Pentatomids Associated with Arizona Crops

Item Type text; Book

Authors Butler, G. D.; Werner, F. G.

Publisher College of Agriculture, University of Arizona (Tucson, AZ)

Rights Copyright © Arizona Board of Regents. The University of Arizona.

Download date 01/10/2021 17:54:31

Link to Item http://hdl.handle.net/10150/602185 TECHNICAL BULLETIN 140 APRIL 1960

PENTATOM I DS

Associated With Arizona Crops

Published by the AGRICULTURAL EXPERIMENT STATION THE UNIVERSITY OF ARIZONA, TUCSON

Seventy-Fifth Anniversary 1885 -1960 PENTATOMI DS Associated With Arizona Crops

by G. D. Butler, Jr.' and F. G. Werner' Illustrations by Marian S. Adachi2

Stink bugs are among the largest Hemiptera found on crop plants. Their characteristic triangular or shield -like shape makes most species easily recognizable in the field. The other families with similar shape are rarely seen in samples from crops. In case of doubt as to their identity, the true stink bugs, family Pentatomidae, can be recognized by the follow- ing combination of characters: antennae 5- segmented; scutellum triangular, not U- shaped; and legs without stout spines. Most of our species are brightly colored and most of them make their presence known by the emissions from the scent glands. Some experienced entomologists can detect their presence in a field by the odor alone. All can distinguish them in the sweep net. Most of our common species are defintely harmful to crops, especially seed crops, because they feed on developing seeds; at least one also feeds on vegetative growth. Podisus acutissimus is beneficial because it is predaceous, feeding on other insects. This species is not to be considered one of our most important predators, however, since it rarely occurs in such numbers as do the reduviids, nabids, etc. A considerable amount is known about the biology and nature of dam- age of our most important species. The available information is summar- ized under the species but the papers cited should also be consulted if more detail is desired. Several recent taxonomic studies have affected our species and further biological investigations will be needed where there is a chance that more than one species is reported under one name in the older literature.

1. Associate Entomologists, Department of Entomology, College of Agriculture, University of Arizona, Tucson. 2. Former Research Assistant, Department of Entomology, University of Arizona. -1 - LIFE HISTORY Stink bug eggs are deposited in masses averaging from 17 eggs in some species to 32 in others, arranged in three to five parallel rows. The eggs hatch in about five days in the summer and in from nine to 12 days in the spring and fall. About 30 to 40 days are required for the eggs to hatch and for the nymphs to mature, through five instars. Mating and egg - laying start within two weeks after the adult stage is reached. Adults live from 40 to 60 days in the spring and summer but from seven to nine months when they overwinter. The life cycle may be completed in some- what less than five weeks in the summer and from seven to nine weeks in spring and fall. Russell (1952) has studied the overwintering of the three common species in southern Arizona, Chlorochroa sayi, Thyanta pallido- virens spi- nosa (as T. custator) and Euschistus impictiventris. The following account is from this author. The winter is passed in the adult stage, some indi- viduals seeking shelter in late September and remaining there until mid - April. Most remain inactive from late December to early February. Euschis- tus and Thyanta may become active during warm days during this period but Chlorochroa is less active during the winter months. The adults usually overwinter in protected places near the soil surface, under low- growing plants and plant debris. A favored location is under the spreading branches of Australian saltbush, a common plant in cultivated parts of southern Ari- zona. He could find as many as 300 adults per square foot of soil surface under this plant. Emergence and resumption of normal activity on spring hosts begins in early March and may extend over several weeks before all the adults are active. Various weeds, such as Sisymbrium Trio, mallow and nettleleaf goosefoot, are preferred spring host plants. These weeds may be abundant in waste lands, along margins of fields, etc. Most of the females that have hibernated lay their eggs on these plants, which bloom and produce seeds from mid -January to late April or early May. Oviposition normally starts about March 15. Adults of the first generation begin to appear in April and early May. At this time the spring host plants are drying up and most of the second generation adults migrate; they turn up on small grains, sugar beet seed fields, etc. The seasonal sequence in the Salt River Valley was as follows: weeds, Feb. 15 to April 15; sugar beets, April 15 to June 15; small grains, April 15 to May 31; alfalfa, June 15 to Sept. 15; cotton, July 1 to Oct. 15; and grain sorghum, Sept. 1 to Oct. 15. In the Safford area the spring emergence is somewhat later and range plants, such as alfileria, serve as hosts for the first generation. Enormous numbers of Say stink bug adults sometimes descend on ripening grain fields in May.

