we ( BUREAU OF ENTOMOLOGY. L. O. Howarp, Entomologist and Chief of Bureau. C. L. Maruatt, Hntomologist and Acting Chief in Absence of Chief. R. 8S. Cuirton, Haeccutive Assistant. W. EF. Taster, Chief Clerk. F. H. CH1IrrenpDen, in charge of truck crop and stored product insect investigations. A. D. HopxKIns, in charge of forest insect investigations. W. D. HUNTER, in charge of southern field crop insect investigations. I’. M. WEBSTER, in charge of cereal and forage insect investigations, A. L. QUAINTANCE, in charge of deciduous fruit insect investigatiois., EK. F. PHILIPS, in charge of bee culture. D. M. Rocers, in charge of preventing spread of moths, ficld work. Ro.iia P. CurRig, in charge of editorial work. i MABEL CoLcorD, in charge of library. SOUTHERN FIELD Crop INSECT INVESTIGATIONS. W. D. HuNTER, in charge. W. D. Pierce, G. D. Smitu, J. D. MITCHELL, Harry PrinKus, B. R. Coan, R. W. MOoRELAND, engaged in cotton-boll weevil investigations, I. C. BrsHopp, A. H. JENNINGS, H. P. Woop, W. V. KING, engaged in tick investi- gations. A. C. Morcan, G. A. RUNNER, S. HE. CRuMB, D. C. PARMAN, engaged in tobacco insect investigations. T. E. Hottoway, E. R. BARBER, engaged in sugar cane insect investigations, EK. A. McGrecor, W. A. THOMAS, engaged in red spider and other cotton insect investigations. J. L. Wess, engaged in rice insect investigations. 2. A. CootEy, D. L. VAN DINE, A. F. ConRADI, C. C. KRUMBHAAR, collaborators. II CIRCULAR No. 152. Issued July 10, 1912. United States Department of Agriculture, BUREAU OF ENTOMOLOGY. L. O. HOWARD, Entomologist and Chief of Bureau. THE RICK WATER-WEEVIL AND METHODS FOR ITS CONTROL. (Lissorhoptrus simplex Say.) By E. 8. TUCKER, . Entomological Assistant. ECONOMIC IMPORTANCE. The most serious insect enemy of growing rice in the Southern States is the rice water-weevil (Lissorhoptrus simplex Say) (fig. 1). When in its larval stage, the insect is known to rice growers as the “rice root-maggot.” The larvee feed on the roots of rice plants, and the adult weevils cause some harm by feeding on rice leaves. Owing to the extensive growing of rice in sections of Louisiana, Texas, and Arkansas within recent years, the weevil has found very favorable conditions in the rice fields for its multiplication in propor- tion to the increase of the acreage and to the number of years in which rice has been grown in any section. The development of definite rice-growing areas in these States has naturally resulted in particular centers of high infestation by the weevil. Rice growing has consequently been attended by great damage to the crops on account of the insect’s attacks. The amount of loss that is occasioned by the attacks is difficult to estimate, as the reduction of yield has been variously reckoned in different localities. Since all fields are not affected alike and differ- ent portions or spots of a field are apt to suffer the severest injuries, although the plants seldom fail outright, the growers differ much in their opinions of the extent of damage which they sustain, but all agree in the declaration that it is considerable. General statements of the shortage of production include a report by a grower at Beau- mont, Tex., who placed his loss as low as 1 per cent; but the attacks in some fields at Stuttgart, Ark., have been severe enough to cut down the yield as much as 75 per cent. > THE RICE WATER-WEEVIL. Vic, 1.—The rice water-weevil (Lissorhoptrus simplex) : a, Rice plant showing injuries; b, larval scars on section of root; c, section of rootlet showing feeding scars; d, water line; e, e, e€, roots severed by larve; f, injured leaf; f’, enlarged section of injured leaf; g, adult beetle, dorsal view, much enlarged; h, antenna of beetle, more enlarged; enlarged segment of larva, lateral view; k, i, larva, side view, much enlarged: j, dorsal structure of larva. (Original.) THE RICE WATER-WEEVIL. 