP ogetay ait aEahe sn 7) isi [Po woe canal. otk 4 tas i . 7 is . a Oa ra , PREPAC BE. Early in 1905 the Bureau of Entomology published as Bulletin 51 an account of the information concerning the Mexican cotton-boll weevil which was available at that time. Since 1905 the work on the investigation of this important insect has been continued by the Bureau of Entomology and by various other agencies. As the result of this recent work certain features of the life history of the pest have received full treatment in publications of the bureau. This is the case with hibernation,' natural control,’ arch proliferation,* and repression.° Important contributions have been made by State agencies. The result has been that the original bulletin has been out of date for some time. On many topics the amount of informa- tion now avaiable is more than double that at hand at the time the previous publication was issued. Moreover, it seems advisable that the history of the pest in the United States and an account of the losses occasioned by it should be brought up to date. For these reasons the present publication has been prepared to include all of the more important available information concerning the boll weevil. It is based upon Bulletin 51, from which many extracts have been used, and will supersede that publication. In the nature of the case it is impossible to include all of the data which have been published with reference to certain phases of the life history of the Moll weevil, such as hibernation and parasite con- trol. In all such cases, however, the main essentials regarding these special topics have been incorporated. Persons who desire more etailed information may consult the various special publications, which are still available. As might be supposed the accumulation of many additional data has necessarily changed some of the conclusions drawn in the earlier publication. It is to be noted, however, that these changes are generally of little consequence. The investigation of the boll weevil was begun by the then Division of Entomology in 1895 and has been continued, more or less con- stantly, to the present date. The vast amount of information which has thus been accumulated is to be credited to a large number of entomologists, many of whom are now doing work in other fields, The earlier investigations of the weevil were conducted by Dr. L. O. Howard and Messrs. C. L. Marlatt, C. H. T. Townsend, E. A. Schwarz. and Frederick Mally. The State officers who have assisted mate- rially in this work have been the entomologists of Texas, Messrs. E. D. Sanderson, A. F. Conradi, C. E. Sanborn, and Wilmon Newell; of Louisiana, Messrs. H. A. Morgan, Wilmon Newell, J. B. Garrett, 1 Bull. 77, Bur. Ent., U. S. Dept. Agr., 1909. 4 Bull. 59, Bur. Ent., U. S. Dept. Agr., 1906. 2 Bull. 74, Bur. Ent., U.S. Dept. Agr., 1907. 5 Farmers’ Bull. 344, U.S. Dept. Agr., 1909. ® Bull. 100, Bur. Ent., U. 8. Dept. Agr., 1912. 7 8 PREFACE. T. C. Barber, H. Dean, M.S. Dougherty, A. H. Rosenfeld, and G. A. Runner; of Oklahoma, Messrs. C. E. Sanborn and A. L. Lovett; of Arkansas, Dr. George F. Adams; of Mississippi, Messrs. Glenn W. | Herrick, R. W. Harned, 8. F. Blumenfeld, aa R N. Lobdell; and of — Alabama, Dr. W. E. Hinds and Messrs. W. F. Turner and I. W. Car- penter. The work has been facilitated by the commissioners of agriculture of the various States, including Col. Charles Shuler, for- mer commissioner of agriculture of Louisiana, Mr. H. E. Blakeslee, commissioner of agriculture of Mississippi, and Mr. F. W. Gist, former commissioner of agriculture of Oklahoma. The agents of the Bureau of Entomology who have contributed to this bulletin are: Messrs. F. C. Bishopp, J. C. Crawford, R. A. Cush- man, F. L. Elliott, A. F. Felt, C. W: Flynn, J. B. Garrett, W. H. Gilson, S. Goes, G. H. Harris, W. E. Hinds, W. H. Hoffman, T. E. Holloway, C. E. Hood, W. A. Hooker, R. C. Howell, C. R. Jones, B. T. Jordan, O. M. Lander, Thomas Lucas, E. A. McGregor, J. D. Mitchell, A. C. Morgan, A. W. Morrill, D. C. Parman, T. C. Paulsen, H. Pinkus, F. C. Pratt, V. I. Safro, E. A. Schwarz, J. S. Slack, G. D. Smith, H.S. Smith, C. S. Spooner, E. 8. Tucker, G. N. Wolcott, and W. W. Yothers. Of these agents Dr. W. E. Hinds, who for several years was the principal assistant in the cotton boll weevil investigations of this bureau, was the most extensive contributor. 'To him we owe a large share of the accurate data on the life history and habits of the boll weevil. He also did a large amount of work in the prepara- tion of Bulletin 51, upon which this publication is based. e have attempted throughout the bulletin to credit the various agents with the work for which they have been directly responsible, but in this lace it must be stated that the results obtained are due to the faithful and efficient service of the whole corps of entomologists who have been associated with the writers. The work has also been oreatly facilitated by the constant interest and encouragement of the chief of the bureau. Special credit is due to Mr. E. S. Tucker for skillful preparation of the plates. THE AUTHORS. CONTE NPS: fr Birect losses caused by the Raliowecuie 6 ee-n+ oe eee eee Tho larva ....--22.-scnacnles ach case ene eee fee See ee eee er Food habits. ...25- 2.2.22 cogs nic ne eee ee Duration of larval stage... .-»-.--Gacuce saa Rats dees cee oe Pupal cells... 0 20. fob 3. do Scesh et Re) eet Dee eee ee ee Pupation 2... danse ste 2 ies ke th te SEE pe ee ee TRE. PUP Ae nia d ance sccninis = ~/n'c 005 ond ain Cis bint eian bcd Ste ee ee oe ACHIVIUY = «2-5 ds Senn Famke ole RE ~ eles ot eee Duration of pupal stave. . <2 oc oe we ee ee ee Percentage of weevils developed from infested squares...........-..----- Rife cycle - <2 25s 22 eo een ee vee ptm ce es We ee Duration. of life.cycle..3-. 23). 2 20 a ae eee ee Sexual variations... sooo eee ee Oe Variations due to location of developing stage......-......-...-- Variations due to time of falling of infested squares..........-..-- Variations: duevto temperature: ..-.>~--2-:5: - <. ce ae see oe Duration of hibermidtion period. oot Ls 2! oS ee eee ee eee Average length: of hibernation period. '.:').) <2. 2. ee ee eee Relation of shelter to duration of hibernation...........-...-.-.-...-.- Emergence from hibernation. 2/3200 Te ee eee Time GP emervencees. ooo es ee ee ee eee Rate of emerrence.:o. 2s ee ee ee ee eee Survival of hibernated weevils: ..< =. 02. 320222 ee eee Relation of fall destruction to survival............. CONTENTS. Tibernation—Continued. Survival of hibernated weevils—Continued. Relation of shelter to survival Bae eA rel nits aOR Cite enth bwich nemo ce « peseeviyy Ce aT Gc ae i cn ee a aximum length of life.............. he, Se Relation of emergence and longevity to time of planting . . EMG A a eee . ales he cera oerse'e via k vars win a Sec ekigete wo 2b vied. fa a ae we Sat Meee chee Sem ans &. Climatic influences on vitality and activities. . ay ie eae Field observations on mortality due to heat and dryness. . 2 General discussion of the relations of temperature to the boll weevil. . Mapervone Of Inia! temperature ..............9--.--. cele. SS AEE 1007 ea ell li eS el ales Re et NE 8 MMOD IDE a ae a auido njele vo oe vis mim ict G Mga bin @ PMP MAO ae onc web icin span amine oo we vie oe ate ke power eonc Or its) temperatures............ 0.02500 00.0..2.20.. PommumeieeiOus Gt temperatire.....--. 2... ee eee Effects of flooding age LAV EO 21 E(t bog sR Ree Se Sat By Lae oe a ERS Mle oi SI ca wis cio: cia w ie wie oe oe Se Se EN So mimne es IMME ERTS eshte ele ee alow ec et eee des between earmee EEMPERU Me LAEL COU ITO! 22.2. ete ve ee eee RT OE nrg A So Me ie a oe oe See eee cle es Darmeiicund Grogatory IISeCt Enemies. -......-.------ 2.2 ieee eee eee A brief summary of the insect species attacking the boll weevil....... EEE a itt SS Saosin cece ee cs thee totes ce Son dee snes CORI GGES Re ee ee eee ee et ea Pec or Nusign OL Kuares and weevils... -...-....--. 2-22-22. et ee ee Pepummepommenis in. burial... 2... oe eee ee alee a Burial of adult weevils at time of hibernation................------- Rance acm Gitial Experimenta. 2.022200 0. 2 betel. ee REI el Pe SKE oe Nie sict oes Aad Sa ceee ese ewe ee PP MInEGInAnC GN Meade oo. eee ot ye PO os Pe EAE NR a ne aa Se Bae Ee cE eis rt 98 il 9 Sa ead ane ge SET DN Se RS a A Futile methods which have been suggested. .........--.---------------- Min et wn COLLONSECM Oll 2 22 eS RE Rea aS sins oh ue pn yer he oe Ed PR I as sso ete, cae Se i IRIE oe i Sa ee ce ane ALE BS Trapping at light-. 22 Other proposed remedies. . perenne Be 2 Requirements of a satisfactory method of boll-weevil control...........-- AE SESS a a a ea ee Summary of means of repression of the boll weevil.....-..--.-.----------- Beovine te Hou weeyil In cotton seed... .. 222.552... 58225--2------ Legal restrictions regarding the boll weevil ...................---------- SeReEee ERP try eres tee Pt ete TS ie alia yee imaniuer ortie severd! states. .2.i 0505.00 OP Po eck eee IE eeee eee ere es 8g a Ori ee eee Ere eae a re SE Me Pa ee bk Nature of weevil activity following emergence from hibernation..........-. PrateE I. re ITT. IV. VI. VII. VIII. ILLUSTRATIONS. PLATES. P Cotton plant attacked by boll weevil. a, Hanging dry square infested by weevil larva; 6, flared square with weevil punctures; c, cotton boll, sectioned, showing attacking weevil and weeyil lary. In tts Cell. 8 eas ane eos eee a eee Frontispiece. The boll weevil and insects often mistaken for it. a, The cotton boll weevil, Anthonomus grandis; 6, the mallow weevil, Anthono- mus fulvus; c, the southern pine weevil, Pissodes nemorensis; d, the cottonwood flower weevil, Dorytomus mucidus; e, Conotrachelus erinaceus; f, the pecan gall weevil, Conotrachelus elegans.......- Anatomical structure of the boll weevil. a, Dorsal view of anal segments of larva; b, front view of head and anterior segments of larva; c, ventral view of anal segments of larva; d, lateral view of adult; e, lateral view of larva; f, ventral view of adult; g, dorsal view of adult with wings spread; h, ventral view of pupa; 7, ventral view of anal segments of pupa; j, ventral view of anterior portion OLPUAs « 2 shee bot sees ros See nen ee eee eee The atin boll weevil and emergence holes. a, Squares of Peruvian cotton showing emergence holes of the Peruvian cotton square weevil; b, square of upland cotton showing emergence hole of the cotton boll weevil; c, adult boll weevil on cotton square; d, adult boll weevil puncturing cotton square; e, adult boll weevil emerg- ing from cotton boll; /, small dry bolls showing emergence holes; g, hull of boll.with weevils found hibernatine..:~--<--- eee . Effects of boll weevil attack on leafand squares. a, Cotton leaf much fed upon by adults; 6, square with two egg punctures; c, flared square with many feeding punctures; d, square prevented from blooming by puncture; e, bloom injured by feeding punctures; f, poor blooms caused by feeding punctures. .......-.....-.--.---- Injury by boll weevil to squares. a, Bloom checked by attacks of larva; 6, square opened, showing grown larva; c, square opened, showing pupa; d, dwarfed boll opened, showing one larva and two pup; e, weevil escaping from square; f, emergence hole of adult THISQUANCs 2-5 ee ne fle 2a an ae ee oe eee Injury by boll weevil to bolls. a, Three larve in boll; 6, emergence hole in dry, unopened boll; c, two larve in boll; d, weevils punctur- ing boll; e, opened boll with two locks injured by weevil; f, large bolls.severely punctured :.~-. <2 32/..4-02< Soci ene ae ee eee Field conditions in territory occupied by the boll weevil. Fig. a.— Newly planted’cotton field, with sprouts from overwintered cotton roots. J%g. b.—Fallen infested.squares ......-.----------------- . Relation of boll weevil cells to seed. a, Boll weevil pupa found in cotton seed; 6, boll weevil pupa in cell of lint from boll; c, weevil cell in dwarfed cotton boll containing live pupa taken among seed; a; weevil cells in ‘bolis;ie, cotton seeds: =) 2-2- = 25--se ase eee . Fig. a—Boll weevil remains after passing through fan from gin. Fig. b.—Ten-sectioned hibernation cage...........-.------------ . Hibernation conditions for the boll weevil. Fig. a.—Cotton field adjacent to timber covered with Spanish moss. Fig. b.—Proxim- ity of moss-laden trees, conducing to high infestation by weevil. - . Hibernation conditions for the boll weevil. Fig. a.—Standing dead timber and forest environment favorable for hibernation of weevils. 28 32 36 40 100 100 me ve} oo ~I o> or me CO Ne a eS © ILLUSTRATIONS, . Natural control of the boll weevil. _a, Pilose and nonpilose stems of cotton; 6, larva of boll weevil crushed by proliferation; c, pupaof Catolaccus incertus on upa of cotton-boll weevil; d, larva of Microbracon mellitor attacking boll weevil larva; e, a3 holes Eseved by Solenopsis geminata in effecting entrance into in- PRION ACS he re ASE dp a ciciuls ai dinaiy amin ws Bea sted oho Bei . The difference between hanging and fallen squares. Fig. a.— Cotton squares with short absciss layer, permitting infested squares to fall. ig. b.—Cotton squares with long absciss layer, retaining infested forms to hang and dry................----- . Boll weevil ants. a, Eciton commutatus; b, Cremastogaster lineo- lata; ¢, Dorymyrmex pyramicus; d, Monomorium pharaonis; e, Solenopsis molesta; /, ridomyrmex ON GUTS Aire esr tat ee AS errs . Boll weevil parasites. a, Eurytoma tylodermatis, male; 6, Lury- toma tylodermatis, female; c, M icrodontomerus anthonomi, female: “, antenna of same; d, Habrocytus piercet, female; d’, antenna of same; é, Catolaccus hunteri, female; e’, antenna of same: rales antenna of Catolaccus incertus.....---2+.e+++e+eeeeeeeeeeccee XVIII. Boll weevil parasites. a, Lariophagus texanus, female; b, emer- gence hole of Tetrastichus. hunteri trom weevil larva; c, Tetra- stichus hunteri, female; c’, antenna of same; d, puparium of Ennyomma ¢ globosa. in weevil larvasce, Ennyomma globosa; f, Cerambycobius cyaniceps, female; /’, natural position of same. XIX. Effect of Paris green on cotton. Fig. a.—Cotton before treat- ment with Paris green. Fig. b.—Cotton one week after treat- ESS ETERS 22) 0 ae See a XX. Cultural control of the boll weevil. Fig. a.—EKarly fal] destruc- tion of stalks, the fundamental method for controlling the boll weevil. Windrowing stalks for burning. Fig. b.—Chain cul- iieleL passine throwrh) cotton TOWS) \. 42/<)-)2. ---22)o.0p ee . Map showing minimum temperatures in the winter of 1910-11 in Louisiana. _ Evarthrus sodalis an enemy’of the bolfweewils” > 732227) sare eee 2. Chauliognathus marginatus an enemy of the boll weevil........----.--..-- 3. Hydnocera pubescens an enemy of the boll weevil....................---. . Apparatus for fumigating cotton seed in the sack. ee ee acta ene a oiled THE MEXICAN COTTON-BOLL WEEVIL: A SUM- ~ MARY OF THE INVESTIGATION OF THIS INSECT UP TO DECEMBER 31, 1911. ORIGIN AND HISTORY. There is very little certainty regarding the history of the Mexican cotton-boll weevil before its presence in Texas came to the attention of the Division of Entomology in 1894. The species was described by Boheman in 1843 from specimens received from Vera Cruz, and was recorded by Suffrian in 1871 as occurring at Cardenas and San Cristobal, in Cuba. Written documents in the archives at Mon- _cloya, in the State of Coahuila, Mexico, indicate that the cultivation of cotton was practically abandoned in the vicinity of that town about the year 1848, or at least that some insect caused very great fears that 1t would be necessary to abandon the cultivation of cotton. A rather careful investigation of the records makes it by no means clear that the insect was the boll weevil, although there is a rather firmly embedded popular opinion in Mexico, as well as in the southern United States, that the damage must have been perpetrated by that species. So far as the accounts indicate, it might have been the bollworm (/Teliothis obsoleta Fab.) or the cotton caterpillar (Alabama argillacea Hiibn. ). rom the time of the note by Suffrian regarding the occurrence of _the weevil in Cuba in 1871, up to 1885, there has been found no pub- lished record concerning it. In 1885, however, Dr. C. V. Riley, then Entomologist of the Department of Agriculture, published in the report of the Commissioner of Agriculture a very brief note to the effect that Anthonomus grandis had been reared in the department from dwarfed cotton bolls sent by the late Dr. Edward Palmer from northern Mexico.! This is the first account in which the species is associated with damage to cotton. The material referred to was collected in the State of Coahuila, presumably not far from the town of Monclova. 1 The following is a copy of the original letter by Dr. Palmer: EAGLE Pass, TEX., Sept. 28, 1880. The COMMISSIONER OF AGRICULTURE. Sir: Previous to leaving Monclova, Mexico, for this place I visited some fields planted with cotton. Seeing but few bolls of cotton, examination revealed the cause. An insect deposits its egg and the boll ; thus some plants had only two or three, others five or six bolls, while underneath the leaves, in the shade thereof, were many that had fallen there in the moist shade to lay for the larva to hatch. Please ee roclosed insects and many of the injured bolls, some newly punctured, others taken from under the t. Monclova, Mexico, and the surrounding country a few years ago was famous fcr its large supply of cotton; at this time none can be grown, owing to the destructive insect, samples of which aresent. The inhabit- ants would be glad to hear of a remedy, upon which matter in the future I will communicate with your department. Your obedient servant, EDWARD PALMER. The specimens were sent by Dr. L. O. Howard to Mr. Henry Ulke, who transmitted them to Dr. George Horn, of Philadelphia. In turn Dr. Horn forwarded the material to Dr. Sallé, in Paris, who made the determination, 15 16 THE MEXICAN COTTON-BOLL WEEVIL. After the American occupation of Cuba the boll weevil began to} attract considerable attention in that island. In 1902 it was ob-§ served that the weevil was ane injurious to cotton at Cayamas, Cuba. This place was visited by Mr. E. A. Schwarz, of the Bureau of Entomology, in the spring of 1903. He found that the native food plants of the weevil in Cuba were the “wild” or “loose” cottor (Gossypium brasiliense) and the native ‘‘kidney’’ cotton—both tree cottons. The spread of the boll weevil in Mexico appears to have begun prior to 1892. In that year it appeared at Sabinas, State of Coahuila, and about this time or earlier it appeared at San Juan Allende, Morelos, Zaragoza, and Matamoras, Mexico. It crossed the Rio Grande at Brownsville probably before 1892. At any rate, duri that year it caused considerable loss at Brownsville. In 1894 it ha spread to half a dozen counties in the Brownsville region, and during the last months of the year was brought to the attention of the Division of Entomology as an important enemy of cotton. Mr, C. H. T. Townsend was immediately sent to the territory affected, His report, published in March, 1895, dealt with the life history and habits of the insect, which were previously entirely unknown, the probable method of its importation, and the damage that might result from its work, and closed with recommendations for fighting it and preventing its further advance in the cotton-producing regions of Texas. It is much to be regretted that at that time the State of Texas did not adopt the suggestion made by the Bureau of Ento- mology that a belt be established along the Rio Grande in which the cultivation of cotton should be prohibited, and thus the advance of the insect be cut off.! The events of the last few years have verified the predictions of the Division of Entomology in view of the advance made and the damage caused by the insect. In 1895 the insect was found by the entomologists of the Division of Entomology, who continued the investigation started the year before, as far north as San Antonio and as far east as Wharton. Such a serious advance toward the cotton-producing region of the State caused the Bureau of Entomology to continue its investiga- tions during practically the whole season. The results of this work | were incorporated in a circular by Dr. L. O. Howard, published early in 1896, in both Spanish and English editions. An unusual drought in the summer of 1896 prevented the maturity of the fall broods of the weevil, and consequently there was no | extension of the territory affected. During 1896 the investigations were continued, and the results published in another circular issued in February, 1897. This cneae was published in Spanish and German as well as English editions, for the benefit of the very large foreign population in southern Texas. The season of 1897 was in many respects almost as unfavorable as that of 1896, but the pest increased its range to the region about Yoakum and Gonzales. Although this extension was small, it was exceedingly important, because the richest cotton lands in the United States were beginning to be invaded. The problem had thus become so important that Mr. C. H. T. Townsend was stationed ; 1 This suggestion was brought to the attention of the General Assembly of Texas by the then Assistant Secretary of Agriculture, Dr. C. W. Dabney, who went to Austin for that purpose, ORIGIN AND HISTORY. 14 in Mexico, in a region supposed to be the original home of the insect, for several months to discover, if possible, any parasites or diseases that might be affecting it, with the object of introducing them to prey | upon the pestin Texas. Unfortunately, nothing was found that gave an hope of material assistance in the warfare against the weevil. it The season of 1898 was very favorable for the insect. Investiga- tions by the Bureau of Entomology were continued, and a summary of the work, dealing especially with experiments conducted by Mr. C. L. Marlatt in the spring of 1896, was published in still another circular. During this year the first of a long series of conventions to discuss the boll weevil was held. This meeting took place at - Victoria, Tex., on October 12, and was attended by many planters, bankers, and merchants. At this time the Legislature of the State of Texas made provision for the appointment of a State entomologist and provided a limited appropriation for an investigation of means of combating the boll weevil. In view of this fact the Bureau of Entomology discontinued temporarily the work that had been carried on through agents kept in the field almost constantly for four years, and all correspondence was referred to the State entomologist of Texas. Unfortunately, however, the insect continued to spread, and it soon became apparent that other States were threatened. This caused the work to be taken up anew by the Bureau of Entomology in 1901, in accord- ance with a special appropriation by Congress for an investigation independent of that ate was being carried on by the State of Texas, and with special reference to the discovery, if possible, of means of preventing the insect from spreading into adjoining States. In accordance with the provision mentioned the senior writer was sent to Texas in March, 1901, and remained in that State until December. He carried on cooperative work upon eight large plan- tations in the region infested by the weevil. The result of his obser- vations was to suggest the advisability of a considerable enlargement of the scope of the work. It had been found that simple cooperative work with the planters was exceedingly unsatisfactory. The need of a means of testing the recommendations of the Bureau of Ento- mology upon a large scale, and thereby furnishing actual demonstra- tions to the planters, became apparent. Consequently, in 1902, at the suggestion of the Department of Agriculture, provision for the enlargement of the work was made by Congress. Agreements were ‘made with two large planters in typical situations for testing the principal features of the cultural system of controlling the pest upon a large scale. At the same time the headquarters and labora- tory of the special investigation were established at Victoria. The results of the field work for this year were published in the form of a Farmers’ Bulletin. During this season cooperation was carried on with the Mexican commission charged with the investigation of the boll weevil in that country, which was arranged on the occasion of a personal visit of Dr. L. O. Howard to the City of Mexico in the fall of the preceding year. In November an enthusiastic convention of planters and merchants to discuss the problems was held at Dallas, Tex. The favorable reception by the planters of Texas of the experi- mental field work conducted during 1902 and the increase in the 28873°—S. Doc. 305, 62-2——2 18 THE MEXICAN COTTON-BOLL WEEVIL. — territory occupied by the pest brought about an enlarged appropria-~ @ tion for the work of 1903. It thus became possible to increase the @ number and size of the experimental fields as well as to devote more attention to the investigation of matters suggested by previous work in the laboratory. Seven experimental and demonstrational farms, aggregating 558 acres, were accordingly established in as many distinct cotton districts in Texas. . During 1903 the weevil was recorded from San Juan, Guatemala, - by G. C. Champion. In this same year it was discovered that the weevils were being introduced in cottonseed into the ‘“ Laguna” district in the State of Coahuila, Mexico, but effective measures were taken by the Mexican authorities, and the infestation was suppressed. Since that time the weevil has never been recorded from this impor-_ tant cotton region. The year 1903 is also important as being that in which the weevil first crossed the Sabine River into Sabine and Calcasieu Parishes in Louisiana. Another feature of the year was a large boll-weevil convention held at Dallas, Tex., which estab- lished a permanent organization and issued a number of valuable circulars relating to the problem. A similar meeting was held in § New Orleans on November 30, at which the governor of the State 9 presided. In 1904 a general realization of the great damage done by the § boll weevil led to the appropriation by Congress of $250,000 for use @ in enabling the Secretary of Agriculture to meet the emergency caused by the ravages of the insect. It thus became possible again to increase the number of experimental farms and to pay especial attention to a number of important matters that could not be investi- gated previously. The large appropriation was used in part to estab- lish the demonstration work of the department. The object of this 9 work was to demonstrate the methods of control perfected and — demonstrated previously by the Bureau of Entomology. It has gradually developed into the well-known Farmers’ Cooperdti Demonstration Work of the Bureau of Plant Industry. With the advent of the weevil into Louisiana that State began energetic work against the pest. Largely through the efforts of Prof. W. C. Stubbs an extraordinary session of the legislature was convened early in 1904. The action decided upon was the estab- lishment of the Crop Pest Commission of Louisiana, with full authority to take such a course as might be found advisable. - Prof. H. A. Mor- gan became secretary and entomologist of the commission. In 1905 Prof. Morgan was succeeded by Mr. Wilmon Newell, who continued the cooperative investigations with the Bureau of Entomology throughout the period of his services in Louisiana, which extended to January 31, 1910. During 1904 two conventions were held at Shreveport, La. The first discussed especially the local features of the problem, while the | second, which was held in November, was national in its scope. It | was attended by delegates from most of the Southern States. The year 1904 witnessed an extensive dispersion of the weevil into new regions in Texas and Louisiana. During this year, Dr. O. F. Cook, of the Bureau of Plant Industry, found the weevil thoroughly established in Alta Vera Paz, Guatemala. At the beginning of 1905 the laboratory of the bureau was moved from Victoria to Dallas, Tex., where it has since remained. The ORIGIN AND HISTORY. 19 ybservations on the activities of the boll weevil in this year were nsiderably limited, owing to restrictions on travel imposed by the yellow-fever quarantine. The insect was found, however, at Mazat- , State of Sinaloa, on the Pacific coast of Mexico, on March 20, 1905. In 1906 the weevil spread extensively to the west in Texas, a con- ‘siderable distance northward into Oklahoma, into Arkansas, and almost to the Mississippi River in Louisiana. During this season Mr. M. T. Cook recorded the weevil from Santiago de las Vegas, Cuba, in addition to places previously recorded. The year 1907 marked the crossing of the Mississippi River into the State of Mississippi. There was a corresponding movement to the north, but none to the west. A very severe setback, caused by climatic conditions, occurred in the northern and western parts of the infested territory in November, 1907. In 1908 the most noticeable advances were made into Mississippi and Arkansas. By this time a considerable part of the Mississipp1 Delta region of Louisiana had become Theestedl In the spring of 1909 preparations were made for the establish- ment of a laboratory at Tallulah, La. The main object of this laboratory has been the accumulation of data concerning the local features of the weevil problem in the region where the greatest damage is certain to occur. Cold weather in the winter of 1908-9 again checked the boll weevil so completely that it did no appre- clable damage in Oklahoma and the greater part of Texas during 1909. The checking of the insect was enhanced by the very unusua heat of July and August. However, there were enough weevils in the Red River Valley to give rise to a considerable movement into Arkansas and to a remarkable eastward movement in southern Mississippi which ended with a total advance of 120 miles eastward. This carried the insect to within 6 miles of the-Alabama border. At the same time the decided climatic control of the season held the weevils in check in northern Louisiana so that the total advance in the Delta was little more than 20 miles northeastward. The year 1909 closed with an exceptionally cold December which greatly reduced the numbers of the weevil in extreme northern Louisiana and in Arkansas, Oklahoma, and northern Texas. The winter of 1909-10 was probably more disastrous for the weevil than any it had previously experienced in this country. It was shown by examinations made in June and July, 1910, that the weevil had lost a very wide belt of territory in western Texas and that there was less than 1 per cent infestation in one-third of the infested region of Oklahoma and Texas. The reduction was also very pronounced in northern Louisiana and in the Mississippi Delta. In August it was found that there had been some recovery of lost territory, but there were still several thousand square miles of formerly infested territory in Oklahoma which the weevil had been unable to regain. There were slight gains in western Texas in the vicinity of Abilene late in the season and rather pronounced gains in the Delta region of Ar- kansas and in the hills of northern Mississippi and eastward through southern Mississippi and Alabama to the border of Florida. On account of the general scarcity of weevils the total amount of damage done during 1910 was less than had been experienced for several preceding years. 20 THE MEXICAN COTTON-BOLL WEEVIL. An early frost on October 29, 1910, throughout all but the coa regions of the infested territory, caused the death of all but a ver small fraction of the fall-bred weevils, and consequently the season of 1911 started with a low infestation. The general defoliation by the leaf worm, however, reduced the available food supply and caused a general dispersion, which enabled the weevils to regain considerable lost ground in Texas and Oklahoma, to make remarkable gains in Arkansas, Mississippi, and Alabama, and to invade Florida. DISTRIBUTION. The territory covered by the boll weevil at the end of the year 1911 (see fig. 1) included the southeastern half of the cotton section of Texas, the southeastern corner of Oklahoma, the southern three- y e rc. 1.—Map showing the distribution of the cotton-boll weevil on January 1, 1912. (Original.) fourths of Arkansas, all of Louisiana, the southern three-fourths of | Mississippi, the southwestern corner of Alabama, and the western | portion of Florida. In addition to these States the weevil is found throughout Mexico in the cotten-growing region of both the Atlantic and Pacific coasts with the exception of certain mountain regions. foremost among the excepted regions is that known as the Laguna district in the vicinity of Torreon, Mexico. The weevil has not been | recorded from any part of Yucatan excepting the western coast, although it may occur on tree cottons throughout this region. It has not been recorded from British Honduras, but is known to occur throughout the cotton regions of Guatemala and in Costa Rica. There is little doubt but that it also extends into other Central American Republics, although no definite records have ever been | LOSSES DUE TO THE BOLL WEEVIL. 21 nade. The five western States of Cuba are infested, and possibly the weevil is to be found throughout the entire island. It has not been ound in any of the other West Indian Islands. LOSSES DUE TO THE BOLL WEEVIL." _ Various estimates of the loss occasioned to cotton planters by the boll weevil have been made. In the nature of the case such esti- mates must be made upon data that are difficult to obtain and in the —eollection of which errors must inevitably occur. There is, of course, a general tendency to exaggerate agricultural losses as well as to - attribute to a single factor damage that is the result of a combination of many influences. Before the advent of the boll weevil into Texas unfavorable weather at planting time, summer droughts, and heavy fall rains caused very light crops to be produced. Now, however, the tendency is everywhere to attribute all of the shortage to the weevil. Nevertheless, the pest is undoubtedly the most serious menace that the cotton planters of the South have ever been compelled to face, if not, indeed, the most serious danger that ever threatened any agri- ¢cultural industry. It was generally considered, until the appearance of the pest in Texas, that there were no apparent difficulties to prevent an increase in cotton production that would keep up to the enlarging demand of the world until at least twice the present normal crop of about 12,000,000 bales should be produced. Now, however, in the opinion of most authorities, the weevil has made this possibility somewhat doubtful, although the first fears entertained in many localities that the cultivation of cotton would have to be abandoned have generally been given up. An especially unfavorable feature of the problem is in the fact that the weevil reached Texas at what would have been, from other considerations, the most critical time in the history of the production of the staple in the State. The natural fertility of the cotton lands had been so great that planters had neglected such matters as seed selection, varieties, fertilizers, and rotation, that must eventually receive consideration in any cotton- producing country. In general, the only seed used was from the crop of the preceding year, unselected, and of absolutely unknown variety, and the use of fertilizers had not been practiced at all. Although it is by no means true that the fertility of the soil had been exhausted, nevertheless, on many of the older plantations in Texas the continuous planting of cotton with a run-down condition of the seed combined to make a change necessary in order that the industry ight be continued profitably. n 1905 Prof. E. D. Sanderson ? made a very careful estimate of the damage done by the boll weevil in Texas for the six years ending with 1904. During this period he found that there had been an average annual decrease due to the boll weevil of 43 per cent, amount- ing to 0.182 bale per acre a year in the infected territory. , rof. Sanderson found that in 1899 the 18 counties infested at that time showed a decrease of 0.135 bale per acre, of which it was con- sidered that 150,000 bales were chargeable to the weevil. In 1900 the great storm of September complicated matters so that no reliable estimate of injury could be made. In 1901 the general conditions 1 The following paragraph is modified from Bul. No. 51, Bureau of Entomology, pp. 21-25. 2 The Boll Weevil and Cotton Crop of Texas, published by the Texas Department of Agriculture. 22 THE MEXICAN COTTON-BOLL WEEVIL. throughout the State were unfavorable to the cotton crop, resulting in a reduction of 0.05 bale per acre for the uninfested portion of the State. The weevil loss was estimated at 100,920 bales. In 1903 the 32 counties infested produced 0.28 bale per acre. The loss chargeable to the boll weevil was 200,000 bales. In 1903 the 4¢ counties infested yielded 0.23 bale per acre, as against an average of 0.43 bale during years previous to infestation, which was interpreted to show a loss of 500,000 bales due to the weevil. In 1904, 69 counties were infested. These showed a loss of 0.22 bale per acre. This— meant, after deducting the losses due to the bollworm and other causes, a loss of 559,000 bales due to the boll weevil. In these esti- mates the losses for the period from 1899 to 1904 amounted to_ 1,725,000 bales. ‘ The weevil was in Texas from 1899 to 1904, but had not caused any appreciable damage in Louisiana during that period. The statistics of production and acreage of the two States for these years show clearly the effect of the weevil on the crop. TasBLe I.—Comparison of cotton production and acreage in Texas and Louisiana in equivalents of 500-pound bales. Texas. Louisiana. Year. a ee — Acreage. Crop Acreage. Crop | ae ee eS ee a a eae Acres Bales. Acres Bales NRO Say a Ne ee ere bel ees a Sa 6,642,309 | 2,609,018 | 1,179,156 700, 352 111 UC ik fale eRe t d ms ag i a re IRON A Apt 7,041,000 | 3,438,386 | 1,285,000 705, 767 Ue isi ee Se ee oe ee ee ee OS 7,745,100 | 2,502,166 | 1,400,650 840, 476 1 ee yO, Se Ae So neee See = AIRE beyonce Smear 8,006,546 | 2,498,013 | 1,662, 567 882, 073 PU Ue oles UU Pd Aisi CEP e ee Ge &, 129,300 | 2,471,081 | 1,709, 200 824, 965 TP TIEL EE Say sae Sie REA paren aati oS 8,704,000 | 3,030,433 | 1,940,000 893,193 It will be seen that while the acreage in Texas and Louisiana increased at about the same proportion the crop in Texas decreased annually for the six years ending with 1904 (with two exceptions— 1900 and 1904), while the crop in Louisiana increased annually (with | one inconsiderable exception, in 1903). That the boll weevil pre- vented Texas from keeping pace with Louisiana during this period will be admitted by all. The exceptional years, 1900 and 1904, in which the production in Texas did not decrease, were those in which the conditions for the cotton plant were unusually favorable. More-_ over, it is to be noted that in the first of these two years the pest had not reached far into the most productive counties. Further indications of the amount of weevil damage are available from the statistics of production per acre, as shown by Table II: TABLE II.—-Average yield per acre of cotton by five-year periods in 500-pound bales. Louis- Arkan- Okla- Missis- Years. | Texas. iana. sas. homa. | sippi. | Bale. Bale. | Bale. Bale. Bale. Lt |! Pee ana SE oe ee ee Se URE Og ea ewe 0. 39 0. 58 0. 58 0. 48 0. 45 1. SE Se at Se en ay Se ae ee aren 37 51 . 40 48 - 40 ANOS] B07 om ae 8 ey eee >, ee Fee Se Ae 1.38 2 . 45 2 - 43 US | aE Oe ea Pe NT A Ses 1,39 . 52 .45 .47 . 40 OT Le ee ee ee | 1.34 1.49 1.40 1.47 44 1 1.35 1,40 1908-1910........ ; BN ap Dg ee Py ar ah y- 1.29 1.37 1 During these periods the weevil has caused more or less damage to the crop. LOSSES DUE TO THE BOLL WEEVIL. 23 TS SEER 2 eS Sa ee ee ee ae re rhe 05 _ Messrs. Norden & Co., of New York, have made a conservative estimate of the average annual loss in the various States, as follows: . Per cent. : NES Se Sl TS Cee Sen ee a eee rr ee 15 i NB ills : ROP fn Me Ne ne ee me oe Bete ee 15 reer a covers were k ie east ii LY Ah DOAN LS 21 The Bureau of Statistics of this department estimated the losses to the cotton crop in 1909 from various causes as shown below: ! TABLE II1.—Amount of injury to cotton crop of 1909 due to various causes. Loss in seed cotton per acre from— State. oh Me 3 Pe Gimatic| Boll | Bole | omer | Plant | Miscelle| Seeman. weevil. | worm. | insects. | diseases. | Go ices. Pounds. | Pounds. | Pounds. | Pounds. | Pounds. | Pounds. | Pounds. | La TESA Ae 2S Se arenes etree 112.2 21.5 2.5 0.7 14.4 0.7 152.0 TES CURR a Se ape 38.8 148.8 8.5 15a) 11.0 1.4 209.8 ST SST CERES ee eae 103.3 14.1 8.0 0.7 18.8 Syl 148.0 DEMOS! S28 Usk cone oe - 147.3 11.0 3.7 0.4 2.2 3.4 168. 0 (LDS Lee Ratile e eaeee 100. 4 37.6 8.7 0.0 Tet 0.6 155. 0 Average of infested region - 100. 4 46.6 6.2 0.6 10.8 1.8 166.4 According to this estimate, the boll weevil was responsible for 28 per cent of the loss in the five infested States and 14.9 per cent of the loss in the United States. Thisloss was estimated as 1,267,000 bales of 500 pounds, which, at the current price of cotton in 1909, would be worth $88,056,500. _ Although the estimate of the Bureau of Statistics may be high, it was based upon the reports of numerous trained observers throughout the infested territory. Frequently misconceptions arise regarding the manner in which the weevil has affected cotton production in Texas. This is due to the fact that the total crop of the State has been maintained more or less regularly since the advent of the pest. In order to obtain exact information on this point we must examine the statistics of produc- tion in different parts of the State.’ It is necessary to divide the State into three areas. These are eastern, central, and western Texas. The divisions are made in accordance with variations in normal annual precipitation and other factors. Eastern Texas as used in this bulletin is bounded on the west by a line running practically north and south from the western 1Crop Reporter, vol. 12, No. 12, p. 94, December, 1910. ; 2 The following four paragraphs and table are extracted, with afew modifications, from Circular No. 122, Bureau of Entomology, pp. 5-8. 94 THE MEXICAN COTTON-BOLL WEEVIL. line of Lamar County to the western line of Brazoria County. In this region the rainfall is 45 inches per year or more. It comprises the counties listed below. Practically the whole area is covered with forests. It covers 40,180 square miles. Central Texas com- prises a broad belt from the Gulf to the Red River, beginning on the © west with the limit of the belt of 32 inches normal annual rainfall, and extends eastward to the line just described as defining the western boundary of the eastern Texas area. Central Texas consists of 45 counties ? and comprises 38,868 square miles. It is for the most part prairie country, although there are wooded valleys and occasional strips of timbered uplands. Western Texas comprises the remainder of Texas, beginning with the line marking the western limit of the area of 32 inches normal annual being tion. It is largely a prairie region, though wooded valleys are numerous. Another factor in differentiating western Texas from central Texas is the increased elevation. A careful study has been made of the manner in which the weevil has affected the production of cotton in the three regions mentioned. Use has been made of the Census records of production from 1899 to 1910, a period of 12 years, as shown in Table IV: TABLE 1V.—Eastern, central, and western Texas cotton production compared, 1899-1910 from United States Census. [500-pound bales. ] Eastern. Central. Western. 3 Years. ress Propor- pe tion o tion of tion o Bales qieete Bales Meese Bales. We crop crop. crop. Per cent Per cent Per cent 1 RS) oe a a ed 637, 872 22.44] 1,633,618 62. 61 337, 528 12. 94 ee re re ee en ee 811, 413 23.59 | 1,892,669 55. 04 734, 304 21. 36 OS on te en eee, Aas 633, 620 25.32 | 1,448,872 57. 90 419, 674 16. 77 AU PA eee Nias a Se ae ee ce 736, 660 29.48 | 1,332,487 53. 34 428, 866 ty a by Reese es ecco ea os ee or 545, 288 22.06 | 1,242,654 50. 28 683, 139 27. 64 Average, 1899-1903.............. 672,970 24.88 | 1,510,060 55. 85 520, 702 19. 26 i AUD a ORE ie ap eg ae Sie SAE ere ae om Se, ee 720, 671 22.91 | 1,700,224 54.15 724, 475 23. 07 De ee ee eee orn 329, 523 12. 96 1,414,115 55. 63 798, 294 31. 40 Yh Cok hye Solow PR Saat ne eae or ne panes 672, 497 16.11} 2,213,863 53.03 | 1,287,846 30. 85 Pee et ee res oe ee we CE EE 343, 328 14.92} 1,218,143 52. 95 738, 7 32.11 DO se Pa Bek ee ag aR OR ee oe 515,038 13.50} 1,980,7 50.60 | 1,318,681 33. 68 A 9S fei i Sage eo aes ae ee eee a 474,311 18. 80 1, 362, 096 53. 99 686, 404 27. 20 Lee ee Se SE ee Nee eS ee 645, 158 7 Hag 1, 677, 688 55. 02 726, 553 23. 83 Average, 1904-1910.............. 528, 647 17.19 | 1,652,414 53. 62 797, 280 28. 88 In eastern Texas the production for five years ending with 1903 averaged 24 per cent of the total crop of Texas. During the same series of five years western Texas averaged 19 per cent of the total ' Red River, Bowie, Franklin, Titus, Morris, Cass, Wood, Camp, Upshur, Marion, Harrison, Smith, Gregg, Cherokee, Rusk, Panola, Nacogdoches, Shelby, San Augustine, Sabine, Angelina, Trinity, San Jacinto, Polk, Tyler, Jasper, Newton, Liberty, Hardin, Orange, Jefferson, Chambers Galveston, Lamar, Delia, Hopkins, Rains, Van Zandt, Henderson, Freestone, Anderson, Leon, Houston, Madison, Waller, Grimes, Walker, Montgomery, Harris, Fort Bend, and Brazoria. * Central Texas counties: Cooke, Grayson, Fannin, Denton, Collin, Hunt, Tarrant, Dallas, Rockwall, Kaufman, Johnson, Ellis, Bosque, Hill, Navarro, McLennan, Limestone, Bell, Falls, Williamson, Milam, Robertson, Brazos, Travis, Lee, Burleson, Washington, Hays, Bastrop, Caldwell, Fayette, Colorado, Austin, Guadalupe, Gonzales, Lavaca, Wharton, Dewitt, Goliad, Victoria, Jackson, Refugio, Calhoun, Matagorda, and Aransas. * Including counties grouped by Census under “ All other.”’ LOSSES DUE TO THA BOLL WEEVIL. 25 crop. For the seven years ending with 1910 the eastern Texas pro- uction dropped to 17 per cent of the total crop of the State, while the production in western Texas advanced to 28 per cent of the total crop of the State. In other words, the portion of the Texas crop roduced in one area has decreased 21 per cent, and in the other it ‘ fxs increased 53 per cent. This increase in the west, where the dry | climate reduces the boll-weevil injury, served to offset the loss in ~ eastern Texas and thus accounts to a great extent for the fact that the total crop of the State has not fallen off. Mr. F. W. Gist, of the Bureau of Statistics of this department, has made a very careful study to determine the center of cotton produc- tion in Texas for each year from 1899 to 1908. As would be sup- posed from the figures that have been given, it was found by Mr. Gist that the center of production had moved considerably to the west- ward. In fact, this center moved from 30.78 miles east of the ninety- seventh meridian in 1899 to 19.14 miles west of this meridian in 1908. This was a westward movement of practically 50 miles. The center of production in 1899 was on a line passing north and _ south through the eastern Cortion of Grayson pounty,in Texas. In 1908 the center had moved to a line pass- ing parallel with the other through the western portion of Cooke County, in Texas. These state- ments may be illus- trated by the follow- ee (fig. 2). he statistics which have been given show ROBERTSO the entire fallacy of fad a ek ea, eee oe ne co cemant of the cents the seriousness of the HEPEME TuRcoltonipHaduction westward: (Oneal) 1 ae boll-weevil problem by considering only the total crop which has been produced in Texas for some years past. It is absolutely necessary in estimating the damage that is fikety to be done in any certain region to find the on of Texas in which the climatic and other conditions are most ike those in the region that is being considered. In Texas there are several very distinct boll-weevil problems due to local conditions, exactly as there are numbers of distinct agricultural provinces. The future of the boll weevil in the eastern part of the United States can not be foretold unless the manner in which the insect has affected the portion of Texas which is most like the eastern part of the belt is considered. An investigation of this matter will show that the eastern part of Texas is the only part of the State which is like the eastern portion of the cotton belt in the climatic and other features which react upon the boll weevil. This is especially the case with 26 THE MEXICAN COTTON-BOLL WEEVIL. reference to precipitation, the presence of timber, and temperaturé It is clear, therefore, that the only criterion by which to judge the future damage of the weevil is the effect it has exerted on production in eastern ‘l’exas, where, as has been shown, there has been a consid erable decrease in production. INDIRECT LOSSES CAUSED BY THE BOLL WEEVIL. The foregoing discussion has dealt altogether with the direct losses — caused by the boll weevil, but it is to be noted that there are certain | indirect losses which must be considered. It is not alone the farmers — who are affected. The reduction in the size of the cotton crop imme- | diately affects the ginning and oil-mill industries in which large — amounts of money are invested. The railroads, banks, and mer- chants are also concerned. In fact, the disturbance extends through- out the community. In the case of many parishes in Louisiana one — of the first results of the invasion of the boll weevil has been the reduction in the assessed valuation of farm lands. In all regions, for at least a short time, the price of farm properties has been reduced. — Likewise in many localities the invasion of the insect has caused the exodus of large numbers of tenants and even of landlords. In the — former case landowners have found themselves without the labor to — run their places. Losses due to such disturbances can not be esti- mated, but it issafe to say that theyreach an aggregate amount at least equal to the direct losses which are caused. | COMPENSATIONS FOR LOSSES CAUSED BY THE BOLL WEEVIL, ~ In spite of the great losses caused by the boll weevil it must be rec- ognized that certain compensations are returned. The insect forces a diversification of crops. There is no doubt that there is a tendency to place too much dependence in the South upon the cotton crop. When the ravages of the boll weevil reduce the size of this crop mate- rially or make production of a cotton crop hazardous, the farmers must change their system of cropping materially. This results directly in diversification and animal husbandry, and thus tends toward a more logical and profitable system of agriculture. Of course it would be much better if this change could be brought about by less revolutionary means and with less loss than is caused by the boll weevil. The tendency for many years has been toward diversification, which was certain to come in time. The boll weevil has undoubtedly hastened it and has thus in a broad sense offset, to a certain degree, some of the direct losses which it has caused. It is to be noted, how- ever, that in many cases this forced and, in one sense, premature diversification of crops has resulted disastrously. In some localities extensive and rapid growth has taken place in fruit raising and market vardening. In some of these instances the new industries have devel- oped with abnormal rapidity and without the proper foundation. This was the case in extensive plantings of potatoes made in 1909 by the cotton planters of Avoyelles Parish, La. The result has been that unless carefully managed the new lines of farming have failed and there has been a tendency to return to the cultivation of cotton. ‘The boll weevil also tends to eliminate the indifferent and unprogres- sive farmer. Te is driven either to the city or to some other locality. PROSPECTS. 27 In this way the weevil works toward the production of a better class of farmers. Of course, no community favors a reduction in the number of inhabitants. It would prefer that the inefficient remain and be improved by education or otherwise. This effect of the invasion of the me weevil, therefore, can not generally be looked upon as a benefit. PROSPECTS. The rapid spread of the boll weevil in the past few years and its apparent adaptability to most of the conditions prevalent in the cotton region of the United States indicate that it will ultimately be able to exist in all except the semiarid portions of the entire cotton- growing country. In order better to estimate the probable move- ment in the future, we present Table V to illustrate its progress since the year 1892: TaBLE V.