Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices U. S. DEPARTMENT OE AGRICULTURE, BUREAU OF ENTOMOLOGY -BULLETIN No. 86. L. O. HOWARD. Entomologist and Chief of Bureau. PLANT-BUGS INJURIOUS TO COTTON BOLLS. BY A. W. MORRILL, Ph. D., Entomologist of the Arizona Horticultural Commission and of the Arizona Agricultural Experiment Station. Issued June 14, 1910. i> I B R A R y" * JUN W 1910 * S-JUill WASHINGTON: GOVERNMENT lMilNTlNT, OFFICE. 1 9 I 0. Bui. 86, Bureau of Entomology, U. S. Dept. of Agriculture. Plate I. [( s TV M V 7 Some of the More Important Plant-bugs which Attack Cotton Bolls. Fig. 1.— The conchuela (Pentatomaligata). Fig. 2.— The brown cotton-bug (Euschistus servus). Fig. 3. — The green soldier-bug (Nezara hilaris). Fig. i.—T/u/anta custator. Fig. n. — Acantho- cephala femorata. Fig. c<>ris rapidus) is sometimes present in con- siderable numbers in cotton fields where no external evidence <)( injury such as described by Professor Sanderson can he found, it seems likely that the sunken spots on the outside of the boll, resem- bling some diseased condition, are not a necessary accompaniment oi a Insect Life, Vol. III. v. 68, L890. 6 Bui. 20. o. s.. Div. Km.. I'. s. Dept. Agr., j>. 31, 1893, c Farmers' Bulletin 223, p. '-'it. L905, 16 PLANT-BUGS INJURIOUS TO COTTON BOLLS. this insect-damage (PL II, fig. 5). However, the fact that they have been produced in some cases differentiates the injury by this Capsid from that of all Pentatomids, Coreids, and Pyrrhocorids which has come under the writer's observation. Investigations during the past two years in many sections of Texas and in northern Mexico with representatives of these three last-mentioned families of Heteroptera have failed to show a direct connection between spots of any kind on the outside of the carpels of the injured bolls and the insect's punc- tures. In nearly all cotton fields bolls can be found which are marked with reddish or brownish spots (PL II, fig. 8), more frequently seen on the parts of the boll not covered by bracts, and never showing on the inside of the carpels. It is apparently an evidence of a physiolog- cal disorder of little or no consequence, but in some cases these spots have appeared to bear a relationship to the condition of the developing lock. To determine if any such relationship existed in the case of green bolls damaged by plant-bugs, 100 bolls were examined, with the following results: Average number of spots in 25 bolls with slightly stained locks 2. 24 Average number of spots in 75 bolls with badly stained locks 3 Percentage of badly stained bolls without spots 10 Percentage of slightly stained bolls without spots 46 A second lot of green bolls picked from plants on July 11, 1905, was examined and the results are here presented in tabular form. Table I. — Relation of external spots to plant-bug injury of cotton bolls. Number of external spots. Number of bolls. Number of bolls dam- aged. Number of bolls un- injured. 17 11 10 17 9 7 0 One 2 3 Total 38 33 5 The punctures may be through the spot, but this is entirely acci- dental. One boll of the above lot showing over 60 conchuela punc- tures was found to have but three small external spots, while the carpel of the lock most severely damaged was entirely free from dis- coloration. Among those examined which showed but one external spot, several were as badly damaged as any of the entire number. From the foregoing observations we may conclude that the spots here referred to with which every cotton grower is familiar do not bear a direct relation to punctures by plant-bugs, for the spots may be present on bolls which show no punctures, which in all cases are detect- able when present as hereafter described, and may be absent on badly damaged bolls. They are shown, however, to have a secondary Bui. 86, Bureau of Entomology, U. S. Dept. of Agriculture. Plate II. Effects of Plant-bug Attack on Cotton Bolls. Fig. 1.— Boll with section of carpel removed to show plant bug injury. Fig. 'J.— Portion of full- grown cotton boll, showing lock of cotton ruined by destruction of seed ai apex i>\ Thyanta CUStatOT, Fig. 8. — Lint partly removed from seeds to show discoloration by cotton stainei dercuA xittturltiix); a. Seed and attached lint from uninjured boll; b-C, same from boll dam- aged by cotton stainer, showing lint stained deepest close to seed. Fig. 4.— Decay of seeds in immature cotton boll as a result oi feeding by plant-bugs; no external evidence of injury. Pig. .">.— Exterior of cotton boll injured by Caloeorts ropidus. Fig. 6. — Cross section of immature cotton seed damaged by Pentatomid busrs. Fig. 7.— Inside of carpel of cotton boll, showing feeding punctures i>y plant-bugs. (Arrows point to punctures without proliferation.) Fig. 8. — Cotton boll showing external spots referred to on page 16. (Original.) NATURE OF INJURY. 17 relationship in that they occur with greater frequency on bolls injured by plant-bugs than on those entirely free from injury from this source. Although no external discoloration in the form of spotting of the bolls is known to result directly from the attacks of the representa- tives of the Heteropterous families thus far studied, and included in this discussion, there is frequently present more or less reliable external evidence of damage. Bolls when severely attacked by plant- bugs may flare, turn yellowish, become flaccid, and finally fall to the ground. This has been observed to take place in bolls as large as 1J inches in diameter, although it more often occurs in bolls which have attained less than one-half of the normal mature size than in larger bolls. Occasionally a deformity results from the destruction of one lock when the boll is quite small, but this frequently occurs when there is no evidence to connect the deformity with plant-bugs. In addition to these physical changes in the boll, it has been observed with several of the plant-bugs that damaged bolls may be detected in many cases by the yellowish stain produced on the bracts and carpels by the liquid excrement. INTERNAL APPEARANCE OF BOLLS DAMAGED BY PLANT-BUGS. Description. — Plant-bug injury to cotton bolls can be positively determined only by means of an internal examination. This subject was treated in the author's report0 of preliminary investigation of the conchuela in northern Mexico, but additional observations allow of a more complete consideration at this time. While these observa- tions are for the most part based on the conchuela, it has been found that the same effects result from the attacks of the other representa- tives of the Pentatomidae, as well as the representatives of Coreidse and Pyrrhocoridse upon which studies have been made. The most essential factor in determining injury to cotton bolls by these plant- bugs is the appearance of the inner side of the carpels (PL II. fig. 7), where the point of entrance of the insect's seta^ is marked by a minute dark spot surrounded by a watery or blisterlike, bright-green area, contrasting distinctly with the light, dull-greenish background. In many cases, particularly in bolls three-quarters grown or more, these blisterlike areas increase to a diameter of 4 or 5 millimeters, but in other cases, more especially in small, rapidly growing bolls, a physio- Logical reaction in the form of a proliferation of plant tissue takes place. This proliferation (PI. Ill, figs. 6-8) is of the same nature as that which results from the puncturing o( the carpels o{ the bolls bv boll weevils, described by Hunter and Hinds in a previous bulletin of o Bui. 51, Bur. Ent., U. 8. Dept. Agr., pp. 29-30, L905. 22348— Bull. 86—10 2 18 PLANT-BUGS INJURIOUS TO COTTON BOLLS. this Bureau. a That this abnormal growth may be caused by the punctures of Heteropterous insects was first pointed out by the author in his report of preliminary investigations of the conchuela.6 Since then, in the course of more extended investigations of this and other Heteropterous cotton pests, incidental observations on this point have been made by the writer, a summary of which will be found in a publication by Dr. W. E. Hinds dealing with the relation of the proliferation to the cotton boll weevil. c When caused by the boll weevil, this growth can be easily distinguished from that caused by Heteropterous insects by the distinct open puncture which extends through from the outside of the carpel. The entire inner side of the carpels of bolls damaged by plant-bugs is frequently found on exami- nation to present a rough or papulous surface due to the fact that the punctures are so close to one another that the proliferous growths merge together. At Tlahualilo, Durango, Mex., on July 17, 1905, an examination of 100 injured bolls revealing over 4,000 punctures by plant-bugs (practically all by Pentatoma ligata) developed the fact that 34 per cent of the punctures had resulted in proliferation. On November 1, 1905, an examination of 25 bolls at Dallas, Tex., from a field where three species of Pentatomidse (Nezara hilaris, Euschistus servus, and Thyanta custator) occurred in considerable numbers, gave the following results in regard to proliferation, using the lock as the unit: Table II. — Proliferation on mside of carpels rf locks fed upon by Pentatomids. Size of bolls (diameter). Locks. Number. Number Per cent showing 1 showing prolifera- prolifera- tion, tion. Destroyed by plant- bugs. Slightly injured. Unin- jured. Inches, i-i 1-1* Total 60 40 42 70 11 27 39 8 3 3 0 a2 100 53 47 6 2 a Inside carpels showing three and four punctures, respectively— no apparent injury. The objective point of the attack by insects investigated is the seed, which they are able to reach with little difficulty by means of the threadlike organs of their mouth-parts, except in large, nearly mature bolls which are protected by the resistance offered by the lint. Except in the larger sized bolls, therefore, a blisterlike spot or prolif- a Bul. 51, Bur. Ent., U. S. Dept. Agr., 1905. 