8 The recent work of the bureau on the rice water-weevil was begun in 1910 by Mr. C. E. Hood; working under the direction of Mr. D. L. Van Dine. The present writer began work on the problem in 1911. In this circular many notes made by Mr. Hood are incorporated. The object of this paper is to give as much practical information as is now available about the weevil and measures for its control in order that rice growers may make proper efforts in fighting the pest and secure larger crops. The cooperative facilities afforded by the Agricultural Experiment Station of Louisiana, through Prof, W. R. Dodson, director, in providing accommodations at the State Rice Station, Crowley, La., and allowing free use of the unpublished notes comprising a preliminary investigation of the rice water-weevil by Mr. Wilmon Newell, in 1909, deserve grateful acknowledgment. HISTORICAL ACCOUNT AND DISTRIBUTION. The weevil was originally described in 1831 as Bagous simplea by Thomas Say. It and another species of weevil were given the generic name of Lissorhoptrus by Dr. J. L. LeConte in 1876. Le- Conte and Horn have stated that the weevil commonly inhabits swampy places throughout the eastern part of the United States. Its northern range extends into the Lower Peninsula of Michigan, according to Hubbard and Schwarz, and Dury has recorded the spe- cies as being taken near Cincinnati, Ohio. . It is also reported from New Jersey, Maryland, and the District of Columbia. Mr. E. A. Schwarz has concluded “ that the genus Lissorhoptrus occurs all along the Atlantic coast (including the Gulf of Mexico), recurs along the Great Lakes, and is occasionally found inland.” As an injurious insect, the species first attracted the attention of rice farmers along the Savannah River in Georgia and South Caro- hina. In 1881 Dr. L. O. Howard visited a rice plantation known as * Proctor’s,” and owned by Col. John Screven, on the South Carolina side of the river, a short distance below Savannah, Ga., for the pur- pose of studying the insects affecting rice crops. An account of his observations, including notes on the rice water-weevil, was published in the report of the United States Commissioner of Agriculture for 1881 and 1882. But little advance has been made in further knowl- edge of rice-crop insects up to the present investigation. DESCRIPTIONS OF STAGES. The adult——The mature insect is a small, dark-gray weevil (fig. 1,g). The technical description by Mr. E. A. Schwarz in the account above mentioned is here quoted: Lissorhoptrus simplex—tImago: Average length from tip of thorax, 3 mm, Oblong-oval, covered with large, dirt-colored scales, but usually entirely en- 4 THE RICE WATER-WEEVIL. veloped in an argillaceous coating, which renders scales and sculpture irrecog- nizable. Rostrum stout, as long as head and thorax, subcylindrical, densely rugosely punctulate, neither sulcate nor carinate; head densely punctulate. Thorax as long as wide, constricted anteriorly, lateral lobes well developed, sides moderately rounded, base truncate, a finely impressed median line, sur- face densely rugosely punctate, sides at middle with a shallow transverse im- pression. Elytra much wider at base than thorax and about twice as long; humeri oblique, strongly declivous at apex, punctate-striate, interstices wide, subconvex, 3d and 5th more prominent at declivity than the rest. Prosternum fiattened, transversely impressed in front of coxe; abdomen coarsely punctate. Tibize somewhat curved, armed with a strong terminal hook; tarsi narrow, third joint not emarginate; claws slender, approximate. Very little difference exists between the sexes. The females usually have a shghtly larger body than the males, and are often more dis- tinctly marked with a black area on the back. The marks of colora- tion, however, show more plainly on live moistened specimens in the field than on dry examples either alive or dead. According to Mr. W. D. Pierce, a secondary sexual character is presented by the con- figuration of the scrobe on the beak. He has determined that the scrobe of the female is shghtly curved, but in the male it is practi- cally straight. These fine distinctions are difficult to make out with certainty on account of the natural curvature of the beak. The pupa.—No example of the pupa fit for description has yet been obtained, as it is very soft and any slight pressure or touch that is ex- erted in attempting to remove one from the mud crushes or distorts it. The egg.—All attempts to secure deposited eggs have afforded only partial results. For purposes of description dependence must at present be placed upon the appearance of eggs obtained by dissection of gravid female weevils. Mr. Wilmon Newell, in presenting a de- scription based upon such observations, has stated that the egg is pure white, cylindrical and shghtly curved in form, and has a length about five times the diameter. It 1s barely visible to the naked eye. LIFE HISTORY. SEMIAQUATIC HABITS. Water is an element in which the weevil delights. It swims readily on or beneath the surface, and it feeds, rests, and mates almost as fre- quently in the water as above it. To determine how long the adults can live under water, Mr. C. E. Hood conducted a test in which one weevil died after passing the first 24 hours of submersion, but two did not die until after being kept submerged for fully 96 hours. The weevil does not carry a bubble of air for breathing purposes when it goes below the surface, although tiny globules of air are apt to adhere to parts of the body. Without water, the insect can not breed. The eggs are probably deposited on roots under water or in mud, and the THE RICE WATER-WEEVIL. 