RECORDS The samples reported here have been segregated from "sweepings" of crops in all major agricultural areas of the state, as detailed in the fore- word to Ariz. Agr. Exp. Sta. Tech. Bul. 132 and the introduction to Tech. Bul. 133. The crops selected for sampling were not always mature and for this reason the number of samples with stink bugs is relatively small. A crop in a purely vegetative stage may have none at all. Table I sum- marizes the collection records. Two species not taken in the sweeping -2 - Table I. The number of collections of the various species of stink bugs in 522 samples from Arizona crops made in 1954 -56.

Total Chlorochroa Chlorochroa Chlorochroa Thyanta Euschistus Podisus County Samples sayi uhleri ligata p -v. spin. impictiv. acutiss.

Yuma 76 8 4 9 22 Maricopa 187 16 9 46 19 1 Pinal 50 2 2 13 1 2 Pima 74 7 6 22 9

Sta. Cruz 21 1 5 3 1 Cochise 43 8 4 14 2 9 Graham 27 3 10

Greenlee 6 2 1 4 1 Yavapai 12 4 2 5 Gila 4 1 Mohave 7 3 Coconino 5 3 2 Navajo 4 1 2 3 Apache 6 2 2 Totals: 522 58 15 15 138 47 23 samples have been included, one because it is commonly seen on weeds and sometimes attacks crops and the other because it sometimes feeds on developing peach fruit and occasionally on alfalfa and other crops. The authors wish to acknowledge the assistance of Drs. H. H. Ruckes and R. I. Sailer for identification of critical specimens and to thank Dr. Sailer for pointing out the key characters used in segregating Chlorochroa uhleri from C. sayi. CLASSIFICATION An attempt has been made, in the key that follows, to define our species closely enough that any additional species that may be taken will be eliminated from consideration. Arizona has a rich pentatomid fauna and there is a possibility that other species than those included may be seen, particularly in weedy fields and those near the desert. Because the specimens must be examined closely when this key is used, a second key is added, this one designed for use in the field. In most cases this key should be adequate for identification. The species are considered individually in the body of the text and are arranged alphabetically, without regard to relative importance. Key to Adults 1. Bucculae distinct throughout their length, of almost uniform width, and with the first segment of the beak embedded between them. Cheeks without a lateral tooth near their tips 2 Bucculae distinct anteriorly, becoming evanescent behind, not enclosing the first segment of the beak except at its base. Second abdominal sternite with a slender median spine that projects forward to the hind coxae. Humeral angles of pronotum sharply spined. Ground color pale olive -green to pale yellow, marked with dark brown to dull red. The most heavily marked specimens have the markings dark brown, as follows: posterior portion of pronotum, behind a line connecting the humeral spines; apical half of scutellum except for a white tip and a feeble pale midline; and a narrow longitudinal band on the hemelytral membrane. Base of scutellum infuscated except for three elongate white spots. There is a small but very well defined black spot at the middle of the apical third of the corium and there are two black spots at the hind margin of the head. Lightly marked specimens retain the spot on the corium (brown instead of black) and at least a pale brown stripe on the hemelytral membrane. All the other markings may be reduced in extent and dull red in color. The white spots at the base of the scutellum may also be replaced by dull red. The hind margin of the pronotum is often pale. Length 7.5 - 10.0 mm., mean 9.0 . . (Fig. 5) Podisus acutissimtes

2. Second abdominal sternite not produced forward in a stout spine . 3 Second abdominal sternite produced forward in a stout spine, which reaches the middle of the hind coxae. Cheeks not surpassing tylus. Osteolar canal long, tapering, much surpassing the middle of its sup- porting plate. Humeral angles of pronotum obtusely produced, not spined. Color uniformly pale green except for the transparent hemely- tral membrane, very narrow yellowish to pink lateral margins on head and pronotum and narrow black posterior borders on the exposed por- tion of the abdominal tergites. Length 14 - 17.5 mm., mean 15.5 . . Acrosternum hilare -4 - E