—Annual movement of the boll weevil in the United States. Weevil advance. Total Total Year. move- area in- Tsseas Louisi-| Okla- | Arkan-| Missis-] Ala- Flor- ment. fested. : ana. | homa. | sas. sippi. | bama. | ida. Sq. mi. | Sq. mi.| Sg. mi. | Sq. mi. | Sg. mi. | Sq. mi. | Sq. mi.| Sq. mi. | Sq. mi. Rene te eA! “oral dll eke GS at Ge ad NAS UN eed [Mlaieiicen Danica 1, 400 1, 400 Jol Seer eee 7 NU eee eal (EE Stee 2s || SS ras ae Bee eas) nee Pega ae a a 7,400 8, 800 2 eb aa SR eee le ees, ee ee 10, 300 19, 100 Lo DSL) Sa Bo oe ee ROTO [en eee ies eerste eta roe ecto eae een oe aloe ole 7,900 27, 000 > MS ae O° UOT cee AR. 2 ea gs ee ees ee eee ee nr (ee 17,300 19, 700 og LESSER ae eee PERE Se eee Meera top ele cee lame cee 9, 600 29, 300 TASER eee oe Bernier, okie: hi n/N L eg eet EL eee she 7, 200 36, 500 eae ite ELE) EUR lee a lin emi tila (oP 6, 600 43, 100 ee lest Ricoh: oe elise folic. RICE SORTER 7 6, 600 49,700 | ae T/L) [16 ne Fe | eee (ee te (re oe ea | ee nee 6, 700 56, 400 2 ESR AR Seas apes ME er a ele Ss on ern |S ean Se ee ee lee. 11, 600 68, 000 _ | | Se ST pase 11,700 SOON K SSic8 2a ace eee eta ssa eta tera ieee 12, 000 80, 000 a ROR OED RRC Oe a od (ees See ns ial eer 46,900 | 126, 900 BLAS . Seo cas S88 EL 0 ae a a Oe ee ere (eee 20, 400 147, 300 UL See Se ee 22,600 | 9,300} 4,200 BOO hs 3372.5 8S see aoe S ae 36, 600 183, 900 Sed SGI nM eS MS a 5,000 | 8,200} 7,800 GODS ee co seyel| eater 21, 500 205, 400 es CEE Se eee Be FOOT ESO 6 7500"]> 4,800 1 e552 seo. 2 18, 500 223, 900 ee ae ee 9,800 | 1,900] 7,500] 10,700 |........|.....-.. 29,900 | 253) 800 12 2S ey Ba P00 T2002 16,500 | 1,900 | 13,500 | 3,900 |........ 14, 200 268, 000 a Sty ee ee 13,000 | 9,700} 11,000] 5,400] 1,400] 3,500] 271,500 Motte: si este | 139,300 | 40,800 | 6,300 | 31,900 | 40,500 | 9,300} 1,400 | 271,500 |.......... | 1 These figures. indicate losses instead of gains. A summary of Table V in three-year periods is given below: TaBLeE VI.—Average annual rate of boll-weevil movement. Total Yearly | Average of Three-year periods. movement.| average. | averages. Sq. miles. | Sq. miles. | Sq. miles. OOS vel Digs: “led... D> «eae SE ee ee ee ee 19, 100 6, 366 ee gale al ae 10, 200 3,400 |... .-22-ucaes TS S70 i pe ea ee 20, 400 6, 800 5, 522 LUE M e e 30, 300 10. LOO! 15a. - = opts CTL Eo OO lye) ys 2 ga SSR SO SA 103, 900 34; 633s|> 2. cues isi eos 2) 5 a ee ee rs el er CH a,- 69, 900 23, 300 22, 677 DeISOO |y ads eee 14, 099 At the end of 1910 the total area infested was 268,000 square miles, a net gain of 14,200 square miles over 1909. Including the year 1910, the average rate of movement in the United States beginning with 28 THE MEXICAN COTTON-BOLL WEEVIL. es 1904 has been 27,000 square miles a year, with 402,000 square miles of cotton-producing area yet free. It is therefore reasonable to estimate that it will take at least 15 years before the entire cotton region of this country can become infested. _ ay It is evident, however, that the weevil will find certain definite checks in the cotton-growing regions of this country. Among the more important of these checks are (1) dryness, (2) low winter temperatures, (3) altitude, and (4) such combinations of these factors as tend to form definite life zones. The possible effects of these factors will be discussed separately. Dryness is the most important check the boll weevil experiences. The insect has repeatedly advanced into western Texas, but has invariably been prevented from gaining a foothold by the dry climate of that region. Occasional wet seasons have resulted in apparent gains in that quarter, but they have been nullified by the recurrence of normal years. The extremely dry conditions in Texas, Oklahoma, and Arkansas during the summers of 1909 and 1910 had a remarkable effect upon the weevil. Combined with the very severe winters, these dry summers practically excluded the weevils from the western half of the infested region of Texas and most of the infested region in Oklahoma. The damage done in these regions for two seasons has occurred only after the breaking of the intense summer heat. The occasional occurrence of a dry summer, however, does not give any promise of future immunity from the boll weevil, because its tendency to disperse in the fall in all directions enables it to regain any ground which it might lose during such a season. It is also important to note that the practice of irrigation in dry regions may counteract the effects of the lack of precipitation and enable the weevil not only to maintain itself, but to cause considerable damage. The low temperatures of the winters of 1907, 1908, and 1909 had a very pronounced effect upon the numbers of the weevil in the follow- ing years. An analysis of the minimum temperatures reached in the regions where the weevils were most affected indicates that such control was the result of a temperature of 12° above zero. In some places where this temperature was reached there were earlier low temperatures which may have forced the weevils into considerably heavier shelter than they would have selected normally. This apparently enabled the weevils to survive even a temperature of 5° ee zero. Although the information at hand is rather Incomplete, we can nevertheless hold out some hope that regions having a mini- mum temperature of from 5° to 10° above zero wil have little trouble from the bol weevil. In later sections of this bulletin we will show how even higher minimum temperatures can greatly reduce the weevil damage of the followimg year. The weakness of predictions of this kind is that they do not take into account the fact that the weevil is rapidly adjusting itself to changed conditions and that eventually the result of natural selection will be a class of weevils which can with- stand greater vicissitudes than those of the present. The extremely slow progress into western Texas might be explained on the basis of altitudes. So far, the weevil has not established itself at an altitude above 2,000 feet. It may be possible that this altitude is its extreme limit. Again, there is danger in this assumption, Bul. 114, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE Il. THE BOLL WEEVIL AND INSECTS OFTEN MISTAKEN FOR IT a, The cotton boll weevil, Anthonomus grandis; b, the mallow weevil, Anthonomus fulvus; c, the southern pine weevil, Pissodes nemorensis; d, the cottonwood-flower weevil, Dorytomus mucidus; e, Conotrachelus crinaceus; f, the pecan gall weevil, Conotrachelus elegans. (Original.) : INSECTS MISTAKEN FOR BOLL WHIEVIL. 129 because the boll weevil has shown considerable adaptability in the past and may be able to adapt itself to higher altitudes than it has yet reached. With regard to the possible relation between life zones and the distribution of the weevil it is to be said that at present the infested territory includes the tropical regions of Cuba, Central America, and Texas, and a considerable part of the Austroriparian Zone of the Lower Austral Region in the other Southern States. It is interest- ing to note that the weevil has not yet succeeded in establishing itself in the Upper Sonoran Zone of the Upper Austral Region of either Mexico or western Texas. It has invaded, or at least sur- rounded, two isolated areas of the Carolinian Zone of the Upper Austral Region in Oklahoma and Arkansas. Considerable cotton is grown in western Texas, in the Upper Sonoran Zone. There also | exist in Arkansas, southern Missouri, Tennessee, northern Georgia, northern South Carolina, western North Carolina, and Virginia large | regions of cotton-producing territory included in the Carolinian Zone. It is possible that the boll weevil will be unable to establish itself permanently beyond the limits of the Lower Austral Zone and this would exclude it from the regions just mentioned. As a matter of fact, the effects of climatic conditions upon the weevil are so powerful that there may be occasional diminution in the serious attacks from the insect in the moist regions, such as was | experienced in the summer of 1911. The season of 1911 was unusual } in Louisiana and Mississippi, starting with severe cold in January, | which cut down the emergence from hibernation to 0.5 per cent, i and continuing with a very unusual drought. Such conditions are | not often experienced, and we may usually expect severe attack by the weevil in southern Louisiana and the Delta of Mississippi. INSECTS OFTEN MISTAKEN FOR THE BOLL WEEVIL. | The anticipated appearance of a serious pest such as the boll weevil in hew regions causes greater attention to be given to the insects found in the cotton fields. Many planters notice common native insects which appear to answer the description of the boll weevil. The result of such mistaken identifications is generally a local panic. On account of the difficulty of distinguishing the boll | weevil from a large number of related insects, we advise that whenever a planter discovers an insect which he suspects to be the boll weevil he send it either to the State entomologist or to the Bureau of Ento- mology and receive authoritative information.! 1 Addresses of officials who will give authentic determinations of the boll weevil: Alabama.—W. E. Hinds, Auburn. Arkansas.—Paul Hayhurst, Fayetteville. Filorida.—E. W. Berger, Gainesville. Georgia.—K. L. Worsham, Atlanta. Louisiana.—J. B. Garrett, Baton Rouge. Mississippi.—R. W. Harned, Agricultural College. i North Carolina.—Franklin Sherman, jr., Raleigh. Oklahoma.—C. E. Sanborn, Stillwater. South Carolina.—A. F. Conradi, Clemson College. | Tennessee.—G. M. Bentley, Knoxville. Texas.—Wilmon Newell, College Station. Ernest Scholl, Austin, Department of Agriculture. W. D. Hunter, Bureau of Entomology, Dallas. Virginia.—E, A. Back, Blacksburg. 30 THE MEXICAN COTTON-BOLL WEEVIL. Many of the weeds in the vicinity of the cotton fields are attacke by different species of weevils which may in some respects resembl the boll weevil. Some of these weevils are of a general dark color and have beaks with which to puncture theirfood plants. Oncloseobserv tion it will be found that the weevils which are discovered on other weeds are breeding in those weeds. They are not the boll weevils and will not attack the cotton. Many of these native weevils are also found on the cotton plants at the nectar which is produced by the — squares, blooms, and leaves. These weevils simply visit the cotton plants in order to feed upon this nectar and do not injure the plant in any way. The following list contains the names and references to the habits of some of the most common weevils which occur in and about cotton fields: Insects often mistaken for the boll weevil (Anthonomus grandis Boh.). (P1. II, a.) Weevil. Attacks. Anthonomus albopilosus Dietz......-.---- Seed pods of wild sage (Croton). Anthonomus eugenit Cano. ....------------ Pepper pods. Anthonomus fulvus Le C. (Pl. IT, 6)...--. Purple mallow buds. Anthonomus signatus Say..........------ pari CUE dewberry, and strawberry uds. Anthribus cornutus Say.....-.--.--..-----| Cotton stems. Arexcerus fasciculatus DeG....-.--.------- Ghana coffee beans, and old cotton olls. BOUENUS NOSICUS BAY 22257 = 2s = EES Acorns. Balaninus victoriensis Chitt........-...--- Live oak acorns. RFS STRAT SAY = jon 2% Koes Sa x re Se ee Roots of ragweed (Ambrosia). ATIS LON SULTS DAY. oe ee Roots of cockle-bur (Xanthium). Chalcodermus eneus Boh......-...------- Cowpea pods. Conotrachelus elegans Say (Pl. II, f)..---- Galls and nuts of pecans. Conotrachelus erinaceus (P1. II, e).........| Habits unknown. Conotrachelus leucophxatus Fab...........| Stems of careless weed (Euphorbia). Conotrachelus naso- eC... 2.2. --..- o2022 Acorns. Conotrachelus nenuphar Hbst..........---- Fruit of plums and peaches. Desmoris constricius Say. :.o. 522 5326 £222: Seed of sunflower (Helianthus). Mesmoris-scopatis eG. . 225s: 2 tebe. Flower heads of broad-leaved gum plant (Sideranthus). Dorytomus mucidus Le C. (Pl. II, d).--.-. Cottonwood catkins. Epicerus imoricaius Say... 2225... | Habits unknown, adult feeds on foliage. Gerzus penicellus Hbst... 22. 2 oes 8 | Habits unknown, visits cotton nectar. Gerxus picumnus Hbst............-.-.--- | Habits unknown, visits cotton nectar. Gersteckeria nobilis LeC..........------- Joints of prickly pear. REINS, DUNES TA DAG he odo a ce se a Pine bark. Tarus scrobicollis Boh................---- | Stems of ragweed (Ambrosia). Pachylobius picivorus Germ...........---- Pine branches and bark. Pissodes nemorensis Germ. (Pl. Il, c)..-.-. Pine branches and bark. Rhynchites mexicanus Gyll...........-.--- Rosebuds. Rhyssematus palmacollis Say.........-.--- Morning-glory pods. Trichobaris mucorea LeC..........------- Tobacco stalks. Trichobaris tevana LeC...............---- Spanish thistle stalks. (Solanum _ ros- tratum). Tychius sordidus LeC.:.-...- 2... 2.5.28. Pods of false indigo (Baptisia). Many other insects are sometimes mistaken for the boll weevil. "his list includes only the species which are more or lesss closely allied to that insect and consequently more commonly confused with it. FOOD PLANTS. oe FOOD PLANTS OF THE BOLL WEEVIL.' The careful investigations of Mr. E. A. Schwarz in Guatemala, Mexico, and Cuba have convinced him that the original food plants of the boll weevil are the tree cottons of those countries. One of these species has the seeds adhering together in a mass and is called “kidney” cotton from the shape of this mass. The other has seeds separated as in Upland cotton of the United States and is probably the Gossypium brasiliense of botanists. The former appears to be the more ancient form and presumably is the species upon which the weevil originally subsisted. Cotton is now rarely cultivated in Cuba, but the practically wild tree cottons are found throughout the island, and on these the boll weevil is generally to be found, although in very small numbers. There are, however, frequently found through- out the island isolated plants which are not infested. The areas of cultivation of cotton in Guatemala are extremely isolated, but the presence of tree cotton perpetuates the weevil and gives it a rather general distribution. In Mexico the principal regions of cotton erowth are represented by narrow belts along the two coasts and a large area in the north-central portion known as the ‘‘Laguna.”’ Tree cotton probably serves to continue the boll weevil’s activity in many parts of Mexico where cotton is not cultivated. It is impos- sible to decide whether the boll weevil originated in Cuba or in Central America, as it occurs in practically the same condition in both places. It is, however, practically certain that the insect has attacked the cotton plant from antiquity. In fact, there is nothing to indicate that it ever had any other food plant. The question of the possibility that the boll weevil may feed upon some plant other than cotton is one of importance. As an illustration we may state that as long as cotton is extensively produced in any given region there is comparatively little danger, but if a certain region should forego the planting of cotton for a period of years in order to escape pes dine and then resume its cultivation, it is apparent that all efforts would fail if the boll weevil could in the meanwhile exist on other native plants. It is a well-known fact that insects which have few food plants usually confine their attacks to closely related plants belonging to the same botanical family or even genus. The native plants most closely allied to cotton in the regions so far infested are the various species of Hibiscus and the trailing mallows of the genus Callirrhoe. Careful tests have been made with these plants and with many unrelated plants, both as to their powers of sustaining life and the inducements offered for oviposition. Six species of Hibiscus, namely, esculentus, vesicarius, manihot, moscheutos, militaris, and africanus, have been tested to ascertain how long the weevil could live on them and whether it would oviposit in the fruit. In experiments conducted by Dr. W. E. Hinds hibernated weevils starved in an average time of about four days with leaves of either Hibiscus esculentus or H. militaris. Weevils 1 There has recently been discovered by Prof. C. H. T. Townsend another serious cotton pest, A ntho- nomus vestitus Boheman, which we may designate as the Peruvian cotton square weevil, as it is not at pres- ent known outside of Peruand Ecuador. Prof. C. S. Banks has also discovered in the Philippine Islands a weevilfeeding in cotton flowers which may be known as the Philippine cotton flower weevil. This species has been described as Ecthetopyga gossypii Pierce. The coffee-bean weevil, Arxcerus fasciculatus DeGeer, frequently breeds in old dried cotton bolls, and the cowpea pod weevil, Chalcodermus xneus Boheman, breeds occasionally in fresh cotton squares in fields of cotton following cowpeas. On account of the exist- ence of these other square and boll weevils it is still necessary to retain the original name Mexican cot- ton boll weevil for Anthonomus grandis Boheman. 82 THE MEXICAN COTTON-BOLL WEEVIL. — of the first generation which had fed upon no cotton were placed wy Hibiscus militaris, and these starved within an average of three four days. The first-generation weevils which had fed for a few dé on squares were placed upon leaves, buds, and seed pods of Hibise vesicarius. Though they fed alittle, all starved in an average of abo five days. ....... ag (oP aes, Be | 145 L771: Lilo ees +29.0 Motel: fresco 156 90 | 10.996 | 40,234 | 10,190 |...6-...4- 2). 2 a BVEragee S20 sss ee i eee peear eRe 3.6 2.4 44.7 { ‘ Modified from Bulletin 51, Bureau of Entomology, p. 52. PLATE V. Bul. 114, Bureau of Entomology, U. S. Dept. of Agriculture. EFFECTS OF BOLL-WEEViL ATTACK ON LEAF AND SQUARES. a, Cotton leaf much fed upon by adults; 6, square with two egg punctures; c, flared square with many feediug punctures; d, square prevented from blooming by puncture; e, bloom injured ’ by feeding punctures; f, poor blooms caused by feeding punctures. (Original.) —— SEASONAL HISTORY. 41 ABILITY TO LOCATE COTTON. When, hibernated weevils emerge from their winter quarters in search of food they are frequently long distances from the nearest cotton field. It has been a question of considerable interest whether the weevils are able to locate cotton or whether they find it by chance. Dr. A. W. Morrill conducted a series of experiments in the laboratory to test the attraction of cotton squares for the weevil, but the results were not conclusive. In the eight years of study of the boll weevil, _ there have been very few records of weevils on any other plants than cotton, notwithstanding the fact that special collections were made in the woods and fields near the cotton fields in search of boll weevils. In the season, of 1905 extensive collections were made by means of sweeping nets by several men for weeks during the dispersion season, and yet not a single weevil was found outside of the cotton fields. _ All of this would indicate that there is some attraction of the weevils to cotton. The concentration of weevils upon the earliest plants in the spring and upon the greenest and most luxuriant portions of the fields in the fall are also evidences of the ability of the weevils to find desirable places for feeding. FEEDING HABITS OF HIBERNATED WEEVILS. Whether there be few or many hibernated weevils makes no differ- ence in their feeding habits. The stage of the cotton at the date of emergence determines largely the nature of the food habits at that time. The first weevils to emerge obtain their food from the tender, rapidly growing, terminal portions of the young plants. They place themselves upon the node where the two cotyledons branch. In fact, this seems to be the point usually attacked in cases of very young cotton plants. In almost all cases the puncture of the weevil at this point results in the death of the plant. Sometimes the attack is made a little above the node on a petiole of the cotyledon, in which case the one cotyledon falls and the other remains, and the plant usually recovers. However, it frequently happens that the same pedvil attacks both of the cotyledons. This form of attack is fatal to the seedlings unless they have become very vigorous—sometimes until they have developed two true leaves. Later the central bud, young leaves, or tender stems are attacked, and upon these the weevils easily subsist until thesquares aredeveloped. (SeePI.V,a.) Incases where the emergence from hibernation is very large the weevils may come out in such numbers upon the newly sprouted cotton as to stunt or even kill the growing plants by their depredations upon the terminal portion. Weevils which have fed upon tender tips of plants seem perfectly satisfied with their food supply, and it appears that their first meal upon squares is largely the result of accident. After having begun to feed upon squares, however, it appears that their taste becomes so fixed that they normally seek for squares. : In the spring of 1895 Mr. E. A. Schwarz found the first emerged hibernated weevils working upon plants which had sprung from 2-year-old roots. In thespring of 1903 in one field of comparatively early cotton, 2 or 3 acres in extent, the senior author found, between April 24 and May 11, 23 weevils working on the buds and tender leaves of stubble plants before a single weevil was found on the 42 THE MEXICAN COTTON-BOLL WEEVIL. | young planted cotton having from four to eight leaves. At Victoria, early in June, 1902, Mr. A: N. Caudell found, in examining 100 stubble plants growing in a planted field, that fully one-half of the squares upon these plants were then infested. The planted cotton was just Beene to form squares and was slightly injured at that time. It appears, therefore, that stubble plants, where such exist, receive a large part of the first attack of the hibernated weevils, not because of any special attraction, but for the reason that they are present long before the planted cotton has come up. The occurrence of volunteer and stubble cotton in the fields in the early spring is of considerable importance in the boll-weevil problem. Throughout the coast regions, especially of southern Texas, stubble cotton is very common in the fields, and there is hardly a region of the South where volunteer cotton can not be found before the normal planting is up. (See Pl. VIII, a.) It is Ke no means certain that all or even a large proportion of the hibernated weevils may be found upon the early plants, and this renders their use as traps entirely impracticable. A number of observations have shown that weevils frequently occur upon the pee cotton, even when numbers of vigorous stubble plants may »e found within a comparatively short distance. In fact, at Victoria, Tex., in 1904, many weevils were found feeding upon the planted cotton for more than six weeks after the stubble plants were producing fruit. DESTRUCTIVE POWER BY FEEDING,! A glance at the figures in Table VIII is sufficient to show the creat destructive power of the Mexican cotton-boll weevil. It may be seen that both in the field and in the laboratory the weevils of the first generation are more active in making punctures than are the hibernated weevils. These generations overlap too far to justify us in attributing this difference to the influence of a higher temper- ature alone, though this factor will account for a large part of it. A comparison of the figures for males alone with those for females alone or with those for males and females together shows that it is very conservative to state that males make less than half as many punctures as do females. By the habit of distributing their punc- tures among a greater number of squares the destructiveness of the females becomes at least five times as great as that of the males. This great capacity for destruction has been one of the most evident points in the history of the spread of the weevil and has deeply impressed the entomologists who frst studied the insect in Texas. In 1895 Mr. E. A. Schwarz, in writing of the work of the weevil at Beeville, said: Each individual specimen possesses an enormous destructive power and is able to destroy hundreds of squares, most of them by simply sticking its beak into them for feeding purposes. ATTRACTIVENESS OF VARIOUS SUBSTANCES. _ Experiments have proved that the report which has sometimes been circulated to the effect that cottonseed meal attracts the weevil is due to mistaking other insects for it. Many tests, both in the laboratory 1 Extracted from Bulletin 51, Bureau of Entomology, p. 61. |: fl gz SEASONAL HISTORY. 43 and in the field, have shown that sugar and molasses, either in solution or otherwise, have no attraction whatever for the weevil. Honey exerts a very weak attraction, but not enough to be of any practical use in control. In fact, it has not been found that any substance exerts a special attraction for the weevil. The experiments have dealt _ with many chemicals as well as plant decoctions. SENSE OF COLOR. A series of interesting observations on the color sense of the boll _ weevil was made by Mr. C. R. Jones at Calvert and Victoria, Tex., and . Alexandria, La., in 1907. Tubes of different colors were placed in a box, all with an equal amount of sunlight, and the weevils were given food. The observations were made at intervals during the day, and each time the weevils were all shaken back into the box. Table IX | shows the total number of weevils found at each color for the series of _ observations and also the weighted average attractiveness. Fourteen _ shades were used, but these may be grouped under eight colors. The three most attractive shades were lhight-blue, dark-green, and light- pink. While itis rather difficult to explain the results, it nevertheless | appears that there is some preference for certain colors on the part of | the weevil. TABLE 1X.—Relative attractweness of colors to the boll weevil. Number of | Number Average Color. observa- | of weevils | attractive- tions. attracted. ness. Per cent. CB TME. . 2 SS aos Es a ee ae al ae 64 461 Wee, HEB E. 5 uptic led AGA eis Be cle cae pny I ST a ea oO 43 261 6.0 DEEP Sb as See ee ee eg mr an me Vg 32 123 3.8 (NO). seaSar oc See ce Ce es SSE Ee Ses ie a ieee a et 107 411 3.8 ON) HERD So ad aad i 0 oy tee SE A 11 24 Dal SUT ssa sds Hesse Ra Gee 8S 5 Be Aes AB a ea Sica a eet 32 29 8 DEED cA eon ened see ete ee aI A a A ee 10 5 a A ee eas a ng aes paar ae ilo yO Ms ik as NT 21 6 ae, MOVEMENTS ON FOOD PLANT. Various observations have been made to determine the amount of - movement of weevils at night. InJuly, 1904, at a mean temperature of 76.3° F., Mr. A. C. Morgan found, in an aggregate of 134 weevil nights, that eight weevils had moved but 25 times. Each weevil _ had moved only once every six nights. On cloudy days weevils are _ much more sluggish than on sunny days. Relative humidity influ- ' ences the activity, but no definite observations on this point have been ! made. The effect of temperature on locomotive activity may well be illus- trated by a series of laboratory experiments conducted by Dr. A. W. | Morrill. A thermometer was passed through a cork and inclosed in a test tube, which in turn was placed within a hydrometer cylinder of sufficient depth to inclose it. Weevils were inclosed in the test tube _ with the thermometer, and the temperature of the cylinder was varied either by heating gently or by the use of ice water. Starting with the thermometer at 64° F., the 10 weevils inclosed were found to move slowly, half of them being quiet. As the temperature was gradually 44 THE MEXICAN COTTON-BOLL WEEVIL. raised the activity of the weevils increased up to 105° F. When the temperature reached 95° F. or over the weevils were running uj and down the tube. By filling the cylinder with cold water th temperature was lowered to 86° F., at which point the weevils began te cluster at the top on the cork and were crawling slowly. By the addition of ice in the cylinder the temperature was lowered to 59° F. at which point five weevils were struggling on the bottom of the test tube or clinging to one another, four were clustered on the stopper, while one was slowly crawling downward. At 50° F. six weevils at the bottom showed slight signs of life, and one was crawling slowly. At 45.5° F. slight signs of life were still shown, while « 40° I. occasional movements only were noted. When the tempers ture was raised weevils began crawling as 50° F. was passed, and at — 64° all had left the bottom and were crawling upward. Some recoy- |} ered more quickly than did others. The temperature was again lowered, this time by the use of salt with ice. All movement ceased at 37° F. The cooling, however, was continued to 33° F., after which it was slowly raised to 42° F., at which point movements began. - EFFECTS UPON SQUARES AND BOLLS OF FEEDING BY THE BOLL WEEVIL. eo 2 From numerous large, open feeding punctures a square becomes so severely injured that it flares very quickly, often within 24 hours. (See Pl. V, ¢.) Males usually make the largest punctures, which they always leave open while they remain for a day or more working upon the same square. It has been often found that squares thus injured by a male will flare before the weevil leaves it. The time of flaring depends upon the degree of injury and the size of the square. Thus small squares which receive only a single large feeding puncture in the evening are found widely flared in the morning. On the other hand, large squares which are within a few days of the time of their | blooming may receive a number of punctures without showing any — noticeable flaring. Frequently a square which has flared widely will | be found later to have closed again and to have formed a distorted bloom, and occasionally such squares develop into normal bolls. 9 (See Pl. V, e, f.) In squares of medium size a single feeding punc- § ture does not usually destroy the square.. The destruction of a 9 square by feeding results either from drying or decay which follows a | the weevil injury. Ge SN al ee 4 = - M TaBLeE X.—Destruction of squares by the feeding of the boll weevil. . | | Total |Numberof) otal Average Pee 7 | Period. number of gy tea tee number of ae numberof | squares feeding feeding punctures oo before e | punctured. punctures. punctures. per square. ailing. ai = — | cor — i DUNGB-JULG =o oot en ee ee eee 751 170 335 1.9 5.3 August-September ........................ 426 183 383 2.0 4.4 October-November... ...............-..+-- 176 74 216 2.9 15.2 ARO, cola bo Peers eee eee 1,353 427 934.4. .-:.bs. teehee pee Welptited averares:.. : 2s ce os ie ee ele eee Pe 2 2.0 7.0 Bul. 114, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE VI. INJURY BY BOLL WEEVIL TO SQUARES. a, Bloom checked by attacks of larva; b, square opened, showing grown larva; c, square opened, showing pupa; d, dwarfed boll opened, showing one larva and two pups; e, weevil escaping from square; f, emergence hole of adult in square. (Original. ) iL 7 Le Bc EES: BY BOLL WEE\ Y WIL SEASONAL HISTORY. 45 Table X shows that the number of feeding punctures per square is _ determined by seasonal influences, as is also the average number of _ days before falling. A comparison of the average time from the date of the attack to the falling of the square shows that squares __ which are only fed on, fall, as a rule, somewhat more quickly than do squares which only contain larve and have never been fed upon. ] axing takes place more rapidly as the result of feeding injury by the adult than from oviposition and injury from the developing stage. _ While only one egg is generally laid in a square, it appears from Table X that two feeding punctures are usually made in a square. Bolls are quite largely fed upon after infestation has reached its height. Small and tender bolls are often thoroughly riddled by the numerous punctures and fall within a short time. (See Pl. VII.) Larger bolls may receive many more punctures but do not fall. In bolls an abnormal woody growth sometimes takes the place of the _ punctured fiber, and a softening and decay of the seeds often accom- panies this change. One or more locks may be destroyed, while the remainder of the boll develops in perfect condition. ——— = SUSCEPTIBILITY OF VARIOUS COTTONS.! \ During 1903 and 1904 experiments were conducted at Victoria, _ Yex., to ascertain the relative susceptibility of several varieties of American Upland, Sea Island, Egyptian, and Cuban cottons. The observations at the laboratory were made by carefully examining the plants, looking into each square, and removing every weevil and infested square found. If there were any distasteful or resistant cotton among these it would surely be found in this way, and if any variety were especially attractive to the weevils it would be equally apparent. Since infested squares were removed, the accident of association or proximity would not determine the location of the weevils found, but all might be considered as having come to the cotton with equal opportunities to make their choice of food, and accordingly their location has been considered as indicating such choice. The period of observation extended from June to November, except with the Cuban cotton, which was planted late and began to square during the latter part of August. For the purpose of this comparison both the several varieties and the various plats of the American cotton will be considered together, as no evidence of preference was found among them. ) In making a comparison of the results three elements must be con- sidered for each variety of cotton: First, the number of plants of each . variety; second, the number of days during which each kind was | under observation; third, the total number of weevils found on each | class of cotton. The elements of numbers of plants and time under observation may be expressed by the product of those two factors | forming a term which we may call “plant days.’ The total number _ of weevils found upon any class of cotton divided by the number of { _ plant days will give the average number of weevils attracted by each | ~ plant for each day, and these numbers furnish a means of direct com- parison and show at a glance the average relative attractiveness of 1 The following discussion is extracted, but modified, from Bul, 51, Bureau of Entomology, pp. 61-64, 46 THE MEXICAN COTTON-BOLL WEEVIL. each class of cotton. The results of this series of experiments tabulated below: TaBLeE X1.—Relative attractiveness of various cottons to the boll weevil. Total. Average — = OO pL Relative — Class of cotton. ro =o as % a este attrac- plants.| Plant _ reed Bi tat squares | tiveness. days. | found. squares. per day. ea 1903. ASMOMOCAN. : o ---- 2-5 - or = one enn 62 | 4,920 287 | 3,507 | 0.058+ 12.24 bane = bh ecoeec posh ee aoa eee 5 120 11 136 -092— 12.4— Bs Bee IsIGnh Son cn oe eo eee tec een 8 552 64 | 1,089 . 116— 17.0+ 2.0 UP) NEN CSS 2 erp ar eo Soe A ae 8 808 207 | 2,013 256+ 9.7+ 4.44 Total of 3 non-American cottons. - 21} 1,480 282 | 3,238 -191— 11.5— 3.3— 1904. ANIOTICR ete ee 60 | 3,780 S46 Ne ee tee MOTE hi See bea aslanid >.) 2os' 88 oh see oe eee 5 315 LDS Sa cee SOL ence eee epyntiand) oot eh ec oe a 4 252 10222 ee .405— eesseseee: An examination of Table XI shows that American Upland cotton is less subject to attack by the weevil than any of the others, and that _ Egyptian (Jit Afifi) is by far the most susceptible. The weevils gathered so thickly on the Egyptian cotton that the plants could not produce sufficient squares to keep ahead of the injury, and therefore the average number of squares for each weevil is only three-fourths as great with that variety as with the less-infested kinds, but the average injury to each square was greater than with any other. It is possible that the greater amount of nectar secreted by the Egyptian cotton plants is responsible for this increased attraction of the weevils. The results are still further sustained by observations upon larger areas of American and Egyptian cotton under field conditions in three localities in Texas, no weevils being removed from either kind. At Victoria, Tex., on August 26, 1903, an examination showed that 96 per cent of Egyptian squares were infested, while an average of 13 fields of American showed 75.5 per cent. At Calvert, Tex., on Sep- tember 4, Egyptian showed 100 per cent infested, while the American varieties growing alongside showed 91 per cent. Similar results were found atSan Antonio. Though growing in close proximity, the Egyp- tian produced no staple whatever, while the American gave better than an average yield in spite of the depredations of the weevil. At Victoria, in the experimental tract during 1904, three varieties of igyptian cotton (Mit Afifi, Janovitch, and Ashmouni) were tested side by side with American varieties. The Egyptian varieties uniformly failed to make a pound of cotton, while the American varieties aver-_ aged 400 pounds per acre. | In accordance with these observations, it appears that in developing a variety of cotton which shall be less susceptible to weevil attack, by far the most promising field for work lies among the American varie- ties, and of these the very early maturing kinds are most promising. The question of choice of different varieties for food was tested in the laboratory by Dr. A. W. Morrill, by placing squares of two kinds of cotton, American and Egyptian, in alternate rows in a rearing cage SEASONAL HISTORY. 47 so lettered and numbered that each square could be exactly located. Weevils were then placed so that they could take their choice of these squares, and observations from 8 a. m. to 6 p. m. were made upon the location and activity of the weevils. Though this experi- ment was repeated four times no positive evidence was obtained to show that weevils had any choice as to which kind of squares they fed upon. Table XII presents a summary of these results. -TaBLE XII.—Rearing-cage observations upon boll weevil choice of American and Egyptian squares. S American squares. Egyptian squares. DB iS : 2) # ; } . q Period of observation. 86 3 a eime 5 2 a.!| 5 @ i |S Selene: ees Sy e EA ars E i a = ® ep I = ® roa | d ® = a bd ae = | ad ds 5 o > = Ss 3 oF ra S) s| jon e S| Ss sg 8s D on ~ I ® oO 5 S i) = o a0 i) = 5) te) ca Z, i B ties * Without food or water 50 weevils, just developed but not fed, lived an average of 5 days; 15 which were 7 weeks old lived 6 days; and ' 18 which were one month old lived 7.5 days. Taste XIV.—Duration of life of boll weevils with normal food. Num- Aver- | Maxi- : Number ; Season. Sustenance provided. ber of of weevil ache i tet wee- days lon- lon- vils. ; gevity. | gevity. Muby—Sep tember 2. o.6: sc sncsed ce S25 BS OUSHE RB EM erie Uetae erates See | 37 684. 5 18.5 +20 September—~November.......2.-..2-2.-+-.|----- ClO) Srey RR ee eee | 45 981.0 21.8 69 Roralstoniweewvilsmedvonebolls. 2 3) 25.2 oso sh ness on ctw sae 82 1, 665.5 20. 3 69 antany—MUllyon seen er ce ye fle HOA Ge eee a seis 4,261 | 103, 931.1 24.3 130 October-December ...... robbie Soe Se tee bk ee CORE eas ee US oe OS 92 2, 950. 9 SOROS nee motal ton weeviisuedson foliage! )i..c lee Lk be eds 4,353 | 106, 882.0 24.5 130 ISU SS Be beh iene tote nea ee SCE Osea Seoasoosdasouel 170 | 12,439. 4 (eel 105 “Arg ad Uy © SOE e Bese aie oer arenes ane | COE SoUeS ee Peake ae. | 91 3, 363. 2 36.9 58 PMAOUIST—SePlCIMDCL =< 5-2 - sq. 22. -cies-|~s- 2 OKO SS Namie Jane emai | 64 4,796. 0 74.9 135 eptember~October:- = 22) s22is..222-222] 2225. GOR Rie See aaa ee | 18 1,170.0 65.0 +76 Mecrober—Decempbersee...: <8 2 oc -n| eee ke GO Se eee rete eae | 10 359.0 SON OMe eee Mopfalmon.weevilseduoniSquarests.|22 4-5 5228: Yeas ete tee | SH AP eG) 62.7 135 | These records show the following longevity for weevils fed on different portions of the cotton plant: On bolls, 20.3 days; on foliage, 24.5 days; on squares, 62.7 days. The sustaining power of foliage is therefore about 20 per cent higher than that of bolls, and that of squares 150 per cent higher than that of foliage. This indicates that the squares are by far the most suitable form of food. A number of observations were made on the relative longevity of weevils of different generations when fed upon cotton squares. Weevils of the first generation lived 57 days; of the third, 48.5 days, and of the fifth, 65 days. Newly reared weevils evidently have not the vitality of weevils emerged from a long hibernation, for they can not live so long on water alone. The boll weevil can find nourishment in several species of malvaceous plants which will sustain life twice as long as water alone, and in certain conditions as long as.cotton foliage. It is inter- esting to note that the sweetened water from sorghum cane had almost three times the sustaining power of pure water. In connection with these studies figures were obtained upon the relative food value of the various foods to the two sexes. The data obtained may be tabulated as follows. 28873°—S. Doc. 305, 62-24 50 THE MEXICAN COTTON-BOLL WEEVIL. TaBLeE XV.—Duration of life of boll weevils according to sex. | Males. Females. Condition. | Season. phe 8 Se : . . Num- | Weevil | Lon- | Num- |} Weevil | Lon- | ber. days. | gevity.| ber. days. | gevity. Hibernated......-.- Junexs% bos Se None...... 7 13.3 1.9 6 19.2 3.2 FROGIOO! goose ce June-July.......- Ve Eo eee 9 19.8 2.2 9 27.9 3.5 Rigas ee ome Oia see Oatseoeos 7 18.9 > Hy | 8 26.0 3.25 Gao Ses Ms ra Le Joep mee eee be! Ca) n ele meine 5 17.0 3.4 5 17.4 3.4 Hibernated......-- Tne. bee Rice es 8 24 fa. 3.4 6 18.0 3.0 Reared?=. o.<5e5. SOO LE eat Water..... 4 14.8 Sa 8 30.8 3.85 Hibernated........ March-June.. .... Peeao. 2,638 |27,052.5 10.2 1,980 | 19, 895.5 10.0 Kearen so. 5. > July-—September..| Bolls...... 16 315.2 19.7 PAL 319.2 15.2 Hibernated........ March-July...... Foliage....| 1,672 |42,185.7 24.6 | 1,337 | 34,752.1 25.9 1D Ye es es ee | eed fo (ee eee Squares... 90 | 7,207.0 80.0 4,752.0 69.8 FLCATOC 4-228. s July-October.....|...do..... .- 57 | 3,198.0 56. 1 44 | 2,432.0 55.2 NOPADS tet Ake Go ae eee he Nene 4,513 |80, 069.4 | 17.7 | 3, 492 | 64,290.1| 18.4 Table XV in some respects bears out other findings as to the superior hardihood of the female sex. It will be noticed that the female’s superior vitality is shown in all the cases where the food supply is abnormal. Nevertheless, it is noticeable that in the case of weevils fed on squares and bolls the males had the greater longevity. CANNIBALISM.} It is hardly proper to speak of cannibalism as a food habit of the boll weevil, but the facts 5 a may well be recorded here. Under the impulse of extreme hunger weevils have several times showed a slight cannibalistic tendency. Seven beetles were confined in a pill box without food. On the third day six only were alive. Of the seventh only the hardest chitinized parts (head, proboscis, pronotum, legs, and elytra) remained, the softer parts fants been eaten by the survivors. In another box containing 12 adults the leaf supplied for food was insufficient, and on the fourth day eight were dead, four were partly eaten, and others had lost one or more legs each. In another case a few young adults and a number of squares con- taining pupe were placed in a box together with a few fresh squares to serve as food for the adults. When the box was opened after a number of days one adult was found having its elytra eaten througa and most of its abdomen devoured. In spite of this mutilation the victim was still alive and kicking slowly. The squares were still fresh and fit for food, so that this 1s really the clearest case of canni- balism observed. Frequently more than one larva hatches in a square, and when this is the case a struggle between them is almost certain to take place before they become full grown. Many cases have been — observed in which squares contained one living and one or more smaller dead larve, while in a few cases the actual death struggle was observed. 1 From Bulletin 451, Bureau of Entomology, p. 48. SEASONAL HISTORY. 51 SEASONAL PROPORTION OF SEXES. The most careful records of the sexes have been made in connec- tion with the hibernation period. The records are presented here- with in tabular form, grouping the specimens as hibernated weevils, reared weevils taken during the sprmg and summer, and autumn _ weevils which were about to hibernate: TaBLE X VI.—Sex of hibernated boll weevils. Ne Male. Female. Year. Locality. Number. | Per cent.| Number.|} Per cent. | SIS BSS ee i ect Wictoriayilexs) scene 2. San 269 60. 8 174 39.2 TTS Lo ile So Res aa Calvert Mex ae eo 40 59. 7 27 40. 3 EMEP U I Uae Me i poke Cg tek wis Wictoria lex te 2 eee 203 57. 1 153 42.9 "SAUD Seg SIG Na ae le ee Dallas lexee ane oes eee 173 57.7 127 42.3 SES alls ea 8 geri tee, Oran eg VictoriawMexn: v2.5 se s2¢ 84 59. 6 57 40. 4 ro a ee ee Wallasi Mex wes tee sk. 1,668 54.1 1,412 45.9 eee nee SR eb ees 2 bas Calvert, (Mexess ler se Soden: 948 52.9 846 47.1 ROS See cone WAC TORIA UM exe rerie eco 8 1,660 61.3 1,049 38.7 VEOHEN IS SIN oN oe os oy Oe a ah ee ee ce ae ee SUNS we secee ee Biv Nose ees eee SRA INUCUTAVCLALES Seen e Pee lo tee eee eee emo dA DONS ale Ras E 43.2 TaBLE XVII.—Sezx of spring and summer reared boll weevils. Male. Female. Year. Locality. Number. | Per cent. | Number. | Per cent. TIED 9 AT RS ere ane a a Ra WAG LOTTO AW OsKek ae ee meen ete 240 48.0 260 52.0 2 ideead Siete tea leet agi ne Sata (a a Ose ENB AR CA an 140 53. 1 124 46.9 LONG. oo aaa COE a eee ae Dalllaisy Ut ex py.) hs a aa 63 44.7 78 55.3 UNO 2 RSS es eee eae reece’ Owerton)) Dex <4. o55 2 ees 9 47.4 10 52.0; LL Sa cet ene a ea Malina Was ess ee 475 54.7 393 45.3 INCHES Sint cles CDSS SS OBS BSS (ice ae ata ete eo re OAT a eee an SGon|/Raeeeanee \hY Cue QUO LEVER INE 55553 bode HE BESeS Shee OSD ASeoBO ne soars er Aeerore AWA eonc Sacre 48.3 TaBLE XVIII.—Sezx of autumn boll weevils ready to enter hibernation. Male. Female. Year. Number. | Per cent.| Number. | Per cent. LU a Ia a po a sey a ie eB alate ag 557 63.7 317 36.3 OMe eihoee be oR A ee ee COIS eRe ms RINE IL Ae Be RUA sn cs ee 3] 62.0 19 38.0 USUE. ote ce bec cosSo SURG DN OCS EES Oe Be Sat sae ate ope Me Rare 63 57.7 127 42.3 MRE ee eee er Oe Nec eeepc odode date ales 173 68.9 78 Sai ISIE 5 6 Beebe gabe cde re be Bee ae ee IEATEE Oe Fe eect mel na a rae Ca 173 ths tf 127 42.3 GUlt. do doScbesa gS GRRE ED Bo GS BECP e re Hees Sena eatin eimai poesia 19 57.6 14 42.4 3 Ls ge se SuBS age oS GaP Oe Ae ue Sia De nr eae 29 D2eih 26 47.3 UNQE bocca Serbs sacl: se cong ebebe >oc ce eces asec sea pE caqsee ACY ollie naa ae 008 J jas ees RVCIP he GeNenares emer ee otal by ees Yelk Nal a hk 60: Ose eae 40.0 Total and weighted averagefor all seasons............-...--.-.- 7,017 5052 5, 418 42.8 52 THE MEXICAN COTTON-BOLL WEEVIL. From these determinations it appears that males are somewhat more numerous than females, the pales based on our observa- tions being 57.2 males to 42.8 females. It is noticeable also that the males are in preponderance throughout the year. Since the males” are less active in their movements than are the females, the advantage of the existence of the majority of males becomes 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. It has been shown by rearing experiments conducted at low tem- peratures that the retardation of the development, such as is due to cold weather, favors the development of the males. FERTILIZATION. AGE AT BEGINNING OF COPULATION. After the adult weevils have left the squares a certain period of feeding is necessary before they arrive at full sexual maturity. This period varies in length according to the temperature prevaill and appears to bear about the same ratio to the developmental nena as does the pupal stage. With weevils fed upon leaves alone the period prscadias copulation is about twice the normal length, in the cases observed, of those having squares tofeed upon. Mr.Cushman, in observations at Tallulah, La.,in 1910, found that the period from emer- gence of the female to copulation varied from two to seven days, with an average of 4.4 days. During hot weather it is probable that this period averages three or four days, but as the weather becomes coider it increases gradually until the weevils may become adult, feed for a time, and go into hibernation without having mated. It should not be understood, however, that weevils do not usually copulate before hibernation. Mr. C. E. Hood made numerous observations of the exercise of this function in the fall of 1909 at Mansura, La. SEXUAL ATTRACTION AND DURATION OF COPULATION. The distance through which the attraction of the female insect will influence the male varies extremely. In observations made by Dr. Hinds at Victoria, Tex., it was found that the male was unable to recognize the female at a much greater distance than aninch. Obser- vations carried on in the field, as well as in the laboratory, tend to show that the sexes are attracted only when they meet, as they are likely to do either on the stems or upon the squares of the plant. In a considerable number of cases that were timed the average duration of the sexual act was very nearly 30 minutes. The earliest spring records of copulation available are for April 15. DURATION OF FERTILITY. A number of femaies which were known to have mated were isolated to determine the duration of fertility. Although the limit was not determined exactly, the results proved very striking. Several of the females laid over 225 eggs each, and nearly all of them proved fertile. Selecting three cases in which the facts are positively known, it appears that fertility lasted for an average of something over 66 days 7 he o SEASONAL HISTORY. 53 i) and that during this period these females deposited an average of | nearly 200 eggs. The maximum limits may possibly be considerably higher. In fact, a single union seems to insure the fertility of as - many eggs as the average female will lay, and its potency certainly | lasts for a period fully equal to the average duration of life. It 1s- probable, however, that there are many cases of repeated fertilization of females. : PARTHENOGENESIS. Several series of experiments were conducted at Dallas, Tex., in August, 1906, to determine whether the boll weevil can reproduce arthenogenetically. Mr. R. A. Cushman kept 24 unfertilized Beiales in confinement for 259 weevil days, and found that they deposited only 43 eggs, all being placed outside of the squares. No fertile eggs were laid. The rate of oviposition was one egg per female every six days. With a similar purpose Dr. Hinds isolated 40 indi- viduals as soon as they matured.t’ Each beetle was supplied daily with fresh, clean squares and careful watch was kept for eggs. The first point noticed was that no eggs were found till the weevils were about twice as old as females usually are when they deposit their first eggs. After they began to oviposit it was found that a very small pp eportion of the eggs were deposited in the usual manner within sealed cavities in the squares, but nearly all of them had been left on the surface, usually near the opening of an empty egg puncture. This same habit was shown by a number of females, and so can not be ascribed to the possible physical weakness of the individuals tested. The number of eggs deposited was unusually small, and the few placed in sealed cavities failed to hatch. After somewhat more than a month had been passed in isolation a few pairs were mated to see if any change in the manner of oviposition would result. The very next eggs deposited by these fertilized females were placed in the squares and the cavities sealed up in the usual manner, showing that the infertile condition had been the cause of the abnormal manner of oviposition. OVIPOSITION. AGE AT BEGINNING OF OVIPOSITION. As has been shown, normal oviposition never takes place until after fertilization has been accomplished, but it usually begins soon afterwards. Observations upon the age at which the first eggs are deposited can be made more easily and more positively than those upon the age at which fertilization takes place. In a general way, therefore, the observations here given may be cited as also throwing hight upon the time of beginning copulation. Table XIX is intro- duced to summarize the various observations which have been made upon the period preceding oviposition. It will be noticed that the range is from 4 to 14 days during the breeding season. Of course, the weevils which hibernate before ovipositing are not to be consid- ered as of this category. 1 Bulletin 51, Bureau of Entomology, pp. 91, 92. 54 THE MEXICAN COTTON-BOLL WEEVIL, TaBLE XIX.—Age of the boll weevil at beginning of oviposition. Date adult. Place. Date first egg. — June 8-14, 1903........-- Victoria, Tex.....-... June. 16-10-4 he 5. July 8-11, 1910........--- Telinianh) Vanna Jily 14-19 oe ee 6. July 29-31, 1910..-......-]--..- BO see. eae ee AUG. D-T overt nus eae 6. Aug. 14-22, 1910... .....-|----- 00.330 csen eee ANG. 21-28 55 = accu e ee 6. Sept. 4-9, 1902..........- Victoria, Tex: <2. .-2-- Sept.t6-l7 ee 9. Sept. 10-20,1910......--. Tallulah: Ga: 2225 Sept. 18-Oct. 8......-. 12. Ocha. 1008 25 fe Victoria, Tex........- Oct, 1620-7, 2. ee 14. Noy. 9-11, 1002.2. 02. 28) nee- GO ens eae eens Nov. 16-193 ee esse oe 7 its 5| $8SsSRsu June S—Nov. 10 oe eh eee eee eee June 16—Nov. 19......