5 larva, and doubtless also the pupa, require a bed of saturated earth in which to live. Wet conditions of soil with suitable vegetation appear to be necessary for the development of all the stages. FOOD PLANTS. The semiaquatic life of the insect demands that its proper food plants be adapted for growing in moist situations or entirely in water. The adult weevil itself is not disposed to feed on any plant unless the roots are at least partially covered with water or soft mud. In South Carolina Dr. Howard observed weevils feeding on “* Sagit- taria, Scirpus, Cyperus, Nympheea, and Nuphar ’—plants commonly known as arrowhead, bulrush, galingale, water lily, and spatter-dock. Besides these, he reported wild rice (Zizania aquatica) as well as cultivated rice (Oryza sativa). One specimen has been collected as a visitor on Baptisia at Victoria, Tex. All positive records of addi-: tional food plants refer entirely to grasses and they are the result of observations that were mostly made in Louisiana. Mr. Hood has re- ported some of the Louisiana grasses by the common names of “ bull grass” and “nigger’s wool,” which grew at Crowley. ‘“ Hurrah grass” was recorded by Mr. D. L. Van Dine at Matagorda, Tex. Adult weevils fed on the leaves of these undetermined grasses and the larve were found on the roots of the first, which was identified by the writer as a Paspalum and was said to have been introduced into the country. “ Bull grass” is a very common term in the section and refers to several species of grasses. The occurrence of weevils on Walter’s swale grass (Paspalum membranaceum) was first observed by Mr. Newell at Lake Arthur, La. While similar observations have been made by the writer at Crowley, La., and Pine Bluff, Ark., the finding of larve on the roots of the grass at Crowley presented complete evidence of the true host relationship of the plant. This fact, however, may have been dis- covered by Mr. Newell two years previously at the same place where he found larve infesting the roots of a stocky Paspalum, which he was inclined to regard as another species. Also during the season of 1911, at Crowley, La., the writer found two other species of grass which attracted the weevils from the nearest rice plants. One of these was Bermuda grass (Capriola dactylon). It grew on a levee in a rice field which had become partly overflowed with the flood water. As an attempt had been made to grow it on the land previous to the rice crop, its occurrence under flooded conditions was exceptional, and no larve were found attack- ing the roots. It can not be considered as a proper host plant. In the other case, a bunch of “ water crab grass,” undoubtedly a species of Syntherisma, was making a desperate struggle for existence 6 THE RICE WATER-WEEVIL. within a flooded rice field. Having evidently started into growth before the field became irrigated, this crab grass was able to live in a depth of about 6 inches of water. Not only were the leaves severely fed upon by weevils, but the roots were attacked by larve. APPEARANCE OF ADULTS IN RICE FIELDS. Since the growing of rice offers special inducements for the breeding of the weevil, due to the attraction of the plants and the wet condi- tions which they demand for growth, rice has become the favorite food plant of the insect. Directly after the rice fields are flooded the weevils appear and commence feeding on the leaves of the young plants. In southern Louisiana, where much of the water is supplied by canals, the irrigation of rice fields usually begins in the first week of May, but the time of turning on water in different fields is often later, the flooding sometimes not being done until in July to accord with late planting. Where water is pumped onto the fields, a steady flow must be maintained for several days before any large area of land can be inundated. The flooding of fields in Arkansas is not generally effected earlier than the middle of June. By following the application of water in every field the weevils gather most numerously on plants that stand