3. Checks with side margins thin, not reflexed. Head pointing forward . 4 Cheeks with side margins thick and reflexed. Head strongly deflexed. Color brick red to yellowish, with strongly contrasting black markings, which may have bluish reflections. Length 8.5 -11 mm., mean ca. 9.5 Murgantia histrionica 4. Osteolar canal sharply defined, ending at or before the middle of its supporting plate (Figs. 9 & 10) 5 Osteolar canal continuing as a ridge that extends obliquely to the outer front angle of its supporting plate (Fig 8) 9 -5- 5. Osteolar canal short, ending in a distinct auricle, which is a lobed struc- ture with the entire distal end elevated above the supporting plate ( Fig. 10) . Humeral angles of pronotum at least acute, often with a prominent spine. Color light tan to reddish tan, with numerous small punctures slightly darker. Exposed portion of abdominal tergites marked with brown anteriorly and posteriorly, with a very narrow pale line between the dark markings of adjacent segments ( Fig. 1) Euschistus impictiventris Osteolar canal short but ending in a gradually tapered structure that grades in with the supporting plate along the anterior edge. ( Fig. 9. ) Humeri of pronotum blunt 6 6. Size very small, not over 7 mm Thyanta sp. Length at least 12 mm 7

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2 mm,

FIG. 9

7. Scutellum with no sign of three pale spots along its anterior edge. Membrane of hemelytra partly brown, especially at the base and in scattered flecks on the veins. Last abdominal sternite of male truncate, vertical from the ventral surface to the posterior border of the dorsal depression that encloses the claspers. ( Fig. 6. ) Color usually dark chocolate brown, with contrasting reddish markings on the lateral mar- gins of the pronotum, exposed edges of abdominal tergites, the adjacent edges of the base of the corium and on the tip of the scutellum. The -6- color is sometimes light brown, with the pale markings varying to dull yellowish in such specimens. Length 13 - 16 mm., mean 14.8. . . . Chlorochroa ligata Scutellum with at least some indication of three pale spots across the base or, if none are present, general color pale green. Membrane of hemelytra colorless or with some purple flecks on the veins. Last ab- dominal sternite of male with a sloping shelf behind the depression that encloses the claspers, appearing as a lobe from ventral view ( Fig. 7) . Upper surface of body usually with scattered conspicuous, though small, pale elevated spots 8 8 Membrane of hemelytra with some purple flecks along veins. Summer form predominantly pale green, with the lateral margins of the prono- tum, exposed margins of abdominal tergites, the adjacent borders at the base of the corium, the tip of the scutellum and a median and two lateral spots at its base yellowish (Fig. 2). In some specimens the mar- ginal markings and the tip of the scutellum are partly or entirely orange. In others the anterior spots on the scutellum are obscure or absent and the other markings reduced and pale. Winter form predominantly dark green, olive -green to purplish brown, with the pale markings usually yellowish or whitish, sometimes with a tinge of orange. Length 12 - 16 mm., mean 13.6 Chlorochroa sayi Membrane of hemelytra without dark or purplish markings. Color pre- dominantly pale green ( olive in a few specimens) with the pale mark- ings as in C. sayi. The pale markings are most often greenish and not strongly contrasting, rarely pale orange. Length 12.5 - 15.5 mm., mean 14 2 Chlorochroa uhleri 9. Length 5 - 7 mm., mean 6.5. Humeral angles of pronotum without any trace of spines. Color usually green, sometimes with brownish flecks Thyanta sp. Length 8.5 - 11 mm., mean 9.7. Summer form ( Fig. 3.) predominantly pale green, without a yellowish median raised line on the pronotum. Humeral angles of pronotum with an acute spine. In a few specimens the spines and the adjacent margins of the pronotum are reddish but this color form is rare in Arizona. Winter form (Fig. 4.) olive to tan- nish, sometimes green, the scutellum usually with a yellowish elevated median line. Humeral angles of pronotum blunt Thyanta pallido- virens spinosa Field Key to Adults 1. Humeral angles of pronotum acute or sharply spined 2 Humeri of pronotum blunt to rounded 4 2. Color pale green. Humeral angles of pronotum acutely spined, some- times marked with reddish (Fig. 3.) summer form of Thyanta pallido -virens spinosa Color not pale green 3

3. Color almost uniformly brown (Fig. 1.) . Euschistus impictiventris Color pale olive -green to yellowish, with dark brown to reddish mark- ings on pronotum, scutellum and hemelytral membrane (Fig. 5.) . . Podisus acutissimus 4. Color predominantly pale green 5 Color other than pale green 9 -7- 5. Length less than 7 mm Thyanta sp. Length at least 8.5 mm 6 6. Length under 11 mm. In most specimens there is a pale midline on the scutellum ( Fig. 4.) some winter specimens of . . Thyanta pallido -virens spinosa Length at least 12 mm 7 7. Scutellum entirely pale green Acrosternum hilare Scutellum with contrasting pale tip and three spots across base . . 8

