Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. | ee ee ev-« ? is * T z ee ae A i a we ae oe Sis oe ~ ; i a tt ere yee t “4 os as gee ty = sons Ns oe BeSone - “ sen ie res ta) ; RS j i Bn Nai s EURO Oe gt ae erg Sine ; | ay t La} ee : s ee Ape fo ta oF | : U.S. DEPARTMENT OF AGRICULTURE, > BUREAD OF ENTOMOLOGY—BULLETIN No. 51. (0% HOWARD, Entomolagist. : THE MEXICAN COTTON BOLL WEEVIL: A Revision and Amplification of Bulletin 45, to Include the Most Important Obser- _ vations Made in 1904. = * PREPARED UNDER THE DIRECTION OF THE ENTOMOLOGIST ~ gos BY Ns tog aS W. D. HUNTER and W. E. HINDS, -» Wwe TEN Ay al Tits 5 hil 22 1. Oa" I} De ta (A 3 <= 4 qe . Vi} eaake E ihe = Y nal v; = XA : Ula Me Aer ey WS AG a WASHINGTON: GOVERNMENT PRINTING OFFICE. 1905. BUREAU OF ENTOMOLOGY. = | mee O. Howarp, J Entomologist and ae of Bureas ce : = = ee, ee Ged Be Manvarr, in charge of eupicninental field work. = : = oer Hest 992 5S CHITTENDEN, in charge of breeding experiments. Se ea ee : A. D. Hopxiys, in charge of forest insect investigations. === ae Ww. D. Hunter, in’ charge of cotton boll weevil investigations, == _ Frank Benton, in charge of apieultural investigations. ok M. Wenrster, in. charge of field-crop insect investigations, Bs ee 3 LL. ee im eae of deciduous fount insect inv estigations. = Paiologtats:. A 5 EN ee St ee eS Cuirron, Chief Ceo See en ; series =i. 8. G. Trrus, F. ©. Prarr, Aucust Buscx, Orro HEIpEmany, A, N Canam _ CURRIE, J. G.Sanvers,; FD. CouDEN, Assistants, ce, R. GC. Atruouss, W. F. Tasrer, Mary G. CHAMpNEY, A. se Tae rE cs Wo —f. A. Kevener,:Jesste E. Marks,’ gnagraphers: and. Clerks. Soe nS Crs oe ~ Lian L. Howensrer, Artist. ee ea TP ei eae eee x - | Mave ae Be ae : Wincs NEWELL, E. C Saxporx, E. S, Hany, Rk 0. Hows, eng in “4 _ boll weevil ees ; ee ; oe J. M. Ranxin, eae vee gE F Se en we imap inves ee GAL REBYES, W. J. PHILLIPS, engaged i field-crop insect investigations. — 2 2 _ Frep J OHNSON, 25 A. GIRAULT, J. = Brarie, engaged % MN a ee _tigations. see ek ee ae Soe aS oes ‘E. BL SASSCER, Student Assistants Se ae = ra PLATE lI. Bul. 51, Bureau of Entomology, U. S. Dept. of Agriculture. STAGES OF MEXICAN COTTON BOLL WEEVIL. 2, side view of adult; fig. 3, egg; fig. 4, spread—all (original). Fig. 1, Cotton boll weevil, back view of adult; fig. 2, side view of larva; fig. 5, ventral view of pupa; fig. 6, adult, with wings except fig. 3 enlarged to four diameters; fig. 3 enlarged to twelve diameters Cro Ea eivwiiNT Or AGRICULTURE, BUREAU OF ENTOMOLOGY—BULLETIN No. 51. L. O. HOWARD, Entomologist. THE MEXICAN COTTON BOLL WEEVIL: A Revision and Amplification of Bulletin 45, to Include the Most Important Obser- vations Made in 1904, PREPARED UNDER THE DIRECTION OF THE ENTOMOLOGIST BY W. D. HUNTER and W. E. HINDS. Ms zs TTA al ils Is e. sulle hf nfl ES i Mit): ts WASHINGTON: GOVERNMENT PRINTING OFFICE. UQOSE LETTERS OF TRANSMITTAL. To the Senate and House of Representatives: I transmit herewith, for the information of the Congress, a report on the Mexican cotton boll weevil. Your attention is respectfully invited to the accompanying letter of the Secretary of Agriculture recommending that at least 10,000 copies of this report be printed for the use of the Department of Agriculture, in addition to such num- ber as may be desired for the use of the Senate and House of Representatives. THEODORE ROOSEVELT. Tue Wuitr Housn, March 2, 1905. DEPARTMENT OF AGRICULTURE, OFFICE OF THE SECRETARY, Washington, D. C., March 2, 1905. Mr. PrestpEent: I have the honor to transmit herewith, for your information and that of the Congress of the United States, a bulletin entitled ‘* The Mexican Cotton Boll Weevil: A Revision and Amplifi- cation of Bulletin 45, to include the most Important Observations made in 1904,” prepared by Messrs. W. D. Hunter and W. E. Hinds, of this Department. This is an elaboration of a bulletin published a year ago, and of which an especial edition was ordered by Congress. In view of the popular interest felt in this subject in Texas, Louisiana, and other cotton-growing States, I respectfully recommend that at least 10,000 copies of this bulletin be printed for the use of this Department, in addition to the number which Congress may, in its wisdom, order for the use of members thereof. The preparation of the bulletin has been hastened as much as is pos- sible, consistent with accurate and careful work, and, while it is reeret- table that it could not have been completed at an earlier date, the urgency of its publication is such that it is my hope that you will see fit to urge Congress, before adjournment, to take the necessary steps to secure the publication of a sufficiently large edition. i have the honor to remain, Mr. President, Very respectfully, JAMES Wixson, Secretary. The PresipEnt. (3) - U. S. DeraARTMENT OF AGRICULTURE, BurREAU OF ENTOMOLOGY, Washington, D. C., March 1, 1905. Str: I have the honor to transmit herewith the manuscript, pre- pared under my direction by Messrs. W. D. Hunter and W. E. Hinds, special field agents of this Bureau, of an extended bulletin on the Mexican cotton boll weevil, which is a revision and amplification of Bulletin No. 45 and includes the results of the many important studies made during the season of 1904. It is so amplified and altered as to deserve independent publication. I therefore recommend that it be issued as Bulletin No. 51 of this Bureau. Respectfully, L. O. Howarp, Entomologist and Chief of Bureau. Hon. James WILson, Secretary of Agriculture. CONTE Nas: GemeralecomsiCerabiOrs ene Mee eee Ae eer Uae ere ese the | Pee ISLETS Lyra ye ppp pe ere ere ee LP Feat A Ma Bh A le ts Oa We Se HD ES GIVE TNC S Se me ae Son 2 cs aes wom tei a EL aan Sa Meraittoray athe Cle Caps eine ae re Crs Seed ee Say NI LO a Sie Nd Pe Saas Dishriloutiiommon tliaeroollweewale spe erk iN tee Ne cee ce ee ea JARS] HOCUS: 5S ies aes Beatie Dic AN Sa ae ang SS er sek IOS NSTI OT ONY eh eth Sie SS ges hes ae Cah ae eg a mane me, SDUUMOD RIAL SS bis aaa AS ts Sica Serene yea pity Ate kr en pede ea Ieee a Uae INNS Qe, 2 ass SS GSS OG BE A I tg ee eS ge nitoryomicudevelopment ates sos ass ehie as. go) hs Cae ee es DD UGALIOMPON ES OUSLATC eee ceo Nee eee ce CON EME ae Tice Bie Raat Hele tre Lain aes pene eee Nile RAE SITE SS aoe ta aera So ia ae Matebmexotcegestlandyoutside gins se cee 2 ee ee i Eating of eggs deposited outside --..-.-.---- Seep phi a NG Neate eek oO Rercentage oinecosutnatshatehnmss a seek ee ic ae ce EST seas viet oa ees oN tas oP eae net eer NL Le 5 WR EAS Lancs oe IN ONS ties a coil ll Ee Rn he aes SK Per gia ee IBEOCESSRON TNO CII ye ay ce I Sis ee ae LS ee cs en Ng Durahionvoirlarvalistag ep 2. eet ala Caen ree yay a) ieee dts pens as ees Fpakeceliisiiniely@ lis) cee, s ee Sem apr a a POM Vs eee ue EL JED OTA KO) Os ies ARS asc Se 2d SAR a gs A a ee papa er agus Ae Meg ARNE) OU OBI , Ss Bee rier e eas rae ere ee aa IPS ye aya Sra Sera a ee ee a CE Dunawongotapulpalestace se, 45% Wye se eee ee Lis fe hee See I ER ee a MISia es exclaim yee yee mene ee aes a SNA) Mae es athe mt one en wee BeTOTRe REM One li Cate CNet eae Gabe Ae, eevee Uae ci Sal py Bs ae J BIROOVRERS NGS): ie Bis Sey acl ss cas tae Oa oe aya ae Se Saal as Chancedaike raemenreemce= a tres neta eer <2 ee ee ere ie svar Descriotroneoliadullitpsmys wetness sats ee 2 Mees pl AN Fath ys Pas A SHAS ONE NELSON ISIS ae, I Sas Fa) Ae een ey 8 re Non ean eae een Relaionpotes(zertomood Supwlynee =. 455 22s wee Nn eu oak Wierodatmoteacliulitsyare tenes sinen ee een eruts Cala OR MO ha Secondaryacexualchandctensieeeeren ao see ee eS Se Sn i sees ERO POrGOMSNOlmi Meise ecm s ny 4 eee nis EN Fa i ek Duravronvol litenmpompsauanese ys pee Uae wl ee Leek yok ee Wuratioukotsiteronebollcralomess sewer ee ar es obs Duration omuteron cottonpleaves alone 225-0 225.2 es. 22 ee lh ee Duration of life with sweetened water and with molasses.........--- Duration et lite without food: put with water. 1.22.2 22..2.i2..22<2 Durawmengoiite withoutoodonnyaerooose2 =... 5225.4¢ 5382 Te 2 (Caio Oee Tesora s Saat I A I ol ai as a 6 Page. Food shabitss..X osi20. 6 en 252 Seton ce oe ee eee Se ee eee ee 48 Larval... 2.2 e262 22 2 Se te BE 49 AUG 2 cd oe a ek ee ES a 49 Male) 2c. so5:2 5 2c ae SS eae eo 51 Female 0.2.2 sachsen soon ee a ee 52 Males and femalesitesetber 0 toa ee ite ee coe ye 52 Feeding of hibernated weevils on early cotton =. 2222 52 Time hibernated weevils can exist on foliage before formation of SQUATES 2.2252. SoS ONES ae Oe Se ee ee 53 Concentration ef weevils upon most advanced plants................ 54 Are weevils able to locate a food supply at any considerable distance?.-... 56 Danger from allowing seppacte- crow 2202. ones) ee 57 Increase. in. leatiarca al cotton 5.0) oo A eee ee ee ee 58 Effects of feeding upon squares and bolls. .--..----- eS. Bo Seer Sree 59 Destructive power by feeding. 223 ne Ei Ted 20 Sed See eee 61 Susceptibility of various cottons ...--...----.-..-. Be ee) Pe eee 61 Has the weevil any other food plant than cotton?.....-.-.-... SAS Ne vee é4 Fasects. often. mistaken for the. boll- weevil.2. 20a ee ee 66. @ Tscotton-sead mealatiractiver x5 oe ef eee 68 Laboratory observations Sens Se ree aE A Rede 2, ee seals Ving spares 9 68 | Miehd testes. as a ee Ne ee ee ee eee 69 The possibility of baiting weevils. with sweets ..._...-.-2------.--- geet SES 70 Adtractiveness,of various sweeis... ono. a. 32 bode ee os ee 70 Attractiveness of sweets to hibernated weevils in laboratory............- 71 @ Influence of sweetened water upon feeding of weevils on cotton plants... 72 % Field tests for hibernated weevils, using pure molasses.......---..-----. 73 Feioning, deaths... Re 2 oa ee eee 74 Reprodu¢tion +. 228e52 a ee eee ee 74 Method of making field observations upon work of weevils.-..-.----.--- 74 Fertib@etion. 5355 ee ee i eee 7 @ Age of beginning copulatien 2.2524 = ee eee De Sexual attraction and duration of copulation_..—- Sere ee ees 76 @ Duration. of fertility in-iselatediemales: S09 ee ee ee 76 OMINOSITION:. oe a cee = Be a ee SEA ota i Re re ee ee 77 Age of beginning ov ipasifion wheat Sn ee a eee ee Cig Examination. of squares.belore oviposition. a ee ee 77 Selection of uninfested squares for oviposition .--.- aioe 5 eee ng ee 78 Laboratory observations 30 2 ee ee ea 79 ; Field observations. 22-2 33 2 eee 80 Activity of weevils in different Sete Of the: days os ee ees 81 Place.of eos-deposition: 0 es ee ee eee & Position of the weevil while puncturing for hea Rieaieten en es > ‘Rhe-act Gikovipostiien,. 2.5 oe ee ee eee 85 Time required to deposit an egg... .-- ce Eee Oe or a eee eats 85 Rate of oviposition—average, maximum ___._........-..--i-<--6.-- 86 Stimulating effect of abundance of squares upon eg « deposition Ses 87 Relation. of warts teevlposition. — 2) 24 2 a eee 88 Effects of oviposition upon squares—flaring, falling-.-....-.---------- 89 Period.of oviposition. = aa Se ee eee 90 Original habit of depositing eggs mostly in bolls......-...-.-------- 90 Does parthenogenesis occur? 24-42 e= ee eee SS 91 IDSTAO NINE se DOSS FSSC Se SOS REE s Les SESE ee ete ea Percentage of weevils developed from infested squares --....--.--..----- Development of weevils in squares which never fall...............------ Durahioneoet the literowcle: {22s 2s ee kee 5 eaten Pe AS ee ass py cette BRO OCSOr SEMeCTAMOMNS ee alae le oa escew ite se remeicicreieimewinin Cie sesenice = =< Possible annual progeny of one pair of hibernated weevils....-..-------- Thermal influence upon activity and development -.....-.-.----------.. Induence:ot retarded development upon sex 22252 5-2- -S.- cee eee te Laboratory experiment in effect of temperature upon locomotive activity - Gradual development during hibernation in south Texas...-...--.-- oe FCASO TEMS GOT cea seers emcee crs Se eh raels Perdana s Vea LV OVEN cua gES COUN hes eh ese ls pips i ee pc Re ns ae eee aloe Ra yee pen) eae Pel Ao Oy mira cesnvorMijemnAbiOn nak ona cule ees oe eue eee Sihieliterisoucint, ma inibernahion ses sc. cee, koe sac ct eee Durttionsot hibermatvon period: 22.2.4 5.5 —. Ree ens a Seti a ee Apparently favorable conditions for tanemeton east iste. oe (Ss ea Neat Percentage of weevils hibernating successiully.....-......---------- Aires OMeMMerCCMCS TLOMN MAT OCTNAMOMs scene fescue c cc tee See oes ae eS Gradual emergence from hibernation ..............------.-- se eT Distance hibernated weevils will fly to food ..........-.-.-.-.------ Gradual attraction of hibernated weevils to squares............--.+-- General movement of hibernated weevils in field having considerable {SI SION] ei SOU OV Sega oe a a re oo EN en PRAT Apparent dependence of reproduction upon food obtained from squares. Progresso imlestation inviields 2224.22.42. -- Paehieee 2510 Gls ean meer ae Wicevil amir SO Wane precmuenony ja. .2 sen i Js se ee Effect of maximum infestation upon weevil multiplication ......_... Proportion of squares attacked that are not destroyed.............-- WELCOME O MV eeNAlS CO. LOPUCROD, certo neha th ee ten re ae Nome reasons tor the early destruction of stalks .-...--- 1222.22. 2.2: DWSISVSIOANU EC HEY OUR a ENS ry DN to sua Ae aieeeter r N age re ae Ne aunaenoy eae PATA eV eo TCLS ovr phate satan mea ice 2 GLE Nek en Les Bet a Weevilsam seed HOuUsSes IL CINMETIES. .S oS Se ee Se ee Se ee ee aes 161 Legislation. needed’ <= a2 5255 Sas. 3c See ee a ee ee ea eee 163 Bibliography .ca..'s5. view oc Godin nec ctee coo case. a eee eee ee eee 164 IMG eNes omen eo ce oars Poet soot ate ta bas Ro oe Ss Scie ee ee nae 173 Puate I, 108 Jhb LV. \ WAL WIT: WADI OIE STIR BONS. PLATES. ( Page. Fig. 1.—Adult boll weevil, dorsal view ................-.-- Frontispiece Fig. 2.—Adult boll weevil, lateral view..........---.-.-.-- Frontispiece IEA oe yh Orn ma nena et eet a Ee een. Chay. parca) sae cae Frontispiece ince 42 — Tar omoy it ATV Maha Sep ea usted as Frontispiece igo hupasventralvie Wine ss senses. eke yolk tos. Frontispiece Mes e6:—— Adult with wingsispread: ss. s42-..5 +2525. 08.28: Frontispiece Fig. 7.—Collection showing life history and work of boll weevil -.-- 32 Fig. 8.—Partly stripped square showing two eggs and a feeding (CIN SUEY age es ong tee cares Co raps ON Sparta Pe ese re Pe teaeiee sors 32 ‘Fig. 9.—Square with egg deposited outside.............-..-...--- 32 RigsalOe—Squere withotull-orowmelanvar 62. = 22 fo = ee ee 32 Rio tin ups qusupormed wilhimi squares... Sess oss ee oe B2 Fig. 12.—Weevil just transformed to adult in square .-.-.-.....---- 32 roy ls. hwoslarcelanveonmelarcesbolliee esse. see ae eee oe 32 iota 42 Pupalscell tirom™ubolls brokens Opens 22-25 ose ee a2 eee 36 ger e— OIG ENICW: Ol OU Passer er esa ee tape ee se ne 36 PionlG Venta li wae ws OlspUlpaise=* sae aac ew hs Cee ee ee Nes ued 36 Fig. 17.—Four pupal cells from bolls compared with four cotton seeds. 36 Fig. 18.—Weevil just escaping from a square ......-...-.-.-.------ 40 Fig. 19.—Weevil just escaping from boll, normal method_.-.-...-.-. 40 Fig. 20.—Square showing emergence hole of weevil.-.....--.-----. 40 Fig. 21.—Unopened boll showing emergence hole of weevil ..-.---- 40 Eig 22,——@ace used im breeding weevils=: s2222. 22. 5.95-- 2.222 --. 40 hig 23°——\wieevils feeding ontlarge boll: 2 eca. 2225- os -ehee- cee eee 40 Fig. 24.—Leaf fed upon by weevils in confinement. -..-.-.-..--.---- 48 Fig. 25.—Square about to bloom destroyed by weevil -..----..------ 48 Fig. 26.—Weevil full grown in square of usual size..-.....----.---- 48 Fig. 27.—Larva full grown in square; would fall with corolla....---. 48 Fig. 28.—Weevil full grown in square, ovary untouched..-......--- 48 Fig. 29.—Weevil larva destroying two locks of boll ......---.------ 48 Fig. 30.—Weevil preparing puncture for oviposition .....---------- 48 Fig. 31.—Square injured by many feeding punctures. ........------ 48 Fig. 32.—Bloom distorted by many feeding punctures -...-...---..- 48 Fig. 33.—Comparison of flared with normal square ...-..-.--------- 48 Fig. 34.—External signs of weevil injury to large boll ...-..---.---- 60 Fig. 35.—Internal effect of weevil feeding on large boll.....-.-.----- 60 (9) PLATE IX. 10 mies 37.—a, Feeding ‘icles elcsed = woody growth from carpel; b, gelatin formation following weevil injury ........-. Fig. 38.—Boll showing two locks destroyed by two feeding punc- tures OL male weevil .oss- oe a ee Snes Fig. 39.—Device used to test weevil choice of squares __--....-.-.- . Figs. 40 and 41.—Mexiean eotton boll weevil (Anthonomus gr cues) Fig. 42.—Bloodweed. weevil (Livus) -...-.- Sr aSR RMR SOE O DE Oe ds Fig. 43.—An acorn weevil (Balaninus uniformis).......--.--.---- Fig. 44.—Apple curculio (Anthonomus scutellaris).........-..---- Fig. 45.—Pepper weevil (Anthonomus xneotinctus).......-.------- Fig. 46.—Ironweed weevil (Desmoris scapalis) ...........------ — XI. Fig. 47.—Transverse Baris (Baris transversa) ....-.....---------- Hie. 48:-——Cenbranes mentees. 232. eh ee ce ee ee Fig. 49.—Coffee-bean weevil (drecerus fascieulatus): a, oe. 6, cages: CG, pupa <5. 5 ee a ee eee Se Figs. 50 and 51.—Cowpea-pod weevil ( Chalecodermus xneus)-..--.-- XII. Figs. 52 and 53.—Sharpshooter (Homalodisea triquetra) - Re eee Fig. 54.—Cotton stainer (Dysdercus suturellus) ..-.........------ x Fig. 55.—Cotton-stalk borer (Atazia crypta) ....-------------4+-- Fig. 56.—Imbricated snout beetle (Epicerus imbricatus) _......--- Fig. 57.—A snapping beetle ( Monocrepidius vespertinus).....------ XIII. Fig. 58.—Device used to test attraction of molasses for weevils in field Figs. 59 and 60.—Weevils “‘ playing *possum”’ _.............-.-- Fig. 61.—Method of obtaining exact data regarding weevil work in field. 22.52 Vat ee ee ee ee XIV. Fig. 62.—Section of square showing location of egg -.--.---..---- Fig. 63.—Hull stripped from boll showing two-eggs-on inner surface Fig. 64.—Section of boll showing location of egg.......---.--.---- Fig. -65.—Wart formed in healing egg puncture.---..----.-- date XY. Fig. 66.—Two egg punctures in -a-sqiare ...--.-.----.-.---2----- Fig. 67.—Square flared widely from two feeding punctures ------- Fig. 68.—Infested squares fallen to the ground -............-..-- XVI. Fig. 69.—Iniested squares hanging dried upon the plant.-.-...--- XVII. XVIII. Fig. 70.—Refrigerator devised for breeding weevils under low tem- PeTahres 2-2. Soak ob Re ee eee Fig. 71.—Boll showing three larvee in one lock -.-.-.------------ Fig. 72.—Apparatus for testing effect of low temperatures on weevil RELDVIEDY Lasce cee es SS ot Be ee ee Fig. 73.—Comparison of planted with seppa cotton on April 15, 1904 Fig. 74.—Comparison of planted with seppa cotton on May 14, 1904 Fig. 75.—Locality found very favorable for successful hibernation in winter of 1902 to MOS. son an ot ee ee Fig. 76.—Near view of small infested bolls in late fall.......--.-- Fig. 77. ee standing in late fall after they should have been destroyed: ons ea eee Fig. 78.—Destroying stalks, forming windrows preparatory to bUENDING +... ch ae Se eee Page. Ah PuaTE XIX. Figs. 79 and 80.—Small bolls containing weevils when found shipped with seed into uninfested localities .....-.-- Fig. 81.—Comparison of pilosity on stems of American and io ngvlanecOttOMmen setae cee ee RL soe So. Fig. 82.—Gelatin formation in boll following feeding punctures, drtedvandiblackemeds asain iit ee ees XX. Fig. 83.—Gelatin formation in square after drying..-.--..---.- Fig. 84.—Larva of Bracon mellitor attacking larger larva of boll WC Call anmethNeeScUAne Meese ie eye a ala) chee Spey peace Io Fas Fig. 85.— Pediculoides ventricosus breeding upon wasp larvee..--- X XI. Fig. 86.—Cage work in studying effect of poisons in the field --- Fig. 87.—Experimental apparatus for testing effect of hydro- cyanic acidegas| upon weevil stages. - 2222. -.22-222-- Fig. 88.—Experimental apparatus for testing effect of formalde- hyde vapor, upon weevil stages’. 5.2...-22..252 5252 XXII. Fig. 89.—Weevils killed in passing through cotton gin......--- Fig. 90.—Remains of weevils passed through main fan at gin- TNC TAY fern aes esc erat et op cyst Sie elle ia ot iain ete ae XXIil. Fig. 91.—Passing weevils through gin—a, seed, and b, mote col- TGs t. CO NI GD O1 NEC iN O Nam Res rer Moin G8 ieays ed towne 2h. AGS Fig. 92.—Gin opened, showing spaces through which weevils escape the achlomrol the saws: 2424-05505 = ee Fig. 93.—Cotton field in weevil-infested territory producing a In allemperedl Chewy sateen ao eee Smead BO TEXT FIGURES. Map showing increase of weeyil-infested territory between the years SLE OT Sta rat CRRIIG 0) oreo 8 atey cia pn eeetan ies Tare eh kt 4 Ee oe Lelie ie de . Mexican cotton boll weevil; head, showing rostrum and antenne.... . Diagram showing average activity of five female weevils...........-. . Diagram comparing outline of general weevil movement in a field with outline of present weevil-infested area_.2-...-.-:..--..-----2-2--- . Map showing successive weevil movements into Louisiana .........-. eATAasiLeOmNOll weevil C@Enacon melliton) 6-6 ea. a) ae eke eo ee TE MEennyAOl DOllweevllCedrculordestventnicosus)te- ae (5a. 2 secs . A native ant enemy of the boll weevil (Solenopsis geminata) ....-..