- EXAMINATION OF SQUARES BEFORE OVIPOSITION. In the course of a great many observatious upon oviposition it was found that females almost invariably examine a square carefully before they begin a puncture for egg deposition. This examination is conducted entirely by means of senses located in the antennz and not at all by sight. In fact, the sense of sight appears to be of com- paratively small use to this weevil. In regard to the actual time spent in the work of examination before beginning a puncture, over sixty observations are recorded. ‘These show that the average time is over two minutes. This examination of squares is made by females only when they intend to oviposit. Males have never been observed acting in this way, nor do females generally do so when their only object is to feed. SELECTION OF UNINFESTED SQUARES FOR OVIPOSITION. The sense by which the weevil examines the squares frequently enables it to detect an infested condition when no external sign is visible. Females sometimes refrain from placing eggs in squares, even when they are apparently searching for a place to oviposit and anxious to do so. The acuteness and accuracy of the preliminary examination is well shown by the fact that when aonidee with more squares than they have eggs to deposit they do not often place more than one egg in a square. Where a totally infested condition is reached, as is frequently the case in the field, no choice between in- fested and uninfested squares could be exercised, and then, unless the female happens to be in a condition to refrain from oviposition, she is forced to deposit more than one egg in a square. Table XX illus- trates the distribution of egg and feeding puncture as collated from many records. TABLE XX .—Selection of squares and relation of feeding to oviposition of the boll weevil. Squares with both egg and Squares fed on feeding punc- oaly. Squares with Squares with miare ital 1 egg each. Place and time of | Total” Cap each. tures, observation. athicken ee ye "| nnm.| Percent | a,,_| Per cent jay Per cent | y,,,,_| Per cent eyes of total plea of total | N""") of total Nom of total * | Squares. * | Squares. * | Squares. “ | squares. In laboratory, 1902..... 630 477 75.7 19 3.0 24 3.8 110 17.4 In Held, 1902202. 22.82 151 56 7.0 33 21.8 46 30. 4 16 10.5 BT uela 1008. 2.2. oe 560 317 55. 9 83 14.8 50 8.9 110 19.6 In field, 1905..........- 1,036 531 51.2 415 40. 0 90 8.6 0 0.0 In meld; 1907... 2.22 2,679 413 15. 4 0 0.0 | 1,832 68. 4 434 16.2 TOTAL oe oS “OPC 3) ft ty (1S ee 6601-5 B42 Ae eee 670 ||... 22a Average percentage. ... at eae 10:3 jicsseeee BOS alscore os 13.2 TT ao if et en —— SEASONAL HISTORY. 55 The observations show that 86.7 per cent of all squares attacked received eggs. It may also be seen that 40.9 per cent of all squares | oviposited in received only one egg each. The squares which were _ only fed upon formed but 13.2 per cent of the total number attacked, _ and, as has been shown above, those receiving both egg and feeding _ punctures constituted 40.3 per cent. As the weevil injury overtakes _ the production of squares the proportion of squares containing both ege and feeding punctures increases rapidly. Where several eggs are placed in a square it is rarely the case that more than one larva develops.t. If two or more hatch in a square one is likely to destroy the others when their feeding brings them together. Should eggs be laced in squares which already contain a partly grown larva, those fiching would probably find the quality of the food so poor that they would soon die without having made much growth. Since one egg will insure the destruction of the square and a number of eggs would do no more, it is plain that the possible number of offspring of a single female is increased directly in proportion to the number of her eggs that she places one in a square. Favorable food conditions for the larva are likewise best maintained by the avoidance of feeding upon squares in which eggs have been deposited and also by refraining from : ovipositing in squares which have been much fed upon. — Selection of uninfested squares is, therefore, of the greatest importance in the reproduction of the weevil, since this insures the most favorable con- ditions for the maturity of the largest possible number of offspring. Feeding and oviposition are common in the same boll, but unless the infestation is very heavy it appears that only rarely is more than one egg placed in one lock, though several are often deposited in the same boll. The number deposited depends considerably upon the size of the boll. The smallest, which have just set, receive but one, as do the squares, and these fall and produce the adult weevil at about the same period as in the case of squares. Bolls which are larger when they become infested have often been found to be thickly punc- tured and to contain 6 or 8, and in one case 15, larve. (See Pl. VI, da; Pl. VII, c.) DEPENDENCE OF REPRODUCTION UPON FOOD OBTAINED FROM SQUARES.” During the fall of 1902 a series of experiments, lasting for 12 weeks, was made to determine the length of life of weevils fed solely upon leaves. In one lot, consisting of nine males and eight females, the average length of life of the females was 25 days, while that of the males was 36 days. Though this period far exceeded the normal time usually passed between the emergence of adults and the begin- ning of egg deposition, no eggs were found. Dissection of the females which. lived longest showed that their ovaries were still in latent condition, though the weevils were then 81 days old. Few instances of copulation were observed among weevils fed upon leaves alone, and among nearly 70 weevils which were thus tested no eggs were ever deposited. After a period of three weeks upon leaves, 11 weevils were transferred to squares. Females in this lot began to lay in. four days, and four of them deposited 323 eggs in an average time 1 In one case four normal pup were foundin asingle square. ‘This observation was made at Shreveport, La., by Mr. H. Pinkus. 2 From Bull. 51, Bureau of Entomology, pp. 112, 113. 56 THE MEXICAN COTTON-BOLL WEEVIL. of 20 days. The conclusion seems plain that so long as leaves alon are fed upon, eggs do not develop, while a diet of squares leads to the development of eggs in about four days. It is worthy of note that the interval between the first feeding upon squares and the depo-. sition of the first eggs is almost the same with these weevils taken in middle life as with weevils which have just emerged. An examination of hibernated females taken in the spring of 1903, which had fed for six weeks upon cotton leaves, showed that their ovaries were still latent. Copulation was rarely observed among hibernated weevils until after squares had been given them. In a few days after feeding upon squares, mating and oviposition began. The average period was from three to five days, and, having once begun, oviposition continued regularly. It has been found that food passes the alimentary canal in less than 24 hours. Assimilation therefore must be very rapid. It is evident that while leaves will sustain life certain nutritive elements found only in squares are essential in the production of eggs. These experiments were repeated in 1904 with similar results. Upon dissecting weevils just taken from hibernation, it was found that females contained no developed eggs, but that their ovaries were in an inactive condition, similar to those of females which had fed for months entirely upon leaves during the previous fall. Upon examin- ing females taken from stubble cotton later in the spring, but before squares nad appeared, it was found that they also were in similar condition. This was also true of females kept in the laboratory from the time of emergence from hibernation until squares became abun- dant, with only leaves for food. It seems peculiar that upon a purely leaf diet eggs are not developed, but all observations made indicate that thisis the case. It can not be said definitely whether the females examined had been fertilized, but it is certain that they were not ready to deposit eggs. PLACE OF EGG DEPOSITION. The location of egg punctures, while variable, still shows some selection on the part of the weevil. This may be due partly to the form of the squares and partly also to the size of the weevil, but what- ever the explanation, the fact remains that in a majority of cases the egg puncture is made ona line about halfway between the base and the tip of the square. Whenso placed the egg rests either just inside the base of a petal or among the lowest anthers in the square, accord- ing to the varying thickness of the floral coverings at that point. Punctures are very rarely made below this line, though they are some- times made nearer the tip. Almost invariably the egg puncture is started through the calyx in preference to the more tender portion of the square, where the corolla only would need to be punctured. With bolls no selection of any particular location has been found, but eggs seem to be placed in almost any portion. THE ACT OF OVIPOSITION. While engaged in making egg punctures, the favorite position of the weevil is with its body arallel to the long axis of the square and its head toward the base. The tip of the weevil’s body is thus brought near the apex of a medium-sized square. It may be that the position SEASONAL HISTORY. 57 described is especially favorable for obtaining a firm and even hold and this may have something to do with the regularity with which itis assumed. Having selected her location, the female takes a firm hold upon the sides of the square and completes her puncture while in this position. The dood begins drilling a hole by removing with the mandibles a little flake of the outer epidermis. Then, with ber feet strongly braced by gnawing and pushing with an auger-like motion, she thrusts her beak into the tender portion of the square. At the bottom of the puncture she makes a small cavity by gnawing, at the same time moving about the hole with the beak as a pivot. Withdrawing her beak, she turns about with the center of her body as a pivot. This places the tip of her abdomen directly over the puncture, into which she thrusts fee ovipositor. The ovipositor is protruded to the bot- tom of the cavity in which it appears to be firmly held in position by the two terminal papillz and the enlarged terminal portion. Slight contractions of the abdomen occur while this insertion is being made. In a few moments much stronger contractions may be seen, and often a firmer hold is taken with the hind legs as the ege is passed from the body, and its movement may be seen as it is forced along within the ovipositor and down into the puncture. Only a few seconds are required to complete the deposition after the egg enters the opening to the cavity. Having placed the egg, the ovipositor is withdrawn, and just as the tip of it leaves the cavity a quantity of mucilaginous material, usually mixed with some solid excrement, is forced into the ep oning and smeared around by means of the tip of the abdomen. This seals the ege puncture, and the act of oviposition becomes complete. Sometimes the weevil fails to locate the puncture imme- diately with her ovipositor. In this event she searches excitedly, moving the tip of the abdomen about feeling carefully over the sur- face of the square. In this search, however, she never moves her front feet, apparently using the position of these as a guide to the distance through which she should search. Failing to locate the puncture in this way she again turns around and searches for it with her beak and antennez. When the cavity has been found again the female invariably enlarges it before turning again to insert the ovi- positor. If the search with the antenns does not prove successful, oe female generally makes another puncture in the same manner as at first. The usual habit of the female in puncturing through the calyx enables it to seal the wound more thoroughly because of the healing power possessed by the calyx tissue. Punctures made in the corolla must remain open or are closed only by the slight filling of mucilagi- nous excrement by the weevil. Punctures through the calyx will, in most cases, be healed by the natural outgrowth of the tissue so as completely to fill the wounds in a manner analogous to the healing of wounds in the bark of a tree. The custom of the weevil in sealing up its egg punctures with a mixture of mucous substance and excre- ment is of great advantage and assistance to the plant in the healing process. While undoubtedly applied primarily as a protection to the ege, it serves to keep the punctured tissues from drying and decay, and thus promotes the process of repair. As a result of the growth thus stimulated in the calyx, the wound is healed perfectly in a short 58 THE MEXICAN COTTON-BOLL WEEVIL. time, and a corky outgrowth appears above the general surface plane. This p passa Ante has been termed a ‘‘wart.’’ The healing is com- pleted even before the hatching of the egg takes place, and thus both | egg and larva partake of the benefit of its production. Occasionally — warts develop from feeding punctures which were small, but the exact conditions under which this takes place have not been determined. — Nevertheless, the presence of warts is the most certain external indi- cation of oviposition insquares. In aseries of observations they were found to follow oviposition in 84 per cent of the cases. TIME REQUIRED TO DEPOSIT AN EGG. Careful observations have been made upon the time of egg deposi- tion. As in all other processes of the life history of this insect, the period of egg deposition is influenced by climatic conditions. It was found at Tallulah, La., in the early part of the summer of 1910, that the time required for making the puncture varied from 1 minute and 20 seconds to 8 minutes and 27 seconds, with an average of 3 minutes and 36 seconds. On the other hand, at Victoria, Tex., in October, the average time was 54+ minutes, and the range from 1 to 13 minutes. At Tallulah the period for the deposition of the egg and the sealing of the puncture varied from 2 minutes and 45 seconds to 9 minutes and 30 seconds, with an average of 4 minutes and 41 seconds. At Victoria the period ranged from 3 to 16 minutes and averaged 74 minutes. STIMULATING EFFECT OF ABUNDANCE OF SQUARES UPON EGG DEPOSITION.! Four actively laying females were confined together upon a few squares from September 22 to October 14, 1902. During this period they laid a total of 227 eggs, or an average of 2.37 eggs per weevil per day. For the next 13 days these same weevils were isolated and supplied with an abundance of squares. During this shorter period they laid 236 eggs, or 4.54 eggs per female daily. These figures are the more striking, because the stimulation was plainly shown in spite of the general tendency to lay fewer eggs as the weevils grow older and as the average temperature becomes lower. ACTIVITY OF WEEVILS IN DIFFERENT PARTS OF THE DAY. Two series of observations have been carried on to determine the hourly activity of the weevils. The experiments at Victoria were conducted in the early part of September, when the temperature was ranging from a little under 70° F. to 95° F. durmg the day. It was found that there was almost a perfect coincidence between the temperature curve and the curve of the average activity of the females in ovipositing. This is shown in the accompanying diagram (fig. 5). it also appeared that the activity of the weevils began and ceased at about 75° F. Perhaps this indicates that the act of oviposition requires a zero of effective temperature different from that of develop- ment. This would be entirely analogous to conditions in flowers, where it is found that the various functions of the plant are governed 1 Modified from Bulletin 51, Bureau of Entomology, pp. 87, 88. SEASONAL HISTORY. 59 i by independent laws of effective temperature. It appears also that || the activity is much less on cloudy days than on clear days. At Tallulah, La., in 1910, observations were made on the periodic | division of daily oviposition. The results are shown in Table XXI. anne ae MEV ETE rie FO A HEIT . 12P I2e lam 2 3 4 = wn o> ~] (e2) de) 5 > 2 Mm w iN on © N @ o Ss 3 lil si amet AE sector eee CHa eneicrer emeeeeaearelefee fey foT py yy dpe bel ay | Fic. 5.—Diagram showing average activity of flve female boll weevils. (After Hunter and Hinds.) TABLE XXI.—Summary of periodic division of oviposition, based upon nine boll weevils, Tallulah, La., July, 1910.3 inert cake ; pene Average C otal eggs number o eggs per Period. laid. eggs per oviposition weevil our. period. per hour. 2 10s WOT S Ue 00 Cee ease Sapa ea eam ae 25 5. 00 Dowls 0. 63 © DU TTS I Oi, TO ee eee ee See ae 10 -59 9. 26 07 4! Din TOG St TOS SS oe 21 2.10 19. 44 26 2 2p TAAL Onna Fee eS sie ee ae a 17 2.13 15.74 27 Hep On Deke tas ee eats Coe Sl sae. se 35 4.38 32. 41 55 From these records it may be seen that the warmest part of the day is the most active period for the weevils. _ SEASONAL RATE OF OVIPOSITION. Since the period of reproductive activity of the boll weevil is so long, the rate at which eggs are deposited is a question requiring much time for its determination. The rate of oviposition is at least as strongly influenced by variations in temperature as is the rate of development, and it is very probable that some of the previously unaccountable and abrupt variations in the rate upon succeeding days may be explained by the relative humidity or by the amount of sunshine. The rate is influenced also by the abundance of clean squares which the weevil can find, so that it is greater in the early part of the season as the degree of infestation is approaching its it than after infestation has reached its maximum. Several series of observations have been made upon the rate of egg deposi- tion. These have been tabulated below in Table XXII. 1 From Cushman, Journ. Econ. Ent., vol. 4, p. 436. 60 THE MEXICAN COTTON-BOLL WEEVIL. TaBLE XXII.—Seasonal rate of oviposition of the boll weevil. Aver- | Aver. Num-| age Num- ; Total age Place. Time. ber of Bacher Leip number number females. days. | posi- of eggs. | of eggs tion. y Victoria, Tex........-.... Aug.-Dec., 1902... 31 135] 135] 255] 1.88 LOY Aaa, ey ee SE ae eee ae Sept.-Oct., 1902... 40 247 6 | 1,248 5.05 23 227 2.37 | Do...........--------]---- do......--....- 4 { 13 \ 9 { 936.| 4.54 | DOR be ee Seances ee Oct.-Dec., 1902... . 9 352 39 990 2.81 DOP - tnrgee ede ales May-July, 1903....} 351] 2,018 39| 5,254] 2.60 |B Yo} eee SOA Sele See Pose June-Sept., 1903. _ 324) 1,395 58 | 3,541 2.53 12) ee ore eee OTe ty ne 3 21 7 112] 5.32 Terrelle Tex: “pls ee Sept:, 19046 522-7" | 4 12 3 55 4.56 Dalle vhexs eee -...| July—Aug., 1905... 2 23 11 81 3. 68 IDO! fat as eae eee Aug.-Sept., 1905. .- 3 108 36 233 2.15 allah eiat 2. 22 se June-Aug., 1910... 39 310 34] 1,830 5. 90 a DES each. Seas Mate com bat Se Aug.-Oct., 1910... 34 183 45 887 4.85 LT) Eee A ame | Reet Ie Aaa Bi 154: | BRAD) A Pee At 14,949 }). 2. a eee ato) ec Pe eR ERIS) | Shae BER Ree een ee Seer [ores See BL eee ee 3.13 1 Hibernated weevils. 2 First generation weevils. 3 Observed for entire oviposition period and used in discussion of fecundity. The influence of temperature upon the rate of oviposition may be shown by the following diagram (fig. 6), which expresses in a single line the mean number of eggs laid daily at a NuMBER oF Es6s given temperature. There is, of course, more Agr or less fluctuation from the mean, and it is due mostly to differences in humidity. The maximum number of eggs deposited by any weevil in one day has been recorded by Mr. Cushman as 20 at Tallulah, La. At Vic- toria, Tex., Dr. Morrill recorded two weevils to have laid 108 eggs in three days, or at the rate of 18 eggs per day. Dr. Morrill found that the size of weevils ‘lid not affect the rate per day, as four very small females laid 761 eggs at the rate of 3.3 eggs per day. It will be noticed that this rate is higher than the average of all the records in Table XXII. The number of eggs produced on the first day of oviposition varies from one to seven. About itucmee Ot teapeaiee OF per cent of the weevils at Victoria were on average rate of oviposi- found to oviposit fewer than three eggs on the tion of boll weevil. (Orig- inal.) Ons” first day. TEMPERATURE, DEGREES Fr IS THE FECUNDITY OF THE WEEVIL DECREASING? In view of the fact that recent observations have shown a decrease in the fecundity of the gipsy moth in Massachusetts,’ we have selected from the foregoing table (Table XXII) on the seasonal rate of oviposition the rather meager data bearing on the question of whether the fecundity of the boll weevil is decreasing. We find 76 1 Howard and Fiske, Bull. 91, Bur. Ent., U. 8. Dept. Agr., pp. 109, 110, 1911. SEASONAL HISTORY. 61 weevils at Victoria, Tex., in 1902 and 1903, laying an average of 119 eggs in an average period of 46 days, and at the rate of 2.6 eggs per day, with a maximum of 18 eggs in one day; while at Tallulah, | La., in 1910, 13 weevils laid an average of 209 eggs in an average period of 37 days and at the rate of 5.7 eggs per day, with a maxi- ie mum of 20 eggs in one day. While these facts appear to indicate _ that the fecundity of the weevil is not decreasing, they do not, on the other hand, because of the great difference in the places of _ observations, prove an increase. More detailed data will be obtained on this point in the future. PERIOD OF OVIPOSITION. With the exception of hibernated weevils it appears that ovipo- sition begins with the majority of females in about seven days after they emerge as adults to feed and continues uninterruptedly until shortly before death. In the case of 43 weevils observed at Tallulah, La., in 1910, the average preoviposition period was 7.72 days, the minimum 5, and the maximum 23 days. While females fre- quently deposit their last eggs during the last day of their life, a period of a few days usually intervenes between the cessation of oviposition and death. The known maximum number of eggs laid by a single individual is 304. This was in the case of a weevil which lived for 275 days and deposited eggs at the rate of 7.6 eggs per day for 41 days. The __ Maximum period of oviposition recorded is 135 days. In the case of 52 hibernated weevils at Victoria the period of oviposition averaged about 48 days, the maximum being fully 92 days. In an average rate with 21 females in the first generation the actual period was almost 75 days, the maximum being 113 days. The average period for the females of the first two generations appears to be longer than that for any other. In the third generation the average period for 11 females was 58 days, the maximum being 99 days, and in the fifth generation for 5 females the period averaged 48 days, with the maximum only 62 days. At Tallulah, La., in 1910, the average oviposition period was found to be 34.44 days. The average period for all of the records available is but 31 days. The approach of cold weather cuts short the activity of the weevils which become adult after the middle of August, thereby decreasing the length of their oviposition period. Weevils which pass through the winter usually live HhoarSect but as it requires more or less vitality to pass through the long hibernation period, their activity in the spring is thereby lessened. EFFECTS OF OVIPOSITION UPON SQUARES. As has been explained elsewhere, the attack of the weevil on the square causes it to form an absciss layer, which ultimately causes it to separate entirely from the plant. One of the immediate effects of attack is the flaring of the square, that is, the spreading of the bracts and their subsequent yellowing and drying. (See PL. I.) Flaring may result from many other causes besides boll-weevil injury. When resulting from weevil injury it does not begin, as a rule, immediately after the injury, but only within from one to three days of the time 62 THE MEXICAN COTTON-BOLL WEEVIL. when the square will be ready to fall. In especially severe cases o feeding injury flaring often results in less than 24 hours. Occasionall the growth of the square overcomes the injury from feeding, and the bracts, after having flared, again close up and the square continues its normal development and forms a perfect boll. When injured by the feeding of a young larva as the direct result of successful oviposi- tion, flarmg was found in 193 cases to take place in an average of 7 days from the deposition of the egg. (See Pls. V, VI.) After an average period of 2.5 days subsequent to flaring the square was found to fall to the ground, although it may sometimes hang by a thread of the bark. The average time from egg deposi- tion to the falling of the square in 539 cases from June to September was found to be about 9.6 days, which is about the middle point of the weevil development. It has been shown in another place (Table XXVII) that the period before the falling of the square has a direct bearing upon the period of the development of the weevil. PROBABLE ORIGINAL BREEDING HABIT. There is nothing to indicate that the boll weevil has changed its food plant, although it may have done so. It is now confined, as far as we know, to the various species and varieties of the genus Gossy- pium. The boll weevil belongs to a genus of weevils every species of which is confined in its food habits to a single species or genus of food plants. The majority of the species of Anthonomus and perhaps all that belong to the true genus normally breed in buds. It is therefore reasonable to assume that the normal habit of the boll weevil is to breed in the cotton buds or “squares,” and that its habit of breeding in the bolls is an adaptation due to the necessity of providing for the ereat number of weevils which develop in the later part of the season. A study of the length of the development of many species of Antho- nomus leads the authors to believe that the short developmental eriod in squares is perfectly normal and that the longer period in bolls is due merely to environmental conditions, as is explained under the subject of development. THE EGG. DURATION OF EGG STAGE. Concealed as the eggs are beneath several layers of vegetable tissue, 1t is impossible to examine them to ascertain the exact length of the egg stage without in some degree interfering with the natural- ness of their surroundings. The beginning of the stage is easily obtained by confining female weevils with uninfested squares. By making a large series of observations about the time that the larve should hatch it is possible to obtain the average length of the egg stage. The extreme range which has been observed in the duration of this stage is from 1 to 17 days, while the average period for the whole number of observations is but 3.7 days. It is possible that the embryo can undergo an even greater retardation without losing its vitality. The period of embryonic development is lengthened by decreases in oe temperature and also by lowered atmospheric humidity. Thus it was found that between 79° F. and 81° F. the ee SEASONAL HISTORY. 63 egg stage averaged 1.9 days at Alexandria, La., 2.61 days at Tallulah, La., 3.73 days at Victoria, Tex., and 4.1 days at Dallas, these differ- ences corresponding quite regularly to the differences in the humidity of the various places. Table XXIII is presented to show the data (OLE a IN ONAN np OL Ee 2/ Mer an ae ee a seis Cle a ry Eee a ae p [a 2 | EE CLE ce! aera es] § Fer aed 1 Ge q ct me SN a | SO ER a0 |) N spe SS a |S R ess = Q e , a a < ale reg re re ia ee ian MIL ALP Fie. 7.—Diagram illustrating relationship of temperature to the egg period of the boll weevil at Victoria, Tex., in 1902. (Original. ) which have been obtained on this stage, and is accompanied by two diagrams (figs. 7 and 8) to illustrate the relationship between mean temperature and the length of the egg period. TaBLE XXIII.—Duration of the egg stage of the boll weevil. Total ae num- | Aver- | Mean Place. Year. Eggs laid. Eggs hatched. egos | berof| age |temper- eg. | ese | period. | ature days. Days ida. Wactoria, Nex s).. 22.22... 1902 | Sept. 4-29....... Sept. 7-Oct. 3... 384 | 1,434 3.73 81.0 13/0) 2 Sat ge ieee ee a 1902 | Oct. 7=20-.2..2.: Oct. Marr ee. 95 430 4. 52 73.0 DOM Renee ae eaee TO Zia NON aie se oee . cae aaa: | 2 3 1 24 8 | 12 4 39 13 ee gL 4] — Bigg | a OMLeMber os.) ee sees oe 5 | 2 September 4-5..............- 10 20 2 60 6 | 50 5 130 | 13 oe fp eee eo 30 60 g ab tal oe ; a0 ir Seplember 25. -. 23.2 -t.<:2-2 5 5 40 5 70 } ype Se etd chee cena a te | 16 16 1 | 112 | fi 96 6 | 224 | 14 Doe een ese) eee 4 4 1 | 40 | 10 16 4 56 | 14 1D Yee one Bae ee ee ee 12 24 | 2 | 72 | 6 | 7 6 168 14 September 3-4. .........-.-.- 3 6 | 2 | 21 | 7 15 | 5 42 14 September 2-+4.............-- 18 36 | 2 | 144 8 72 4 258 | 14 Seplem ben eae aoe 9 18 2 81 9 27 | 3 126 14 AUIS USE Stas = eae ee ee | e % ps Poon Coenen Cer be or Bhs < OSes hs ees ee ole eee 5 il mR PM aS Sh We tee we TS ts Beal Ble A oe ee) eg de oe oi DOS Ae eee 3 9 | 3 | 24 8 | 24 3 42 14 September Ve=- seers 2 4 | 2 i4 7 | 12 6 30 15 IAVIC USD Oboe et © 2 ene as. oe ee 4 12 | 3 32 | 8 | 16 | 4 60 15 September is < .... 3 ne see 6 12 | 2 42 | 7 42 7 96 16 ATICUSE OU ns eee eee ee 2 6 | 3 | 16 8 | Ht : _ “ 1D Ya ae ee ee ee eles ede 3 9 va) 24 8 8 WAG (kt Os ae oye Sem ore See ee. | e234: raed cae WAP fee ae 57 19 D Ons oc areas eee odie | Ot) Sato Se | Seen ee | Pe ees ee ts, 427 eaeseaee Saree 60 20 a Nk re a a \ SEASONAL HISTORY. 713 '| Taste XXVIII.—Table showing variations in the developmental period of boll weevils Y in the third generation at Alexandria, La., in 1907—Continued. TOTALS AND AVERAGES. Num- | Total FA ‘. | Total el Total she Total pai Date of oviposition. ber of | egg of larva Tae 1] | Pupa naa weevil Gara stages. | days. | poriod.| 2Y8- | period.| 4#YS: | period.| 4#YS: | period. Meee period... 2... 229 436 IF oa asia car tea Ai lies ene al reas 5 Sea Daa ctl amet exes | ee semen de Marval period.....:-......... Ee) cartel aise Maat 1,096 Ay eee Uk ee IT GL i al Leah ee ae mapal period..........2...-. 2. LSTA Ae tine hecI Me Se tt LS ea 717 DO, remap ae Weebotal period........-.--.--.- 5D 8 RED creel Metree ees tala a ollie peel So] Rear caer ae ote 2 2,198 14.4 | DEVELOPMENT OF WEEVILS IN THE SQUARES WHICH NEVER FALL. It is generally true that squares seriously injured by the weevil sooner or later fall to the ground. The form of the absciss-layer erown when the square is injured determines whether it is to fall or to hang. (See Pl. XV.) This will be explained fully in connec- tion with the discussion of parasites (pp. 148, 144). | Certain climatic and cultural conditions seem to increase the tendency of the cotton plants to retain the infested squares, although this tendency seems to be very largely of a varietal character. In the hanging position the square dries thoroughly and becomes of a dark- brown color. Although exposed to complete drying and the direct rays of the sun, the larvee within are not destroyed by the sun in the same proportion as those which are exposed to the sun on the hot soil. However, control by parasites is much greater in the hanging squares than in the fallen squares—so much greater at times that the total mortality from all causes in hanging squares surpasses that of fallen squares. This matter will be dealt with more fully in a later section. Owing to the much smaller number of squares which hang on the plants, we have been unable to obtain a sufficiently large series of records upon the development of the weevil in this class of squares, but the records available show that the development is slightly shorter in hanging squares than in the average fallen squares. DEVELOPMENT DURING WINTER. As is normal with many species of weevils, there is some develop- ment during the winter months. This development, however, is frequently cut short by severe freezes. In southern Texas larve and pupee of the boll weevil which are in squares when frost comes are not always killed thereby, but slowly finish their development if the weather is warm enough for any activity, and the adults thus devel- oped may live through the winter without feeding. Mr. J. D. Mitchell took a number of live larvee, pupe, and adults from bolls in a field at Victoria, Tex., on December 26, 1903, after two hard frosts and one freeze. Two weeks later, from a field in the same locality, after three hard frosts and two freezes (30° F.), he took another lot of live specimens in these three stages. On February 7, 1904, Mr. Mitchell took 32 adults, 1 pupa, and 4 larve, all alive, from standing stalks, and on February 14 he found 32 adults, 2 pupex, and no larve. The material collected at different times up to February 14 = 74 THE MEXICAN COTTON-BOLL WEEVIL. included 197 specimens, 23 larve, 30 pup, and 144 adults. It therefore evident that large numbers of weevils go into the winter. in the immature stages, and there is every probability that, in the — southern part of Texas at least, many of them live and mature, emerging in the spring. It may be that this gradual maturity of the hibernated weevils is one of the reasons why they emerge so irregu- larly from their winter quarters. Prof. Sanderson, in Bulletin 63 of the Bureau of Entomology, mentions that in March, 1903, Mr. W. P. Allgood sent aim from Devine, Medina County,Tex., a quantity of bolls, which were examined March 12. Twenty per cent of the bolls contained weevils, alive or dead, in some stage. In 40 bolls there were 40 live and 11 dead pup, 30 live and 40 dead adults, and 5 dead larve. Many of the adults had just transformed from pupz. One live larva was found in the material. Estimating the survival of weevils in the plants in this field, Prof. Sanderson calculated that there would be about 10,500 weevils per acre in the spring. The lowest temperature which the weevils experienced in the locality from which these bolls were sent was 23° F. in February. SEASONAL ABUNDANCE. BROODS OR GENERATIONS.! The term ‘‘brood”’ can hardly be applied in its usual sense to the generations of the weevil, as was pointed out by Dr. L. O. Howard in the first circulars of the bureau dealing with the problem. For several reasons no line of distinction can be drawn between the genera- tions in the field at any season of the year, not even between hiber- nated weevils and the adults of the first generation. As has been shown, the period of oviposition among hibernated females is in some cases fully 3 months, while it averages 48 days. The average period of the full life cycle for the first generation is 25 days, and as the time for the second generation would be slightly less, it is evident that the first eggs for the third generation may be deposited at the same time as those for the middle of the second generation, and also with the very last of the eggs deposited by hibernated females for the first generation, as shown in figure 14. The great overlapping of generations thus produced prohibits the application of any of the common methods of ascertaining their baits The complexity indicated for the first three generations becomes still further increased as the season advances, so that in October, for example, a weevil taken in the field might possibly belong to any one of five or six generations. Duration of life and the period of reproductive activity are important factors in determining the average number of genera- tions. Periods of greatest abundance can not be regarded as giving any reliable information upon this point, since the number of weevils developed soon comes to depend largely upon the supply of squares. In the case of the boll weevil, therefore, the information upon the number of generations must be drawn mainly from laboratory sources, but the results are supported by observations made in the field. Many of the hibernated weevils continue to deposit eggs until the middle of July, and some are active for fully a month longer. In 1903 the last eggs from hibernated weevils were deposited on August 27. In the course of rearing experiments made in 1902 it was found that many 1 The following two paragraphs are taken from Bull. 51, Bureau of Entomology, pp. 95, 96. = | developing after the middle of | November may go into hiberna- tion, and from their last deposited eges produce weevils whose last _ offspring will be ready for success- ful hibernation again. This con- clusion is based upon actual dem- onstration. The maximum number of gener- ations will be found by taking the first instead of the last eggs de- posited in each case. In order to ascertain the maximum number of generations which would be pos- sible, the figures for the develop- ment at Victoria, Tex., have been taken. Figure 14 is a diagram _ which shows the maximum num- ber of generations possible and also the minimum number possible. This is based upon the mean tem- eratures of the various months at ictoria and the known period of development at such mean tem- peratures. The maximum number of generations of course begins with the first egg laid by the first weevil to begin oviposition in the spring and continues with the first egg of the first developing weevil from each generation. In this manner it will be seen that 10 generations are possible for weevils reared on squares. The last egg laid by the first emerged weevil and the last eggs laid by the following genera- tions allow only three generations from the first emerged weevils, which might be considered the minimum. The maximum number of generations from the last emerg- ing weevils by the same system can only be eight generations, whereas the minimum number of genera- tions from the last emerged weevils will be two generations. SEASONAL HISTORY. > S ~ ® R Sih qannodeds > x Saree hs s = SW —<& x x Saye PGS alos Sys * Driase New Nw S Agom S§ Ps INN) Ba BES & W Qh xh / & GN eS SN RA SR A/SS8) Sah/ x SWREN/ VIN § io SSN/ Say & S ey Sey Sy se NN b Vxh EM OS _g Re EN SN Sx & SRN oS _s-KN ry > NA IN oN Sy S SQn KIT S | Rae Sal R&xq & QKY § aN oh § SSN Seu TR ia 8 SNe TRON EAS een § | Soy § Sean ols Sistick “hehe SSS \ J wo Sy: SER S ] Sh Sas yy is Nome SNS SEAS aN “ke ey N > vi a: Ws N NB S § § NB SH a QA — ; L & of eS a Tos * 2S ly Ne o 2X SN NAN N NINN -S4h Bae « § xf SOSG Ye | Ny w = S 75 ' weevils which had become adult about the 1st of August would con- tinue to deposit eggs until the latter part of November. the longest-lived weevils and their last-laid eggs, therefore, it is easily possible for two generations to span the entire year. Considering The weevils (Original. ) Fig. 14.—Diagram illustrating seasonal history of the boll weevil at Victoria, Tex. There is no basis for the idea that there is a distinct hibernation brood. The activity of the adults and the development of the imma- ture stages is gradually retarded by the decline in temperature until ~~ "6 THE MEXICAN COTTON-BOLL WEEVIL. hibernation time arrives. Most of the weevils of the first two or three generations have probably died, or then do so, while most of the’ adults of later generations, still having considerable vitality, go into hibernation. It is certain that every generation may have some | direct part in the production of weevils which are to hibernate. All weevils which are still strong and healthy when cold weather comes on may be expected to go into hibernation, so that there can be no special brood for this purpose. POSSIBLE ANNUAL PROGENY OF ONE PAIR OF HIBERNATED WEEVILS. One of the most important factors in the development of an insect is its capacity for very rapid production. The conclusions as to the ability of the boll weevil in this respect are drawn from the following data, summarized from what has been set forth in preceding pages of this bulletin. The starting point is considered to be the average date of deposition of one-half of the eggs for the first generation at Victoria, Tex., which, under the usual conditions, seems to be about June 10. The average number of eggs deposited by a female was found to be 139. For the purpose of this computation 70 is the assumed number. The difference may be considered as an allowance for mortality or failure to hatch. The average period of development for each generation is 19 days. The average period between emer- gence of the adult and deposition of the first eggs is 6 days. The average period for the deposition of one-half the eggs for each genera- tion is 18 days, thus making the average period for each generation 43 days. The sexes are produced in approximately equal numbers. For the sake of conservatism allowance has been made for only four generations in a season. The following table shows the rate of multi- plication and the corresponding dates: Annual progeny of one pair of hibernated weevils. Weevils. First generation, average adult June 29, numbering.............--..----- 70 Second generation, average adult Aug. 10, numbering..............------ 2, 450 Third generation, average adult Sept. 22, numbering. ..........--.------ 85, 750 Fourth generation, average adult Nov. 4, numbering. ...........-------- 3, 001, 250 As a matter of fact, the multiplication during the early part of the season is so much more rapid that it is very certain that a large part of the third generation becomes adult by the middle of August. Pos- sibly a more definite idea of the significance of this ability for repro- duction may be obtained if we consider that, at the conservative rate given, the progeny from one fertile hibernated female might, in the | course of four generations, number one weevil for every square foot of area in a 75-acre field. | As a matter of fact, the possibility of the multiplication is controlled primarily by the abundance of food supply. The maximum infesta- tion is usually reached some time in August. If we assume that there are 6,000 plants on each acre of ground, and that each plant produces 100 squares for weevil attack up to August 1, we would find that if the usual percentage of these squares produces weevils, the actual PLATE VIII. Bul. 114, Bureau of Entomology, U. S. Dept. of Agriculture. Fig. a.—Newly planted cotton fieid, with sprouts from overwintered cotton roots. (Original.) Fig. b.—Fallen infested squares. (Original.) FIELD CONDITIONS IN TERRITORY OCCUPIED BY THE BOLL WEEVIL. SEASONAL HISTORY. Wi _ multiplication would be limited to about 250,000 weevils per acre. _ It has been shown in this bulletin that on the average over 50 per cent of the weevil stages are destroyed by natural conditions. This ' means that the theoretical possibilities are never reached. In fact, ' itis doubtful whether the actual increase from a single pair exceeds ' 2,000,000. |’ Prof. Sanderson, in Bulletin 63, of this bureau, estimated that the actual increase in the number of weevils from the 1st of June to the ist of September is about 50 times and certainly not over 65 times, where theoretically it would be 625 times. PROGRESS OF INFESTATION IN FIELDS. It is of considerable importance to understand the rate of increase of the infestation in the fields. Normally, in a given cotton field the infestation when the squares have just begun to form is under 10 per cent, but this percentage increases very rapidly in proportion as the hibernation was successful. The infestation generally starts in a given field in the vicinity of timber or of buildings where cotton or cottonseed was stored during the winter. It then progresses in | increasing circles until the entire field is scatteringly infested. From _ then on the increase is general until it is almost impossible to find an uninfested square. Table XXIX may be used to illustrate the progress of infestation in a given field. TaBLE XXIX.—Progress of infestation by the boll weevil, field 1, Victoria, Tex.} umber Number Block. Date. Suzie : ie ae Perens Remarks. raat infested. 1903. (iwi Gy © Saoeicte 4,200 675 16.0 | Work of hibernated weevils only. WN cutlivad Sears oes 467 211 45.0 | Second generation at work. AG ul ye22 aie 249 193 77.5 | Third generation beginning. August 4...... 278 224 80.6 August 29...-. 91 85 93.5 | About four generations now working. Milives Ones 358 168 46.6 | Much cotton dying from root rot. Il August s. 255. 331 148 44.7 August 4....-.. 300 100 33.3 August 20....- 699 636 91.1 Rotalees. 6,973 2,440 35.0 1 From Bull. 51, Bureau of Entomology, p. 114. 78 THE MEXICAN COTTON-BOLL WEEVIL. Additional illustrations are furnished in Table XXX. TABLE XX X.—Observations upon infestation by the boll weevil, various localities,1904. | aE: 2 fs |e ee | 2 ig fesals 5g qa |S2 182/88 | Ga |$3 [Suelo 0 > i ae = se |eaiss ee oles Suez ag 22 85 . ® jae |so lee of fas |eeal ae — 3B io] e 2F | Sn (28 xo 12 os62|e8 Locality (Texas). | F3 | 38 5 g [68 |sale° | BE [es .|Eesl 2e ' |sel%2 2 a |Aex cela | 6S [ASelR’ S| a2 =e pee 5 = 228] 35 o 4! = 9 8\o82 of 25 |2> z 2 jade) He (ess) “S |PSe\Fs2) 23 = E = S |Son| Sa lboo| S@ IBselsSal § = = 5 So |Farlor l>azl & \>n2l|>as! > Az A Ay Ee ie Be |< = if deed < oe Fe Swe a 1904. Calyents 22 .o 75252 3.- 12 2 | Ang.23to | 2,754 | 94.0; 251 GA 1,475;).94.7) 1:8 4.2 : Sept 9. | Corsicana: LTS s een Se eS Som es Sppepers 12 5 | July 29 to | 6,951 | 72.4 376.) 5.7} 2,506 | 71.9 6.) “2708 Sept. 12. EAS SS 85s Si fy: ORE 11 5 | July 28 to| 4,534 | 80.4 | 407] 9.0] 3,261 | 64.9 «6 |» 195 Sept. 12. | Mexia =. SLUR Leese 15 5 ky 30 to | 6,445 | 64.4] 317] 5.0] 4,618 164.9] 1.2] 34.5 ept. 13. Palestine a sae ce 22 2 | Aug. 26 to} 3,719 | 91.3 | 274|-~7.4] 2,456 | 92.8 7 8.2 : } Sept. 14. WiIGEORIS semape sae tase 11 18 june 18 to | 13,227 | 54.2 | L7OF 133 544 | 66.9] 6.1 44.6 ept. 24. Wihartonb = $-2 0-2 4 4| July 22 to} 5,005 | 65.0| 167] 3.3 230 | 46.4] 10.2] 25.3 Aug. 25. Motel reese oer ie ee ee June 18 to | 42,635 |...... ttpo eee 14,780.|- 2° 2-22" ee Sept. 24. AV ET ALOR eee |e (jal eee ae ee Eas ae ead OS eee 4G eee 80.0] 2.2 | 2728 1 From Bull. 51, Bureau of Entomology, p. 116. Prof. Sanderson’ has estimated that usually 50 per cent of the squares will be punctured by about two months after the cotton com- mences to square, at which time there would normally be about 100 squares to the stalk. When one-half of the squares are punctured it may be readily concluded that there are probably sufficient weevils present to prevent any more squares from forming fruit. It will be seen, therefore, that the critical period in the relation between natural increase of squares on the plant and increased injury by the boll weevil is during the period of six to eight weeks after the first squar- ing, which usually coimcides more or less closely with the time between the appearance of the second and third broods of the weevils. Thus, if we consider six weeks as the average time for cotton to begin to square after planting, it will be seen that the bulk of the fruit must be set in 85 or 95 days after planting. In other words, to escape injury by the boll weevil, cotton must ‘be so erown that the bolls will commence to open in about 100 days after planting and that all the fruit which will probably be secured must be set within 45 days after the squares begin to form. The advantage of early planted cotton and rapid-maturing varieties becomes, therefore, very apparent. Field examinations have shown that the period of maximum infes- tation is reached between August 1 and 20, and that from 6,000 to 10,000 adult weevils per acre is sufficient to cause maximum infesta- tion within afew days. The highest number of weevils per acre which -has ever actually been recorded from a locality during the summer was 1 Bull. 63, Bureau of Entomology, p. 38. SEASONAL HISTORY. 719 24,347 adult weevils at Port Gibson, Miss., in August, 1911.1. With this number of weevils there was a record of only 37.03 per cent infes- } tation of the remaining squares and bolls. Higher percentages of | infestation have been recorded with much smaller numbers of adult | weevils per acre. | EFFECT OF MAXIMUM INFESTATION UPOM WEEVIL MULTIPLICATION. At the time of maximum infestation the majority of the third- | generation weevils are becoming adult and many of the hibernated weevils have died. About this time also a decrease in square pro- eal Ae Vale Bio ty nil i ee), \ CSET AB Ra OC ny EPH “2 CT) Ee SOY Te eC Oras Ems Fic. 15.—Status of the boll weevil in Texas in August, 1906; percentage of infestation of all forms. (Original. ) duction accompanies the maturity of the bulk of the crop, owing to the fact that the assimilative power of the plant is largely consumed in maturing seed. If dry weather occurs at this period, which is frequently the case in Texas, there is a further decrease in the number of weevils present. Not only are there fewer squares to become infested, but each square is also subjected to greater injury, and many which would otherwise produce weevils are unfitted as food for the larvee by the decay which follows the numerous punctures. Several egos may be deposited in each square, but as a rule only one weevil 1 During the late fall the number may be much larger. See p. 76. 80 THE MEXICAN COTTON-BOLL WEEVIL. will develop. These general conditions frequently bring about . reduction of the number of weevils present in the field. This becom evident to the planter by the number of blooms seen. Of course, thei}; peas soon change and the weevils become more abundant than}: efore. 7 STATUS EXAMINATIONS. In order to become fully acquainted with the conditions of the weevil during the most important parts of the season, it has been the custom). to conduct an extensive series of observations in the latter part of) Fig. 16.—Status of the boll weevil in Texas in August, 1908; percentage of infestation of all forms. | ( riginal.) June and first part of July and again in the first half of August in | order to learn the extent of damage being done by the weevil. These © examinations have been made so thoroughly and have been distrib- uted in such a manner that it has been possible, even in June, to determine the probable direction of the greatest movement of the weevil during the season, to point out the regions in which the damage to | the crop will be greatest, and also to indicate where the control of the © weevil during the winter has been of greatest consequence. The — first “status” of the year frequently gives very definite evidence of | natural control or an absence of it. While certain general methods of a’ SEASONAL HISTORY. Sl control have been contrived, it is still true that some of the most ‘important methods of control are those which are devised to suit particular emergencies. These have been indicated from time to ‘time in connection with the status reports. RELATION OF WEEVILS TO TOP CROP. After considerable cotton has been matured fall rains often stimu- late the production of a large number of squares, and many planters are misled by the hope of gathering a large top crop from this growth. Fig. 17.—Status of the boll weevil in Texas in August, 1909; percentage of infestation of all forms. (Original. ) The joints of the plant are short, and the squares are formed rapidly and near together. Though weevils may have been exceedingly numerous in the fields, their numbers will have become so decreased by the dispersion and by the limited quantity of food that they can rarely keep up with the production of squares at this period of rapid erowth. Many blooms may appear, and the hope of a large top crop increases. It has been a very rare occurrence that planters have gathered top crops, even in years of no injury from insects. The chance of its development, though always small, becomes prac- tically inconsiderable wherever the weevil is present in numbets. 28873°—S. Doc. 305, 62-26 82 THE MEXICAN COTTON-BOLL WEEVIL. In the seniorauthor’s experience of 10 years only oneexample of a top — crop in a weevil district has been seen. ‘This happened in the vicinity of Brownsville, Tex., in 1911. The production of a few bolls on the © tops of the plants was due to a rare combination of exceptional influ- — ences, including very dry weather during the summer, defoliation at an early date by the cotton worm, and late rains after the weevils were greatly reduced in numbers. Neither the very remote chance of gathering a top crop nor the actual injury which is being done to the crop of the succeeding year by allowing that growth to continue until frost kils it is generally | Tig. 18.—Status of the boll weevil in Texas in August, 1910; percentage of infestation of all forms. (Original. ) appreciated by planters. Because of the apparent abundance of squares and the presence of many blooms the plants are allowed to stand long after they might have been destroyed to the great benefit of the next crop. As is the case in the early spring, however, the abundance of squares increases greatly the production of weevils, and though a few bolls may set, they are almost certain to become infested before they reach maturity. Every condition, therefore, contributes to the production of an immense number of weevils very | late in the season and at just the right time for successful hibernation. | As a result, far greater injury is done to the crop of the following | SEASONAL HISTORY. 