6 Bul. 54, Bur. Ent,, U. S. Dept. Agr., p. 29, 1905. c Bul. 59, Bur. Ent., U. S. Dept. Agr., p. 29, 1906. Bui. 86, Bureau of Entomology, U. S. Dept. of Agi Plate III. CV* : 1 10 Effects of Plant-bug Attack on Cotton Bolls Parasite. Egg and Puparium of Tachinid Fi£. 1.— Locks of a cotton boll shriveled by the conchuela. Figs. 2-6. — Small Sea Island cotton bolls destroyed by the cotton Btainer. Fig. 6.— Nearly mature Sea island cotton boll opened to show damage by cotton Btainer. Pig. 7. —same with seeds and lint removed to show feeding punctures ami proliferation due to feeding by cotton stainer. Fig. 8. — Cotton boll show ing two h>ck> damaged by four and >ix feeding punctures, respectively, by the green soldier bug {Neza a '■■ - Fig. 9.— Head and thorax of the conchuela. Bhowing eurur of Tachinid parasite, Qymnosoma Juligtnosa, attached to side of {>rothorax at left. Fij,r. 10.— i'uparium of Tachinid parasite, (■.'. fvMginosa. (Original. ) Bui. 86, Bureau of Entomology, U. S. Dept. of Agriculture. Plate IV. A Cotton Plant Showing the Bolls Injured by the Conchuela. The cotton plant shown bears Til bolls, all lmt 10 of which have been destroyed by thi^ insect. (Original.) NATURE OF INJURY. 19 eration on the inner side of the carpel, such as has been described, indicates an injury to the seed or discoloration of the lint directly opposite. When a seed of a rapidly growing boll is fed upon at first the stimulation, probably partly mechanical and partly due to salivary fluids of the bug, causes an increase in the flow of sap to the injured seed, causing a characteristic watery appearance. The seed after- wards gradually becomes discolored (PL II, figs. 4,6) and proliferous tissue is extruded from it in some cases. Punctures near the tip of the lock are most effective in destructiveness ; in one case (PI. Ill, fig. 8) 4, 6, 16, and 10 punctures per lock, respectively, were found to have produced proliferation from the seed nearest the tip of the boll in each lock and would have prevented the opening out of the cotton if it had been allowed to mature. This is equivalent to complete destruction of the boll. The lint surrounding the point where the insect's mouth-parts enter turns yellowish, and, if the injury is severe, finally becomes a dirty brown and decays (PI. II, figs. 1, 2; PI. Ill, figs. 1-8), which probably is the condition Glover referred to as "the rot." As the great majority of the punctures are made on the outer half of the bolls, it is there that staining is most frequently found. In general bolls damaged by plant-bugs when open (PI. Ill, figs. 1-5; PI. IV) are characterized by shriveled locks and only partial spreading of the carpels. The entire lock may become a brownish shriveled mass or the shriveling may be confined to the outer tip. Again, locks may be perfect except for a small stained patch of lint, which, however, might offset the value of the unstained product. Seeds in nearly mature bolls may be destroyed without the surround- ing lint becoming badly stained. Consequently where Heteropterous cotton pests are abundant, there is a reduction in the percentage of seed capable of germinating. This phase of the subject of plant-bug damage has received no especial attention. Proof that described injury is due to plant-bugs. — The evidence that plant-bugs cause injury such as described above amounts to positive proof. Sufficient evidence was given by the author in a previous report and, although much more might be added, it is unnecessary to more than summarize the facts there presented: 1. In a field where the number of conchuelas averaged about 1 5 per acre and the number of other plant-bugs was a negligible quantity. a specimen of the species named (Pentatoma ligaia Say) was known to have fed on a single boll for over 36 hours. After several days, during which no bugs were found on this plant, the 15 bolls found on this plant were cut open and examined, with the result that only the one upon which the insect was known to have fed showed the injury described. 2Q PLANT-BUGS INJURIOUS TO COTTON BOLLS. 2. In the same field two plants upon which 4 and 3 adult conchuelas, respectively, were found, neighboring plants in all directions, being free from the pest at the time, were found to be injured to the extent of 7 bolls out of 15 examined, and 18 bolls out of 20 examined, respec- tively, while as a check the bolls on the next adjacent plant in the row to each of the foregoing were examined and but 3 injured bolls were found out of a total of over 30. 3. The injury to the bolls which has been described as due to plant- bugs was invariably found in sections of a cotton plantation com- prising 27,000 acres, where the conchuela was also found; but in a section where no plant-bugs could be found, although careful search was made for them, no injury of this kind was observed. 4. Cage tests, consisting in the confinement of several adult con- chuelas on two plants in a field where no plant-bugs of any kind could be found and where an examination of many bolls indicated entire absence of the supposed plant-bug injury, resulted in 20 bolls of a total of 34 on the caged plants showing the injury a few days later when an examination was made. AMOUNT OF DAMAGE TO COTTON BY PLANT-BUGS. It is very probable that each year since cotton has been grown in this country certain localities have suffered from injuries by plant- bugs to the cotton bolls. The cotton stainer (Dysdercus suturellus) for many years has been the most serious enemy with which the grow- ers of Sea Island cotton in Florida have had to contend, and the same pest Mr. Schwarz in 1879 (1. c.) declared to be the most formidable enemy of cotton culture in the Bahamas, making questionable the possibility of continued cotton growing on those islands. Professor Sanderson's reference to the damage by the leaf-bug (Calocoris rapi- dus) shows this insect to be capable of considerable destruction to cotton bolls, although no estimate of the amount destroyed has been made. In the Laguna District of Mexico — the leading cotton-growing sec- tion of that Republic — the conchuela accompanied by related pests of less frequent occurrence has been more or less destructive to cotton during the past few years. A specimen of the insect named was sent to this Bureau in August, 1902, from Mexico, by Dr. A. Duges with the note that it was injurious to cotton at San Pedro de la Colonia, Coahuila, Mexico. In 1903 the same pest attracted considerable attention on account of its unusual abundance in the cotton fields of the Laguna District, particularly those near Tlahualilo, a settlement located in the State of Durango about 50 miles from San Pedro de la Colonia. After investigation by the author it was conservatively AMOUNT OF DAMAGE TO COTTON BV PLANT-BUG 21 estimated that the damage to the crop for the season 1903-4 was between 10 and 15 per cent. This loss on the one plantation accord- ing to this estimate was between 1,200 and 1,500 bales. A study was made of the losses occasioned by these pests in 1905 on the above-mentioned plantation, and the results in detail are considered under the subject of " Destructiveness " of the conchuela. Briefly, this damage on the entire plantation approximated between 5 and 10 per cent, and for one section of 120 acres where the bugs had been most abundant, the destruction as estimated December 4-6, 1905, amounted to 30 per cent of all bolls, including unopened bolls, and 41 per cent of all bolls open at that time. In this country damage by plant-bugs, with the exception of that by the cotton stainer, has never attracted so much attention as has that by the conchuela in Mexico. Nevertheless, after the character- istics of plant-bug injury have been brought to one's attention, a per- son is generally impressed with the frequency with which it is met in the cotton fields. The appearance of the conchuela as an enemy of miscellaneous crops in western Texas, near Barstow, in 1905 led to an investigation, in connection with which estimates were made of the damage of the insect to cotton in that locality. As has been stated in a paper dealing with this outbreak, it was estimated that about 10 per cent of the cotton was destroyed near Barstow in 1905. In one field on August 11, 30 per cent of the bolls had been ruined, but the disappearance of the majority of the insects and the continuance of the fruiting of the plants resulted in the percentage of injury being ultimately reduced by one-half. Plant-bugs occur in cotton fields in the northern half of the State of Texas in much greater abundance than in the southern half, and in 1905, special attention having been given for the first time to the occurrence of plant-bug injuries, it was evident that the aggregate losses from this cause must have been large. It is impossible to ap- proximate the total loss chargeable to the work of plant-bugs in 1905, but it is almost certain that for northern Texas an estimate of 4 or 5 per cent of all bolls is not too high. As a matter of fact the writer's personal examinations in many cotton fields in the section of Texas referred to indicated that this estimate is much too low. Plant- bugs (Pentatomids) were especially abundant near one corner of a 60- acre cotton field at Dallas, Tex., used for experimental purposes by this Bureau. On September 9, 1905, 43 green cotton bolls were picked at random in the section of the field referred to, and o( these 29, or 68 per cent, were damaged by the bugs, about 50 per cent being ruined and the others showing badly stained lint. On November 4, 25 bolls were picked at random in a section of the field where these 22 PLANT-BUGS INJURIOUS TO COTTON BOLLS, insects had been abundant, and the results of the examination are summarized in the following table : Table III. — Injury by plant-bugs to cotton bolls. BOLLS. Diameter. Number. Uninjured. Slightly injured. Inches. i- J 15 10 1 0 b'2 1-1} Total 25 2 2 LOCKS. Number. Destroyed by bugs. Slightly injured by bugs. Destroyed by weevils. Uninjured. GO 40 45 15 8 11 1 2 6 12 100 60 19 3 18 ' FEEDING PUNCTURES. Total. Number in Number in Number in destroyed slightly in- uninjured locks. jured locks. locks. Average per destroyed lock. Average per slightly in- jured lock. Average per uninjured lock. Average per destroyed boll. 366 300 346 20 186 i 82 0 32 7.7 12.4 2.5 7.0 0 2. 