--- 156 156 JE JEJE USMIG, IBb, The present bulletin is based upon Bulletin No. 45, of this Bureau, entitled ‘‘The Mexican Cotton Boll Weevil,” issued in May, 1904. That publication included the results of investigations of this impor- tant pest which had been carried on for several years. The present bulletin includes additional results that were obtained during the sea- son of 1904. In form the principal changes are in the incorporation of the treatment of some 50 additional topics. Asa matter of fact, however, some of the principal actual additions are incorporated in the tables which occur throughout the pages of the bulletin. Many additional features of the life history of the pest that may throw light upon the question of combating it have been investigated. In some respects very considerable additions to our knowledge of the insect have been made. This is especially the case in all matters relating to dissemination. This topic deals with matters that are naturally diff- cult to determine. The work must be done in the field, and a large territory must be covered. Through the cooperation with the Louisi- ana Crop Pest Commission, which was engaged in an attempt to pre- vent the further advance of the boll weevil into that State, a number of entomologists occupied several months’ time in the extreme eastern and northern regions infested by the pest. It is, of course, only upon the basis of such a complete knowledge of all means by which the weevil reaches new regions that the possibility of checking its advance may be considered. The Mexican cotton boll weevil (Anthonomus gr ee. Boh.) has the unique record of developing in less than twenty years from a most obscure species to undoubtedly one of the most important economic- ally in the world. It was first brought to the attention of the Bureau of Entomology as an enemy of cotton in Texas in 1894. Before it had invaded more than half a dozen counties in the extreme southern portion of Texas several entomologists were sent to the region in con- nection with this work. Enough was soon discovered to indicate the most feasible plans for avoiding damage by the pest. These original plans, based upon investigations of the life history of the insect, with modifications, for the most part due to climatic conditions in regions quite dissimilar to the lower portion of Texas, are still the basis for all that is known in combating the pest. However, at that time it (13) 14 was necessary to pay particular attention to the immediate economic phases of the problem, and a detailed study of the habits of the insect was impossible. In 1902, by the aid of a special appropriation by Congress, it became possible to establish a complete field laboratory in the portion of Texas in which the weevil had been known to exist at that time for about eight years, where a careful investigation could be conducted regarding the points in the life history of the pest that offered even remote chances of suggesting means of avoiding damage. The results of the work at this laboratory that have been of more immediate economic bearing have already been published in farmers’ bulletins of this Department. However, as will be seen from the fol- lowing pages, a very large mass of information concerning all the habits of the boll weevil has been accumulated. Not only on account’ of the great economic importance of the problem and the demand for information from numerous quarters concerning the biology of the pest, but also on account of the fact that the methods followed in this work have been to some extent original, and may be of use in con- nection with the investigation of other insects, it is thought advisable to publish a great number of the observations that have been made. The historical and economic features, to which reference has been mace elsewhere in the publications of the Bureau, are included to bring together in convenient form practically all that is known regard- ing the species. Much information obtained by the earlier investi- gators of the Division of Entomology, Dr. L. O. Howard, Mr. C. L. Marlatt, Mr. C. H. T. Townsend, and Mr. KE. A. Schwarz, has been used. On account of the painstaking character of the work of Mr. Schwarz, and his intimate knowledge of related species, his reports, largely unpublished, have been found especially valuable. Special acknowledgment is due to Mr. Schwarz also for his assistance in the determination of the recognizable insect fragments contained in the bird stomachs collected and examined. Because of his very intimate knowledge of this work he has written the paragraphs under the sub- ject ‘* Birds,” pp. 150 to 153. In presenting this work the authors have taken care to state fully the data furnishing the basis for the various conclusions. Under each | important heading will be found, first, a description of the methods and apparatus employed; second, a full and in many cases tabular statement of observations; third, the obvious conclusions. Care has constantly been exercised to avoid errors likely to result from artificial conditions in the laboratory. A large part of the work of the past two years was in ascertaining how closely laboratory results corre- sponded to the actual conditions in the field. The writers have on many occasions been surprised to discover how close the correspondence is, and consider that the demonstration ona large scale of the possibil- ity of accurately determining the details of the life history and habits > OO ee a ida A Wi i i laa Miia lati, As 15 of an insect by laboratory investigations is by no means the least important of the results of the investigation. In general the laboratory investigations have been under the direc tion of the senior author, Mr. W. D. Hunter, but practically all of the labor of preparing detailed outlines and of executing or supervis- ing the execution of the laboratory work has devolved upon the junior author, Mr. W. E. Hinds, who has been in charge of the boll weevil laboratory. In addition to the assistants, Messrs. A. W. Morrill and G. H. Harris, whose work was incorporated in the original publication (Bulletin 45), the most important observations and experiments of the following field agents have contributed to the publication in its pres- ent form: Messrs. C. M. Walker, W. D. Pierce, W. A. Hooker, W. W. Yothers, A. C. Morgan, J. C. Crawford, and $. Goes. Besides these, Prof. H. A. Morgan, the secretary of the Louisiana Crop Pest Com- mission, has suggested many lines of investigation. Mr. James Hull, of Victoria, Tex., was employed for several months in making a thorough study of cotton-ginning machinery. - Specifically, all of the present bulletin, except the portion preceding the topic ** Life History,” p. 30, and the topics following the subject ‘‘Wutile- Methods Frequently Suggested,” p. 159, with the further exception of the topic upon ‘‘ Birds,” p. 150, has been written by the junior author. The illustrations used are from photographs taken for the work by the junior author, with the exception of the text figures and the illustrations of ‘‘Insects mistaken for the boll weevil,” of which those marked ‘‘ original” are, with one exception, from draw- ings prepared by the Bureau of Entomology. THE MEXICAN COTTON BOLL WEEVIL. GENERAL CONSIDERATIONS. HISTORY. There is very little certainty regarding the history of the Mexicam cotton boll weevil before its presence in Texas came to the attention of the Bureau of Entomology in 1894. The species was described by Boheman in 1843 from specimens received from Vera Cruz, and it was recorded by Suffrian in 1871 as occurring at Cardenas and San Cristobal.,. in Cuba. Written documents in the archives at Monclova, in the State of Coahuila, Mexico, indicate that the cultivation of cotton was prac- tically abandoned in the vicinity of that town about the year 1848, or at least that some insect caused very great fears that it would be nec- essary to abandon the cultivation of cotton. A rather careful inves- tigation of the records makes it by no means clear that the insect was the boll weevil, although there is a rather firmly embedded popular notion in Mexico, as well as in the southern United States, that the damage must have been perpetrated by that species. As far as the accounts indicate, it might have been the bollworm (//eliothis obsoleta) or the cotton caterpillar (Alabama argillacea). From 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, C. V. Riley, then Entomologist of the Department of Agriculture, published in the report of the Commissioner a very brief note to the effect that Antho- nomus grandis had been reared in the Department from dwarfed cot- ton bolls sent by Dr. Edward Palmer from northern Mexico.* This is «4 The following is a copy of the original letter by Doctor Palmer: HAGLE Pass, Trex., September 28, 1880. The ComMMISSIONER OF AGRICULTURE. Str: 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 falls; 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 (17) 16780—No. 51—05—2 18 the first account associating the species with damage to cotton. The material referred to was collected in the State of Coahuila, supposedly not far from the town of Monclova. The exact date at which the insect crossed the Rio Grande into Texas is as uncertain as the means whereby this was accomplished. All that can be found, which is mostly in the form of testimony of planters in the vicinity of Browns- ville, indicates that the pest first made its appearance in that locality about 1892. In 1894 it had 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 Bureau of Entomology as an impor- tant enemy of cotton. Mr. C. H. T. Townsend was immediately sent to the territory affected. His report was published in March, 1895. It dealt with the life history and habits of the insect, which were pre- viously completely unknown, the probable method of its importation, the damage that might result from its work, and closed with recom- mendations for fighting it and preventing its further advance in the cotton-producing regions of Texas. It is much to be regretted that the State of Texas did not adopt at that time the suggestion made by the Bureau of Entomology that a belt be established along the Rio Grande in which the cultivation of cotton should be prohibited, and thus cut off the advance of the insect. The events of the last few years have verified the prediction of the Bureau of Entomology in regard to the advance made and the damage caused by the insect. In 1895 the insect was found oS the entomologists, 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 prin- cipal cotton-producing region of the State caused the Bureau to con- tinue its investigations during practically the whole season. The results of this work were incorporated ina circular by Doctor 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 exten- sion of the territory affected. It should be stated in this connection that the region -from San Antonio to Corpus Christi, and thence to Brownsville, will frequently pass through similar experiences, which will be quite different from anything that may be expected to occur find enclosed insects and many of the injured bolls, some newly punctured, others taken from under the plant. Monclova, Mexico, and the surrounding country a few years ago was famous for its large supply of cotton; at this time none can be grown, owing to the destructive insect, samples of ice are sent. The inhabitants 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. ee ee ee ee ee | 19 in regions where the rainfall is more certain. In 1900, as well as in 1903, in all or part of the region referred to, the numbers of the weevil were reduced by climatic conditions, principally a scanty rainfall, so that they were comparatively unimportant factors. During 1896 the investigations were continued, and the results published in another circular issued in February, 1897. This circular 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, although 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. Townsend was stationed in Mexico, in a region supposed to be the original home of the insect, for several months to discover, if possibJe, any parasites or diseases that might be affecting it, with the object of introducing them to prey upon the pest in Texas. Unfortunately nothing was found that gave any hope of material assistance in the warfare against the weevil. The season of 1898 was very favorable for the insect. Bastrop, Lee, and Burleson counties became invaded, and some isolated colo- nies were found across the Brazos River, in Waller and Brazos coun- ties. Investigations 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. 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 by having agents in the field almost constantly for four years, and all correspondence was referred to the State entomologist; but, unfortunately, the insect continued to spread, and it soon became apparent that other States than Texas were threatened. This caused the work to be- taken up anew by the Bureau of Entomology in 1901, in accordance with a special appropriation by Congress for an investigation independent of that 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 this provision an agent was sent to Texas in March and he remained in that State until December. He carried on cooperative work upon eight of the larger plantations in the weevil region. The result of his observations 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 20 unsatisfactory. The need of a means of testing the recommendations of the Bureau of Entomology upon a large scale, and thereby furnish- ing actual demonstrations to the planters, became apparent. Conse- quently, at the suggestion of the Department of Agriculture, provision for an enlargement of the work was made by Congress. Agreements were entered into with two large planters in typical situations for test- ing the principal features of the cultural system of controlling the pest upon a large scale. - In this way 125 acres at Victoria and 200 acres at Calvert were employed. At the same time the headquarters and laboratory of the special investigation were established at Vic- toria, and such matters as parasites, the possibility of poisoning the pest or of destroying it by the use of machines, as well as investigat- ing many of the features of its biology that were still absolutely unknown, were given careful attention by a specially trained assistant whose services were procured for that purpose. The results of the field work for this year were published in the form of a Farmers’ Bulletin entitled ‘‘ Methods of Controlling the Boll Weevil; Advice Based on the Work of 1902;” but on account of the late date of the establishment of the laboratory (June), and the consequent incom- pleteness of many of the records, it was not thought advisable to publish anything concerning the laboratory investigations. 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 1901. Specimens of parasites were frequently exchanged, and through the courtesy of Prof. A. L. Herrera, chief of the Mexican commission, an agent in charge of the investigation in Texas visited the laboratories at the City of Mexico and Cuernavaca, where a study was made of the methods of propa- gating parasites, especially Pediculoides ventricosus Newp. A large number of specimens of this mite were brought back to Texas, where they were carried through the winter successfully and used in field experiments the following season. The favorable reception by the planters of Texas of the experi- mental field work conducted during this season, with the increased territory invaded by the pest, brought about an enlarged appropria- tion for the work of 1903. By enactment which became effective on the 4th of March, $30,000 was placed at the disposal of the Bureau of Entomology. Itthus became possible toincrease the number and size of our experimental fields as well as to devote more attention to the investigation of matters suggested by previous work in the laboratory. Seven experimental farms, aggregating 558 acres, were accordingly established in as many distinct cotton districts in Texas. Despite generally very unfavorable conditions the results of this experimental 21 work demonstrated many important points. The principal ones are detailed in Farmers’ Bulletin No. 189 of this Department. A general realization of the great damage done by the boll weevil now © led to the appropriation by Congress of $250,000 for use in enabling the Secretary to meet the emergency caused by the ravages of the insect in 1904. It thus became possible to again increase the number of experimental farms and to pay especial attention to a number of impor- tant matters that could not be investigated previously. As was stated in the preface, the present bulletin is one of the results of this work. The economic results of more immediate importance have been pub- lished in farmers’ bulletins and other publications of this Department. Farmers’ Bulletin 209 dealt with the possibility of controlling the boll weevil in cotton seed and at gins. Farmers’ Bulletin 211 dealt with the value of the use of Paris green in an attempt to control the pest, a matter which was of very great importance in infested regions during the season. Circular No. 56 of the Bureau of Entomology dealt with the most important step in controlling the pest, namely, the early fall destruction of the stalks. Including the seven editions of Farmers’ Bulletin No. 189, which incorporated some of the results of the work of the season of 1903, 260,000 copies of these publications were issued. DESTRUCTIVENESS. Various estimates of the loss occasioned to cotton planters by the boll weevil have been made. In the nature of the case such estimates must be made upon data that is difficult to obtain and in the collec- tion of which errors must inevitably occur. There is of course a general tendency to exaggerate agricultural losses, as well as to attrib- ute 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. 10,500,000 bales should be produced. Now, however, in the opinion of most authorities, the weevil has made this possibility very 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 22 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 completely 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. Aithough 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 to continue the industry profitably. A careful examination of the statistics, to which cunize complete ref- erence is made in Farmers’ Bulletin No. 189, has indicated that the pest causes a reduction in production for a few years after its advent of about 50 per cent, but at the same time it is evident that mest planters within a few years are able to adopt the changes in the sys- tem of cultivating this staple that are made necessary by the weevil, so that the damage after a short time woe not compare with that at the beginning. Upon the foregoing basis, during the season of 1903 the weevil cause die cotton planters a . loss of about $15,000,000, and this nee agrees rather well with estimates made in other ways by the more conservative cotton statisticians. A similar esti- mate made in 1902 led to the conclusion that the damage amounte to about $10,000,000. It consequently appears that during the years the pest has been in Texas the aggregate damage would reach at least $50,000,000. Many conditions of climate and plantation practice in the eastern porticn of the cotton belt indicate that the weevil problem will eventually be as serious east of the Mississippi as it now is in Texas. According to the estimates of Mr. Richard H. Edmunds, the editor of Manufacturers’ Record, the norma! cotten crop of the United States represents a value of $500,000,000; the extreme ultimate dam- age that the pest might accomplish over the entire belt would be in the neighborhood of $250,000,000 annually, provided none of the means of avoiding damage that are now coming into common use in Texas were adopted. In spite of the general serious outlook, however, it must be stated that fears of the damage the weevil may do are very often much exigg gerated, especially in newly invaded regions. It is not at ail necessary to wees cotton. The work of the Bureau of Entomology for. oo seasons has demonstrated that a crop can be grown profitably in spite of the boll weevil, and this experience is duplicated by many planters in Texas. During the season of 1904 the usual increase in infested territory occurred. About 15,000 square miles, representing approximately an 23 area devoted to the cultivation of cotton of 900,000 acres, the normal production from which would be in the neighborhood of 350,000 bales, became invaded for the first time. This brings up the total infested arca in the United States at present to about 32 per cent of the total cotton acreage. A very conservative estimate of the damage caused by the pest, based upon the principles mentioned in the foregoing paragraph, is $22,000,000 for the season of 1904, as against about $15,000,000 during the preceding season. Many estimates much larger than this one have been made. Careful examination, however, reveals the fact that many fallacies are connected with such excessive esti- mates. There is a general tendency to overestimate the damage by insect pests, and to attribute all of the damage in any quarter to insect depredations when climatic conditions have been unfavorable. In this connection it is of interest to note the present very large crop (estimated by the Bureau of Statistics of this Department on December 3, 1904, as 12,162,000 bales“), and to. refer to the question that has been raised as to the reasons for this very large production in view of the large territory infested by the pest. The followimg appear to be the principal reasons for the present large production: (1) The insect has not yet reached numbers in all its range sufficient to appreciably reduce the crop. The accompanying map (fig. 1, p. 25) outlines the total area in which any weevils are known to occur. In perhaps 10 per cent of the territory thus considered infested only isolated colonies occur, and the general production has not yet been curtailed. In some of the northern counties of Texas, for instance, the production could not have been reduced by the weevil, although | the statistics show considerable variation between the several years on’ account of changes in acreage and the ravages of other insects, prin-. cipally the bollworm. The following table shows variations in pro- duction in some of the counties of north Texas in which the boll weevil is not yet numerous enough to appreciably reduce the crop. TaB_E I.