83 season with no actual gain in the yield of the current season. Plants standing until frosts kill them are often allowed to remain throughout the remainder of the winter and easily furnish an abundance of favor- |able hibernating places for the weevils. The consequence of this practice is that so many weevils are carried through the winter alive that the yield of the next year is much less than it might have been but for the farmer’s indulgence of the forlorn hope of a. top crop. It is far wiser to abandon the uncertain prospects of a top crop and destroy the stalks in order to insure a better crop the following year. ple a oles ciel Str Fic. 19.—Status of the boll weevil in Texas in August, 1911; percentage of infestation of all forms. Original.) VARIATIONS IN ABUNDANCE OF THE WEEVIL FROM YEAR TO YEAR. The decrease in damage by the weevil in Texas in the last few years has led some observers to believe that the insect will finally disappear altogether. Investigation shows that this belief is erroneous. In 1897 the French entomologist, Dr. Paul Marchal, published a paper which set forth some of the essential factors governing insect abun- dance from year to year. This author called attention to the more or less regular periodicity in the abundance of certain well-known injurious insects. In this country the cotton leaf worm, Alabama argillacea Hiibner, is an example of such periodical abundance. The 84 THE MEXICAN COTTON-BOLL WEEVIL. a lication of Dr. Marchal’s law to the abundance of the boli weevil | be discussed in the following paragraphs. mnie the boll weevil antobodl the United States, it was released from most of its natural enemies and was in the portion of the cotton belt most resembling its natural home. Naturally, it increased with great rapidity. In fact, the weevil was on what may be called the upward curve of numerical abundance from 1892 to 1896. In the meanwhile, native parasites began to adapt themselves to it, and we may assume that their abundance might be indicated by a curve par- allel to but behind that of the boll weevil. In 1896 a severe drought — was the cause of a very sudden decrease in the numbers of the weevil and of course also acted upon the parasites. Following 1896 the increase in abundance of the weevil was comparatively slow, owing to the unlimited opportunities for spread. The maximum point in this increase appears to have been reached in the autumn of 1904 and may have been partly due to the fact that in that year the abundance of the parasites was on the decrease. In the winter of 1904 a severe cold period turned the curve of abundance downward, but the decrease was slow until the fall of 1907, when another severe freeze caused a sudden falling off. Floods in the spring of 1908, drought in thesummer, afreeze in the fall of the same year, and droughtsinthesum- mers of 1909, 1910, and 1911, followed in 1909 and 1910 by severe winters, all combined to reduce the weevilstill more. Fic. 20.—Curves of numerical strength of the boll weevil and its para- sites. The boll weevil curve is at the scale of 2 to 10 and represents On the other hand the percentage of infestation in August in Texas. The porastis eurye from 1904 to 1908 is at the scale of 1 to 1 and represents the percentage of mortality o the boll weevil due to parasitism. (Original.) the influence of the parasites was in- creasing and from then until 1911 decreasing. As Dr. Marchal pointed out, it is very rare that some condition does not intervene just before the number present has reached zero and save the species from extermination. The weevil will undoubtedly frequently be greatly reduced in large regions, but in such areas the inflow from other tp ealiies will serve to bring about early reestablishment. (See fig. 20.) “Undoubtedly the adverse seasons of recent years will be followed by others which will allow the-weevil to reach approximately its former abundance. This alternation of years of scarcity and of abundance will continue indefinitely. Natur ally, no definite predic- tion can be made as to the number of years which will be included in the alternating periods. The series of Texas maps presented herewith (figs. 15-19) illus- trates the variations in the percentage of infestation in August during a series of years in which the weevil abundance was at a low ebb. They also show very plainly how the areas of heavy damage are shifted by more or less local causes. Sees: NATURAL DISSEMINATION. 85 , aS _ The status examinations upon which these maps were based show the following average percentages of infestation in Texas. (See Table XXXII.) Taste XXXI.—Percentage of infestation by the boll weevil in Texas in August; years 1906 to 1911. To Percentage of Year infestation, 1906 50. 11 1907 38. 09 1908 SPA eye 1909 14.78 1910 20. 79 1911 Uh 1172 NATURAL DISSEMINATION. The natural movements of the boll weevil are of several more or less distinct kinds. For several months in the spring there is a general dispersal in search of food. After the cotton commences to square there is a steady spread across the fields from the vicinity of the places where the insects have hibernated. This may become a spread from field to field. In late summer there is a sudden and wide dispersal, which is shortly followed by asearch for hibernation. SPRING SEARCH FOR COTTON. After a quiescent period of from five to eight months the weevils leave their hibernation quarters and start in search for food. During a warm period, such as was experienced in March, 1907, many weevils come out of hibernation long before any cotton has made its appear- ance. Without doubt these weevils wander considerable distances and finally either die or reenter the quiescent state on account of lower temperatures. As the emergence from hibernation covers a period of about three months there is little or no regulation of the direction of flight, such as might occur if all emerged at the same time during a high wind. Elaborate tests have been made by releasing marked weevils fresh from hibernation in the vicinity of cotton fields. Invariably after careful search a very small percentage of these wee- vils have been found in the nearest cotton. The experiments of Mr. A. C. Morgan in 1906 at Victoria, Tex., give the most specific data on individual flight. Seven hundred and eleven weevils were used in the experiments, of which 355 had been fed and 356 were unfed. Of the fed weevils 179 were male and 176 female, while of the unfed weevils 183 were male and 173 female. This gave a total of 362 male and 349 female weevils. The maxi- mum flight by a fed male was 775 yards, by a fed female 350 yards, by an unfed male 225 yards, and by an unfed female 500 yards. The experiments also showed the average distance Ny 24 hours for a fed weevil as 63.3 yards, and for an unfed weevil, 66.6 yards. It was generally observed that the weevils flew with the prevailing wind. Bi Observations on the early spring movement of the weevil in Mis- sissippi in 1910 showed the utility of the rotation of crops. During 86 THE MEXICAN COTTON-BOLL WEEVIL. the two status examinations made in 1910 in southern Mississippi it was very evident that in these fields in which cotton followed corn there was a conspicuous absence of infestation until the fall dis- ets of 1910, whereas in neighboring fields in which cotton fol- ee cotton the infestation was in some cases extremely high, even in June. These circumstances and many others which have been observed in the spring indicate a rather irregular dispersal from the places of hibernation which may carry the weevils considerable distances in all directions. On the extreme border of the infested territory this may result in the infestation of entirely new territory. SPRING SPREAD WITHIN THE FIELD. The spread from plant to plant begins in the portions of the field adjacent to Pere hibernation quarters. It has usually been found that the early summer infestation begins at a point adjacent to timber or near farm buildings where seed or seed cotton has been stored. From these centers it is generally easy to trace the infesta- tion to other parts of the field. The movement of the weevils from these centers, however, is not regular. They occasionally fly to rather distant portions of the field and then start new centers, but on the whole the progress is steady and soon brings about a complete infestation of the field. A number of observations were made to determine the degree of movement of hibernated weevils in a field at Victoria, Tex., in 1904. The weevils were marked so that they could be recognized, and frequent examinations were made to determine the location of each specimen from day to day.: It was found that the maximum time one weevil remained upon a single plant was 18 or more days, the observations having been discontinued after the eighteenth day. The average time positively found in 73 cases was 4 days, with a possibility for this same number of observations of 63 days. Prob- ably a true average lies approximately between these results, and, if so, we may assume that about 54 days usually intervene between the movements of each weevil. In the whole series of observations, extending over 25 days, for weevils which were found after being liberated, only 57 movements were recorded. The total of these movements averaged only 62 feet each in 177 movement days. This would give us an average movement of but 0.35 foot per day for each weevil in a field where stubble plants were quite abundant, where squares were forming upon fully one-third of the plants, and during a period for which the mean average temperature was 78.6° F. SUMMER FLIGHTS. During the summer there is more or less general movement within the cotton fields and also from field to field. These flights are at first weak, but gradually become more pronounced and finally lead into the great dispersal of the late summer and fall. During the summer the conditions on the border of the infested area are peculiar. Many of the weevils which arrived late in the fall of the preceding year are unable to survive the winter on account of 1 The remainder of this paragraph is from Bulletin 51, Bureau of Entomology, p. 112. 4 4 4 ‘a NATURAL DISSEMINATION, 87 their exhausted condition. Therefore, the line of continuous infesta- tion may be considerably behind the line of continuous infestation resulting from the last movement of the preceding year. Outside of this continuous line is a strip of considerable width in which the weevil is found scatteringly. The summer flights cause these isolated infestations to coalesce. FALL DISPERSION. All movement of the weevil at other seasons is insignificant in comparison with the great dispersion of the fall which carries the insect far into new territory. It is this movement which causes the more or less regular annual advance in the cotton belt. In one sense this dispersion is merely an overflow from territory in which the insects have become so numerous that there remain no oppor- tunities for breeding. In another sense it appears to be the result of a strong instinct which the weevils possess to invade new regions. At any rate, they show great activity in the late summer and fall. The main causes of the fall flight, therefore, appear to be (1) a scarcity of food and breeding places due to maximum infestation, and (2) an instinct to invade new territory. Several conditions may tend to precipitate the movement or strengthen it. Among these are damage by other cotton insects, which hastens maximum infestation, and drought, which may have the same effect by pre- venting the continued fruiting of the plants. There seems to be no special tendency to fly in any particular direction, although prevailing winds frequently cause the majority of the insects to follow one course. This has been observed to be southeast, north, and east in different localities. If not governed by the wind, any weevil which takes flight is as likely to fly toward the old infested territory as in any other direction. It is, therefore, only a portion of the dispersing weevils which enlarges the infested territory. The distance any weevil will fly in this movement depends upon how soon it finds uninfested cotton. If on the first flight it finds only heavily infested cotton or none at all it will take wing again. In this way a succession of flights may carry the insect over a wide territory. In one case a distance of over 40 miles has been known to be cov- ered in this manner. If, on the other hand, the first flight carries the weevil into an uninfested field it remains there. Consequently, the advance is slowest in regions where cotton fields are numerous. The occurrence of the leaf worm, Alabama argillacea, in great numbers in any locality destroys the food and tends to cause decidedly longer flights of the dispersing weevils. So far as we have been able to discover, the weevil has no sense by which it can locate cotton. Such a sense may exist, but the general aimless flight of thousands upon thousands of individuals seems sufficient to account for the infestation of all fields in new territory. An interesting observation was made by the junior author and Mr. G. N. Wolcott near Meridian, Miss., that the early dispersing weevils, in flying through hill country with heavy woods, found only the patches on the tops of the hills and from these gradually spread downward to the denser cotton. x COTTON-BOLL WEEVIL. MEXICAN THE 88 \ a ao _ “W6/ AO NOSIS FHL SO OND DHL A ORBLE IAN! Ath aa DL Dh AO LIT FL SILOM ty Re c Lm ~ Rs pe, Yel | | NATURAL DISSEMINATION. 89 - Louisiana about August 1, and a little later toward the north, but in all cases the movement had crossed the line by the 20th of August. In this year there were two very well-defined dispersals with about a month intervening. This might indicate that the first dispersal was caused by the lack of food and that in another month a new generation found itself confronted by the same conditions as its predecessor and was also forced to disperse. In 1906 the movement seems to have been more irregular, for the first serious new infestation was in central Louisiana rather than in the southern part of the State. In the hght of present knowledge this was probably due to the smaller amount of cotton grown in the pine woods of southern Louisiana, which naturally gave rise to comparatively few weevils for the flight. The year 1906 was the last in which any appreciable movement into western Texas was observed until 1910. In 1907 and 1908 the eastward and northeastward progress of the weevil carried it far into regions where much cotton is produced. The year 1909 exhibited some very striking features. There had been a considerable loss in the infestation during the winter of 1908 in northern Louisiana and eastern Arkansas, a region of very exten- sive cultivation of cotton. During the autumn of 1909 the almost continuous movement in southern Mississippi from field to field in the rather sparsely cultivated areas amounted to 120 miles for the season. In the delta region of Louisiana, Mississippi, and Arkansas, where the weevils encountered a belt of extensive cotton culture from which they had been driven back during the previous winter and were stopped by the large amount of food available, they were unable to gain more than 20 miles of new territory. In 1910 a peculiar situation developed. It was discovered that high winds had caused an extensive movement into central Mississippi in May or June. In the entire history of the weevil there had pre- viously been known but one occasion when a severe storm caused a dispersal of the insect. A study of the records of the Weather Bureau brings out the fact that there was a series of cyclonic storms about May 7, 1910, passing northeastward across Mississippi from the heavily infested regions around Natchez. We have been unable to find any other explanation of such an extensive movement in the early spring. Studies conducted during the summer and fall of 1910 revealed the existence of many sporadic infestations throughout central Mississippi, probably due to the storm. From these isolated infestations the weevils spread in concentric circles until about the end of November, when the intervening territory became covered. The winter of 1909-10 was unfavorable to the weevil in the Delta. When the dispersion season opened it was noticed that in strong contrast to the rapid movements in central Mississippi, the weevils in the Delta advanced slowly. During the entire season there were only two courses of considerable movement in the Delta region. One of these was along the Mississippi River through the fields adjoining the levees. The other extensive movement in the Delta country G() THE MEXICAN COTTON-BOLL WEEVIL. oe ® . i ¢ was in a belt coincident with a strip known locally as the ‘dogwood ridge.” The winter of 1910-11 also was unfavorable to the weevil. It began _ with a sudden freeze on October 29, which extended over almost the — entire infested region and destroyed the food supply. Severe cold weather in January also contributed to the sr Examinations made in June and August, 1911, demonstrated that the weevil was in the lowest average condition numerically that it had ever reached. It was completely exterminated in the northern portion of the Texas and Oklahoma black prairie, but west of this was a region which escaped the first frost, and where the weevils occurred in more or less normal numbers. The defoliation by the leaf worm was so widespread that a condition of maximum infestation was reached with much smaller numbers of weevils than usual, and the scarcity of proper food supply forced a phenomenal advance along the Mississippi canes conan Tennessee. In Texas and Oklahoma there were some gains made in the lost territory, but even with these gains 24,000 square miles of territory were not reinfested. The northern lmit of cotton production in western Arkansas was reached, and the line of infestation stopped only about 10 miles short of the southwestern corner of Tennessee. Great gains were made in northern Mississippi, and western Alabama and Florida became invaded for the first time. HIBERNATION FLIGHT. The fall dispersion movement continues more or less regularly until frosts occur and mark the beginning of the hibernation period. Thus, in many cases the fall dispersion is a flight into winter quarters. However, a period of feeding seems to be necessary for successful hibernation. Therefore, few of the dispersing weevils which are forced into hibernation by cold weather survive. Those that do survive seem to be supplied from a distinct movement into hibernation quarters at the end of the season. The most striking observation on this pon was made by Mr. J. D. Mitchell in the winter of 1906. Although there had been no lowering of the temperature, he found on entering the cotton fields on November 18 a very restless activit among the weevils. Adults were observed upon the squares wit their wings open and flew at the least disturbance. He observed many hundreds of weevils rising into the air and disappearing. The weather was warm and pleasant, and there appeared no reason at the time for this flight, which continued for about two days. In a few days the temperature became decidedly lower, and Mr. Mitchell was able to find only a very few weevils remaining in the fields. This note is of special interest in connection with the observations on cli- matie control, which will be discussed later. OTHER FORMS OF NATURAL SPREAD. _ Heavy windstorms, hurricanes, and cyclones are powerful agents in the spread of the weevil. It is believed that the great storm of st, saga es 8, 1900, in Texas, carried the infestation northward many mules. As has been stated, the storms of about May 7, 1910, in Missis- Sippl, were instrumental in causing a considerable increase of the infested territory in that State. qi i ' ARTIFICIAL DISSEMINATION. 91 There is another method of natural spread of some local importance. — In hill lands, especially, rains sweep immense numbers of infested squares to the lower parts of the fields. Cotton squares are remark- ably impervious to water, and weevils may develop in them after decay is far advanced. These squares may be carried many miles from their source and deposited under favorable conditions for the emergence of the weevils. ARTIFICIAL DISSEMINATION. While the natural dispersion of the boll weevil is by far the most important means by which new territory becomes invaded, there are certain artificial means of dissemination which are of some importance. The more noteworthy of these are connected with the handling of the cottonseed and cottonseed products. Many weevils are carried to the gins with the cotton. From the gins dissemination may take place in several ways. The weevils may be carried back to the farms in cottonseed to be used for planting, or they may be shipped by rail to the oil mills along with the seed. Moreover, weevils are likely to secrete themselves during cool weather in the wrapping of cotton bales. In this manner transportation along with the lint is possible, although experience has shown that the danger from this source is inconsid- erable. When the cottonseed arrives at the oil mill there is chance of infestation from flight mto neighboring cotton fields. The greater damage, however, is in the shipment of weevils beyond the oil mills in the cars which have been used for the purpose of carrying the seed to those establishments. Among the means of minor importance may be mentioned the inci- dental carriage by vehicles, including railroad coaches, by the move- ment of plantation laborers, and by intentional carriage for the purpose of experimentation or exhibition. The possibility of spread by these various means will be discussed in the following paragraphs: MOVEMENT OF SEED COTTON. Many immature or teneral weevils are carried to the gins with the seed cotton. Adults are frequently found crawling over the wagons filled with unginned cotton. The devices for removing foreign matter from cotton in the process of ginning are numerous and effective. Many of the weevils are removed or destroyed, but adults, as well as larve and pupe, are likely to pass through the gin with the seed. This has been determined by the Bureau of Entomology by running gins experimentally... Many of the weevils, consequently, are carried into the seedhouse along with the cottonseed. Moreover, many of those that are removed by the cleaning devices are not injured. They pass along with the motes into a barrel or box, which is generally uncovered, and from there they frequently fly about and find their way into the cottonseed, or they may secrete themselves in the bagging of the bales standing in the gin yard. Furthermore, many ot the adult weevils are not taken into the gin house at all. Being on the cotton in the wagon, they are disturbed by the process of unload- ing and may fly to any portion of the plant. Consequently, cotton- seed in storage at the gin may become infested by any one of the 1 For a full account of these experiments see Farmers’ Bulletin 209. 92 THE MEXICAN COTTON-BOLL WEEVIL. following means: (1) By passage of weevils through the gins alo with the seed; (2) by the weevils finding their way into the see house from the receptacle containing the discharge from the cleaner feeder; and (3) by flight from the wagons during the process of unloading. Thus, gins may serve as important agencies in the dis- semination of the boll weevil by the shipment of the seed or possibly of baled cotton. That the danger in baled cotton is slight is shown by the fact that no colonies have been found to have become estab- lished in spite of extensive shipments out of the infested territory which have been made for several years. In many localities the unginned cotton is carried for a distance of 20 miles or more to the gins. It frequently happens that this car- riage is into uninfested territory. Under such conditions it is evident that an important form of artificial dissemination of the weevil occurs. Two examples will be given of the possibility of the dissem- ination of the weevil by such means. In October, 1904, a shipload of unginned cotton was carried across Lake Calcasieu, La., from Grand Lake and Lakeside to Cameron. The latter place was free of the weevil and isolated by extensive stretches of swamp lands. Shortly after the shipment reached Cameron, however, an infestation was found in the gin yard. It was in all probability due to the carriage of the cotton from the opposite side of the lake. In the other case a shipment of unginned cotton was made from Yucatan, Mexico, to ay aR Ala., in 1909. The Mexican locality was infested by the boll weevil, while the region about Mobile was free of the insect. No infestation resulted in this case for the reason that the shipment from Mexico was accidentally delayed in transit and did not reach Mobile until all of the weevils had died. If the shipment had been made according to the regular schedule there is little doubt that an infesta- tion in the vicinity of Mobile would have resulted. MOVEMENT OF COTTONSEED. In ginning districts on the edge of the infested territory the custo- mers are composed of those whose fields are infested and those whose fields are not infested. The inevitable result is that weevils are constantly brought into the gin yards by the farmers, and in the subse- quent movements of the cotton are spread broadcast. Some of them may alight upon the wagons filled with the seed to be returned to the farm and consequently may be frequently carried to uninfested farms. The most striking illustration of infestation by this means was found in Shelby County, Tex., in 1904. An establishment on the border line ginned for farmers in a radius of 10 miles or more. Some of the customers had the weevil. The ginner himself had a few weevils on his place, but had raised an exceptionally large crop of big-boll cotton, for the seed of which quite a demand arose. An investigation of the farms in this district showed that all the custo- mers who had purchased this seed had infestations near their seed house. Very few of the other farms in the vicinity were found to be infested. Cottonseed is frequently shipped considerable distances from the gins to the oil mills. As has been shown there are abundant chances that the seed may become infested at a gin within the infested terri- tory. (See Plate IX.) At the oil mills the cars are unloaded and Bul. 114, Bureau of Entomology, U. S. Dept. of Agriculture. RELATION OF BOLL-WEEVIL CELLS TO SEED. a, Boll-weevil pupa found in cotton seed; b, boll-weevil pupa in cell of lint from boll; ec, weevil cell in dwarfed cotton boll containing live pupa taken among seed; d, weevil cells in bolls: e, cotton seeds. (Original.) cv ARTIFICIAL DISSEMINATION. 93 _ passed on to the railroads for other uses, frequently without being _ swept out at the mills. It is common in the lumber country for cars _ to pass from oil mills to lumber mills. Such cars are often found - eontaining several pounds of seed in the corners. The lumber men _ sweep out this waste before loading their cars. In case cotton grows near the mill the danger is quite apparent. An interesting example of the shipment of the weevil in cotton- seed came to notice in Mexico a few years ago.!. On January 5, 1903, it was discovered that Texas-grown cottonseed was being imported into the southeastern part of the Laguna district in Mexico.2, Exami- nation of this seed, made by Prof, L. de la Barreda, revealed the fact that six lots had been received from infested points in Texas and that each of these lots was at that time infested with live boll weevils. The results of an examination of samples from three consignments are given in Table XXXII. TABLE XXXII.—Result of examination of infested cottonseed shipped to Mexico. Number Boll of sacks of | weevils Alive. Dead. examined. OU: 8 27 2 25 4 11 2 9 The results of these careful examinations show very clearly the possibility of transporting live weevils in shipments of cottonseed. Unless the oil mill is within the infested territory and ships hulls to points outside there can be very little danger from this product. In fact, it is hardly possible that weevils are ever spread by means of cottonseed hulls. BALED COTTON. One of the writers has found live weevils in bagging about bales consigned to Liverpool on the wharves at New Orleans. However, as has been pointed out, experience has shown that the danger from this source is very slight. PASSING VEHICLES. Carriages, wagons, and railroad trains, in passing fields where the weevils are numerous, may carry them great distances, although few specific observations have been made on this matter. MOVEMENT OF FARM HANDS. Many laborers frequently pass from infested territory to uninfested territory. Their practice is to use cottonseed for ee ing breakable household articles. If the movement takes place late in the season 1 The remainder of this and the next paragraph are from Bull. 51, p. 125. 2 Boletin de la Comision de la Parasitologia Agricola, vol. 2, pt. 2, pp. 45-58. 94 THE MEXICAN COTTON-BOLL WEEVIL. this cottonseed or sacks used in infested fields may easily be the means of spreading the insect. It is thought probable that a sporadic infestation at Jackson, Miss., in 1908, originated by such means from the heavily infested district around Fayette, Miss. UNEXPLAINED SPORADIC OCCURRENCES. Infestations at Wichita Falls and Paris, Tex., in 1904, far removed from other infestations, can not be explained. A reported infesta- tion in 1909 at Temple, Okla., is also of the same nature. INTENTIONAL TRANSPORTATION OF THE WEEVIL. On several occasions it has been found that the boll weevil has been carried into uninfested territory purposely. In some cases the inten- tion has been merely to exhibit live spécimens and in others to test supposed remedies. Whatever the purpose of these introductions may be, the practice must be strongly condemned. It is very likely to result in the infestation of localities many years in advance of the time the weevil would reach them by natural means. The result would be a great and unnecessary loss, not only to cotton planters, but to merchants and others dependent upon the cotton trade. In this connection attention is directed to the fact that a Federal statute pro- hibits the interstate shipment of the boll weevil, as well as other important insect pests, and prescribes heavy penalties... This act is reprinted in part, under the heading ‘‘Legal Restrictions,” on a sub- sequent page. In addition to the Federal legislation on this subject practically all of the States in the cotton belt have statutes which prohibit the importation or having in possession of live boll weevils for any purpose. whatever. (See the section at the end of this bulletin.) HIBERNATION.’ There are many popular misconceptions regarding the manner in which the boll weevil passes the winter. For this reason we take the opportunity to point out some general considerations about hiber- nation. Many forms of animal life suspend activity during the winter. This is the case with the boll weevil and many other insects, as well as with certain other animals. During this period of inactivity the animals which hibernate derive sufficient nourishment from a supply stored within the body to maintain life. They obtain no other form of food. In fact, the hibernation period coincides more or less with the periods in which the native food supply is absent. The temperatures which kill the cotton plant force the boll weevil into winter quarters, where it remains with suspended animation until spring. Almost coincident with the first sprouting of cotton we find the weevils leaving their winter quarters aad moving about in the fields. fs = act to ee importation or interstate transportation of insect pests, ete. (Act of Mar. 3, 1905, ch. 1501, 33 Stat. L., 1269.) * Two excellent publications on the hibernation of the boll weevil have been issued. These are: ‘‘The Hibernation of the Boll Weevil in Central Louisiana,’’ by Wilmon Newell and M. S. Dougherty (Cir. 31 La. Crop Pest Commission), and ‘‘ Hibernation of the Mexican Cotton-Boll Weevil,” by W. E. Hinds and W. W. Yothers (Bul. 77, Bur. Ent., U. S. Dept. Agr.). ie | HIBERNATION, 95 _ The long absence of the weevils from the cotton fields has led super- ficial observers to believe that the weevils pass the egg stage in the cotton seed. Such persons point out the fact that the weevils are found in seed houses and appear most abundantly in the fields near these buildings, and also that they have found insect larve in the seed. Asa matter of fact, the insects found in the cotton seed are not boll weevils, but other species which feed upon dried seeds and similar vegetable matter. The appearance of the early weevils in the vicinity of seed houses is due entirely to the fact that the protection offered there attracts many in the fall. Careful observations through- out the winter have shown that the boll weevil remains inactive except _ for very slight movements during very warm periods and that it does ' not breed in or feed upon cotton seed. _ As explained in another portion of the bulletin, the hibernation period is defined by the continuance of mean temperatures within what we define as the zone of hibernation. This zone has as its upper limit the mean temperature above which, if continued for any con- siderable period, the life activities must be resumed, and has for its lower limit the absolute temperature below which no weevil can live for even ashort time. For all practical purposes the hibernation zone hes between 56° and 12° F. METHODS OF STUDY OF HIBERNATION. In studying several features of the hibernation of the boll weevil the practice has been to utilize large cages covered with wire screen which were placed in the cotton fields. (See Pl. X, 6.) No cotton was grown in these cages, but at different dates in the fall large num- bers of weevils collected in the adjoining cotton were placed in the cages. It has been considered that the rate of survival of weevils in these cages installed chronologically is an index to the number of weevils that actually survive under natural conditions. It has thus been considered that with 1,000 weevils in a cage installed October 1, which showed a survival of 10 per cent, and a cage containing 1,000 weevils installed on September 15, which showed a survival of 5 per cent, twice as many weevils would have survived the destruction of the plants on October 1 as on September 15. Although there is no - doubt that this method gives a fairly accurate index, there is one objection that can be made to it. This objection is that the number of weevils leaving the field to go into hibernation as the season progresses, the number dying in the fields, and the number maturing there are not taken into consideration as the calculations have been made. On September 15 none of the weevils in the field would have entered into hibernation. By the 1st of October, however, a certain number would have left the field, and such weevils would not be represented in the collections made for the cage installed on October 1. It is not known whether the weevils which remain in the fields late are more or less hardy than those which leave early to find hibernating quarters. The indications, however, are that the stronger and more active weevils—that is, those more likely to survive the winter—are the ones which do not go into hibernation at an early date. Nevertheless the number that may have gone into hibernation between the dates of the installation of the various cages, the number that died from natural causes, and the number that matured in the fields during that 96 THE MEXICAN COTTON-BOLL WEEVIL. time must be considered. As a matter of fact, the total number c weevils in a locality on October 1 would be the number present in th cotton fields on September 15, less the total number dying betwee: September 15 and October 1, and less the number leaving the field te enter into hibernation during that period, plus those that matured during the same time. It is likely that the number of weevils matur- ing is generally sufficient to offset the number that die from natural causes. This leaves only the weevils which escape collection by entering into hibernation to be considered. As there is no way in | which this number can be determined, the method we have followed, | which ignores them altogether, is the closest approximation we can make to a determination of the actual number of weevils which suc-— ceed in passing the winter after the destruction of the food plants in — the fall. ; It is to be noted that the possible error in the interpretation of the — results of hibernation experiments becomes greater in the case of the cages installed late in the season. As the season advances more | and more of the weevils leave the fields and thus pass out of considera- tion in connection with the number collected and placed in the cages. The hibernation experiments conducted have dealt with 181,932 weevils utilized in seven different seasons in seven localities through- out the infested territory. ENTRANCE INTO HIBERNATION. SOURCES OF WEEVILS ENTERING HIBERNATION. Following the maturity of a considerable portion of the crop of ) bolls, and usually in connection with the occurrence of a heavy rain- fall, a renewed growth of the plant commonly produces an abundance of squares. It is this late top growth of the plant, which serves no good purpose so far as further production of cotton is concerned, that is primarily responsible in most fields for the needlessly large number of weevils produced between the time of maturity of the crop and the usual time of destruction of the plants by frost. A large proportion of the weevils which become adults before September 1 may be ex- pected to die, either as cold weather comes on or during the earl fe of the winter season. There is no particular hibernation eae nut representatives of all generations may survive and enter hiberna- tion, as has been shown by figure 14 in the discussion of the life cycle. STAGES ENTERING HIBERNATION.’ The reproductive activity of the weevil continues steadily until the plants are destroyed by frost, but it gradually decreases coinci- dently with the gradual decrease in temperature. All stages from the egg to the adult may be found in both squares and bolls, even after frosts have occurred. The immature stages in squares are not immediately killed unless the freeze is exceptionally severe, and in some localities many of these survive to reach maturity and to emerge during the following spring. Usually, however, only those Which are nearly adult at the time frost occurs may be expected to ' The matter in this section is mainly extracted from Bull. 77, Bureau of Entomology, pp. 12, 13, ? The matter in this section is largely extracted from Bull. 77, pp. 13, 14, ~ Bul. 114, Bureau of Entomology, U.S, Dept. of Agriculture. Fia. a.—BOLL-WEEVIL REMAINS AFTER PASSING THROUGH FAN FROM GIN. Fia@. b.—TEN-SECTION HIBERNATION CAGE. (ORIGINAL.) PLATE X. (ORIGINAL. ) a Ww Bu es oe =) Bul. 114, Bureau of Entomology, U. S. Dept. of Agriculture. PLaTe Xi. =D Ly Dall a Fig. a.—Cotton field adjacent to timber covered with Spanish moss. (Original.) Fig. b.—Proximity of moss-laden trees, conducing to high infestation by weevil. (Original.) HIBERNATION CONDITIONS FOR THE BOLL WEEVIL. HIBERNATION. 97 emerge. These might emerge upon warm days following the colder weather, but in the absence of a fresh food supply would soon die. In the fall of 1903 Prof. E. D. Sanderson, in an examination of 700 _ squares at the middle of November, found 79 eggs, which means that 11 per cent of the squares contained eggs. In an examination of _ 1,600 squares he states that 366 larve were found, showing that about _ 23 per cent of the squares contained larve at the time of entrance into hibernation.| Some stages may survive in squares for a short time after the freeze, but there are few records of weevils entering hibernation as immature stages in squares and surviving to emerge therefrom in the spring. These stages are therefore unimportant _ from an economic point of view. | With immature stages entering hibernation in bolls, the case is quite different from that in squares. Very large numbers of weevils enter upon the period of hibernation as immature stages and during many seasons, especially in the southern part of the State, a large percentage of these complete their development, and many survive until time for their emergence in the spring. Immature stages in bolls have been found alive at Victoria, Tex., as late as February 17. TIME OF ENTERING HIBERNATION. Hibernation begins when the temperature reaches a point between 60° and 56°F. The exact point will be higher with a high percentage of humidity and lower with a low percentage of humidity. According to the observations of Messrs. Newell and Dougherty.? at Mansura, La., in 1908, entrance into hibernation began on October 28. The mean temperature for 10 days preceding that date was 63.7° F., but the minimum dropped from 46° to 31° F. on the day the weevils began to enter into hibernation. The action of the weevils in securing shelter from approaching cold is instinctive rather than intelligent. It is probably true that they have no such sense of sight as we commonly understand from the use of that word and that their selection of shelter is not at all guided by that sense. We mean by this that a weevil on a cotton plant can not see at any distance shelter which might be attractive to it and thereupon fly from the plant to the shelter. Cold nights with a temperature between 40° and 50° F., succeeded by warm still days, such as occur commonly in the fall, seem to stimulate the weevils to an unusual activity both in flight and in crawling. It seems possible that they have an instinctive knowledge of the approach of temperature conditions from which they must secure shelter, but it is also true that many weevils remain active upon plants for some time after the plants have been destroyed by frost and frequently until several weeks after other individuals have entered hibernation. In speaking of entering hibernation, therefore, we mean the entrance of the weevils upon a period of comparative if not complete inactivity. Their action in securing shelter is gradual and governed primarily by the degree of protection from the cold which they may receive. If early in'the season a weevil accidentally finds shelter which gives it exceptional protection from the cold it will likewise be exception- ally protected from heat and therefore less likely than are other less 2 Cir. 31, Lousiana Crop Pest Commission, p. 170. 28873°—S. Doc. 305, 62-2——7 1 Bull. 63, Bureau of Entomology, U.S. Dept. of Agriculture. 0 98 THE MEXICAN COTTON-BOLL WEEVIL. fortunate individuals to resume its activity ae warm days. at first the shelter which weevils find is only slight they will be easil influenced by succeeding warmth, and in another period of activity will be likely to find better protection. Their fight upon warm day. undoubtedly leaves large numbers of them outside of the cotton fields, where they are more likely to find favorable shelter than within the fields themselves. From this explanation it will be understood that it is rarely pos- sible to indicate by a single date the time when weevils enter hiber- nation. It may be better expressed as a period within the limits of which a large majority, though possibly not all, weevils may seek shelter. Naturally this time varies according to the seasonal tem- perature conditions, so that in a certain locality it may occur several weeks earlier in one season than in another. It is also evident that differences in temperature conditions due to latitude or altitude will cause a similar variation in the time when weevils enter hibernation.! In Table XX XITI areshown the times of the yearin which the weevils entered hibernation in the experiments of 1903 to 1906, together with the temperature conditions prevailing. The table shows the relation- ships between humidity and temperature and the length of the period of entrance into hibernation. In short, it may be stated that the lower the mean temperature the shorter the period of entrance. Sufficient information is not at hand to show positively the influence of humidity, but it is evident that there is a decided influence. TaBLE XX XIII.—Period of entrance of the boll weevil into hibernation and meteoro- logical conditions. Period. Y Localit icmp ae ear. ocality. mpera- | pumidity. Limits. Days.d\g Cee = a oe Per cent. #905" | eDallasWlex Siee he pea. SOR eee Novi29=Dec: 8%. 3-3. 10 40.5 64.8 1903 | College Station, Tex...................- Novs15-27¢22 eee 13 49. Bee oe seek 2 ao ; TOOSsuVoCtOrIa Pex. = 822 oi. A TEST R oe: Nov215=30 222267 -aeee 16 Gt Ue ees See Bee 19052222 Oe ee Se eae ote, so aice ea oe Nov. 30-Dec. 18....-..- 19 SOF OH Soe a 1904517 Corsicana’ Vex oto se ck oo ee Nov. 10-Dec. 5......-- 26 SONU eee eee nee 19063 PDalias sexs soos tes eee tee ba ee Nov. 12-Dec. 8425. 27 53.0 73.1 19045) Victoria, Demers 22s. = Je 2a 2 20s So atm ara as | Nov. 11—Deci8" ee 28 57.5 79.3 1906 |..... Msi ct 8 mcs See Oe | Nov. 9-Dec. 21-...._.- 43 Gals Sera re Weevils can not be forced to hibernate when conditions do not nor- mally induce hibernation. If kept without food, they will starve. The real bearing of this statement will be brought out later in con- nection with the summaries of the survival in its relation to the time of beginning hibernation. (See Table XLVI.) NUMBER OF ADULT WEEVILS ENTERING HIBERNATION. Of course the number of adult weevils entering hibernation is a variable quantity, owing to the differences in the percentage of infes- tation in various regions and seasons. Examinations in heavily infested regions have shown averages as high as 58,000 adult weevils ‘This and the preceding paragraph are remodeled from Bull. No. 77, Bureau of Entomology. ee HIBERNATION. 99 } per acre in the middle of November. In this connection it is inter- esting to note the progress of entrance into hibernation as shown b Table XXXIV, based on investigations made at Dallas in fields with an average of 8,300 plants per acre. - TaBLE XXXIV.—Number of boll weevils per acre upon stalks at different dates at Dallas, Tex. Plants Living Living Date. exam- weevils | weevils ined. found. | per acre. 1906. (CYCLE PE es ea me 110 122 9, 205 Octz3l torNovesss.- 84 190 | 18,774 INNO alee ee ee 60 106 | 14,663 INOW IHD SS SEA GES EN Eee 35 29 6, 877 INO VWEN22 Se ees a 35 27 6, 403 TONES dats Serenata 36 10 2,306 DD CCHS ee eee erasone 35 5 1, 186 1907. AED A Leen nea AI le 35 3 711 1 From Bull. 77, Bureau of Entomology, p. 18. In connection with this subject we include also Table XX XV for the same period, showing the occurrence of the weevils under shelter on the ground in the cotton fields. TaBLE XXXV.—WNumber of weevils under rubbish on ground at Dallas, Tex.? pycergs Portion found— Percent- Field. Daler: of acre zeta age Remarks. examined. PCB OChes we aline: Alive. | Dead 1906. Ateee----| Nov. 15 | 22 plants. 4 0 1, 450 100.0 | In cracks of ground around bases 3 of plants. ACT een sel E's doses: 1/264 4 0 1,056 100.0 | Under rubbish on ground. AE eee NOVer 22 1/347 8 0 2,776 100.0 Do. AL ae Sele Dee, 18 1/264 5 14 5,016 26.3 Do. 1907. Berar Jan. 11 10/8384 5 2 5, 870 71.4 | Northeast corner of field. Crain he Jan. 29 10/6236 1 al 1, 247 50.0 | Middle of field. Coase: Gonsae 10/8384 2 2 3, 354 50.0 | Near southwestern edge. 2 This table and the following paragraph are taken from Bull. 77, Bureau of Entomology, p. 20. The sum total of weevils found both on plants and on the ground on November 22 shows an average of slightly more than 9,000 weevils per acre, all of which were alive. On December 18 the number that could be accounted for was between 6,000 and 7,000 per acre on the same ground which had been Pee examined. On the former date more than two-thirds of the weevils were still upon the plants. On the latter date nearly five-sixths of them were on the ground, and among those on the ground only 26 per cent were living. These fig- ures show that between November 22 and December 18 a very large mortality had occurred among weevils which had entered hiberna- tion, and especially among those which had sought shelter under rub- bish upon the surface of the black-waxy soil of field A. 100 THE MEXICAN COTTON-BOLL WEEVIL. SHELTER DURING HIBERNATION. \ Boll weevils in seeking shelter from the cold will enter all kinds of places which might afford shelter. The following statements are quoted from Prof. EK. D. Sanderson: ' The observations by Prof. Conradi at College Station, Tex., in the early winter of 1903, probably indicate some of the normal places for hibernation—that is, under dead leaves, in old cotton brush, and under loose bark. In the hibernation cages, where the weevils were furnished an abundance of rubbish, it was found that many of them which were hibernating successfully had crawled into the cavities made by borers in dead wood and in similar positions where they were well protected. It has been often noticed that in a wooded country the weevils appear first in spring along the borders of fields next to the woods and gradually work inward from the edges, so that it seems probable that in a wooded country most of them hibernate in woodland. Around outbuildings and barns also are found favorable places, as there is always more or less rubbish and protection in such situations. In 1903 more than five times as many weevils were found in a piece of cotton near the college barn, where cotton had been grown the previous year, than were found in any other locality in that neighborhood. It is also noticeable that weevils are always more numerous near gins than at a distance from them. It is noticeable that weevils are much more abundant where cotton is planted in fields where sorghum stubble has been allowed to remain all winter adjoining a last year’s cotton field. Professor Mally has given the observations of Mr. Teltschick upon finding weevils hibernating in the crevices of the soil around the cotton stalks and roots, at a depth of 3 inches. On March 7, 1901, a raw, windy day, upon 35 stalks, he found 7 live and 2 dead weevils from 1 to 3inches below the surface. In September, 1902, he stated that he had again found weevils in a similar situation during the previous spring, but not as many of them asin 1901. Mr. Teltschick recently writes as follows: ‘‘T found but few weevils in crevices around stalks during the last two winters, partly because there were no crevices (frequent rains filling them up as soon as formed) and partly because freezes were severe enough to keep cotton from coming out during any part of the last two winters; whereas in 1900 we had neither rain enough to fill up crevices nor frost enough to keep cotton from budding out at intervals at the base of the stalk, which latter fact accounts, no doubt, for the relatively large number of weevils found within the crevices.”’ Where the cotton stalks are allowed to stand throughout the winter they furnish the weevils both the means of subsistence late in the fall and an abundance of favorable hibernation places through- out the field. The prospects of successful hibernation are thereby multiplied many times, and, furthermore, the weevils are already distributed over the field when they first become active in the spring. The grass and weeds which almost invariably abound along fence lines are exceedingly favorable to the hibernation of many weevils, so that it will be found generally true that the worst line of infesta- tion in the spring proceeds from the outer edges of the field inward. Where cotton and corn are grown in adjacent fields, or where, as is sometimes the case, the two are more or less mixed in the same field, many weevils find favorable shelter in the husks and stalks of the corn. An especially favored place is said by Mr. E. A. Schwarz to be in the longitudinal groove in the stalk and within the shelter of the clasping base of the leaf. Perhaps the most favorable of all hibernating conditions are to be found among the leaves and rubbish abounding in the edges of timber adjoining cotton fields and in Spanish moss. From such sources the weevils are known to come in large numbers in the spring. Sorghum stubble, which collects débris blown about by the wind, is also very favorable for hibernation. ' Bull. 63, Bureau of Entomology, U.S. Dept. Agriculture, pp. 18-19. Bul. 114, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE XII. Jig. a.—Standing dead timber and forest environment favorable for hibernation of weevils. (Original. ) . . . fig. b.—Litter in forest, suitable for hibernation of weevils. (Original.) HIBERNATION CONDITIONS FOR THE BOLL WEEVIL. Bul. 114, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE XIll. Is in = S il.) 3 (Origin ntion. hibern Fig. b —Density of Spanish moss as a protection to weey HIBERNATION CONDITIONS FOR THE BOLL WEEVIL. ible for hibernation of rery favor (Original.) > eae ad > - weevils. —-Spanish moss on trees; lig. a. HIBERNATION. 