Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. . . » ay Py aes si a 0, 45. - e See nae BS ea RAE ee f y . HOWARD, ENTOMOLOGIST, £ Rae a MECN COTTON mL, WEN € Me A234 ‘ > ' ng « ry - 2 PREPARED UNDER THE DIRECTION OF THE ENTOMOLOGIST i ne aro a & . Me if : a Les Ly 2 BY Z = : 5 > g és es ; A . ee Wed. HUNTER and W. E. HINDS. eRe Ke a WASHINGTON: 8 oP 0 al US OVERNMENT PRINTING OFFICE. Choe tes 4 + : Load c Bene ey z =F G date Z re j ¥ . 1 j pe” ‘ 2 i ¢. , : oe : 1 : * £ 7 5 ¢ R mn NE a DIVISION | OF aes tp aL: O. Howarp, , Entomologist. oe a Cnt gcone. de. re, we A. Guacue C. ip Paves, F. i BIsHOPr, SPRINGER ( Gors, = ae °C. M. - WALKER, ees bes agents. — Bul. 45, Div. of Entomology, U. S. Dept. of Agriculture. PLATE |. DEVELOPMENTAL STAGES AND WORK OF THE BOLL WEEVIL. Fig. 1, Cotton boll weevil; fig. 2, weevil feigning death; fig. 3, two eggs and feeding excavation in a square; fig. 4, full-grown larva; fig. 5, pupa, ventral view; fig. 6, pupa, side view; figs. 7-9 show transformation taking place within squares: fig. 7, larva, full grown; fig. 8, pupa; fig. 9, adult; fig. 10, weevils feeding on boll; fig. 11, larva developing in boll, (Figs. 1-10, natural size; fig, 11, two-thirds natural size.—Original. ) teo PE RAR EEN OF AGRIGUELLURE, DIVISION OF ENTOMOLOGY—BULLETIN No. 40. L. O. HOWARD, ENTOMOLOGIST. THE MEXICAN COTTON BOLL WEEVIL PREPARED UNDER THE DIRECTION OF THE ENTOMOLOGIST BY W. D. HUNTER and W. E. HINDS. ) ————-f WN H =U fff NZS WASHINGTON : GOVERNMENT PRINTING OFFICE. 1904. LETTER OF TRANSMITTAL U. 8. DEPARTMENT OF AGRICULTURE, DIVISION OF ENTOMOLOGY, Washington, D. C., February 20, 1904. Str: I have the honor to transmit herewith for publication an account of the Mexican cotton boll weevil, prepared under my direc- tion by Messrs. W. D. Hunter and W. E. Hinds, special field agents of this Division. Mr. Hunter has been engaged for three years in investigations of this very important injurious insect, his work extend- ing all through the infested portions of Texas and to some extent into Mexico. Mr. Hinds for two years has been devoting his whole time to this subject, having been stationed for the most part at Victoria, Tex., in charge of laboratory work. The bulletin as a whole is a remarkably careful and complete treatment of the entomological aspects of the investigation. It seems to me as complete a treatise of the life history of a single species as has ever been published. The necessity for the most perfect knowledge of every detail of the habits of this great enemy to the cotton crop must be obvious, since only upon such perfect knowledge can we authoritatively base remedial work and can we authoritatively indicate the uselessness of many of the remedies proposed by ingenious and inventive persons. ‘The six- teen half-tone and other plates and six text figures are an essential part of the report. I recommend the publication of this paper as Bulletin No. 45 of this Division. Respectfully, LL. O. HOWARD, Entomologist. Hon. JAMES WILSON, : Secretary of Agriculture. | ; if EIR Tes PAG Toe The Mexican cotton boll weevil (Anthonomus grandis Boh.) has the unique record of developing in less than twenty years from a most obseure species to undoubtedly one of the most important economic- ally in the world. It was first brought to the attention of the Divi- sion 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 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 made elsewhere in the publications of the Division, are included to bring together in convenient form practically all that is known regard- 3 + 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. E. 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. In pre- senting this work the authors have taken care to state fully the data furnishing the basis for the various conelusions. Under each impor- tant heading will be found, first, a description of the methods and apparatus employed; second, a full and in many eases tabular state- ment of observations; third, the obvious conelusions. Care has con- stantly been exercised to avoid errors likely to result from artificial conditions in the laboratory. Cl Fig. 67.—Cotton stainer (Dysdercus suturellus) -_.--.-----. ---- Fig, 68:—Cotton stalk borer (Ataxia crypta)-___-..2.-.-.------ Fig. 69.—Imbricated snout-beetle (Epicceerus imbricatus) ____- Fig. 70.—A snapping beetle (Monocrepidius vespertinus) ----_- TEXT FIGURES. Map of area infested by weevil . Mexican boll weevil, head showing rostrum and antenne_________- . Diagram showing activity of 5 female weevils_.____.__._._______.- . Bracon mellitor enemy ou boll weevil, Pediculoides Ventricosus 2.2. 224. 4.222 2s SOMLCH OPSUSOCOULES Vials CCUG t= 2 6 oS Ee ge | THE MEXICAN COTTON BOLL WEEVIL. GENERAL CONSIDERATIONS. HISTORICAL. There is very little certainty regarding the history of the Mexican cotton boll weevil before it came to the attention of the Division of Entomology in Texas in 1894. The species was described by Boheman in 1845 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 (Heliothis armi- ger) or the cotton caterpillar (Aletia 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 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 Division of Entomology as an impor- tant enemy of cotton. Mr. C. H. T. Townsend was immediately sent 11 12 to the territory affected. His report was published in March, 1895. It dealt with the life history and habits of the insect, which were then 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 Division 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 Division of Entomology in regard to the advance made and the dam- age caused by the insect. In 1895 the insect was found by 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 principal cotton-producing region of the State caused the Division to continue its investigations during practically the whole season. The results of this work were incorporated in a 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 in regions where the rainfall is more certain. In 1900 as well as in 1905, in all or part of the region referred to, the numbers of the weevil were reduced by climatic conditions, principally a seanty rainfall, so that they were comparatively unimportant factors. During 13896 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 possible, 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, 13 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 Division 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 Division 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 Division 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 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 unsatisfactory. The need of ameans of testing the reeommendations of the Division 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 Vie- 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 pubiished 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 14 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 Cuernevaca, where a study was made of the methods of propa- gating parasites, especially Pediculoides ventricosus Newp. A large number of specimens of this mite was 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 Mareh $30,000 was placed at the disposal of the Division of Entomology. It thus became possible to increase 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 experi- mental work demonstrated many important points. The principal ones are detailed in Farmers’ Bulletin No. 189 of this Department. 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 coHec- 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 _ tall 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 —+ | 15 doubtful, although the first fears entertained in many localities that the cultivation of cotton would have to be abandoned have generally been given up. An especially unfavorable feature of the problem is in the fact that the weevil reached Texas at what would have been, from other considerations, the most critical time in the history of the production of the staple in the State. The natural fertility of the cotton lands had been so great that planters had neglected completely such matters as seed selection, varieties, fertilizers, and rotation, that must eventually receive consideration in any cotton-producing coun- try. In general, the only seed used was from the crop of the preced- ing year, unselected and of absolutely unknown variety, and the use of fertilizers had not been practiced at all. Although it is by no means true that the fertility of the soil had been exhausted, neverthe- less, on many of the older plantations in Texas the continuous plant- ing of cotton with a run-down condition of the seed combined to make a change necessary in order to continue the industry profitably. A eareful examination of the statistics, to which more 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 most 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 does not compare with that at the beginning. Upon the foregoing basis, during the season of 1903 the weevil caused Texas cotton planters a loss of about $15,000,000, and this estimate 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 amounted 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 portion of the cotton belt indicate that the weevil prob- lem 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 normal cotton crop of the United States represents a value of $500,000,000, the extreme ulti- mate damage 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 exaggerated, especially in newly invaded regions. It isnot at all necessary toabandon cotton. The workof the Division of Entomology for several seasons has demonstrated that a crop can be grown profitably in spite of the boll weevil, and this expe- 16 TERRITORY AFFECTED. At the present time the boll weevil has not been found in the United States outside of Texas (see fig. 1) except in three instances in Louisiana. In one of these cases, at the sugar experiment station at Audubon Park, in the vicinity of New Orleans, the cireumstances have led the State authorities to the conclusion that the pests were purposely placed in the fields. The other two cases are isolated oc- currences in Sabine Parish, in the extreme western part of the State. Both of these are apparently traceable to importation from the oppo- site county in Texas, in cotton seed used for planting purposes or possibly in hay. The authorities totally destroyed the cotton grow- ing at the experiment station at Audubon Park, La., as soon as the presence of the weevils was discovered. As no cotton is grown within 9 miles of that point, it seems altogether likely that the colony may have been completely exterminated. Similar action is being taken regarding the two colonies found in Sabine Parish. In Texas the infested area extends from Brownsville, where the weevil originally entered the State, to Sherman. Shelby and Morris counties represent the extreme eastern range. The cotton acreage involved in this territory includes about 30 per cent of the cotton acreage of the United States, which produced in 1900 about 35 per cent of the total crop of this country, or about one-fourth of the crop of the world for that year. There is, however, a considerable belt between about the latitude of Dallas and the Red River where the pest does not occur in uniform numbers in all cotton fields, and con- sequently the general damage has not been great. It may bea matter of only two or three years before it will become sufficiently numerous to cut down the total production. 