—Cotton production in certain counties in northern Texas, in equivalents of 500- pound bales. County. 1899. 1900. 1901. 1902. 1903. Average. PRE RPRE Eh OUEL Cf paynirn data iia taal Wal cies s/o3m Sc ciao 15, 064 34, 488 28, 454 16, 981 30, 172 25, 031 Beamer oS oe ee enon eaten ce 16, 826 21, 347 16, 756 17, 829 20, 807 18, 613 BAEC. OU oe iatanta ie banister oman oa sa lore 28,.584 47, 870 39, 911 31, 284 33, 815 35, 402 BREEN Soop pees ah Dates aciots cosa oe 49, 077 70, 963 60, 049 47, 344 62,.979 58, 082 (2 LOLE. oo UMBC OR Gr eo ae ee en Mins aes ee oan 11, 905 18, 751 19, 561 11, 012 20, 810 16, 408 (2) Throughout the portion of Texas where the bulk of the crop is produced—that is, north of about the latitude of Waco—various condi- tions combined to cause an unusually small number of weevils to hibernate successfully during the winter of 1903-4. The principal factor in this situation was the very early date of the first killing frost, @ Census Bul. 19, April 25, 1905, gives crop of 1904 as 13,584,457 bales of 500 pounds. 24 which was about thirty days prior to the average date for the past fifteen years. This early frost destroyed a great number of immature weevils in the squares and bolls which would otherwise have passed through the winter to damage the crop in the spring. (8) An important factor which has contributed to the production of a large crop in the same region has been a lessened degree of damage by the bollworm. It has been estimated by Mr. A. L. Quaintance, of the Bureau of Entomology, that this pest could not have caused more than about half as much damage during 1904 as during the preceding season. During the first of these years it was estimated that the dam- age would aggregate $5,000,000, as against about $2,500,000 damage for the latter year. (4) The high price of cotton pricr to the time of planting the crop of 1904 undoubtedly had the effect of increasing the acreage consid- erably. (5) The growing season was unusually favorable. The average of the conditions of the growing crop in Texas from May to September, inclusive, as published by the Bureau of Statistics, of this Department, was 82 in 1904, as against 72.5 in 1903. The average condition for 1904 was, in fact, much higher than in even the season of the largest crop ever previously produced, namely, 1900, when the average condi- tion reported for the months mentioned was 77.6. (6) The season of 1904 was exceedingly favorable during the time of picking the crop, resulting in an unusually small loss of lint from rains. (7) The large amount of work done by the Department of Agri- culture and commercial bodies which imported many carloads of improved seed, and the more general adoption of approved cultural methods also contributed somewhat to the large crop produced. A general idea of the effect of the ravages of the boll weevil in reduc- ing the crop in Texas may be obtained from the following table: TaBLe I].—Comparison of cotton production and acreage in Texas and Louisiana wn equivalents of 500-pound bales. Texas. Louisiana. Year. : : Acreage. Crop. Acreage. Crop. gO) Ee rae Aa RSS ee eee Rr Rosy PH Sars Sc TO CGO AER GSE 6, 642,309 | 2,609,018 | 1,179,156 700, 352 TOG ke eee ers Bornes VEINS AOR as nen SN Gi a ets SACS 7,041,000 | 38,438,386 | 1,285, 0C0 705, 767 BL OO ee fr ES Na a hee pe eng 7,745,100 | 2,502,166 | 1, 400, 650 840, 476 do 10 Pe Solan eri ae ee SOS OL RE ey a A Rai 8,006,546 |} 2,498,013 | 1,662, 567 882, 073 7G 0 ae eS ee a ae nr Arai ey eL RE RS Bane eet TO ee ae oe 8,129,300 | 2,471,081 | 1,709,200 824, 965 aS OY Mee AE eit Spee a, Seater OE a a MERE AS Re A Gooe 8, 704,000 | 3,080,433 | 1,940, 000 893, 193 It will be seen that while the acreage in Texas and Louisiana has been increasing at about the same proportion the crop in Texas has decreased annually for the past six years (with two exceptions—1900 and the present year), while the crop in Louisiana has increased annu- 25 ally (with one inconsiderable exception—in 1903). That the boll weevil is the cause that has prevented Texas from keeping pace with Louisiana will be admitted by all. The exceptional years, 1900 and 1904, in which the production in Texas did not decrease, were undoubtedly those in which the conditions for the cotton plant were unusually favor- b 4 Bf IGULESPIE| Sf Fic. 1.—Map showing increase of weevil-infested territory between the years 1901 and 1904. (Original). able. Moreover, it is to be noted that in the first of these two years the pest had not reached far into the most productive counties. TERRITORY AFFECTED. At the present time the boll weevil has not been found in the United States outside of Texas and Louisiana. The infested territory in this country is shown on the accompanying map (fig. 1). In con- nection with this figure it should be noted carefully that there is a 26 considerable area within the outside line in which the weevil has not yet reached great numbers. - At frequent intervals during the season of 1904 accounts have appeared regarding the occurrence of the weevil at points far beyond the limits of the infested territory as indicated in fig. 1. It seems likely that at any time the pest may be carried far outside of the present infested territory through the shipment of cotton seed .or certain other cotton products. In view of this fact the Bureau of Entomology has paid especial attention to these reports. Entomolo- gists connected with the Bureau have investigated rumors originating in parts of Louisiana, Arkansas, and Indian Territory, and through cooperation with State and station entomologists the Bureau has also received specific information about reports in Georgia, South Caro- lina, and elsewhere. Fortunately, it has been determined that all these reports have been based upon misidentifications of the numerous species of insects which are apt to be found in cotton fields. In Texas the infested area extends from Brownsville, where the weevil originally entered the State, to Sherman. In Louisiana six of the westernmost parishes are known to be generally infested and three others have a small number of weevils within their boundaries. The cotton acreage involved in this territory amounts to 32 per cent of the cotton acreage in the United States, and produced in 1900 about 37 per cent of the total crop of this country, or over one-fourth of the crop of the world for that year. There are some features of special interest in the situation in Cuba. Although the weevil has long been known to occur in the island, it has attracted very little attention on account of the fact that the cul- tivation of cotton was abandoned for a long time in favor of crops that have been more profitable. Now, however, with the better price of the staple and rather unsatisfactory returns from some other crops, cot- ton is being planted upon a considerable scale. Mr. E. A. Schwarz was sent to the island on two occasions to study the conditions there. Although his report refers especially to the Province of Santa Clara, it is probably true that conditions similar to those he describes obtain everywhere. He found that the entire province is naturally more or less infested by the boll weevil, and that weevils did not spread from cultivated cotton planted with seed obtained in the United States to the wild plants, as at first supposed, but from the latter to the former. The weevils were found to be more numerous on the kidney cotton growing wild than on the loose cotton (seminiella). The latter, when growing alone, was usually found to be free from weevils, but likely — to be infested when growing in the vicinity of kidney cotton. A large number of wild cotton trees growing in the vicinity of dwellings or growing entirely wild are always infested, and here the weevils are more numerous, but never as numerous as on the cultivated Egyptian 27 f cotton. At one locality, where a large number of kidney cotton trees were growing (about 50 plants, some of them probably 20 years old), it was found that at least one out of every twenty squares had been punctured by the first week in March. From Mr. Schwarz’s report it does not seem that there is a very promising outlook for cotton raising in Cuba. The presence of wild perennial cotton, upon which the eal probably exists everywhere, will always be a source of danger. The long moist seasons and mild winters will form more favorable conditions for the pest than will occur anywhere in the United States. During the season of 1904 Mr. Edward Ferrer conducted, an inter- esting experiment in the cultivation of cotton in the Santa Clara Province, Cuba, at the suggestion of the Bureau of Hntomology. The plan of the experiment was to eradicate all of the wild cotton plants growing in the vicinity of the place where a field of cotton was to be planted. By such eradication some time prior to planting it was sup- posed that the weevils would be greatly reduced in numbers. Very recently Mr. Ferrer has reported that the resuits have been exceedingly gratifying. He succeeded in obtaining a very profitable crop of cot- ton by the means suggested at a place where several previous attempts had resulted in failure. DISTRIBUTION OF THE BOLL WEEVIL. The following list of localities represents the range in distribution of this insect so far as it is positively known at the present time: United States.—Louisiana: six western parishes of Louisiana wholly or partially infested; Texas: all of the principal cotton-growing coun- ties in the southern, central, and eastern portions of the State, a few border counties along the Red River in the northeastern part of the State not yet infested. (See fig. 1, p. 25.) Mexico.—Tamaulipas: Matamoras, Jiminez; Vera Cruz: Vera Cruz,' San Andres Tuxtla; San Luis Potosi: San Bartolo; Coahuila: San Isi- dro, Allende, Monclova; Michoacan: Zamora; Morelos: Cuernavaca. Cuba. Oe Ean Pinar del Rio: San Cristobal, Rangel; Santa Clara: Cayamas; ietaneae Kastern portion, Condens Guatemala.—Alta Vera Paz (Cook); Peten: Spr José (Champion). It has been impossible to verify the rumors which state that the boll weevil has been found in Brazil and also in some localities in | Africa where cotton is grown. It is said that the injury in these ' localities is identical with that of the boll weevil in the United States. In the Philippines there has been found a species of weevil which is distinct from the Mexican cotton boll weevil, but attacks the cotton in a very similar manner. @Recently Dr. A. L. Herrera has sent specimens collected at Mazatlan in the State of Sinaloa by M. T. Madrigal. 23 PROSPECTS. The investigations of the life history of the weevil that are referred to in detail in the following pages have indicated that the most impor- tant elements in limiting the spread of an insect—namely, winter tem- peratures and parasites—in this case offer no assurance that the pest will soon be checked. For the past ten years, except where local unfavorable conditions have interfered, it has advanced annually a distance of about 50 miles. The insect is undoubtedly changing its habits and adapting itself to climatic conditions in new regions that it is invading. It is undoubtedly true that it has acquired an ability to withstand more severe frosts than occurred in the vicinity of San Antonio in 1895. Except in a few particular regions, however, it does not seem that the continued spread will be as rapid as it has been. The country between Gonzales County and the Red River is practically a continuous cotton field, and the prevailing winds have undoubtedly -favored the northward spread of the insect. Similar conditions will now favor a rapid extension into the Red River Valley in Louisiana, and likewise there seems no doubt that the spread will be rapid in the Yazoo Valley in Mississippi; but in most other situations throughout the belt the cotton fields are smaller and more isolated than is the case in Texas; consequently it is to be supposed that the spread of the pest will be retarded somewhat. Basing estimates on a careful study of the distance the boll weevil has traveled each year, as well as upon some attention that has been paid to the means whereby it reaches new territory, referred to more in detail hereafter (p. 123), it seems safe to predict that in from fifteen to eighteen years the pest will be found throughout the cotton belt. During the time it has been in Texas there has been no tendency toward dying out, and in south Texas the pest is practically as trou- blesome, except in so far as it is affected by changes in managing the crop, as it was in 1895. In Mexico, where it has existed for a much longer period, it is apparently as plentiful as ever. Careful attention that has been paid to the study of parasites and diseases, as well as temperatures unfavorable to the insect, has failed to reveal any pros- pect that it will ever be much less troublesome than now. There will, nevertheless, be seasons from time to time in which the damage will be much less than normal. Climatic conditions will undoubtedly cause temporary diminution of the numbers of the pest in certain localities. In Texas these conditions have given rise almost every year to the supposition on the part of the planters that the insects have died out. This was especially the case in the region between San Antonio and Beeville in 1900, and in the vicinity of Corpus | Christi in 1903. Both these years followed a series of seasons in which there was much less than the normal rainfall; consequently not 29 only had a great many of the weevils been killed, but the numbers had been diminished by reason of the very limited extent to which it was possible to raise cotton. Both 1900 and 1903, however, were exceedingly favorable for cotton. Early planting was possible, and there was an abundance of rain throughout the season. The crop was so far advanced by the time the weevils became numerous that a very fair yield was made, although in neither of the cases was any top crop whatever produced. Whenever a series of years of scanty rainfall is followed by one of normal precipitation the weevil will temporarily be comparatively unimportant. The most disastrous seasons will be those in which the rainfall is excessive and planting unavoidably thrown late. One of the most interesting features of the situation which devel- oped during the season of 1904, which will be dealt with more fully in the succeeding pages, was the fact that the infested region extended eastward much more rapidly than northward. Careful examination of the portions of Indian Territory and Arkansas which the weevil is apt ~ to reach first has failed to reveal any infestation; in fact, on the north the limitation of the infested territory remains practically the same as at the end of the season of 1903. ‘This applies, however, only to the total infested area in which even isolated colonies have been found _to exist. There has been, nevertheless, a gradual northward advance of the region of gross infestation. Its advance has extended from the latitude of the northern portion of Ellis County to about the latitude of the southern portion of Collin County. This situation raises the question of whether the pest has not reached a northern limit beyond which its spread would be prevented or at least checked by climatic conditions. It has been found that there is at least one full generation less during the season at Terrell, Tex., than at | Victoria, Tex., 275 miles farther south. This naturally means a greatly lessened degree of damage. The time when the maximum number of weevils per acre is produced is made considerably later with a consequent manifest advantage to the crop. The | lessened number of generations is due to three principal factors. (1) Later emergence from hibernating quarters; (2) greater time required for the development of the several stages; and (8) the earlier date of the first killing frost. It was pointed out in a previous bulletin (i. e., No. 45) that the considerations just men- _tioned would probably cause the weevil problem to be much less serious in extreme northern Texas and similar localities than has been the case in regions that have hitherto been infested. Never- _ theless, it is to be expected that there will be some adaptation on the part of the weevil to the climatic conditions in newly-invaded regions, and this element introduces considerable risk in any prediction regard- Ing future damage. From the present outlook, however, it may be on 30 stated that, in all probability, the greatest damage by the pest will always be in the régions south of the latitude of Dallas, Tex. A careful consideration of the matter, based upon what is icnitboras regard- ing the life history and habits of ae boll weevil, leads to the supposi- tion that in the alluvial lands of the southern part of the belt, into which the pest 1s now encroaching, the damage will be greater than in any areas which have suffered up to the present time. In Texas, as — is well known, a reasonably effective method of mitigating the damage of the pest has been developed, known as the cultural system. It is to be feared that there will be many obstacles in the-way of the adap- tation of this system to other regions. Of course, the planters in other States will have-the advantage of learning from the experience of planters In Texas; nevertheless, there will undoubtedly be many difficulties. The greater rainfall from the Sabine River eastward will contribute to the very rapid multiplication of the weevils. In Louisiana the rainfall during the growing months of May, June, July, and August has been 4.47 inches each. In Texas, for the same months, = average monthly precipitation has been only 3.26 inches. « In this connection it becomes of some interest to speculate as to the possibility that. the weevil may eventually be carried outside of the United States and gain a foothold in other cotton-producing countries. The fact that the insect is rather rapidly adapting itself to conditions in the United States that are quite diverse from those of its native home leads to the supposition that it would experience but little difficulty in adapting itself.to climatic conditions wherever cotton may be grown. This probability of the BS a = the weevil outside of the United States is increased by the fact that cotton seed for planting purposes is frequently shipped from the United States to various parts of the globe, and that within the last few years various conditions have caused especial interest to be displayed in this matter. There is noth- ing whatever to prevent weevils that may happen to be sacked with cotton seed from being carried long distances on shipboard. In the semidormant condition in which they hibernate, they have often been known to go longer without food than is ordinarily required for a freight shipment from Galveston to Cape Town. Although there are no truly cosmopolitan cotton insects, it seems likely that the boll wee- vil may eventually be more widely distributed than any other. LIFE HISTORY. SUMMARY. The egg is deposited by the female weevil in a cavity formed by eat ing into a square or boll. The egg hatches in a few days and the footless grub begins to feed, making a larger place for itself as it grows. During the course of its growth the larva sheds its skin at — ee d1 os least three times, the third molt being at the formation of the pupa, which after a few days sheds its skin, whereupon the transformation becomes compieted. These inane stages require on the average between two and three weeks. A further period of feeding equal to about one-third of the preceding developmental period is required to perfect sexual maturity so that reproduction may