101 Attention has already been called to the fact that many stages enter the period of hibernation in an immature condition in unopened bolls. That adult weevils hibernate entirely within the protection afforded by the bracts and hulls of bolls has been abundantly demon- strated. Messrs. Hinds and Yothers! showed, however, that the percentage of live stages in bolls decreased rapidly during the winter, _ thus proving that the bolls do not furnish perfect hibernation, shelter. Their results may be summarized as follows: | Taste XXXVI.—Seasonal decrease of live stages of the boll weevil in bolls; percentage of bolls containing live stages. DROIT IVEN sv oS ees SR ee on 36. 00 JISROISIER. Sie Je. = BPS apts OA Se RE a en ne ee 1.15 LP SINRUGINT , 3 cin abe ae RS a eee 0. 29 MUSUNCID 22 Wy cin, BAR Re St a ee a ae ee 0.00 As would be expected, it was found that there was a greater per- centage of survival in bolls in southern localities. - 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.? (Pl. XII, b.) 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 rather important factors where they occur in considerable numbers. (Pl. XII, a.) Where the Spanish moss (Tillandsia usneoides) occurs, as in the bottom lands in the coast section of Texas and in the southern por- tions of the Gulf States generally, weevils find exceptionally favor- able shelter. Many examinations of large quantities of moss have been made to ascertain the importance of this form of shelter. The maximum number of weevils per ton of moss is recorded by Messrs. Newell and Dougherty (1909) as 3,158 in moss collected from an elm tree located in a swamp at Mansura, La., December 23, 1908. The moss was at a height of 15 feet. The tree was one-fourth of a mile from the nearest cotton field. On January 9, 1910, Mr. C. E. Hood found at Mansura 924 boll weevils and 2,156 boll-weevil para- sites per ton of moss collected at from 1 to 8 feet above the ground. The weevils seem to prefer the festoons of green-hanging moss to the dead masses. (See Pls. XI, XIII.) Cornfields adjoining cotton, or cornstalks scattered throughout cotton fields may shelter many weevils. This was first noticed by Mr. E. A. Schwarz at Victoria, Tex., in the winter of 1901-2, and has since been corroborated by a number of observers. Several examinations have been made of haystacks in the vicinity of cotton. 1Bull. 77, Bureau of Entomology. gees . 2 This paragraph and the remainder of the discussion in the present section is modified from Bull. 77, Bureau of Entomology, pp. 30-33, 41, 42. a 102 THE MEXICAN COTTON-BOLL WEEVIL. This is a task quite comparable with that of seeking for the pro- verbial 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 favorable shelter for weevils. Especially in ginneries and seed houses the weevils become concentrated with the cotton or seed and frequently may be found in large numbers within or around these buildings. In connection with this subject the reader is referred to a fuller discussion of the significance of ginneries and oil mills in the distribution of weevils and of the methods recommended for con- trolling them.! In order to have a basis of comparison of the various kinds of shelter, Many cage experiments have been conducted. In Table XXXVITI will be found a comparison of the survival in the cages at Keatchie, La., for weevils installed November 23 and 29. TaBLE XXXVII.—Favorable conditions for hibernation determined by rank in per- centage of weevils surviving at Keatchie, La., in 1905-6. Weevils survived. Weevils Nature of shelter. put in. Number. | Per cent. Ordinary field'stalkserass: etesis 5... fo ta) ee ee eee ee 2,000 93 - 4.65 Brush, leaves, stumps, logs; stalks standing..................--2..-- Ere ee 2,500 99 3. 56 Sameias above, butistalks removed . 52 320.222. 2513. eee ee ae 3,300 70 2.12 Cotton seed, piled but uncovered; stalks standing.....................-..- -2,000 30 1.50 Absolutely bare Pround see oh 28k See eee ees oe ee ee | 2, 000 30 1.50 Cotton seed piled and covered; stalks left standing ....-...-..--....--...-- 2,000 23 1.15 1 From Bull. 77, Bureau of Entomology, p. 42. It is evident from these observations that ordinary field conditions where stalks are allowed to stand together with the grass and leaves littered over the ground are as favorable as any other for successful hibernation. One fact should be emphasized in regard to 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 practically all of them. Undoubtedly the burning of cotton stalks, weeds, grass, and other rubbish is the easiest and most effective method of destruc- tion where it can be practiced. Next to this in importance would be the destruction of the stalks by a stalk chopper and plowing under alltherubbish. In the latter case it must be stated that many weevils which, under dry conditions, are buried not more than 2 inches will be able to escape through the soil and may then find shelter near, if not within, the field. ‘ Farmers’ Bull. 209, U. S. Dept. of Agriculture, “Controlling the Cotton Boll Weevil in Cotton Seed and at Ginneries.”’ HIBERNATION, 103 ACTIVITY DURING THE HIBERNATION PERIOD. It is natural to expect that during warm periods of winter the tem- perature will rise to a point which forces the weevils into activity. Of course, the weevils under the lightest shelter are the ones which first become active. It is these warm periods which cause the inter- mittent development of the immature stages in dry bolls left in the fields. In some winters the hibernation is incomplete throughout the cotton belt, and in the extreme South it is probably so almost every winter. This same temperature condition is responsible for the growth of sprout cotton, which affords food in the warm periods. Observations were made in January, 1907, on weevils fase on sprout cotton at Victoria, Tex., at a mean temperature of 67° F. DURATION OF HIBERNATION PERIOD. AVERAGE LENGTH OF HIBERNATION PERIOD. Many factors must be considered in arriving at the average length of the hibernation period. The time of entrance, condition of the weevils on entering, temperature and humidity before and during hibernation, and nature of shelter, all have a decided effect upon the duration of hibernation. Im a series of condensed summaries we have attempted to show how some of these factors act. In Table XX XVIII is to be found a general summary of the nine large experiments conducted, with the extreme variations in each series. Krom this table it appears that in the years 1906 to 1911 the hibernation period has tanoed between 62 and 255 days, and that in 1909 the range fell short only 1 day of this maximum range. It also appears that the average duration in Texas is 26 days shorter than in Louisiana. The period of emergence extends from Feb- ruary 15 to July 1. TaBLe XXXVIII.—Extremes of variation in duration of hibernation by the boll weevil. Total Total Pee - | Mini- | Maxi- | Aver- Place number |} number ee eek mum | mum | age of Earliest yetest ‘ weevils | weevil eriod.|period.| 2V@r- | aver- | aver- | emergence. ance emerged.| days. |? |P ‘| age. | age. | ages. Bone Days. | Days. | Days. | Days. | Days. Keatchie, La., 1906.... 731 114, 192 108 222 136 178 156 | March 22....| June 28. Mansura, La., 1909... -. 3,260 | 516, 067 62 254 94 199 156 | February 21.| June 29. Mansura, La., 1910..-.-. 1,038 | 170, 212 86 232 114 217 164 | February 15.| June 15. Tallulah, La., 1910....- 317 58, 245 103 237 126 224 183 | February 15.| June 27. Tallulah, La., 1911..... 46 6, 587 107 231 118 158 143 | February 15.| June 4. Louisiana aver- ALOE snes 5,392 | 865, 303 62 254 94 224 160 | February 15.) June 29. Victoria, Tex., 1907....| 3,028] 383,797 92 223 95 146 126 | February 28.} June 15. Calvert, Tex., 1907..... 1,842 | 255, 831 91 255 100 195 138 | March 4..... July 1. Dallas, Tex., 1907......| 3,462) 481, 271 85 233 98 168 138 | March 1..... June 19. Dallas, Tex., 1908...... 118 17, 839 113 217 121. 170 151 | March 2..... June 16. Texas average...| 8,450 |1, 138, 738 91 255 98 195 134 | February 28.) july 1. Grand total..... 13, 842 |2, 004, 041 62 255 94 224 144 | February 15.| July 1. THE MEXICAN COTTON-BOLL WEEVIL. 104 *9oTIOsIOULO ON 1 PPL 9% “AVY | F6 €t ‘adv | 921 @ ‘aidy | Ost 1@ “AVW | 681 6 “ady | 891 yp ‘idy | OST STOWE OL = eal Se ee OBvIOAB poyysiom purely ea Sl es PL ‘ABW | 86 6 “AVA | OTL €% “ABW | Sel €Z “AV | IST 1% “AV | 99T TAM Sh el 0) 2 ae | oad OFVIOAG poyysIoM SVxoy, eG OSS | 2 iia cae ine 0% “AV | 221 Og “AV | THT Tt ‘ady | 2ST 1Z “Le | O9T LT ‘te | OLT “"""8O6T “XO, ‘Seed | SOE LS Nella la aa aaa PI “ABW | 86 6% “VW | G2l 9% “AV | SET 0% “lv | GFT 6% “IV | 89T Rilips op anind elie meine a fea ee VANS CHANCE 2 OSES OE Ee lien lniaiaeage mceaala €L “BW | OOT bZ “AV | GIT t cady | Gr1 ST ‘ady | SLT 8% “AVA | 99T (coaches slhae eater | ee SLO) ASO koa LEO nese eet arr ee yn ee 61 “VW | SIT ZS “AVI | ZET PT “AV | 6ET agea Str | a eee apes = Fle ee lee LOOT SO EIOOL A, OoT ~—s«- | 9% “ABW | ¥6 gt ‘ady | 621 €% “idy | IST Gt ‘ady | ct b% “idy | 8st gt “ady | 061 Che IA Vi SORT fame aml op OdBIOAB PO -JUSIOM VUBISINO'T _ aS] tele eat ba nai by peek oe gil ea?) eee a(t) a seem eo. ABI | S27 0% “TVW | 9ST eet alee ae) eee O Lee. MeL ey 0 SES EG) Co ion icing (aia aaa G poral Og Adve |sopT 9T “dy | OT Gt ‘ady | &2T LI AV | 61Z G AVW | FZ ""-OT6T “RT “YRINITRL, eis |e g Avy | 91 9% “dv | 6ST @@ “Ady | 291 L ‘idy | SOT 8 ‘idy | OST € AvW | LIZ ““"O16T “ey “ensue ap fet TE 9% “IV | 66 er “ady | P2r ct “ady | €hI Ir ‘adv | 2ST 0g ‘idy | S8T 1% “lV | OLT Ig “Iv | Est """G06T “VT ‘RInsUeyy 0 SESS Ca te SR Ste lil Sens SGI s| OFT JT Avy | SST Bol sletelestolete!|(atasotpnleloioss/=|(ch-1sinis/\=/aj0/=['4i0'=ininiein anal sinicia a\clopinia}eicie cistern ciciie aren mice | etc ea alae aa OG as B -Old0] Com ‘shoq shivg ‘shod ‘shog ‘shog ‘shng ‘shng shog meco)oucial “OIC “HOlyeUu “HOI]eU meceauciel meceauciet “HOIYVU ‘pos10urgy| -Loq rt JO | ‘postourg’] -toqiy Jo | *posrourgz| -Aoqry JO | *posLourg] -1oqry Jo | ‘posr1ourgy -Loqry JO ‘posdourny| -Loqiy Jo | ‘postoursy| -loqry jo ‘uoneu ysue'y ysuo'T yysue'T Yysue'T yysuo'T yy suey qysue'T 5 -loqry |—— : ’ RI OsBIOA VY "1-91 “00, *T-T “00d ‘0-91 “AON, “CI-T “AON “T8-9T “JO *GI-T “290 “og-9T “3dog ‘HOLL BI[BISUL ‘HOI) BI [VySUt “LOI RI[CISUL ‘HOLY VI [VISUL “OI} RI [VISUL ‘MOT}RI[V]SUL ‘UOI}B[[VISUL Jo ull, jo oul, Jo OUI, JO ONT], JO OULLT, jo OWL, jo OWL ‘uoynypnjsur fo ayop 0} paywjat sv praaam y0q ay) fo porsad uoynusagy fo yjbua) abvi00py— XITXXX IIAV, HIBERNATION. 105 Knowing that the time of entrance affects the percentage of sur- vival, it is also reasonable to expect an effect upon the duration of the hibernation period. Table XX XIX has been constructed to show the average duration and average date of emergence at each locality for all weevils entering hibernation in each half month during the several seasons of the experiments. It will be noted that the length of the period, with a few minor exceptions, decreases in accordance with the lateness of entrance. It is very strikingly shown that in any given period of entrance the duration in Texas is considerably shorter than in Louisiana. On the other hand, it is impossible to show from this table any progression in the average date of emergence. The diagram (fig. 22) shows graphically the correspondence between date of installation and period of hibernation and emphasizes the differences between Texas and Louisiana. So Ae 2S ee RELATION OF SHELTER TO DURATION OF HIBERNATION. That the nature of the hibernating quarters has a direct bearing upon the duration of the period is to be gathered from the records of Messrs. Newell and Dougherty made at Mansura, La., in 1909, which are abstracted below: TasBLE XL.—Comparison of length of hibernation of the boll weevil in different shelters at Mansura, La., 1909.! Number | Number | Average Average Nature of . of of number Date started 1908. hibernation pogeuon of | weevils | weevils | of days fateies quarters. ee con- surviving] in hiber- ence tained. | winter. | nation. 8 : OCTODCTE2 Oh aes eye cee Average...| In open field... 1, 294 325 169.1 | April 13 IDG). 3s GSS HSS SEER COS Se ae Seem eer do....| Inswamp....-- 1,142 162 173.3 | April 17 DOES < BR Rey ia ae Ree MOSSE eee In open field. . 1,214 409 190.9 | May 4 IDO S GARE SEA sen OSes ned were ier (eee do ....| Inswamp..... 938 408 199.4 | May 13 WOU SS S25 dries} 5 5 2 ele een |e gee aif areca a 4,588 Te S043 Nase so eos oe ee wee AT OIRGO8 gate cs S58 p64 Sack at eee are |e espe rere et se (yee es race Pieeenearraee 85.0 | April 28 . 1 This table and the following statements are extracted from Cir. 31, State Crop Pest Commission of Louisiana. Consideration of Table XL reveals the interesting fact that weevils hibernating in the cool, shaded situations in timber remained in hi- -bernation an average of about seven days longer than those hibernating in the open field. Weevils which hibernated in moss in the swamp remained in hibernation practically 200 days, and those which passed the winterin moss on trees in the open field remained in hibernation 191 days. In marked contrast to this the weevils that hibernated in a general assortment of materials in the open field remained in hibernation only 169 days, though gathered from the cotton fields at exactly the same date in the fall of 1908. This prove the dangerous nature of the moss, for it really causes the weevils in it to remain in hibernation for nearly a month longer than they would if hibernating in other materials. | Table XLalso illustrates the influence of temperature upon the dura- tion of the hibernation period, for there is no doubt that it 1s the temper- x 106 THE MEXICAN COTTON-BOLL WEEVIL. ature prevailingin the exact spot where the individual weevils are hiber- — nating that determines the date of emergence from hibernation. Piles — of grass in the open field are warmed by the sun in February and March, | and the weevils emerge from them at that time. The shaded places of the forest or swamp are cool and damp, and they do not reach an NOVEMEER: /0 20 DECEMBER ———? /0 20 3O Fic. 22.—Diagram illustrating average length of hibernation period of the boll weevil as related to date of entering hibernation. (Original.) equivalent Lerpey te until some weeks afterwards, and the wee- vus consequently emerge later in such places than in the open fields. The bunches of moss are so resistant to heat that even in the hottest days of summer they are very noticeably cooler than the air. EMERGENCE FROM HIBERNATION. TIME OF EMERGENCE. The time of emergence of the boll weevil from hibernation ranges from February 15 to July 1. It is necessary to discuss the conditions which cause this irregularity. A careful study of all the series of experiments to determine the immediate causes for the first decided impulse to emerge has resulted in the following conclusion: That the as oa HIBERNATION, 107 time of emergence varies with the total effective temperature and the rainfall. Computing the total effective temperature from Jan- uary 1 in daily units of mean temperature above the mean of 56° F. (average zero of effective temperature) it is found that approximately 172.6° F. of effective temperature and 5.1 inches of rain are necessary to bring the weevils out of hibernation in comparatively large numbers. If the rainfall is greater than 5.1 inches the necessary effective INCHES PRECIPITATION F Sj 6 th 8 &) /0 PRECIFITATIP 70° 95° 220° 120° 148° 170° 1952 245° 270° DEGREES EFFECTIVE TEMFERATUAE. 295° Fig. 23.—Diagram illustrating relations of effective temperature and precipitation to date of beginning emergence of the boll weevil. (Original.) temperature usually will be less than 172.6° F., and, on the other hand, if the total effective temperature is greater than 172.6° F. the necessary rainfall will usually be less than 5.1 inches. This may be seen by reference to Table XLI and by the diagram (fig. 23). Dis- crepancies will occur with regard to this formula and will in a large ore be due to the type of shelter or to great irregularities in the climate. 7 TaBLeE XLI.—Relation of effective temperature and precipitation to date of beginning emergence of the boll weevil. Total ; effective Total D Bicol Place. tempera- | Precipita- hp ture from tion from extensive ipa. Jan. 1. emergence. hie Inches. Tsien, IONS SSosssssensos so ab cen dees SraesseoerESonoesonbooE 65 10.5 | March 1. MansuralOlOse. sie: EO bef oe Vinee air cee np Late Se ATA ape So Ne 115 7.3 | March 2. IDRIOS, IOWs Hc coe'sGae Hee See bee acme bee 20 daeacoeacee capostocrE 160 6.5 | March 12. Dallas, 1907.....- Se inate ee AP Pat Ly EE TIO 170 2.2 | March 3. Nile ore) WOOO: obs teks kao e hanes bec oeeonude asersonsoucsasae- 185.5 5.5 | February 21. With, ISO. Bowtctdeekoboe ore anoUe HobedeosodccPeasdsocondoeoose 260 1.3 | February 23. BeR@ALVONE LOOT se coca clos cies orem woes me ee nemlnininie cin ee eile en sie oie ene : 303. 7 2.35 | March 5. a —- a a. -— A a ee — en — ee. 108 THE MEXICAN COTTON-BOLL WEEVIL. ‘ Figure 23 shows graphically that climate influences the time of beginning emergence. It also has a decided effect upon the sub- sequent emergence. In Table XLII is shown what effect the daily mean temperature has upon the hibernating weevil. Taste XLII.—The relation of emergence of the boll weevil to increase in temperature at Keatchie, La., and Dallas, Tex., 1906.) “ | Keatchie, La. Dallas, Tex. a bck" Per cent = number | based on Range of temperatures (° F.). Bumper Per cent per Per cent of nd weevils | Of total | yeeyys | of total | weevils total emerg- emer- | omerg- emer- | emerged. | emerged. ing. pence, ing. bee 7G Ey ei eae ee Send cae tines SA 20 2.7 0 0 20 2.5 os ee oe ees ep Saree 52 7 2 3.6 54 6.8 Ce ee eee mente, eee 116 16.0 25 45.5 141 17.8 it Be ee oe es Aart BS ee TS er te 127 17.5 18 32.7 145 18.5 7 Ss fs PS Mie Focal Sea hee ee Aes, 309 42.4 10 18.2 319 40.7 7k BES OE cee ees Ree See a gee eee OA 84 11.5 0 0 84 10.7 ES ee on ae aa ele one | Oe 20 2.7 0 0 20 PAF Total Se on oc ee ae ee eee er 728 100.0 | 55 | 100.0 783 100.0 1 Modified from Bull. 77, Bureau of Entomology, p. 44. The number of weevils emerging under 57° F. is very small indeed. From that point the emergence increases with the increase in tem- perature until a majority of the weevils have emerged. Most weevils have been found to leave their winter quarters during a temperature averaging between 64° and 78° F. At Keatchie 75 yer cent and at Dallas 96 per cent of the total emergence took place Eeteen these limits. At Dallas the largest emergence occurred between temperatures of 64° and 68° F., while at Keatchie the largest emergence occurred between 74° and 78° F. In a preced- ing paragraph we have shown that higher temperatures are neces- sary to affect the weevils hibernating in Louisiana, apparently because of the heavier shelter. RATE OF EMERGENCE. With a long-continued emergence period it is important to deter- mine whether the rate of emergence is equal at all times or has its periods of retardation and acceleration. Upon charting the per- centage of total emergence for each week it was noted that the Texas and Louisiana points differed considerably. On the accom- panying diagram (fig. 24) the four Texas series are consolidated to give the average rate, and likewise the four Louisiana series are consolidated, while in Table XLIII the records for each locality are given. It is immediately apparent that the emergence begins much HIBERNATION. 109 more abruptly in Texas than in Louisiana. In Texas 25 per cent have emerged by March 12, 50 per cent by March 21, 75 per cent by April 8, and 100 per cent not until June 19. On the other hand, in Louisiana 25 per cent have not emerged until March 30, 50 per cent until April 27, 75 per cent until May 16, while 100 per cent will have emerged only by July 3. Herein hes a powerful argument for early planting. With 50 per cent of the weevils emerging after March 21 in Texas 700 FEB. MARCH AFF L. MAY |. SUNE SULY” PERCENTAGE OF TOTAL. EWIEVPGENCE Fic. 24.—Diagram illustrating average rate of emergence of the boll weevil from hibernation in Texas and Louisiana. (Original.) and 86 per cent emerging after the same date in Louisiana, or with 75 per cent emerging after April 8 in Texas and 64 per cent yet to emerge after the same date in Louisiana, it becomes evident that every day gained in Texas before March 21 or in Louisiana before April 8 is of immense importance in the fight against the weevil. Even later than these dates every day counts a great deal, because it is apparent that the longer planting is deferred the more weevils will be out to attack the cotton when it comes up. ees oh La 110 THE MEXICAN COTTON-BOLL WEEVIL. Taste XLIII.—Percentage of total emergence of the boll weevil out at given dates. Keatchie,| Tallulah, Mansura,| Mansura,| Dallas, |Calvert,| Dallas, | Victoria, | Tallulah, Date. | ae as oe cooks cee to ec ee ee March 31..} April 29...] May 24....) June 21. Swainpi(cares BanGg51).62. 2222222) ee ee Rr eae April 8....| May 20....| June1_...} June 29. Mossi(caves/Atanduib)) eee Benn 0 ee. Re fan eee | April ay goles oS ee June 2.=<.| “Do. It will be noticed that only four cages entered the consideration, cage 5 being average quarters in open field, cage 51 being in average quarters in swamp, cage A being Spanish moss in open field, and cage being moss in swamp. SURVIVAL OF HIBERNATED WEEVILS. The central idea in all the hibernation experiments has been the determination of the percentages of weevils which survive under different conditions and different treatments. In obtaining the facts which have been discussed in the preceding and following paragraphs on hibernation the grand total of 181,932 weevils has been used. With such a large series it is reasonable to suppose that the average yercentage of survival must very nearly approximate the normal. ‘his survival in nine series of experiments conducted in seven years at six localities representing the principal climatic, shelter, and other conditions of the infested region has been 7.6 per cent. Table XLV presents the final summaries of each ot the nine series. HIBERNATION. iba I | TaBLE XLV.—Summary of survival of the boll weevil in all the more important expervments. Total Total number of | number of Places weevils weevils PON, : entering | surviving ped dete hiber- hiber- nation. nation. UATESIROIO. Wey MOTOS See ae a 24, 700 731 2.1 PNM), LP" GION 5 oS RN aie ea ae a a oe Oe 16, 281 3, 260 20.0 vec Psd, Bee OOS See Sie a eee ata ee ae ee ee 22,179 1,038 4.6 Tes @ NE TOES LPRIIICO) ET se 1 tea ge 21, 835 317 1.4 (MERI 1a 5 TAI 2 ea Se ae 8, 439 46 -O TIS® LLGWUISRE WME) STE SS 3 CP ge eg eee 93, 331 5, 392 5.7 DDS, SRO NOD lec oa 5 ot aes oe ne ee i a 32, 439 3, 464 10.6 Malverts exe MIO 7 ooo. Bee st Bae te yee eee rafarteiSre sails Setar cities ays 20, 430 1, 834 8.9 ‘FGI SNORE 5s UO ev lee Sie a a en 23, 645 3, 026 12.8 DEES, SECS G op QOS 5 cles st St ape a 12, 087 118 9 DOWIE TNORAS! SORES 25S 5 See eee eee ee eh a 88, 601 8, 442 9.5 DUNE! OIRMIN® SOM oc ic cf Tes ee eee ee 181, 932 13, 834 7.6 The highest average percentage of survival for any locality is 20 per cent, at Mansura, La., in 1909, and the lowest average is 0.5 per cent, at Tallulah, La., in 1911. The highest percentage of survival In any cage was 47.72 per cent of 767 weevils, at Mansura, in a cage with average conditions established December 14, 1908. The lowest percentage of survival is no weevils, from 408, at Tallulah, in two cages with average conditions, established November 15, 1910. RELATION OF FALL DESTRUCTION TO SURVIVAL. One of the most important recommendations for boll-weevil con- trol is that of early destruction of the cotton stalks. It has long been known that the earlier the stalks are destroyed the less chance the weevils have of surviving. Table XLVI, showing the percentage of emergence by dates of installation, affords an incontrovertible argu- ment in support of this recommendation. TaBLE XLVI.—Percentage of emergence of the boll weevil, by dates of installation. Place. Texas points. Dallas 190 fsa = tosses Sess Caliviertrel 90 (Gees ere seas Victoria, 1907...-- Ey too eae Ate DANA PONE ea seeme etn se cees Texas, weighted average DCLCE MAS Cease) Total weevils installed.......... Louisiana points. - ieentehies (90629 3-22 soe ese WMTW OFS E TGS) eh es 2 eae che era Maras tires SIO eps es aioe 2! TEV IC NSS Bae aus Sore ee Maliwlahe lOc ee noe coataae Louisiana, weighted aver- age percentage-.---..-5- Total weevils installed........-- Grand weighted average OCECCMLAS Crepe sole teielaio ares Total weevils installed... - Sept. 16-| Oct. 1- 30. Oct. 16— | Nov. 1- | Nov. 16-| Dec. 1- | Dec. 16- i5%4 31. Ne 30. alsy Olt Per cent.| Per cent. | Per cent. | Per cent. | Per cent. 6 6. 67 20. 57 ASSO ulin te sae os rare ees Bells 3.98 10. 33 PEN ee Se ase (3 aa amet Na ie 6.17 17. 69 NG SQO Me aces Sag Nl ae Se .39 2.8 1.68 Os 265 |eeeeies eee ee ee 2.33 5. 62 15. 42 1a eR 015) ee ee ee reeled oe 7, 729 27, 806 30, 431 ea ie eee emer! Seer bier ES ay Selah Ra) Lak Nee eee UR OH 250 3823 0.8 BeOL 23.9 23.8 24. 56 43. 23 37.06 eit 6.58 9.95 6.31 6279 See 2. 23 Takes le 1S 2.4 S00! S525 eae 1 G3 .54 SOR | eee se ee 00) Be se eae 2.00 8.04 8. 82 6. 07 10.65 12.61 14, 218 24, 464 9,620 24, 252 10, 208 1, 483 2.07 6.58 14. 26 9.00 10. 65 12.61 . 21,947 52, 270 40,051 36, 425 10, 208 1, 483 — *, 112 THE MEXICAN COTTON-BOLL WEEVIL. Converted into terms of the number of weevils in every thousand which would survive the winter if stalks were destroyed on a given date, we can see the force of Table XLVI. It is even more evident from the arrangement of the data given below in Table XLVII. Taste XLVII.—Number of boll weevils in each 1,000 which would have survived destruction of stalks on a given date. : : In Loui- Date of destruction. In Texas. | Sate | ofpey en) eed G81 Re ee ec = Rarer se aae saacce shane se seescee sec 2 | 3 October 1—1b seo. an oe ae he Se See oe ee ee ee ee 23 20 Ootoher 16-s1e+; ~ = n E Pe Sn oo e Ate fe ols cle eee eS ee 56 80 November 1-15.58 -.2 -fesk eset ete eos et So Ae Se oe a ee ee ee 154 88 November: 16-30) 2 ose oe a ns een oe ee Se oc cisniec eee ee ae eee Eee 160 60 Dacember 1-15 oo 5s eee ois ces ne Se io ee oc ae ee ee (?) 106 PecaM DEM GSU e Neen ee ne ear A eines cecines tre Seek oe Ce ee (?) 126 RELATION OF SHELTER TO SURVIVAL. It has already been stated that the density of the shelter has a bearing upon the survival. This is best shown by the following records (Table XLVIII): Taste XLVIII.—Relation of shelter of boll weevils to their survival. Place. Date installed.) Weevils. Shelter. Survival Per cent Mansura asa Sa Secsc se ia atest eect A eee October 26... -- 2,436 | Average... .--- 20. 00 A DY eR ES Vee 5 ee ae 2 SaaS 5 ae an ee ane 2 OB ey teat 2 E dors 258): MOSSso22 feeeee 37.76 Victoria, Tex....- Ree iops ope oe pe os ores ae October 28. ... 2,375 | Average....-.- 5. 61 AD {ei Sy RS th. CA age Hale mA ol a Sh | November 6... 25 800 4) SLOSS eee ee 23. 65 1D (tang A Rie ee ah a os eo hs oe Lg Ss BB November 10.. 2,850 | Average....... 12.7 RELATION OF CLIMATE TO SURVIVAL. Another important consideration in determining the causes for high or low survival is the climate. Some of the principal relation- ships are brought out in Table XLIX below: TasLte XLIX.—Relation of climate to survival of boll weevils in hibernation. Rainfall and tempera- ture, Oct. 1—Mar. 15. | Number | Per cent Description. of of sur- weevils. vival. Periods of emer- gence. Abso- | Total Rain- | lute {degrees fall. mini- | below mum. 32. Inches. ae mee Place and year. Tallulah, La., | 10 cages, variety of 8, 439 0.5 | Feb. 15-June4-..-} 8.30 9.5 199.5 1910-11. shelter, installed Oct. 15-Dec. 1. Dallas, Tex.,| 9 cages, variety of | 12,087 .9 | Feb. 19-June 16.-| 22.61 15.0 233.0 1907-8. Shelter, Sept. 21- | Nov. 18. Tallulah, La., | 19 cages, great variety | 21,835 1.4 | Feb. 15-June 27-..| 19.34 13.0 378.5 1909-10. of shelter, Sept. 16- Dec. 14. HIBERNATION, 113 | Tasuz XLIX.—Relation of climate to survival of boll weevils in hibernation—Con. Rainfall and tempera- ture, Oct. 1-—Mar. 15. Number | Per cent | periods of emer- Place and year. Description. of fsur- 4 : 4 weevils. Sail Bones : Abso- | Total Rain- | lute |degrees fall. mini- | below mum. 32. : ; Inches.| ° F. CAN, Keatchie, La., | 18 cages, variety of 24,700 2.1 | Mar. 22-June 28..| 18.87 21.0 91.0 1905-6. shelter (1 bare), in- stalled Nov. 18- Dec. 18. Mansura, Tex., | 19 cages, great variety 22,179 4.6 | Feb. 15-June 15..] 15.37 19.5 151.5 1909-10. of shelter, Sept. 16- Dec. 14. , . Calvert, Tex., | 10 cages, variety of 19, 408 8.9 | Mar. 4-July 1....| 11.87 26.0 47.0 1906-7. Sn eted: Oct. 1-Dec. 0. Dallas, Tex.,| 10 cages, variety of 30, 864 10.6 | Mar. 1-June19...) 8.52 22.0 145.0 1906-7. shelter, Oct. 13- : r i Dec. 6. Victoria, Tex., | 10 cages, variety of 22, 463 12.8 | Feb. 28-June15..} 11.25 27.0 5.0 1906-7. shelter, Oct. 25- Nov. 29. Mansura, La., | 19 cages, great variety 16, 281 20.0 | Feb. 21-June 29..| 10.44 23.0 81.0 1908-9. of shelter, Sept. 28- ies ZAlZ One of the most striking features of Table XLIX is the disparity between the percentage of survival through the six winters considered. A special effort has been made to discover the factors that cause this disparity. Among those that have been considered are the absolute minimum temperature, the daily accumulated degrees below 32 during the hibernation season, the number of times a temperature below 32° was reached, and the rainfall. Contrary to our expecta- tions, it appears that the number of times the temperature descends below 32° has no direct effect. However, there seems to be a direct relation between the absolute minimum temperature and the rainfall, taken together, and the percentage of survival. As the absolute minimum ascends and the rainfall decreases the survival seems to increase. The greatest survival (Mansura, La., 1908-9) was accom- anied by the third highest minimum temperature and the third owest rainfall during the hibernation season. In the same way the next to the highest survival (Victoria, Tex., 1906-7) was accom- anied by the highest absolute minimum temperature and the fourth owest rainfall. Conversely, the lowest survival (Tallulah, La., 1910-11) was accompanied by the lowest absolute minimum tem- perature and the lowest rainfall. The next to the lowest survival (Dallas, Tex., 1907-8) was accompanied by the third lowest absolute minimum temperature and the highest rainfall. It thus appears that a moderately cold winter, with temperature frequently near the zone of fatal temperatures and excessive precipitation, is very unfavor- able for the weevil, but a winter with little precipitation and a tem- erature within the zone of fatal temperatures is by far the most atal. Conversely, a winter with temperatures always above 20° and moderate precipitation is the most favorable for the weevil. 28873°—S. Doc. 305, 62-2——8 114 THE MEXICAN COTTON-BOLL WEEVIL. Certain climatic phenomena are likely to occur which will emph size still more the effects produced by extreme cold and great precipi-— tation. At Tallulah, La., in 1910-11, the early freeze on October 29 cut off the food supply and was followed by warm temperatures in- November which required feeding. The minimum experienced in January completed the control and was low enough to counteract the small precipitation. LONGEVITY OF HIBERNATED WEEVILS. From the beginning of the hibernation experiments in 1905 it has been the custom to place the emerging weevils in rearing jars or cages to determine the average and maximum longevity with and without food. The data obtained have a bearing upon the proper time for planting and upon other practical points. In these experiments 9 295 weevils have been used, as shown in Table L. The fed weevils were furnished cotton squares as soon as they became available. Before that time they were given fresh cotton leaves daily. The unfed series was supplied with water only. Both series were placed in small cages where general conditions closely approaching those in nature were maintained. It should be espera noted that fed weevils show over double the longevity of unfed weevils throughout the season. TaBLeE L.—Longevity of hibernated boll weevils after emergence. Unfed series. | Fed series. l | Place. Longevity. Longevity. Number 6 y Number 5 7 weevils. | \raximum.| Average. | WeeVils- Maximum. | Average. Days. Days. Days Days. Meatcine: ha. (1906. 2222. Ate Lit 412 62 1 fa Bil Beg 8 ee te Meg ees ite & 5 | 735 eee Dallas? Rexs- 1907, 2" 52. - oe 2,179 : 90 12. 50 | 901 | 130 38. 20 Calverts Dex O07 eee eee 1,079 48 8.07 715 118 30. 00 Virtonia ex. \d007 io. int i 1,360 44 8. 20 1,349 86 14.70 Mansura.a-. 1909... so. =. 3. Seren 261 44 11.09 360 36 10. 42 Natchez; Wiss: AI909. th ree 4 19 8.75 | 36 25 12. 20 Manguray slats, | GLO. 28 oe: Sek 175 28 8.78 146 81 36. 50 aU ahesa VOLO ae see ee 179 21 5.70 | 121 105 22.30 Daliwiae Waa Ou ss sk Bo ee 8 12 i220 10 | 25 13.30 Chote! ees 7t tans release ft) Rear iLiteey 3 Pe apt Seg5e [cle oe. Ue Mexia: ores a2 eres eee Bae Be | G07) Siri a 130 | 38. 20 Wreeightediaverage: © ory se He ea aie ee eel | 10. 55 aw accra ecear aoe 24. 20 } It will be noted that the records of longevity of weevils after emergence from hibernation referred to above are based upon speci- mens that had passed the winter in artificial hibernation cages. However, a number of observations have been made upon the lon- gevity of weevils which pass the winter under natural conditions in the field. Forinstance, March 1, 1906, a number of weevils were collected from cotton bolls at Brenham, Tex. These were placed in small cages and observed daily. The last one died on May 31. Naturally the time this weevil was deprived of food the preceding fall is not known, but it must have been prior to December 1, as the frosts had oe HIBERNATION, 115 E _ killed all cotton at Brenham by that date. Assuming that it entered hibernation on December 1, it lived six months without food. In another case weevils collected in the field 7—-MARCH— APRIL -—-MAY— I UNE in the spring at Cal- 40 | vert, Tex., lived with- out food as late as 35 June 8. This gives a duration of life 30 without food of six months and_ twelve “days. Similar ob- %% servations indicate \ clearly that the lon- [20 gevity of weevilsthat pass the winter in IS artificial cages is a roper index to the JO ongevity of those which pass the win- ter in the field. 3 It has become quite apparent from — astu dy of therecords Fia. BET Cue ta eon eS ayerane ave ree ae weevils after that the longevity of | weevils provided with food is considerably greater with weevils emer- ging in June than with those emerging in March, while, on the con- trary, with unfed weevils the longevity decreases with the lateness of emergence. (Table LI.) The diagram (fig. 25) illustrates the above statement graphically. TasLe LI.—Latest dates of death of hibernated boll weevils. Unfed weevils. Weevils fed foliage. | Weevils fed squares. Time of emergence. Mansura, | Tallulah, | Mansura,| Tallulah, | Mansura, | Tallulah, La., 1910. | La., 1910. | La., 1910. | La., 1910.| La., 1910. | La., 1910. IDO OS ASAE Seek ee aera ese Secrest Tut ew 2 TUES See ae PR an Laon | eh Medes ec i Pet Maia ere erence a oe ee ee PAS Pel Seer ACT mrlet aee erceeon enue ieee es sotec mel Savers We rs LG SSE rie Se. So len 4 ee a Atpre 20K Tr Apreel 2) diame 20 se . eS ipyaeaese cIPE Eee. Ste JNTOTE II UGS SS ese ely ees Se eee ee ee ea ASI cou PA Die 2ou | pallye vole SUMO? Qi sree) cbeyaiore, «|e eteee a rtols PACU O SOM SEs Vek Ns ae hone eta wee Es Mayes: |) Mayma2 tuner 28n ume Ste. e eee eene ee be iP? Teo ae So ee Ss 3 Sa eee Nena Leah Fe Wie. PO dibbatsy Te dhblhy sass i Uiblbaialey los Gg sencodc||ogecasecke WWlany IOS sce os Sanet seer Ger and eee semeenee June T2 "i unewloa daly L20) duly- 26" |e eee Sept. 13 AHS NAG ss ees 4 > SEC RCS Ae ee Ia ee (fe ae a June 27 | July 29 | July 7/| July 19| July 1 UMS ISSO s Shoe GESTS 6 sabe OS oe ea ETE ee FRC PSE |e ea | eR Rr PS ee a) I ee Aug. 31 EMDR Seas OMe a eee ise oe ae cigs ae June 12 | June 27 | July 29} July 26] July 19] Sept. 13 MAXIMUM LENGTH OF LIFE. In connection with Table LI it will be noticed that the latest known recorded death of a hibernated weevil is September 13. This fact, taken in conjunction with Table LII, showing the maximum longevity 116 THE MEXICAN COTTON-BOLL WEEVIL. of weevils from the time of entering hibernation to death, is of great interest. The maximum longevity of 335 days, or 11 months, gives proof of the wonderful vitality of the boll weevil. ; ; TasLe LII.—Longevity of hibernated boll weevils from installation to death. Longevity. Place. Condition. Average. | Maximum. Days. Days. Mansura, La.,1910....... 2 5 oe eo SE ae Untied =... =, eee 158 226 allitiah: 1a. 1910. ee ee SAS Keli hepa 2 do_e-.4 yes 169 243 Mansura, La.,1910........------- ee gee tae Ee | Fed foliage.......-.-.. | 206 256 Pallinish ss. o1 Ol Oseme ene ase BRS o- AO pee eased leon +s do. Ae. eee 221 272 Mansura, La., 1910....... eee Soret > | Fed squares........... 257 267 Wallolan: Va 10102. cc oe ees IR» HAE wool (Ss eRaH ro (a ee eeeaes Scher Pe 262 335 RELATION OF EMERGENCE AND LONGEVITY TO TIME OF PLANTING. The data that have been presented show the extreme importance of early planting as a means of averting damage by the boll weevil. Early planting takes advantage of the portion of the season when the weevils are present in the fields in smallest numbers. The longer nlanting is jetereed the greater the number of weevils which will hae emerged. The advantage of an early crop has been shown in many experiments by the Bureau of Entomology and by practical cotton planters. On the other hand, the experience in late plantings has been disastrous. The obvious explanation is in the prolonged period of emergence and the remarkable ability of the weevils to live without food after emergence. This topic will receive additional treatment under the heading of “ Repression.”’ NATURE OF WEEVIL ACTIVITY FOLLOWING EMERGENCE FROM HIBERNATION. In the section dealing with the sprmg movement we have discussed the early search of the weevils for food. There are certain points connected with the spring movements, however, which are intimately related to hibernation, and these will be dealt with here. ‘In following the activity of emerged weevils at Dallas, Tex., certain specimens were marked in such a way as to make it possible to recognize them individually, and the weevils were allowed to remain practically undisturbed in the section where they had spent the winter. In making the daily examinations record was kept of the appearance or disappearance of each individual weevil. No food was supplied in any of the sections until toward the close of the experi- ments in May, when seed was planted and cotton began growing before the last weevils emerged. A majority of the weevils were seen a second time, and some disappeared and reappeared as many as eight times. The longest El | between the first and second appearance of any individual was 43 days. 1 From Bull. 77, Bureau of Entomology, pp. 50, 51. HIBERNATION. a ba lari Taste LIII.—IMtermittent activity of unfed boll weevils after emergence, at Dallas, Tex., 1906. 4 Weevils ‘“rehibernated”— 5 Number of weevils seen— ed Once. Twice. |Three times.) S Bs eee fe Be CO Co age Gre |e ae ec ieee | Sal St gs rs 6 o *s ~~ — peor g — — ovo o o o0' A o o oa ~ 4 q ~ Q . Q . Q 6 ras} s 2 2 5 2 = © a S B = B | & | q Es a ° 12 i A on = 3 = S =) 3 | > o) a i= fy om Rn op) jaa Z A Z AQ vA AQ < 46 26 15 11 | 6 2 2 1 17 8.7 6 ee: 2 OO 6.8 The observations recorded in Table LITT show conclusively that wee- vils may leave their winter quarters during warm days and, failing to find food, they may again become quiet and emerge again after a con- siderable interval. ‘This fact has an important bearing upon the proposition which is frequently advanced by planters of starving the weevils in the spring by deferring the time of planting. While many weevils might perish in this way, 1t is certain that many more would be able to survive and reappear at intervals, so that there would be plenty of weevils to infest the crop, even though this might be planted as late as is possible to secure any yield. Other eee were made upon the intermittent activity of unfed weevils during the spring of 1906. Weevils from Calvert, Vic- toria, and Brenham, Tex., were tested. The weevils from Calvert and Victoria had been confined in hibernation cages throughout the winter. Those from Brenham were collected in the field early in March. None of these weevils had tasted food after emergence. The results are shown in Table LIV. In this table the date of death, unless otherwise indicated, is considered as having been the middle date between the last examination at which a weevil was found alive and that at which it was found dead. TaBLE LIV.—Intermittent actiwity of unfed emerged boll weevils, 1906.1 When . Date of . When When Weevils Locality. é apens put in hi- temoved rehiber- | putin rehi- Bees * | bernation. nennation nated. bernation. as ; 1905 1905 1906 1906 CAV ERG WOK. se has Sete mse Nov. 25 | Nov. 27 | Apr. 19] Apr. 23 20 | May 10 Victoria, Tex Nov 7,13 | Nov. 7,13 \a r 6 | Apr 16 We | ACpr sano. ee comarca aT Tes Deceit Deckumate Wir, oe BE: BE: 1906 (Bromma he Kop saet ae acl eis Nov. 1 eee ae Mar. 1 | Mar. 7 8 | May 11 Average Weevils | Date of | Weeviis | Date of | weevils | Pate of | iength of Locality. SWE VIN |e een oh SUGVLV CD ly neo eie || ASURVIV. Tee ence life in ing. : ing. See ing. ges rehiber- nation. nation. survival. ation : Days. G@alwentsehexee cease eas eat 10 | May 22 6] June 8 0| June 8 30. 4 WiC hOnia ext 5 eM jae ane 3 | May 10 Ores see dilweiie tts May 10 19.1 IB eM AT OX 2 coe ei cts sie 2| May 23 1 | May 31 0 | May 31 67.4 a 1 From Bulletin 77, Bureau of Entomology, p. 52. 118 THE MEXICAN COTTON-BOLL WEEVIL. The records for Calvert and Brenham show a very remarkable ower of endurance in some weevils, the average survival for the two ots of 20 and 8 weevils being over 30 and 60 days, respectively. NATURAL CONTROL. Considerable attention has been given to the study of the natural forces which control the boll weevil. These studies have revealed a large amount of important data, some of which have been used in several bulletins. In the present publication it is possible to give only a summary of the most important results. In general, the natural agencies which control the boll weevil may be classified as climatic (consisting principally of heat which kills directly and also indirectly by rendering the food supply unsuitable, and dryness, the effects of which are intermingled with those of heat), lant resistance, parasites and other insect enemies, diseases, and higds. Each of these agencies will be discussed separately, but a general summarization may be of value. Table LV is a summary of the observations made in the years 1906 to 1909 on weevil stages from many localities. It deals with the mortality of immature stages from all causes exclusive of plant proliferation. TasLte LV.—Annual mortality of immature boll weevils in all classes of cotton forms. 1906-1909. Number stages killed | F etcen ees of mortality by— ue to— pee Total | Total ¥ Year. Bx: stages | stages | amined, | found. | dead. | Cjim- | Preda-| Para- | Al | Clim- | Preda-| Para- ate. tors. sites. | causes.| ate. tors. Sites. 1906.....-..:..-..-| 100,644 | 40,073 | 22,353 | 10,078 | 10,547 | 1,728 | 55.81 | 25.15] 26.31 4.31 eee ee eos | 21,980 | 13,405 | 7,275 | 3,896] 2,263 | 1,116 | 54.27) 29.06) 16.88 8.32 1908 eae ee oe eee 72, 234 | 29,546 | 13,103 | 6,268 | 3,878 | 2,957 | 44.34] 21.21] 13.12 10. 00 POODER Te WUT | 27,857 | 11,653 | 4,863 | 3,012] 1,231 620 | 41.73 | 25.84] 10.56 biz 1906-1909....| 222,715 | 94,677 | 47,594 | 23,254 | 17,919} 6,421 | 50.26 | 24.56] 18.92 6.78 Inasmuch as the material used in making the examinations was derived from many sources and in different proportions each year, a system of weighting the different kinds of material was devised. Table LVI presents a summarization of this weighting in terms of percentages of mortality: TasLe LVI.—Weighted average mortality of the boll weevil, 1906-1909, due to various causes. | | re | Prolifera-| q); Preda- | Parasit- Year. | tion. | Climate.) “tion. sera Total. er Per cent. | Per cent. | Per cent. | Per cent. | Per cent. ROO oe eee AR ec) te ee ey tes ee 12. 42 24. 39 24. 85 2. 94 64. 61 LOOT, 5 isk GL tees ee en 2 ie ee ea ere 12. 42 28. 16 16.18 3. 83 60. 61 ISOS Becca eee Shh, en | ane ee a 12. 42 17. 83 UES 6. 34 48. 37 MOOD hs «oo oe te hon 2 Ac Conon bea tg: oe: Sa | 12. 42 23.01 10. 92 2. 63 48.99 1G06=1909 st A 5S be. ee eee ee eee 12. 42 24. 45 15. 93 3.93 56. 73 ' The average determined in 1906 (see Bull. 59, Bureau of Entomology) is used to apply to other years. NATURAL CONTROL. 119 The extensive series of examinations tabulated above (Table LVI) were made upon immature weevils in all conditions of squares and bolls, the principal of which are known as hanging dry squares, fallen squares, hanging dry bolls, and fallen bolls. The conditions in these four classes of material vary greatly as does the mortality, as is shown in Table LVII. The apparent discrepancy between the totals in Table LVIT and in Table LVI is due to the admission of other minor classes of material in the first table. This table (LVIT) also excludes mortality from plant proliferation. TasBLe LVII.— Mortality of immature boll. weevils in various classes of cotton forms, 1906-1909. Nimmo peuaees Hits Percentages of mortality due to— Total Total | Total y Class of infested forms stages | stages ELIE exam- | found. | dead . : ined. j * | Cli- | Preda-| Para- | All Cli- | Preda-} Para- mate. tors. sites. | causes. | mate. tors. sites. Fallen squares....| 107,293 | 63,985 | 34,403 | 17,596 | 13,958 | 2,849 | 53.76] 27.50} 21.81 4, 45 Hanging squares. . 24,683 | 14,390 | 7,084] 2,543 Aon 21M 49 som l(a Gide uel Daal, 19. 43 Hanging bolls. .-.-- 41,738 | 8,737 | 3,328] 1,709 | 1,054 565 | 38.09 | 19.56} 12.06 6. 47 Fallen bolls. .--.-. 46,200 | 6,825] 2,375} 1,128 | 1,148 99 |} 34.79 | 16.52) 16.80 1. 45 All classes...| 219,914 | 93,937 | 47,190 | 22,976 | 17,905 | 6,309 | 50.23 | 24.45} 19.06 6. 71 Still another extremely important aspect of this large series needs to be shown. ‘This is the geographical differences in the control by climate, predators, and parasites. TasLeE LVIII.— Average mortality of vmmature boll weevils in various classes of cotton forms by States, 1906-1909. Total Stages killed by— Mortality due to— forms | Lotal | Total stages | stages Class of formsand State. exaM- | found. | dead. | Cli- | Preda-| Para-| All Cli- | Preda-| Para- ined. mate. | tors. | sites. | causes.}| mate. | tors. | sites. Fallen squares. ‘Pct pacts PACE jEGh INN ANISA SS See 374 162 62 43 17 2) 38.27] 26.54] 10.49 123 HVOUISIAN Ae eee eee 28,204 | 15,177 | 4,895 | 1,990 | 2,243 DOZE|ozecon palo sl 14.77 3.70 = Mississippieics- essen! 4,216 2, 661 1,070 416 263 391 40. 21 15. 63 9. 88 14.69 Oklahoma ss sees 657 442 238 100 117 21 53. 84 22. 62 26. 47 ANTS Southwest Texas.....-- 3D, 757 1,390 390 186 152 52 28. 06 13. 38 10. 93 3. 74 SowmbhernwVDexass 25.25. | 38, 007 | 25,063 | 16,965 | 8,547 | 7,377 | 1,041 67.68 34.10 29. 43 4.15 IS ASteRe KASH ses eee eee 825 464 248 136 107 53. 44 29.31 23.06 Le OF, Central Mexase se: 14, 879 7, 628 4,233 | 2,386 | 1,602 245 55. 49 31.28 21.00 Sook ' Northeast Texas......- 10,318 6, 497 3,439 | 1,812 | 1,347 280 52.93 27.89 20.73 4.30 North-Central Texas...| 7,066 4, 501 2,863 | 1,980 633 250 63. 60 43.99 14.06 5. 55 Hanging squares. IATHIKANSAS Sek Seo se. 1, 612 1, 144 494 188 60 246 43.18 16. 43 5. 24 21.50 WOUISIANan eee 8, 601 5, 184 2,182 881 651 650 42.09 16.99 12.55 12.53 MASSISSIPDlie= += saeco 784 499 182 41 34 107 36. 47 8. 21 6.81 21.44 Oklghomiake 742. -* 100 63 26 6 One 20 41.27 9. 53 0.00 31.74 Southwest Texas.....-.- 89 46 24 6 2 Gah 521071 13200 4.30 34. 70 Southern Texas......-.- 5, 740 3, 626 1, 937 C2i 496 714 53. 41 20. 04 13. 67 19. 69 astuhexase eee. a. 192 135 | 10 5 1 4 7. 40 3.70 0.74 2.96 Central) Texas: 5-2-2. 2,094 1, 052 703 253 208 242 66. 82 24. 04 19.75 22.98 Northeast Texas.....-- 4,044 1, 667 | 887 290° 211 386 53.80 17.39 12. 66 Pa AUS) North-Central Texas...| 1,-992 1,141 | 766 196 88 492 67.13 U7 (6 Al7/ Cowal 43.12 120 THE MEXICAN COTTON-BOLL WEEVIL, Although the grand total of the examinations shows a higher mor-_ tality due to fallen squares than to hanging squares, it is noticeable © that the mortality in hanging squares is greater in Arkansas, Louisi- ana, southwestern, central, northeastern, and north-central Texas, — and less in Mississippi, Oklahoma, and southern and eastern Texas. As shown in Table LVIII, the highest mortality in fallen squares is 67.68 per cent in southern Texas and the lowest 28.06 per cent in southwestern Texas. In hanging squares the highest mortality is 67.13 per cent in north-central Texas and the lowest, 7.40 per cent, in eastern Texas. Climatic control is highest in fallen squares in north-central Texas, at 43.99 per cent, and lowest in Louisiana, at 13.11 per cent, while in hanging squares it reaches 24.04 per cent only in central Texas and is as low as 3.70 per cent in eastern Texas. Predatory control in fallen squares is highest in southern Texas, at 27.43 per cent, and lowest in Mississippi, at 9.88 per cent, while in hanging squares its highest average is 19.75 per cent in central Texas and its lowest no per cent in Oklahoma. Parasitic Sania in fallen squares is highest in Mississippi, at 14.69 ne cent, and lowest in eastern Texas, at 1.07 per cent. On the other rand, in hanging squares it is highest in north-central Texas, with 43.12 per cent, and tawere in eastern Texas, with 2.96 per cent. In fallen squares it is generally the case that over half of the mor- tality is due to climate, but in Louisiana, Mississippi, Oklahoma, and southwestern Texas insect control is greater than climatic. In hanging squares the insect control is invariably greater than climatic control, and in Mississippi, Oklahoma, and southwestern and north- central Texas parasitic control alone is greater than the climatic plus the predatory control. It was shown in the table comparing the total mortality in all classes of forms (Table LVII) that the weighted average mortality due to insects was 25.77 per cent, as against 24.45 per cent due to climate. All of this evidence is cited to show that in reality the insect enemies produce a very large proportion of the mor- tality of the boll weevil and should therefore be encouraged in every way possible. Of course, it is evident that climatic control is even superior, because of the influences it brings to bear upon every phase of the weevil’s existence. Regional comparisons such as have been made above are of the greatest importance in determining what factors im natural control need to be given the greatest encouragement by cultural expedients or otherwise. CLIMATIC CONTROL. _ From almost every viewpoint the climatic control of the boll weevil is the most ae nae eae this insect experiences. The weevil reacts to a multitude of conditions of temperature and humidity. The time of entrance into hibernation, the length of the hibernation period, the time of emergence from hibernation, the length of the varlous immature stages, the rate of oviposition, and even the pro- portion of sexes are profoundly affected by these agencies. In man cases their effects are not direct. They may affect the weevil indi- rectly through the cotton plant. For example, drought may interfere bie the fruiting of the cotton plant and thus deprive the weevils of OoOd, Bul. 114, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE XIV. NATURAL CONTROL OF THE BOLL WEEVIL. a, Pilose and nonpilose stems of cotton; b, larva of boll weevil crushed by proliferation; c, pupa of Catolaccus incertus on pupa of cotton boll weevil; d, larva of Microbracon mellitor attacking boll-weevil larva; e, /, holes gnawed by Solenopsis geminata in effecting entrance into infested squares. (Original.) NATURAL CONTROL, Ft The most conspicuous illustration of the climatic control of the weevil lies in the failure of the pest to establish itself in the drier pons of Texas. For several years multitudes of weevils have own from the more humid portions of Texas to the west, where the _ climate is drier. In fact, every year there has been a large inflow of weevils into this region. Every season, however, the conditions have _ practically immediately prevented the establishment of the weevil. _ The most important factor has been dryness, but there are others that must be considered. Among them is the fact that there is com- paratively little winter protection for the insect. In addition, an indirect result of small precipitations is the growth of cotton plants of only small size. This results in a small amount of shade and thus augments the direct effect of heat and dryness upon the infested squares which fall to the ground. Frequently the effects of climate act upon the enemies of the boll weevil. This is the case where heat destroys the weevils and their parasites in squares that fall to the ground. In several cases, how- ever, heat increases the effectiveness of the enemies of the weevil. A striking example of this was observed on September 2, 1911, by Mr. J. D. Mitchell, of the Bureau of Entomology. A succession of days in which the temperature was very high and the air exceedingly dry caused the premature opening of many cotton bolls in the vicinity _ of Victoria, Tex. Prior to this time the weevils had destroyed prac- tically all of the squares, and many immature stages were to be found in the bolls thus forced open. In such instances the exposed imma- ture stages of the weevil were subjected to two important destructive agencies. Heat killed many that became exposed to the air, and the ants were able to reach not only those that were exposed, but others inside of the partially opened bolls. If the bolls had not opened, such weevils would have been beyond the reach of the ants. As it was, the climatic conditions not only directly destroyed large num- bers of weevils in a situation where climatic factors rarely affect them, but also greatly increased the effectiveness of another unrelated factor of control. CLIMATIC INFLUENCES ON VITALITY AND ACTIVITIES. In the preceding pages numerous effects of climate upon the devel- opment and activities of the boll weevil have been pointed out, but these must be summarized in order to show how intimately connected the climate is with every phase of the weevil’s life. It appears that the movements of the weevil are sluggish or active in accordance with the nature of the day, cloudy days or low temperatures always causing them to be more sluggish. The number of feeding punctures per square decreases with increases in temperature, and the time before falling of a punctured square also decreases with higher temperatures. In like manner the length of life of the weevil decreases. The age of beginning copulation and the age of beginning oviposition are both increased by decreases in temperature. The activity in oviposition, which is found to begin at 75° F., is greatest in the hottest time of the day, cloudy days causing the oviposition to be less active. The num- ber of eggs per day increases with the temperature and varies for any given temperature with the humidity. The entire period of develop- ment increases as the temperature and atmospheric humidity decrease. 