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 eul- tivation of cotton was abandoned fora 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 liable to be infested when growing in the vicinity of kidney cotton. A large > ae OS IS STE na cuay owralcoguie of ~t | =} vl Z = 1 X Nn a | ae ij \) } Be ZAPATA. f iN \ ul \ yy, z Fic. 1.—Map showing area infested by Mexican cotton boll weevil (redrawn. ) 21739--No. 45—04——2 18 number of wild cotton trees growing in the vicinity of dwellings or growing cntirely wild are always infested, and here the weevils are more numerous, but never as numerous as on the cultivated Egyptian 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 -aising in Cuba. The presence of wild perennial cotton, upon which the weevil 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. 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 im- portant elements in limiting the spread of an insect—namely, win- ter temperatures 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 annu- ally a distance of about 50 miles. The insect is undoubtedly chang- ing 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. Exeept in afew 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 situa- tions throughout the belt the cotton fields are smaller and more iso- lated 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. 94), 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 ovt, 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 — 19 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 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. Eariy 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. 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 these 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 spread of 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 nothing 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 weevil may eventually be more widely distributed than any other. 20 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 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 completed. These immature 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. Jolor varies as widely as does size. It is usually of a gray or yeilow- 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. II, fig. 12. THE EGG. ‘The egg of the boll weevil is an unfamiliar object even 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 conspicuous on account of its pearly white color. Measurements show that it is on the average about 0.8 mm. long by 0.5 mm. wide. Its form is regularly elliptical (Pl. III, fig. 14), but both form and size vary somewhat. Some eggs 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 deli- cate membrane forming the outer covering of the egg shows no notice- able markings, but is quite tough and allows a considerable change inform. Were the eggs deposited externally they would doubtless prove attractive to some egg 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 weevil avoids by placing the eggs deeply within the tissue of the squares or bolls upon which she feeds. As a 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 incon- spicuous objects (Pl. I, fig. 3) and are found only after careful search. rh Pe sn) = Pet ee 21 EMBRYONIC DEVELOPMENT. Owing to the transparency of the egg membranes, something of the development of the embryo ean be seen through them, but no special study has yet been made upon the subject of the embryology of the weevil. The fully developed embryo completely fills the inte- rior of the egg, its large head being in one end and its body curved ventrally upon itself till nearly double. Considerable motion is mani- fested if the egg be touched at this period. LENGTH OF EGG STAGE. Concealed as the eggs are beneath several layers of vegetable tis- sue, 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. Careful dissections were then made of the squares at a little later than what was found to be the average embryonic period at that sea- son. 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 I, 553 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 can be approximately determined for any season and for any locality within the present area of infestation. TABLE I.—Length of egg stage at certain periods. Namber Mean eer age pense i ; 5 ,_ |tempera-/effective| length o Period of examination. OF obser [ture for |tempera- eg e “1 period. | ture.@ stage. 1902. Ori. Sie Days. Septembert=Octoberset =.= js2sso. ee es ee 385 81 88 | 2.5to 3 October November lias = sss ee a a 107 73 30 | 4 to 4.5 Noveniber?i—December 15> = 2-9 Ss) ee 36 62 19 11 1903. AVIS yaad ULN) Oo) ee een ee Ly Nee a es ee 25 1255 2 ii| noo vO. ARO baile e tea Hee Re oS SA oe eee Se eels Fb 5p al ee aera eee |e ets ee Ib3.4to 4.1 aIn considering the influence of temperature upon the weevils it has been assumed that. as has been found to be the case with other animals, 43° F. would be about the lowest temperature at which the weevils would beactive. Temperatures blow that point would have, therefore, no influence upon their activity, while all above that point would. For this reason it is better to speak of the ‘‘effective temperature,” meaning by that the number of degrees above 43° F. Experiments made upon the influence of temperature upon the activity of weevils indicate that this is very near the correct figure for this insect. b Weighted average. The extreme range observed in Table II in the length of this stage is from two to fifteen days, while the average period for the whole 22 number of observations is but three and six-tenths days. It is possi- ble that the embryo can undergo an even greater retardation without losing its vitality. It may be noted here that drying of the square will also retard - embryonic development, but this condition does not oceur in the field. TABLE II.—Range in length of egg stage. | Number Length of | Number _Length of of eggs. | egg stage. | of eggs. | egg stage, Days | | Days. P| | 4 5 to 6 182 | 2to3 || 3 8 to a \| 5 10 to 12 2to 4 || 15 | 10tol2 42 | 3to4 || 4 | 10tol3 96 4 || 3 18 to 14 8to5 || 2 13 to 15 40 | 4to5 || | 2) | 3 4t06 | | { — = — =e The length of the egg stage in bolls does not appear to differ greatly from that in squares. HATCHING. While still within the egg 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. HATCHING OF EGGS LAID EXTERNALLY. It occasionally happens that females are unable to force an egg into the puncture prepared to receive it and the egg is left on the outside of the square or boll. Eggs so placed usually shrivel and dry up in 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 two to three 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 externally is of no importance, since the larve must perish without doing any damage. EATING OF EGGS DEPOSITED OUTSIDE. The number of eggs left outside increases as the female becomes weakened, and is especially noticeable shortly before her death. The number of such eggs which may be found is greatly diminished by the following peculiar habit, which was observed many times. Occasion- ally it appeared that the puncture which the female had made for the reception of an egg was too narrow to receive it, and after a prolonged attempt to force it down the female would withdraw her ovipositor, a 23 leaving 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 some- whatthe cavity previously made. When this was completed she would attempt to place another egg therein. The second attempt was usu- ally 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 writers’ general impression that less than | 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. (,4; inch) in length. Except for the brown head and dark-brown mandibles, the young larva is 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 changed 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. Ill, fig. 15). 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 great changes from the legless grub to the fully formed and perfect beetle (PI. I, figs. 7, 8, and 9). Throughout this stage the.body of the larva preserves a ventrally curved crescentie form (PI. III, fig. 16). The color is white, modi- fied somewhat by the dark color of the body contents, which show through the thinner, almost transparent, portions of the body wall. The dorsum is strongly wrinkled or corrugated, while the venter is quite 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 larva are slightly changed. The dark color disappears from the interior and is replaced by a creamy tint from the transforming tissues within. The ventral area becomes flattened, and the general eurve 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. 3 24 GROWTH. It is impossible to follow the growth of an individual larva with- out interfering so greatly with its normal conditions of life as to make the observations unreliable. It seemed more accurate to meas- ure larvee of approximately known ages. In these measurements the natural curve of the body was not interfered with, but the measure- ment taken across. the tips of the body. In this way it was found that in squares during the hot weather the length of the body increases quite regularly by about 1 mm. a day. As it 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 larvée vary in length from 5 to 10 mm. across the tips of the curve. Larvee of normal size in squares average from 6to7mm. The largest larve are developed in bolls which grow to maturity (PI. III, fig. 19). 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 right time to observe the process are very small indeed. However, it has been ascertained beyond question that two molts occur before the larva reaches half its growth. The first oceurs 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 ocea- sionally found larve which had certainly just molted, but which were much larger than the usual size at the second molt, the writer is led to suspect 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 as 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 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. PLATE Il. Sgua ne, bur ws Yer tare Sey) fate ey foi f é pa? : t tw iy Puncke ae a Ss a ec ee EMR I Bul. 45, Div. of Entomology, U. S. Dept. of Agricuiture. FIG. 12.—COLLECTION SHOWING LIFE HISTORY AND WoRK OF BOLL WEEVIL. (ORIGINAL.) fie 5 1 f a “ ¢ Oh 4 ui t Bul. 45, Div. of Entomology, U. S. Dept. ef Agriculture. PLATE III. DEVELOPMENTAL STAGES AND WORK OF THE BOLL WEEVIL. Fig. 13, Two boll weevils feeding on a square, natural size; fig. 14, egg isolated, 25 times natural size; fig. 15, full-grown larva in square, natural size; fig. 16, full-grown larva isolated, natural size; fig. 17, pupa, twice natural size; fig. 18, adult just transformed, natural size; fig. 19, large laryee in large boll, two-thirds natural size; fig. 20, pupal cellin boll, broken open, twice natural size. (Original.) 25 LENGTH OF LARVAL STAGE. Most of the observations upon the larval stage were made between September 1 and December 15, 1902. ‘The temperature prevailing dur- ing the first half of September was as high as is ordinarily experienced 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 two of the immature anthers. The coverings were then replaced as carefully as possible. Another disturbance was necessary to determine exactly the date of pupa- tion. Observations made in this way were checked by others using larve which were allowed to go from egg deposition to pupation under natural 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 length of the immature period in cases where no disturbance of normal conditions occurred, we may conclude that the periods found for the larval stage were approximately correct. Altogether 266 observations were recorded upon the length of this stage. The majority of the observations may be included in three groups, and when thus grouped they may be best considered in relation to the effective temperature. Table III presents a brief summary of these groups: TABLE III.