8. Hemelytral membrane with some flecks of purple ( Fig 2.) . . Chlorochroa sayi Hemelytral membrane entirely pale . . . Chlorochroa uhleri 9. Contrasting marked with black and brick red to yellow Murgantia histrionica Not so marked 10 10. Length less than 11 mm. Color olive to tannish, often with a pale median stripe on the pronotum ( Fig. 4.) winter form of Thyanta pallido -virens spinosa Length more than 12 mm 11 11. Color usually dark chocolate brown, with the margins of the body and the tip of the scutellum dull red Chlorochroa ligata Color usually dark green, olive green to purplish brown, with whitish to yellowish, sometimes slightly orange, markings on the margins of the body, the tip and three basal spots on the scutellum winter form of Chlorochroa sayi Acrosternum hilare (Say) GREEN STINK BUG This large, green species has not been taken in our crop samples. It is mentioned by Russell (1952) as occurring in the Salt River Valley on alfalfa, a mixture of alfalfa and small grains and on small grains, trees and shrubs. Sailer (1953) gives some information on its occurrence in Illi- nois and cites several references to investigations in Ohio, Virginia, Illinois and Utah, where it is a pest of orchard fruits and lima beans. Aside from Russell's records we have one observation of nymphs dam- aging green peach fruit near Mesa in 1957. The nymphs are quite unlike the adults, marked with black and orange, the abdomen of larger nymphs straw- colored with a series of black markings down the middle. The humeri of the pronotum are much more rounded than in the adult. Morrill (1910) has studied the biology in detail and the following data are from his report: an average of 30 eggs are laid in a cluster and these hatch in 9.5 days at 70 to 80° F. At 75° F. the five nymphal instars take 54 days, the developmental period being two to three weeks longer than in the other species he investigated. Russell (1952) was unable to find parasitism of adults in Arizona, either by rearing or by dissection. Chlorochroa ligata (Say) CONCHUELA This is not one of the abundant stink bugs in Arizona. We have it from only 15 of the crop area samples and the samples represented are not from the principal agricultural areas, but scattered from Pinal to Green- lee County and with two of the records from Navajo County. Ten of the samples were collected in November, well after our principal seed crops -8- are susceptible to stink bug damage. Russell (1952) reports it as "found in small numbers in all the principal alfalfa seed -growing areas of south- ern Arizona." He further mentions that it has been reported mainly from northern Mexico, Texas and New Mexico, with scattered records from Cali- fornia, Colorado and Utah. Cassidy and Barber (1938) include it as an important cotton pest in the Big Bend region of Texas and the Laguna district of Chihuahua, Mexico. Morrill (1910) gives a detailed account of the life history and habits. Russell's (1952) investigation of an Arizona population disclosed the fol- lowing life history details: egg clusters contain an average of 32.4 eggs, these hatching in 6.6 days at 70 - 80° F. The nymphal instars take an average of 28 days at 76° F. Times are reduced at higher temperatures and lengthened at lower. Adult females lived for an average of 61 days and males 59. Three summer collections of adults yielded 63% females. NATURAL ENEMIES. Russell (1952) reared two species of Tachi- nidae, Gymnosoma fuliginosa (Desv.) and Cylindromyia armata Aldrich (reported as C. euchenor (Walker)) from adults collected in the Salt River Valley. Morrill (1907, 1910) states that the victims of G. fuliginosa are adults or fifth -instar nymphs and that adults that had been parasitized as adults could be distinguished by the presence of "the yellowish -white egg or eggshell which remains attached to the host."