122 THE MEXICAN COTTON-BOLL WEEVIL. The number of generations decreases with the mean temperature and mean humidity. Hibernation seems to begin at mean temperatures between 56° F, and 60° F., but is hastened by high humidity. Cold nights followed by warm, still days seem to stimulate the weevils to considerable activity in the fall, evidently warning them to seek hibernation quar- ters. The period of entrance into hibernation is much more rapid as the mean humidity and mean temperature become lower. The emergence of the weevil is in like manner influenced by the tempera- ture, but it must be considered that the actual temperature experi- enced by the weevil is that which affects the emergence. The time of emergence apparently depends upon an accumulation of a certain amount of effective temperature and a certain amount of rainfall, but if more than the necessary temperature accumulates less rainfall will be needed, and vice versa. The majority of weevils emerge at mean temperatures between 64° F. and 78° F. The percentage of survival seems to decrease as the absolute minimum temperature decreases and the rainfall increases. The foregoing statements are conclusions based in some cases upon more or less fragmentary information, but in other cases they may almost be considered as laws of climatic control. FIELD OBSERVATIONS ON MORTALITY DUE TO HEAT AND DRYNESS. Heat and dryness affect the weevil in a very simple manner. Un- less the square remains moist the food supply becomes unsuitable. In other cases the heat itself causes death directly. Therefore, the hotter and drier the ground upon which the infested square falls, the more certain is the death of the weevil. In the years 1906 to 1909 an exhaustive study was made of the effects of various climatic and other agencies which control the boll weevil. In this work 222,715 cotton forms (including bolls and squares) were collected by agents of the Bureau of Entomology at 65 localities in Texas, 26 in Louisiana, 7 in Oklahoma, 6 in Arkansas, and 6 in Mississippi. Careful laboratory observations were made to deter- mine the mortality due to heat or dryness and to other factors. By reference to the series of general tables (LV—-LVIII) at the beginning of the discussion of natural control it will be noticed that climatic control kills practically one-fourth of the developing stages, the average for the four years in which records were made being 24.56 er cent, which was slightly surpassed by the total insect control. he highest average climatic control was obtained in 1907, being 29.06 per cent, while in 1908 it averaged only 21.21 per cent. In rearranging the data to ascertain the condition in which the control was greatest we find the following results: Fallen squares, 27.50 per cent; hanging dry bolls, 19.56 per cent; hanging dry squares, 17.67 per cent; and fallen bolls, 16.52 per cent. The geographical distribution of climatic control is very interesting. In fallen squares the various sections ranked as follows: North-central Texas, 43.99 per cent; southern Texas, 34.10 per cent; central Texas, 31.28 per cent; eastern Texas, 29.31 per cent; northeastern Texas, 27.89 per cent; Arkansas, 26.54 per cent; Oklahoma, 22.62 per cent; Mississippi, 15.63 per cent; southwestern Texas, 13.38 per cent; Louisiana, 13.11 per cent. NATURAL CONTROL. 123 In hanging squares we find a somewhat different arrangement of | the sections: Central Texas, 24.04 per cent; southern Texas, 20.04 | per cent; northeastern Texas, 17.39 per cent; north-central Texas, _ 17.17 per cent; Louisiana, 16.99 per cent; Arkansas, 16.43 per cent; southwestern Texas, 13 per cent; Oklahoma, 9.53 per cent; Mississippi, 8.21 per cent; and eastern Texas, 3.70 per cent. In many of the records made during 1906 it became evident that certai cultural practices greatly favored the amount of control by heat and dryness. The wider the rows, the greater the amount of sunlight which strikes the ground. Consequently the fields with wide rows or in which the stand was imperfect showed the greatest mor- tality. In a similar way, fields in which were varieties with compara- tively small amounts of leafage showed greater mortality due to heat and dryness. It did not become apparent, however, from the obser- vations made, that the direction in which the rows ran made any material difference in the mortality. The difference between the various sections in the mortality in fallen squares is especially conspicuous. This is due undoubtedly primarily to the greater precipitation in the sections with low mor- tality, which, by keeping the ground more or less moist, prevents such temperatures at the surface as are frequently reached in Texas. The greater rainfall in Louisiana also undoubtedly has an indirect effect. In that State the additional rainfall causes the cotton plants to grow to a large size and to shade the ground more than is the case in ‘Texas, thus preventing the sun from reaching the squares on the eround. The differences in hanging squares are not quite so con- spicuous, but are probably due to some extent to atmospheric humid- ity, density of foliage, and other similar factors. Equally interesting results were obtained in 1906 with reference to the effect of heat and dryness upon the different stages of the boll weevil. It was found that the mortality in the larval stage amounted to 52 per cent, in the pupal stage to 18 De cent, and in the adult stage to 6 percent. Nearly 70 per cent of all the mortality caused by heat and dryness occurs; therefore, during the larval stage. Table LIX illustrates the percentage of stages killed during the warm months of the year by high temperatures and is based upon all of the examinations made during the years 1906 to 1909, inclusive. TaBLeE LIX.—Weighted average heat control of immature stages of the boll weevil, by months, Texas, Louisiana, Oklahoma, Arkansas, and Mississippvr. Per cent Forms Stages | killed by Month. Secalt found. | heat and i drying. IMENT 5 Ghebe Soc See tes Se 8 TENS ee ee RARE eset eS Dee Na e e 100 56 7.20 HUI soane Shouts ls oS AES Re eee Sie emai eS oe pe ee en Ce ed 16,930 10, 708 28.33 Ligeia BST D0 TST aie iia Degen ie neil ee et Rote 43,059 | 21,758 25.61 AO RTEBSG Sa 5 SEIS SSO R ES O Re eee a de, Spee ere A Neen AB Ana eRe ge Hoist rr Bee 80, 923 33,170 24. 62 SNC] DSITA| OTP Ss oe Soe i a es ne 37,378 17,107 22.87 October--) 22. SE cect ager tS eo al hae Dae 17,344 8, 283 16.59 TORE Ss xis ey SSS Am SES Oe eS es ee Ra ee he ea en 195,734 91, 082 23.80 Many illustrations are available to show the powerful effect of heat and dryness in the reduction in the numbers of boll weevils in cotton fields. The action of this agency is so powerful that it may check the 124 THE MEXICAN COTTON-BOLL WEEVIL. weevils in a single season so that a crop may be obtained. This was shown in a field which was under observation in Victoria County, Tex., in 1906. It was found in April that a very large number of hibernated weevils appeared in the field. This month was reasonabl moist, so that the cotton germinated promptly and made a quic growth. The month of May, however, showed a decided deficiency in precipitation, being more than 3 inches below the normal for the month. This checked the weevil at the time the first infested squares began to drop. The control continued during the month of June, which also showed 3 inches less than the normal rainfall. These conditions resulted in such a checking of the weevils by June that the cotton plants were able to put on a large number of squares. The month of July showed a precipitation above the normal, which caused the plants to grow rapidly. The setback experienced by the weevils, however, during the preceding dry period was so great that they were unable to overtake the production of fruit, so that a yield of about one-fourth of a bale per acre was obtained. Examples of such complete control within a single season are not common. It frequently Wan ens that a drought continues so long that the plants are es affected. In general, however, the lants can recover more rapidly from a drought than the weevil. This results in an advantage to the crop from even a short drought. Of course the advantage becomes greater as the drought is prolonged, provided it is not prolonged to a point where it seriously affects the growth of the plants. Examples of the control of the weevil in one season from heat and dryness of the preceding season are common. Table LX shows a striking instance of this kind. It will be.seen that the effects of the drought of 1902 extended into the following season and brought about a marked increase in production. By the follow- ing year (1904) the recovery of the weevils from the drought of 1902 was indicated by a decreased production of cotton. | Taste LX.—General illustration of drought control of the boll weevil, Nueces County? Tex., 1901-1904. Rainfall. Ab . ainfa emperature Cotton produc- : > tion Annual. Mar. 1-Aug. 31. Annual. Mar. 1-Aug. 31. Nueces rn. a : County Year. equiva- Depar- Depar- Depar-| jentin Mean ture Mean ture Mean | ture 500- aver- from aver- from aver- | from pound age. nor- age. nor- age. nor- bales. mal. mal. mal. Inches. | Inches. | Inches.| Inches. ot: Yn 1900 ec oe ee ee 17.49} —11.90 6. 745\0 17242 76.2 | +0.83 601 190222 oe ee PPP) A MATT B57. | aan 77.3 | +1.85 480 10032 oe eee er FU 36.92] + 6.72] 25.97] +11.38 74.5] — .9 4,099 1004.8 ae ee be 28.54| — 1.66] 13.56] + .83 76.0] + .5 1,556 NATURAL CONTROL. 125 GENERAL DISCUSSION OF THE RELATIONS OF TEMPERATURE TO THE BOLL WEEVIL. Our studies of the boll weevil lead us to the conclusion that there is a certain degree of temperature above which, under any condition of humidity, no individuals can exist even for a limited time. This point is known as the maximum fatal temperature. Below this there Is a zone of varying width of temperatures which may be fatal in cases of long exposure or under certain conditions of humidity or insect vitality. This may be known as the upper zone of fatal tem- peratures. Below the zone of fatal temperatures is a zone of tem- peratures which, when continuing for any length of time, force the insects to shelter. This zone may therefore be fitly called the zone of zstwation, and it must be understood that the relative humidity will have a strong influence in moving this zone upward or downward, according to regional conditions. This zone is aed by the point at which effective temperature ceases. Below this point is the zone of actwity. In this zone will be found the degree of effective tem- perature, a long continuance of which is necessary to draw the insects out of hibernation. This is not an absolutely fixed point, for it varies with humidity. Possibly the relation could be stated in a definite formula if a sufficient amount of data was available. The temperature which causes activity is usually known as the zero of effective temperature. It is assumed that active metabolism begins at this point and that a certain amount of effective tempera- tures accumulated in daily units is necessary to bring about a given transformation or function. This sum is known as the total effective temperature for any given function. It will vary in accordance with the humidity. Below the zero of effective temperature there will be no necessity of feeding, and locomotion rapidly becomes impossi- ble. On the approach of the zero of effective temperature the insects will display considerable activity in finding winter quarters. We therefore designate the zone below this zero as the zone of hiber- nation. The lower limit of this zone is the highest temperature which may be fatal under certain conditions of humidity or pie alternation of temperatures. Below this point occurs a more or less restricted lower zone of fatal temperatures. The lowest point at which life can exist is known as the minimum fatal temperature. 1 Of course the manifestation of the absolute temperature which draws the weevils out of hibernation is dependent upon the density of shelter. Certain forms of shelter prevent the weevils from being affected until long after the outside air has been sufficiently warm to cause activity. 126 THE MEXICAN COTTON-BOLL WEEVIL. These zones are illustrated in the accompanying diagram (fig. 26). UPPER ZONE OF FATAL TEMPERATURE. Numerous experiments have been conducted in dropping adult boll weevils upon the soil at different temperatures to determine the effects upon the insect. MAXIMUM FATAL TEMPERATURE In this work 119 tests were made at soil tem- peratures varying from UPPER ZONE OF FATAL TEMPERATURES 110° to 140° F. Below | 122° F. none of the wee- fe vils were killed, but from 122° F. upward death re- sulted in times varying from 1 second to 900 ZONE OF AESTIATION seconds. In a general way the exposure neces- sary to cause death de- creased as the tempera- tures became higher. From these experiments we conclude that the upper zone of fatal tem- perature for the adult boll weevil may be con- ZONE OF ACTIVITY. sidered as from 122° to eee In the series of exper- iments to which refer- ence has been made a <— £000 1S REQUIRED ABOVE THIS POINT Ba Sen PATA STS <—ZLRO OF LFFECTWE TEMPERATURE were made upon humid- ity. The atmospheric humidity during the time <“7AL TEMPERATURE FoR E665 AND YoUNG LAkvae =the experiments were “under way, however, was rather constant, ranging from 37 per cent to 40 per cent. Within this narrow range it was not determined that humid- | ; ity either decreased or 140 “\ S MURMUUREE MMRRU ORES MUR O ROR ED PUURROOUU RUURHUUEEO RURRERUROR UOREORGED 8 S Sy LDEGALES FAHPLENMAEL T S fo OF HIBERNATION FOR IMMATURE STAGES 8 TR CR ROR RL ZONE OF HIBERNATION FOR ADULTS 20 increased the length of LOWER ZONE OF FATAL TEMPERATURES time necessary to ealse the death at any fixed <—MINIKIUWE FATAL TEMPERATURE temperature. It is interesting to note that the zone of 2 fatal temperature for ‘IG. 26.—Diagram to illustrate the zones of temperature in their > +] thi relations to the activities of the ball weaver (Onsite) adult weev ils W hich fall to the ground will be reached under general conditions when the temperature recorded at the usual distance above ground at which thermometers are placed reaches 95° F. /0 NATURAL CONTROL. 19% ZONE OF ZSTIVATION. During 1906 and 1907, in southern Texas, Mr. J. D. Mitchell ob- served that many adult weevils were on the ground near the cotton stalks under clods of earth and dead leaves, seeking protection from the intense heat. This indicates a distinct zone of estivation, although such temperatures may exist only for a few hours at a time. The exact limitations of this zone are undeterminable. » Astivation is a very common habit among weevils. As throwing some light on the probable action of the boll weevil under high tem- peratures, it is of mterest to state that Prof. C. H. T. Townsend, of Piura, Peru, finds that the Peruvian cotton square borer, Antho- nomus vestitus Boheman, estivates during the hot months in the fallen squares both as pupa and adult, but remains practically Inactive. ZONE OF ACTIVITY. | The temperatures at which most of the functions of the boll weevil | are exercised lie between the means of 91° F. and 56° F. It is prob- | able, however, that this zone approaches very close to the zone of fatal temperatures. In the spring effective temperature '! begins to accu- mulate at approximately 56 degrees, but the total necessary to bring the weevils out of hibernation may be low if the rainfall and humidity for the same period are high, and it must be correspondingly high if the humidity is low.2. When the two factors have accumulated enough between them they bring about emergence. It is roughly calculated that 172° of effective temperature and 5.1 inches of rain are necessary. A deficiency of effective temperature must be balanced by additional rainfall; a deficiency of rainfall must be balanced by additional effec- tive temperature. For a fuller discussion of this subject see the section on emergence from hibernation (p. 107). When the weevils have emerged and found food they require a cer- tain number of days of feeding before oviposition can take place. This preoviposition period for hibernating weevils and for the succeed- ing generations is determined largely by temperature and humidity. As these two factors decrease the period increases. In like manner we have shown on preceding pages how the egg and larval and pupal stages are governed by the same laws. We have also shown that even _ the daily rate of oviposition is accelerated by increases in temperature and probably also of humidity. The common impression that ‘‘rain brings the weevils’’ has its basis in the natural increase in the numbers of weevils shortly after a rainy period, due somewhat to the fact that increased humidity reduces the developmental period. A more important factor, however, is that humidity reduces the effects of sunshine in killing the weevil stages. ZONE OF HIBERNATION. The behavior of the weevils in hibernation is fully discussed else- where. In ice-box experiments at 45° F.it was found that the weevils would not emerge, but Dr. W. E. Hinds found that 10 weevils which had emerged: from hibernation and which were confined 303 weevil 1 That is, the temperature at which activity begins. ‘ : 2 In a former publication (Bull. No. 51) we adopted the assumption made by other writers that 43° F. is the general zero of effective temperature for insects. Recent experiments have shown conclusively that this is an error, so far as the boli weevil is concerned. 128 THE MEXICAN COTTON-BOLL WEEVIL. days at 44° to 45° F. made 36 feeding puncte or at the rate of one puncture every 8.4 days. It is probable that these punctures were all — made possible by the removals from refrigeration for examination. LOWER ZONE OF FATAL TEMPERATURES. In 1904 Dr. W. E. Hinds conducted experiments in the effects of low temperature on eggs and young larve. He found that 34 eggs at 45° F. for 13 to 14 days did not hatch when kept later at a temper- ature of 69° to 70° F. Recently hatched larve, however, were killed by nine days’ exposure to 45° F. By experiments conducted with adults in 1905 it was ascertained that 32° P. was not fatal; 24° F. benumbed the weevils, but they could revive; 18° F. killed. ; In experiments conducted by Mr. H. P. Wood 32 weevils were exposed to a minimum of 15° F. and an average temperature of 18.6° F. for seven and one-fourth hours and then iploved in the refrigerator at a higher temperature, but none recovered. In similar experiments Mr. W. A. Hooker exposed 11 weevils for six hours to temperatures varying from 15° to 20° F. The weevils were quiet, but later showed signs of life, although they died within two days. Between 7 and 10 degrees, five weevils were killed in six hours. One degree below zero was absolutely fatal. Observations on the effects of low temperatures upon the weevils in the fields leads to the statement that all places experiencing a tem- perature under 12° F. in the early part of the winter will profit by an almost complete extinction of the weevil, depending somewhat, of course, upon the amount of protection the weevils may have secured before the freeze. Regions having a normal minimum temperature of zero need have little fear of serious continued depredations from the weevil until the insect has proved itself able to adapt itself to colder temperatures than it is now able to withstand. In this connection it will be of interest to submit Table LXI, giving the pee? winter mortality from cold since the beginning of our records. TABLE LXI.— Weighted average cold control of immature stages of the boll weevil, by months. a} Killed by Month. OSS paeee cold and 7 * | wetting. a — SOE d,s. I@IK:._ 50s Fata i) Saas Per cent. JATUBIY 2 ees oc hn baw so doe ain Soe oe oe eee ek ee ee 5, 687 1,285 36. 42 Kebruaryce 2s ere ok bot SRS ee ee ee 13, 597 665 67.36 Marchige. ct eats ee el. Re ee eae sees Se ae 2,500 159 31. 44 NOVeMDers cas os nce coe oe en ES a es Cee ee 2,534 798 41. 40 December. sees cs ses cies Se ee oe ee 2,663 38. 37 Dotal cs - oo cijoc acne annoetdannr ee a eS eee | 26,981 | 3,595 44. 61 It should be noticed that winter cold is, on the average, almost twice as effective as summer heat. The history of the boll weevil furnishes several examples of winter control, principal among which are the early freezes of November, 1907, November, 1908, and December, 1909, which greatly reduced weevil damage in large sections. NATURAL CONTROL. 129 FATAL VARIATIONS OF TEMPERATURE. _ It has long been known that one of the most potent forces in insect _ control is abnormal variation of temperature. Probably no stronger illustration of such control could be produced than that afforded by : the conditions of the winter of 1910-11. See beled - Pea Oe vale a ane -- -- meee kl =. a Re da wat ee J e---\ MISS. ‘ woo er’ mee een wee eee Fic. 27.—Map showing dates of first killing frost in the area infested by the boll weevil,in the winter of 1909-10. (Original.) ee : = =. ee er =n. 4- (After Fig. 28.—Map showing normal dates of first killing frost in the southern United States. i Weather Bureau Bulletin V.) On October 29 to 30, 1910, a freeze occurred throughout the cotton belt affecting all but a narrow strip of territory along the Gulf coast and two small interior areas of Texas, as illustrated by the accom- panying map (fig. 27). Another map (fig. 28) is presented to show 28873°—S. Doc. 305, 62-2——-9 on 130 THE MEXICAN COTTON-BOLL WEEVIL. the normal dates of the first killing frosts. Comparison of these two | maps will show at a glance that the first killing freeze of 1910 was over a month earlier than the normal. Such a natural phenomenon is an exact equivalent of artificial fall destruction at the same date. The temperatures were not fatal to the weevils, but were such as to force hibernation and at the same time cut off food supply. If tem- peratures compelling hiber- nation had continued, the weevils would haveemergep in about the same propor- tion as would be expected if they were artificially de- prived of food on the same date. However, another climatic factor intervened. Almost the entire month of November was warm, and throughout Louisiana, at least, the mean temperature oi * stood at above56° F. for the Fic. 20-Msp showing minimum temperatures on Octo- Tonth We have already Louisiana. (Original.) shown that a continuance of mean temperatures over 56° F. will force the weevils to take food, and that in the absence of food at effective temperatures starvation occurs in a few days. If all of the cotton had been killed by the freeze, the control would have been complete, but there are al- aX lullsides or near buildings severe freezes, and these Ne areas no doubt harbored Ra many weevils until the cold wave of November 29 drove them to a normal hibernation. Inthe map (fig. 29) show- ing the Louisiana minimum temperatures of October 29 and* 30, 1910, on which dates the first killing frost occurred, it will be noticed that no fatal temperature was reached, but that a freezing temperature oc- Lae pe curred in practically all of ae aC ay teeta Lag tere a (oat by ere the cotton-producing terri- tory. The other map (fig. 30) illustrates the minimum temperatures of the entire winter of 1910-11 and shows that fatal temperatures (7° F. to 22° F.) occurred throughout the State. These minima ways sheltered areas on that escape two or three ‘ee NATURAL CONTROL. | 35) ~ occurred, however, early in January, at which time all weevils which had survived the starvation of the fall were deeply hidden in hiber- ee shelters, where sudden changes of temperature have little effect. The survival from hibernation at Tallulah, La., was only one-half of 1 per cent, as shown in the hibernation statistics, and this, no doubt, must be attributed to the rare combination of early freeze, subsequent long duration of effective temperatures without food, and finally a period of minimum fatal temperatures. One of the most interesting features of the fall of 1910 in Texas was the presence of two small areas in which the first freeze was delayed from one to two months. (Fig. 27.) We call attention to the most interesting of these cases. The freeze of October 29 was felt in all Texas above the latitude of 31°, except in Erath, part of Comanche, part of Brown, Eastland, Callahan, Taylor, Jones, and Haskell Coun- ties in central-west Texas. In this frost-free area in the following October, 1911, a very heavy infestation was found at Cisco, in Kast- land County, and at Brownwood, in Brown County. The infestation diminished in every direction from those places. At Lampasas, 60 miles southeast of Brownwood, where we would naturally expect a much higher infestation than at Cisco, very shght damage occurred, and at Granbury, in Hood County, 60 miles east of Cisco, where the weevils have been present since 1904, they were extremely difficult to find. Thus, it is seen that a territory which had had the weevil much longer than either Brownwood or Cisco had fewer weevils in 1911, because it experienced an earlier killing frost. EFFECTS OF FLOODING UPON THE WEEVIL. Tests at Victoria, Tex., in 1904, were divided into two parts, each of which included both the immature and mature stages. In each part floating and submergence were tested. In the tests made upon the floating power of adults, weevils were isolated and placed in water in tumblers. They were dropped from a considerable distance above the surface, so that they became entirely submerged, and they rose to the surface naturally. The surface tension of the water was found to be sufficient to float weevils which were placed upon it carefully. The generally hairy condition of the surface of the weevil’s body prevents it from being readily wetted, so that it may struggle for some time in the water without becoming really wet. When dropped, as described above, weevils float head downward, with the tip of the abdomen above the surface. In the submergence tests weevils were held down by a wire screen, and all bubbles were removed from their bodies by a pipette, thus making the tests as severe as possible. Sixty squares believed from external examination to be infested were floated in a driving rain for six hours. They were then removed and left for several days, during which time 75 per cent of them pro- duced normal adults. Ten squares which were floated in driving rain for six hours were opened at once, and in every case found to be only slightly moist on the inside. These contained six larve and four pup, and all were in Tage condition. As squares float normally, submergence tests were considered extreme. Five squares were submerged for six hours, and after that produced three normal adults; one pupa died, and one square was found .¥ 132 THE MEXICAN COTTON-BOLL WEEVIL. to have been uninfested. Five more squares were submerged for 31 hours. These produced two normal adults, and one ware died in the process of molting after removal from the square. Death was prob- ably caused in the last case by drying; one square was found to contain a dead pupa, and one was not infested. To test the possibility of its living, should the square be penetrated by water, a naked pupa was submerged for six hours, but in spite of this unusual treatment it pro- duced a normal adult. Numerous larve removed from squares and placed in water pupated in one or two days, and several pup remained alive, though floating for several days in water before they transformed into adults. In the case of squares floating normally it is evident that they might remain in water for several days without injury to the weevil within. Very slight wetting of the cell takes place, even under the extreme conditions of submergence. The effect of a brief flood would not, therefore, be at all injurious. As adults float as readily as do squares, they may also be carried long distances, and, further- more, they are able to crawl out of the water upon any bushes, weeds, or rubbish which they touch. Even when floating for several days continuously they are able to live and may be carried directly to new fields. The floating of adults and infested squares explains the appearance of weevils in great numbers along high-water lines immediately after a flood. Field observations were made to supplement the laboratory experi- ments recorded in the preceding paragraphs. In July, 1904, many fields in the vicinity of Victoria, Tex., were partially and some wholly submerged. This condition lasted for several days. Examination made after the recession of the water showed that many fallen squares which had been in the water for some time contained unin- jured larve and pupe. Naturally, eggs and larve found in squares upon the plants, even though under water for some time, escaped unharmed. Weevils were working normally upon the plants. No diminution in their numbers could be seen, and it was apparent that the overflow caused no check either to the development of the imma- ture stages or to the activity of the adults. PLANT CONTROL. While climate is the foremost factor in the control of the boll weevil and also of the behavior of the cotton plant, there are certain kinds of control which the plant itself exerts. One of the most important of these is proliferation, which will be discussed in the fol- lowing paragraphs. PROLIFERATION. Zarly in the investigation of the boll weevil it was noticed that the immature stages and sometimes even the adults are frequently killed by a form of reaction of the plant known as proliferation.1 It appears that this property of the plant might be emphasized by breeders. For this reason special studies were conducted in 1905 1 Dr. O. F. Cook, of the Bureau of Plant Industry, has published a number of papers in which references are made to proliferation. The reader is referred to these papers, which are included in the bibliography at the end of this bulletin, for a full discussion of the botanical aspects of the phenomenon. NATURAL CONTROL. 133 and 1906. The results were published in Bulletin 59 of the Bureau of Entomology from which the following statements are abstracted. | For the present purposes proliferation may be defined as the devel- — opment of numerous cells from the parts of the bud or boll of the — cotton plant which are injured by the weevil. It is clearly a mani- _ festation of an inherent tendency on the part of the plant to counter- act irritation by the growth of large numbers of new cells. This growth usually begins in the layer of cells adjoining the lining of the boll or in the staminal column of the undeveloped bloom. Part of | the formation may project through the rupture made by the weevil - or may form a hemispherical mass protruding from the inner side of the carpel of the boll and pressing into the lock. The reaction on the part of the plant begins generally before the egg hatches. In some cases the egg itself may be moved a considerable distance by the erowth. In other instances the egg becomes enveloped and the larva — emerges in the proliferous mass. Under such circumstances it may be destroyed early in life, although it often makes its way through the mass into portions of the fruit which have not been affected. As the larva feeds it continues and increases the irritation, and the response of the plant is immediate. In this way it often happens that the space the larva has eaten out becomes filled by the proliferous mass, and the pressure becomes so strong that eventually the larva or the resulting pupa or adult is crushed. It is clear from the observa- tions made that it is this crushing effect that destroys the weevil. (See Pl. XIV, 6.) A number of experiments in which weevil larve were placed in proliferous tissues showed that they could develop normally upon this modification of their natural food. The frequency of the occurrence of proliferation was determined by the examination of 1,870 squares and 2,042 bolls of a large number of American and several foreign cottons. In the case of squares, it was found that in the averages for all seasons and localities proliferous growth followed feeding punctures in 48 per cent of the cases. The highest percentage, 75, was in the case of the Jannovitch, an Egyptian variety. Inthe case of bolls, proliferation followed in 81 per cent of . the cases of feeding punctures. It is consequently apparent that proliferation occurs more frequently as a result of feeding punctures in bolls than in the case of punctures in squares. No very satisfactory results followed a study of the effect of climatic conditions upon the frequency with which proliferation follows the attack. of the weevil. The observations included a number of varieties growing in two localities during two seasons, but there seems to be no special relation between the locality and the season and the number of cases in which proliferation was found. In fact, the maximum percentage of formation of proliferation in bolls and the minimum in squares occurred at the same time in the same locality and with the same variety. Table LXII shows the weevil mortality due to proliferation in squares and bolls under natural conditions. 134 THE MEXICAN COTTON-BOLL WEEVIL. Taste LXII.—Summary of observations showing increased mortality of the boll w in squares and bolls caused by proliferation. iat Me Soar? Mortality | 2 Mortality | 3 , | a Squares examined. in squares. a8 Locks examined. ti ake’ =8 3 2 bo F ie = = ~ = Oo Ko) CO as > = | - Sq Ss be | © Es = : Sq a a o } eS observa-| 5 |} 2 s =solso/& =. = = = =o] ss = =. = tims. |2 | 5 | g | FS |EB|S./9s/S8] B15 (Fs) Fela. | eg | ae 3/3| 3 | 58/88/88 |88lecl 8 |] ah 155 )e8165)] se] Be S\e| = | 48/88) 53| 88/22] 2 | 2 | 28 | ss | 2S] se)2= 3.1 Sasi wes Fe lne|/8° 1/85/58) a] Eci.nels SSisés 5\/a © Ha logis en = ° °° Alon ls ee peng = = Lm = = S rs |e aa) eS Zi ew = = = | P.ct.| P.ct.| P.ct.| gee oie (a et | Piet 1902... 4] 4 105 44 | 41,9.) 3035)) 19554) U0 see See 1 ee ee Paes CS ia te ly a Ee, eR pee, beak ig Sek a) ce ay SF || 246] 1,033 | 434] 42.0] 15.0] 5.0] 10.0 Tae | i Mee, Pa pCise. Syacih sagt (ies CEOS GS & || 45211,898| 995 | 52.4] 28.4]12.8] 15.6 1904.....| 1] 9 | 2,954 / 1,480] 50.0] 9.6 Ae AL | enn os een elles SE BR Se Pets Sek. 1904... 2 | 2h eer ae 15 val SEN ADS 2 ae |} 398] 1,708 | 885] 51.8|18.2] 11.1] 7.1 1905.....). 2 |14.| 4,504 | 2,365 |.52.5:1-09.60), 5.5.) 14. Ll ce le ee le ee ee 1905.....| 1 | 6° 771 | 372] 48.2128.6]° Basis Wo tcc ng ee eae lf 1905.....| 1] 1| 443) 212 | 47.9 | 25.1] 9.7 154:| [ile Ee een eek eee GeSred beter es 1905.....| 1] 4 144) 40 | 97.8.1.348'|, 3:2 130 elew®: ee ine rer a ie 5 PASC ee 1905... -.. Con 2) era ee Hesent sd Pee ee eee EES 11,802 | 7,821 |5,069 | 64.8/ 16.7] 85] 82 "(Napa | bee Oe ih Rican (ARS ea Pear 6 hak ae See | 82] 254] 158] 62.2)146| .0| 14.6 Totals | | | | and av- erages..|....|...-| 8,921 | 4,513 |250.6 [217.2 |23.7 [213.5 ||2,980 |12, 714 ee 259.3 pases 79.2 26.3 | | 1 From Bulletin 59. Bureau of Entomology, p. 27. 2 Weighted average. It will be seen that in the case of squares there was a range of from 9 to 31 per cent increase in the mortality due to proliferation, the eneral average being 13 per cent. In bolls the range is not so great, one only from 7 to 15 per cent, while the average increase in mor- tality in bolls was found to be 6 per cent. This is slightly less than one-half as great a mortality as was found to be the case in squares. A number of interesting experiments were performed to determine whether artificial punctures were as frequently followed by prolifer- ation as those made by the weevil. One thousand one hundred and three needle punctures were made, resulting in proliferation in 36 per cent of the cases. This percentage is not so large as in the case of feed- ing punctures of the weevil, but 1t is as large as could be expected when the difference between acleanneedlepuncture and the rough, lacerating puncture by the weevil is considered. It consequently appears that it is the mechanical injury of the weevil rather than any secretion which causes the growth. Bop WC , tA Le no 1) 142 THE MEXICAN COTTON-BOLL WEEVIL. Lariophagus texanus Crawford (Pl. XVIII, a).—There is strong evidence that this species is a primary parasite of the boll weevil in — southern Texas. It is also undoubtedly a parasite of four other species of weevils. EULOPHID#. Tetrastichus hunteri Crawford (Pl. XVIII, 6, c).—This parasite of the boll weevil has been known only since 1908. It is the only internal hymenopterous parasite of the weevil and occurs commonl in Louisiana and Mississippi and has been recorded from Texas. tt is evidently more important in the fall of the year. ICHNEUMONIDEA. ICHNEUMONID#. Pimpla sp.—On February 23, 1909, a single female of this species was reared from a weevil larva collected at Nacogdoches, Tex., on January 27. BRACONID#. Sigalphus curculions Fitch.—This common parasite of the plum curculio has been found frequently attacking the boll weevil in Louisiana and Mississippi. It is known as a parasite of eight other species of weevils. Urosigalphus anthonoma Crawford.—This species has been reared from the boll weevil only at Brownsville, Tex. Urosigalphus schwarz Crawford.—This species is a parasite of the boll weevil in Guatemala and has never been reared in the United States. Urosigalphus sp.—A single specimen of this species was reared in 1909 at Arlington, Tex. Microbracon mellitor Say. —Until 1909 this was the most important parasite of the boll weevil. It is coextensive in distribution with its host, but is by far most important in Texas and Oklahoma. It is known as a parasite of 10 other species of weevils. An unknown braconid, nearly related to Glyptocolastes, was reared from the boll weevil in southern Texas. DIPTERA. PHORIDA. Aphiochxta ngriceps Loew. Aphiocheta fasciata Fallen. Aphiocheta pygmexa Zetterstedt. These three species and also possibly others in this genus have fre- quently been found feeding upon boll-weevil larvee and in many cases under such circumstances that they must be assumed to be parasites as well as scavengers. TACHINID. Myiophasia «nea Wiedemann.—This fly has been recorded as a parasite of the boll weevil in Texas. It is also an enemy of six other species of weevils. _ Ennyomma globosa Townsend (Pl. XVIII, d, e).—This fly is an important parasite of the boll weevil in Louisiana. It also attacks the cowpea curculio. NATURAL CONTROL. 143 | Careful studies have proved that the 29 species of parasites are all | derived from native hosts, which are mainly weevils breeding in | weeds and other plants growing normally around the cotton fields. | Some of these parasites have lived for many generations on certain | common weevils until suddenly some abnormal condition has deci- ' mated the numbers of the normal hosts or freed the parasites of their normal control, thus upsetting the natura] equilibrium between them and their hosts. In this way the parasites have been compelled to seek new hosts, and the presence of the boll weevil in large numbers has led them to attack it. This has been demonstrated by the sudden adaptation of several species of parasites at Victoria, Tex. These were normally enemies of the huisache pod weevil, but were unable to attack this insect in 1907 because of the failure of the hui- sache trees to fruit. Another demonstration of sudden adaptation was found in the sudden increase of attack by Hurytoma tylodermatis following the cutting of a number of weeds in which this parasite was attacking a native weevil. Such adaptability of course suggests the advisability of keeping the weeds in the vicinity of cotton fields cut down during the summer in order to force the parasites to attack the _ boll weevil. | After a parasite has once attacked a new host it becomes com- paratively easy for succeeding generations to repeat the attack. In this manner many species of weevil parasites have increased their range of hosts until they have obtained a complete series extending throughout the year. A rotation of hosts has, therefore, been estab- lished. As many as 17 different weevils are attacked by one of the species of boll-weevil parasites. To illustrate the value of this rota- tion we have but to quote one of the commonest examples. The strawberry and blackberry bud weevil is very common in the South in the latter half of March and until June. Two of the species of the boll-weevil parasites attack this weevil as soon as it begins to breed, and they are able to develop at least one generation before the boll weevil can begin its attack on the cotton squares. These parasites are found attacking the boll weevil throughout the summer. In the fall they begin to attack certain stem weevils, such as the potato or Solanum stem weevils, and produce a generation during the winter which emerges in time to attack the strawberry weevil. Thus, two generations are developed while the boll weevil is in hibernation. To obtain a practical benefit from this rotation of hosts it is only neces- sary to have a hedge of dewberries or blackberries along the fences. It is of extreme importance to know that no matter what exigencies reduce the boll weevils, the parasites, though also reduced in numbers, will still be conserved on their native hosts and will attack the boll weevils again as soon as they become sufficiéntly numerous. The location of the developing stages of the weevil is of much importance to the insect enemies. (See Pl. XV.) It has been found that cotton varieties display two distinct tendencies in their response to injury to their fruit. Certain varieties, such as King, Simpkins, and Shine, are distinguished by a transverse ring at the base of the pedicel of the square and boll. When the square or boll is badly injured, the plant immediately cuts off circulation by forming a corky layer at this ring, and the injured member falls to the ground. Other varieties, such as Dickson, Rublee, and in general the cluster 144 THE MEXICAN COTTON-BOLL WEEVIL. and semicluster types, are distinguished by an elliptical mark which encircles the pedicel, but extends down the stem for one-half to a whole inch or more, and is usually incomplete at the lower end. When such a square is injured, the corky layer is of course diagonal, extending downward on the stem, but usually incomplete, so that — the injured member adheres by a thread of bark and dries on the plant. A very extended series of observations has definitely proved that the hanging dry infested square is the most favorable place for parasitic control and that the total control of the weevil by all causes increases in proportion to the number of these hanging dry infested squares. A proper selection of varieties is, therefore, a practical method of increasing control. On the other hand, it must be understood that insect control of the stages in fallen squares is often very high. Certain parasites and all of the ants and predatory beetles are more likely to find the immature weevils in the soft moistened or dried fallen squares than in the dry hanging squares. ‘Thus the developing weevil has enemies wherever it is. The parasite control on the ground will be obtained best by the methods of cultivation to be mentioned hereafter. The adjustment of new species of parasites and predators in each new region makes it apparent that the boll weevil will everywhere be attacked by those species of insects most fitted to attack it under the existing local conditions. This attack will be of greatest impor- tance in regions where humidity tends to reduce the effectiveness of other forms of control. By Table LXIII we show the final summary of the records of para- sitism made for a period of years to illustrate the fact that this is a factor of great importance. TaBLeE LXIII.—Parasite control of the boll weevil, by years. Bee Mortality Year. ieeual Parasites. from BES: parasites. Per cent. DOU eee ee Ne ee cps os cle he a 602 7 1.16 OSE ae ects Sore rk Be oe ow einen bolt cictectt Rise cine a ease ee 819 59 7.20 LOGS March Sree wee fy oe Ae ep) ese) ee ee ee eee 1,005 32 3.18 LOOP AUTO US Lees nmin = ee ic oe ee ee Ba et 1,702 21 1.23 LOG Entre Reh e Ber ed oh Tee ee aD SGA oes tose SI oe ee ee eee 40,073 1, 728 4.31 LOOT eee en te ee eS ee ee a ee 13, 602 isi PAL 8. 24 EGU re ee ep eee: Sra ee! MORIA Ace ae ee eee 29, 349 2,952 10. 05 TOG A See a ere a ee ed Mi 8 Tee te. ot pel ne Ey Ce Re ee ee 11, 653 620 5. 32 Dotals'and averages =< 22.22 hs 2 sles Se se abe eee eee 98, 805 6, 540 6. 61 Table LXIII is based upon collections of squares and bolls made throughout the infested territory under a great diversity of conditions. The average monthly parasitic and predatory control for the years 1906 to 1909, inclusive, has been arranged below (Table LXIV) to show that insects are a factor of importance throughout the year. It should be noted especially that in the months of August and Septem- ber, when the boll weevils are most numerous, from 27 to 30 per cent of the immature stages are killed by insect enemies. The average for the year of 25 per cent offers great encouragement. Bul. 114, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE XVIII. 3 BoLL-WEEVIL PARASITES. a, Lariophagus texanus, female; b, emergence hole of Tetrastichus hunteri from weevil larva: c, Tetrastichus huntert, female; c’, antenna of same; d, puparium of Ennyomma globosain weevil larva; e, Ennyomma globosa; f, Cerambycobius cyaniceps, female; jf’, natural position ofsame. (Original.) We YH n= wy AWE n— oa NATURAL CONTROL. 145 Taste LXIV.— Weighted average insect control of immature stages of the boll weevil, by months. Per- Per- , > er- : Killed | centage Forms ex-| Stages | Killed | centage) “y 7 | killed | centage Month. F by par-| killed killed amined. | found. | (2.7 °. preda- by asites. | by par- hd ae by all asites. y ae insects. MEANUTAT Veryer Co) calico isinicia aiujers\siciwicis'soissieisis et 5,687 | 1,285 54 4. 20 63 4.90 9.10 ARG 1oy 0) 2 ee re met tate aha cys 2 stera' 13, 597 665 56 8. 42 60 9. 02 17. 44 j Witates nicer s cela arc teye cwtieininicinie b's eas Sale ccine 2,500 159 2 1.25 28 | 17.61 18. 86 BL St ese earn seattle on = ce cyhe dip e.iciainrninimewne Sie 100 56 2 3.957 0 . 00 3. 57 REND so TS aes eg a 16,930 | 10,708 553 GF AUG Ne ale) I ae Gi7/ Ups U8 NTE OE SE Nl Rome See Co oat ee 43,059 | 21,758 | 1,536] 7.051 3,247| 14.92] 21.97 PUPAL Gyn, eters “yarciefaiabas cic. s/sycie ei) sie eislaseie J 80,923 | 33,170 1,970 5.93 | 8,248 | 24.86 30. 79 ‘SHAOGO bys eee ee ee ee 37,378 | 17,107 | 1,160 6.78 | 3,495 | 20. 43 Dera WIGTOD EIR seen alas Ll este oie ated 17,344 | 8,283 879 | 10. 61 773 §. 33 19.94 IN GMEMNIDEN Sc aseee cine cae oe seco eee ited se Seeds 2,534 798 127 15. 91 2 ads) 16.16 INEQOET OS PSs a setae SSE 5 Soa ae See area ae 2, 663 688 82} 11.91 14 2.03 13.94 ANG TA SS Sie Stic S Os eae eee nae ee 2225715 194,677 | 6,420 |). 5. 28. RONG esas cca eters Veloce dgay Chae Grey cee ee aa cciteceecis ice seeimideslnecdiwteere lees oeees (Orfeo baaoeae 18. 92 25. 70 The weighted average insect control in June, July, August, and September proves to be 26.82 per cent and for the remainder of the year 17.11 per cent. A few records of high insect control will suffice to illustrate the extent of control under some conditions. TasBLeE LXV.—Highest records of insect control of the boll weevil. Location of Killed by Places. Date. squares. Stages. iTaseets: ( Per cent. PASITENIS nee cps eae: yee emi ters, ce ios cela ate a bictd-eie 25 Nae ose eke Aug. 1,1907 | Fallen..... 255 96. 11 Pare rises ill @xe tess cisrarela roles elaito «2,59 oye = =j-tars-aietbiot a Avge S19 08) | ae Aden aeee 100 92. 00 OMEHLOM ARO Rare pre eee ee ees aa ciosersts eis a cle Ne shee Avige) M1906: |cedove ce: 197 85. 20 INGOSMSR MN oes Gustes deed SARE Ee ee ae SE annie Aug. 1,1907 | Hanging .. 75 84. 00 (Bibs File, UGS boo os beige coor ge oae yee es Ge eee seccecioads Aug. 1,1906 | Fallen.... 1,310 78. 80 Wit@i@iia), UNGes Osean 2 en6> See eae eee Nhe cae Ae E er es July 29,1908 |: do. 2.22. 375 78. 38 ipaeillig, (MOS 4 theo elo pilot ede suede seeaao eon ne ace Sept. 1,1906 |...do...... 678 77. 40 JAIMIE OM, ANOS Sood 5: Se Accs See ae ee ele ae ee July —,1909 | Hanging .. 55 75. 44 (METS Cee ae Sst rats cha iaicin cio eo wate Galaisie siolale oraioeiae June 20,1908 | Fallen..... 549 73. 60 The distribution of insect control in the four principal classes of forms, and also by geographical sections, has been presented in the general discussion of natural control. BIRDS. Exhaustive studies of the stomachs of many birds killed in infested cotton fields by the agents of the Biological Survey of this depart- ment have emphasized the fact that the birds play a considerable part in the control of the adult boll weevils. This investigation has resulted in a list of 53 species which more or less commonly feed upon the adult weevils. In Cuba, Mr. E. A. Schwarz discovered that an oriole (Icterus hypomelas) has developed a habit of extracting the immature stages from the bolls and squares. Table LXVI, which follows, is taken from Circular 64 of the Bureau of Biological Survey. 28873°—S. Doc. 305, 62-2—~—10 ee a. wre” nee a 1} ia a | ys {> cee UWS 2 Dn Fr ah 146 Taste LXVI.—Schedule of stomach examinations of birds which had eaten boll weevils During Janu- = A During O ary, Febru- | , ete TA | ad ae ber, Novem- ary, an fed Ge Boa ber, and March sak ptember. | pecember D coo [=a in jen la la we io n wo ls es] =| o 5 ic qd QO: =| Oo -10 ° Species, Be (e378 Soles slag lea|e9 ia ea = |SFlog oe blesl_ sf elas las |e bls $8) s/°S/eg) se slse| g(°eloa) aig |pele2 s4\s8 e252 s8|leels3lo8 eels LE Aa 254 ee 4e 28a ae lageae ASISSIESISSISSIES SSISSIESIESIESIE 5S ISPS ES [SLs a |S Se/s isis AWGN lel (4s (a te ta ae Upland plover (Bartramia longicauda)......-..- 43 1-5. | eae 13 Alt Oe rie ene eee Medes Se Killdeer (Oxyechus vociferus)......-.---------- 28} 2 1 RY eres Pee ie eee! Fee 1 | eS Quail ( Colinus virginianus)-.-.....----=------- (#331 poe bo e LO ese Bl oes (Bee 108} 1 1 Nighthawk ( Chordeiles virginianus)s=2 23° 22 |e ee ae se el eee 10.) 4°). 15 eee Scissor-tailed flycatcher ( Muscivora forficata) . .|.----|----|-----|-- BE (Peet. ee Stas 7 |. seals spe Kingbird ( Pyrannius|tyrannws) =e - 2 Sea = fae 103) i) | eo i eb i ee ee Crested flycatcher ( Myiarchus crinitus).......-|-----|----|----- 7D A Le ee By it 3 |S ae eee Pheebe (Sayornis phebe) ..-\- - 2. = - 4 a te Se UR ec ace S| ose loser |pees yA aoe | L} 135s 3 Olive-sided flycatcher ( Nuttallornis borealis)...|-----|----|.-.--|---- eee eee Ad eee AS (eee fees Be Alder flycatcher (Empidonatz trailli alnorum)...|----- ee eel ee Bese eee 3 leak DAN ecg ets, em [eee Least flycatcher (Empidonar minimus)........|----- | 2ee| ee ed eee PEAS ae 14 7) QE eee Blue jay ( Cyanocitta cristata)....--.-.--------- ~ehol | mth Ly pie Oo aces Fae, fe Wy eee PS 2 > Veesetes bps Cowbird (Molothrius ater): Fn es 92| 4 Ay | 2" 29S) Spe ee 84 3 Shiphi2ar ise ats Red-winged blackbird (Agelaius pheniceus)....| 79 | 4 8 LG) LC eal dibs | eee 49| 2 2 Meadowlark (Sturnella magna).........