—General results as to length of larval stage in squares. Mean (Average average effective Number | Average Period of examination. |of obser- | range of renee pope vations. | stage. 1902. SHE HE Days. September 6 to October 5 ____________- Shoah Nptee Leena ieen aeean 78.7 35.7 195 6to 9 DEpLbembereowOs| effective | effective Period of examination. Ce of pupal pone ‘tempera- tempera- “| stage. SH) TRUE | ture. sell 1902. | Days. Days. | OH. CAKE Wihy 6 GOB E See eee es carci ere ee ee ae el 161 | 2to 5 3.5 | 39. 65 | 138.8 September 15 to October 8 -_-.-._-._---_.--._---.- S15 Snton a 5.2 36. 05 187.5 SepLomiberm.4 to-OctOberizs= =~ =a a 167 | 4to 8 6.0 31.1 186.1 INE VCO NS 2 CT Bie a aes ee 29| 5to 6 5.6 2652 5146.7 [DYE CESAR YET AA Oy CAS De re ee a a eR a omen 4 10 to 16 14.5 18.55 | 269.0 It should be noted in connection with Table IV that the observa- tions made in November were 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 length of this period during hot weather is from three to four days, and the period increases as the cool fall weather approaches to a maximum of about fifteen days. A comparison of Tables I, III, and IV shows that the decrease in temperature affects each stage in very nearly the same proportion. In each case the maximum recorded length of any stage is about four times its minimum, and the great retardation in each case occurs somewhere between 60° and 70° F. of mean average temperature, or 17° to 27° F. of effective temperature. Even greater retardation occurs during the winter season. 28 The length 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. EFFECT OF BURYING SQUARES UPON PUPATION AND THE ESCAPE OF ADULTS. The experiments made upon this point were designed to ascertain the value, if any, in the plowing under of squares as a means of destroying the larve and pupe infesting them. but few experiments seemed necessary to demonstrate the futility of this operation alone as a means of controlling the weevil. Squares which were known to be infested with about haltierown larvee were placed in glass jars and covered with several inches of quite dry and fairly well pulverized earth. When examination was made it was found that pupation had taken place normally while the squares were buried under from 2 to 5 inches of dirt. In no ease was pupation prevented, though a few weevils did not leave the squares after having become adult. Altogether about 100 squares ' were thus buried, and from them over 75 weevils emerged. In a portion of the preceding tests careful examination was made to ascertain how far toward the surface the newly emerged weevils had succeeded in getting before they perished. It should be noted that these weevils had never fed, and they would have, therefore, less strength and endurance than such fully hardened adults as might be buried in the ordinary processes of field cultivation. Furthermore, the soil used was of finer texture and more compactly settled than it would be in the field. Twenty-seven weevils were found in this exam- ination, their location varying from the bottom of the jar to their having escaped through 4 inches of soil. A weighted average shows, however, that each weevil had made its way upward through 2 inches of dirt. Wemay infer, therefore, that had these squares been buried under less than 2 inches of fairly well pulverized earth, as would be the case from field cultivation, but a small percentage of them would have failed to make their way out. As it was, fully three-fourths of those leaving the squares made their way out through more than 2 inches of dirt. In 1896 Mr. C. L. Marlatt noted that ‘‘the weevils can escape from loose soil when buried to a depth of 3 inches, but when artificially embedded 8 inches in moist soil they are unable to extricate them- selves, as shown by test experiment.” Quite extensive experiments are now being made at Victoria to test the ability of the fully fed adult weevils to escape after being buried at various depths and in soil containing various pereentages of water. That the moisture content exerts a great influence upon the texture of the soil is especially noticeable in the black bottom lands of the Texas cotton belt. While 29 the results of these experiments may furnish reasons for changing our conclusions upon this point, the present indication is that the bene- ficial effect of thorough cultivation lies in the direct influence which that practice exerts upon the steady and rapid growth of the cotton, thus favoring the production of squares, the setting of bolls, and the early maturity of the crop rather than in the direct destruction of the weevils by burying them either while in the squares or after they have become adult. THE ADULT. BEFORE EMERGENCE. Immediately after its transformation from the pupa the adult is very light in color and comparatively soft and heloless. The probos- cis is darkest in color, being of a yellowish brown; the pronotum, tibize, and tips of the elytra come next in depth of coloring. The ely- tra 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. 18), 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. IV, fig. 21). In large bolls the escape of the weevil is greatly facilitated by the natural opening of the boll (PL IV, fig. 22). 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 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. IV, fig. 26). The material removed does not appear to be eaten, but is rather 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 30 darkening of the ground color makes the scales more apparent, and thus gives the impression of further development after emergence has | taken place. ; | 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 cf 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 4 inch). in length, including the proboscis extended, and from | to 3 mm. (4% to ¢ 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. | I The supply of food was not only small, but, owing to the immaturity ill of the pollen saes, its quality was also 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. l In them the food supply is most abundant, and the period of larval Hl development is several times as long as it is in squares. Possibly il 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 ii coming from the proper source. After emergence they were fed for iM some time to bring them up to their normal weight. in| TABLE V.—Summary of weight of weevils. tit! a Beth ee 4 Average | Source of weevils. Number. weight. Mi = = ———— At Grain. IB Bredstromyplckedssmiallll Sci uleur es pegs eee mse eee ea nee 25 0. 105 Hy Bredeeronmiaviera sc tall emy Sollee Sees sey ap ae rp ney 68 "281 iI BLA EPOMMAT SSO OLS ee ea ae BON Ura an tern 69 . 268 it Mo baila bec eh OF Ae ARE tae) WS SEIN a capes tI MN Ms ead EO ae 162 | 36. 825 1 Average weight per weevil, all sources .__..-..-......__-.--..__-__-_.----|_------.--- . 227 || It should be noted that these figures do not nearly represent the i weight of the extremes in size, but they do indicate the difference in i|| the average weevil of each class. 31 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 eolor. Weevils developing in large bolls, having an abundant food supply 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 seales. The seales are yellow in color, while the ground eolor 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- dueed from larve having abundant food and a long period of devel- opment the seales 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 non-essential 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 distince- tion 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 ideaisa 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 develop- ment and are not indications of sex. The sexes seem to be about equally represented among the smallest as well as the largest weevils. 32 Characters commonly used to separate the sexes in the family Cur- culionide are not distinctive in this species. As a rule the antennz are inserted nearer the tip of the snout in the male than in the female. This character is variable among boll weevils; and though a large 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 activity 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 charac- ters are there found. . PROPORTIONS OF THE SEXES. No reliable secondary sexual characters having as yet been discoy- ered, the certain determination of sex therefore rests solely upon the 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 VI. TaBLE VI.—Proportions of the sexes. Tfe- of males | i Season-of 1902, both bred and from field... =) = eee 240 | 260 Bibernated ‘weevils, 1902-3: 2. 23 Se ee ee eee 269 | 174 Hirst ceneration, (QQ 2. =. 8 eh ae eee eee 5 32 Bred weevils, 1908 -_-__------.-- bin i et A ne ee ee ee ee ee 45 3 Hield weevils, midsummer, 1908: 2) = es eS ee ee 52 59 'Potali< == 2-=—__.2 2.22. ee ee ee 649 5a8 From these 1,207 determinations it appears that males are somewhat more numerous than females, the percentage being nearly 54 of males to 46 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 may be that the retardation of development due to approaching Bul. 45, Div. of Entomology, U. S: Dept. of Agriculture. PLATE IV. BREEDING JAR AND METHOD OF ESCAPE OF ADULTS FROM SQUARES AND BOLLS. Fig. 21, Emergence hole made by weevil in square, natural size; fig. 22, weevil escaping nor- mally from boll, two-thirds natural size; fig. 23, apparatus used in breeding weevils, one-fourth natural size; fig. 24, larva destroying the ovary and preventing the bloom in large squares, natural size; fig. 25, leaf fed upon by weevils in confinement, one-half natural size; fig. 26, emergence hole of weevil from boll which never opened, two-thirds natural size. (Original.) RP LE MORO VIE Ce REL ER Roe TOR TER A eRe CRS Om Bul. 45, Div. of Entomology, U. S. Dept. of Agriculture. PEATE V- FIG. 27.—LARVA IN SQUARE, OVARY UNTOUCHED, NATURAL SIZE. (ORIGINAL). e Fic. 28.—LARGE AND SMALL LARVZ IN BOLL, TWO-THIRDS NATURAL SIZE. (ORIGINAL.) = a ee 33 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 liv- ing through the winter were also males. 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. LENGTH 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 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 cov- ered at the top by cheese cloth held firmly in place by a rubber band. With this apparatus weevils could be readily observed without dis- turbing 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 (Pl. IV, fig. 23). The moisture of the soil and fresh leaf covers were renewed as needed. Clean squares were sup- plied 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 length of their lives is known. Length 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 con- servative. 21739—No. 4oa—04——3 4 TasBLE VII.—Length of life of weevils upon squares. | Males. Females. , |Average , | Avera B Number. days. Number. ayes Weevils placed in hibernation Dec. 15, 1902; living Apr. 15, A OOS ooo ens Se re eae er ee eee 23 180 14 171 Hibernated weevils taken spring, 1903; estimated adult PSCH MT HUGO 2 Ee set Pa Se oS cs eae ae ae ered ere 66 223 53 220 Hibernated weevils, from time of feeding in 1903_______-_- af or First generation, bred __-.-.----- 9a ta Se ee Eee See 30 58 25 56 Mhind¥es. en erat OT lo TS Cl eee ee ee eee eee ee 18 43 10 54 IMME thy sem era tl OM seo 1; eC Clea pee 9 76 9 54 Totals and weighted averages, including hibernation POT OC 2 Sas ee eee OSM A gy my Nee ee he ea 146 2 = 13k 111 148 Totals and weighted averages, not including hibernation PGT LOO ae os See a Sr ee ee el aoe eee eee es ea | 147 7 112 64 Entire length of life, hibernated weevils only --_---_--.