6 26 30 666 532 102 32 8.9 5.3 1.8 28 Destroyed bolls. Slightly injured bolls. - Destroyed locks. Slightly injured locks. Unin- jured locks. Maximum Minimum number of number of punctures, punctures. Maximum number of punctures. Minimum number of punctures. Maxi- mum number of punc- tures. 20 Mini- mum number of punc- tures. Maxi- mum number of punc- tures. Mini- mum number of punc- tures. Maxi- mum number of punc- tures. 69 7 1 5 1 81 15 55 16 22 4 16 1 10 a Two locks destroyed by boll weevil larvae. b Including one boll with 55 feeding punctures by bugs, lint only slightly stained at time of examination. The data given in Table III will serve as a guide to the relation between plant-bug punctures and the damage which results, as well as an example of a condition which may be occasionally met with in cotton fields of northern Texas where large numbers of plant-bugs are concentrated in small areas. Fortunately such occurrences are not common and are generally restricted to small areas where the surroundings are favorable for the breeding of the bugs in large numbers. THE < OXCFIUELA. 23 Due credit has not hitherto been given plant-bugs for their part in diminishing the yield of cotton and lowering the quality of the lint. This failure to connect the injury with the cause, as has been pointed out, is largely due to a lack of understanding of the nature of the injury, as well as to the fact that plant-bugs have always been found in cotton fields and except in rare instances no good criterion for judging the amount of loss has been afforded. Field agents of this Bureau, engaged in investigating cotton insects, frequently have met cotton growers in northern Texas who ascribed the shriveled condition of the locks of bolls damaged by these bugs to dry weather. In Florida some cotton growers have explained damage of tins same kind as due to the prevalence of wet weather. Summarily it may be stated that locally plant-bugs frequently cause large losses and throughout large sections of the cotton States cause small but appreciable losses which it is important should be determined in a less cursory manner than heretofore. PLANT-BUGS AS DISSEMINATORS OF PLANT DISEASES. Various plant-bugs have been suspected of transmitting fungous and bacterial diseases of plants, but as yet there appears to have been no careful investigation of this matter. That the transmission of the spores of cotton boll anthracnose (Colletotriclium gossypii Southworth) by plant-bugs from one boll to another is possible requires no demonstration. An investigator would rather be con- cerned with the extent to which these cotton-frequenting insects are responsible for the spread of the disease. It is highly probable that the bacillus of the cotton boll "rot" (Bacillus gossypiaus Stedman) may be disseminated to a greater or less extent by means of plant- bugs whose mouth setae would furnish a means of direct entrance of the organism to the interior of the boll. The entire subject is one which offers a field for interesting and valuable research, but for the present no estimate can be made of the damage to cotton indirectly caused by plant-bugs through dissemination of pathogenic fungi and bacteria. THE CONCHTJELA. I Pentatoma ligata Say.) (PI. I. fig. l.) HISTORY. The conchuela ° was described in 1831, but first became known as an insect of economic importance when, in August, L902, specimens were received from a correspondent of the Bureau of Entomology, " This is the common name used for this insect by the natives of the Lacuna Dis- trict of Mexico. It is a Spanish won! meaning "little shell" and is based on a fancied resemblance to a shell. 24 PLANT-BUGS INJURIOUS TO COTTON BOLLS. with the note that the species was injuring cotton in the Laguna District of Mexico at San Pedro de la Colonia, State of Coahuila. In March, 1904, the author was directed by the Entomologist to in- vestigate a reported partial destruction of the cotton crop by an un- known pest in the Laguna District of Mexico. The specific report emanated from a large plantation of between 25,000 and 30,000 acres of cultivated land located in the northern portion of the Laguna District, the headquarters being at Tlahualilo, State of Durango. At the season of the year when the first visit was made, although the cotton stalks were still standing in the fields, it was impossible to establish positively the relationship between the conchuela and the large number of ruined bolls present everywhere on the plantation. The second visit to Tlahualilo from August 30 to September 8, 1904, resulted in this point being definitely determined as well as in the procuring of considerable information concerning the insect and its work. The details of these preliminary investigations were reported on in a previous bulletin of this Bureau.0 The investigations were continued in 1905 at Tlahualilo, where the author of this report spent the month of July and a week in the early part of December. The conchuela has recently become known as a pest in western Texas, where, in 1904 and 1905, near Barstow, it occasioned con- siderable loss to seed crops of alfalfa, and in the latter season proved? in addition, its destructiveness to miscellaneous crops, including peaches, grapes, peas, and other garden products. The report of the investigation of this unexpected outbreak has been published under a separate title.6 DISTRIBUTION. The distribution of Pentatoma ligata is a wide one, the species occurring rarely in the eastern half of the United States, and with much more frequency in the arid and semiarid regions of the Western States and Mexico. It is probably of considerable significance that hitherto localities where this species has been found to occur in large numbers have been situated in the Lower Sonoran faunal region of the Lower Austral zone. In Texas miscellaneous collections for three years by members of the Bureau of Entomology engaged in cotton boll weevil investigations have not included a single specimen of Pentatoma ligata taken east of the semiarid region or approximately the ninety-eighth degree of longitude. A single specimen in the collection at the office of the Texas state entomologist bears the label Beeville, Tex., which is situated between the ninety-seventh and the ninety-eighth degrees of longitude and is the easternmost a Bui. 54, Bur. Ent., U. S. Dept. Agr., pp. 18-34, 1905. 6 Bui. 64, Pt. I, Bur. Ent., U. S. Dept. Agr., 1907. THE CONCHUELA. 25 locality in Texas from which the writer has seen a specimen of the species. West of the ninety-eighth degree of longitude specimens have been collected at the following points and elevations in the State of Texas: San Diego, 300 feet; Abilene, 1,700 feet; Barstow, 2,500 feet; Llano, 1,000 feet; San Angelo, 1,800 feet; San Antonio, 675 feet; Clarendon, 2,700 feet. The known Mexican localities where the species has been collected, with their elevations, are: San Pedro de la Colonia, Coahuila, 3,600 feet; Tlahualilo, Durango, 3,700 feet. FOOD PLANTS. Like most other plant-feeding Pentatomids whose habits are known, the conchuela has a wide range of food plants and shows a decided preference for fruits and seeds. In Texas and Mexico its principal food in uncultivated regions is the bean of the mesquite (Prosopis sp.) and the berry of a common wild solarium (Solarium elseagnifolium), known among the natives of Mexico as "trompillo." Of these two the former seems to be preferred according to observa- tions in northern Mexico where the two food plants grow together on the arid plateaus. Records of other wild food plants of the species, with the observer and locality, are as follows: Spanish bayonet or bear grass (Yucca sp.), Barstow, Tex., J. C. Crawford; wild currant (Riles sp.), San Antonio, Tex., W. E. Hinds and J. C. Crawford; sage, Clarendon, Tex., W. D. Pierce. Records of cultivated food plants, with the observer and locality, are as follows: Cotton, alfalfa, grapes, corn, chilli pepper, and tomato, Tlahualilo, Durango, Mexico, A. W. Morrill; peaches, Barstow, Tex., J. C. Crawford; cot- ton, grapes, Milo maize, sorghum, alfalfa, peas, tomato, Barstow, Tex., Crawford and Morrill. The fact that in 1905, at Barstow, Tex., the conchuela attacked several of these crops in sufficient numbers to cause considerable damage has been referred to under the subject of the history of the species. The range of food plants which has been recorded points to the likelihood that this insect may use as a food plant almost any of our cultivated grains, fruits, and vegetables which circumstances may place in the way. DESCRIPTION. ADULTS. (PI. I. fig. I; text fig. 1.) This species belongs to the subgenus Chlorochra Stal, and in com- mon with certain other members of this group exhibits a wide varia- tion in color. The general color is usually dull olivaceous, frequently either grayish, pinkish, purplish, or greenish, and occasionally black or brown. The punctures are black or dark gray. The species is most strikingly characterized by its general dark color, with the 26 PLANT-BUGS INJURIOUS TO COTTON BOLLS. lateral margins of the thorax above and below, the basal third to two-thirds of the costal margins of the wing corium, and the tip of the ' scutellum varying in color in different specimens from pale yellow to bright crimson. In a series of 63 specimens collected at random the range in length was found to be from 12 to 16.5 mm. While in this species there was one of either sex measuring 16.5 mm., the females in general are slightly larger than the males. Among 10 specimens of each sex collected at random in a cotton field, the average length was 15.1 mm. in the case of the females and 14.1 mm. in the case of the males, the former ranging from 14 to 16.5 mm., the latter from 13 to 14.5 mm. . Fig. 1.