Chlorochroa sayi Stal (Fig. 2) SAY STINK BUG

The Say stink bug is probably the most important species in Arizona and it is represented in our samples from all counties but Mohave. Thirty - six of the 58 samples were collected from May to July and 11 in Novem- ber. The months from December to February are not represented, this being the normal period of hibernation. Clancy (1946) reports that this species is predominantly an alfalfa pest until about midsummer in the Yuma Valley. At this period it gradually replaces Euschistus impictiventris on cotton as the primary boll-puncturing species. As the bolls ripen the adults migrate to grain sorghums. Hills (1941) reports that C. sayi reduced the germination of sugar beet seed from 89.3% to 13.4% and Hills and McKinney (1946) report a reduction in the number of viable seed balls produced, as well as in the number of sprouts per viable seed ball. They note that C. sayi tends to cause slightly more of this kind of damage than does Euschistus impictiventris. LIFE HISTORY. Detailed studies have been made in northeastern New Mexico by Caffrey and Barber (1919) and at Tempe, Arizona by Russell (1952). Russell notes that oviposition takes place at any time of the day or night, wherever the female happens to be resting or feeding. The eggs are generally placed on the lower side of some portion of the food plant or underneath some object in the vicinity, in two to four parallel rows. They are laid at the average rate of one per minute. Caffrey and Barber found individual clusters to consist of from 13 to 43 eggs, with an aver- age of about 26; Russell found an average of 28.4 per cluster. Russell found that each female lays an average of 151 eggs, with a maximum of 526, during an average oviposition period of 26 days. The females often alter- nate mating and oviposition, but they may deposit two or more clusters between matings, or mate two or more times between depositions. Some females laid as many as ten egg clusters during a period of 47 days. -9- Russell found that hatching takes place in an average of 10 days at 60® - 70° F. and only 5.1 days at 80° - 90 °. Caffrey and Barber state that the eggs darken when they are nearly ready to hatch and that those in one cluster generally hatch in one 24 -hr. period. The nymphs are capable of locomotion as soon as they emerge from the egg but usually remain near the egg cluster until after the first molt. Second -instar nymphs begin to wander away singly in search of food but generally remain close to- gether. After the second molt they become solitary. Caffrey and Barber found a regular cycle of activity in the nymphs. They became active at about 8:00 A.M. and started to feed, continuing until the sun became very hot at about 11:00. They then sought out shade and remained quiet until about 2:00 P.M., when they resumed feeding. They continued feeding until late afternoon but stopped if the tempera- ture dropped. Since these observations were made in northeastern New Mexico, it could be expected that the times of activity would be different at lower elevations in Arizona. The nymphs dropped to the ground and feigned death when disturbed. During periods of high wind or rain they sought shelter and did not feed. Russell found that the nymphal instars require an average of 35 days at 73° F. and 23 days at 85° -91° F. Caffrey and Barber found that the adults are active and feed during most of the day and night. They do not cease feeding during the hottest part of the day, as do the nymphs, but become more active then. Adults are gregarious, individual plants being favored to the exclusion of others of the same kind and in the same stage of growth. This gregarious habit results in the concentration of six or eight individuals on a single grain head while adjoining heads have almost none. Activity ceases during periods of high wind, rain and hailstorm, when the adults seek shelter under objects on the ground or at the base of their food plant. The adults, like the nymphs, drop to the ground and seek cover when disturbed. Russell observed that there is a premating period of from three to 15 days and that from one to 15 days elapse after mating before the first eggs are laid. Matings usually last for two hours or longer. At Tempe, Arizona, slightly less than five weeks were required to complete the life cycle in the summer, at daily mean temperatures of approximately 85° F. Eight weeks were required in the spring and fall, at daily mean tempera- tures of 73° - 75° F. There were five generations from the end of March to the end of October at low elevations in southern Arizona (Russell, 1952) . Russell found that adult males lived for an average of 70 days and a maximum of 246 and females an average of 66 days and a maximum of 225. Samples collected in the summer contained 52 to 56% females and those collected in the winter 55 to 66 %. Caffrey and Barber found a similar ratio. Out of 564 adults collected, 313 or 55% were females. Russell indicates that C. sayi is less active than Euschistus impictiventris or Thyanta pallido- virens spinosa (reported as custator) during the cooler months of the year. HOST PLANTS. Russell (1952) reports on the host plants of this species, on the basis of extensive collections and observations in southern Arizona. Since he did not differentiate Chlorochroa uhleri, a very similar - looking species, some of his records will require verification. This is espe- cially true in the case of uncultivated host plants. Among the crop plants he found that alfalfa, seed beets, cotton, okra, squash, grain sorghum, -lo- oats and barley were most severely attacked and damaged. In the Salt River Valley the common mustard of waste land (Sisymbrium Irio) was apparently the most important wild host in the spring, populations mov- ing from it to crop plants. In the Safford area hosts such as alfileria (Ero- dium cicutarium) on range land apparently served to build up the first generation. NATURAL ENEMIES EGG PARASITES. Hymenoptera - family Scelionidae. Telenomus uta- hensis Ashmead is the abundant species of Scelionid egg parasite on stink bugs in Arizona. Caffrey and Barber (1919) found it to be one of the most effective natural control agents of C. sayi in northeastern New Mex- ico. They found it widely distributed throughout their area. Sixty percent of the C. sayi eggs they collected in late July and early August were para- sitized. Nymphs rarely hatched from an egg cluster when any individual egg produced a wasp. Dissection revealed dead parasites in the unhatched eggs. Morrill (1907) observed the same phenomenon with eggs of Chlo- rochroa ligata and Clancy (1946) with eggs of Enschistus impictiventris. Clancy found that parasitism gradually increased as the season advanced, in southern Arizona. In October 95.9% of the eggs on grain sorghum were parasitized by T. utahensis and a few by T. podisi. He concluded that "since the egg parasites apparently required most of the season to build up effective populations, their greatest benefit was in the reduction of late -generation nymphs, which otherwise would have produced large num- bers of overwintering adults. Although wide seasonal fluctuations were thus caused, the average host density was no doubt greatly lowered." He suggested that early- season mass release of T. utahensis, or the introduc- tion of other species, might improve the situation. He found that a genera- tion of T. utahensis required from 12 to 17 days at Yuma in October. With a two -week life cycle in the summer, this parasite can complete two or more generations to each generation of its host in southwestern Arizona. Muesebeck et al. (1951) list four species of Pentatomidae as hosts and Gahan (1932) reports that the species is a common parasite of pentatomid eggs in the southwestern states. Telenomus podisi Ashmead was reared in small numbers from C. sayi eggs on grain sorghum (Russell, 1952). Muesebeck et al. (1951) list eleven species of Pentatomidae as hosts. The species is apparently not abundant in Arizona. Hymenoptera - family Encyrtidae. Ooencyrtus johnsani (Howard) was collected by Russell (1952) in the Buckeye Valley. He found that it was never more than one -fourth as numerous as Telenomus utahensis. Clancy (1946) found the species associated with C. sayi eggs at Bard, California. Ooencyrtus johnsoni is apparently not restricted to stink bug eggs, since Muesebeck et al. (1951) record Arilus cristatus (a reduviid) eggs and lady beetle eggs among the hosts. EGG PREDATORS Clancy (1946) reports that Collops marginellus adults could not pene- trate the shell of C. sayi eggs, even though they tried. His observations were made near Yuma and the Gallops referred to is more likely C. vittatus, a more abundant species in that area. Field- collected eggs from alfalfa, cotton and sorghum had not been fed on by Collops. Russell (1952) gives a table of percentages of C. sayi eggs destroyed, over a seven -year period of observation. Adult stink bugs of the parent or other species accounted for an average of 10 percent and unspecified other predators for an aver- age of 2 percent. He states that "stink bug adults often suck the liquid content from eggs of their own or other pentatomid species, particularly where infestations are heavy."