in the depressions and lower portions having the deepest flood. Mr. Hood has counted as many as 18 weevils on a stool and 12 on a single plant. An average of at least 1 weevil to every 5 or 6 plants in one field has been reckoned by Mr. Newell. Some inclination to avoid direct sunlight during days of hot weather is shown by the weevils, as they seem to prefer positions in the shade of the plants and under the surface of the water. . | They are rather sluggish except when swimming and are disposed to feign death if taken in the hand. They show no inclination to fly during the day and even refuse to expand the wings on being tossed into the air. Passage between separate plants is accomplished in the daytime by swimming. That they can fly for long distances, however, is clearly proven by their attraction to artificial lights at night. This propensity will be more fully discussed with reference to methods of control. Invasion of fields must therefore be con- summated at night. NATURE OF ATTACKS BY ADULTS. Rice is attacked in the same manner as other similar host plants and the effects of the feeding by the adults are soon manifested by the appearance of scars on the leaves. (Fig. 1, f.) In the act of feed- ing, the weevil braces its body firmly on the upper side of a leaf, and moving slowly forward in a longitudinal direction either up or down the blade, it chews out the epidermis and produces a scar, leaving THE RICE WATER-WEEVIL. q the underside uneaten. These scars are very narrow, being in fact no wider than the spread of the mandibles, but they vary in length from a small fraction of an inch to more than 2 inches, depending on the time in which the insect engages in feeding. When the thin underside dries within the scar, it splits and forms an open groove throughout the injured space. The leaves suffer no serious ill effects from being fed upon unless the scars become numerous enough to cause wilting and dying. Adults prefer tender young plants rather than the coarser strong growth. MATING AND OVIPOSITION. Throughout the period in which the weevils remain in evidence, mating takes place on nearly all occasions when a male and female happen to meet, and this usually occurs on a leaf. The gravid females crawl down the stems of the plants and evidently deposit their eges singly in a puncture that is first gnawed in a root. Mr. Newell has mentioned that he has seen adult weevils which he be- lieved to be females make punctures on the stems below the water line. Mr. Hood and the writer have watched the operations of females when they apparently undertook to oviposit on rice roots within glass tubes. Each weevil thus observed deliberately sought out a place on a root and ate into it for about a minute. Then she reversed her body, gripped tightly, and pressed the tip of the abdo- men over the hole which she had eaten out. Mr. Hood has recorded that he saw the ovipositor in the form of a brown tubular organ in- serted into the hole. In this case the weevil remained in position without any apparent movement for 50 seconds before the ovipositor was withdrawn. The writer has not been able to see the ovipositor extended nor to detect an egg with certainty. The weevil may climb up above the water after each operation and rest for a long or short period, or continue her actions among the roots for a while. One weevil stayed among the roots for 45 minutes. The device that was designed and used by the writer for observing the method of oviposition by the weevils is illustrated in figure 2. In its construction a long lamp chimney was placed upright in a saucer and cemented at the base with plaster of Paris. A wire sup- port with the top bent into a loop of the proper size for steadying a closed-bottom glass tube, one with an inch diameter being used to hold the roots of a young rice plant in water, was first placed in the center of the saucer. The lower end of the support was also bent in a spiral to secure firmness after being set in the plaster. By means of a string tied to the upper part of the tube, it could be lowered through the top of the chimney into a standing position within the wire loop and also removed to permit close inspection of roots and insects inside of it whenever desired. 40996 ° —Cir. 152—12 2 8 THE RICE WATER-WEEVIL. NATURE OF ATTACKS BY LARVAE. Mr. Hood has stated that the larve are first found in the rice fields from one to three weeks after the turning on of the water, the (Li) TW iy, Ii UU HATA Hi tall} \ Fig. 2.