------- 48212 10) || Sales eees eee i Ay Bes (rae 183 | 28 | 32 Western meadow lark (Sturnella neglecta)... ... 520) Bs) Deca ae eae 66 | 12}; 18 Orchard oriole .(icterws spurius) i. 42 322225 32. 52 | 5-222 | eee | Sees 20): 1 ek | LP POLS 304 R64 ee ee Baltimore oriole (Icterus galbuia).......-.....-|-----|-=--|--.-- Dales eee DO Ti 4s ee | ena) eerste Bullock oriole|(Icterus bullock?) -..- =.2-). 2.22 2] See | eee }2=44449 1°40 49s] 22 oe Bas Poe Rusty blackbird ( Zuphagus carolinus)......-.- yap al al NE Seay (RS) NSF Sc 10 |. 4) Brewer blackbird (Zuphagus cyanocephalus)...| 1389 | 24 | 40] 1 |...-|--.-|....-|..--|.---- 5) PA 2 Bronzed grackle (Quiscalus q. eneus)...-.----- 36 | 5 Selma ee 5 il Pee es et eas pe Great-tailed grackle (Megaquiscalus major | ANUELCT OUTILS) meee ose ee ee Saal mee PT | eg (ol i es ee | | Pee (eee 2. |sactfoues Vesper sparrow (Poccectes gramineus)....--.--- 29) 1 9 Webs ess, Pe tes eee ee gs ok [Se eee 6 BY heed er — Savanna sparrow (Passerculus sandwichensis, subspecies)... 2.2. pete, i (aes sm (2 emery apse beet | I” ener {Sa as Lark sparrow ( Chondestes grammacus)........-|-----|----|----- 1B} Mseaileaeelh Oe! | if | LS eee W hite-throated sparrow (Zonotrichia albicollis).| 53 | 1 dO eee a Pee Pees ee ee ees er 9 | 1 1 Field sparrow (Spizella pusilla).........-...-- a9 Bae Jal Wai 2a Ne) SCE 5 |: aes eee bs |----]---- Swamp sparrow ( Melospiza georgiana)......--. Zh Naat DAU a ie Ao Eee ohare ee Bets tae Fox sparrow, (Passereiia tliaca) - 2 2-ee. 2s as Shine 7 Jay eee) Pecavapey Feeeg sc Foe 22 eee ihe Qi 5 St Towhee (Pipilo erythrophthalmus).........-.-- 10s) 2 1 AP ee eee ee 6 | Bipre bt. Cardinal ( Cardinalis cardinalis)............---- YOM eel Ee fe cia Re a 39. |: .3,|: 4) 28h eee Texan prraplons (Pyrrhulozia s. terana)...-. fees ae eee ES [eres (ea al oe 64 | 2 2) | 222. See Painted bunting (Passerina ciris).........-.-- SS awe ieee Fea Pace 8 |...-=| 109.) 18). , 19. |e eee Dickcissel (Spiza americana).......-....------|-----|---- | eee off eee eG mes 32a | sereen He ALENT CRTOGIE SILDIS) set ee ee | oe oe eee py ts eed le Ly) el 1 CEL See Cliff swallow (Petrochelidon lunifrons) ........-- vi ee eee aT) (i eae 35. | 34) 638 |~ee Barn swallow ( Hirundo erythrogastra).........|---.-|--.- Fees Naga eit 143) 5 2a Gee eee Bank swallow (Riparia riparia)...............|.----|.--- pei (ece-re) aoa (aun 95°91] Br ee see Loggerhead shrike (Lanius ludovicianus)....--| AGW d. 7 Ps iad (Rea LO eee TEAS eee 5 Yellow warbler (Dendroica sestiva).. 2.22.2 4.. 14--fe|a-$ |e cfe ee| e 25| 1 The Reais es beet a Myrtle warbler (Dendroica coronata)........... W7e eed 21. 8 |v escloncel see 94 eee eee see eee Maryland yellowthroat (Geothlypis trichas)....| 2] 1 sR es bea ae | rk ae E | et eh Basse Yellow-breasted chat (Icteria wrens) _ 2.2 <. © 2 -2|5-- 24] esl Seales eee eee eee 1) bt Se) | American pipit (A nthus pensilvanicus)......-.- 3A eo4e | 1200 eee [eects Pachepeses ae ee ee 8] 3 4 Mockingbird ( Mimus polyglottos).........-.--- 43) 32 ya PS 9 Pp) ER 8s WSIS SS 5 GR fates |=. Brown thrasher ( Toxostoma rufum).......---- Grieg eee Y far pe fe ee eS | 29|} 1 1 Carolina wren ( Thryothorus ludovicianus)...... 37 | 6 co es) Gn ee i Reape sere 7| 5 6 Bewick wren ( Thryomanes bewicki)..........-- a Aa Se ase) (Soa ose + PSSA es PA bee se a Winter wren ( Nannus hyemalis)...........--- faa) al Ye nea eS |= scl oeqos| Ss: slat eee se le oe Tufted titmouse (Bxolophus bicolor)........... |} 14] 5 Y dal ee) Matos fee etal pA Wa fac Frese [reine os (Eo Black-crested titmouse (Bzolophus atricristatus)|.....|--.-|.----]----|----|---- 1 eerieesas A hee gi! 1 Carolina chickadee (Penthestes carolinensis)....| 6 | 1 j PA (eeaeae (eee dee 1 Precise LE ee } THE MEXICAN COTTON-BOLL WEEVIL. It will be noticed that the largest numbers of boll weevils were eaten during the months of July, August, and September, and also that a considerable number are consumed during the hibernating season. weevil during the winter. The most important birds are those that capture the boll According to this table these are the three species of blackbirds, two meadowlarks, six species of native sparrows, the pipit, the three species of wrens, and the two species of titmice. examined showed remains of the boll weevil. It will be noted that only one of the 108 quail stomachs weevils eaten. THE MEXICAN COTTON-BOLL WEEVIL. 147 REPRESSION. EFFECT OF BURIAL OF SQUARES AND WEEVILS. The effect of the burial of squares and weevils is of considerable importance for the reason that some degree of burial can be practiced _ in the ordinary processes of cultivation. If it were to be found that the weevils could be killed by a depth of burial which could be accomplished without interference with the root system of the plants this process would be of vast importance. At Tallulah, La., in 1910, Mr. G. D. Smith conducted an exten- sive series of burial experiments. The infested squares were placed in screened cages in the field. In each of these cages 2,000 infested squares were placed on October 10. A careful estimate showed that there were 250 live weevil stages for each 2,000 squares. In the first of the cages the infested squares were placed upon a sheet of wire screen 2 feet above the ground. These squares were kept constantly moist. In the second cage the squares were placed on the surface of the ground. No artificial moisture was supplied. In the third cage the squares were on the surface of the ground but were kept moist constantly. In the fourth cage the squares were buried to a depth of 2 inches and the ground was kept moist. In the fifth cage the squares were buried 4 inches and the ground was kept dry. The artificial moisture was applied three times each day during the course of the experiment. The ‘“‘dry’’ cages were cov- ered with canvas so that rains could not reach the squares. The soil in the locality was the typical ‘‘buckshot”’ of the Mississippi Delta. Immediately before the institution of the experiments several rains had made the soil moist. Observations on emergence were made from October 10 until November 15. Table LXVII summaries the results of these experiments. TaBLE LXVII.—Summary of experiments in the burial of squares infested by the boll weevil at Tallulah, La., October and November, 1910. Conditions. Teron) Emergence. Per cent. Cacenieass P2seetia OmelsUmda Re eIMOIS tpn yt ol Ae iam tue ee SNL RN 119 7.6 Cage J2ass4 pOmisuriacendr yee epee nee rs ek ais ate eine Bod ane aise ey 157 62.8 Capes e454 |e ON Stila Ge srtd OLS ie mone seers i Gem cy wea Fe stil be 147 58.8 Cage 4's ts |B unieds2 anh esydisyeme sre eee ai eee mee See ie! CNL Rae on 62 24.8 Cacetheaas eb unied yam clive sr O1S epee tpn” Deter us SI Dadar Me, 6 52 Cavern. =| DUnled Aan Chesm diya app oee Meee iat Soh NS CMe 18 sel ORYHS Pies sal] ABIUON COL AI maVeLaV SS ion YVOy hehe is Be ea a eS eee AS” A al Ro ae ge 0 0 It will be noticed that the greatest emergence was from the two cages In which the squares were placed upon the surface of the ground. At 2 and 4 inches beneath the surface the emergence was very small. When kept dry beneath 2 inches of the soil 24 per cent of the possible emergence occurred, but at this depth when moisture was provided less than 1 per cent emerged. At a depth of 4 inches 0.7 per cent emerged in the dry cage, but none from the same depth where mois- ture was provided. It may be concluded from these experiments that burial beneath 2 or more inches of dry soil of the ‘ buckshot”’ variety will prevent the emergence of a large portion of the weevils. If the soil is kept moist with burial at 2 inches or more below the suriace the emergence is practically negligible. This is shown most clearly by comparing cages 4 and 5 in the table. a a... on a eG a > wz a _ 148 THE MEXICAN COTTON-BOLL WEEVIL. LABORATORY EXPERIMENTS IN BURIAL. In an experiment performed at Victoria, Tex., m 1904, 1,000 infested squares were buried under from 2 to 5 inches of well-pul- | verized earth.! Seventy-five weevils emerged. Twenty-seven wee- vils were found which had been unable to reach the surface. Their location varied from the bottom of the receptacle to just beneath the surface. The weighted average of the distances covered by the weevils which failed to reach the surface was 2 inches. In another series of experiments at Victoria, Tex., 74 squares were placed under wet soil. It was found that 16 per cent of the weevil stages were killed. Of the weevils which became adult 30 per cent emerged from the squares, but only 23 per cent reached the surface or escaped from an average depth of 1 mch. In these experiments, considering all the weevil stages present, 35 per cent died without escaping from the soil. In 1904 Prof. E. D. Sanderson performed a number of burial experiments at College Station, Tex. At from 0.5 inch to 1.5 inches below the surface 26.7 per cent of the weevils emerged; at from 2 to 4 inches 4.7 per cent reached the surface. It will be noted that these laboratory experiments substantiate the conclusion drawn from the field experiments described previously regarding the greatly increased mortality brought about by deep burial and by moisture. BURIAL OF ADULT WEEVILS AT TIME OF HIBERNATION. On or after November 23, 1903, at Victoria, Tex., 1,000 adult weevils were buried under from 2 to 6 inches of soil which contained from 9 to 19 per cent of water. Only five of these weevils succeeded in reaching the surface. Four of those which escaped and one which was still buried in the earth were found alive when examination was made on March 16, 1904. All the remaining weevils appear to have died where they were buried. CONCLUSIONS FROM BURIAL EXPERIMENTS. The field and laboratory experiments to which references have been made indicate that the boll weevil has comparatively little ability to emerge from moist soil, while dry, partially pulverized soil offers small obstacles to their emergence. The experiments also show that burial, even under moist conditions, would have to be as deep as 2 inches:to bring about very decided results. The practical question therefore is whether in cotton fields the soil can be turned over to a depth of 2 inches during the growing season without injury to the crop. As is well known, one of the most important cultural methods in producing cotton is shallow cultivation. The reason for this is that the plant sends many lateral roots almost at right angles from the rows and at a very short distance beneath the surface. Many of these lateral roots he only 2 or 3 inches beneath the ground. If they were disturbed, the plants would react by shedding the squares. Undoubtedly the loss of fruit from this cause would more than offset any possible advantage accruing from the destruction of the 1 Much more thoroughly pulverized than would be the case in the field. Bul. 114, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE XIX. Fig. a.—Cotton before treatment with Paris green. (Original.) Fig. b.—Cotton one week aiter treatment with Paris green. (Original.) EFFECT OF PARIS GREEN ON COTTON. REPRESSION. 149 weevils by burial. It is thus clear that as a means of controlling the weevil during the growing season the burial of squares is imprac- ticable. There is a time, however, when the burial of the squares can be carried on to excellent advantage. This is in the fall when the maximum infestation has been reached. Under these conditions it makes no difference to the planter whether the lateral roots of the - cotton plant are cut or not. The fruit already set on the plants will _ develop in either case, and any additional fruit inevitably will be destroyed by the insects. Consequently the planter may destroy many of the weevils which would mature in a short time to feed, multiply, and enter hibernation, to emerge and damage the crop of the succeeding season. In this way deep fall cultivation is a pre- - liminary step that should be practiced in connection with the destruc- tion of the plants. It should precede that-process and should by no means be depended upon to take the place of it. After the plants have been uprooted and brought into windrows previous to burning it is advisable to plow the fields to a depth of at least 2 inches. This will result in the burial of many squares which were on the ground at the time of the uprooting or which fell during the process. The experiments show that the effectiveness of burial either before or after the uprooting of the plants will increase greatly if rains occur after the work is done. Likewise it is evident that the destruction of the weevils will be much greater in heavy soils than in lighter formations. In the Mississippi-Yazoo Delta the general nature of the soils is more or less heavy. This and the heavy precipitation in that region indicate a means of destroying the weevil that is especially important on account of the scarcity of direct means available. INSECTICIDES.! From the very beginning of the work on the boll weevil much atten- tion has been given to testing the more promising insecticides. As one result of the offer of a $50,000 prize by the State of Texas for an efficient remedy for the boll weevil, large numbers of supposed reme- dies have been proposed. Doubtless the inventors have been per- fectly sincere in their faith in the efficiency of these compounds. As was fully anticipated by the entomologists when the reward was offered, the commission charged with awarding the money was deluged with applications therefor, the claims in a large majority of cases being based upon some concoction supposed by the inventor to possess marvelous insecticidal properties. In comparatively few cases had the new product been tested in any way. Often samples were sent with the request that tests be made. Many of these inven- tions found their way to the various laboratories of this investigation, where it has been the uniform policy to give every thing of this kind a fair test and report the results to the originator. Tests were made in the field upon weevils confined by cages. This work has required a great deal of time, and the results have failed to indicate a single new compound having real value. Many of the substances tried had absolutely no effect on either plant or insect life, while others were equally fatal to both wherever they came in contact with them. The primary difficulty with all such insecticides lies in the fact that, 1 The first two paragraphs under this heading have been modified from Bull. 51, Bureau of Ento< mology, p. 156. Le ae. ee, ee os. ee oo) i" ey wey 15m hom 25.8 c h w ff So = 0 om 150 THE MEXICAN COTTON-BOLL WEEVIL. ’ owing to the peculiar habits and life history of the weevil, the poison — can not be so applied as to reach the immature stages at all, and it can not reach the adults so as to cause sufficient mortality to result in any considerable benefit to the crop. Much work has been done in thor- oughly testing the effect of Paris green. The most important results of this work have already been published in Farmers’ Bulletin No. 211 of the Department of Agriculture. They will be described briefly on a subsequent page. Among 40 other compounds tested, none proved worthy of even passing consideration for field use. As a fumigant for seed, among the eight gases or vapors tested, carbon bisulphid was found to possess considerable value when applied in the special manner described on pages 162, 163. POWDERED ARSENATE OF LEAD. In 1909 Messrs. Wilmon Newell and G. D. Smith, then of the Louisiana Crop Pest Commission, published the results of certain work with powdered arsenate of lead as a remedy against the boll weevil. This work was done in central Louisiana during the season of 1909. The principal experiments were located on three different plantations on plats provided for the purpose. From 1 to 10 appl- cations were made, consisting of a total amount of poison of from 1 to 51 pounds per acre. The treated cotton yielded an average of 71 per cent more than similar cotton which was not treated. In all except one of the plats there was a net profit from the use of the poison (that is, after deducting the cost of the poison and of the labor from the value of the increased yield) of from 27 cents to $23.54 per acre. In the one exception there was a loss of $7.07 per acre. These striking results led to extensive otk on powdered arsenate of lead by the Bureau of Entomology. The services of Mr. G. D. Smith, who was directly connected with the Louisiana work to which reference has been made, were obtained. The bureau instituted numerous experiments in Louisiana, including several which duph- cated the previous work in that State. This investigation has now extended through two seasons in Louisiana, and considerable work has also been done at Victoria, Tex., by Mr. J. D. Mitchell. In the experiments of 1910, 32 plats were utilized on plantations at Livonia, Shaw, and St. Joseph, La., and Victoria, Tex. In the work in Louisiana there was a profit from the use of the poison on 20 of the plats and a loss on the 12 remaining plats. The average loss on the plats which failed to show a profit was $6.99 per acre. The average profit on the remaining plats was $5.83 per acre. Twenty- two of the 32 plats showed an increased yield of from 35 pounds to 403 pounds of seed cotton per acre. A striking result was the fact that invariably the plats upon which small amounts of the poison were apphed showed profits. The work at Victoria, Tex., in 1910, con- sisted of four experiments. In only one of these experiments was a gain in yield obtained, and this amounted to only 59 pounds of seed cotton per acre. In all of the experiments at this place there was a loss from the application of the poison of from $1.55 to $6.52 per acre. In 1911 the work on powdered arsenate of lead was continued. In some respects the resiilts were contradictory of those obtained pre- viously, but there was agreement in that profits were obtained on all REPRESSION. 151 plats where small applications were made. On account of the apparent contradictions and the variations due to the seasons it is considered necessary to continue the work another season before definite conclusions as to the practical value of arsenate of lead can be drawn. MACHINES. FIELD MACHINERY. Many attempts have been made to ee machines that will assist 1n the warfare against the weevil. The only one of direct value that has been perfected is the chain cultivator (Pl. XX, ); Pl. XXI) invented by Dr. W. E. Hinds, formerly of the Bureau of Entomology, and patented by the Department of Agriculture for the benefit of the people of the United States. Its construction is based upon the discovery that the weevils in the infested squares that fall in such position as to be reached by the sun soon die. In a cotton field many of the infested squares fall within the shade of the plants, and are thus protected. The chain cultivator is designed to drag the fallen squares to the middles of the rows and leave them exposed to the sun. This it has been found to accomplish in a satisfactory manner. In fact, in tests the use of the machine has been found to result in a decided gain in production. : Although the chain cultivator was designed primarily for bringing the squares to the middles, it was found in field practice to have a most important cultural effect. The chains (so-called ‘‘log chains’’) are heavy enough to establish a perfect dust mulch and to destroy small weeds that may be starting. In fact, it is believed that this cultural effect would more than justify the use of the machine, regardless of the weevil. In view of the effect against the insect and the important cultural effect, it is believed that this implement or one similar to it should be used by every farmer in the weevil territory. The chain cultivator is now regularly manufactured by one of the large dealers in farm implements, but a satisfactory machine can be made by any blacksmith. Full directions are to be found in Farmers’ Bulletin 344, a copy of which may be obtained upon application to the Secretary of Agriculture. Some forms of cultivators now in use allow the attachment of boards which drag on the ground and carry the infested squares to the middles. In fact, the principle of the chain cultivator can be incorpo- rated in many implements now in use. It is strongly recommended that this be done for weevil control as well as for obtaining a dust mulch. : 1Many machines have been designed to jar the weevils and infested squares from the plant and to collect them, to pick the fallen squares from the ground, to kill by fumigation, and to burn all infested material on the ground. The Bureau of Entomology has carefully investigated the merits of representatives of all of these classes, beginning in 1895 with a square-collecting machine that had attracted considerable local attention in Bee County, Tex. Up to the present time none of these devices has been found to be practical or to offer any definite hope of being eventually successful. At one 1 The following three paragraphs are modified from Bull. 51, Bureau of Entomology, p. 157. wR 4-7" Ow (om Bhacrma Cc yh 152 THE MEXICAN COTTON-BOLL WEEVIL. time there seemed some hope that a machine designed to pick the squares from the ground by suction might’ be perfected. The experiments, however, have indicated probably insurmountable difficulties; and a large implement concern, after having experimented with the matter fully, has come to the conclusion that mechanical difficulties will always prevent the perfection of such a machine. The ultimate test of all methods or devices for controlling the weevil is to prove through a series of seasons, and under a large variety of conditions, that by their use there is produced an increase in the crop treated or protected of sufficient value to more than repay the expenses of the treatment or protection. As a general sb where machines have been used or poisons applied, planters have provided no check upon the results obtained and have kept no close records as to the expense involved and net gain or loss resulting from the treatment. The result of such applications is, therefore, merely a general impression of gain or loss which may not agree at all with the facts. In this connection it must be stated that all machines which assist in more satisfactory methods of preparation of the land and cultivation of the crop are of indirect advantage. This is especially the case with devices which increase the amount of work that a single hand or team of mules may do. In fact, the boll weevil has been the cause of much commendable improvement of agricultural machinery throughout the infested territory. GINNING MACHINERY:.! The more important results of studies upon this class of machinery were presented in Farmers’ Bulletin No. 209 of the Department of Agriculture. Modern cleaner feeders were found to be quite efficient in separating the weevils from the seed cotton, as they removed fully 70 per cent of the weevils passing into them. Of the weevils removed, over 80 per cent were still alive when taken from the trash. This fact shows the necessity for the use of some additional device which will crush or otherwise destroy all weevils taken from the cotton by the cleaner feeder. (See Pl. X, a.) For the weevils escaping the action of the cleaner feeder and passing into the ginning breast with the roll there are two avenues of escape— one with the seed, the other with the motes. In these two ways it appears that over 85 per cent of the weevils passing into the gin breast escape alive, while the remainder are killed by the saws. From these facts it is evident that some way should be provided for properly caring for the motes so as to confine the weevils which are thrown out among them and secure their destruction with those removed by the cleaner feeder. Some method should also be devised for separating from the seed the weevils that pass the saws before they reach the seed house or the farmers’ seed bins. When we consider the important effect that gins have been found to possess in spreading the weevil, especially near the border line of infestation, it appears exceedingly desirable that improvements in gin machinery should be made in the following particulars: First. The area and distance through which the action of the picker roll in the cleaner feeder is continued should be considerably increased, ! This section is modified from Bull. 51, Bureau of Entomology, pp. 158, 159. Bul. 114, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE XX. i Rm ae Fig. a.—Early fall destruction of stalks, the fundamental method for controlling the boll weevil. Windrowing stalks for burning. (Original.) ee nD Fig. b.—Chain cultivator passing through cotton rows. (Original.) CULTURAL CONTROL OF THE BOLL WEEVIL. Bul. 114, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE XXIi. (Original.) ffeect after passage of cultivator. 1D) Tig. b. Lic j. (.—Space between cotton rows before passage of cultivator. ’ (Original. ) USE OF CHAIN CULTIVATOR. REPRESSION. 153 compression rollers or some other device being employed to destroy - the weevils separated by the cleaner. Second. Some method should be devised for keeping under control the weevils escaping alive with the motes, as under present conditions they have free range through the ginnery. Third. Possibly the most important of the devices needed is an apparatus which may be applied near the gin (possibly as the seeds leave the gin breast and drop into the seed chute) by which the weevils may be separated from the seed and brought under control, so that they may be destroyed. With these improvements the oil mills would almost cease to be a factor in the dissemination of weevils, and the movement of seed, either for planting, stock feeding, or fertilizer, would practically cease to be what it is at present, a factor in the spread of the weevil. FUTILE METHODS WHICH HAVE BEEN SUGGESTED.! MINERAL PAINT AND COTTONSEED OIL. The very serious nature of the boll-weevil problem is constantly illustrated by the manner in which various useless devices and nos- trums are brought to public attention. At one time it was widely alleged that mineral paint would act as a specific against the weevil. An equally fallacious theory that also received considerable popular attention was to the effect that cottonseed meal exerted a powerful attraction for the pest. SPRAYING. Probably the most important useless recommendation has been that of spraying. It was supposed for some time by certain parties that it might be possible to poison weevils economically by attracting them to some sweetened preparation. The experiments conducted to determine the attraction of various sweetened substances demon- strate the fallacy of the theory. Even if these substances exerted as much attraction as was supposed, there would be insurmountable difficulties in the application of the method in the field. It is true that it is possible to destroy a certain number of weevils in regions where stubble cotton occurs by heavily spraying the earliest plants, but this method is of immeasurably less importance than the simple practice of cultural methods. SULPHUR. The old idea, the fallacy of which has been explained repeatedly by economic entomologists for the past 50 years, namely, that sulphur can be forced into the system of the plants to make them immune to insect attack, sometimes crops out with reference to the boll weevil. It is scarcely necessary to call attention to the fallacy of attempting to destroy the boll weevil by soaking the seed in chemicals with the hope of making the plants that are to grow from them distasteful or oisonous to the insect. Any money expended by the farmer in Falliowrine this absurd practice is entirely wasted. 1 This section is greatly modified from Bull. 51, Bureau of Entomology, pp. 159, 160. 154 THE MEXICAN COTTON-BOLL WEEVIL. PARIS GREEN. One of the most mporteny fallacies regarding a remedy for the boll . weevil was that which received great attention during the season of 1904, namely, that Paris green is a spac for the pest. The ‘urgent demand for a specific was evidenced by the very extensive use of this substance. A portion of the great attention that it received pub- licly was due to the fact that early m the season a certain number of weevils may be killed by it. Applications made by spraying are even less effective than dusting with the dry Paris green. As was pointed out in Farmers’ Bulletin No. 211, which deals with exhaustive field and laboratory experiments with Paris green, the number so de- stroyed in the spring really means nothing whatever to the crop later in the season when the ae have put on squares and the poison is no longer effective. As a matter of fact, the uselessness of Paris green was quickly discovered by planters. Since 1904 prac- tically none has been used in the warfare against the pest. (See PERE) TRAPPING AT LIGHT. There is still, in many quarters in Texas and Louisiana, a supposi- tion that it is possible to attract the boll weevil to hghts. A number of machines have been constructed based upon this idea. Whether or not the boll weevil can be attracted to ights was one of the first matters that was investigated by entomologists. During September, 1897, Mr. J. D. Mitchell, of Victoria, Tex., a naturalist and cotton planter, set out trap lanterns in a cotton field in Victoria for one night, and sent the insects captured to this bureau for examination. In all, 24,492 specimens were taken, representing approximately 328 species. Divided according to habit, whether injurious or beneficial, the result was: Injurious species, 13,113 specimens; beneficial spe- cles, 8,262 specimens; of a negative character, 3,117. The interest- ing point in connection with this experiment was the fact that not a single specimen of the boll weevil was found, although the lights were placed in the midst of fields where the insects were very abundant. Since that time other investigators have looked into this matter fully. Lights have been kept burning in cotton fields night after night for several weeks. In no case has a single specimen of the boll weevil been discovered, although thousands of species of insects have been captured. The popular misapprehension about the possibility of capturing the boll weevil at Wane is due to the fact that somewhat similar insects, Balaninus victoriensis, and other acorn weevils, differ from the boll weevil in that lights exert a strong attraction for them. Dur- ing occasional seasons the acorn weevils are exceedingly common in Texas, and great numbers of them fly to the electric lights. OTHER PROPOSED REMEDIES. Tundreds of proposed remedies, in addition to those which have been mentioned, have been carefully investigated. The claims of their advocates in practically all cases are based upon faulty obser- vations or careless experiments. The strong tendency of the weevil to die in confinement, which has been referred to, has caused many REPRESSION. 155 _ honest persons to suppose that the substances they are applying have killed it. Moreover, an insuperable difficulty that these special preparations have encountered is the impracticability of the appli- cation in the field. Hundreds of known substances will kill the weevil when brought into contact withit. The difficulty is to apply them in an economical way in the field. The claims made at different times of the repellent power of tobacco, castor-bean plants, and pepper plants against the boll weevil have no foundation whatever. In fact, none of these plants has the least effect in keeping weevils away from cotton. REQUIREMENTS OF A SATISFACTORY METHOD OF BOLL-WEEVIL CONTROL! The difficulties in the way of controlling the boll weevil he both in its habits and manner of work and also in the peculiar industrial conditions involved in the production of the tale in the Southern States. Thefacts that in all stages, except theimago, the weevil lives within the fruit of the plant, well protected from any poisons that might be applied, and in that stage takes food normally only by insert- ing its snout within the substance of the plant; that it frequently requires only 12 days for development from egg to adult, and the progeny of a single pair in a season may exceed 3,000,000 individuals; that it adapts itself to climatic conditions to the extent that the egg stage alone in November may occupy as much time as all the imma- ture stages together in July or August, are factors that combine to make it one of the most difficult insects to control. It is, conse- quently, natural that all the investigations of the Bureau of Ento- mology have pointed toward the prime importance of methods of control which involve no outlay for materials and very little for labor. Methods which involve some direct financial outlay for material or machinery are not in accord with labor conditions surrounding cotton production in the United States. Moreover, the indirect methods advocated are in keeping with the general tendency of cotton culture ; that is, to procure an early crop, and at the same time have the great advantage of avoiding damage by a large number of other destruc- tive insects, especially the bollworm. Nevertheless it must not be understood that attention has not been paid to the investigation of means looking toward the direct extermination of the pest. Much work has been done, but the results have all been negative. BASIS FOR MEANS OF REPRESSION. In spite of the many difficulties involved in the control of the boll weevil certain generally satisfactory means of repression are at hand. They consist of both direct and indirect means. Those of an indi- rect nature are designed to increase the advantage gained by the direct measures and to increase the effectiveness of the several natu- ral factors which serve to reduce the number of weevils. Thus, the control measures constitute a combination of expedients, the parts of which interact in many ways. Naturally, the best results are obtained when the planter can put into practice all of the essential parts of the combination. . 1 This section is greatly modified from Bull. 51, Bureau of Entomology, pp. 160, 161. 156 THE MEXICAN COTTON-BOLL WEEVIL. It is obvious that any method of controlling the boll weevil must depend upon full knowledge regarding its life history and the natural forces which tend to prevent its multiplication. Certain practices which upon superficial observation might be considered important in the control of the insect upon investigation may be found to be of no avail whatever. In fact, in some cases what appear to be feasible means of control are worse than useless, because they tend to nullify the effects of natural forces which act against the weevil. This is notably the case with the practice of attaching a bar to a cultivator to jar the infested squares from the plants. As will be explained later, this practice is of advantage only under very restricted conditions. Throughout the greater part of the infested territory it is an assistance rather than a hindrance to the boll weevil. There are seven features of the life history of the weevil that are of cardinal importance in control. These are indicated below. 1. The weevil has no food plant but cotton. 2. The mortality of the weevil during the winter is very high. 3. The emergence from hibernating quarters during the spring is slow and prolonged until well into the summer. 4. Early in the season, on account of comparatively low tempera- tures, the development of the weevil is much slower than during the summer months. 5. The drying of the infested squares, as the result of heat, soon destroys the immature stages of the weevil contained therein. 6. The weevil is attacked by many different species of insect ene- mies, the effectiveness of which is increased by certain practices. ke ae weevil has but little ability to emerge when buried under wet soil. Exactly how each of these features of the life history of the weevil affects plans for practical control will be explained in the following paragraphs. In the case of many of the important injurious insects the problem of control is greatly complicated by the fact that the pests can sub- sist upon more than one food plant. In some cases a single species attacks several cultivated crops. In other cases the pests can sub- sist upon native plants practically as well as upon the cultivated species. All these difficulties are absent in the case of the boll-weevil problem. As has been shown in the preceding pages, the insect is absolutely restricted to the cotton plant for food and for opportu- nities for breeding. The problem is therefore much more simple than it would be if the weevil could subsist upon any other plant in the absence of cotton. This peculiarity of the weevil was the basis of the recommendation made in 1894 that the pest be exterminated absolutely in the United States by the abandonment of cotton. At that time only a few counties in Texas were affected. The procedure would have involved small expense. Even now the weevil could be exterminated in a single season by preventing the planting of cotton and the growth of volunteer plants. This proposal has been made at various times, notably at the national boll-weevil convention held in Shreveport, La., in 1906. _ Various difficulties, however, appear to render the plan entirely impracticable. In the first place, there would be strong opposition in large regions in Texas where the planters have learned to combat REPRESSION. . ENT” the weevil successfully. This opposition would undoubtedly be sufficiently strong to prevent cooperation in a large territory. More- over, the expense would be enormous. A large army of inspectors would be required. The work would not end with the prevention of planting cotton, but would necessarily extend to the destruction of volunteer plants which would be found along roads, railroads, about gins and oil mills, and on plantations throughout the infested region. The loss to mills, railroads, merchants, banks, and others dependent upon the cotton trade would complicate matters further. Unless a plan of rermbursement were followed there would be stren- uous opposition from these quarters, and any scheme of payment for damages would increase the cost still further. From a theoretical standpoint all the expenses involved would be justified. The saving in a tow years would more than offset the cost. Nevertheless, the practical difficulties undoubtedly will always prevent the execution of the plan. All interests now seem to favor the necessary adjust- ment of conditions to the boll weevil rather than total eradication— once practicable but now little more than visionary. Under the discussion of the hibernation of the weevil it was shown that during the several years in which careful experiments have been performed the average rate of survival was 7.6 per cent. It is note- worthy that frequently the survival is much smaller. In the ex- periments to which reference has been made it ranged from 0.5 per cent to 20 per cent. The most important means of controlling the boll weevil that are available are designed to increase the tremendous mortality caused by natural conditions during the winter. The destruction of any certain number of weevils during the winter is much more important than the destruction of much larger numbers at any other season. The best means at the command of the farmer for increasing the winter mortality is through the uprooting and burning or burial “ot the stalks at an early date in the fall. (See Pl. XX, a.) Numerous experiments have shown the lessened mortality due to depriving the weevils of their food at early dates in the autumn. In fact, the experiments showed a practically uniform increase in the number of weevils surviving as the dates of the destruction of the plants became later. For instance, in all of the experiments per- formed in Texas it was found that destruction in September re- sulted in a survival of only 0.2 per cent; destruction two weeks later showed a survival of 2.3 per cent; destruction during the last half of October, 5.6 per cent; and during the first half of November, 15.4 per cent. The results of the Louisiana experiments were similar. Destruction in September showed a survival of 0.3 per cent; destruc- tion in the first half of October, 2 per cent; in the last half of October, 8 per cent. In addition to the experiments in which the weevils have been placed in cages at different times in the fall, the Bureau of Ento- mology has conducted considerable field work to show the benefits of fall destruction. The most striking experiment was performed at Calhoun County, Tex., in 1906. In this experiment an isolated area of over 400 acres of cotton was utilized. There was no other cotton within a distance of 15 miles. By contracts entered into by the department, the farmers uprooted and burned all of the ee during the first 10 days in October, and provision was made to prevent 158 THE MEXICAN COTTON-BOLL WEEVIL. the growing of sprout cotton. As a check against this area, cotton lands about 30 miles away were used. Here the stalks were not de- — stroyed in the fall, and the interpretation of the results of the experi- ment was based upon a comparison of the number of weevils present during the following season in the two localities. In May following the destruction of the plants careful search revealed only one weevil in the experimental area. In the check, however, the weevils were so numerous at this time that practically all of the squares had been destroyed. Examinations made later showed similar advantage in regard to freedom from the boll weevil of the area where the stalks were destroyed in October. The last examination was made on August 20. At this time there were 10 sound bolls to the plant on the experimental area and only 3 to the plant in the check area. The difference in yield between the two areas was about 600 pounds of seed cotton per acre. The work, therefore, resulted in an advan- tage amounting to about $18 per acre. Sle Newell and Dougherty! have described a very satisfactory device for cutting the cotton stalks in the fall. It consists of a triangular wooden framework, designed to pass between the rows and cut two at the same time. In the process of cutting, the machine windrows the stalks from two rows into the middle between the rows. The runners are provided with knives made of sharpened metal. Old saws have been found well adapted to the purpose. It is important to provide a metal runner at the rear end of the machine to prevent Hae This runner is designed to run an inch or more beneath the surface of the ground. The device can be made by any black- smith at a cost of about $4. It will cut and windrow from 10 to 15 acres of stalks in a day. There is a disadvantage in cutting the stalks at or near the surface of the ground: If warm weather follows, many of the roots will give rise to sprouts that will furnish the weevils food. On this account the process is less effective than uprooting the plants. Wherever the stalk cutter is used, it should be followed by plows to remove the roots from the ground. There is another important means by which the winter mortality of the weevil may be increased. This is by removing the hibernating quarters or destroying them after the weevil has gone into hibernation. Many of the insects are to be found in the winter in trash and débris found in and about cotton fields. The more shelter there is provided in the form of weeds growing about the fields, the more ashe ible the conditions will be for the insect. By the burning of such hiber- nating quarters as are found in the cotton fields and in their immediate vicinity a farmer can cut off a very large proportion of the weevils that would otherwise emerge to damage the crop. The prolonged period of emergence from hibernation gives the planter another important advantage over the weevil. It has been shown on preceding pages that the period of emergence from hiber- nation extends, in normal seasons, to practically the 1st of July. In fact, except in one of the experiments that was performed, the last weevils did not appear until after the 20th of June. In the one exception the last weevils appeared on the 6th of June. In Texas it was found that 75 per cent of the emerging weevils appeared after ! Cir. 30, Louisiana Crop Pest Commission. REPRESSION. 159 _ April 8 and in Louisiana 64 per cent. In Texas, after May 1, in all the experiments, from 4 to 18 per cent of the surviving weevils appeared. In Louisiana, after May 1, from 30 to 40 per cent emerged. t is obvious that the fact that many weevils do not appear until _ long after cotton can be planted and brought to a fruiting stage is a very great advantage to the planter. A portion of a crop at least can be set before the weevils have become active. Usually it is Pee to plant a crop sufficiently early to have it set some fruit efore much more than 50 per cent of the surviving weevils have emerged. Attention was directed to the fact that the development of the weevil is much slower in the early portion of the season than later. For instance, at Vicksburg, Miss., the average period of development in April is 30 days and in May 19 days. In June the period is short- ened to 15 days. Consequently the planter has an opportunity to force the development of fruit on the plants when the weevils are being held in check by the temperatures of the spring months. The ability of the cotton plant to grow during April and May is much ereater than that of the weevils. This gives a margin of which the planter can take advantage. In the section dealing with natural control it was shown that climatic checks are the most important that the boll weevil experi- ences. The principal manner in which climatic factors affect the weevil is through the drying of the fruit. Naturally, the more heat and light there is to reach the fallen squares, the greater will be the effectiveness of the most important natural means of control. This is the basis for the recommendation that the plants should be given considerable space, not only between the rows, but in the drill. Of course, 1t would be possible to place the plants entirely too far apart, and thus reduce the yield. There is a happy medium, however, at which: planters must arrive from experience on their individual places. At the same time, varieties should be cultivated which have a minimum tendency toward the formation of leafage. The work of the insect enemies of the boll weevil is increasing from year to year. This work should be encouraged in so far as possible. It happens that several of the recommendations made for other rea- sons will result in facilitating the work of the enemies of the weevil. This is the case with early planting, wide spacing, and the use of varieties with sparse rather than dense leafage. [Even fall destruc- tion is not a disadvantage, because it forces the parasites at the active season to native hosts that carry them through the winter. Wherever possible, varieties should be planted which retain a large proportion of the infested squares, because the hanging squares are more favorable for parasite attack than those which fall. Whenever the squares are picked by hand they should not be burned or buried, but placed in screened cages. In this way the weevils will be destroyed while the parasites may escape. Numerous experiments have shown that a large proportion of the weevils buried under 2 inches of moist soil can not reach the surface. Unfortunately, it is not possible to plow the infested squares under 2 inches of soil during the growing season. The operation would result in injury to the root system and cause great shedding. Never- theless it 1s possible for the planter to follow this practice after maximum infestation has been reached and after the plants have 160 THE MEXICAN COTTON-BOLL WEEVIL. been uprooted. Therefore, every means should be taken at the time of maximum infestation to plow under the infested squares as deeply as possible. This method is of little use in dry regions, but fortunately is of great importance in humid regions where other means of control are comparatively lacking in efficiency. It is also assisted greatly by the occurrence of large areas of so-called stiff soils in the humid area. SUMMARY OF MEANS OF REPRESSION OF THE BOLL WEEVIL. In the preceding pages all effective methods of controlling the boll weevil have been described in a general way, and their connec- tion with the life history of the insect shown. Further details regard- ing the application of the methods have been published in Farmers’ Bulletin 344. In the present connection it will be sufficient to sum- marize the subject. The following are the essential features of the | control of the boll weevil: 1. Prevention of the nvasion of new territory by means of quarantines — directed against farm commodities that are likely to carry the weevil. — It is not necessary to have a quarantine applied to an extended list of articles. Only a few forms of cotton and of cotton by-products need to be considered. The most important is seed cotton. Next in importance are cottonseed and cottonseed hulls. There is no danger in cottonseed meal and scarcely any appreciable danger in baled cotton. Cottonseed can be easily rendered entirely safe by fumigation with carbon bisulphid, as described in this bulletin. 2. The destruction of the weevils in the fall by uprooting and burning or burying the plants. This is by far the most important step in con- trol. (See Pl. XX, a.) It isso important that unless it is followed all other means will avail little to the planter. The burning of the cotton plants is, of course, a bad agricultural practice. It should not be ralloeed except In extreme emergencies. In all other cases the plants should be uprooted as soon as the cotton can be picked and cut by means of stele choppers and immediately plowed beneath the surface. The ground should afterwards be har- rowed or dragged to make it still more difficult for the insects to emerge. In many cases it will be found inadvisable to wait for the uprooting of the plants until all of the cotton is picked. After only a small portion remains for the pickers, it is entirely feasible to uproot the plants by means of a turning plow and leave them in the field so that the cotton can be picked. This will hasten the opening of the green bolls and fnbanen ly result in a considerable saving to the planter. 3. The destruction of the weevils during the winter. This is accom- plished by the destruction of the places in which the insects hibernate. Many such places are found in the cotton fields or in their immediate vicinity. A certain number of the weevils will of course make their way into the heavy woods and other situations beyond the reach of of the planter, but many remain where they can be reached. 4. Obtaining an early crop. (See Pl. XXII.) The importance of obtaining an early crop has been shown to depend upon the small number of weevils which hibernate successfully, their late emergence from hibernating quarters, and their comparatively slow development Bul. 114, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE XXII. Fig. a.—Late-planted cotton under boll-weevil conditions, given same culture as early planting. (Original. ) Fig. b.—Early-planted cotton adjoining the late planting under same conditions. (Original.) RESULTS OF EARLY AND LATE PLANTING OF COTTON. REPRESSION. 161 - during the early part of the season. The obtaining of an early crop _ is brought about by early preparation of the soil, by early planting, by the use of early-maturing varieties, by a system of fertilization which will stimulate the growth of the plants, and by continuous shallow cultivation during the season. 5. increasing the effects of climatic control. As has been shown, practically 50 per cent of all the weevil stages throughout the infested territory are destroyed by climatic influences. This means that the power of reproduction of the weevils is reduced by one-half. A planter can increase the advantage in his favor by providing a suitable distance between the plants and between the rows. It is also impor- tant to use varieties, where possible, which have a comparatively small leaf area. ‘The use of the chain cultivator will be found of great value in connection with obtaining the full effects of climatic control. 6. Encouraging the wsect enemies of the weewl. This is accom- plished in part by procedures already recommended and further by the use of varieties which have a well-developed tendency to retain the fruit and which also have a comparatively open structure and small leafage. 