PARASITES OF ADULTS AND FIFTH -INSTAR NYMPHS Diptera - family Tachinidae. Gymnosoma fuliginosa (Desvoidy). Rus- sell (1952) collected adults of this species throughout Arizona and was able to dissect out larvae throughout the year. He found parasitism to run fairly high each spring, up to 25% in C. sayi on Sysimbriurn Irio in late May at Mesa. During the summer it seldom exceeded one or two percent. Eighty -five percent of the tachinid flies he reared belonged to this species. Clancy (1946) did extensive rearing and obtained an average of 1.8% parasitism, with a maximum of 4.0% in a single collection. He recorded a slight increase during late summer but concluded that "this species was obviously of little value as a control agent." If Russell's observations on the early season populations are representative, G. fuliginosa must be of very great importance in the repression of stink bug populations at a crit- ical time, even if it is not effective in reducing numbers during the main growing season.

Caffrey and Barber (1919) state that the eggs of this fly are placed on the ventral prothoracic region, near the margin, of adults or fifth instar nymphs. The larva leaves the host in the anal area and drops to the ground to pupate. The life cycle is about as long as that of the host. Females are preferred. The stink bugs may survive after the emergence of the para- sitic larvae.

Cylindromyia armata Aldrich. This species has been reported most often as C. euchenor (Walker). Caffrey and Barber (1919) report that "the species has been observed infrequently in the field and must be con- sidered of only minor importance in the natural control of C. sayi. Its life cycle and habits, as far as observed, were very similar to those of Gymno- soma fuliginosa." Russell (1952) reared adults from C. sayi and found that parasitism was fairly high in the spring but decreased to one to two percent in the summer.