—Lamp-chimney cage for rearing and observing the rice water-weevil: 4a, Glass lamp chimney; b, vessel containing plaster*of Paris; c, glass tube; d, wire support; e, rice plant; f, string lift; g, gauze; h, rubber band; i, j, beetles feed- ing. (Original.) time of their inception varying with the weather. Hot weather accelerates their development. The young larve, which have doubtless hatched from eggs laid in the roots, begin to feed on them, and in course of time as the larve increase in size they devour or sever large portions of the root system. They have been known to eat holes in large rice roots and burrow into them. Mr. W. D. Pierce, at Beaumont, Tex., in 1904, found vigorous larvee consuming the entire in- terior of the roots. Figure 1, c, gives a representation of six feeding holes made at a distance not more than one-fourth of an inch apart as Mr. Hood viewed them. The common methods of attack result in a pruning of the roots, after which the severed portions rot and the remaining parts are further marred with feeding scars. At this stage the hold of the plant upon the soil is greatly weakened and it can be pulled from the ground with ease. In some instances on rec- ord the root systems were en- tirely destroyed and the rice plants floated in the water. The injuries done by the larve first cause the leaves of the rice plants to turn a pale yellow and droop, the lower blades often: resting on the water. With severe attacks some of the leaves may die. These effects in the fields become most pronounced on plants growing in depressions and low portions of the land into which the water first flowed and where it THE RICE WATER-WEEVIL. 9 stands deepest. As previously mentioned, such places are most attractive to the adults. Where the adults occur most numerously the larvee must be expected to follow in great number. In conse- quence the severity of the larval infestations is shown by a yellow cast of the leaves extending in broad streaks along dead furrows, while spots and areas of yellowish plants also become visibly ap- parent within the hollows and sinks of the land. These signs of injury have appeared in fields after 20 days of flooding, but ordi- narily the larve do not become numerous enough to cause much damage until the water has stood for at least a month. If many of the roots are cut off from a plant (fig. 1, e), its growth is stunted, but as the growing rice plant possesses a strong vital power new roots are put out to replace the ones destroyed, and on the cessa- tion of attacks the injured plant revives, or is said to “ recover,” and makes a belated growth, usually resulting in late heading. Much of the unequal growth of the plants in the fields, as well as the irreg- ular maturity of heads, is accountable to the detrimental effects of the larval attacks. Harvesting must necessarily be delayed until all the heads are ripe, thus involving the risk of loss to the normal yield from storms or other causes. : Furthermore, the attacks on the roots of tender young plants pre- vent proper stooling or production of stems. In comparison with normal plants, often less than half as many stems grow from a stool that has suffered damage. Shortage of heads-is therefore caused by the failure of badly injured plants to produce a full quota of stems. The fact that the larvee are largely responsible for a great deficiency of yield in this respect will impress a comprehension of the amount of loss caused by the insect. DEVELOPMENT OF STAGES. The length of time required for the development of the weevil from a freshly laid egg has been estimated by Mr. Hood to be about 10 weeks. Judging from the first occurrence of larvee in fields after 1 to 3 weeks of flooding, a period not to exceed 10 days would probably be ample time for an egg to hatch subsequent to deposition. Development is hastened with the advance of hot weather when the water and soil become warm. Usually not until about six or seven weeks after fiooding do many of the larve attain full growth and appear ready for pupation, although pupe have been found in a field that at the time had been irrigated for only five weeks. In prepara- tion for the pupal stage the larva forms a cell in the mud among the roots or at the tip of one, and Mr. Hood has asserted that the pupa passes two or three weeks before it matures and the emergence of the adult takes place. 