___- , 89 212 67 210 fs | 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. Probably the greater activity of the first generation may account for their somewhat shorter life. The average active life period for all generations is probably not far from 71 days for males and 64 days for females. LENGTH 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. I, fig. 10), 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 length of life of 19.7 days, while the females survived for only 15.2 days. This is a much shorter period than the normal length of life upon squares for either sex. LENGTH OF LIFE ON COTTON LEAVES ALONE. To determine whether they could live upon the foliage of cotton alone 69 newly transformed weevils were at the Ist 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 to squares and 6 continued upon the leaves. Of these 6, 3 lived to be 81 days old and were then intentionally killed for dissection. The ee. gt ee ee eee eee. 2 en 35 average length of life of those kept entirely upon leaves was over 30 days. These results show clearly the ability of many of the weevils to live upon foliage alone in fields in which fall grazing is practiced until it becomes sufficiently cold for them to go into winter quarters (see Pl. IV, fig. 25). LENGTH 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 anda half at atime. 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 length 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 54 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 lie: Six weevils just emerged kept upon undiluted molasses showed a greater length of life, these dying at an average age of 115 days. LENGTH 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. Each 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 53 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 increase the length of life of the starving weevils. LENGTH OF LIFE WITHOUT FOOD OR WATER. Three series of observations were made along this line. In the first the weevils used were taken immediately after emergence and never allowed to feed. Fifty weevils were tested in this way during July and August and showed an average length of life of 5 days from the date of emergence. A few lived as long as 8 or 9 days. ‘These never acquired as dark a color nor as great a degree of hardness as is normal. In the second series the 15 weevils used were 7 weeks old and full- fed at the time of beginning the test. These showed an average length of life of slightly over 6 days, the range being from 5 to9 days, These ' weevils were tested during the latter half of November, and the late- 36 ness 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 inthe middle of November. The con- ditions in this series were as in the series preceding, with the excep- tion that an abundance of two species of grass taken from cotton fields was included. These weevils showed an average length of life of nearly 73 days, ranging from 3 to 10 days. The weevils made no effort to feed 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 ina 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 clear- est 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. HABITS. Among the habits of any insect of economic importance, the first for careful study are those relating to its food, and secondly 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 37 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. FOOD HABITS. 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 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 accommodation of its rapidly iIMncreasineouike (alts fic. Pl Ii fie, Lo; PI PV, tie. 24). “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 by the larva is sufficient to arrest its development. In many cases of this kind the larva works its way up into the corolla and falls with it, leaving the young boll quite untouched (PI. V, 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 falls, and in such cases the boll falls as would a square. In large bolls the larvee feed principally upon seed and to some extent upon immature fiber. A larva will usually destroy but one lock in a boll, though two are sometimes injured (Pl. V, fig. 28). ADULT. Before escaping from the square the adult empties its alimentary canal 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 soon after 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 purpose in life: They will take squares, bolls, or leaves, but they much prefer the squares, and when squares are present in the field it is probable that leaves are seldom touched. As has been shown, however, weevils ean live for a long time upon leaves alone when squares and bolls are 38. 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 asocket 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 they have 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, head showing ros- the entire puncture becomes finally like that trum with antenne near middle and mandibles Of a miniature flask. at end—much enlarged Only after weevils have fed considerably do (original). ; : ; $ : sexual differences in feeding habits begin to appear (PI. ITI, fig. 13), the females puncturing 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 (PI. I, fig. 3); 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. As a number of these large cavities are often formed in one square (Pl. VI, fig. 29), 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 and its nor- mal course of development is continued. When feeding punctures are made in squares which are nearly ready to bloom, the injury com- . Masses. 39 monly produees a distorted bloom (PI. VI, fig. 30) and in very severe © eases 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 sep- arately. 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 weevil-days.“ During this period 2,185 squares were supplied them and they made 5,617 feeding punctures in 1,582 ofthesesquares. A little calculation shows that they averaged to make 33 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 compara- tively slight. 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 punetures per male per day, making the number of squares attacked by each male less than | 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 if accumulates often in quite large a 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 «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. 40) keeps their punctures scattered so long as plenty of clean squares can be found. When clean squares become searce, the normal inclination ean 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 was 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. TABLE VIII.—Number of punctures per weevil per day. Total. Average. haracterization of .| Number Feeding| Egg c gee ae of fe- lweeyil| Feeding| Egg punc- punc- Period of ‘| males. Bars punc- punec- |tures per|tures per) observa- YS: | tures. tures. weevil | female tion. day. day. Hibernated weevils Days. in laboratory-_------ 55 54) 4,938 17, 406 5, 702 3.5+ 2.3+ 45.3+ Hibernated females invite] decals emeee = as ane eee 4 93 284 489 3.0+ 5.3— 23. 3— Weevils of first gen- eration in labora- ; tOBYi 2 eee 31 27 | 38,258 16, 487 3, 565 5.0+ 2.4— 56. 2— Females, first gener- ation, in field cage__|___.------ 5 70 263 435 3.8— 6.2+ 14.0 Males only, labora- tory, summer of 1903 eae s eee eas Gewese eas 2,492 BCG Ee Bas paish 2:30 | steak nae 38.3-+4 Motaliseve 288s Sol 5 90 | 10,851 40, 057 10; W928. oso) Sees | eee 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 to 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 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. Whether they be few or many, however, makes no difference in the feeding habits of the hibernated beetles. The stage of the cotton determines largely the nature of the food habits at this time. Owing — SS ea ee Fs pi ly i aa a a a 4] to the extremely wet winter and the very late spring of 1903, little eotton could be planted until the latter part of March or the first part of April. In such a season as this, therefore, cotton must be small at the time of the emergence of the weevils from hibernation, and some time must elapse before the formation of the first squares fur- nishes the weevils with their normal food supply. During this inter- val the weevil gets most of its food from the tender, rapidly growing terminal portion 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 squares are developed, after which they confine their injury to them. The earliest plants in a field seem to attract most of the weevils, and where seppa” plants occur they serve as excellent 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 seem to start earlier and grow more vigorously than do those from seed and are therefore doubly tempting to the hungry weevils. 3 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.” 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 upon the young planted cotton hay- ing from 4 to 8 leaves. If, however, the cotton should be further advanced at the time the weevils appear, they would then go at once to the squares. Even then they prefer to attack the most advanced plants, which have a number of nearly grown squares, rather than the smaller plants which are but just beginning to square. Seppa plants, where such exist, come in, therefore, for a large part of the first attack of the hibernated weevils. This fact is well shown by observations made by Mr. A. N. Caudell, of the Division of Entomology, at Victoria, at about the middle of June, 1902. In an examination of 100 seppa plants growing in a planted field he found that fully half of the squares upon those plants were then infested. The planted cotton was just beginning to form squares, and was but slightly injured at that time. 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 a-*Seppa’’ is the term used by the Mexican residents of South Texas to differ- entiate the cotton plants springing from the roots of the previous year from those strictly ‘‘ volunteer,’ springing from accidentally scattered seeds. —— 7 See Sa Slee SS ee a Sn CTR Ce SSS SS EE EES eee eee 42 exclusively in the most recently unfolded growing portions at the tips of the stems, it was evident that the rapidity of increase in the leaf 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 [X.—Estimated increase in leaf area of cotton, averages of five plants. Primary leaves. Secondary leaves. : : | Average Percent-| Average 7 Percent- Date of examination. Tie st Vere? age of | number fever age age o per lant daily in- ea ee daily in- plant Pp * | crease. | plant. Pp crease. 1902. | | Series I: | Sq. in. | Sq. in. Aupust:30 ooo eass noes ueeeeeeee 8.0 G45 04 sae eee | O05) Se eee Septemberi3= 22 ee 8.6 136.8 8.0 8.0 AV? | ble eeanee Septemiber2ot= sass ee eee 9.8 231.6 5.4 16.6 187. 4 30.0 OCtOber 652) en ae eee i ae ara 11.0 309. 6 3.0 22.6 | 347.8 7.8 October Wis ses Se eee sae ye eae 13. 2 376. 6 2.0 31.0 | 522. 4 | 4.6 Series IT: | TANI SUS Gi SO) ek cara seer ee eae een 7.8 Urol see eae 21.6 266: 851235 Ss September 13 2282 i-k se see Soe 8.4 229. 2 2.0 24.8 | 341.4 2.0 Septemiber(2oy ssc eee 9.8 241.6 04 42.4 514.0 3.6 October Gs sass s) ae Peele ee em 9.6 214.8 | a—1.0 52.6 619. 2 | 1.8 Octoberdic.3 23 sees eee ee 10.0 ZIGSS eee sae 67.4 808. 8 2.1 a Decrease of 1 per cent due to falling of old primary leaves. 