— The conchuela (Pentatoma ligata): a, Adult bug; b, egg-mass on leaves; c, egg just before emergence of nymph; d, egg at an earlier stage of development; e, egg from side showing exit hole at the top; /, egg closed, a, b, enlarged; c-f, greatly enlarged. (Author's illustration.) EGGS. (Text fig. 1; PI. V, fig. 1.) The writer has described the egg of this species in a previous report. From the examination of 25 eggs deposited by various females the dimensions may be stated as follows: The greatest diameter of individual eggs varies from 0.95 to 1.22 mm., rarely exceeds 1.1 mm., and averages about 0.98 mm.; the height varies from 1.2 to 1.45 mm. and averages about 1.28 mm. The egg is irregularly ovoid in form. When first deposited it is pale green but the chorion soon turns white except for certain areas which are translucent and grayish in color, turning to dark gray or brown as the embryo develops. Fig. 1 .— Egg Batch of Conchuela (Pentatoma ligata\ Showing Hatched and Unhatched Eggs. Enlarged 63 Diameters. cAuthor's Illustration.) Fig. 2.— Egg Batch of Conchuela from which 32 Proctotrypid Parasites 'Telenomus ashmeadp have Emerged Enlarged 6s Diameters. (Author's Illustration.i This illustration shows three parasites, Including male and remale, ready to emerge; also an egg destroyed, probably by an ant. Till. CONCHUELA. 27 Fig. 2.— The conchuela: Nymph, first instar. Enlarged 21 diameters. (Original.) NYMPHS. Figs. 2-6.) First instar.— In the first instar the head and thorax are deep brown. The abdomen is deep slate-gray with a middorsal scries of shiny black spots, whitish at the marginal incisures between which just inside the margin of each segment is a spot of deep brown. Speci- mens in this Btage vary in length from 1 to 1.75 mm. and in width from 1 to 1.5 mm. according to individual variation and age. Second instar. — The head and thorax of the nymphs in the second instar are shiny black, the thorax being margined with yellowish or orange -red. The abdomen above is dark viola- ceous, the venter paler. There is a series of brack spots on the dorsum of the abdomen as in the first instar and a ventral series of black spots is sometimes present along middle one to each of the last four segments. The abdominal segments above and below have a yellowish or orange-red border, which narrows posteriorly. The length of second-instar nymphs varies from 1.6 to 2.5 mm., and the width from 1.3 to 2 mm. Th i rd i n sta r. — T h e nymphs in the third in- star are much like those of the second but are subject to greater vari- ation in color. There is more or less olivace- ous along the middle of the venter of the thorax. The abdomen usually has a pale violaceous ground color and dark violaceous spotting. The Neutral series of spots is usually distinct. consisting of one spot on each of the segments from the fourth to the eighth, the anterior spot being the smallest. Frequently inside the reddish border on each segment from tin1 second to the ninth is a more or less thickened crescentic black mark. Corresponding Kig. 3.— The oonchuela: Nymph, second instar ameters. i original.) Enlarged 21 di- 28 PLANT-BUGS INJURIOUS TO COTTON BOLLS. Fig. 4. — The conchuela: Nymph, third instar. Enlarged 13 diame- ters. (Original.) markings are sometimes present on the venter. The lines of the segments are usually dark in color. The length in this instar varies from 3.5 to 4 mm., and the width from 3 to 3.5 mm. Fourth instar. — The fourth instar is characterized by the first external evidence of the developing wing- pads. The ventral side of the head, and sometimes the two basal segments of the beak, are more or less oliva- ceous. The black crescentic markings inside the margin of the abdominal segments are more distinct than before. Otherwise the color corresponds very nearly with that of the third instar. The length of the fourth- instar nymph varies from 4.8 to 6.5 mm., and the width from 3.7 to 5 mm. Fifth instar. — In the last or fifth nymphal instar the head and thorax are rarely uniformly black as in the two preceding instars but are more or less oliva- ceous, with black punc- tures. The venter of the thorax has usually an olivaceous but sometimes a pale pur- plish or rosaceous ground color, with black punctures and markings. The basal segments of the legs are more or less oliva- ceous. The abdomen is colored as in the previous instars except that the ventral series of spots along the mesal line is either absent or only faintly indicated. The length of the nymphs in the fifth stage varies from 9 to 11 mm., and the width from 6 to 8 mm. Fig. 5.— The conchuela: Nymph, fourth instar. Enlarged 10 diameters. (Original.) THE CONCHUELA. 29 LIFE HISTORY. Mkthods of Study. Studies in the life history of this and other species of plant-bugs were conducted in an improvised laboratory at Tlahualilo, Durango, Mexico, during July, 1905, and at the boll weevil laboratory at Dallas, Tex., after August 5, 1905. The insects were confined in lantern chimneys covered at the top with cheese cloth held in place by rubber bands, the number of adults to a cage ranging from one to five. The adults were provided daily with freshly picked green cotton bolls until about October 1, after which fresh bolls were supplied every two days as long as any were available. Nymphs were fed upon fresh green cotton leaves or twigs, cotton bolls cut or broken in two. and imma- ture cotton seed from which the lint was first removed. R e c o r d s w e r e made at least once each day. noting deaths, eggs de- posited, time o( examination, etc. During the writer's occasional absences from the laboratory on Held work these records were made by Mr. W. W. Yothers and Mr. A. 0. Morgan. Fig. 6.— The conehuela: Nymph, fifth instar. Enlarged 6 diameters. (Original.) Adults. PERIOD BETWEEN MATURITY OF ADULTS AND BEGINNING OF EGG-LAYING. The data at hand on the length of time elapsing from the maturity of the adults to the beginning o( oviposit ion are not sufficiently extensive to permit the drawing of conclusions. Apparently the specimens upon which the data are based were influenced by the lab- oratory conditions, for the period varied in length from 23 to 95 days and averaged 45 days in the case o^ the five specimens which were reared to maturity in the laboratory during duly and August and which deposited one or more batches of eggs. Three females in addi- 30 PLANT-BUGS INJURIOUS TO COTTON BOLLS. tion to the foregoing lived deposited no eggs. 6, 34, and 125 days, respectively, but REPRODUCTION. Monthly and daily rate of oviposition and relation to temperature. — Including all the female specimens of Pentatoma ligata upon which observations were made, the average daily rate of egg production was 1.45. Omitting the month of November, during which no eggs were deposited, the rate was 1.8 per day, while up to October 1 the rate was 2.4 per day. The more important data on egg deposition are summarized in the following table : Table IV. — Rate of egg deposition of the conchuela. Lot. collected. Where collected. Total Average number of eggs deposited per Num- 1 num- ! insect per day. ber of ber of females, eggs de- posited. July. Aug. Sept. Oct. Nov. Total. A 1905. July 6-10. . . . Tlahualilo, Mexico. Aug. 1 1-12. . Barstow, Tex Sept. 12. . . .do 21 2.755 2.74 3.05 0.51 8 1 592 4. 6 .57 14 1,271 6.27 0 0 1.50 0 0 0 0 0 1.92 B... 2.5 c 5.4 D Oct. 13 . .do. . . a 10 0 . . U 1 a These insects were soft, indicating that they were newly matured. A study of the effect of temperature on egg production in the species here considered leads to the conclusion that the effective temperature as concerns egg-laying in the faunal region where these records were made, i. e., Lower Austral, is a little less than 75° F. The effect of temperature changes upon egg production is well illus- trated by the data given in the following table relating to insects of lot A referred to in Table IV: Table V. — Relation of temperature to egg-laying in. the conchuela. Period. Average NumbOT °' 1905. July 11-15 July 16-20 July 21-25 July 26-30 82.i. 67 75.3 1 11 78.1 61 THE CONCHUELA. 31 Egg-laying capacity. — A summary of the Laboratory records regarding egg-laying capacity is presented in the following table: Table VI. — Egg-laying capacity of specimens of the conchuela collected in cotton field*. Lot. When Number of collected, females. Average Maximum number of number of eggs depos- it ed per ited per female. female. 1905. A Julv 6 21 B Aug. 12 c Sept. 12 14 D Oct. 13 L0 131 321 74 . (a) 91 b 122 0 0 a No individual records kept for this lot. t> This record is for the only female specimen isolated from others of same sex. The above records are based on females collected in the field, lot A at Tlahualilo, Mexico, and the remaining lots from Barstow, Tex. In all cases it may be presumed that the specimens had deposited eggs before the records began. From the fact that few nymphs were present, while the number of adults was rapidly increasing in the field where lot A was collected, it is probable that the migrating insects consisted of males and females which had recently reached maturity in the surrounding mesquite and arrived at the cotton field as a consequence of their search for a better food supply. The status of these insects in the mesquite as hereafter described adds further evidence to the support of this supposition. If we consider, accord- ingly, that the individuals of lot A had averaged to begin egg-laying one week before the above records begin, the daily rate being the same as for the remainder of the month, the average number of -LrLr^ deposited by each female of the lot would be 150 and the maxi- mum number 340. Duration of fertility. — Four lots of insects were used in testing the duration of fertility in isolated females. The results are summar- ized as follow-: Table VII. — Duration of fertility in females of the conchuela isolated from males. Lot Xunlber When number. ^"^ isolated. -irion of first infer*:: Deposition of last fertile egg. Date. Number of days after iso- tion. Number Date. i ac- tion. 1905. 