10 THE RICE WATER-WEEVIL. ng With the aim of working out the details of development of the larval and pupal stages, a number of larve were placed on the roots of young rice plants, each of which was set in water within a glass tube, the tubes being simply stood in a holder. Attempts to carry through the development of pups from larve when subjected to con- stant exposure to light proved only partially successful, but better progress, although still lacking completeness, was made after shield- ing the tubes from light and supplying a small amount of earth with the roots and water. SEASONAL HISTORY AND GENERATIONS. _ Adults as well as partially and full grown larve, and also without doubt the pups, occur in many fields up to the time of draining for harvest. With late crops in the coast region, however, and in the fields of Arkansas on account of the difference of the season in that State, the number of weevils in all these stages diminishes about the time when the plants begin to head in the latter part of August. Weevils found in fields after the drawing off of water to permit harvesting are apt to be freshly emerged individuals of a new gen- eration. From a collection of infested roots obtained by Mr. Pierce at Beaumont, Tex., June 28, 1904, adults emerged as early as July 2 following. In case such early emerged weevils breed at once, they have a chance to produce a second generation in a season, provided they find late flooded fields or suitable water holes. At Stuttgart, Ark., on September 12, Mr. Hood found roots of rice infested by a few larve which he regarded as representatives of a second genera- tion. The last larva found by the writer during his stay at Crow- ley, La., was taken September 25. While the weevils that emerge in July possibly lay eggs for a second generation, the species is prin- cipally propagated in one yearly generation. In the spring, before many of the rice fields were flooded, Mr. Hood collected adults on grasses and red rice growing in ditches and other places containing water. Since the weevils have not been known to breed in such places until the soil and water become sufficiently warm, at which time the flooding of rice fields is well under way, the deduc- tion is made that low temperatures up to this time exert a restrictive influence upon breeding. Examination of roots of red rice and other plants growing in a constantly flooded ditch at Crowley, La., on October 3, failed to dis- close any evidences of infestation at the time. These results show conclusively that the weevil does not breed at this time of year even in most favorable situations. Not only were the adults absent, but the lack of feeding scars on the leaves denoted that they had not visited there for some time. 11 THE RICE WATER-WEEVIL. The fact that adults live throughout the greater part of the season has been demonstrated several times. In an experiment with speci- mens collected at Mackay, Tex., April 5, 1904, Mr. W. W. Yothers succeeded in keeping the weevils alive by furnishing grass for food until after the middle of July. Weevils confined on rice plants by Mr. Hood at Crowley, La., July 18, lived later than the middle of September, and the writer has made a corresponding record. cover- ing a period from July 11 to September 21. The common absence if not scarcity of fresh signs of feeding by _adults late in the season or at the time when the new generation of weevils is expected to emerge throws much doubt on the question of their taking any food then. At least they do not remain long on the plants, and the few feeding scars that may appear to have originated at the time are likely produced by lngering adults of the old gen- eration. A yearly overlapping of generations in the adult stage evi- dently occurs. Few specimens that might be regarded as freshly emerged weevils have been found in the fields. These were taken by Mr. Hood, hiding in the cracks of the ground after the water had been drained from the field for harvesting. Possibly some of these weevils stray to electric lights at night, my last capture of a weevil being made on the night of September 20. Ifa new generation of weevils occurs no evidence of it has been found. The question is, What be- comes of them until they go into hibernation ? HIBERNATION.* During the fall and water of 1910 Mr. Hood made examinations of various places which might serve as hibernating quarters. The materials examined included rice stubble, loose dirt in the fields, strawstacks (both old and new). grass and other vegetable matter along levees, and Spanish moss. No weevils were found hibernating except in the Spanish moss, which, however, afforded an excellent shelter, as the following tabulated observations made at Crowley, La., will show: Observations on the places of hibernation of the rice water-.weevil. | F Estimated Nios pisiance | Height Number | numberof Date of examination. Peaniined MGReSE | above of weevils} weeviis "| vice fiela, | SrOund. | found. per ton | ot moss. 1910. Pounds. Mile Feet. | (OCs OE AER ASA Rhoe Sec He BROSEO RS Be caam seer if (?) 