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 inerease 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 II. The extreme 43 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 absolutely impossible to poison the weevil’s food sup- ply, and also that the irregular emergence of the weevils from hiber- nation may extend through several weeks, it at once becomes evident that spraying early cotton for hibernated weevils is almost as imprac- ticable as the spraying 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. Males usually make the largest punctures, and always leave them open while they remain for a day or more working upon the same square. It has been often found that squares thus injured by a male will flare before the weevil leaves it. The time of flaring depends upon the degree of injury 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 showing any noticeable flaring. Fre- quently a square which has flared widely will be found later to have closed again and to have formed a distorted bloom (Pl. VI, fig. 30; PI. VII, fig. 31), and occasionally such squares develop 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. Bolls are quite largely fed upon after infestation has reached its height. Small and tender bolls are often thoroughly riddled by the numerous punctures (Pl. VII, fig. 32). Small bolls so severely injured fall within a short time. Larger bolls may receive more punctures without being so severely injured. A comparison of the external and internal effects in such cases is shown in Pl. VIII, figs. 34, 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. VII, fig. 33; Pl. X, fig. 38). After the bolls become about half grown the effects of feeding are less liable to cause the boll to fall (Pl. I, fig. 10). The puncture becomes closed by a free exudation of the sap and a subsequent woody growth, +4 which forms frequently an excrescence the size of half a pea upon the inner side of the ecarpel. An exerescence of this character usually results from an egg puncture, and often from feeding punctures. DESTRUCTIVE POWER BY FEEDING. A glance at the figures in Table VIII (p. 40) is sufficient 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 comparison of the figures for males alone with those for females alone or with those for males and females together shows that it is very conservative to say that males make less than half as many punctures as do females. By the habit of distributing their punctures among a greater number of squares the destructiveness of the females becomes at least five times as great as that of the males. This great capacity for destruction has been one of the most evident points in the history of the spread of the weevil, and deeply impressed the entomologists who first studied the insect in Texas. In 1895 Mr. E. A. Schwarz, in writing of the work of the weevil at Beeville, said: Each individual specimen possesses an enormous destructive power and is able to destroy hundreds of squares, most of them by simply sticking its beak into them for feeding purposes. SUSCEPTIBILITY OF VARIOUS COTTONS. An excellent 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, 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 eot- ton with equal opportunities to make their choice of food, and accord- i 45 ingly their location has been considered as indicating such choice. The period of observation extends from June to November, except with the Cuban cotton, which was planted late and began to square during the latter part of August. For the purpose of this comparison, both the varieties and the several 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 elass of cotton. The elements of numbers of plants and times of observation may be expressed by the product of those two factors forming a term which we may call ‘‘plant-days.” The total number of weevils found upon any class of cotton divided by the number of ‘‘plant-days” will give the average number of weevils attracted by each plant for each day, and these numbers furnish a means of direct comparison and show at a glance the average relative attractiveness of each class of cotton. The following table presents these results in comparable form: TABLE X.—Relative attractiveness of various cottons. Total. Average. Number | Relative | -,. | Infested Class of cotton. of | : | Weevils ; attract- plants eek | Weowlls ne eo per plant See iveness. | | per day- weevil. | | | 4 Nimerical: a= ase! = ean 62 4,920 | 287 3,507 | 0.058+ | 12.24 1.0 Cuhs nts ieee ee | 5 | 120 11 | iH 3)| an oa ae Seawlslain dhs seers ee 8 | 5d2 | 64 1,089 IG =) EOF 2.0 1B sy Gia ee ee 8 | 808 | 207 2,013 | .256+ | O70 | ge £4 Total of 3 non-Amer- | | | | | | 1GanlicOLtOnse==— = 21 | 1,480 | 282 3, 238 .191— 11.5— | 3.3— 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 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. a The practical applization of these observations may be emphasized 46 still further by the statement that in spite of the frequent and care- ful 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 Egyptian cotton under field conditions in three localities in Texas, no weevils being removed from either kind. At Victoria, Tex., on August 26, 1903, an examination showed that 96 per cent of Egyptian squares were infested, while an average of 13 fields of American showed 75.5 per cent. At Calvert, Tex., on Sep- tember 4, Egyptian showed 100 per cent infested, while the American varieties growing alongside showed 91 per cent. Similar results were found at San Antonio. Though growing in close proximity, the Egyp- tian produced no staple whatever, while the American gave better than an average yield in spite of the depredations of the weevil. In accordance with these observations, it appears that in developing a variety of cotton which shall be less susceptible to weevil attack by far the most promising field for work lies among the American varie- ties, and of these the very early maturing kinds are most promising. The question of choice of different varieties for food was tested in. the laboratory by Dr. A. W. Morrill, by placing squares of two kinds of cotton, American and Egyptian, in alternate rows in a breeding cage (Pl. XII, fig. 48), so lettered and numbered that each square could be exactly located. Weevils were then placed so that they could take their choice of these squares, and observations from 8 a. m. to 6 p- m. were made upon the location and activity of the weevils. Though this 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 XI presents a summary of these results. TaBLE XI.—Breeding-cage observations upon weevil choice of American and Egyptian squares. | a7 J ; 7 “ Num. American squares. Egyptian squares. Ex- | Period o er oO a | | peri-| observa- | obser- Weovils | Total aL Bec: | Egg | Total| 7, ee Egg ment.) tion. va- } : num- | gosted >| punc- | num- f punc- : | .| pune = Z ested.| punc- tions. | ber. tures, | tures. ber. tures. | tures 1 | 12m. to8 [Seaeemene 8 10 16 12 15 5 16 5 12 3 2 | 11.45a.m to 9.45 Pe Wades ae 5 10 16 5 19 1 16 5 13 3 3 |12m.tod p.m.day after _- 10 16 us 25 2 16 9 27 2 4) 11.45a.m to9a.m 5 10 16 6 17 6 16 8 14 3 5 | 6p. m. to | 8a.m 1 18 | 4 2 7 0 4 2 10 0 RepEsoad | 29 76 11 47 In experiments 1 and 2 the American squares were attacked more extensively than were the Egyptian, while in experiments 3 and 5 greater injury was done to the Egyptian. Inexperiment 4the 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 agreement in the points of comparison made in this table than is therein shown by the American and Egyptian squares. HAS THE WEEVIL ANY OTHER FOOD PLANT THAN COTTON? The question of the possibility of boll weevils feeding upon some other plant than cotton is one of great importance. It is a well- known fact that insects which have few food plants usually confine their attacks to closely related plants belonging to the same botanical family, or even genus. Accordingly, most of the plants which have been tested especially are most closely related to cotton. Four species of Hibiscus (H. esculentus, H. vesicarius, H. manihot, H. 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 Hibiseus. The buds and seed pods were not formed at that time, so could not be tested. Weevils of the first generation, which had had no cotton for food, 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 Hibiscus vesicarius. Though they fed a little, all starved in an average of about 5 days. 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 (Helianthus annuus), bindweed (Convolvulus repens), the slender pigweed and the spiny pigweed (Amaranthus hybridus and A. spinosus), and western rag- weed (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. Upon the exposed, juicy pith weevils fed considerably, but they did not puncture through the hard stem to obtain the juice. The sweet 48 | sap found in the pith sustained weevils for some time in the labora- | tory, but where obliged to puncture the stem, as they would be in the field, they would never attack sorghum, except possibly freshly eut i stubble. Among the many plants tried, therefore, none has been ij found to show any capacity for sustaining the lives of weevils in the field in the absence of cotton. ee es Se sas Ss , | 1 : ] | } } | The question of the original food plant of the weevil has received Mi considerable attention from this Division, the investigations made in | Cuba being particularly thoroughand conelusive. In that island some varieties of cotton grow wild and are perennial. After most careful search Mr. E. A. Schwarz wrote in the spring of 1903: ‘‘ There is not | the slightest doubt, in my opinion, that the original and only food Hi plants of the weevil are the varieties of Gossypium and here in Cuba | the variety known as kidney cotton.” The investigations of the Division 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 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 (Pl. XIV, fig. 55) 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 abundanee has led to their more frequent discovery. The acorn weevil has in a number of eases 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- | tional conditions will the acorn weevil feed at all upon cotton bolls. : Though the bloodweed weevil (Pl. XIV, fig. 54) 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. XIV, fig. 58), is much less common and therefore less frequently mistaken, but resem- bles the boll weevil in general appearance far more closely than does I | Div: of Entomology, U. S. Dept. of Agriculture. FIG. 29.—SQUARES MUCH FED UPON. NATURAL SIZE. (ORIGINAL.) Fig. 30.—DISTORTED BLOOM, CAUSED BY FEEDING UPON LARGE SQUARE, NATURAL SIZE. (ORIGINAL. ) Bul. 45, Div. of Entomology, U. S. Dept. of Agriculture. PRARE Vil: FEEDING INJURIES ON BLOOMS AND BOLLS. Fig. 31, Blooms distorted by feeding punctures, open but imperfect, two-thirds natural size; fig. 32, small boll riddled by feeding punctures, natural size; fig. 33, one lock of boll destroyed by feeding punctures, two-thirds natural size. (Original. ) 49 either of the species previously mentioned. This insect has been found attacking white prickly poppy (Argemone alba) and tumble- weed (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 Division of Entomology as having been confused with the boll weevil.¢ Many of the most common species will be found figured among the illustrations. 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. The boll weevil is included in this list, and figures of the adult are given in the plates to facilitate comparison. In many cases ho common name has yet been given to the species. Seven of the species mentioned attack living cotton and five species are found feeding only in decaying bolls. The occurrence of the remainder upon cotton is merely incidental. Insects often mistaken for the boll weevil. Scientific name. | Common name. Usual food plant. ae WEEVILS. | Anthonomus grandis Boh __--- | Mexican cotton bollweevil| Cotton squares and bolls_| XIV, 52,53. PAN MONOMUS CLO DTLOSUSDICUZe| Ses = a8 ee ee | Pe SSeS ee ae eet [eee ee Authonomus prunicida ______- Plums Ous er eee [SE Tarn soe eee ls ea | XIV, 57. Balaninus uniformis auct __-.