1 5 Julv 10 2 1 Julv 10 3 5 Julv 10 4 2 July 11 1905. Aug. 11 Sept. ID Aug. 1'' 39 1905. 47 Sept n Sept. 10 44 rage 54 32 PLANT-BUGS INJURIOUS TO COTTON BOLLS. Two points of importance are brought out by the data given in Table VII. First, it is evident that the duration of fertility after isolation does not cover the normal egg-laying period of the female. Second, the end of the period of fertility in the female is not well marked and a considerable period may elapse between the deposition of the first infertile egg and of the last fertile egg. PROPORTION OF SEXES. While observations on a small scale indicated a preponderance of the number of females over the number of males, the final and most conclusive observation as well as the totals show that the two sexes occur in about equal abundance. The difference in favor of the female sex shown in the totals is less than 2 per cent over an equal division, a difference which might occur in slbj arbitrarily chosen series from a large number of specimens including exactly one-half of each sex. Table VIII. — Proportion of sexes of the conchuela. When collected. Where collected. Number of males. Number of females. Total. September, 1904. . . Julv 11, 1905 Tlahualilo,Durango, Mexico. do 7 17 247 12 25 19 42 July 12, 1905 do 253 500 Total 271 290 561 LONGEVITY. Adults collected in the field. — Provided that an abundance of food is available, the length of life of the adults when protected from their natural enemies is dependent upon the season of the year in which the insects reach maturity. The following tabulations summarize the data concerning this point in the life history of the conchuela derived from the laboratory records. Table IX. — Summary of records of longevity of adults of the conchuela collected in cotton fields. Number of specimens. Where collected. When col- lected. Maximum longevity. (Days.) A verage longevity. (Days.) 8 14 5 9 6 2 0 11 Tlahualilo, Durango, Mexico Barstow, Tex 1905. July 6-10 Aug. 12 Sept. 12 Sept. 19 Oct. 13 9 142 83 29 6 91+ 6 67 + 79 "09" "c67+' 9 71 29 17 53 6 67+ 37 "9" "53+ do Clarendon, Tex a Apparently parasitized by Tachinid fly but no parasite emerged from body of supposed host. 6 In hibernation test December 1; all alive December 19; all dead March 8, 1906. c Alive January 17, 1906, in hibernation cage; dead March 8, making 98+, but to keep on same other specimens the record was included only up to December 19, 1905. THE CONCHUELA. 33 In order to show in a more graphic manner the vitality of the females collected at various times during the year, the data con- cerning that sex are arranged in the form presented below: Table X. — Longevity of adult females of tf>< conchuela collected infield. Number Number alive in sucessive months.** When collected. Y\ here collected. of speci- meDS- July. Sept. Oct. Nov. Dec. 190'). Julv iv-10. . . Tlahualilo, Durango, Mexico Barstow. Tex 21 21 20 13 4 11 5 7 1 5 10 1 2 10 0 August 11-12 68 c 14 0 September 12 September 19 October 13 do 0 o Barstow, Tex 10 rflO a Record on the first day of each month following that during which collection was made. t> Not including *> which died in less than five days after irip from Barstow to Dallas. Tex. c Not including 2 which died in less than five days after trip from Barstow to Dallas. Tex. d Hibernating alive December 19. All of the above records on the duration of adult life are incom- plete, as it was not definitely known in any case how long the insect had been in the adult stage when collected. Conditions at Tlahua- lilo indicate that the specimens collected at that point had been in the adult stage, on the average, about ten or twelve days. There were no means of judging on this point in the case of the specimens collected during August and September, but those collected on October 13 were still soft and specimens which died in transit contained no recognizable eggs; hence with little doubt this lot of specimens had matured within the week preceding their collection. Adults reared to maturity in the laboratory. — As will be explained under the subject of the molting of nymphs, imperfect or crippled adults are frequently produced in the laboratory. From the ten apparently normal adults which reached maturity in confinement the most complete records on longevity were obtained. Table XI.— Summary of records of longevity of adults of the conchuela which reached maturity in laboratory. Number of specimens. Where collected. When mature. Maximum longevity. Average longevity. 9 l 6" 1 Tlahualilo. Durango, Mexico. (), Bur. Km., V. s. Dept. Agr., \k L58, L906. 6 Records based on a recording thermometer in the room with th< 38 PLANT-BUGS INJURIOUS TO COTTON BOLLS. female brought from the field into the laboratory proved unfertilized; hence this factor should be eliminated from the laboratory records in order to make them comparable with actual field conditions. As an illustration of the mechanical prevention of hatching referred to, a conchuela in one instance deposited eggs in two layers, the nymphs in the lower layer of eggs, numbering 20, being of course unable to escape from the shells. This manner of depositing the eggs was evidently due either to interference by other specimens in the cage or to a lack of sufficient leaf-area, both of which conditions are abnormal. Occasionally eggs are deposited, both in the labora- tory and in the field, wrong side up with relation to other eggs of the batch. This also usually results in mechanical prevention of hatching and accounts for the failure to hatch of somewhat less than 1 per cent of the 942 eggs referred to above. Other eggs may fail to hatch owing to the exit hole at the top being abnormally small, as the author has observed to occur in two instances with eggs of the harle- quin cabbage bug (Murgantia Mstrionica Halm). The extent of this abnormal condition may not be noticeable, yet sufficient to prevent emergence of the nymph. Still other eggs may be abnormal in the respect that the lid which must be raised to permit the escape of the nymph is too solidly attached to the neck of the egg in proportion to the strength of the insect. EFFECT OF LOW TEMPERATURE ON VITALITY. An experiment was made to determine the extent to which de- velopment of eggs might be retarded or otherwise affected by low temperature. In this experiment 12 egg-batches comprising 288 eggs were used, all of which were deposited between August 27 and September 16 by 8 different females. Each batch of eggs was placed in an ice box within 24 hours after being deposited and kept there until November 2, with the temperature almost invariable and averaging 49° F. Upon examination it was found that the eggs had been entirely destroyed, being shriveled so that there could be no doubt of their condition. It would seem, therefore, that such long- continued low temperatures are fatal to the conchuela in the egg-stage. HATCHING. As the eggshell is nontransparent, the developing nymph is invisible up to the time of hatching. The stout spine on the egg-burster is directed at the suture between the lid and the neck of the egg at a point opposite the hinge. By pressure from below a split is made along the suture and the pale pinkish head of the nymph surmounted by the egg-burster appears beneath the partially opened lid. The integument of the insect being soft, the emergence is by slow, scarcely perceptible peristaltic movements, the egg-burster slipping over the the concb i;i;la. 39 head and along the venter as the emergence progresses. The position of the nymph in the egg is with the dorsum toward the binge of the lid. The antennae and legs are closely appressed to the body and extended directly backward. Movement of the antenna and legs begins as soon as they are free from the egg and emergence is not completed until the legs are sufficiently strong to enable the insect to cling to the egg-batch. Individual nymphs have been observed to emerge in from 12 to 15 minutes after the lid is first raised. Emer- gence of nymphs from a batch of eggs usually extends over a period of less than labours, but activities in this line as in others are largely under the influence of temperature. A record on October 10 shows a difference of 2 hours and 15 minutes between the appearance of the first nymphs and last nymphs to emerge from a batch of 13 eggs. Xy.mphs. duration" of xymphal stages. Under normal summer temperatures. — In spite of the most careful attention one can reasonably give, the death rate of Pentatomid nymphs under observation in the laboratory is very high. In no case were nymphs of the conchuela reared to maturity in the labora- tory, but the duration of the various stages was determined by more than 35 individual records. The prevailing temperature conditions seem to control the duration of the nymphal stages of these and other Pentatomids, while a lack of food supply seems to result only in either a stunted growth or death from starvation. During the months of July and August, 1905, at Tlahualilo, Durango, Mexico, and Dallas, Tex., respectively, the data summarized in the following table were obtained, being based on from 5 to 35 specimens in each instar. Table XVI. — Observations on duration of nymphal stages of the conchuela. Stage. Average Minimum Maximum duration, duration, duration. Days. Day*. First instar 4.:. 