begin. Variation in size depends directly upon abundance and condition of the food supply. Weevils of average size are about 8 mm. in length, one-third as broad as long, and weigh about one-fourth of a grain. Color varies as widely as does size. It is usually of a gray or yellow- brown, and is most markedly yellow in the largest weevils. Sexes are produced in practically equal numbers, the males predominating slightly. No other food has been found which will attract weevils from squares and no plant. but cotton upon which they can sustain themselves for any considerable length of time. (See Pl. L, fig. 7.) THE EGG. The egg of the boll weevil is an unfamiliar object-eyen to many who are thoroughly familiar with the succeeding stages of the insect. If laid upon the exterior of either square or boll it would be fairly con- spicuous on account of its pearly white color. Measurentents show that it is, on the average, about 0.8 mm. long by 0.5 mm. wide. Its form is regularly elliptical (Pl. I, fig. 3), but both form and size vary *somewhat. Some eges are considerably longer and more slender than the average, while others are ovoid in shape. The shape may be ‘influenced by varying conditions of pressure in deposition and the shape of the cavity in which it is placed. The soft and delicate mem- brane forming the outer covering of the egg shows no noticeable markings, but is quite tough and allows a considerable change in form. Were the eggs deposited externally they would doubtless prove attractive to some egy parasite as well as to many predatory insect enemies. Furthermore, the density of the membranes would be insufficient to protect the egg from rapid drying or the effects of sudden changes in temperature. All these dangers the female weevil avoids by placing the eggs deeply within the tissue of the squares or bolls upon which she feeds. Asa rule, the cavities which receive eggs are especially prepared therefor and not primarily for obtaining food. Buried among the immature anthers of a square or on the inner side of one carpel of a boll, as they usually are, weevil eggs become very inconspicuous objects (Pl. III, fig. 8) and are found only after careful search. | EMBRYONIC DEVELOPMENT. Owing to the transparency of the egg membranes, something of the | development of the embryo can be seen through them. Special study is now being made of the embryology of the weevil. ‘The fully devel- o2 oped embryo completely fills the interior of the egg, its large head being in one end and its body curved ventrally upon itself till nearly double. Considerable motion is manifested if the egg be touched at this period. DURATION OF EGG STAGE. Concealed as the eggs are beneath several layers of vegetable tissue, it is impossible to examine them to ascertain the exact length of the egg stage without in some degree interfering with the naturalness of the accompanying conditions. The beginning of the stage was easily obtained by confining female weevils with uninfested squares. Care- ful dissections were then made of the squares at a little later than what was found to be the average embryonic period at that season. In this way it is believed the range of error was reduced to a fraction of a day in most cases, and a large number of observations were made to still further reduce the error. As shown by Table III, 631 observations have been recorded upon this point, the majority of the observations being made in the fall of 1902. Considering the temperatures prevailing at the four periods studied, it appears that the range in development during the average season at Victoria, Tex., has been included, and it seems probable that from these temperatures as a basis the length of the egg stage ean be approximately determined for any season and for any locality within the present area of infestation. Tasrie I1].—Duration of egg stage at certain periods. Mean | Average Average Number | temper- effective} duration Period of examination. or obser ature for temper- of ege *} period. ature. ature. @ stage. 1902. OR. ES oh pws September4 to: October 3-52.02 ok aoe < Se eee eee eee 385 81.0 38.0 | 2.5 to 3.0 October 7stosNoyem ber! 3: Ses as Seca eee ere 107 73.0 | 30.0 | 4.0 to 4.5 November? /to.D ecember this se— see e es eee eee eee 36 62.0 | 19.0 11.0 H 1903. | WEA VO? (GOs LLG 0 sectarian 25 12.5 | 82.5 | 3.5 to 4.0 1904, | EXP ELiMN SMS CC DORMS ase oe aes ha eS ee eee 78 70.0 27.0 ok PO tails. Seve netsis cis ence see Soe eae eee eee eee 631 | aise sede teks 63.6 to 4.2 aIn considering theinfluence of temperature upon the weevils it has been found that with the weevil, as has been found to be the case with many animals, 48° F. isabout the lowest temperature at which activity isshown. Temperatures below that point would, therefore, have no influence upon activity, while all above that point would. For this reason, it is better to speak of the ‘‘effective temper- ature,’’ meaning by that the number of degrees above 48° F. Experiments made upon the influence of temperature upon the activity of weevils indicate that this isan approximately correct figure for this insect. b Weighted average. The extreme range observed in Table III in the duration of this_ stage is from 2 to 15 days, while the average period for the whole number of observations is but 3.6 days. It is possible that the embryo can undergo an even greater retardation without losing its vitality. PLATE II. Bul. 51, Bureau of Entomology, U. S./Dept. of Agriculture, eS 5 at | / Rerfect : Vpuares 2a rod ce : i fed ar oY i Salty i cathee Sessoms Weerils | GATE ppetudes ram Ant on0mn Le grandis Boh. Lxrhihition of its Live Hislary and Work Freparéed £y WE#i é by Lhinds, Ficlo rid, (exas. July BMarx [Fo2. JSutts . pexare tran’ Range. Ad« ae ACT eo dy Pe Range. Werk larva Trtepdor TEL ot ys, Bulonasd (7778 of Weer (ls on ata : - Fig. 7, Collection showing life history and work of boll weeyil—reduced to one-half natural diameter (original). us nA ee vf ‘yy Bul. 51, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE III. DEVELOPMENTAL STAGES IN SQUARES AND BOLLS. Fig. 8, Square showing location of two eggs and the cavity formed by a feeding puncture, natural size; fig. 9, square showing puncture formed for oviposition with egg deposited outside; figs. 10, 11, 12, series of views showing transformation from larva to adult which takes place in the square on the ground; fig. 13, boll nearly full grown containing two large larvee—figs. 9 to 13 reduced to two-thirds natural diameter (original). bs ef ate ee _ 0 33 Among 84 eggs kept for from 9 to 15 days at a temperature of from 49 to 45° F. none hatched when later removed to a higher temperature. It may be noted here that drying of the square will also retard embryonic development, but this condition does not occur in the field. TaBLE 1V.—Range in duration of egg stage. Number Duration of)| Number |Duration of of eggs. egg stage. of eggs. egg stage. Days. Days. 2 2 4 5 to 6 132 2to3 3 8to 9 192 3 5 10 to 11 2to4 15 10 to 12 42 3 to 4 4 10 to 13 96 { 4 3 13 to 14 38tod |} 2 13 to 15 40 4to5 9) mS \ 4 to 6 The duration of the egg stage in bolls does not appear to differ greatly from that in squares. HATCHING. While still within the ege the larva can be seen to work its mandi- bles vigorously, and although a larva has never been seen in the act of making the rupture which allows it to escape from the egg, it is believed that the rupture is first started by the mandibles. The larvee do not seem to eat the membranes from which they have escaped, but owing to the extreme delicacy of the skin it is almost impossible: to find any trace of it after the larva has left it and begun feeding on the square, the membranes having been found in only a few cases. HATCHING OF EGGS LAID OUTSIDE.” It occasionally happens that a female is unable to force an egg into the puncture prepared to receive it and the egg is left on the out- side of the square or boll (PI. IL, fig. 9). Eggs so placed usually shrivel and dry up within a short time. To test the possibility of a. larva making its way into a square from the outside, a number were protected from drying. Of the 19 eggs tested, 6 hatched in from 2 to: 3 days. In no case, however, was the young larva able to make its way into the square and it soon perished. ‘The hatching of eggs laid outside is of no importance, since the larve must perish without doing any damage. tATING OF EGGS DEPOSITED OUTSIDE. The number of eggs left outside increases as the female becomes weakened, and is especially noticeable shortly before her death. Re- peated observations have shown that unfertilized females normally 16780—No. 51—05——3 34 deposit their eges on the outside, and only occasionally is an infertile egg deposited normally, though the attempt is regularly made to do so. The number of such eggs which may be found is greatly dimin- ished by the following peculiar habit, which was observed many times. Occasionally it appeared that the puncture which the female had made for the reception of an ege was too narrow to receive it, and after a prolonged attempt to force it down, the female would withdraw her ovipositor, Jeaving the egg at the surface. She would then turn immediately and devour the egg. After that, seeming conscious of her failure and aware of the cause of it, she would proceed to find and enlarge somewhat the cavity previously made. When this was com- pleted she would attempt to place another egg therein. The second attempt was usually successful, but in one or two cases a female was seen to fail several times, and in more than -half of these cases she ate the eggs, as has been described. PERCENTAGE OF EGGS THAT HATCH. Definite records were not kept upon this point, but in the many hundreds of eggs followed during these observations very few failed to hatch, though some were much slower in embryonic development than were others laid at the same time and by the same female. It is the writer’s general impression that less than 1 per cent of the eggs | are infertile or fail to hatch. THE LARVA. DESCRIPTION. The young larva, upon hatching from the egg, is a delicate, white, legless grub of about 1 mm. (5 inch) in length. Except for the brown head and dark brown mandibles, the young larva 1s at first as inconspicuous as the egg from which it came. As it feeds and grows — it continues to enlarge a place for itself in the square or boll until | the food supply has become exhausted or the vegetable tissues are so ehanged as to be unsuitable for food. By this time, as a rule, the interior of the square has been almost entirely consumed and the larval | castings are spread thickly over the walls of the cavity (PI. LU, fig. 10). This layer becomes firmly compacted by the frequent turning of the | larva as it nears the end of this stage. -In the cell thus formed occur the marked changes from the legless grub to the fully formed and | perfect beetle (Pl. I, figs. 4, 5, and 6). Throughout this stage the body of the larva preserves a ventrally- | curved, crescentic form (PI. I, fig. 4). The color is white, modified somewhat by the dark color of the body contents, which show through the thinner, almost transparent, portions of the body wall. The dor- sum is strongly wrinkled or corrugated, while the venter is quite oD smooth. The ridges on the dorsum appear to be formed largely of fat tissue. After becoming full-grown the larva ceases to feed, the alimentary canal becomes emptied, and both the color and form of the Jarva are slightly changed. The dark color disappears from the inte- rior and is replaced by a creamy tint from the transforming tissues within. The ventral area becomes flattened, and the general curve of the body is less marked. Swellings may be seen on the sides of the thoracic region, and when these are very noticeable, pupation will soon take place. GROWTH. It is impossible to follow the growth of an individual larva without interfering so greatly with its normal conditions of life as to make the observations unreliable. It seemed more accurate to measure larvee of approximately known ages. In these measurements the natural curve of the body was not interfered with, but the measurement taken across the tips of the body as curved. Ja this way it was found that in squares during the hot weather the length of the body increases quite regu- larly by about 1 mm. a day. Asit becomes cooler the daily growth is less. In bolls which grow to maturity the rate of growth is less and the length of the growing period is much greater. Full-grown larvee vary in length from 5 to 10 mm. across the tips of the curve. Larvee of normal size in squares average from 6 to 7mm. The largest larvee are developed in bolls which grow’to maturity (Pl. III, fig. 18). MOLTS. To accommodate the rapid growth of the larva two or three molts, occur. The period of change from one instar or stage to the next is so short that the chances of opening a square at just the righftime to observe the process are very small indeed. However, it has been ascer- tained beyond question that two molts occur before the larva reaches half its growth. The first occurs at about the second day and the second at about the fourth day. Whether a third molt occurs before pupation.can not be positively stated; but having occasionally found larvee which had certainly just molted, but which were much larger than the usual size at the second molt, the writer is led to sus- pect that three larval molts may sometimes, though possibly they do not always, occur. In bolls where the length of the larval stage is often three or four times us great as that usually passed in squares it seems almost certain that more than two larval molts occur regularly. Counting only the first two molts which have been often found, a third _ occurs at the time the larva pupates. PROCESS OF MOLTING. So little is known in regard to the molting of Curculionide that the process as observed is here recorded. In the cases observed, starting 36 at the neck, the skin split along the back, and was then pushed down- ward and backward along the venter of the larva. The cast head shield remained attached to the rest of the skin. Immediately after casting the skin the head, as well as the rest of the body of the larva, was of a pearly-white color. The tips of the mandibles first became brown, and within a short time a yellowish brown color marked the entire integument of the head. DURATION OF LARVAL STAGE. Most of the observations upon the larval stage were made between September 1 and December 15, 1902. The temperature prevailing during the first half of September was as high as is ordinarily experi- enced at Victoria during midsummer, and therefore the extremes of the average season may be considered as having been covered. The time of egg deposition was easily determined by exposing unin- fested squares in breeding cages containing active females. The time of hatching of the larva could only be found by opening the square, and it was so ascertained. ‘The newly hatched larva was then placed in a small cavity made by lifting the covering on the side of a freshly picked square and removing one or twoof the immature anthers. The coverings were then replaced as carefully as possible. Another dis- turbance was necessary to determine exactly the date of pupation. Observations made in this way were checked by others using larve which were allowed to go from egg deposition to pupation under nat- ural conditions and without disturbance until the end of the larval stage was approximately reached. Since the sum of the times found for the various stages agrees approximately with the known duration of the immature period in cases where no disturbance of normal con- ditions occurred, we may conclude that the periods found for the larval stage were approximately correct. Altogether 266 observations were recorded upon the duration of this stage. The majority of the observations may be included in three groups, and when thus grouped they may be best considered in rela- tion to the effective temperature. Table V presents a brief summary of these groups: TABLE V.—General results as to duration of larval stage in squares. Mean | Average average | effective | tempera- tempera- | | Number Average Period of examination. of obser- | range of | ture. | ture. | vations. | stage. 1902. Ue ORE | Days. September: Gio OCtOberOsss eerste ee eee eee eee 18.7 | 35. 7 195 6 to 9 September267to, Octo berries ses. = eee oeine eee eee eee 73.6 | 30.6 15 7 to 12 NOVeEMber 11 toeDecembersl2esse ae asso eee eee 62.5 | 19.5 Us 20 to 20 1904. | Ieée-box experiments sac 5 a seee Sz ect asice Semcicems ce seeine aoe 69.0 11 to 14 to (or) (an) ® Bul. 51, Bureau of Entomology, U. S. Dept. of Agriculture. Fig. 14, Pupal cell broken open, exposing pupa within, enlarged to three diameters; figs. 15, 16, side and ventral views of pupa, enlarged to four diameters (original). ig. 17, Four pupal cells from bolls (on left) compared with four cotton seeds (on right )— natural size (original). 37 During the heat of summer the larval stage requires approximately one week. This time appears to hold so long as the mean average temperature remains above 75° F. As the temperature falls below that point there is a gradual increase in the duration of this stage. The average total effective temperature required during hot weather by the larval stage is not far from 280° F. As development becomes retarded by colder weather the average total effective temperature required to complete it is much greater. These facts may be expressed in general by stating that during the hottest summer weather the duration cf this stage is somewhat less than one week. Development becomes slower as the temperature falls, but does not cease altogether so long as cotton can live. Even moderate frosts do not destroy larve in the squares and bolls, and these may finish development during warmer weather after the frost has taken place. Hard frosts appear to kill both larve and pupe in squares and bolls. The duration of the larval stage in bolls is as a rule much greater. If the boll falls when small the increase is slight, but if an infested boll grows on to maturity the larval stage more than any other. is much extended. Special observations upon the larval stage in bolls have not been made, but reckoning from the known duration of the whole developmental period in maturing bolls we may conclude that the larval stage may frequently extend over six or seven weeks. PUPAL CELLS IN BOLLS. As the boll approaches maturity, the full-grown larva ceases to feed upon the drying and hardening tissues of seed and fiber. Its excre- ment, more or less mixed with lint, becomes firmly compacted, and in the drying which occurs the mass forms a cell of considerable firm- ness, within which pupation and the subsequent transformation to the adult take place (PI. LV, fig. 14). These pupal cells frequently include a portion of the hull of a seed, but the writer has never found a large larva or a pupa entirely inclosed within a single cotton seed. The cells described are shorter and thicker than seeds, but in general appearance there is considerable resemblance between them (PI. LV, fic. 17). Doubtless these cells have misled some into the statement that they have found weevils in cotton seeds. PUPATION. The formation of the adult appendages has gone a good way before the last larval skin is cast. The wing pads appear to be nearly half their ultimate size. The formation of the legs is also distinctly marked, and the old head shield appears to be pushed down upon the ventral side of the thorax by the gradual elongation of the developing proboscis. Finally the tension becomes so great that the tightly © 38 stretched skin is ruptured over the vertex of the head, and it is then gradually cast off, revealing the delicate white pupa. The cast skin frequently remains for some time attached to the tip of the abdomen. THE PUPA. When this stage is first entered the insect is a very delicate object both in appearance and in reality. Its color is either pearly or cream white. The sheaths for the adult appendages are fully formed at the beginning of the stage and no subsequent changes are apparent except in color (PI. LV, figs. 15 and 16). The eyes first become black, then the proboscis, elytra, and femora become brownish and darker than the other parts. The final molt requires about thirty minutes. The skin splits open over the front of the head and slips down along the proboscis and back over the prothorax. ‘The skin clings to the antenne and the tip of the proboscis till after the dorsum has been uncovered and the legs kicked free. Then by violently pulling upon the skin with the fore legs first the tip of the snout and then the antenne are freed, and finally the shrunken and crumpled old skin is kicked off the tip of the abdomen by the hind legs. | DURATION OF PUPAL STAGE, The duration of this stage is more easily determined than that of any other. It seemed to make little difference in the time whether the pupee were allowed to remain in the squares or were removed there- from. Considerable variation in the duration of this stage exists among individuals of the same generation and even between offspring of the same female and from eggs laid on the same day. The period) of investigation ranged from July to December, so that ie extremes of, the season are pefuded: Altogether 530 ATS tions were made upon this point. Nearly all of these are included in Table VI, which shows a summary of the results. TasLte VI.