| Acorn weevil_-_---.=_____-- NOAICO DHS ers ee San er lPX@Vin 55: Centrinus penicellus Hbst __--- | paseoneiss She Sonsne esas a oSaee | Beetle in flowers ______--- | XV, 61. Centrinus picumnus Hbst ____- | esd PS ee Ne ai ae SU a ea eee CO ie Ree ee ek arse! | eee a peelie Swe Chalcodermus ceneus Boh _---- | Cowpea-pod weevil ___....| Cowpea pods -________-_-- i XV, 63, 64. DESINIGTESISCULDOLUS We Cee at anne era eS Pa Broad-leaved gum plant _ XTV, 48. DESITGEISZCONSLERICLULGI SAV ene oe |e oe oe [pseoe ates heaes Saneao cbse stac| boosts eans Dorytomus mucidus Lec__-_---- | eee ale orcs SA pele ies kaa ail OW See Se Sa ee | eee ee ee Lixus leesicollis Lee ____---__-- | Blood-weed weevil ________ Ragweed (Ambrosia spp)- XTV, 54. Coccotorus scutellaris _____---- | Appleicurculig 2222562. YN 0) 0) Spe tae see eer ae XIV, 56. IBONIS:SULOLG) SAYrss=--- = -— === = | Striped ’Barisss-- 222 =-2=-- Stemsiof nagweedes=25 == |p se ae Baris transversa Say -_--------- | Transverse Baris_________- Roots of cocklebur -___-..-| XV, 59, 60. Anthribus cornutus Say------- | Horned stem borer_---_-_-_- Cottonystems eee ses os eee Arecerus fasciculatus DeG __.| Coffee-bean weevil _______- Coffee beans and old cot- | XV, 62. ton bolls. Epicerus imbricatus Say ------ Imbricated snout beetle __| Ommivorous _____--------- XVI, 69. SPPIDISODIS FOU TBM VSS eek, a OS Te ae NN | ge ee (Ae ee Rhynchites mexicanus Gyll __.| Mexican rose beetle-_-_-_---- iBeetlestattacke noses a=5 | aaa =e Hi CILIRESESOT. GLO USHUCC aes ake sae eee eee as OS ee ee Common in cotton fields__|__---------- Oph StCSID TE MOET OSUSIS NID 2 =| = s8s eso ee oe Houndsonvcottonee see] ose |= ae Trichobaris mucorea Lec -_----- Tobacco-stalk weevil____-- MODACCOStalkg es a ee ee aIn the preparation of this list we are under obligations for assistance to Mr. F. H. Chittenden, who has also furnished information in regard to the food habits of the species. 21739—No. 45—04—4. 50 Insects often mistaken for the boll weevil—Continued. Scientific name. Common name. Usual food plant. Plate figure OTHER BEETLES. | | Monocrepidius vespertinus Pah nee eore s eer pant Larva in grass roots ____. XVI, 70. Notoxus monodon Fab_-_-__-_ JES. | es RE SA ae Larva in ground _______- Let). fee aree Ataxia erypta Say__-.--.2 +=. | Cotton-stalk borer ___....| Cotton stalks _______.____. XVI, 68. OLD TUS IT COLTS IMTS ea eo | epee ee ID exer mares lool) oa eee ee : : | | Carpophilus hemipterus Linn __|-__...-_---- i Bee a lh ae Developsin decaying bolls ___________- = | Cappopialeys: AUC Cees MANO ee |e ee ea | GO)! Saab e es Pee ae &a |e eas ae Paes Epurea cestiva Linn ___-.------ eee er er geet ae Loren eel Seen do? 2 esas ee teeta Se Cathartus gemellatus Duy ___--- Grains beetics sae ere (i [sou nee One efi F a oe Tribolium ferrugineum Fab____ Houmbeetlere=ssasere ane | Attacks seed aes se as [sees aa ee BUGS AND OTHER INSECTS. | | Homalodisca triquetra Fab _.... Sharpshooter_-..._______- l@otton-stal kc =a sean tee XVI, 65, 66.. Oncometopia undata Fab _-_---- | Waved sharpshooter ____. eras dO ties. oe ee eee Dysdercus suturellus H-Sch _...| Cotton stainer__......_.- |. otton! bolish :. Summa XVI, 67. \ | IS COTTON-SEED MEAL ATTRACTIVE ? LABORATORY OBSERVATIONS. On account of the popular impression that cotton-seed meal will attract weevils it has been necessary to conduct a rather full series of experiments. To ascertain the possibility of using this substance as an attractant for the weevil in field work three series of laboratory tests were first made. The weevils used were obtained from the same source in all tests. The first series was designed to test the ability of the weevils to live upon cotton-seed meal alone asa food. The sec- ond series was intended to show whether the weevils would prefer the meal to cotton leaves as an indication of the possibility of attracting hibernated weevils before the formation of squares in the spring. The third series was planned to show whether the weevils would pre- fer the meal as a food when squares could be easily found. The cotton-seed meal used was obtained fresh from the oil mill and the experiments started during the latter part of November. Weevils fed rather sparingly upon the meal in Series I. It did not seem to agree with them as a food and they showed no special inclina- tion to feed upon it. Twenty-three of the 24 weevils confined upon meal alone died in from 2 to 13 days, showing an average length of life of slightly over 6 days. These weevils either starved to death rather than eat the cotton-seed meal or else they were not able to eat it. The dry and empty bodies of all dead weevils showed that death was caused by starvation and not by disease. Being entirely covered with the fine meal did not seem to have any bad effect upon them. As weevils without food or water showed an average length of life slightly over 6 days, agreeing exactly with the period in this test, it appears that cotton-seed meal is not only not a food for the weevil, but also that it is not capable of prolonging their lives to any appre- ciable extent. d1 In Series II 21 weevils were confined with fresh cotton leaves and ecotton-seed meal as food. During the 297 ‘‘ weevil-days” that this experiment was continued but one weevil died. The average period of the test for each weevil was 14 days. The weevils fed almost wholly upon leaves. Occasionally one would feed a little on the meal, but they certainly preferred the leaves, and the results show that leaves alone were responsible for the longer life of these weevils. The 20 survivors were placed in hibernation December 20, 1902, but ali died before April 15, 1903. In Series III freshly picked squares were placed with the meal to see which would attract the weevils. Fresh meal, as well as squares, was supplied at frequent intervals. During the 158 ‘‘ weevil-days” that this test continued not one of the 10 weevils died. The average period of the test was almost 16 days, and after it the weevils were placed in hibernation, but all died before April 15, 1903. In only one instance was a weevil observed feeding upon the meal. From this test it was evident that cotton-seed meal has not the power to attract weevils from squares, even when the latter have been picked for several days. In spite of the complete failure indicated by these results, a series of field tests was made during the late fall of 1902. FIELD TESTS. In order to settle this question finally, two series of field tests were made, one during the fall, when weevils were abundant but full-fed and cotton still standing, and the other during the early spring, with the view of attracting weevils as they came from hibernation before cotton began to square. Fall of 1902.—Cotton-seed meal fresh from the mill was placed in 10 cheese-cloth bags, which were shaken so that the fine dust from the meal covered the outside of each bag. The bags were numbered and then tied to cotton plants in infested fields at about the middle of the plants. The bags were so distributed as to test fields in which the following conditions prevailed: One field entirely black from frost, one nearly black, one about half green, and one still entirely green. The number of weevils on the plant to which the bag was attached was noted each day to ascertain in a general way the number of wee- vils which would be very near the meal and able to reach it in the ordinary course of travel over the plant without having to fly to it. Weevils on adjacent plants would naturally come within the sphere of influence if such existed, but they were disregarded. After the failure of the meal to attract weevils in the field became apparent, weevils were caught and placed upon the bags to see if they would stay there. Altogether 65 observations were made, covering a period from Novem- ber 24 to December 16. The weather was generally cool, averaging 52 about 61° F., mean temperature, and cotton had ceased to grow. Counting each weevil found at each observation, only 5 were found upon the 10 bags of meal. Of these 5, 3 were hidden in the folds of the cloth for shelter and were not feeding. One weevil was counted twice and was the only one found that appeared to be feeding upon the meal. During this period a total of 163 weevils was found upon the top parts of the plants to which the bags were attached. This is con- siderably below the real number present, because in many instances this examination was not made, and doubtless weevils were overlooked even when examination was made. “At various times 27 weevils were placed directly upon the bags of meal and given every opportunity to show whether they would stay thereon if they accidentally found the meal. Only one of this num- ber stayed tpon the bag for 24 hours, and this one remained in the shelter of the cloth. The unattractiveness of cotton-seed meal for the weevils seems absolutely proven so far as fall conditions are concerned. Spring of 1903.—These tests were intended to show whether hiber- nated weevils would be attracted to the meal before squares were to be found in the field. Two series of experiments were planned, using four bags of meal in each. For the loeation of the first series a field was chosen which was known to haye been badly infested with wee- vils up to December 18, 1902. This field was not replanted with cot- ton in 1903, nor was there another field in the vicinity, so that weevils coming from hibernation would find no possible food except the meal. A number of live hibernated weevils was taken from this field, so that there can be no doubt of the presence of many of them. The bags of meal were placed near apparently favorable hibernating places. Fifty-five observations were made under these EE URIS but not a weevil came to the bags of meal. PIES For the second series a field was selected in which occasional seppa cotton plants were found. The plants had been allowed to stand through the winter in this field, and hibernated weevils were quite abundant. The bags of meal were here attached to stakes driven beside seppa plants. More than 50 observations were made after weevils were known to be out of their winter quarters. Nine weevils were found upon the seppa cotton plants beside which the bags of meal were placed, but not a weevil was found on the meal. Only one conclusion can be drawn from these experiments. Under no conditions will cotton-seed meal serve as a food for the weevils, and it shows no power whatever of attracting them. THE POSSIBILITY OF BAITING WEEVILS WITH SWEETS. ATTRACTIVENESS OF VARIOUS SWEETS. On account of the considerable publicity given the theory that it might be possible to destroy the weevil by attracting it to sweetened poisons, a number of experiments were performed along this line. D3 In the course of this work Mr. G. H. Harris employed in the labora- tory tests a large variety of sweets. White granulated sugar, two or three grades of brown sugar, two or three grades of molasses, and the best strained honey were among the sweets tried. The conditions were such as to lead the weevils to eat the sweets if they would ever do so. The only alternative offered them for food was a supply of rather old cotton leaves such as weevils never touch in the field. In spite of the unfavorable conditions for getting at the real choice of the weevils they showed little inclination to feed upon the sweets except in the case of honey, which seemed to attract them quite strongly. Many weeviis fed upon the unattractive leaf tissue or upon the broken end of the petiole rather than upon the sweets. The result of Mr. Harris’s experiments with undiluted molasses applied to plants in the field as summed up in his own words was that ‘‘nothing indicated that the weevils were attracted by the odor of sweets.” Honey was then tried, and this did attract a few weevils. Mr. Harris’s general conclusion, based upon the results of his experi- ments, was that ‘‘ while a high grade of sweets seemed to have more attraction than a cheaper grade, neither can be depended upon to 99 attract the weevils for poisoning.”’ ATTRACTIVENESS OF SWEETS TO HIBERNATED WEEVILS IN LABORATORY. The sweets used in these tests were of three kinds: High-grade molasses, common molasses, and light-brown sugar. The weevils were brought in from the field and left for one week without food or drink previous to the beginning of the tests on April 2, 1903. Three weevils were used with each kind of sweet, the latter being in their strongest form and the sugar in a saturated solution. The inclosing apparatus was formed by placing two bottles mouth to mouth with sufficient space for air, but not enough for the escape of the weevils between them. In the bottom of one bottle was placed the sweet and the second leaves of cotton in the bottom of the other. The weevils were then inclosed, and the cages thus formed were placed in a hori- zontal position in the dark to eliminate every possible influence of direction of light, relative elevation of food, ete. The food supplies were renewed occasionally, and the location of the weevils relative to the food in each cage was noted frequently. The weevils were counted at each observation. The results of these observations are briefly summarized in the following table: TaBLE XII.—Attraction of various sweets vs. cotton, second leaves. | Number /Number| Number “ & of ob- | of wee- | of wee- Character of sweet. serva- | vilson | vilsat tions. | cotton. | sweets. Besbimolasses=cage id 222 2 see ee ee ee Pet SAE eee: 20 25 | 1 IBESisINOlASSeSNGaAr Ol aue nm pre ee neon SUPE ie 2h Se a eS | 13 29 5 Commonimolasses cace Bees Le aa ea es 18 42 4 EO SUSIE MN CALC eset eh ee me ee | 21 48 8 AMONG SA oe Se ae ta nee oo ee Re al ee em 12 144 | 18 54 These figures become even more striking in consideration of the fact that the cotton leaves were often purposely left until they became moldy and decayed or dried and wholly unfit for food. It was at such times that most of the weevils sought the sweet in preference. Should we leave out of the account the weevils found at the molasses or sirup when the cotton was unfit for food, the number attracted there would be reduced fully one-half. In either case the fact remains that none of the sweets can be said to have attracted weevils from the cotton leaves. INFLUENCE OF SWEETENED WATER UPON FEEDING OF WEEVILS ON COTTON PLANTS. It is easy to demonstrate that weevils will in confinement feed upon sweet solutions. To prove that they will show the same attrac- tion to it in the field is a far more difficult matter. For the purpose of these experiments, cheap molasses was used, mixing 1 part of molasses with 25 parts of water, as is generally recommended in spraying formule. Three pairs of young plants which had not begun to square were then selected from those growing upon the laboratory grounds. The plants in each pair were of equal size, and both in healthy condition and standing closely enough together to be both covered by one cage. One plant of each pair was then dipped in the sweetened water, while the other was left in its natural condition. In each of the cages 10 weevils were then placed upon the ground and midway between the bases of the plants. The object of the test was to see which plant, the treated or untreated, would attract the larger number of weevils. During the first three days observations were made several times each day. Weevils found upon either plant were counted at each observation. A summary of the observations made on the first day before the liquid had dried showed 15 weevils upon the sweetened plants and 16 on those not sweetened. These results were so remarkably even that no attraction or repulsion could be ascribed to the liquid before it dried. During the ten days covered by the observations, however, 63 wee- vils were found upon the unsweetened plants and only 45 upon those sweetened. The weevils fed largely upon the petioles and somewhat upon the blades of the leaves and the main stems of the plants. No indication was observed of special feeding upon the ‘“‘gloss” left by the drying of the sweetened water. In each cage the normal untreated plant was destroyed before the treated one. During the first half of the observations 52 weevils were found feeding upon the unsweetened plants and only 32 upon the sweetened. Only after every leaf on the untreated plants hung black and dead, while the sweetened plants were in much better condition, did more weevils attack the sweetened plants. 55 Not only did these tests show that molasses in solution has no attrac- tion for the weevils, but also that the sticky coating left after the liquid has dried acts more as a positive repellant to them. FIELD TESTS FOR HIBERNATED WEEVILS, USING PURE MOLASSES. As a final experiment to settle the possible usefulness of molasses in the weevil fight, a large series of tests was undertaken in the field to see if the pure, undiluted molasses would not prove- attractive to weevils as they came from hibernation. To insure a continuous sup- ply of fresh molasses a test tube was nearly filled and then rather tightly plugged with a small stopper wound with cotton. The tube was then fastened in an inverted position to the top of a stake about 2 feet long, and as the molasses gradually oozed through the cotton it ran slowly down the stake, forming a streak of continuously fresh molasses a foot or more in length. The supply would thus last for several days and was then easily replenished. This apparatus, as shown in Pl. XII, fig. 45, was then placed beside a vigorous seppa cot- ton plant in the field at the season when the weevils were beginning to leave their winter quarters and seek food to break their long fast. Both high and low grades of molasses were employed in these tests, three tubes of each being used. Altogether 84 observations were made between April 24 and May 15, 1903, during which period most of the weevils emerged from hibernation. The results again proved disappointing, for only a single weevil was ever found at the molasses. This individual sipped occasionally at the sweet, wandering up and down the tube in the intervals. It did not appear to be satisfied and did not remain long at or near the molasses, but flew away and was not found there again. The failure of the molasses to attract was not due to the searcity of weevils in the field. During the period of observation 25 weevils were found working upon seppa cotton very near the molasses tubes, and certainly within. reach of its attractive influence, provided it had any. More weevils were also found in the same field, but at some- what greater distances from the tubes. During the warm days toward the close of the experiment many butterflies, mostly Vanessa atalanta and some Anosia plexippus, came tothe tubes. A few specimens representing several species of beetles and many ants were also found. None of the experiments made, either in the laboratory or in the field at Victoria, Tex., has shown that weevils are attracted in even the slightest degree to any grade of molasses, either in its undiluted or diluted form. No sugar solution has been found to possess any more attraction than does molasses. Honey appears to be an-espe- cially attractive sweet, but is too expensive for use in this manner. Considering the facts that these experiments have been much more numerous and that they have covered a much broader range of con- 56 ditions than any previously performed, we must conclude that it yet remains to be shown that sweets of any kind have any value in the problem of controlling the boll weevil. FEIGNING DEATH. This interesting habit of the weevil is its first resort as a means of escape from its larger enemies. It has been the basis of many ma- chines designed to jar them from the plants and to collect them in convenient receptacles. If jarred from the plant, the weevil falls to the ground, with its legs drawn up closely against the body and the antenne retracted against the snout, which is brought inward toward the legs. The position is characteristic and can be more easily shown than described. See Pl. I, fig. 2. In this position it often remains motionless for some time. If further disturbed, so that it finds that its ruse has failed to conceal it, it will start up quickly, run a little way, and again fall over, feigning death. The color of the weevil so closely resembles that of the ground that it is quite difficult to find a fallen individual so long as it remains quiet. The habit is of great value in protection. If left undisturbed until it believes danger to be past, it recovers its footing and returns to the plant. REPRODUCTION. Under this general heading we present some of the most interesting observations which have been made upon the habits of the boll wee- vil. The relation of the sexes, the evident selection of clean squares for egg deposition, the great destructive power of the weevil, the rapidity of development, and the influence of varying temperatures upon its activity and development may also be classed as among the most important as well as most interesting observations. METHOD OF MAKING FIELD OBSERVATIONS UPON WORK OF WEEVIL. For the purpose of field study large cages (3 by 3 by 4 feet) were made, the covering being of fine wire screening (Pl. IX, fig. 36). Uninfested plants having plenty of squares were found by a careful examination of each square and inclosed by the cages. The number of weevils placed in each cage was varied according to the number of squares within, ranging from 2 to 5 at various times. In making the daily observations the cage was entered and each square examined. Each square found attacked in any way was marked with a numbered tag containing full data as to the lot of weevils and the number pres- ent, date, and nature of injury (PI. IX, fig. 37). After all weevils had been found the cages were removed to new uninfested plants for another day’s work. Close watch was kept upon all tagged squares upon succeeding days, and every important change taking place in each square was added to the record on the tag. The special points Bul. 45, Div. of Entomology, U. S. Dept. of Agriculture. PLATE VIII. EXTERNAL AND INTERNAL INJURY FROM FEEDING ON BOLLS. Fig. 34, External appearance of large boll much fed upon, natural size; fig. 35, internal appear- ance of same boll, natural size. (Original.) Bul. 45, Div. of Entomology, U. S. Dept. of Agricuiture. PLATE IX. Fia@. 36.—CAGES USED TO CONFINE WEEVILS IN FIELD. (ORIGINAL). Fic. 37.—PLANT SHOWING TAGGED SQUARES FROM CAGE WORK. (ORIGINAL. ) Bul. 45, Div.-of Entomology, U. S. Dept. of Agriculture. PLATE X. EGG AND FEEDING PUNCTURES: EFFECTS ON SQUARES AND BOLLS. Fig. 88, Boll showing two locks destroyed by two feeding punctures made by a male weevil, two- thirds natural size; fig. 39, square showing external appearance of two egg punctures, natural size; fig. 40, wart formed on side of square in healing an egg puncture, natural size; fig. 41, egg deposited on inside of carpel of a boll, two-thirds natural size; fig. 42, normal and flared squares, natural size. (Original.) 