4 5 Second instar 6 7 Third instar s 10 Fourth instar S ."> 12 Fifth instar All nymphal instars It is very unlikely that the maximum duration of each stage given above would ever be equaled by a single specimen passing through the successive stages, even in the laboratory during the summer months. It is, moreover, probable that under out-of-door temperature condi- tions the average duration of all nymphal instars taken together is a few days less than the average obtained by the laboratory observations. 40 PLANT-BUGS INJURIOUS TO COTTON BOLLS. This would seem to be the natural result of the insects being fre- quently exposed to direct sunlight. The average daily mean tem- perature during July at Tlahualilo was 81.5° F., and during August at Dallas was 82.8° F., the daily mean for the 2 months averaging 82.1° F. There is considerable variation independent of tempera- ture. This is shown by specimens reared from the same egg-batch and kept in the same cage, having in every respect equally favorable opportunities for development. The range in duration of the stages becomes greater with each succeeding instar, which fact is well brought out by Table XVI. Cold as a factor in retarding development. — At an average daily mean temperature of 69.4° F., the minimum length of the second instar among three specimens of the conchuela was 19 days, the period being from September 26 to October 15. In Table XVI is included a record of 7 days as the duration of this instar in one specimen. This repre- sented the minimum length of the second instar among more than 10 specimens of the same brood. The period extended from July 20 to July 27, .the average daily mean temperature being 77.9° F. A comparison of these two records plainly shows the effect of tem- perature on the duration of nymphal stages. Still greater retarda- tion was exhibited by a lot of 31 fifth-instar nymphs of the conchuela, although the records are not as exact as those given, owing to the fact that the specimens were collected in the field and the entire length of the stage is consequently unknown. The specimens referred to were collected at Barstow, Tex., on October 13, and taken to the laboratory at Dallas, where they were confined in a wire breeding- cage out of doors, and supplied with fresh cotton bolls up to about the middle of November. From among these nymphs adults appeared on the following dates: October 17, 2; October 18, 1; October 19, 2; October 26, 3; November 3, 1. Nymphs were recorded as dead on the following dates: October 10, 5; October 14, 2; October 16, 1; October 26, 1. On December 19, 2 nymphs were still alive, although feeble and barely able to crawl, owing to lack of food. The average mean temperature at Dallas from October 15 to December 19 was 53.7° F., the October average being 62.9° F., November, 57.1° F., and up to December 19, 41° F. LENGTH OP LIFE WITHOUT FOOD. Like the adults, the nymphs of the conchuela, when deprived of food during the summer months, are short-lived. Nymphs in the first instar have been recorded as surviving as long as 5 days without food, which period is the longest ever noted under natural tempera- ture conditions in any instance during the months of July, August, and September. On August 11, 46 nymphs hatched from a batch of eggs and all but 3 of these were dead from starvation on August 14, THE CONCHUELA. 41 none surviving after the fourth day. There seems to be little or no difference in the ability of nymphs in later instars to wit hai and starva- tion, so far as observed in all cases with summer temperatures, death taking place in from 2 to 4 days. Data in connection with the retard- ing influence of cold, given in the preceding paragraph, illustrate the effect of low temperature on the length of life without food of nymphs in the fifth instar. In an ice box with an average temperature of 48.6° F., the life of a nymph of the first instar has been prolonged to nearly 40 days without food. In the brood of 24 nymphs to which this specimen belonged, all were alive on the seventeenth day after being placed in the ice box; 18 alive on the twenty-third day; 10 alive on the twenty-ninth day ; and only 1 alive on the thirty-seventh day. A third-instar nymph, robust, and apparently well fed previously, lived only 8 days in the ice box without food, the temperature as before averaging 48.6° F. As the time for molting approaches, a nymph becomes less active, ceases to feed, and shows a tendency to seclude itself where it will be less liable to interference by other individuals of the brood. A twig or other suitable object is tightly clasped, and the insect by pressure, exerted perhaps by means of air drawn into the trachea, splits the integument of the dorsum along the mesal line of the thorax, and in a line on each side of the head extending from the inner margin of the eye backward to the prothorax. The insect becomes freed from its old skin usually in the course of twenty or thirty minutes, although in one observation a conchuela in molting its fifth-instar skin required slightly over an hour. The insect as it emerges is pale pink and very soft, but gradually attains its normal color during the course of an hour. Adults remain soft to the touch for several days after molting. The molted skin which originally covered the abdomen shrivels, and, as is also the case with the integument which covered the thorax and head, only the black markings remain. HABITS. \ N MIMIS. FEEDING AM) GREGARIOUSNESS. For several hours after hatching, the young nymphs o( the con- chuela remain closely clustered either on or near by the egg-hatch. If there are any unhatched eggs in the batch, the nymphs after a few hours' quiescence begin to (vod on them, although it is probable that if such eggs contain nymphs they are dead or unable to hatch. Frequently enough food is contained in unhatched eggs o( a hatch to enable several nymphs to molt for the first time. For the most 42 PLANT-BUGS INJURIOUS TO COTTON BOLLS. part the nymphs are dependent on the juices of plants for food although eggs of their own and other species of insects are fed upon with relish wherever accident places them in their way. Except for this habit of feeding on insect eggs, the writer has never observed nymphs of the conchuela to attack living insects. In one instance, however, a nymph in the fifth instar exhibited a decided preference for ani- mal food over vegetable. This nymph was in a cage in the labora- tory with specimens of other species of Pentatomids, including a nymph in the fifth instar of Podisus lineatus H. Schf. This last- mentioned specimen died, but was not removed from the cage, and 24 hours later the nymph of the conchuela was observed feeding on the dead insect. As there was a fresh cotton boll in the cage, feeding on the dead inse:t was clearly a matter of preference. The habits of nymphs on the cotton plant are much like those of the adults, except that the nymphs are less conspicuous, frequently being entirely hidden by the bracts of the bolls. They have a well- marked gregarious tendency, especially in the first three stages, dur- ing which all the surviving nymphs of a brood are usually found on the same boll. In a field at Tlahualilo, nymphs of the fifth instar occurred in unusual abundance in a field of cotton averaging 5 or 6 bolls over 1 inch in diameter per plant. The nymphs reached the plants by crawling, and at the time of examination while less than one-fourth of the total number of bolls were infested, as a rule, each infested boll had several nymphs clustered upon it. As many as 17 fifth-instar nymphs were counted on a single boll, while frequently from 5 to 15 nymphs were found on a single boll, with the plant otherwise free from the pest. DISTANCE CAPABLE OF TRAVELING FOR FOOD. The distance which n}nnphs of the conchuela are capable of travel- ing for food proved to be a matter of considerable importance at Tlahualilo in 1905, owing to an invasion by nymphs of vineyards, gardens, and cotton fields adjoining an alfalfa field where the insects were breeding in enormous numbers. The cutting of the alfalfa removed the food supply of the insects, thereby causing a migration in search of food.a The adults distributed themselves by flight, but the migration of the nymphs was limited by their capabilities for crawling. Few of the nymphs in the first 3 instars got beyond a Migrations of this kind have not been previously unknown among the Penta- tomidae. Prof. D. A. Saunders in reporting an unusual outbreak of Uhler's green plant-bug (Pentatoma uhleri?) in South Dakota says regarding this point: "By the middle of June the bugs, being now about half-grown and their wings beginning to appear, began to migrate in great droves 'on foot' toward the cultivated fields. Mr. Senn estimates that they would make about one-half mile in a little less than a day across cultivated fields * * *." (Bui. 57, S. Dak. Exp. Sta., p. 39, Feb., 1898.) THE CONCH [TELA. 43 the limits of the alfalfa field. The fourth-instar nymphs were found in abundance on fence posts, tree trunks, rot ton plants, and weed- within 10 yards of the alfalfa field where they originated, and were scarce from 10 to 20 }~ards from this field. Nymphs in the fifth instar invaded a cotton field up to about 30 yards, in numbers estimated to average between ten and fifteen per plant; from 30 to 40 yard-. between five and ten per plant; and from 40 to 60 yards, between two and five per plant. Few, if any, attained a distance of more than 60 yards from the point of origin. In these estimates due allowance has been made for the nymphs which occurred in the field before the beginning of the migration. These records do not show the maximum distance which the nymphs are capable of crawling, for the new food supply immediately adjoined the field of original infestation. It is certain, however, that this distance is over 60 yards. Adults, fertilization". Laboratory observations show that males of the conchuela are polygamous and females polyandric. During copulation in the cot- ton fields, both insects are usually engaged in feeding on a boll or other part of the plant. Xo attempt has been made to ascertain how long a pair of the insects remain in coitu, but in 2 instances a note was made of more than one-half hour or more than 2 hours, respec- tively. With other species of Pentatomid bugs, pairs have been observed in coition for a period of several hours at a time. EGG LATINO. Place of deposition. — Eggs are deposited in batches or clusters wherever the female happens to be feeding or resting. On cotton they have been found on both upper and lower surfaces of the leaf, though more commonly on the latter, also on bracts of bolls and on stems. In a cotton field at Llano, Tex., in September. 