—Tabular arrangement of observations upon the duration of pupal stage in =a squares. | Ra nge in | Av erage | Total ef- Number | Average | PR Period of examination. of obser- | duration duration | hee e _tective . vations. |. Of PUupal: | or stage. | empera-| tempera- | stage. | ture. ture. 1902 TU YOWOws es arse erick Gea eee eee ee ene | 161 QtOeo 35 39. 65 138.8 Sepremibers(a. £0: Octaber 3s iae sa ee | 81 3to 7 aed 36. 05 187.5 Septenmvers24 sto; October 25a sae oe eee 167 4to 8 6.0 4 ipa 186.1 INO Wember2sto lS se 2225 cn. ee Se ee a en eae 2 | 5 to 6 5.6 26.2 146.7 Wecemibere2lor20 ees nae ere eee ee eee eee 4 | 10 to 16 14.5 | 18.55 269.0 1904. 1ip.g (Sp maanCesaHap IEIKXe| OO): eae can ueoseco aoa ocoas ease Silo arene 7.5. | 26.0 195.0 EO ERT fe 2 eee ee Pe ot nee Se 530 Fto 16 |o2 sae | aS Rae ere 39 It should be noted in connection with Table VI that the observations in November, 1902, were made during a period of rather warm weather and that the temperature records for that time are incomplete. It is likely that the average effective temperature given for that period might be different were the records complete. The average duration of this period during hot weather is from three to four days, and as the cool fall weather approaches the period increases to a maximum of about fifteen days. A comparison of Tables III, IV, and V shows that the decrease in temperature affects each stage in very nearly the same proportion. In each case the maximum recorded duration of any stage is about four times its minimum, and the great retardation in each case occurs somewhere between 60° and 70° I’. of mean average temperature, or 17° to 27° F. of effective temperature. Even greater retardation occurs during the winter season without killing the weevil after the larva has become half grown. we The duration of the pupal stage in large bolls has not been deter- mined. It appears to be longer than in squares, but it certainly can not occupy the same proportional part of the entire developmental period that it does in squares. THE ADULT. BEFORE EMERGENCH. Immediately after its transformation from the pupa the adult 1s very hight in color and comparatively soft and helpless. The proboscis is darkest in color, being of a yellowish brown; the pronotum, tibie, and tips of the elytra come next in depth of coloring. The elytra are pale yellowish, as are also the femora. The mouth parts, claws, and the teeth upon the inner side of the fore femora are nearly black. The body is soft, and the young adult is unable to travel (PI. III, fig. 12), consequently this period is passed where pupation occurs. Usually two or more days are required to attain the normal coloring and the necessary degree of hardness to enable the adult to make its escape from the square or cell. EMERGENCE. The normal method of escape from squares and small bolls is by cutting with its mandibles a hole just the size of the weevil’s body (Pl. V, fig. 20). In large bolls the escape of the weevil is greatly facilitated by the natural opening of the boll (Pl. V, fig. 19). Often the pupal cell is broken open by the spreading of the carpels, and when this is the case the pupa, if it has not already transformed, becomes exposed to the attack of enemies or, what is probably a more Serious menace, the danger of drying so as to seriously interfere with 40 a successful transformation. If the cell remains unbroken the weevil always escapes by the path of least resistance, cutting its way through as in the case of a square (PI. Me hie 21); The material removed does not appear to be eaten, but is ane cast aside and left within the cell as a mass of fine débris. CHANGES AFTER EMERGENCE. At the time of emergence the weevils are comparatively soft, and they do not attain their final degree of hardness for some time after they have begun to feed. If they never feed they never harden. The color of the chitin is of an orange tinge at the time the weevils leave the squares or bolls, but after exposure for some time it turns to a dark chocolate brown. The development of the hair-like scales is probably entirely checked by the drying of the chitin, but the darkening of the ground color makes the scales more apparent, and thus gives the impression of further development after emergence has taken place. DESCRIPTION OF ADULT.@ The poner outlines of the body of the weevil are shown in Plate I, figures 1, 2, and 6. The color varies from a reddish-brown, in weevils which have just become adult and left the squares, to a dark gray-brown, in weevils which have been exposed to the air for some time. Weevils which have developed in bolls are usually more yel- «The following technical description of this species is taken from the Revision of Genera and Species of Anthonomini Inhabiting North America, by Dietz, in Trans- actions of American Entomological Society, Vol. X VIII, p. 205. Anthonomus grandis Boh.—Stout, subovate, rufo-piceous and clothed with coarse, pale-yellowish pubescence. Beak long, slender, shining, and sparsely pubescent at the base; striate from base to the middle, striz rather coarsely punctured; apical hali finely and remotely punctured. Antenne slender, second joint of funicle longer than the third; joints 3-7 equal in length, but becoming gradually wider. Head conical, pubescent, coarsely but remotely punctured, front foveate. Eyes moder- ately convex, posterior margin not free. Prothorax one-half wider than long; base feebly bisinuate, posterior angles rectangular; sides almost straight from base to mid- dle, strongly rounded in front; apex constricted and transversely impressed behind the anterior margin; surface moderately conyex, densely and subcontluently pune- tured; punctures irregular in size, coarser about the sides; pubescence more dense along the median line and on the sides. Elytra oblong, scarcely wider at the base than the prothorax; sides subparallel for two-thirds their length, thence gradually narrowed to and separately rounded at the apex, leaving the pygidium moderately exposed; strie deep, punctures large and approximate; interstices convex, rugulose, pubeseence somewhat condensed in spots. Legs rather stout, femora clavate, ante- rior strongly bidentate, inner tooth long and strong, outer one acutely triangular and connected with the former at the base; middle and posterior thighs unidentate. Tibizee moderately stout, anterior bisinuate internally, posterior straight; tarsi moder- ate, claws broad, blackish, and rather widely separate; tooth almost as long as claw. Long. 5-5.5 mm.; 0.20-0.22 inch. Bul. 51, Bureau of Entomology, U. S. Dept. of Agriculture. (Ng Meevil ener g z NG. WEEVILS ESCAPING FROM SQUARE AND BOLL. Fig. 18, Weevil in act of emerging from square; fig. 19, weevil in act of emerging from boll, tagged record attached; fig. 20, square showing emergence hole of weevil; fig. 21, unopened boll showing emergence hole of weevil; fig. 22, convenient cage used in breeding weevils in the laboratory; fig. 23, weevils feeding extensively on medium-sized boll—all except fig. 22 reduced to two-thirds natural diameter; fig. 22 reduced to one-third diameter (original). a AEN tae ae ey Nt al SAY / ih Hs eet VR ir ath : vee 7 : See : h D y . ‘ phase S . £ Pee q me iy) P L x Nay ; ; ; ; ‘ J ~~ My as ‘ ‘ ‘ 4 Wt ‘ ‘ balk) : . Dy ell r : i 7 . Fs : 5 i - f 4 : 4 = * > i y ‘ ; } : ‘ , . : ® A ‘ , Ci i u : ) ‘ 1 1 . i . ' . , 1 ate eed, rn , ‘ 4 z \e ' . j n t A ‘ te y a 5 i , x v2 + ! ¢ ‘ - . 4 r , ' ? « ey ) " i ‘ ys ‘ : 1 ‘ e+e # 1 J ue t j otha: ‘ : : " ; 1 1 - : ’ e , ” 4 ' Ul + - , ‘ : ; a Neate ‘ y , 4 ' A : ' " - 4 fi ? 1 . ‘ 4 ‘) } ' “ j “1 4 . \ i 7 r ‘ i - + . { ps y D ‘ 4 ‘ t , . ; : . ; ’ oa A . n i y U 4 t a 4 uty e ‘ \, y we + fe (. n . » j M * Mi } Y ‘ DIRE RMN Yana as ilps! 4 aatF any poy a / dienes ‘ ¢ os 2 0 ¢ bok Aa ” : ‘ & ; a 5 catiee 8 D » 1 > 41 lowish in color than those from squares. The length, including the snout extended, ranges from one-eighth to three-eighths of an inch, with the breadth of the body equal to about one-third of its length. The snout is about one-half as long as the remainder of the body. Its diameter is equal to about one-eighth of its length. It is but slightly curved (see Pl. I, fig. 2) and is of a shiny dark-brown color. The antenne, or ‘‘feelers,” are attached to the snout slightly nearer to its tip than to the base. The head is small and conical in shape and partly covered by the following segment. This segment, the prothorax, is about two-thirds as long as it is wide. The scales upon it are most numerous along the middle of the back and upon the sides. The sides through the middle half of the body are approximately parallel. The back is coarsely punctate, and the entire body is more or less thickly covered with hair-like yellow scales. These scales may become rubbed off, leaving the dark-brown color of the body more apparent. The legs are rather stout, the femur being club shaped, and bearing on the inner side at the thickest part a stout tooth. The fore pair alone have two of these teeth. (See Pl. X, figs. 40 and 41.) The size, shape of the body, color, and two teeth upon the forelegs are sufficient characters by which to separate, as a general rule, this species from the others commonly mistaken for it. (See p. 64, Pls. X, XI, and X11, figs. 40 to 57.) SIZE OF WEEVILS. Size of boll weevils is an especially variable quantity, and, as usual, varies almost directly in proportion to the abundance of the larval food supply and the length of the period of larval development. The extremes are so great that the smallest and largest weevils would be thought by one not thoroughly familiar with them to be of entirely different species. So far as dimensions may convey an idea of the size, we may say that the weevils range from 3 to 8 mm. (4 to % inch) in length, including the proboscis extended, and from 1 to 3 mm. (5 to 4 inch) in breadth at the middle of the body. (See PL. I, fig. 1.) RELATION OF SIZE TO FOOD SUPPLY. The smallest weevils are developed from squares which were very small, and which, for some reason, either of plant condition or of additional weevil injury, fell very soon after the egg was deposited. The supply of food was not only small, but also, owing to the imma- turity of the pollen sacs, its quality was poor. Normally squares con- _ tinue to grow for a week or more after eggs are deposited in them, and | such squares produce the weevils of average size and color. The largest weevils are produced in bolls which grow to maturity. _ In them the food supply is most abundant, and the period of larval 42 development is several times as long as it is in squares. Possibly these differences in size may be better shown by a summary of observations which were made upon the weight of adults. WEIGHT OF ADULTS. The weevils used in these experiments were bred to insure their coming from the proper source. After emergence they were fed for some time to bring them up to their normal weight. TaBLteE VII.—Summary of weight of weevils. | | Average Source of weevils. , Number. | weight | Grain. Bredairom: pi¢ked'small squares 5-5 23 oss 5625 2 oe ees Se eee eee oe eee eee 25 | 0.105 Bred. fromuaverare fallen squares! <2< «assess coc sacle eee eee cease cecmemeas 68 . 231 Bred from: lars eypOUS) cc. ake ceteee jacw one mena te He Se eis CRE ee ee Eee | 69 | . 268 Ota. a8 See ince ners SS a As See, Gh se Sea eae Rie oe ci ee 162 36. 825 Average weight, per Weevil; all"sOUnCeSE (fess. nace eat aes ae eee eee | ast Seats pean It should be noted that these figures do not nearly represent the weight of the extremes in size, but they do indicate the difference in the average weevil of each class. COLOR. Color is very often a variable character in insects, and the boll weevil presents considerable range in this respect. Whatever influ- ences the size of the larva affects directly the size of the adult, and it is noticeable that weevils of the same size are also, as a rule, closely alike in color. In general, the smaller the size of the weevil the darker brown is its color; the largest weevils are light yellowish brown. Between these two extremes are the majority of average- sized weevils, which are either of a gray-brown or dark yellow-brown color. Weevils developing in large bolls, having an abundant food upply and a developmental period averaging more than twice that of weevils in squares, are larger in size and more yellowish in color than are those from squares. : The principal reason for the variation in color lies in the degree of development of the minute hair-like scales, which are much more prominently developed in the large than in the small specimens, although the color of old specimens is often changed by the rubbing off of the scales. The scales are yellow in color, while the ground color of the chitin bearing them is a dark brown or reddish brown. When the scales are but slightly developed, as seems to be the case with small weevils produced from underfed larve, the dark-brown ground color is predominant, while in the case of large weevils pro- duced from larye having abundant food and a long period of devel- 43 opment the scales are largely produced and give the strong yellow tone to the color which is characteristic of them. The development of the scales appears to take place mostly after the adult weevil has become quite dark in color but before it becomes fully hardened. They seem, therefore, to be a sort of nonessential aftergrowth which depends upon the surplus food supply remaining after the development of the essential parts of the weevil structure. SIZE AND COLOR NOT INDICATIVE OF SEX. Eminent coleopterists have studied the boll weevil most carefully with the purpose of discovering some external character by which the sexes could be distinguished, but all have failed to find any reliable points of distinction. The writer therefore does not hesitate to own that he also has failed to find any reliable character for the distinction _of the sexes. Many persons have the idea that the small dark weevils are males and the larger and lighter-colored brownish-yellow weevils are females. This idea is a mistaken one. In general it is probably _ true that the males are slightly smaller than the females, but judging from determinations of the sex of many hundreds of weevils, it may be stated positively that size and color are characters which are _related to food supply and length of the period of development and are not indications of sex. .The sexes seem to be about equally rep- _ resented among the smallest as well as the largest weevils. SECONDARY SEXUAL CHARACTERS. Characters commonly used to separate the sexes in the family Cur- culionide are not always distinctive in this species. As a rule the antennee are inserted nearer the tip of the snout in the male than in ) thefemale. This character is variable among boll weevils; and though /alarge number of accurate measurements might show that a slight | difference generally exists, it is too inconspicuous a character to be of general use. With most species the top of the rostrum of the male is | rougher than is that of the female. However it may be with other species, there is but little if any difference in this respect between the / young adults of the boll weevil. As the individuals become older the greater a¢tivity of the females serves to wear the roughness from | the top of the rostrum, and thus gradually, as a result of different | habits, this character becomes more distinctive. In less than half of | the. boll weevils, however, is this character sufficiently noticeable to separate the sexes. The terminal segment of the abdomen shows no external difference in either sex, although in many weevils important | characters are there found. PROPORTIONS OF THE SEXES. | No reliable secondary sexual characters having as. yet been discov-| ered, the certain determination of sex therefore rests solely upon the id primary characters, thus requiring a certain amount of dissection in each case. Such determinations have been made upon large numbers of weevils taken in the field and upon many bred in the laboratory at various seasons of the year. The results are briefly summarized in Table VIII: TaBLeE VIII.—Proportions of the sexes. | Number | Number of of males. | females. Seasonyoie1902. bothsbrediand trom: field eaccesa scaecen cot nee cee eee eee 240 260 eibernatedsweevils; 1902-3 6 ae aes con ene een a eee ee ae eee eee eee 269 174 Hirstiseneration, W903 2. Scatetses cece semaeice at cee eee ae eee e Serta aaa 43 8 32 Bred WeEEVilG AL GOS cae oe Scere terns See selec te ae me era ee ne Oe eee ene ee eae 45 33 icldsweevilss:midsummenrwd903 ssf. oa sense Sac eas eee eee ee 52 59 Weevils taken in hibernation, January to March, 1904. ..-....:2.. 2.4... .-.-.-.- 201 159 Weevils collected before hibernation, 1903, and after emergence from hiberna- ATO deg AT)! Ge en a a ane ere St RIE oe es eel = ae oe SRN aOR ooo Cacao de toee 599 338 | se Sec Cane ORAL oe Sa ee ee ee Ans eel a eS ee oe | 1,449 | 1, 055 | From these 2,504 determinations it appears that males are some- what more numerous than females, the percentage being nearly 58 of males to 42 of females. It is noticeable, however, that the only season at which a preponderance of males occurs is during late fall. If we exclude the figures for hibernated weevils for a moment, we find that the totals for the balance of the season are remarkably close for the two sexes, being 380 males and 384 females. It seems safe to say, therefore, that the sexes are practically equal in numbers except that more males than females seem to be found among hibernating weevils. It has been shown by breeding experiments conducted at low tempera- tures that the retardation of development, such as is due to approach- ing cold weather, favors the development of males. Not only was there a larger number of males than of females taken in December, 1902, but there were also more males than females taken in the field in the spring of 1903 among the hibernated weevils which lived through the winter. According to the determinations made, 64 per cent of the 259 weevils dying during the winter were males and 56 per cent of the weevils living through the winter were also males. Considering only weevils taken during or near hibernation time, it seems that during that period over 61 per cent are males and 39 per cent are females. Since it appears that females require fertilization in the spring before they begin to deposit eggs, the preponderance of males at that time acts as a provision to insure the propagation of the species. DURATION OF LIFE UPON SQUARES. The observations made along this line may be divided into eight groups, each dealing with some special food condition or class of weevils. For the confinement of weevils in the laboratory the most satisfactory apparatus tried, both for convenience in handling and for 45 the maintenance of favorable conditions for the weevil, was made up as follows: A 4 or 5-inch shallow earthen saucer, such as is used with flowerpots, was filled with soil, which was kept fairly moist. Over this was placed a fresh cotton leaf, which conserved the moisture from the soil, but never became wet, and kept both weevils and squares clean, besides facilitating the handling necessary to frequent renew- als of the food supply and the consequent transference of the weevils. The rest of the cage was formed by an ordinary lantern globe covered at the top by cheese cloth held firmly in place by a rubber band. With this apparatus weevils could be readily observed without disturbing them, and food supplied was kept in good condition and could be easily renewed, while there were no cracks to hide in-or to allow weevils to escape (PI. V, fig. 22). The moisture of the soil and fresh leaf covers were renewed as needed. Clean squares were supplied each day, and the actual number of egg and feeding punctures recorded upon numbered slips kept with each cage. The sex of each weevil was also determined and noted upon its death, thus giving an accurate record of the number and sex of weevils responsible for the punctures recorded.. Most of the weevils used were bred, so that the exact period of their lives is known. Duration of life refers only to adult life from the time of emergence from the square or boll to the death of the weevil. Many weevils brought in from the field were under observation in the laboratory for periods sufficiently long to justify the inclusion of the results obtained from them with those of weevils which were bred. Obviously the time these were under observation does not represent their true length of life; therefore the inclusion of both results renders the averages obtained the more conservative. TaBLe 1X.—Duration of life of weevils upon squares. Males. Females. 