6 | 18 36, 000 INOW; glORE cence cases os See eee tee i ese 1 0. 25 10 21 28, 000 NOV C28 see cu cece wate ee eeewcawe scceteses 13 38 6 a 4, 920 INOW SOc cues esa eee eas see eee 12 50 6 1 1, 454 LD YG GSB leap pe mes Se cee ee 13 50 6 2 2, 666 WeC: Qi mars as stas os Sede t aos ae 13 25 6 45 60, 000 WO CS Deri e wap sle sate Seine caaisisis. cei 13 325) 6 28 34, 460 1 With the exception of a few remarks, all of the notes on hibernation of the weevils must be credited to Mr. Hood, who has made the most extensive investigations in regard to the subject. 2300 yards (0.17 mile). 12 THE RICE WATER-WEEVIL. As indicated by the preceding table, several thousand weevils may hibernate in the moss on a single tree. The appearance of large numbers of weevils in rice fields when they are first flooded has led to the opinion that the pest completes one generation on host plants other than rice before this time. But as already pointed out, no evidence has been secured that will sustain this view. Abundance of the weevils is probably due to their successful survival through the winter and emergence from hibernation. One reference in literature mentions the occurrence of adults “ in wintertime under old leaves and other shelter in drier places near the swamps.” The finding of one adult in litter beneath rich stubble is recorded by Mr. D. L. Van Dine as the result of searching for half of a day at Stewart, Tex., on October 28, 1909. Entrance into hiber- nation is probably not begun much before the time when the nights are cold enough for frost. Not a single weevil could be found by the writer in a collection of Spanish moss obtained on September 29, at Crowley, La., and in the preceding spring after the first weevils appeared Mr. Hood was unable to find any specimens remaining in the moss. NATURAL ENEMIES. Besides birds no enemy is known to feed on the mature weevils, although the snakes and frogs which frequent the fields probably do so. Bird droppings found by Mr. Hood in a rice field at Stutt- gart, Ark., on September 12 consisted largely of insect remains, those of the rice water-weevil being the most abundant. However, two perfect specimens of the weevil were removed from the droppings and one was found to be alive. According to records in the Biological Survey, this weevil is eaten by the long-billed marsh wren (7'edma- todytes palustris) and the mallard duck (Anas platyrhynchos). Owing to their concealment in mud the larva and pupa are secure from enemies. When infested roots are pulled for examination and larvee are washed out any minnows that happen to be present in the water will greedily snap the floating bodies. Predaceous larve of water beetles, which also abound in flooded fields, struggle with one another for possession of a weevil larva. If these predators and the several kinds of rapacious water bugs were adapted for burrowing in the mud and reaching the rice roots, they would be very efficient destroyers of both weevil larve and pupe. But their habit of hunt- ing in the open spaces of water renders them of little or no service against the weevil. METHODS OF CONTROL. DRAINING OF-THE FIELDS, As pointed out in the study of the life history, the existence of the larvee and likewise the pups depends upon a saturation of the soil. THE RICE WATER-WEEVIL. 13 Tf the soil dries out after the larve have made an advance in growth, they soon die. The practice of draining fields and allowing them to dry enough to cause the death of the larve was first proposed in 1881 by Col. John Screven, a rice planter in South Carolina, and was indorsed by Dr. Howard after his investigation in the field in 1881. ‘Some of the rice growers in Louisiana and Texas have reported good results from periods of draining, while others have claimed that the plants suffered more from being deprived of water than from at- tacks. Many growers therefore advocate deep flooding of fields as the proper treatment of rice when infested by the weevil larvee. Different results of draining are mainly accountable to the extent of damage done by the larve at the time of releasing the water. When the roots have been but slightly or not yet severely attacked, draining seems