7. Hand picking of weevils and squares. This is a practice of little general importance. Although under some local conditions it may be highly advisable, everything depends upon the cheapness with which the work can be done. On crops produced by wage hands it is doubtful if the hand picking of the weevils or squares will ever result in any profit. Where the crop is produced on the share basis, and the acreage is sufficiently small to allow considerable work in the picking of the squares, the practice will undoubtedly pay. It is, therefore, a matter that must be taken into consideration by each individual planter. It can not be recommended generally, for the reason that under many conditions it would result in loss. Wherever square picking is practiced the squares should not be burned. They should be placed in cages, so that the parasites may escape and continue their work. As a matter of fact, under most conditions it is likely that the encouragement that can be given the parasites by this means is of much more importance than any direct checking of the weevil by the process of hand picking. Wherever squares are burned the planter is merely destroying the enemies of the weevil and consequently working against his own interest. 8. Control at gins.—The use of modern cleaner feeders will eliminate practically all of the weevils from cottonseed. Such devices should be used at least in the ease of all seed that 1s intended for shipment into any infested localities and especially along the outer border of the infested territory, where wagons may carry infested cottonseed some distance into territory that has not been reached by the weevil. It is important in connection with the cleaner feeders to provide some means for the destruction of the insects that are captured. In some cases where the cleaner feeders are in operation the discharge is allowed to accumulate in an open barrel or box. From such recep- tacles weevils readily make their way into the seed cotton in storage. It is a simple matter to provide compression rollers through which: the discharge from the cleaner feeder is passed. If, for any reason, the use of compression rollers is impracticable, the trash should be 28873°—S. Doc. 305, 62-2——11 162 THE MEXICAN COTTON-BOLL WEEVIL. fumigated at frequent intervals by means of carbon bisulphid or col- J. lected in a closed chamber and burned before the weevils have an J}: opportunity to escape. (See Pl. X, a.) 9. Fumigation of seed (fig. 34). This is a means of repression that will be of avail only in the case of shipments of seed into uninfested territory. It has been found that carbon bisulphid is the most sat- isfactory agent to use. Great care should be taken to insure thor- oughness of application. The use of a crossbar attached to the cultivator to jar the infested squares from the plants has frequently been recommended. Under some conditions this practice should be followed, but under others it is worse than futile. It was shown, in the treatment of the subject of natural control of the weevil, that in the humid region, including Arkansas, Louisiana, and the eastern portion of Texas, the mortality in hanging squares is greater than in fallen squares. For this reason it is better for the squares to remain on the plants. There is another reason why they should be allowed to remain on the plants which applies especially to the moist region in which the boll weevil is now doing great damage. This is, that the hanging squares are much preferred by the boll-weevil parasites. The records have invariably shown a higher rate of parasitism in hanging squares than in fallen squares. In this way the hanging squares furnish a means for the breeding of parasites, thereby enabling them to establish themselves in the field. It will be noted that the means of repression of the boll weevil may be divided into two classes, namely, direct and indirect. The direct means of control are the destruction of the weevils in the fall by destroying the plants and burning or burying the immature stages, hand picking of weevils and squares under some conditions, the burial of the infested forms at the time of maximum infestation, and the burning of the hibernating weevils in their winter quarters. The indirect means of control are early planting, the use of early varieties and of fertilizers that will noralcrate erowth, the selection of fields where the soil is suitable to rapid development, frequent shallow cultivation, the encouragement of the parasites of the weevil by placing the infested squares that may be picked by hand in cages instead of burning them, and the use of machinery which facilitates the various operations in preparing the land and cultivating the crop. These have the effect of increasing the acreage that a hand may cul- tivate. In view of the fact that the boll weevil forces a reduction in the acreage per hand, this is a consideration of some moment. DESTROYING THE BOLL WEEVIL IN COTTON SEED. It has been shown in this bulletin that adult weevils are frequently to be found in cotton seed and that there is danger in the dissemina- tion of the pest through the shipment of the seed. A number of experiments have been performed to discover means of killing the weevils found in seed. There are great difficulties to be overcome on account of the density of the seed and its practical impenetra- bility by certain fumigants. It was shown, for instance, that hydro- cyanic-acid gas has practically no penetrating power whatever. Carbon bisulphid was found to be satisfactory, although a special apparatus and special manipulation of the seed are necessary to sure REPRESSION. t6s success. The method described below, from Farmers’ Bulletin 209, is that which has been used by the bureau in cases where it has been necessary to free cotton seed of the weevils. The following plan for this work is proposed: A tight matched-board box should be provided having sides 4 feet high, open on top, and of other dimensions to accommodate 12 or more 100-pound sacks of cotton seed placed upright upon the bottom. Another tier of sacks could be added if desired. Into each one of these sacks about 1 ounce of carbon bisulphid should be forced by an apparatus for volatilizing the liquid and mix- ing the vapor with air. The accompanying illustration (fig. 34) will give an idea of this apparatus. It should consist of three essential parts, as shown in the illustration. A is an air pump having sufficient storage capacity to enable it to maintain a steady discharge of air for several minutes without continu- ous pumping. The stop- cock at a, regulates or prevents the escape of air, as may be desired. B is an ordinary 2-quart bottle fitted at b! with a tight stopper of good length, having two openings, through which the inlet and outlet pipes pass. These pipes may be of glass or metal and should be as large as can be used. The inlet pipe, b,, reaches nearly to the bottom of the bottle and is provided at the lower end with a per- forated metal cap as large as will pass through the neck of the bottle. This allows the escape of the air in small bubbles and insures rapid evaporation. The outlet pipe, b,, reaches only through the stopper. Upon the outside of the bottle is pasted a paper marked with l-ounce grad- uations. C is a piece of bai ordinary 2-inch iron gas : ane pipe about 34 feet long, Fig. 34.—Apparatus for fa etane See seed in the sack. (After but this may be any de- 3 sired length. It is closed and roundly pointed at the tip, and for about 15 to 18 inches of its length provided with small perforations pointing in all directions to give free escape to the vapor into all parts of the sack of seed at once. The connections may be of rubber tubing, but as little rubber as possible should be used for this apparatus, as it is affected by the vapor of the bisulphid, and the couplings will have to be frequently replaced. This, however, will not be a considerable item of expense. With the apparatus just described one operator would be able to accom- plish the entire work of disinfection. The amount of carbon bisulphid recommended is about | ounce for each 3-bushel sack. It is safe to say that this can be secured for less than 1 cent per ounce when purchased in 25 or'50 pound lots, making the cost of bisulphid not over 1 cent per sack. As it requires but from two to three minutes to vaporize 1 ounce of the liquid in the manner described, the expense for labor in appli- ~ cation would not amount to one-half a cent per sack. Fumigation with carbon bisul- phid can therefore be effectively made at the slight expense of from 1 to 14 cents per 100-pound sack. : Application of the bisulphid in this manner reduces the elements of danger to a minimum, as the vapor is almost wholly confined and the slight quantity escaping, mixed with the open air, would not be in either inflammable or explosive proportions. It has been determined that the slight trace of bisulphid vapor in the air would not injure the operator in the slightest degree, The sacks should be left in the box for forty hours after the gas is injected. 164 THE MEXICAN COTTON-BOLL WEEVIL. LEGAL RESTRICTIONS REGARDING THE BOLL WEEVIL. UNITED STATES STATUTE. The statute, quoted in part below, prohibits the interstate ship- ment of the boll weevil and certain other insects, and provides penalties: AN ACT To prohibit the importation or interstate transportation of insect pests, and the use of the United States mails for that purpose. That no railroad, steamboat, express, stage, or other transportation company shall knowingly transport from one State or Territory into any other State or Territory, or from the District of Columbia into a State or Territory, or from a State or Territo into the District of Columbia, or from a foreign country into the United States, the * * * boll weevil, ina live state, or other insect in a live state which is notoriously injurious to cultivated crops; * * * or the eggs, pupz or larve of any insect injurious as aforesaid, except when shipped for scientific purposes under the regula- tions hereinafter provided for, nor shall any person remove from one State or Territory into another State or Territory, or from a foreign country into the United States, or from a State or Territory into the District of Columbia, or from the District of Columbia into any State or Territory, except for scientific purposes under the regulations herein- after provided for, the * * * boll weevil, * * * in a live state, or other insect in a live state which is notoriously injurious to cultivated crops; * * * or the eggs, pupz or larve of any insect injurious as aforesaid. (33 Stat. L., 1269.) Sec. 2. That any letter, parcel, box, or other package containing the * * * boll weevil * * * inalive state or other insect in a live state which is notoriously injurious to cultivated crops; * * * or any letter, parcel, box, or package which contains the eggs, pupz or larve of any insect injurious as aforesaid, whether sealed as first class matter or not, is hereby declared to be nonmailable matter, except when mailed for scientific purposes under the regulations hereinafter provided for, and shall not be conveyed in the mails, nor delivered from any post office, nor by any letter carrier, except when mailed for scientific purposes under the regulations here- inafter provided for; and any person who shall knowingly deposit, or cause to be deposited, for mailing or delivery, anything declared by this section to be nonmail- able matter, or cause to be taken from the mails for the purpose of retaining, circulat- ing, or disposing of, or of aiding in the retention, circulation or disposition of the same shall, for each and every offense, be fined, upon conviction thereof, not more than five thousand dollars or imprisoned at hard labor not more than five years, or both, at the discretion of the court: Provided, That nothing in this Act shall authorize any person to open any letter or sealed matter of the first class not addressed to himself. (33 Stat. L., 1270.) Sec. 3. That it shall be the duty of the Secretary of Agriculture and he is hereby authorized and directed to prepare and promulgate rules and regulations under which the insects covered by sections one and two of this Act may be mailed, shipped, transported, delivered and removed, for scientific purposes, from one State or Terri- tory into another State or Territory, or from the District of Columbia into a State or Territory, or from a State or Territory into the District of Columbia, and any insects covered by sections one and two of this Act may be so mailed, shipped, transported, delivered and removed, for scientific purposes, under the rules and regulations of the Secretary of Agriculture: Provided, That the rules and regulations of the Secretary of Agriculture, in so faras they affect the method of mailing insects, shall be approved by the Postmaster-General, and nothing in this Act shall be construed to prevent any State from making and enforcing laws in furtherance of the purposes of this Act, pro- hibiting oF regulating the admission into that State of insects from a foreign country. Sec. 4. That any person, company, or corporation who shall knowingly violate the provisions of section one of this Act shall, for each offense, be fined, upon conviction thereof, not more than five thousand dollars or imprisoned at hard labor not more than five years, or both, at the discretion of the court. (33 Stat. L., 1270.) QUARANTINES OF THE SEVERAL STATES. Quarantines designed to prevent the importation of the boll weevil are now in force in the following States and Territories: Alabama, California, Georgia, Louisiana, Mississippi, North Carolina, Okla- LEGAL RESTRICTIONS. 165 homa, Porto Rico, South Carolina, Tennessee, and Texas. ‘They are directed against all infested counties and States, as well as against all counties which may become infested in the future. ‘The following pages give the substance of the present restrictions. or further particulars the quarantine oflicers of the several States should be addressed directly. Alabama.—The present quarantine regulations in Alabama were promulgated by the Alabama State board of horticulture on April 4, 1911.. The quarantine applies to cotton seed, seed cotton, hulls, seed-cotton and cottonseed sacks (which had been used), cotton- pickers’ sacks, and corn in the shuck. Importation of these articles into uninfested territory from infested territory, or from any point situated within 20 miles of the area known to be infested, is pro- hibited. However, between January 15 and July 15 shipments of these articles originating within or ginned within a zone 20 miles in length immediately adjoining the infested territory may be made to points not more than 40 miles outside of the line of infestation. Between October 1 and June 30 shipments of Spanish moss, baled or unbaled, originating in infested territory, are prohibited from entering or passing through uninfested parts of the State. Cotton lint (loose, baled, flat, or compressed) originating in infested locali- ties is prohibited except durmg the months of June, July, and August. The shipment of household goods is prohibited unless accompanied by an affidavit attached to the waybill to the effect that the shipment contains no cotton, cotton seed, seed cotton, hulls, seed-cotton and cottonseed sacks, cotton-pickers’ sacks, corn in the shuck, or loose Spanish moss, except that in shipments of household goods made during the months of July, August, and oe corn shucks or Spanish moss may be used for packing. shipments of quarantined articles must be made in tightly closed box cars. No person except the entomologist. of the State board of horticulture and his deputies is allowed to have in possession outside of the weevil-infested territory any live stages of the boll weevil. The penalty provided is a fine of from $100 to $500. Califorma.—tin California the boll-weevil quarantine is in the form of an order issued by the State commissioner of agriculture on April 23, 1908. This provides that all cotton seed shipped into California shall be consigned through one of the State deputy com- missioners of horticulture. These shipments shall be fumigated with carbon bisulphid for a period of 24 hours by a deputy com- missioner. Deputy commissioners are located at El Centro, San Bernardino, Riverside, Los Angeles, and San Diego. Florida.—The restrictions in effect are authorized by a statute passed in 1911 which established the office of inspector of nursery stock. Dr. E. W. Berger, Gainesville, is the present inspector. Georgia.—Previous to August 15, 1904, the Georgia State board of entomology had authority, by virtue of the legislative act which created it, to enact such regulations as it deemed necessary to pre- vent the introduction or dissemination of injurious crop pests or diseases. On August 28, 1903, this board adopted a regulation prohibiting the introduction of cotton seed from Texas except under a certificate from an authorized State or Government entomologist stating that the seed had been fumigated in such manner as to kill any stage of boll weevils which might be contained therein. On 166 THE MEXICAN COTTON-BOLL WEEVIL. August 15, 1904, an act of the General Assembly of the State of Georgia was approved, but further amended August 23, 1905, whereby cotton seed, seed cotton, cottonseed hulls, or cotton lint in bales or loose, corn in the husk, or all material, including house- hold goods packed in any of the above quarantined products, are prohibited from being brought into the State except when there is attached thereto a certificate signed by an authorized State or Government entomologist to the effect that said material was grown in and was shipped from a point where, by actual inspection, the Mexican cotton-boll weevil was not found to exist. Through ship- ments of quarantined articles may be made in cars which must be tightly closed, and no unloading is allowed during transit through the State. No common carrier shall use for bedding or feed for live stock any of the quarantined articles when the shipments originate in regions infested with the boll weevil. Mr. E. L. Worsham, capitol, Atlanta, is the present quarantine official in Georgia. Louisiana.—The State entomologist of Louisiana is, by a law passed December 15, 1903, empowered to quarantine against the cotton- boll weevil whenever it seems advisable. At present the State is entirely infested, but if in the future portions of the State should be freed the entomologist is fully empowered to restrict dangerous ship- ments into such portions. Mr. J. B. Garrett, Baton Rouge, La., is the quarantine officer of this State. Mississippi.—The State legislature in 1908 passed a law giving the entomologist of the experiment station considerable authority in regard to the quarantines against the boll weevil. As only part of the State is infested, and it may be possible to save certain portions several years of injury, the rules established in 1904 should be con- sidered in force as restricting shipments into uninfested counties. An absolute quarantine is established against cotton seed, seed cotton, hulls, seed-cotton and cottonseed sacks (which have been used), cotton-pickers’ sacks, corn in the shuck, unsacked corn, unsacked oats, unsacked wheat, and unsacked cowpeas from the infested terri- tory. Through shipments of quarantined articles must be in tightly closed ears, which must not be unloaded while in transit through the State. Household goods to be shipped from infested territory into uninfested parts of the State of Mississippi must be accompanied by an affidavit to the effect that no quarantined articles are contained as packing or otherwise in the shipment. _ Baled cotton can be shipped into the uninfested parts of the State only in tightly closed cars. Prof. R. W. Harned, Agricultural College, Miss., is the quarantine oflicer of this State. North Carolina.—By virtue of authority from the State legislature to prevent the importation of crop pests, the North Carolina Crop Pest Commission early in 1904 adopted rules establishing a quarantine against all localities where the Mexican cotton-boll weevil is known to exist. The quarantine was absolute and applied to cotton, cotton seed, cottonseed meal, cottonseed hulls, hay, oats, corn, rice, straw, rine samme ge other grain or material likely to harbor any stage of the MOLL WeeVLIL, | LEGAL RESTRICTIONS. 167 The rules published in July, 1910, are reproduced verbatim: REGULATION No. 15. No transportation company, common carrier, or agent thereof, shall bring into North Carolina any shipment of seed cotton or cotton-seed hulls origi- nating at any point in the States of Texas, Louisiana, Mississippi, Oklahoma and Alabama. And this shall likewise apply to other States when the boll weevil shall be determined to be established within their borders. Rea@utation No. 16. Shipments of cotton destined to any points in North Carolina and which originate at any point within the States of Texas, Louisiana, Mississippi, Oklahoma, Arkansas and Alabama, or other States that may hereafter become infested with cotton boll weevil, shall only be in hard compressed bales. If shipped in any other form, it is declared to be a public nuisance and is liable to seizure by the Board of Agriculture or its agents. Reeutation No. 17. Any shipment of cotton seed which originates at any point in Texas, Louisiana, Mississippi, Oklahoma, Arkansas or Alabama, and which is des- tined to any point in North Carolina, can be accepted for transportation only if it shall have attached to the bill of lading a certificate or statement signed by a duly authorized State or Government Entomologist stating that the point from which said shipment originates is a locality not known to be in the area of the boll weevil infection. ReEGuLATION No. 18. If any shipment of seed cotton, cotton-seed hulls, cotton, or cotton seed not in accordance with these regulations be presented to any transporta- tion company, common carrier, or agent thereof, for shipment to or delivery at any point within this State, same shall be refused, and the case shall be reported to the North Carolina State Department of Agriculture, at Raleigh, giving the name and address of the consignor and of the consignee. Prof. Franklin Sherman, jr., Raleigh, N. C., is the quarantine officer in this State. Oklahoma.—By virtue of rules and regulations issued by the State entomologist in accordance with the laws of the State, shipments of cotton seed, cottonseed hulls, seed-cotton and cottonseed sacks, cotton-pickers’ sacks, and corn in theshuck are prohibited from infested territory into uninfested territory. In the same manner household goods are prohibited unless accompanied by a certificate that no quarantined material is contained therein. Through shipments of quarantined articles shall be made in tightly closed box cars and shall not be unloaded while in transit through the State. Shipments of baled cotton into uninfested parts shall be made in tightly closed box cars. No common carrier shall use for bedding or feed for live stock any of the quarantined articles which may have originated in infested territory. All persons are expressly forbidden to send live weevils in any stage to any point in or outside of the State, either by mail, express, or otherwise. Prof. C. EK. Sanborn, Stillwater, Okla., is the quarantine agent for this State. Porto Rico.—By legislative act no cotton seed, seed cotton, cotton lint, loose or in bales, shall be brought into the island of Porto Rico, from any State or county whatsoever without being accompanied by the certificate of a duly authorized State or Federal entomologist that the shipment originated in a locality where, by actual inspection of such official or his agent, the boll weevil was not found to exist. Shipments not so certified are liable to seizure and destruction. Punishment is provided for in section 16 of the Penal Code of Porto Rico of 1902. The governor of the island has direct control over the enforcement of this law. South Carolina.—In South Carolina the quarantine regulations are entirely embodied in the laws of the State, and consequently not so readily modified to conform with the changed conditions and a better understanding of the methods of dissemination of the boll weevil as 168 THE MEXICAN COTTON-BOLL WEEVIL. is the case when authority to promulgate rules and regulations is invested in a commission or in the State entomologist. The law established to guard against the introduction of the Mexican boll weevil into the State of South Carolina was approved on February 25. 1904. The commodities quarantined against were cotton seed, oats, and prairie hay, shipped directly or indirectly from infested points in the State of Texas. Prof. A. F. Conradi, Clemson College, S. C., can furnish information concerning the interpretation of the State law. Tennessee.—In compliance with the requirements of an act of the General Assembly of the State of Tennessee (S. B. No. 442, chap. 466), approved April 17, 1905, entitled ‘An act to create aState entomologist and plant pathologist,” etc., the State board of entomology, estab- lished by said act, announced the following rules and regulations under date of December 31, 1910. (a) No cotton lint (loose, baled, flat, or compressed), cotton seed, seed cotton, cotton-seed hulls, seed-cotton or cotton-seed sacks (which have been used), or corn in the shuck, shall be shipped into Tennessee from the infested territory of Texas, Okla- homa, Louisiana, Arkansas and Mississippi. (b) Shipments of household goods from infested areas of above named States shall not be admitted into Tennessee unless accompanied by an affidavit attached to the way-bill to the effect that the shipment contains no cotton lint, cotton seed, seed cotton, cotton-seed hulls, seed-cotton or cotton-seed sacks, or corn in the shuck. (c) It shall be unlawful for anyone in Tennessee to have in his possession live Mexi- can cotton boll weevils. The public is urged to recognize the danger of introducing unwittingly live boll weevils for inspection, observation, or experiment. Mr. G. M. Bentley, Knoxville, Tenn., is the officer in this State. Texas.—In accordance with an act of the State legislature, to pre- vent the spread and dissemination of injurious insects, the commis- sioner of agriculture designated the boll weevil as such an insect to be quarantined. ‘This ruling in the act makes it illegal to ship seed cot- ton or cotton seed, or any other article which might carry the boll weevil from an infested county to an uninfested county. Mr. Ed. R. Kone, Austin, Tex., is the State officer charged with quarantine enforcement. Regulations of foreign governments.—The Governments of Egypt, Peru, and India have established an injunction against the importa- tion of American cotton seed originating in the infested localities. In all cases, however, it can be arranged to have shipments cleared in case they are accompanied by certificates of fumigation by a com- petent authority. THE MEXICAN COTTON-BOLL WEEVIL. 169 BIBLIOGRAPHY. This bibliography includes only the more important writings which have been published in permanent form. In the preliminary part of this bibliography a special synopsis is given of the contents of pub- ications, more particularly to outline the history of the cultural method now recognized as of supreme importance in the control of the boll weevil. No attempt is made to give a synopsis of the later titles. For a complete annotated bibliography see Circular No. 140, Bureau of Entomology. 1843. Boneman, C. H.—Genera et species Curculionidum cum synonymia hujus familiz ed. C.J. Schoénherr, vol. 5, pt. 2, pp. 232-233. The original description of Anthonomus grandis. 1871. Surrrian, E.—Verzeichniss der von Dr. Gundlach auf der Insel Cuba gesam- melten Riisselkafer. oj. ss Soe eee 145 eMemies - bs. SPE ee ON SE pes Re ene 136-145 insects mistaken. theretor: 2 oes e sere ne ches se ee 29-30 Intentional: transportation os 2 eset re ee 94 invasion of Alabama: = sce eee. ss a eee eee eee 19 Arkansas: 62% 2c pe: ts Se oe re 19 Plorida: 2120) Ghirst oe eer ee ee ees eee 20 Lowisianacs 228 cae een oo eee ee 18 Mississippi: -.--.---: LS ON eee eee ee erin A ila ae 19 Oklahoma: - 22022220 ce eee Ces Tee eee eee ee 19 POXASs. 152 2. SEE Eee eee ee ee ee ae 16 larva, description: =. - =e 7.c SS: Sh cee ee ee ee 33-34 duration of stages. {soe eee ee ee ee eee 66 food habits... 323222... 3/22... te ee eee eae eee 65 eToWUne 2c Scc tees st eee cee ee eee 65 MOlt8 22 ~ cath ok Bee Oe ee Oe eee ee 66 life cycles. 22.2 's. Pate tei See Pee eee Se ee ee ee 69-74 average duration. 23525) 3S e oe eee ee eae eee 69 in hanging SQUares =... AE eRe A ee 73 variations due to location of dev eloping staget:- 222 --. 69 BOR one Cee Se ee eee ee 69 tem perafure ss. 20 ne 2 eee eee (Oia time of falling of infested squares. . - - - 69-70 in bolls: +224... hates ae eee Se ee eee 72 miscellaneous) 25:20: see Ree ee eee ee 72-13 history;:summary.-2j0s.. << oe eee ee 32-33 losses:due thereto 222% <<. 224 eee eee Ree 21-26 compensation thereion! 7) Ares ome eee 26-27 indirect; due*thereto: : : 3552s a eee 26 mortality by sections: 65-5 eee ee ee ee 119-120 due to ‘heat’and-dryness-s e-ce5- 524 ao 122-124 in-all classes of cotton forms. -=<--5s2-2-4264- seen 118-120 natural controls -22.-2ti23525 Se ge 118-146 effect of defoliation of cotton! #245" > a) seas 20 OFIPIN <7... 2 ste ee bt oh. = Ree Rk oie eee ene ee 15-20 OV viposition, BCE wi oes as te ae eee ee 56-98 activity at various times of day: ) See os eee 30 mistaken for bolloweeval e : ao. ee a oe ee ee 30 Chat, yellow-breasted. (See Icteria virens.) Chaulhognathus spp:, enemies of boll weevil... --- = 3-52 2 137 Chickadee, Carolina. (See Penthestes carolinensis.) China-berries attacked’ by.-Arxcerus fascvculatust. oe Ace Bae Se ee 30 Chondestes grammacus, enemy of boll weevil. -- 225. 2. 7. ssa era] eee 146 Chordeiles mrginianus, enemy of boll-weeval. -— 232-3 een ee 146 Climate; factor m-boll=weevilicontrolo ss ss oo ee eee ee 120-132 mortality: 5 ekg hope = ake 2 ee ge ue eee ree 120-132 Climatic conditions, factor in boll-weevil controls. 225...2.--. 2.222422. 120-132 influences on vitality and activities of boll weevil..............--- 121-122 Cocklebur. (See Xanthium.) Coffee beans. attacked by Arzcerus fasciculatus-.---=2- 2p | ee ee 30 bean weevil. (See Arxcerus fasciculatus.) Cold, .effection* boll. weevil... 5.2. 2oe cece. es Se eee ee eee eee 19, 28 Colinus wrginianus, enemy of boll weevil: . 2 2s ee eee eee 146 Colors, attractiveness to boll: weevil ee a ee 43 Conotrachelus elegans attacks galls and nuts of pecan...--....---------------- 30 mistaken for-boll weevil! 542-44) ee 30 ermaceus mistaken for, boll weevil=-2 3-22-2642 ee ee 30 leucophxatus attacks stems of careless weed (Euphorbia)....---- 30 mistaken for boll weewiles 3323. eS eee eee 30 naso attacks acormmss.3¢ 352) ces ee ee ee ee 30 mistaken: for’ boll weevils 22 00 1 ee ee eee ee 30 nenuphar (see also Plum curculio). attacks fruit of plums and peaches...-:.....--..2.-25-- 30 mistaken for bolliweevale= oe oe eee ee 30 Convolvulus repens tested as food plant of boll weevil.........-.-------------- 32 Cordyceps, fungous enemy of boll weevilu..2 2 .------<2 42.5254 4--- 20s eee 136 Corn, duration of life of boll weevils fed thereon..................----------- 48 Cornstalks, hibernation shelter for boll weevil...............-.-.-----,------ 101 Cotton, American Upland, susceptibility to boll-weevil attack......-.....-..-- 45, 46 baled, factor in dissemination of boll weevile «2.4... e-~ 55 oo ee 93 bolls, duration of life of boll weevils fed thereon.................-.--- 49 effect of feedine by boll’ weeval thereons----- oe ee eee 45 old, attacked by Arscerus fasceulatuses 24. eee ee 30 pendent, indirect effect on boll weevil............-.--.-------- 135 with thick walls, effect.on boll weevil....---1/:--.---..---- 2. - 136 boll weevil. (See Boll weevil.) caterpillar. (See Alabama argillacea and Leaf worm.) Cuban, susceptibility to boll-weevil attack.................-....--..-- 45, 46 destruction of stalks as a means of boll-weevil repression.....--.---- 157-158 determinate growth, effect on boll weevil.......2-0-2t22---23-----0 nt 135 early bearing, effect. on boll:weevali._..- = - e eeee 135 maturing varieties as a means of boll-weevil repression-.-.-.--- 160-161 planting as a means of boll-weevil repression.......-.--------- 160-161 Egyptian, susceptibility to boll-weevil attack.................-------- 45. 46 fall destruction of stalks in relation to survival of boll weevil from hiber- . NAMON oes oa. wk ee eee wee ee ee ee 111-112 fertilization as an aid to boll-weevil repression............---------- 160-161 flowers attacked by Echthetopyga gossypii in Philippines. ......---.-.--- 30 hy. . INDEX, 188 | i Page ‘ Cotton, foliage, duration of life of boll weevils fed thereon. ................. 49 HOQCR TMAH Ol ALOOQILO, NGILIGCed= J cits Le CONE Aho ces 15 ATE LONLONUUS QUATGCUSEN Miah. Fa Wee te ACO Ph Ry ae NECN) 1-175 DESUNGU SHR REEMA corti) 5. BIAS tS Serta ad ata Oe 30 FAME CIRUOIUS COT ULRIS eG SAM oMk SAD CELL WaT UA BS A Ca 30 ; CRAIMOM ENS LILEUS USO Ae ita et SEN ENE ea QIN NE 30 HECHT CLODY GANG OSSUPUle sae yee es ae, pe Se 30 | TLCUIOURTSOBSOLEL IN ERO Ne)! Gk Re Bic). eS ogi 15 hare stalics.eltect.on.boll.weevil... 28.2. 9222 22205 Ye Le 135 imVolerd bracts ehect on, bolliweeviles..22% 20s) Re ee a tt 136 Sine enast plant ol pollweevalvin Guba uot. 22. 2.2.2.2. ce. 16, 31 “‘loose.”? (See Gossypium brasiliense.) nectanwncinecs ettect:on boll weevil... 226.% bau e ie 22 ee 135 AEST LOOM Wd GET CUSHPEIICELLUS se valye cranial Ste. SNIP aly Le 30 DUCTUS ery ae ec AOR ERE APSO | tA ABE 30 picking of squares as a means of boll-weevil repression................. 161 planting early as a means of boll-weevil repression.................- 160-161 restriction an impracticable means of boll-weevil repression. . 156-157 time, effect on longevity of boll weevils....................-: 116 DlaMinspLoluTerstion, elect on bollsweevil:<* -2...j2.-2.00)2224..:--- 132-135 cimuemunesimimcal tonbollweevilge as hese eek as So nes - 135-136 FeLenuOM Oninuib. eect, on boll weevil... 2502.05 ds. eee 136 Sea Island, susceptibility to boll-weevil attack......................- 45, 46 Reco mMaAconmneGissemination,of bollsweevil:s. 2225252. . hs oss Sse 92-93 shallow cultivation as a means of boll-weevil repression............-. 160-161 squares attacked by Anthonomus vestitus in Peru..........---...------ 30 Chalcodenm us nes yes nue ath Nh) a Awa ean eye ail buntaleettect, on, boll weevalliacs 8.5 2)) O8ss ue oe a 147-149 duration of life of boll weevils fed thereon.....-.....-.-.--..-- 49 effect of feeding of boll weevil thereon....................--.- 44-45 picking, as a means of boll-weevil repression...........-.----- 161 square weevil, Peruvian. (See Anthonomus vestitus.) stalks as hibernation shelter for boll weevil. .............-..-.-.----- 100 destruction in fall as a means of boll-weevil repression. .....-- 111-112 SHemispaneKmeGn yea WUUVOWS COTMULULS . a5 < se. a. Sen viele Jia =< actos see 30 LOMEChOpeasnaMectea Dyn bolliweevilile, hols eie N28 oe lee 81-83 PRoemNOstED amtRorrDOllweevale. suet Say aan hl ine esis. feu 31 ‘““wild.’? (See Gossypium brasiliense.) Cottonseed meal, nonattractiveness to boll weevil. .........--.------.------- 42 ollassoatiavalnst boll weevil, futility o. 2225 ss5 oes. 2k a. oe 153 Cottonwood catkins attacked by Dorytomus mucidus...........-------------- 30 Cowbird. (See Molothrus ater.) Cowpea curculio (see also Chalcodermus xneus). MOR LOME nA NOMING GlOOOSA= rete 2 tM Ns Nees 0s cecr ei ris eee 142 ROOGEDLAMLLOl CALCODeT IMS CENEUS). ole jak 45 Aspaja\2 = be iste wie tlocllfs eee es = - 30 pod weevil. (See Cowpea curculio and Chalcodermus xneus.) Cremastogaster lineolata leviuscula clara, enemy of boll weevil. .-.-.---------- 139 Croton ost polamioteanthonomus albopilosus.. 212355202. 6.222 eee 2 Fee 30 Onumociivaneristaca. enemynolboll weevils <2. 528 2b e sete. dos. ee ee ee 146 DWendrarca xsuuonencmay, of bollyweevils ot. 2. sass 2. Sess bee ees 146 COnowupe-cenemy. Of DOllweevall {5.2.8 5ecies Sk ee ee Jokes 2 146 Desmoris constrictus attacks seed of sunflower (Helianthus)...-.-.-...-.------- 30 MMB ken MOroOll weevilse sees: oe eis Ne Le Sco hele 30 scapalis attacks flower heads of broad-leaved gum plant (Sideranthus). - 30 mistaken for boll weevil. ....-.. ieee eI AS os BS IRE 30 Dewberry, Host plantiol Anthonomus signatus.2. cs. o.\- 2 ).2-- 222292225 55---- 30 Dickcissel. (See Spiza americana.) Dorymurmes pyramicus, enemy of boll weevil. ..).-...<-- 5-2. 2-5---2555+2-+-- 140 Flavus enemy. at bolliweevill. = sepa eee se oe ee 140 Dorytomus mucidus attacks cottonwood catkins........-.-.----------+----+-+--- 30 muistakenttonmbolliaweewils acing 122 26 ce tiseicle a sels oe l= = 30 Drouchirenectson boll weevil. -(. 0.222. -cob bes fe ee ees ee eat Se See 16 Mnynesssetteet om boll weevil (2.2. -t29-2546- 2.2 22a 2-2 te) in 22 ee 28 factor in boll-weevil mortality............--------++-----+--:----- 122-124 Eciton (Acamatus) commutatus, enemy of boll weevil....-...----------------- 139 Ectatomma tuberculatum, enemy of boll weevil....-..----------------------- 139 Ecthetopyga gossypii feeds in cotton flowers in Philippines.........--. 30 s 184 THE MEXICAN COTTON-BOLL WEEVIL. Empidonax minimus, enemy of boll weevil......-..-..-.------------- tet ae: trailli alnorum, enemy of boll weevil.......--:----..2.-1-:2---- Pe Ennyomma globosa, enemv of boll weevil inde: See ee ; cowpea curculio (Chalcodermus xneus).....--.--- : Epiczrus imbricatus mistaken for boll weevil ...2-.;-2-2-25-5-------------=--= : Euphagus carolinus, enemy of boll weevils_-cce Seseeeueeee - = eee cyanocephalus, enemy of boll weevils. <20.2224oe = 2 oe Euphorbia stems attacked by Conotrachelus leucophxatus........------.------- Eurytoma sp., enemy of boil weevil........----- Sick. BS een ee tylodermatis, artificial increase of effectiveness as boll-weevil parasite. enemy of boll weevils. ')-5.1:: fos le eee eee Evarthrus sodalis, enemy of boll weevil .-.--.:--------2+.-+--------- Pro) Reameiitey sp., enemy of boll weevil-.tieesee (icek a5. Se as Pe eee Excelsior, duration of life of hibernated boll weevils fed thereon...........- False indigo. (See Baptisia.) Farm hands, movement, factors in dissemination of boll weevil.............-- Faunal zone limitations upon bolk weevil ..n::) A =: ae FE ee Flooding; effects. upon, bollswéevilow.s sta: eee Ae eee 131-132- Flycatcher, alder. (See Empidonaz trailli alnorum.) crested. (See Myiarchus crinitus.) least. (See Empidonaxr minimus.) olive-sided. (See Nuttallornis borealis.) scissor-tailed. (See Muscivora forficaia.) Forelius maccooki, enemy of boll weevalicz! 22-4 222 Sse ee Formica pallidifulva, enemy of boll weevil. .~.-.--2.---.-22...--.-.-2-12---- subpolita perpilosa, enemy of boll weevil... 2.-22. 12-225... 2252 Geothlypis trichas, enemy of boll weevils. essesesee yy: = Gerzus penacellus mistaken for boll weenilss.2 Bet Sse ee ee visits. cotton mettars: 29% 21.6. 35.cil) Peete ee ee eee picumnus mistaken for boll weevil ............-..-------...-- = Soe visits cotton nectarse-¢ uf Loe Bee ee Gerstxeckeria nobilis attacks joints of prickly pear.....-....-....-...-...----.- mistaken for bell weevils: 21/522 tee See ee Ginning machinery used in repression of boll weevil. ............-......-.-- 152-153 Gossypium (see also Cotton). | brasiliense, food plant of bolliweevil ius. 24: D3i58 se See 16, 31 Grackle, bronzed. (See Quiscalus q. xneus.) ereat-tailed. (See Megaquiscalus major macrourus.) Guatemalan ant. (See Ectatomma tuberculatum. ) Gum plant, broad-leaved. (See Sideranthus. ) Habrocytus piercer, enemy of bollaveevils 2.2234 u:) bate Se eee Hay, duration of life of boll weevils fed thereon... ..22:5..322)02 . 222 5. 2 Heat, factor in boll-weevil mortality: 25.-1.42.4 i Ae eee 122-124 Helianthus (see also Sunflower). annuus, tested as food plant of boll weevil. ..........-..-.+------ seed attacked by Desmoris constrictus Heliothis obsoleta an enemy of cotton... is: 9-03 1522, ee Hibiscus africanus, buds, duration of life of boll weevils fed thereon.--...--.--- tested.as food plant ofiboll weevil: 3322228 - 0552s eee 31, 3: buds, Japanese. duration of life of boll weevils fed thereon. ......--- esculentus tested as food plant of boll -weevil2....0221 2.12 212_---..- leaf, duration of life of boll weevils fed thereon ...........-..------- manihot tested as food plant of boll weevil.........- foo ee ee militaris, buds, duration of life of boll weevils fed thereon .......---- tested as food plant of boll weevil............-.----.------ 31, 32 moscheutos, buds, duration of life of boll weevils fed thereon........-- tested as food plant of boll weevilzc..3225. 2222. - ee 31,3 vesicarius tested as food plant of boll weevil.............-----.------ 31, 32 Hirundo erythrogastra, enemy of boll weevil Hollyhock (see also Althxa sp.). buds, duration of life of boll weevils fed thereon.........-.:------ Honey, attractiveness to boll weevil....................- i iiod i oh ee Sao Hydnocera pallipennis, enemy of boll weevil. .........-...--------+-----+---- pubescens, enemy of boll weevil -2:.0 2.25 1229 eee Hylobius pales attacks pine. bark-2.._/.- 2. Jo 1, BE a ee mistaken for boll weevil INDEX. 185 Page Uctenia- viens; Srremny Gh poll wmeGuietest. 5 em ee Se ee ka 146 dcterws bullock enemy mi DON Weewihe a2 5.5 dat SE oe aaa ale mines a alt nein oy 146 Galbicht. ENemmiveoc MOM WOCmMl nile A See e e ES i ie wl areal dm oo .6) = 146 hypomelas, enemy ob Doll weevil Mn mbe. 2/5. oes m - Fale jd Srna w'e e 145 SDUTUS - EleninvrOlr OOUMWOG NE Raker aso So oe eel on Bie atin oe 146 Indigo, false. (See Baptisia.) Inseet;, Gnemies OF WM VeC Un —— sot a eae eee io ME ayaa ae ge <= = 136-145 Insechicides ised aeaimst, boll weewdl. marc. 5. atin sowie, 5 ao wisictnlBayape,= niet) 149-151 Irdomiprnnenianaltis Enea, Ol MOll Mee UN eae Ss oe eas ioiala cE het me cieiel ee aie « 140 PLE. Ol MMOMURMUCEHUMUAMUNS es (0 Sia) 2 ciaycrats 2 AL wie ote ynitie ee = = 140 oer GMeMA VIO WOVE. cee cies 146 Veco nja(s oles es aiakele e whemie = 140 RPTL OT UT IUCR GIES ore oh icy ye nt eke ae ee 140 IMGHOMORTUATE PROT GOTULS 20 psyco c12 es 2e ohayenrinte 2 140 SQUERODSTSIGOMUINGLO ee Ae eo. beige chs 140 Janovitch. (See Cotton, Egyptian.) ‘‘Kelep.’’ (See Ectatomma tuberculatum.) Killdeer. (See Oxyechus vociferus.) Kingbird. (See Tyrannus tyrannus.) Lantus udowcumussenemy ot boll weevil: >. o2c.542 2 55. 8 oe bee cee 146 Lariophagusiieaanus. enemy-of, boll, weevil... - 3. 2-620. seek bene eieiet ee - 142 Leaf worm (see also Alabama argillacea). . edect on deiokation on boll) weevil...) 22-2245... -2ee-2 2-5-2 ae 20 Live oak acorns attacked by Balaninus victoriensis....:....--2--2---+2--0-22-+ 30 Lixus scrobicollis attacks stems of ragweed (Ambrosia)...........-.-.--------- 30 PSR TRCUgOT DOMAWCE WIN 20M «hu ccd ier eres. fb ee ee es 30 Machinenyausedtaeammst, boll weevils.) 3. Soe Sachs says beet ene 151-153 Macrocheiesme sae cenem.y. of boll weevil 35 cheer ere aera eit oe wp ee ae 137 Mallow, purple, host plantiof Anthonomus fulvus...2.. .--+25--s-0c2--200-~ 2 <5 30 trailing. (See Callirhoe.) Martin, purple. (See Progne subis.) Meadowlark. (See Sturnella magna. western. (See Sturnella neglecta.) Megaquiscalus major macrourus, enemy of boll weevil....-........----------- 146 Melospiza georgiana, enemy of boll weevil....-...-..---2-.--:-.------ ees 146 Microbraconmeti@an enemy of boll weevil. .284. foo. .2 oe ios sees ae ok 142 Microdontomerus anthonom:, enemy of boil weevil...-.....-...-...-..--+----- 141 Mimuspolyglotasvenemy of, boll weeviln 502220002350. habe cee fe 146 Mineralipaintminbiingacainst bollvweeval: «2. 282060. 9 jieal es Se 6. oe: 153 Mit afifi. (See Cotton, Egyptian.) Mockingbird. (See Mimus polyglottos.) Molasses, nonamnaethveness to boll: weevil o-.28 kena. be. Se ech. le ee 43 Molothrustonmgenempyompoll; weevil. i -. us0 6 Sess sey ee ene 146 Monomer mimunum, enemy. of boll weevils... 0.2. 2cie2 acs 2.2 Se- ase s-~ 140 peoneanis, eaemiy of bolleweevalin. 2052). 006 eee 140 LON AO LAOMULMOMINU MUS 05.25.25. ee. ooo 140 Morning glory pods attacked by Rhyssematus palmacollis................--.-+- 30 Mascara jorediamenemy orboll weevils 2) ol) oe ee eet 146 Myorchussermmius ecneniy, ofsboll weevil 22 ay. 2. ee Se ke 146 Mipophasim-rncmacnemysompolnweenileet ate ere ec ke 142 Nonnusiijemaris ene tnyaorbolb weevil. peste 2 oo eel eek kk 146 Nighthawk. (See Chordeiles virginianus.) Nutiallonuismogcousseuemiyron boll weenwileastey 6 <.... oc ce See ee eee ee 146 Oats, duration of life of boll weevils fed thereon......................2-..-4- 48 Okra buds, duration of life of boll weevils fed thereon......................-. 48 leaf, duration of life of boll weevils fed thereon................--.----2- 48 Leshed: AS ukGoed sill amie OL DOMAweevalisiis wie oo oe oe bbe ede bebe 32 Opatriits mots ,etemis OLmOlliwee vile 225859. 6 ose Ln cee nae ee cance eee 138 Oriole, Baltimore. (See Icterus galbula.) Bullock. (See Icterus bullocki.) Cuban. (See Icterus hypomelas.) orchard. (See Icterus spurius.) OxyechusmocHermsnenemiy. of bollwmeevil co. 5 (5 a2 ob. eee coin ss Bese cee ee 146 Pachylobius picivorus attacks pine branches and bark....................----- 30 MP AKEM OE VOOM nee Val sj 2xtuy ye oath ye ek a kh 30 Parasites siactoram, conirol of WON weevil. a. hs0 oss ooh 2 Se Se ee 120 Paris greeussiuaiieararmet, DoUbee vale ose pers ok wc erceeid os oe haus Sociee cmd 154 KS Be Prev a ——-—... -—. hla. | ee) 186 THE MEXICAN COTTON-BOLL WEEVIL. Page. Passerculus sandwichensis, enemy of boll weevil................--.------------ 146 Passerella thiaca, enemy of boll weevilwy.2 2 ee eee 146 Passerina ciris, enemy of boll weevil.- 3322.22 ee ee 146 Peaches attacked by Conotrachelus nenuphar..--_- = 2 eee ae ee 30 Pecan galls and nuts attacked by Conotrachelus elegans.................--.--- 30 Pediculoides sp., enemy. of boll weevil. 2+: ..2:- =. - 2-2 Lee ee 137 ventricosus, enemy of boll weevil. -2=22-25255 hase) ee 137 Penthestes carolinensis, enemy of boll weevil..........--...2..--1.-2222-2.122.- 146 Pepper, host plant of Anthonomus eugentt. =< =-2* 22s a ee 30 plants, futrlity-agamst boll weevil] ee ee ee ee 155 Perilampus sp.) enemy. ofboll:- weevil 2.2.7 32-2 en ee eee 141 Petrochelidon lunifrons, enemy of boll weevil..................-.------------- 146 Pheidole crassicornis, enemy of boll weeyilo ee aa ee ee eee 140 sp., near flavens, enemy of boll weevil...-............--..-- Leas 140 Phoebe. (See Sayornis phoebe.) Pigweed (see also Amaranthus spp.). duration of life of boll weevils fed thereon!::-----222252 22 222. ee 48 Pimpla sp., enemy- of boll weevil.:..-....22:2. 3) ee ee So 142 Pine bark attacked by Hylobwus:pales..-25 2222 ee eee 30 branches and bark attacked by Pachylobws picworus.........-..--.----- 30 Pissodes nemorensisoe =e eee oe) eee 30 Pipilo erythrophthalmus, enemy of boll weevil.................-.....-----.--- 146 Pipit, American. (See Anthus pensilvanicus.) Pissodes nemorensis, attacks pine branches and bark....--...--..---.-.------ 30 mistaken for: boll-weevile Ss ee eee 30 Plant control of boll weevil. ..::.0.2.2.2: -4 2+) eee ee 132-136 Plover, upland. (See Bartramia longicauda.) Plum curculio (see also Conotrachelus nenuphar). host of Sigalphus curculionis-: .- SS eee 142 Plums attacked by Conotrachelus nenuphar..-322 29. e ss eee 30 Powcetes gramineus, enemy of boll weevil. -....252 58 Sana ee 146 Precipitation, effect on date of beginning emergence from hibernation by boll weevil ins 20 2k GS as a 107-108 survival of hibernating boll weevils....-......-..--- 112-114 Predators, factor 1m: control of boll.weevilit 224 3342 ee ee ee 120 Prenolepis amparis, enemy of boll weevil: i. 22.232) ee 140 Prickly pear attacked by Gersteckerta-nobilis:.22. 28: Fae, ee 30 Progne subis, enemy. of boll weevil......2) 5 Liat ee 146 Proliferation, control of boll weevil thereby... - “98: 00252. ele ee 132-135 Pyrrhuloxia s. tecana, enemy of boll weevil.....- ASH Sh aes SS Page ree 146 Texan. (See Pyrrhulowia s. texana.) Quail. (See Colinus virginianus.) Quarantine against boll weevil by Alabama. :--.2..2:2.5.. 2.25.22 20. 2222220 165 Cailliforniake tJ. 2 Oh SE eee 165 BiG y Dib eee (et sae ee 168 Wloridaieek' A2k 5.4 is Ce Bee ea it eee 165 Georgia: soc ute: Ca erie Gs = aah pee 165-166 India...tf a2, $2 his Si ie, So ee 168 Louisiana-27¢ 20 :3)):6. bn ea ee 166 Mississip pice oe. sha. tease gift). ALS OS Brees 166 North Carolinasny Sanh) age) eee 166-167 Oklahoma #..3 20). :6. 27045. Swe eee 167 Pertis..s2) Sees Be) es 168 Porto Rico: 7. Lie ict Sie Ear ete ee 167 South Carolima ess.) ee Se es 167-168 Tennessee 22 4. Ja et ea ae eee 168 Texas..../272524.38)4 10 Shee ee ee 168 Quiscalus gq. eneus, enemy of boll weevil. .2i2-2.5 aes ae 146 Ragweed. (See Ambrosia.) Rainfall. (See Precipitation.) Rains ‘as agents in spread of boll weevil... ..... te) et a, 91 Xestriction of cotton planting now an impracticable means of boll weevil repres- Rhinchites mexicanus attacks rosebuds. 20 22h a ee ee eee 30 mistaken: for boll weevil Jb 82) ee ee eee 30 Rhyssematus palmacollis attacks morning glory pods............--------------+ 30 mustaken for boll weevil. *>. (2 eee 30 ee ee ee eae en are eed bee Gaeel| INDEX. 187 Page Rice, duration of life of hibernated boll weevils fed thereon.................. 48 mponariparia, enemy of boll weevili 2. 2.2.29. Sse). 2 eee... 146 Rosebuds attacked by Rhynchites mexicanus...........0.0.0520220222---2-22--- 3 Sage, wild. (See Croton.) magormisspnwoe,- enemy of boll weevil.222n.220. [2212.5 hie ie 146 Seed cotton, factor in dissemination of boll weevil....................----.---- 91-92 Shrike, loggerhead. (See Lanius ludovicianus.) miderantihus attacked by Desmorts scapalis:! 02101.) 25.2. AW Spb 30 sHoGuplus curcilionis, enemy of boll weevilii. ioe el ee ee eee 142 plum curculio (Conotrachelus nenuphar)..---- - 142 Solanum rostratum stalks attacked by Trichobaris tevana............-...------- 3 Solenopsis geminata diabola, enemy of boll weevil..........................-. 139-14 prey, ol Mmdomyrmen NUMISL A. ETS PAE a ie 140 movesta.-cnemy Or boll weeval 220! A220 SOU OS eel 2 ek 140 teranacenerm yor boll -weevallee . 821) Vb | a see) 140) Sorghum cane, duration of life of boll weevils fed thereon.................-.- 48 Spanish moss as hibernation shelter for boll weevil....................2....... 101 thistle. (See Solanum rostratum.) Sparrow, field. (See Spizella pusilla.) fox. (See Passerella iliaca.) lark. (See Chondestes grammacus.) savanna. (See Passerculus sandwichensis.) swamp: (See Melospiza georgiana.) vesper. (See Powcetes gramineus.) - white-throated. (See Zonotrichia albicollis.) SMa cespemenemy Or Doll weevil. -2 =. sah Me aD EE 141 S'piza americana, enemy of boll weevil...-.......--...------- UNS PS UNE AST 146 Spiecllaspusiia enemy of boll weeviliey.) ak eo Ores on PUD. tion 146 Sprayme-tiiilibyagaimst-boll weevil. 22 /8P 0a Ae VEG yey athe 153 Stogmomants tmoatarenemy, of bolliweevils-.. 32 s2522 22s 2 ee. oe oe sess 137 SUAKeCUEEMoeGevACeTOMGOLLOMS: io. cto ee 6 an lets aR Spiess oats = Scars Seen 158 Sirawlerny, host plantiof Anthonomus(signatus....s.22..-22-2--2--+---5--22- 30 Simnealamagnaenemy of Dolly weevils: - s.0ee ec. Yok 2 go oe 2. ele 8 146 mequectamenemiy~ou Doll weevil ix: oer aceboy te oe Se oe Seine de oe ee 146 Sugar nonatiractnveness to boll-weevils..- 2.4... 82 22s. yee eo oe ae ee ee 43 Sulphimeonimtilitveagamst boll weevil. +.) 2S ae bee oe See cece 153 Sunflower (see also Helianthus). duration or lite of; boll. weevils fed thereom=....-2225--.-.---.-.5--2- 48 Swallow, bank. (See Riparia riparia.) barn. (See Hirundo erythrogastra.) cliff. (See Petrochelidon lunifrons.) Temperature, effect upon date of beginning emergence from hibernation by Boll "wee ale anise gee Se Nee Sede det 107-108 entering bibemation ss. ..2-42 45555-5652 - 97-98 duration of egg stage of boll weevil.........-...---. 62-63 larval stage of boll weevil...............- 66 pupal stage of boll weevil................ 67-68 lifexeycleotbolliweeval sso. 2- fe 2 ease Geese cnee aoe 70-72 locomotion.otbolliwevally-s- ee pers see Seer 43-44 ovaposition of bolliweeviles s33220 $25.02. ae oe ORO survival of hibernating boll weevils..............- 112-114 fatalavariations\ dor bollsweevals Oy 4 fs. 22s Hee eee 129-131 HeLa TONS ELOLDOLsWECVALY oa ae eae a Sete as eyes) oe we 125-131 ZOMer Omactivity, tor boll weevall ype. Ss. 5 5-22 cos fe 2 eee ee 127 fatalityedlowers for bolliweeval: ..2...-2:..--.28-5.--5= 128-131 Upper; Hor Wolliwee vile n 4% 25 2).5< fans eee 126 ; hibermmationjyior bolluweewall:.226..2- 24-0202 2ssteee see 127-128 Uctrasticnussuunterd.,enem y oi, bolliweevil: ..)2:2. 0525252250 Seb eee ee: 142 Thistle, Spanish. (See Spanish thistle.) Thrasher, brown. (See Toxostoma rufum.) Uinomanesucwickvu;onemy Olbollweeval-. - to - 2-2. ee ie ao 146 Thryothorus vudovcianus, enemy of boll weevil. .........0.-.--~.2---2-------- 146 Tie vine, duration of life of boll weevils fed thereon........................- 48 Tillandsia usneoides. (See Spanish “moss. ) '¢ Titmouse, black-crested. (See Bxolophus atricristatus.) tufted. (See Bxolophus bicolor.) 188 THE MEXICAN COTTON-BOLL WEEVIL. Tobacco, futility against boll weevil. .....4.0.-2-b2:cec=ned Jame po-e eee stalks attacked by Trichobaris mucorediccew--<-h+ sass - eee eee ike Towhee. (See Pipilo erythrophthalmus.) Toxostoma rufum, enemy of boll weevil..............-.---.--------- ad -Ke Trapping at lights, futility against boll weevil...............-.--.-----.----- Trichobaris mucorea.attacks tobacco stalks.: §:. 3.2 t<2hs