7 ay | Average |» 4, | Average Number. days. Number. days. Weevils placed in hibernation Dec. 15, 1902; living Apr. 15, LIU 28 doe cena oe cn acate AEE AOE Cee a OBE a AO mE tee Melee irri n eerie 23 180 14 171 Hibernated weevils taken spring, 1903; estimated adult Dec. BED NDE see rate pa eye neta eee rayeied Sie eva ve oieveretie eateie lee cee leie iis GE eicieine ee 66 223 53 220 'Hibernated weevils, from time of feeding in 1903 ............ { ae Be ne a Barras cocranioum bred tke. ssse8 easeaeee citi ei oe se oe | 30 58 25 56 BPPEGECENMET ALON DNC Cesar toe ey secer nies see ners crete a eiacore wie. | 18 43 10 54 Buheocneration. bredivn. cs. ease ee eee cae ote 9 76 9 54 Totals and weighted averages, including hibernation period. 146 | 151 | 111 ~ 148 Totals and weighted averages, not including hibernation period.... aodcoocoSdecoscou suc osoood ag cdancbsobcoousooadude 147 | Til 112 64 Entire duration of life, hibernated weevils only.............. 89 212 67 210 Whether we include the time of hibernation or not, it appears from the averages of 156 hibernated weevils that those which winter suc- cessfully are longer lived than any following generation, as their active life in spring averaged fully 80 days for males and 70 for females. 46 Probably the greater activity of the first generation may account for their somewhat shorter life. The average aetive life period for all generations is probably not far from 71 days for males and 64 days for females. DURATION OF LIFE ON BOLLS ALONE. As weevils appear to feed freely on bolls in the field after the period of maximum infestation has been reached (PI. V, fig. 23), these tests were made to determine whether they might be able to live normally with no other food. A number of weevils were placed upon bolls as soon as they became adult. Others which had first been fed upon squares were given bolls after they had become hard and had shown themselves to be in a nor- mally healthy condition. Of the total 37 weevils thus tested, 16 were males and 21 were females. The males showed an average duration of life of 19.7 days, while the females survived for only 15.2 days. This is amuch shorter period than the normal period of life upon squares for either sex. There are also indications that the production of eggs does not continue normally when bolls alone are accessible for food. DURATION OF LIFE ON COTTON LEAVES ALONE. “i To determine whether they could liye upon the foliage of cotton J alone 69 newly transformed weevils were at the 1st of October, 1902, | placed upon fresh leaves, which were renewed at frequent intervals. During the first three weeks 52 of these weevils (21 male and 31 female) — died, leaving 17 alive and well; 11 of these were then returned te squares and 6 continued upon the leaves. Of these 6, 3 Hved to be | 81 days old and were then intentionally killed for dissection. The | average duration of life of those kept entirely upon leay yeS Was Over 30 days. | In another test 310 weevils were placed upon loves alone during | October, 1904. Seventy-four per cent of these died in less than 10 @ days, while 7.4 per cent lived for an average of over 38.3 days, when they were placed in hibernation. Ina check experiment on 42 wee- J vils, 43 per cent died in less than 5 days, and 24 per cent lived for an | average of 36 days. As in the preceding experiment, a large propor- tion died within a few days. Among those surviving the first eritical | period, 31 per cent of those on foliage lived to an average age of 38.3 | days, and 42 per cent of those on squares lived to an average age of | 35.9 days. Itappears, therefore, that leaves alone are very efficient i in sustaining life late in the fall, as cal as early in the spring (see p. 54). These results show clearly the ability of many of the weevils to live upon foliage aloné in the fields in which fall grazing is practiced until it becomes sufliciently cold for them to go into winter quarters (see | PI. VI, fig. 24). fp Be DURATION OF LIFE WITH SWEETENED WATER AND WITH MOLASSES. So much has been said about the attraction of molasses for the weevils that tests were made with a cheap grade of molasses diluted with from 20 to 25 parts of water to see whether this solution really served them as food. The weevils used were just adult and had taken no other food. They fed quite readily upon the solution, remaining quietly with their snouts in the water for from a few minutes to an hour and a half ata time. The solution did not seem to draw them from any distance, but as soon as a weevil came to it, it would stop to drink. Feeding or drinking took place daily or oftener until the death of the weevils. The average duration of life for the 12 weevils used was a little less than 6 days. As weevils without food but with water lived an average of 5% days, the conclusion is that a solution of molasses 1 to water 25 parts does not serve the weevil as food, since it does not noticeably prolong life. Six weevils just emerged kept upon undiluted molasses showed a : greater period of life, these dying at an average age of 11% days. DURATION OF LIFE WITHOUT FOOD, BUT WITH WATER. These observations were made during August as a check upon those without water. The 8 weevils used were just adult and had never fed. Hach weevil drank for one or two minutes at least once each day so long as it lived. All died at nearly the same time, having lived for an average of about 54 days. As those without water lived an average of 5 days, it appears that access to water in the absence of food does not materially prolong the life of the starving weevils. DURATION OF LIFE WITHOUT FOOD OR WATER. Three series of observations were made along this line. In the first series the weevils used were taken immediately after emergence and never allowed to feed. Fifty weevils were tested in this way during duly and August and showed an average period of life of 5 days from the date of emergence. A few lived as long as 8 or 9 days. These /mever acquired as dark a color nor as great a degree of hardness as is normal. _ Inthe second series the 15 weevils used were 7 wecks old and full fed at the time of beginning the test. These showed an average dura- tion of life of slightly over 6 days, the range being from 5 to 9 days. These weevils were tested during the latter half of November, and the lateness of the season, together with the full-fed condition of the weevils, seemed to promise a considerably longer period than 6 days. In the third series the 18 weevils used were 1 month old and full-fed at the beginning of the test in the middle of November. The condi- tions in this series were as in the series preceding, with the exception 48 that an abundance of two species of grass taken from cotton fields was ee These weevils showed an average duration of life of nearly y days, ranging from 3 to 10 days. The weevils made no effort to a upon the grass, so the slightly longer life period must be due to other causes. CANNIBALISM. It is hardly proper to speak of cannibalism as a food habit of the boll weevil, but the facts observed 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 6 only were alive. Of the seventh only the hardest chitin- ized parts (head, proboscis, pronotum, legs, and elytra) remained, the softer parts having been eaten by the survivors. In another box containing 12 adults the leaf supplied for food was insufficient, and on the fourth day 8 were dead, 4 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 pup 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 ‘‘reddish-brown” adult was found having its elytra eaten through 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 is really the clearest case of cannibalism 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 larvee, while in a few cases the actual death struggle was observed. FOOD HABITS. Among the habits of any insect of economic importance, the first for careful study are those relating to its food, and the second, those connected with its propagation. The study of the life history of the — boll weevil has revealed no especially vulnerable point, but rather the important fact that in all its stages it is better protected against the | attacks of enemies and the ordinarily effective remedies recommended by the economic entomologist than any other insect which has ever threatened the production of any of the great staple crops of this country. Naturally, then, we must needs turn to a study of the habits of the pest to point the way to means by which either it may be itself destroyed or its great destructiveness prevented. Bul. 51, Bureau of Entomology, U. S. Dept. ofAgriculture. PLATE VI. VARIOUS RESULTS OF LARVAL WORK. Fig. 24, Leaf fed on extensively by weevils in confinement; fig. 25, full-grown larva in square ready to bloom; fig. 26, full-grown larva in square of usual size; fig. 27, larva full grown, ovary in square entirely destroyed: fig. 28, larva full grown, ovary untouched—all reduced to two-thirds natural diameter (original). Bul. 51, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE VII. VARIOUS EFFECTS OF WEEVIL ATTACK. Fig. 29, Boll showing two locks destroyed by one larva; fig. 30, weevil in act of forming an egg puncture; fig. 31, square riddled by feeding punctures: fig 32, bloom distorted by many feeding punctures made when about to open, fig 33. comparison of flared square with normal square— all reduced to two-thirds natural diameter (original). ay ogy ee Sequanyseateans Ad BY, Me? 14 ‘ ee ! x : ek, ‘ € \ j 4 ‘ aed i 4 ¥ \ 4 ‘ ‘ - * he ‘ ‘ ‘ ' ‘ J Ld ‘ ; ‘ 5 ; f 4 ¢ : Peat u / of fies ‘ i 4 ive ' 4 ‘ / . ; ! t f r ee alae ‘ 49 LARVAL. / It is plainly the intention of the mother weevil to deposit her egg so that the larva upon hatching will find itself surrounded by an abun- dance of favorable food. In the great majority of cases this food con- sists principally of immature pollen. This is the first food of the larva, which develops in a square, and it must be both delicate and nutritious. Often a larva will eat its way entirely around the inside of a square in its pursuit of this food. In most cases the larva is about. half grown before it feeds to any extent upon the other portions of the square. It may then take the pistil and the central portion of the ovary, scooping out a smoothly rounded cavity for the accommoda- tion of its rapidly increasing bulk (PI. I, fig. 4; Pl. ILI, fig. 10; Pl. VI, fig. 25). So rapidly does -the larva feed and grow that in rather less than a week it has devoured two or three times the bulk of its own body when fully grown. It sometimes happens that the square is large when the egg is deposited therein, and the bloom begins to open before the injury done by the larva becomes sufficient to arrest. its development. In many cases of this kind the larva works its way up into the corolla and falls with it when it is shed, leaving the young boll quite untouched (PI. VI, fig. 27). Occasionally the flower opens. and fertilization is accomplished before any injury is done the pistil,. and in rare cases a perfect boll results from a truly infested square. Sometimes the larva, when small, works its way down into the ovary before the bloom falis, and in such cases the small boll falls as would. a square. In large bolls the larve feed principally upon the seed and, to some extent, upon the immature fiber. A larva will usually destroy but. one lock in a boll, though two are sometimes injured (PI. VI, fig. 29). | When the infestation is severe a number of weevils, occasionally as: many as six or even more, may be developed i a single boli, which is completely destroyed by the feeding of the larve. ADULT. Before escaping from the ee the adult empties its alimentary eanal of the white material remaining therein after the transforma- tion. The material removed in making an exit from the cell is not used as food, but is cast aside. Weevils are ready to begin feeding very scon rn they escape from the squares or bolls in which the previous stages have been passed. For several days thereafter both sexes feed almost continuously, and seem to have no other ies in life. They will take squares, bolls, or leaves, but they much cree the squares, and when sguares are present in the field it is probable that leaves are seldom touched. As has been shown, however, weevils: 16780—No. 51—05 4. 50 can live for a long time upon leaves alone when squares and bolls are wanting. Bolls are only slightly attacked so long as there is an abundance of clean squares. _ The method of feeding is alike in both sexes. The mouth parts are very flexibly attached at the tip of the snout (fig. 2) and are capable of a wide range of movement. The head fits smoothly into the prothorax like the ball into a socket joint and is capable of a con- siderable angle of rotation. The proboscis itself is used as a lever in prying, and helps to enlarge the puncture through the floral envelopes especially. Feeding is accomplished by a combination of movements. The sharply toothed mandibles serve to cut and tear, while the rota- tion of the head gives the cutting parts an auger-like action. The forelegs especially take a very firm hold upon the square and help to bring a strong pressure to bear upon the proboscis during certain portions of the excavating process. The outer layer of the square, the calyx of the flower, is naturally the toughest portion that the weevil has to penetrate, and only enough is here removed to admit the snout. After that is pierced the puncture proceeds quite rapidly, combinations of chiseling, boring, and prying movements being used. While the material removed from the cavity is used for food, the bulk of the feeding is upon the tender, closely compacted, and highly nutritious anthers or pollen sacs of the square. When these are reached the cavity is enlarged, and as much is Fig. 2.—Mexican cotton boll eaten as the weevil can reach. The form of weevil: Bead crowns ** the entire puncture becomes finally like that middle and mandibles of a miniature flask. ere enlarged Only after weevils have fed considerably do i sexual differences in feeding habits begin to appear; from this time on the females puncture mainly the base and the males the tip of the square. Feeding punctures are much larger and deeper than are those made especially for the reception of the eggs (Pl. II], fig. 8); more material is removed from the inside of the square or boll and the opening to the cavity is never intentionally closed. Feeding punctures are most frequently made through the thinner portion of the corolla not covered by the calyx. The exposed tissue around the cavity quickly dries and turns brown from the starting of decay. Asa number of these large cavities are often formed in one square (Pl. Vil, fig. 31), the injury becomes so great as to cause the square to flare immediately, often before the weevil has ceased to feed upon it. Squares so severely injured fall in a very short time. The injury caused by a single feeding puncture is often overcome by the square which con- = ag 4 feng NS enh 1 he Bi SL 51 tinues its normal course of development. When feeding punctures are made in squares which are nearly ready to bloom, the injury com- monly produces a distorted bloom (PI. VI, fig. 82) and in very severe cases the boll will drop soon after setting. After the females begin to oviposit their feeding habits become quite different from those of the males. Up to this time both sexes move but little, making a number of punctures in a single square; but from this point we must consider the feeding habits of the sexes separately. MALE. Studies of the feeding habits of males have been made both in the laboratory and out of doors.~ In the laboratory 65 males were under observation during a total period of 2,492 weevii-days.* During this period 2,185 squares were supplied them and they made 5,617 feeding punctures in 1,582 of thesesquares. A little calculation shows that they averaged to make 34 feeding punctures in each square, at the rate of 24 punctures a weevil each day. These observations were in most cases made during the latter part of each weevil’s life. During the first few days they have often been found to make from 6 to 9 punctures a day. A general average of 3 feeding punctures a day in the laboratory would seem to be near the actual figures during the warm weather. As each male while under observation attacked only about 2 squares every 3 days, the destructiveness of males seems comparatively slight. As will be seen in the following paragraph, the injury done by males in the’ field is not greater than that indicated by the laboratory obser- vations. Five males were followed upon plants under a field cage for a total period of 145 weevil-days. During this period they attacked 68 squares, making therein a total of 177 feeding punctures. This means an average of 2.6 punctures per square and an average of 1.2 punctures per male per day, making the number of squares attacked by each male less than 1 every 2 days. These outdoor observations indicate that the laboratory results, small though they appear, are yet higher than the actual field numbers. Whether in or out of doors, the activity of feeding decreases as the male grows older. Males choose to puncture more often than do females through the tip portion of the square not covered by the calyx. The yellow or orange-colored excrement is abundant, and owing to the somewhat sedentary habits of the males it accumulates often in quite large masses, so that it is often possible to tell whether a square in the field has been attacked by a male rather than a female weevil. “The term ‘‘weevil-day”’ is used for convenience to designate the product of the two factors: number of weevils multiplied by the number of days. D2 FEMALE. . After they begin to oviposit females seem generally to feed less upon one square or in one puncture than they do previous to that time. They obtain quite a considerable portion of their food from the excavations which they make for the deposition of their eggs, and as they show a strong inclination to oviposit only in clean or pre- viously uninfested squares, their wandering in search of such squares keeps their punctures scattered so long as plenty of clean squares ean be found. When clean squares become searce, the normal inclination can not be followed out, and the number of punctures made in one square will be greatly increased. Most of the special feeding punc- tures of females appear to be made either in the early morning or near sundown, the middle and warmest portion of the day being given mainly to egg deposition. The total amount of feeding done is really very large, as is shown by a few figures. MALES AND FEMALES TOGETHER. During the season of 1903 a large number of weevils were kept in the laboratory for special study, but as several weevils were confined in each cage, the work of the sexes can not be positively separated. A comparison of the results can best be made by means of a tabular arrangement of the figures. Taste X.—Number of punctures per weevil per day. Total. Average. A Fie ely | Number | Feeding Hgg See eucacl on ot age |) Of fe= AWeeoane| Feeding Kgg pune- pune- |Period of Ses aan eemevles: Beas. Wale pune- | tures per) tures per | observa- | ys. tures. tures. weeyil- | female- tion. day. day. Hibernated weevils | Days. TM A OOKAvOLVe see ee 5d 04 | 4,938 | 17,406 5, 702 3.504 2.3+ 45,.3+ Hibernated females | idl ITC CNRS Geo coko) Sonosueeee 4 $3 | 284 489° 3.0+ 5. 3-- 23.3— WVeevils of first gener- | ation in laboratory - 31 27 | 3,258 | 16,487 38, 565 5.0+ 2.4— 56, 2— Females, first gener- aon mimmuteld eagers|secs esse se 5 | 70 | 263 435 3. 8— 6.2+ 4.0 Males only, labora- | tory, summer of 1903. Cae ete ee 2, 492 | Oli als et eee DES al eae te ees 338.3+ otal ower ne 151 90°! 