1905, a female con- chuela was observed depositing a batch of eggs on lint in an open boll. On grape, 11 batches of eggs collected on July 12 were deposited as follows: 8 on underside of the leaves, 1 on the upper surface of the leaf, and 2 on the tendrils. Of 9 egg-batches collected on July 17, I were on the underside and 3 on the tipper surface of alfalfa leaves and 5 on the underside of a solanaceous weed, the "tronipillo" o( the natives of Mexico. At Barstow. Tex., eggs o( the conchuela with eggs of another Pentatomid which will he referred to later — Penia- totna gayi St a! — were frequently found on the seed-clusters o( alfalfa, a favorite feeding place. In captivity the females c^ the conchuela. as well as other cotton-feeding Pentatomids, deposit eggs usually on the cotton bolls supplied for food, but occasionally on paper at the bottom of the cage and on the cheese-cloth cover at the top. 44 PLANT-BUGS INJURIOUS TO COTTON BOLLS. Number of eggs per batch. — The conchuela, in common with other members of the family Pentatomidse, deposits eggs with considerable regularity in parallel rows, each egg except those in the outside rows being in contact with 6 others. The frequency with which eggs are deposited in multiples of 14 is strongly marked. A total number of 172 egg-batches of this species was deposited in the laboratory during these investigations. The total number of eggs in these batches was 4,900, or 28.4 eggs per batch. The number of eggs most frequently noted in single batches was 28, and the number ranking next in frequency was 42. The maximum number of eggs deposited in a single batch was 79. Rate of deposition of individual eggs. — The intervals between the deposition of individual eggs in a batch, with midsummer tempera- ture, varies from one minute to one and three-quarters minutes according to records made in the case of 2 females under observation while depositing eggs. The first of these specimens deposited 13 eggs in twenty minutes, 4 of which were deposited with one-and-one- half-minute intervals. The second specimen deposited 15 eggs in as many minutes. FEEDING. Part of plants preferred. — The conchuela shows a marked preference for the juices of the seeds and fruits of its food plants. In a report of preliminary investigations of this insect the writer recorded an observation regarding this preference. As no specific observation on this point has been made, it may be repeated that of 57 adults feeding on cotton plants, 43 were on bolls, 4 on leaves, and 10 on stems. The proportion feeding on bolls in this observation is less than ordinarily, as is incidentally shown by data given in another paragraph relating to proportion of time adults spent in feeding. The immature seed are the objective point of the insect's attack, as has been stated in de- scribing the nature of the plant-bug injury. Rapidly growing bolls of medium size are preferred to large, nearly mature bolls, the lint of which offers serious resistance to the entrance of the threadlike mouth setse. In connection with this preference bolls on the lower branches of the cotton plant are less subject to attack than are those growing on branches higher up. Conspicuous position when feeding. — The conchuela is by far the most conspicuous of the Pentatomids destructive to cotton bolls which are discussed in this bulletin. This is as much so on account of its selection of a feeding place as on account of its size and striking color. This characteristic is an important factor under some condi- tions in the control of the pest in cotton fields, as will be explained in discussing remedial measures. The author's outline of field work necessitated the examination of many thousand cotton plants for the purpose of counting the insects which were found on them. From THE COXCHUELA. 45 this experience it is certain that in the cotton fields in clear summer weather fully 90 per cent of the conchuelas are visible to the observer from a standing posture and without moving any part of the plant. It was a rare occurrence, when making records of the kind indicated, that any additional specimens of these insects were found by using the hands to open up the plant. Only a few instances have been observed where the adult conchuela has been entirely or almost en- tirely hidden by the bracts of the cotton boll on which it was feeding. When feeding on a boll these insects generally occupy a position on the upper half. When resting, during bright sunlight, they are com- monly observed in a conspicuous position on the cotton boll or on the upper surface of the leaves. The resting in the sun is usually observed during the forenoon. Proportion of time adults spend in feeding. — In the determination of the amount of damage an individual conchuela is capable of inflicting in a cotton field it is important to know what part of its time it is engaged in feeding on cotton bolls. Observations were conducted both in the laboratory and in the field, and the results are summarized in the following tables: Table XVII. — Feeding records on the conchuela in the field, Tlahualilo, Durango, Mexico, July 22, 1905. Hours of observation. Number of eon- X umber of con- X umber of ob- ;h„plas fpPfw chuelas crawl- Per cent feed- servations. c "fi^An, g ing or resting ing on bolls. on mmjs. on plants. 9 a. m. to 12 m lp. m. to 5.30 p. m Summary for dav 251 311 142 51 109 15 193 124 Table XVIII. — Laboratory feeding records on the coyichuela. Lot A." Si et I. Tla- hualilo, Durango, Mexico, July tO-tty 1905. Hours of observation. X umber of ob- servations. Xumber of con- Number of con- chuelas feeding on bolls. chuelas not feeding. Per cent feeding. fi.30a. m. to 8.30 a. m. 9 a. m. to 12 m 1 p. m. to 5 p. in 5.31) p. in. to 7 p. in . . . 8 p. m. to 10 p. m 115 72.4 a a a Table XIX. — Laboratory feeding records o)i the conchuela. Lot A. > i II. Pallas. Tex., Septeml Hours of observation. Number of ob- servations. Number of con- Number of con- chuelas feeding chuelas not on 1k)11s. feeding. Per cent fee 1 6 a. m. to 12 m 47 24 -'! 8 9 15 15 17 1p.m. to 6 p. in 7 p. in. to 10 p. m « Collected in cotton fields in Tlahualilo between July 6 and 10. 46 PLANT-BUGS INJURIOUS TO COTTON BOLLS. Table XX. — Summary of laboratory feeding records on the conchuela, Lot A. Place. Time. Per cent feed- ing in daylight. Per cent feed- ing at night. Per cent feed- ing, day and night. Tlahualilo, Durango, Mexico Dallas, Tex Julv 20-22,1905 Sept. 4-8, 1905 59.4 27.2 89.8 62.5 74.6 A comparison of Tables XVII and XVIII shows a close corre- spondence between the laboratory and field observations on the amount of time the adults spend in feeding during daylight. The fact that in the field the conchuela feeds almost constantly after sun- set has already been recorded.0 We may safely assume that the adults feed for fully as large a percentage of the nighttime in the field as in the laboratory. Considering, therefore, that 90 per cent of the night (Table XVIII), and 66 per cent of the day, is spent in feeding, the percentage of the calendar day spent in feeding at the times and places of these observations was approximately 78. Table XX shows a difference between the same lot of insects which is probably attributable to the difference in age of the speci- mens. Difference in temperature could have had no appreciable effect as it was slight, the average daily mean at Tlahualilo on the days of the observations being 76° F. and at Dallas 79° F. Method of attack. — For locating the position for piercing the carpel of a cotton boll the conchuela makes use of its antennae and tip of the rostrum. As in other Heteroptera, the rostrum is used only as a guide for the threadlike setae and is never forced into the object upon which the insect may feed. As the setae sink into the boll the rostrum bends at the joint between the first and second segments, being directed backward. The setse at the same time are freed from the rostral groove of the basal two segments, and as these two seg- ments fold together, this allows a greater depth of penetration. Next, the apical or fourth segment is bent or folded back leaving the setse in the rostral groove only at the angle between the third and fourth segments. In this position the rostrum forms a letter "Z./' the upper angle representing the joint between the second and third and the lower angle the joint between the third and fourth segments. Feeding may be continued with the rostrum in this position or the rostrum may be freed entirely from the setae and directed straight back along the middle of the venter in the usual position it occupies when the insect is resting or crawling. The insect may therefore use practically the entire length of the setae to penetrate through the carpel and the developing lint to the cotton seed. This length is about one-fourth of an inch. When feeding, the bug alternately a Bui. 54, Bur. Ent., U. S. Dept. Agr., p. 26, 1905. THE CONCHUELA. 