Chlorochroa uhleri Stál

This species is closely related to C. sayi and has apparently been con- fused with it in the past. It is not mentioned at all by the previous authors who have written on crop pest species in the Southwest. We have taken it in small numbers in our samples, from Yuma, Maricopa and Yava- pai Counties. Other specimens in the University collection are from Pima and Cochise Counties. The collection dates are mainly from July to Sep- tember. Alfalfa was the host recorded for all of the crop area samples but we have one additional record from cotton. The host plants have not been determined in this area but Russell's extensive list for C. sayi prob- ably includes some records referable to this species. Esselbaugh (1948) indicates that midwestern records on Opuntia, etc. refer to C. persimilis Horváth. -12- Euschistus impictiventris Stál ( Fig. 1.) This species has been known as the "brown stink bug" in Arizona. This common name has been pre -empted in the list of common names of insects approved by the Entomological Society of America, by Euschistus servus (Say) . Cassidy and Barber (1938) rated C. impictiventris as the most in- jurious cotton hemipteron in Arizona. They state that it feeds entirely on the bolls and does not invade cotton fields until the plants are fruiting. They found it to be gregarious, bands of adults constantly moving from field to field, so that the population in an individual field fluctuated widely during the growing season. They found that boll puncturing was usually followed by severe staining of the lint, the stains often starting on the immature seeds. Russell (1952) reports this species from irrigated districts through- out southern Arizona. Our samples indicate that it is most abundant in Yuma County, less so in Maricopa and with only occasional occurrence in Pinal, Cochise and Graham Counties. Thirty of the 47 samples were taken from June through August, the rest quite evenly distributed through the rest of the year. LIFE HISTORY. Russell (1952) reports the details of a life history study of this species. Egg clusters contained an average of 17M eggs and each female laid an average of 60 eggs over an average period of 107 days. The top number of eggs laid by a single female was 107. At 70° - 80° F. the average incubation period was 6.0 days, with a reduction to 4.0 days at 90 - 100° F. The five nymphal instars required an average of 29 days at 76° F. and slightly longer at 86 °. Fifty -four percent of summer - collected adults were females. The adult males lived for an average of 97 days and the females 106. NATURAL ENEMIES. Clancy (1946) studied the natural enemies of the eggs on cotton in the Yuma Valley. He found that Collops margi- nellus (probably C. vittatus) adults destroyed 42.9% of the eggs under field conditions during the period of study. Telenomus utahensis Ashmead (reported as Telenomus mesillae (Cockerell)) emerged from 18.5% of the eggs and an additional five percent contained Telenomus that had died before emerging. Therefore, two natural enemies destroyed about two - thirds of the eggs. He conducted laboratory tests of predators, using species of Geocoris, Nabis, Sinea and Zelus. None of these insects attacked the eggs. Zelus renardii and Sinea con f usa (reported as Sinea undulata) readily attacked moving first instar nymphs but ignored them if they remained motionless. Collops adults had a decided preference for eggs and could not be induced to attack nymphs. Of the parasites of adults and large nymphs, Russell (1952) dissected only one larva of Gymnosoma fuliginosa from each of two adults out of several thousand examined. He never succeeded in rearing adults from this species. Murgantia histrionica (Hahn) HARLEQUIN BUG The harlequin bug has a bad reputation in other parts of the country as a pest of cabbage and other cole crops and, sometimes, other vegetables. The preferred food plants seem to be the Cruciferae, which include many -13- common weeds. It has been our experience that Murgantia can be very common in a weedy area and not be of importance to crops. Jackass- clover (Wislizenia refracta) almost always has a few individuals on it and some- times very large numbers. There have been reports of heavy damage to cole crops in the Salt River Valley and the Safford area. In general, the insect can be expected at intermediate elevations, from Cochise to Yavapai Counties and probably beyond. It is apparently completely absent in the Yuma area.

Podisus acutissimus Sthl (Fig. 5.) Members of the genus Podisus and some others depart from the plant - feeding habits of most of the family, and are predators. P. acutissimus is a species confined to the Southwest in the United States, with a wider range in Mexico. We have it in our samples from the southern part of the state, from Maricopa to Cochise and Greenlee Counties. Yuma is rep- resented by other collections. Most of our records are concentrated in the period from June to November. We have been unable to find any sig- nificant observations on the biology of this species in the literature. We find it in small numbers and do not believe that it has shown itself to be abundant enough to be one of our most important predaceous insects. In the absence of observations on the type of prey selected, we do not even know how it fits into the overall picture.