10,851.) .40; 057) 10: 191] Saas eet eee cee seen aes FEEDING OF HIBERNATED WEEVILS ON EARLY COTTON. During the period in which hibernated weevils were coming from their’winter quarters and seeking their first food, frequent examina- tions were made in fields where the cotton was most advanced to learn the first-food habits of such weevils. From statements made by pre- vious investigators the writer is led to believe that the season of 1903 at Victoria was abnormal in respect te the small number of hiber- nated weevils which were to be found upon the young cotton in the field. The most careful search failed to discover more than a very wt ee a ke ST en A ae TR Py SF a hetabiiet ok rd 53 few weevils, whereas at the same season in some years hibernated weevils have been picked in large numbers from the young cotton growing in the infested territory. At Victoria in 1904 hibernated weevils were many times as numerous as In 1903. Whether there be few or many hibernated weevils, however, makes no difference 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. Owing to the extremely wet winter and the very late spring of 1903, little cotton could be planted until the latter part of March or the first part of April. [ In 1904 much cotton planted in March in the southern part of the State did not break ground until the latter part of April owing to the dryness of the soil from lack of spring rains. In such eases as these, therefore, cotton must be small at the time of the emergence of many of the weevils from hibernation, and some time must elapse before the formation of the first squares furnishes the early weevils with the normal food supply: During this interval the weevils get their food from the tender, rapidly growing terminal portions of the young plants, as several observers have noted. The central bud, young leaves, or the tender stems are attacked, and upon these the weevils easily subsist until the squares are developed. In 1896 Mr. Marlatt noted: ‘‘ The eating in the field on volunteer cot- ton is practically confined to the young expanding leaves at the bud and to the tender petioles or stems of this portion of the plant.” —_ TIME HIBERNATED WEEVILS CAN EXIST ON FOLIAGE BEFORE FORMATION OF SQUARES. The suggestion has been frequently made that by delaying the planting of cotton until late in the spring the weevils emerging from hibernation might all starve to death before the cotton would be in condition to furnish them with a food supply. In regard to this suggestion, several factors must be considered. (1) The average period of emergence from hibernation in localities where observations have been made may extend from some time in March, frequently as early as the middle of the month, to the very last of May, or possibly the first of June. It is impracticable to delay the planting of the crop until the first of June. In the northern por- tion of the State this late planting would not allow a sufficiently long season for the development of the crop before early frosts occur in the autumn. In the southern portion of the State the occurrence of a considerable amount of seppa”% or stubble cotton would furnish the a “‘Seppa’’ is the term used by Mexican residents of south Texas to differentiate the cotton plants springing from the roots of the previous year from those strictly | ‘‘volunteer,’’ springing from accidentally scattered seeds. ‘‘Stubble’’ and ‘‘stump- age’”’ are other terms similarly applied to second-year growth of cotton, and have the same meaning as ‘‘seppa.’’ 54 _ weevils with a sufficient food supply and defeat the very purpose of delaying planting. | (2) The period from the time the cotton breaks ground until the formation of squares begins varies considerably, but in general may be considered as averaging about six weeks. | (3) A large number of observations have shown that many weevils will, under ordinary conditions, emerge from hibernation after the cotton has broken ground, but before the formation of squares begins. These weevils experience little difficulty in living upon the cotton foliage through a period of at most six weeks. The observations made relate especially to Victoria, but will naturally apply to points farther south. During mild winters the weevils become active through inter- vals of warm weather, and may be found moving about on the cotton plants as though seeking food, and these weevils would undoubtedly feed at such times if food were available. Under these same condi- tions, however, a large majority of the hibernating weevils will not emerge until from five to eight weeks after the growing season of cot- ton begins. During severe winters and in the northern portion of the State, the immature stages appear to be killed in the squares and bolls during the winter, so that only those which hibernate as adults sur- vive. Those adults which are most exposed probably perish also, and naturally those which are best protected against the cold will also be most protected from the heat during the spring, and, therefore, emerge late. Late planting, therefore, delays the crop and really gives the hibernated weevils an advantage. To make the laboratory tests as severe as possible, weevils were taken from hibernation very early in the spring, the dates ranging between January 23 and April 5, 1904, averaging March 23. Alto- gether 110 weevils were used. ‘The food supply consisted entirely of the terminal portions of cotton stems, which were replaced by fresh tips at frequent intervals. Under these conditions one-half of the weevils under observation died in a little over six weeks, the average length of life being really forty-five days. A number of individuals continued active for more than three months. These tests showed that even under most unfavorable conditions fully one-third of the hibernated weevils might be expected to live for a period of time longer than that usually occurring between the planting of cotton and the first formation of squares. CONCENTRATION OF WEEVILS UPON MOST ADVANCED PLANTS. The earliest plants in the field ultimately attract most of the weevils, and where seppa plants occur they may serve as traps to draw the first -attacks. Thus, in the spring of 1895, Mr. E. A. Schwarz found the first emerged hibernated weevils working upon seppa plants which had sprung from 2-year-old roots. These plants, having their root he A ae a A dpi: oO YR i he ie Ai a tae ts 2 8 55 systems well established, start earlier and grow more vigorously than do those from seed, and are therefore doubly tempting to the hungry weevils that emerge early in the spring. In the spring of 1903 in one field of comparatively early cotton, 2 or 3 acres in extent, the writer found, between April 24 and May 11, 23 weevils working on the buds and tender leaves of seppa plants before a single weevil was found on the young planted cotton having from four to eight leaves. At Victoria early in June, 1902, Mr. A. N. Caudell found, in examining 100 seppa plants, growing in a planted field, that fully one-half of the squares upon these plants were then infested. The planted cotton was just beginning to form squares, and was slightly injured at that time. It appears, therefore, that seppa plants, where such exist, receive a large part of the first attack of the hibernated weevils. Several reasons may be given in explanation of this condition. These plants, often appearing above the ground before the planted cotton, naturally draw the earliest weevils, and as the movement of the weevils is very slight at this time of the year, these weevils may very certainly be found upon those plants where they find favorable food. In the natural process of selection, the largest and most advanced plants would naturally be expected to draw the attack of a large proportion of the weevils which might emerge, even after the planted cotton had broken ground. Itis by no means certain, however, that all hibernated weevils may be found upon these early plants. The comparatively small number of seppa plants makes it an easy matter to examine them with much more care than can be given to the large number of small plants. A number of observations have shown that weevils fre- quently occur upon the planted cotton even when numbers of vigor- ous seppa plants may be found within a comparatively short distance. (It has been conclusively shown that the first squares do not exert any such strong power of attraction to the weevils as has been hereto- fore supposed. Weevils which have fed upon the tender tips of plants seem perfectly satisfied with their food supply, and it is quite evident that their first meal upon squares is more the result of accident than | intention. After having begun to feed upon squares, however, it appears that their taste becomes so fixed that they normally seek for squares. It has been found that females do not develop eges until squares have been fed upon for a period of several days. They have, therefore, no especial impulse to seek squares for the purpose of ovi- position, which has hitherto been considered their prime motive in their early spring movement. | The concentration of the weevils upon plants having squares takes place very gradually. Opportunities for observations at Victoria during the spring of 1904 were exceptionally favorable, and it was found that many weevils still remain upon plants not having squares for fully six weeks after numerous plants growing 56 in the immediate vicinity had begun to form squares. These observa- tions were very conclusive, and were sufficient to prove the ineffective- ness of trap rows, even under the most favorable conditions. ARE WEEVILS ABLE TO LOCATE A FOOD SUPPLY AT ANY CONSIDERABLE DISTANCE? One would naturally think that insects so highly specialized as to have only one food plant would be provided with some remarkable ability for detecting the location of that plant and for enabling them to reach it from a considerable distance. Experiments were under- taken by Dr. A. W. Morrill to determine whether the boll weevil had any strongly marked sense of the direction of its food supply. Various methods of testing were employed. In experiments 1 to3 a piece of glass about 20 by 24 inches was allowed to rest upon eight glass tubes pla se at the angles and middle of each side and directed toward the center of the siiss. The space between the tubes was care- fully filled ay cotton. In certain tubes a supply of cotton squares was provided. In ue other green vegetation was placed. The weevils were liberated under the middle of the glass and allowed to move freely in any direction, the object being to see if any consider- able proportion of them would choose the tubes containing squares. In experiments 4, 5, and 6 a cylinder 2 inches in diameter and 18 inches in length was constructed from wire screening. This allowed free circulation of the air and free movement of the weevils in either direc- tion. A supply of squares was placed outside of one end of the cylinder and various eee vegetation at the opposite end. Observations were made to determine the proportions of weevils found nearest the food supply or ree from it. The various conditions of light and heat were so changed as to determine their influence and equalize the effect upon the movement of the weevils. In the course of these experiments over 250 observations were made upon 100 weevils. A summary of the results shows that 83 weevils were found as near the cotton as they could get, while 90 weevils were as far from it as they could be. One hundred and sixty-one weevils were nearer to the cotton than to the. other vegetation, while 193 weevils were nearer to other vegetation than to cotton. In no case did the maximum possible distance from the cotton squares exceed 20 inches, and the minimum varied from 1 inch to immediate access to the squares. All weevils were hungry and many starved during the period of observation. At no time was there a general movement in the direction of the food supply. Considering these results it can not be said that these weevils showed a definite sense of the direction of their food supply, or any attraction to it from a distance, even so short as 1 foot. The reactions to light and heat were bot th positively marked and much more evident than the reaction to food supply. t 4 ? 57 It must not be inferred that we believe weevils have no sense by which to locate their food supply, but it is apparent, both from these observations and from observations made in the field, that the move- ment of the weevils is indefinite, and the probability is that their find- ine cotton is more the result of accident than of evident intention. Since it has been found that weevils may live for a number of days after emerging from hibernation without food, they have considerable opportunity to move about and stand a considerable chance of finding food if it exists in the immediate locality. DANGER FROM ALLOWING SEPPA TO GROW. Tn this connection attention should be called to the serious danger of allowing seppa to grow. It might appear that in localities where there is sufficient seppa to give a fair stand, there would be the decided advantage from the earliness of this growth in attempting to make a crop from these plants. Such, however, is not the case, as has been conclusively shown by the experience in south Texas during 1904. Winter conditions favorable to the survival of the cotton roots favor also the successful hibernation of many weevils, and large numbers of these- attacking the crop in the spring are certainly fatal to the production of even a fair crop. -The conditions and practices which result in seppa growth are those most favorable to the weevil. Southern Texas, where seppa is most common, is the very portion of the State which can profit most easily and most certainly by adopting the fail destruction of the stalks, and the subsequent plowing, which will not only prevent seppa growth, but will also insure the destruc- tion of a vast majority of the weevils. By allowing seppa to grow in a field of planted cotton, the weevils are supplied with the most advan- tageous conditions for getting a start over the planted crop. It will frequently happen that the seppa plants are from four to six weeks in advance of the planted cotton. Under such conditions, as was dem- onstrated at Victoria in 1904, a complete first generation of weevils may develop on the seppa, thus multiplying greatly the number of weevils which are ready to attack the main crop by the time squares begin to form thereon. The development of this largeiy increased number of weevils might easily have been prevented by simply destroying all seppa plants, and the seppa growth can be more easily and more surely prevented by destroying stalks in the fall and giving the ground a thorough plowing at that time than by any measures that may be adopted in the following spring. If it should be argued that seppa furnished ideal trap rows, we would say that extensive observations have shown that they constitute a source of decided dan- ger rather than of benefit, even if preserved for the purpose of trap- ping hibernated weevils. The proportion of weevils escaping destruc- tion upon such trap plants would insure the survival of a larger number of weevils per acre than could possibly have survived under 58 a faithful observance of the practice recommended by the Bureau of Entomology. The menace from this source is certainly sufficient to justify the adoption of strong measures tending to largely reduce, if not to prevent altogether, the growth of seppa cotton. The recom- mendation made by Prof. EK. D. Sanderson, while State entomologist of Texas, that laws be passed making it a punishable offense to allow the unchecked growth of seppa cotton, seems to the writers fully justi- jable and commendable. | INCREASE IN LEAF AREA OF COTTON. The advisability of making observations upon this point was sug- gested by the attempts made to poison hibernated weevils by spraying early cotton with an arsenical insecticide. As the weevils fed so exclusively in the most recently unfolded growing portions at the tips of the stems, it was evident that-the rapidity of increase in the leat area would at least indicate the frequency with which spraying would have to be repeated in order to keep in a poisoned condition the very limited portion upon which the weevils fed. Although the observations were made after midsummer, the plants used were of the right size to indicate the points desired. Two series, each including five average plants, were selected. The plants used in Series I] had 8 leaves at the time of the first observation. Those used in Series II were older and averaged about 30 leaves each. The leaves borne upon the main stem were classed as primary and those from side branches as secondary leaves. Upon the date of each of the 5 observations made, the number of leaves in each class was ascertained, an average leaf in each class was quite accurately measured, and the total product of numbers and area thus found was considered as the approximate leaf area of the plant. The error has been reduced as much as possible by taking an average of the 5 plants in each series as representing a typical plant, and it is with these results that comparisons have been made. TABLE XI.—EHstimated increase in leaf area of cotton, averages of five plants. as Primary leaves. | Secondary leaves. = So eee Average 2 Percent- | Average x Percent- Date of examination. Soha Beare age of | number | ee age of per Tae daily in- per oat daily in- plant. P ; crease. plant. Is crease. - 1902. Series I: Sq, in. Sq. in. ACU PUIS CBO sae Saya ae ets eee tapers 8.0 GE Oi pzeeeexess (0 eel Kea ese acia aky | (Beh AG ae Septem bere 7-2 se ea os eee ees 8.6 136.8 8.0 8.0 ATs Dig (eect area Septemlberi2ae- Masao. acme eee 9,8 231.6 5.4 16.6 187.4 30.0 OCtODEr GC Sac ase ea ee ee Sr ee EO 309. 6 3.0 22.6 347.8 7.8 Octoherd 72 wissen a Bh 376. 6 2.0 31.0 522.4 4.6 Series II: AIP UST SOE oe a ees eee 7.8 ATR E SS Se ete 21.6 26088 Waele eee Heptemiberdks cos sass ee a eet 8.4 | 229512 2.0 24.8 341.4 2.0 September 2o'. ee ye ena eee 9.8 241.6 . 04 42.4 514.0 3.6 OCtOberiG ease eae eee 9.6 214.8 | a—1.0 52.6 619. 2 1.8 O ClO DEL ae Ses Oe eetce ee aieeeoee 10.0 | DAO teh Wecace CSc 67.4 808, 8 Meds — a Decrease of 1 per cent due to falling of old primary leaves, é D9 Several facts are evident from an examination of this table. After the plant has acquired about eight primary leaves the formation of branches and of secondary leaves began, thereby multiplying the number of growing points. From this time on the greater part of the increase in leaf area took place in the secondary leaves. By far the most rapid period of leaf growth occurred at about the time when squares first began to form. In Series I the average total leaf area practically doubled every ten days through the seven weeks under observation. In Series II the plants were older to start with, and it required about forty days to double the leaf area. Everyone now concedes that it is useless to attempt the spraying of full-grown cotton such as is represented in Series Il. The extreme rapidity of increase in the foliage area shown in the first part of Series I shows that spraying must be repeated every week or ten days if even one-half of the entire leaf area is to be kept poisoned. When, in connection with the large per cent of daily increase, we consider _how much of that percentage is being unfolded at the very tip of the stem; that upon that limited tip area alone will the weevil feed before the formation of squares; that after the formation of squares it | appears to be almost impossible to poison the weevil’s food supply; _and also that the irregular emergence of the weevils from hibernation may extend through several weeks; it at once becomes evident that | potsoning early cotton for hibernated weevils is almost as impracticable as the poisoning of older cotton is now acknowledged to be. EFFECTS OF FEEDING UPON SQUARES AND BOLLS. From numerous large, open, feeding punctures a square becomes so _severely injured that it flares very quickly, often within 24 hours (Pl. VIL, fig. 33).° 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 in- | jured by a male will flare before the weevil leaves it. The time of flaring depends upon the degree of injury relative to the size of the “square. Thus, small squares receiving 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 show- ‘Ing 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 (PI. VII, fig. 32), and occasionally such squares de- velop into normal bolls. In squares of medium size a single feeding puncture does not usually destroy the square. The destruction of a square by feeding results either from drying, decay, or a softened, pulpy condition of the interior, which is the consequence of the weevil injury. 60 Bolls are quite largely fed upon after infestation has reached its height. Small and tender bolls are often thoroughly riddled by the numerous punctures (PI. LX, fig. 36). Small bolls so severely injured fall within a short time. Larger bolls may receive more punctures without being so severely injured. A comparison cf the external and internal effects in such cases is shown in Plate VIU, figures 34 and 35. Abnormal woody growth takes the place of the normal development of the fiber, and a softening and decay of the seeds often accompanies this change. One or more locks may be: destroyed while the remain- der of the boll develops in perfect condition (Pl. IX, fig. 38). After the bolls become about half grown the effects of feeding are less likely to cause the boll to fail. The puncture becomes closed by a free exudation of the sap and a subsequent woody growth, which forms frequently an excrescence the size of half a pea upon the inner side of the carpel (Pl. LX, fig. 37, a). An execrescence of this. char- acter usually results from an egg puncture, and often from feeding punctures also. TaBLeE XII.—Destruction of squares by feeding alone. Fagot = Ube be: © oS o is Wien Bysg pas a, Oe © .* a = = LS RES = EAU) rae herrea Ba |) SS = Lote = ae = ak AS | Be = Oa O fae 532 ea = 2 Eel aA AB aea|ed 258 es £$.| ’S |ws- | Se | Sh6| se bees ets a eS AS HKD 25 = 2 = : [= eee Date. 9au | SB | ms? (385) Sa (eao see eee soos | =o SiS: Oge | =o |aes == 20 S005 ss ae Ons Sas OS aa sa ae SUS 22 a2] RS ee he a Oke aoa Dad Ze es wz O = Ron | SUA | Bae rs (S = 5 a ¢ S 1 Oaks Soe >¢ Ss Sos-| oe a2 |s3h3 | © Os Seon) sae e2ea)] Sa e= ora 5 |} oe2n | pak | see = = i = ee ee |< |<: UUM CsA SORT ye ae aoe. Aenea ee 334 59 210 122 Lo, |= OSs 2.0*| 5.6 August 21 to.September 10 .....