57 noted in each case, so far as was possible, were: The formation of a distinct wart; time of flaring, yellowing, and falling; the emergence of adult; presence of a parasite; death of larva, pupa, etc. == ae Ee e|| 71.6 68. 1 67.1 62.6 67.9 Glen. 64.5 INOW ASO Oe ee a ee a | 63.7 | S500 56.8 57.8 BY (EG: 58.9 58.9 . Average for 6 months__ | 74.8 74.8 74.4 71.2 74.6 74.6 12.2 From these considerations of temperature difference and judging the varying influence as ascertained at Victoria, it seems that the weevil may prove less and less destructive as it spreads to the cooler portions of the cotton belt, though this supposition is likely to be nullified by an ability to adapt itself to new conditions. While it must be admitted that nothing, so far as now known, seems certain to prevent the spread of the weevil to any latitude where cotton is now grown, it does seem probable that its control may be more easily accomplished in the more northern portions of the cotton belt than in the Texas area now infested, and since it has been most positively demonstrated that better than the average crop may here be grown in spite of the depredations of the weevil, there would seem to be no special reason for a panic over the future of the cotton crop. Cotton has been and still will be grown in spite of the weevil. The present promise is that those planters who enter the struggle with determina- tion, and who adopt the advanced methods which have proven suc- cessful wherever tried, will realize practically as large a profit from eotton raising in the future as it has been possible to obtain in the past. DISEASES. Especially in moist breeding jars, weevils often die from what appears to be a bacterial disease. The body contents liquefy, turning to a dark brown in color, and have a putrid odor. Death follows quickly, though not until after putrefaction has begun. ‘The fre- quency with which several weevils died in the same jar at about the same time indicates that this disease may be contagious. It has not been found in the fields, however, and may have been due entirely to abnormal laboratory conditions. It is doubtful whether the following observations upon fungus attacks upon weevils should properly be classed with diseases, but as there is a possibility that the attack may have been of this nature, the observations may be given here. In July, 1902, a lot of squares sent by mail from Calvert, Tex., to Victoria, was so long delayed upon the road that they were very 105 moldy when received. Thirteen apparently healthy pup were removed from these moldy squares with the intention of rearing the adults. The pupze were kept moist, and in a short time 56 died, apparently from the attacks of an unknown species of fungus. The remainder were then kept dry, but in spite of this precaution 6 more died, only 2 becoming adult. In another lot of 27 pupe, 5 died, apparently from attacks of the same fungus. Specimens of the dead pupe were sent to the pathologist of the Bureau of Plant Industry of the Department for determination of the fungus. It was pronounced to be a probably new species of Asper- gillus. As no species of this genus is known to be parasitic, it may be that the pupee died from some other cause and that the fungus was entirely saprophytic. The external appearance of the fungus so soon after the death of the pupe, the large mortality prevailing, and the known fact that pupz develop uninjured in the presence of many species of molds leads to the suspicion that it may have had some part in causing the death of the insects. In 1894 Prof. C. H. T. Townsend, while engaged in the study of the boli weevil, found in a field at San Juan Allende, Mexico, a speci- men of a dead pupa which had been attacked by a species of parasitic fungus (Cordyceps sp.). As no other cases of attack by this fungus have been reported, its occurrence is probably very rare. PARASITES. BREEDING OF PARASITES. Owing to the importance attached to parasites in the control of many pests, considerable time has been devoted to the rearing of para- sitic enemies of the boll weevil. From the very nature of the habits of the weevil, no perfectly satisfactory method of breeding these para- sites could be devised. The apparatus used was exceedingly simple. Squares which were thought to be infested were picked or gathered in the field, and cleared, so far as was possible, of all that might pro- duce parasites not developed from the weevils. Small lots of these squares were placed in paper bags, each fitting tightly over the open mouth of a glass jar. As both parasites and weevils upon emergence naturally make their way to the light, they could easily be seen in the glass jars and at once removed. Even when thus bred something must be known of the habits of each species of insect produced or of its close allies to determine whether it is really a parasite upon a weevil larva, a hyperparasite, or merely a vegetable feeder devel- oped in the decaying square. Many small flies breed in such decaying matter and were caught in the jars, but these must all be acquitted of being parasites upon the weevil. The results are therefore made somewhat uncertain because of the impossibility of isolating the weevil larve. A condensed summary of the results in breeding parasites through two seasons’ work is presented in Table XX VIII. 106 TABLE XXVIII.—Breeding of parasites. Parasites. Locality. Collector. Dates ‘Squares. peewee Bracon Creer mellitor. Biss Squares picked from plants and from ground. 1902. Calvert. Dexia se sea eee Garerarrisess= July, August 2,566 277 3 1 Wao orath, MNee< 8 So Wa Bren Seen | eee doses = 645 210 1 itt Guadalupe; Lexa ses { ae = aa ie |August Sees 387 108 1 0 1903. IVs CLOT ase exc as eer Weta Hinds eeee. June =e 881 278 10 0 On eae ie Be eee | Sag Oeste es dfll\yossosossle 264 111 3 1 1D) Ooo ener anon eee Com ee eee August... -.-.- 463 251 0 0 Infested squares dried on the plants. Wi CLOLI aa llOxee=s aa eenes W.E. Hinds------ July, August 342 120 45 5 Motal Asso Sees | Se eee eS Seen ee ae ace ee meee ee 5,548 1, 355 63 8 From these observations it appears that 24.4 per ceht of the 5,548 squares used produced adult weevils, while only 1.3 per cent of the Sr ee we i Da ora Ne I De ee ~~ Ss Fig. 4.-_Bracon mellitor, parasite of boll weevil—much enlarged (original). total squares contained parasites. Among the parasites obtained, 90 per cent were of the single species Bracon mellitor Say (fig. 4). A single specimen of another un- doubtedly primary para- site, Sigalphuscurculionis Fitch, was reared. 1897. HOWARD, L. O.—The Mexican Cotton-boll Weevil, Circular 18, Div. Ent., U. 8S. Dept. Agric. (second series), pp. 8, figs. 1-5. A revision of Circular No. 14. It was issued in English, Spanish, and German editions. as (oa) (Len) ~ . Rtos, J. R.—Aparicion del ‘‘ Picudo” en la Laguna. El Pro- ereso de Mexico, Vol. IV, pp. 811-813. A reprint of an article in the same journal for August 15, 1895. 1897. Ed. Junta de Defensa Contra el ‘‘Picudo.” El Progreso de Mexico, Vol. V, pp. 8-9, Octobre 8. 1897. Ed. El Pieudo (Anthonomus grandis Boh.). Documentos ref- erentes a stu. Existencia en Mexico y a su Invasion in los 4 Estados Unidos del Norte. Mexico, Oficina Tip. de la Seere- taria de Fomento, pp. 100, figs. 1-5. Consists of a few letters from Mexican cotton planters and translations of some of the publications of the Division of Entomology. 1897. BALESTRIER, L. DE.—Las Medias precautorias contra las Plagas | que asolan a la Agricultura. El Progreso de Mexico, Vol. IV, | pp. 575-576, May 22. The author urges the necessity of some definite action, a Es) 1897. HowArp, L. O.—The Mexican Cotton-boll Weevil in 1897. Cir- eular Div. Ent., U. 8. Dept. Agric., No. 27 (second series), pp. 7. 1897. HOwARD, L. O.—Insects Affecting the Cotton Plant. Farmers’ Bulletin, U. S. Dept. Agriculture, No. 47, pp. 16-23, figs. 7-11. Reprinted from Bulletin 33, Office of Experiment Stations, U.S. Dept. Agric., pp. 317-350. 1898. HOWARD, L. O.—Remedial Work against the Mexican Cotton- boll Weevil. Circular Div. Ent., U. 8. Dept. Agric., No. 33 (second series), pp. 6. This is supplementary to Circular No. 27. 1901. RANGEL, A. F.—Estudios preliminares acerca del Picudo del Algodon (Insanthonomus grandis I. C. C.). Boletin de la Comision de Parasitologia Agricola I, No. 3, pp. 93-104, Pl. IX, and figure. Deals with 45 experiments regarding destruction by means of hot air, hot water, steam, haplaphyton, and arsenic. ~ 1901. MAauLuy, F. W.—A Preliminary Report of Progress of an Inves- tigation concerning the Life History, Habits, Injuries, and Methods for destroving the Mexican Cotton-boll Weevil (Anthonomous (sie) grandis). Authorized by Special Act of the twenty-sixth Legislature of Texas, pp. 1-30, supplement pp. 30-405. 1901. Matty, F. W.—The Mexican Cotton-boll Weevil. Farmers’ Bulletin, U. 8. Dept. Agric., No. 130, pp. 30, figs. 1-4. A reprint, with minor corrections, of the preceding, excepting the supple- ment. 1901. RANGEL, A. F.—Segundo Informe acerca del Picudo del Algo- don (Insanthonomus grandis I. C. Cu.). Boletin de la Comision de Parasitologia Agricola, I, No. 5, pp. 171-176. 1901. RANGEL, A. F.—Cuarto Informe acerea del Picudo del Algodon (Insanthonomus grandis I. C. Cu.). Boletin dela Comision de Parasitologia Agricola, I, No. 7, pp. 245-261, Pls. XVI, X XIII. 1902. Hupson, E. H.—The Mexican Boll Weevil (Anthonomus grandis). Farm and Ranch (Texas), Feb. 1, 1902, p. 13, figs. 1902. HUNTER, W. D.—The Present Status of the Mexican Cotton- boll Weevil in the United States. Yearbook U. 8. Dept. Aerie. 1901, pp. 369-380, 1 fig. 1902. MALLY, F. W.—Report on the Boll Weevil. Pp. 70, figs. 3. Austin, State Printer. 1903. HUNTER, W. D.—Methods of Controlling the Boll Weevil (ad- vice based on the work of 1902). Farmers’ Bull. U. 8. Dept. Agric. No. 163, pp. 16, figs. 2. January. 116 1903. SANDERSON, E. D.—The Mexican Boll Weevil. Cire. 1, Ent. Dept. Tex. Agric. Exp. Sta. Press Notes, Vol. VY, No. 3; pp. 5, figs. 4. February. 1903. Kill the Boll Weevil. How to Grow Cotton in the Weevil Dis- trict. History of the Pest, its Habits, and the Remedies Plainly Disclosed. Pp. 8, figs. 4. Published by the Executive Committee of the Texas Boll Weevil Convention. 1903. CHAMPION, G. C.—Biologia Centrali-Americana, Coleopt., Vol. SEV pi4, p:- 186, PL digss 3) 3a. April. om — 1905. Save the Cotton Crop. ‘Testimony of Cotton Growers on Boll Weevil. How to Insure the Cotton Crop in the Weevil District. Pp. 16; published by the Executive Committee of the Texas Boll Weevil Convention, Bull. No. 2, May. Also published in German under the title, ‘‘ Rettet die Baumwolle,” and in Bohemian under the title, ‘‘ Zachrafite bavinu.” 1903. SANDERSON, E. D.—How to Combat the Mexican Cotton-boll Weevil in Summer and Fall. Cire. 4, Ent. Dept. Tex. Agric. Exp. Sta. Press Notes, Vol. V, No. 1, pp. 4. August 10. 1903. Improved Cotton Seed for Texas Planting. Published by the | Executive Committee of the Texas Boll Weevil Convention, pp. 32. Bull. 4, ‘Nov. 9; revised Nov. 17. 1903. MorGAN, H. A.—The Mexican Cotton-boll Weevil. Circular No. 1, La. Agric. Exp. Sta., pp. 10, figs. 3, map1. November. 1903. WILSON, JAMES.—Report of the Secretary of Agriculture, 1903. Pp. 102-106 under heading, ‘‘ Crisis in Cotton Production,” deals with the Boll Weevil problem. December. 1903. CONNELL, J. H.—Proceedirgs of the Second Annual Session Texas Cotton Growers’ Convention, Dallas, Tex. Pp. 99; many illustrations. December. — 1904. HUNTER, W. D.—Information Concerning the Mexican Cotton Boll Weevil. Farmers’ Bull. No. 189, U. 8. Dept. Agric. Pp. 1-31; figs. 1-8. February. ee O | nie a ‘ .