to result very effectively in most cases by the reduc- tion of the number of larve to a minimum. Effectiveness depends on the length of time that plants can stand without water and not suffer from the want of it. Plants that have a fair hold of roots show no ill effects of drying spells lasting from 5 to 10 days without rain. In case of heavy rain, drying should be carried on for some days longer or until the surface of the ground forms a dry crust and begins to crack. This stage of drying has been found very effective in causing the death of larve, and the ground has still retained sufficient moisture below the surface to sustain the plants that possessed a large propertion of roots. On the other hand, when roots have become severely pruned, the plants are unable to endure draining without being further impaired. Instead, they need a plentiful supply of water in order that new roots can be put out and growth resumed. The value of draining is de-- pendent upon the enforcement of the practice at the proper time, which the grower can easily determine by making examinations of the roots. Many growers object to draining on account of the waste of water and the risk or difficulty of getting fields promptly flooded again. If fields were so arranged that water could be turned from one to another in succession or from early to late plantings, most of the water could be utilized and the saving in the cost of pumping, where this means of supply is employed, would be an item of consid- eration. Other benefits arising from changes of water will be men- tioned later. Continuance of flooding to enable plants to overcome injury by larvee, instead of taking steps to destroy the weevils, will, as Mr. Newell has inferred, probably lead to a regular increase of the number of weevils until the point is reached where the insect will make profitable rice culture impossible. Constant or extra flood- ing does not in the least inconvenience the larve, but makes condi- tions even more favorable for them. Being the most practical method of controlling the weevils, draining of fields is therefore highly im- portant. 14 THE RICE WATER-WEEVIL. RESULTS OF DRAINING. Conclusive observations upon tests of draining conducted by the writer or under his instructions during the season of 1911 are pre- sented in the following statements. At Crowley, La., on June 9, a rice grower drained some parts of his field of early planted Honduras rice in which fully one-fifth of the plants, then at a height of 15 to 1s inches, showed yellow blades. The roots had been rather severely pruned, but enough remained together with newly grown ones to permit draining with safety. As many as six and seven larve infested the roots of a stool. Reflood- ing was effected June 19, after a period of drying which had lasted nearly 10 days. Quite a noticeable difference existed between the drained and undrained rice on July 21. The plants in the drained areas had nearly all headed out uniformly, while most of the un- drained rice was behind in growth, either not having headed or hay- ing heads just formed and blooming. Regarding recovery, the owner said that the plants which grew in the fresh water after reflooding soon lost their yellow color and took on a vigorous growth of healthy green, but in the undrained parts with standing water the plants re- covered much more slowly. At harvest time the owner estimated his best yield on land that had been drained to check the weevil larvee. In the field of another grower, however, results were not so suc- cessful. These small young plants were not injured badly and showed only incipient spots and streaks of weak yellow color. This was a variety of Japan rice. The field was drained May 29 and re- flooded June 8, giving a drying of 10 days. One week after reflood- ing the plants had taken on a fresh green color, and the infestation of the most injured roots had been reduced to a minimum, as shown by the nearly normal growth. Owing evidently to a second infesta- tion, during which no draining was done, an irregular belated growth was displayed at heading time. Whether the outcome might have been worse without any draining can only be surmised. Acting under a cooperative agreement, Mr. C. G. Haskell reported some very important results of his examinations at Almyra, Ark. On draining a field July 20 he found 25 larve on the roots of 25 stools. On flooding the field July 28 he found enly two larve on the same number of roots. The result was accomplished by eight days of draining and drying.