-.---| B08 | 54 206 100 Hae Bs) pea tr HSS} 5.2 October.25 to November 25....-..--- | 125 41 137 110 32.8 80.0 | 2.8) J4.2 NO See 5 ed Shee Seer ee ee 51 | 26 79 70 5030) | 882651 3.1 21652 JuMe nM Oro Mitthy ol ee tes eee eee 417 | 3 125 59 CAE Vee Aha? 19 4 6.0 August 6 to September 25 ........... “68 68 177 177 |- 100.0 | 41002021 2.6 | 3.6 1, 353 279 934 638 20. 6 68.3 2:0. 7.0 aSauares attacked by male weevils only. } 1 i i From the preceding table a few genera! conclusions may be drawn. The general impression that most of the seceins ds done in squares specially devoted to that purpose is abundantly sustained by reference to columns 5 and 6, from which it is seen that one > fitth of all the squares attacked by the weevils receive over two-thirds of their feeding punc- tures. Where, as a general thing, only one ee is placed in a square, it _ appears that on an average more tha un two feeding punctures are made inasquare. A on of the average time tea m the date of attack to the f falling of the square shows that squares which are fed upon only, fall, as a rule, somewhat more quickly than - squares which contain larve only and have never been fed upon. While not shown in the preceding table flaring as a result of feeding injury takes place more quickly than when the result of injury by a larva worene within the square. 5 Bul. 51, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE VIII. EXTERNAL AND INTERNAL EFFECTS OF FEEDING ON BOLLS. Fig. 34, External appearance of feeding punctures upon large boll: fig. 35, internal injured condition of same boll—natural size (original ).° Bul. 51, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE IX. Bol L% inch y (has |S big fp Vo Fell. tiff a Bloom. Wo Boll, 2 f P Wo B oll open wo Locks had, EFFECTS OF WEEVIL FEEDING UPON BOLLS. Fig. 36, Small boll showing 13 feeding punctures; fig. 37, section of medium-sized injured boll: a, Feeding puncture closed by woody growth. b, gelatinized area resulting from feeding punc- tures, fig. 38, boll having two locks destroyed by two feeding punctures made by a male weevil: fig. 39, device used to test relative attractiveness of American and Egyptian squares—figs. 36, 38, reduced to three-fourths natural diameter: fig. 39, one-fourth natural diameter (Original). 61 DESTRUCTIVE POWER BY FEEDING. A glance at the figures in Tables X and XII (pp. 52 and 60) is suf- ficient to show the great 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 attribute this difference to the influence of a higher temperature alone, though this factor will account for a large part of it. A com- parison of the figures for males alone with those for females alone or with those for males and females together shows that it is very con- servative to say that males make less than half as many punctures as do females. By the habit of distributing their punctures among a greater number ofsquares 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 deeply impressed the entomologists who first studied the insect in Texas. In 1895 Mr. EK. 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. SUSCEPTIBILITY OF VARIOUS COTTONS. Anexcellent opportunity for observations upon this point was obtained upon the laboratory grounds at Victoria by growing within a small area plants of several varieties of American Upland, Sea Island, Egyptian (Mit Afifi), Peruvian, and Cuban cotton (Algodon sylvestre). The Peruvian cotton made a remarkably large growth during the first sea- son of growth in 1903 and again from the overwintered roots in 1904, but put out no squares, so that it does not really enter into this com- parison. The Mit Afifi seed was obtained through the courtesy of the | Bureau of Plant Industry of this Department from a field grown the preceding season at San Antonio, Tex., in which circumstances led some observers to the opinion that the variety was, to a certain extent, immune. 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. Infested squares being 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 cot- ton with equal opportunities to make their choice of food, and accord- 'ingly their location has been considered as indicating such choice. The period of cbservation extends from June to November, except 62 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 plots 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 preduct 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 comparison and show at a glance the average relative attractiveness of each class of cotton. The following table presents these results in comparable form: Taste XII1.—Relative attractiveness of various cottons. | | Total. Average. | Num- | | Relative Class of cotton. ber of | pyant-| Wee- In- Weevils intesee attract- | plants. 5G ae vils_ | fested ; per plant a wees iveness, YS: | found. |squares| per day. | P vil 1903. | : PAST CRTC aay eee rye Wee eae Are eee eee 62 | 4,920 287 | 3,507 | 0.058+ 12.2+ 1.0 CAD es ee nies aires se | 5 120 11 136 . 092— 12.4— 1.6+ Sea Eslo id ee ee Sie aes eee | 8 | 552 64 | 1,089 .116— 17.0+ 2.0 dL OFSe\ 9 OTe eeapeenee elee eeen eae eens Meare erie 8 | 808 | 207-)5 22013 . 256+ 9.74 4.44 Total of 3 non-American cottons. 21 | 1,480 | 282 | 3,238 .191-— 11. 5— | 3.3— 1904. J MAI Se CON Oe ers cere Sten sabre each ae ea aoot 60 | 3,780 SAGs eh seseee SOON Says eee se 1.0 PSCop IS) Gia eae rae eee eee ee ace 5 | 315 98) (fl ee ere Shh | see eee 4.0 SV PElaMe sac scien 2 wae a ete eee ee ee 40 252 LOD eis ne eer CO all elesiaee ear rec 4.44 An examination of these figures shows that American Upland cotton | is less subject to the attacks of the weevil than any of the others, and that Egyptian (Mit Afifi) is by far the most susceptible. The differ- ence in degree is most plainly shown in the column of ‘relative attractiveness.” It would certainly seem difficult to formulate a stronger argument for the cultivation of American cottons alone within | the weevil-infested district than is presented by these figures. The ff weevils gathered so thickly upon the Egyptian cotton that the plants | could not produce sufficient squares to keep ahead of the injury, and therefore the average number of infested squares for each weevil is only three-fourths as great with that variety as with less infested — kinds, but the average injury to each square was greater than with any other. 63 Reports made by agents of this Bureau who have investigated the habits of the weevil in Cuba and Mexico show that the native varieties of cotton, including the tree and kidney cottons of Cuba and the tree cottons of Mexico, are just as susceptible to serious weevil injury as are the cultiv viel cottons. In some restricted localities in Central America the dwarf character of the cotton grown and the very open method of cultivation result in the production of some staple, though the variety of cotton grown is by no means immune to weevil attack. The practical application of these observations may be emphasized still further by the statement that in spite of the frequent and careful removal of weevils from these cottons during the entire season none of the non-American varieties made a single boll of good cotton, so great was the actual weevil injury to them, while American cotton with the'same treatment developed a large number of bolls. The results are still further sustained by observations upon larger areas of American and Hgyptian cotton under field conditions in three localities in Texas, no weevils being removed from either kind. At Victoria, Tex., on August 26, 1908, 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 percent. Similar results were found at San Antonio. Though growing in close proximity, the Eg¢yp- 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 Egyptian 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 a cesoaile 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 breeding cage EPI. 1X, fig. 39), so lettered and numbered that each square col 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 experiment 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 XIV presents a summary of these results. 64 TaBL—E XIV.—Breeding-cage observations upon weevil choice of American and Egyptian squares. x American squares. Egyptian squares.~ nn | See esata B | a S g ae Ae eis g S| = | 2 S ee] A : eS — = S| = = ml Period of observation. ° 3 Ss g = Aa | © qi = Aw | 5 Ste RE n = oO oo 2 fs = 5) ee 2 Ss = } = Sg MA a> - S a 5 | oF) ef) eel [es |e) elmore eee =e = 2 sg S > io &0 s S.A &D ae SE aa ee ° = | o a9 iS) S | oO - 8D | Ao = ie a) eee Fel eh get bates <3 SIRE Days POI ee aes means S's 0a Tasha ale 15 5 pe 16 5 12 3 2 | si AS a ALON fo rele TIS ae eae ap. L0 16 | 5 19 hey 5 13 3 3 | 12m. to5 p. m. day after....... 5) 10) ste: 7 | 95°) 2o-)2 lie) Bamenp may 2 4) han iae MN. LOL aa mme, sete men, ne baled O) eke 6 ay, 6| 16 8 14 3 Du 6 Peal. iOS acme soc ye. eee LoS eee 2 7 One eel, 0 JNU) Sere ace ae age BA: 258 Gee] ks nears |eente | 68| 29} 76) i In experiments 1 and 2 the American squares were attacked more extensively than were the Egyptian, while in experiments 38 and 5 greater injury was done to the Egyptian. In experiment 4 the smaller number of egg and feeding punctures made in the Egyptian squares is counterbalanced by the larger number of squares attacked. Although the totals from these five tests show slightly less injury to the Egyp- tian than to the American squares, it could hardly be expected that two arbitrarily chosen series, even if of the same variety, would show any closer egreement in the points of comparison made in this table than is therein shown by the American and Egyptian squares. About July 25, 1904, a rather sensaticnal report was published in a number of prominent newspapers, claiming that a variety of tree cot- | ton had been found which was not only unaffected by frosts, but also_ immune to the attacks of the boll weevil. An agent of the boll weevil | investigating force, Dr. A. W. Morrill, was detailed to study the cot- ton which had given rise to the report. Careful investigations were made in seven different localities. No variety of cctton is positively known to be unaffected by frosts. It was found that but a few stalls of cotton were growing in any of the localities visited. The fruit was scattered, in many places there being no boils and the fiber of very poor quality. An examination of the squares showed that they were badly infested by the weevils in several of the localities visited, and | he isolated location in other cases might easily explain their escape | from attack. | HAS THE WHEVIL ANY CTHER FOOD PLANT THAN COTTON? The question of the possibility of boll weevils feeding upon some other plant than cotton is one of great importance. If is a well- known fact that insects which have few food plants usually confine their attacks to closely related plants belonging to the same botan- ical family, or even genus. Accordingly, most of the plants which have been tested especially are those most closely related to cotton. Four species of Hibiseus (Z7. esculentus, H. vesicarius, H. manthot, — Bul. 51, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE X. INSECTS OFTEN MISTAKEN FOR THE BOLL WEEVIL. Figs. 40, 41, Mexican cotton boll weevil (Anthonomus grandis), much enlarged; fig. 42, Lixus sp., enlarged three and one-half times (original); fig. 43, acorn weevil (Balaninus victoriensis) = a, Female, dorsal view; b, same, lateral view; c, head, snout, and antenna of male—all enlarged four times (from Chittenden); fig. 44, apple curculio (Anthonomus scutellaris) , enlarged (from. Insect Life); fig. 45, pepper weevil (Anthonomus xneotinctus), much enlarged (original); fig. 46, Desmoris scapalis, enlargeca (from Chittenden). Bul. 51, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE Xl. INSECTS OFTEN MISTAKEN FOR THE BOLL WEEVIL. Fig. 47, Transverse Baris (Baris transversa), much enlarged (original); fig. 48, Centrinus penicellus, enlarged (original); fig. 49, coffee-bean weevil (Aracerus fasciculatus): a, larva; b, beetle; ¢, pupa, enlarged (from Chittenden); figs. 50,51, Chalcodermus xneus, enlarged (from Chittenden). Bul. 51, Bureau of Entomology, U. S. Dept. of Agriculture. Gi U Wp ff a Z: H INSECTS OFTEN MISTAKEN FOR THE BOLL WEEVIL. Figs. 52, 53, Sharpshooter (Homalodisca triquetra), enlarged (from Insect Life): fig. 54, cotton stainer (Dysdercus suturellws’, enlarged (from Insect Life); fig. 55, cotton stalk borer (Ataxia crypta), enlarged (from Howard); fig. 56, imbricated snout-beetle (Epicxrrus imbricatus) enlarged (from Chittenden); fig. 57, snapping beetle (Monoc (from Chittenden). y repidius vespertinus), enlarged PLATE XII. « " pp dieley Bul. 51, Bureau of Entomology, U. S. Dept. of Agriculture. PLATE XIII. METHODS OF WEEVIL STUDY. Fig. 58, Device used in testing attractiveness of molasses to hibernated weevils early in spring, reduced to one-fourth natural diameter; fig. 59, weevil ‘‘ playing ’possum,”’ enlarged two diameters; fig. 60, weevil ‘ playing ’possum,”’ natural size; fig. 61, field cage used to confine weevils on uninfested plants; tagged plant after removal of cage at right (original). “e 65 IT, moscheutos) were grown and an effort made to see whether weevils: would feed upon either the leaves, buds, or seed pods. In no case, however, did they live on any of these for any considerable time,, though they fed slightly upon some of the parts. Hibernated weevils: starved in an average time of about 4 days with leaves of either okra or Sunset Hibiscus. The buds and seed pods were not formed at that. time, so could not be tested. Weevils of the first generation, which: had fed upon no cotton, were placed upon Sunset Hibiscus, and these: starved in an average of 3 or 4 days. First generation weevils, which had fed for a few days on squares, were placed upon leaves, buds, and seed pods of /7biscus vesicarius. Though they fed a little, all starved inanaverage of aboutddays. A lot of first-generation weevils, fed first for several days with squares, were given leaves, buds, and seed pods of _ okra. More feeding was done by this lot than by any other, all parts _ being slightly attacked. These weevils lived for an average of 7 days. _ Numerous other plants, including sunflower (//edianthus annuus), _ bindweed ( Convolvulus repens), the slender pigweed and the spiny pig- weed (Amaranthus hybridus and A. spinosus), and western ragweed (Ambrosia psilostachya), and various other species of weeds and _ grasses which occur more or less frequently around cotton fields were: _ tested, but in no case was feeding noticed except in the case of weevils: supplied with pieces of the stem of sorghum, the stems of which were _ cut into short lengths and some of the pieces split lengthwise. Upor the exposed, juicy pith weevils fed considerably, but they did not: puncture through the hard stem to obtain the juice. The sweet sap: found in the pith sustained weevils for some time in the laboratory, | but where obliged to puncture the stem, as they would be in the field, they would never attack sorghum, except possibly freshly cut stubble. Among the many plants tried, therefore, none has been found to show any capacity for sustaining the lives of weevils in the field in the absence of cotton. During the summer of 1904 a number of other plants not closely related to cotton were tried, but upon none of them would the weevils. _ even attempt to feed. The question of the original food plant of the weevil has received considerable attention from this Bureau, the investigations made in Cuba being particularly thorough and conclusive. In that island some: | varieties of cotton grow wild and are perennial. After most careful | search Mr. EK. A. Schwarz wrote in the spring of 1903: ‘* There is not. the slightest doubt, in my opinion, that the original and only food plants of the weevil are the varieties of Gossypium and here in Cuba _the variety known as kidney cotton.” The investigators of the _ Bureau of Entomology have given special attention to the possibility of the boll weevil breeding on other plants than cotton. Throughout. _ the investigations of Prof. C. H. T. Townsend in southern Texas and 16780—No. 51—05 3) 66 in Mexico and the careful studies made by Mr. Schwarz in Texas and in Cuba and the observations made by the writers in Texas every plant closely related to cotton has been most carefully watched, and the uniform failure to find the weevil upon any other plant makes it practically certain that cotton is its only food. INSECTS OFTEN MISTAKEN FOR THE BOLL WEEVIL. Many species of insects have been mistaken for the Mexican cotton boll weevil. Among them the two most commonly reported in Texas have been an acorn weevil (PI. X, fig. 48) and a species commonly found upon bloodweed or ragweed. The chief reason for the promi- nence of these two species is not that they resemble the boll weevil more closely than do others, but rather that their habits bring them into closer proximity with cotton fields and their abundance has led to their more frequent discovery. The acorn weevil has in a number of cases been taken in lantern traps set in cotton fields, and the mistake in the proper identification of the species has given currency to the report that the boll weevils are attracted to lights, which, however, is never the case. There is no authentic record of a single boll weevil having been caught at any light. Only very rarely and under excep- tiona! conditions will the acorn weevil feed at all upon cotton bolls. Though the bloodweed weevil (PL. X, fig. 42) has been taken from cotton plants, no evidence has been submitted showing that it was actually feeding thereon, and it is more likely that such specimens had merely strayed to the cotton from bloodweed growing near. Another species of weevil, Desmoris scapalis (Pl. X, fig. 46), is much less common and therefore less frequently mistaken, but resembles the boll weevil in general appearance far more closely than does either of the-species previously mentioned. This insect has been found attack- ing white prickly poppy (Avgemone alba) and tumbleweed (Amaranthus grecizans) in the spring, and probably breeds on Prionopsis ciliata Nutt. and the broad-leaved gum plant (Grindelia squarrosa). In general the food habits of any species are among its distinctive, specific characters, and as the structural differences are easily over- looked and difficult of appreciation by anyone unacquainted with the careful study of insects, a rather full though by no means complete list is here given of the species which have been reported to the Bureau of Entomology as having been confused with the boll weevil. A num- ber of the most common species will be found figured among the illustra- tions in Plates X, XI,and XII. The scientific names of the insects are given because they are definite and refer positively to a single species, whereas the common names are used so loosely that the same name may be applied to a number of species having possibly similar habits. In many cases no common name has yet been given to the species. Hight of the species mentioned attack living cotton and five species are found feeding only on decaying bolls. The occurrence of the remainder upon Deeg Wt eae ecteey / 67 cotton is merely incidental. The boll weevil is included in this list, and figures of the adult are given in the plates to facilitate comparison. Insects often mistaken for the boll weevil (Anthonomus grandis). Scientific name. Common name. Usual food plant. aeser Anthonomus grandis Boh ...-..--- Mexican eotton boll wee- | Cotton squares and bolls... X&, 40, 41 Anthonomus albopilosus Dietz....|.. marr BS Ee eA a ere Ee Sig dedi ea ay cee Sane el Res orttate als eons Anthonomus signatus Say ..--.--- Strawberry weevil..------ Various flower buds....2----|--22--- sec Anthonomus eneotinctus Champ .| Pepper weevil...---..---- Peppernpodde se ceesseeasccer X, 45 Anthonomus scuteliaris Lec ....--- Apple weeyil........-.--- iNSO) OEY Sees ae oom a saci meee XK, 44 Desmoris scapalis Lec...-...----- Jronweed weevil.....-.-- Broad-leaved gum plant.... X, 46 Desmoris constrictus Say ...------ Sunflower weevil........- SS ULTTIO WC Ne sis ee rere ieee cee Re eens eg ‘COMORRUG DATS ROD INBO5= tadansaod|lyshaca dss Gugdassannegésonass |pacuueacdsunseddios coo oped sonollacasauasaode (COMOPPOGIAMD GRGODS SEs oko5555|55 5055 3a4 5645 s5nSneosOGaeSess |S aad bs coe soer Eco see no soo peS sso bacnodsomane Conotrachelus nenuphar Hbst...-| Plum eureulio.........--- Plums aad PCACHeS cc. + cecil ee ee see ee CORUITACIE USI CUCODR als Mad. . |i asain soata cesses ca. -e CWameless ee Ger reise ete eel eee ae CONTE TIVUSHD CUVUCELLLLS SANDS sats ei ern paca See ee eee es cence BeetieimilOwers.. oe. XI, 48 ROE OALAIS PUCUIN US TANS sos sserclae oot ie nice inne eyelncinisinie isis sel[ > oer SO) ges ae oi aa eh mea Te Ee Chalcodermus «eneus Boh......--- Cowpea-pod weeyil....-.- Cowpea pods _.--.. 2... -- | XA, 50,51 Dorytomus mucidus Lec...--..--- AC wallow weevdlic nec