47 raises and lowers its head. After withdrawing the setae from the boll, a downward stroke of one of the fore tibiae places them in the rostral groove, each tibia for this object being provided with a short spine located on its inner side slightly beyond the middle. Miscellaneous observations on feeding habits. — Twenty-six observa- tions gave 20 minutes as the average time the adults fed through one puncture in a cotton boll. The maximum length of time in these observations was 1 hour and 30 minutes. In his report of prelimi- nary investigations a on the conchuela the author presented his observations on the length of time adults remain on a single boll and on a single plant as follows: "One adult under observation in the field visited 4 bolls, 2 on each of 2 plants in 2 days, and remained for over 36 hours on the last of the 4 bolls. Another adult bug remained on the same boll for 2f days. Three remained on the same boll for over 30 hours and 3 others were found on the same plant 30 hours after they were first recorded. In none of these cases was it known how long the insects had been on these plants previous to their first being noted." Abnormal predaceous and cannibalistic habits. — Starving adult con- chuelas confined with live caterpillars of the bollworm (Heliothis obsoleta Fab.) and the cotton boll cutworm (Prodenia orniihogaUi Guen.) failed to exhibit any indication of carnivorous habits. Dead or dying insects, however, are not always refused and are sometimes fed upon by adults as well as by nymphs in preference to cotton bolls. (See feeding habits of nymphs, pp. 41-42.) On a few occasions where 2 or more adults have been confined together in breeding cages, dead or dying specimens have been fed upon by the survivors of the lot. All evidence at hand goes to show that in the field the adult conchuelas are entirely phytophagous. GREC.ARIOUSNESS. The gregarious habit exhibited by the conchuela, like its habit of occupying a conspicuous position on the plant, is of considerable importance in its control. The author has previously noted6 this striking feature, basing the records on observations made at a season of the year when these insects were comparatively scarce. Between August 31 and September (), 1904, in a selected section of the cotton fields at Tlahualilo, 34 adults were collected on 16 plants, although the insects were so few that but 5 or 6 plant- out of 100 were found to be infested. In July. 1905, 2 other species of Pentatomids (Pentatoma sayi Stal and Thyarda perditor Fab.) were found associated with the conchuela and occurring in moderate abundance on the "Bui. 5-t. Bur. Km.. V . s. Dept. A-r.. p. 26, L905. 48 PLANT-BUGS INJURIOUS TO COTTON BOLLS. cotton plants. Field observations showed that whatever the nature of the attraction which is the basis of the occurrence, it is operative between the different species of Pentatomids as well as between individuals of the same species. As a result of this gregarious tendency it was found that of 467 cotton plants examined on July 15, 1905, in one of the most heavily infested sections of the plantation at Tlahualilo, the infested plants, or those plants upon which there was at least 1 bug, numbered 91 and averaged about 2 bugs per plant. There were therefore about five times as many of the insects upon the infested plants as upon the average of the plants examined. A further concentration of these bugs was observed on the individual bolls. Of 100 bolls upon which one or more of the bugs was feeding 52 were found to have from 2 to 5 bugs each and 48 only 1 bug each. In all, there were 175 bugs feeding on the 100 bolls. FLIGHT. In September, 1904, conchuelas in the field showed themselves capable of only short flights, about 25 feet being the maximum dis- tance attained by any one effort observed. In July of the following year observations showed these insects to be strong fliers. Gentle winds have little effect on the flight of the insects, as they seem to fly as often against as with the wind. Many of the insects have been observed to fly as far as the eye could follow. In one instance when lost to view the specimen was about 50 feet above the ground and gradually rising higher; in another case a specimen disappeared from view without rising higher than 15 or 20 feet. The numbers of the insects in any given locality are subject to rapid changes owing to their flying propensities, but extensive migrations are always traceable to the need for a fresh food supply. SEASONAL HISTORY. INCREASE AND DECREASE IN NUMBERS DURING THE SEASON. Previous to the season of 1903, as far as can be learned, the con- chuelas attracted no particular attention as cotton pests in the Laguna district of Mexico. For the information here presented concerning the seasonal history of these insects in 1903 and 1904 the author is indebted to Mr. John Conduit, resident manager of the Tlahualilo cotton plantations, who, owing to the immense tract of cotton grown under his supervision, gives particular attention to cotton pests, and in addition to personal examinations in the fields directs the "bosses" of the various parts of the estate to send in to the office specimens of insects taken on the cotton plants, with information concerning their abundance. The bosses in their turn make examinations and send dozens of laborers into the various THE CONCHUELA. 49 subdivisions of the estate to search for any particular insect concern- ing which information may be desired at headquarters. Tin'- sys- tem made it possible to obtain accurate information concerning the abundance of the Pentatomid bugs here considered. In 1903 the conchuelas were abundant only during the month of July and reached a maximum in numbers about July 20. Their first appearance was in the outlying districts, next to the mesquite, but they soon spread all over the cotton plantation, although they were more abundant in certain parts than in others. The insects disappeared early in August and did not reappear in noticeable abundance during the season, although the cotton plants remained green until October 17, when the first frost was recorded. Although a close watch for the insect was maintained during the late spring and early summer of 1904. the first specimen was not taken in the field until July 6. During the following seven days a rapid increase in its number- was noted, and on July 17 it was observed that a marked decrease had occurred. Nowhere on the plantation were the insects as abundant as in July of the previous year, nor were they so generally distributed. On August 31' a personal examination in the cotton fields by the author showed the insects to be very scarce, although in certain sections of the plantation the open cotton bolls with stained and ruined lint gave unmistakable evidence of their greater abundance a few weeks earlier in the season. In July, 1905, a detailed numerical study was made, which verifies Mr. Conduit's general observations for the two previous seasons. While the subject of natural enemies is discussed under a separate heading, it is necessary to mention here that the abundance of the conchuela during the season is principally dependent upon the efficiency of its parasitic and predaceous enemies. Egg-laying by the average individual i- distributed over such a long period of time that it can hardly be -aid that the conchuelas naturally appear in broods. However, practically the same effect may be produced locally to a greater or lex extent by the action of natural enemies. During the first two weeks of duly adults and nymphs in all stages were found in abundance on mesquite in the uncultivated lands Burrounding the Tlahualilo Cotton Plantation. The gradual ripen- ing and drying of the beans was evidently causing a migration of the adults in search of food, many finding their way into the cotton fields. Egg-parasitism was acting as a practically complete check on further multiplication in the mesquite. In their search for food the first migrants from the mesquite settled in large numbers in sec- tions of the plantation upon which zoca or seppa (stubble) cotton was growing, and later the migrants showed a preference for the planted 22348— Bull. 86—10 1 50 PLANT-BUGS INJURIOUS TO COTTON BOLLS. cotton when the bolls became more numerous and large enough to be attractive to them. The most thorough study of the changes in the numerical status of the conchuelas during July, 1905, was made in a tdbla comprising about 120 acres and known as "Ceceda A 14" (fig. 7). The cotton in this tabla was zoca or seppa, and during the first half of July repre- Fig. 7.— Diagram of a portion of the Tlahualilo Cotton Estates. The shaded tablas are the principal ones referred to in the text. (Original.) sented conditions more attractive to the insects than did any equal area of planta (planted) cotton. Five examinations were made during July near the west end of this tabla, beginning with a row about 1 5 or 20 yards from the end and examining across the tabla, changing to next row east, every 10 plants. The results of this examination are summarized in the following table : Table XXI. — Variation in abundance of Pentatomids during July, 1905, at Tlahualilo, Durango, Mexico. When examined. Number of plants per row. Number of infested plants in 100. Adults per 100 plants. Total adult Pentato- mids per 100 plants. Number of nvmphs P. P. ligata. P. sayi. Thyantasp. ligata per 100 plants. a 1905. July 11 100 99 98 103 96 19 30 31 12 52 52 59 33 0 3 4 n 0 2 0 52 57 113 0 15... is i< 21... 2< 27 . n 33 0 29 17 0 fl 17 1 2 l5 Total Average 493 98.6 99 19.8 213 42.6 1.4 2 222 .4 44. 2 6 1.2 Small figures indicate the instars. THE COXCHUJXA. 51 Bugs were picked from the plants on this tabid between the exam- inations of July 11 and 15 and again between the examinations of July 27 and 2