Thyanta pallido -virens spinosa Ruckes ( Figs. 3 & 4.) This is the species long known under the name Thyanta custator (Fabricius ) in Arizona. Ruckes (1957) has shown that the name custator should be restricted to a species that occurs along the Atlantic and Gulf Coasts of the United States. The common name, "red- shouldered plant bug," has been used in this region but is not on the list of common names approved by the Entomological Society of America. This common name is an unfortunate one in this area, because few individuals have the red "shoulders" that provide the name. We have collections from all counties and from all months, although the summer months are best represented. Cassidy and Barber (1938) ranked the species as one of the more injurious hemipterous cotton insects, athough it does much less damage than Chlorochroa sayi and Euschistus impictiventris. Morrill (1910) noted that it is usually hidden by the bracts when it is feeding on the squares and bolls and that it is therefore easy to overlook. It probably feeds on a wide variety of developing seeds. Russell (1952) has studied the life history in Arizona. He found that the premating period is from one to five days and that three to five days elapse after mating before the first eggs are laid. Mating and oviposition were alternated, although two or more egg clusters might be laid between matings or matings might take place two or more times between egg depo- sitions. One female laid ten egg clusters and mated eight times in 34 days. Egg clusters contained an average of 27.5 eggs. During an average ovi- position period of 29 days, females laid an average of 118 eggs, with a maximum of 334. The eggs required an average of 5.6 days to hatch at 70 - 80° F. and 4.1 days at 90 - 100°. The five nymphal instars took an average of 33 days at 75 °, 25 at 85° and 19 at 91 °. Adult males lived for an average of 52 days and a maximum of 83, while females lived for an average of 63 and a maximum of 108. Fifty -three percent of the indi- -14- viduals collected in the summer were females. He found that slightly less than five weeks were required for a generation in the summer, and seven weeks in the spring and fall. Five generations per year would be possible at lower elevations in southern Arizona. NATURAL ENEMIES. Morrill (1910) reared Telenoinus utahensis from eggs both in the laboratory and in the field. Russell (1952) did not find tachinid parasites in the adults but Morrill (1910) frequently found eggs attached to them. He could not rear flies to maturity on this species.

Thyanta spp. Several small, broad species are grouped here, including T. rugulosa (Say), T. pusctiventris Van Duzee and T. brevis Van Duzee. These have been taken in small numbers in scattered locations throughout the state. Until one of them is implicated as a crop pest, there is little reason to study them in detail. There have been some reports of a small species of stink bugs feeding on heads of grain sorghum, which may refer to this group.

-15- LITERATURE CITED

Caffrey, D. J. and G. W. Barber. 1919. The grain bug. U.S.D.A. Bul. 779. Cassidy, T. P. and T. C. Barber, 1938. Hemipterous cotton insects of Ari- zona and their economic importance and control. U.S.D.A. E -439.

. 1939. Hemipterous insects of cotton in Arizona: Their economic importance and control. Jour. Econ. Ent. 32: 99 -104. 1940. Investigations in control of hemipterous cotton insects in Arizona by the use of insecticides. U.S.D.A. E -506. Clancy, D. W. 1946. Natural enemies of some Arizona cotton insects. Jour. Econ. Ent. 39: 326-328. Esselbaugh, C. 0. 1948. Notes on the bionomics of some midwestern Pentatomidae. Ent. Amer. 28( 1 ) : 1 -73. Gahan, A. B. 1932. Miscellaneous descriptions and notes on parasitic Hyme- noptera. Ann. Ent. Soc. Amer. 25: 736 -757. Hills, 0. A. 1941. Isolation -cage studies of certain hemipterous and homop- terous insects on sugar beets grown for seed. Jour. Econ. Ent. 34: 756 -760. Hills, 0. A. and K. B. McKinney. 1946. Damage by Euschistus impictiven- tris and Chlorochroa sayi to sugar beets grown for seed. Jour. Econ. Ent. 39: 335 -337. Morrill, A. W. 1905. Report on a Mexican cotton pest, the " conchuela." U.S.D.A. Bur. Ent. Bul. 54: 18 -34. Morrill, A. W. 1907. The Mexican conchuela in Western Texas in 1905. U.S.D.A. Bur. Ent. Bul. 64: 1 -14.

. 1910. Plant -bugs injurious to cotton bolls. U.S.D.A. Bur. Ent. Bul. 86.

. 1912. Report of the entomologist of the Arizona Horticultural Commission. 1912. 4th Ann. Rpt.: 34. Muesebeck, C. F. W., K. V. Krombein and H. K. Townes. 1951. Hyme- noptera of North America - Synoptic Catalog. U.S.D.A. Agricul- tural Monograph No. 2. Ruckes, H. H. 1957. The taxonomic status and distribution of Thyanta custator ( Fab.) and Thyanta pallido- virens (Stál) . American Mus. Novitates No. 1824. Russell, E. E. 1952. Stink bugs on seed alfalfa in Southern Arizona. U.S.D.A. Circular 903. Sailer, R. I. 1953. A note on the bionomics of the green stink bug (Hemip- tera : Pentatomidae) . Jour. Kans. Ent. Soc. 26:70 -71.

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