SB 818 e578 ENT No. 39, REVISED EDITION. uted States Department of Agriculture, BUREAU OF ENTOMOLOGY, L. O. HOWARD, Entomologist. THE COMMON SQUASH BUG. (Anasa tristis DeG.) By I’. H. CHITTENDEN, In Charge of Breeding HKxaperiments. GENERAL APPEARANCE AND METHOD OF WORK. The best known of all the insects which infest squashes and pump- kins is the common squash bug, Anasa tristis DeG., otherwise known as stink bug from its disagreeable odor. It is also called black squash bug to distinguish it from that other enemy of cucurbits, the so-called “striped bug” (Diabrotica vittata) . The species is a member of the heteropterous family Coreidee. The adult bug. shown at fig. 1, a, is of large size, nearly three-fourths of an inch long. It is dirty blackish brown above and mottled yellowish be- neath. Its wings, as with other insects of its suborder, are folded diagonally across its back, leaving a _ large triangular space, the scutellum, between. On the under side is its FIG. 1.—Anasa tristis: a, mature female; b, side view of head, showing haustellum; ce, ab- haustellum or beak (see De by dominal segments of male; d, same of fe- : jit aes sats male—a, twice natural size; b, ¢, d, slightly means of which it sucks up the juices more enlarged (author’s illustration). of the plants on which it feeds. The sexes may be distinguished by the external genital organs, ¢, of the illustration representing the male and, d, the female. The injury wrought by this bug is not confined to squash and pumpkin, although these plants, particularly the former, suffer most, as records are not wanting to show at least occasional injury to other cucurbits. This insect is more or less harmful during its entire active existence, from the time it leaves the egg till its demise. When numbers attack a plant together it is soon exhausted, and its death often follows. It is a well-established fact that it is not alone the extraction of the juices that destroys a plant, but that, whenever the bug punctures or “’stings’’ a leaf-stalk, it injects a drop of liquid, sup- posed to be its saliva, which has a poisonous effect on the plant, caus- ing the death of the cell tissue about the puncture. It attacks also the leaves and occasionally the fruit of cucurbits. Still another form of in- jury is due to the insect’s acting, although perhaps not to a very great extent, as a transmitter of the insidious bacterial disease, Bacillus tra- cheiphilus Erw. Sm. ~ Ty ala a 2 Attack on young plants is much more serious than on older and larger ones, a few punctures sometimes being sufficient to cause their death. Soon after being punctured, the tips and leaves wilt or droop and eventually die. Later in the season the bugs do little harm, as the vines by this time have acquired sufficient vigor to resist attack. Injury by this squash bug is sometimes exaggerated in reported cases, the damage observed being often due to other insects which are less apt to be noticed. Weseldom find fewer than three or four forms of injuri- ous insects present upon an infested plant at the same time, and this squash bug on account of its large size is more apt to attract attention than are the much smaller but more destructive striped cucumber beetle and melon louse; the squash-vine borer by reason of its secluded man- ner of living concealed within the vines is not so readily detected, and the result is that the squash bug receives the i \\e 7 blame for the depredations of the others. OE Ae Ya \\ 9008 90/7 DISTRIBUTION. ra N88 pecosceem \ \ V/ ; a s HE 4 \@ 0/ / The common squash bug is known throughout Ca i\\ oY j practically the entire United States, being par- oe) i\\N ticularly abundant east of the Rocky Mountains, eo where it ranges from Maine to the Gulf States. Fig 2.—Eggs of Anasa tristis: [t is also recorded westward to Colorado, New a, from below, showing point j ‘ ' eal ie “aa of attachment; b. from side, Mexico, Arizona, and California. Judging by showing place of escape of 4. — Pee eee Ae ate - 2 OES nymph: c. sculpture of ege; PUblished records and the correspondence of this ai ee8 Glaser a by. Bpout office it is most injurious in the southern portion ive times natural size; ad, 2 y m=) Y y . ° one-fourthenlarged;c,great- OL New England, New York, Ohio, Indiana, and ly Cnlarged (author's Mus" Michigan, although, of course, more or less harm- ful in many other States. In certain of the other States which it is known to inhabit it is less troublesome, except occasion- ally insmall gardens. This species also occurs in Canada and is recorded from British Honduras and Mexico.! LIFE HISTORY AND HABITS. Injury may begin soon after the first sprouting of the plants, or after the plants have made some considerable growth, and may continue until their death or the departure of the bugs to places of concealment for hibernation. The plants are first attacked by the hibernated bugs. Soon after their first appearance, which varies according to temperature and locality from early spring in the South to late in June farther north, the insects copulate and begin the deposi- tion of their eggs, attaching them by an adhesive secretion to the leaves in masses of three or four to forty or more. The eggs, shown in the illustration (fig. 2, a, b), are metallic brown or bronze in color and flattened on three sides. They are laid usually on the under side of a leaf, but not infrequently also on the upper side; often in regular rows, but sometimes less regularly ; and either separated as in the larger mass at d, or more closely crowded together as in the smaller mass. They are whitish when first laid, but soon change to bronze, and hatch in from eight to thirteen days into small green and black creatures, which resemble somewhat the mature insects but differ in having proportion- ‘See W. L. Distant, Biol. Cent. Amer., Rhynchota, p. 139, for distribution and bibliography. 9 v ately longer legs and antenna. These make their escape from the egg- shell through a little round hole cut out of one end, as shown at b. In this period of its existence,! which is known as the first nymph stage (see fig. 3, a), the insect lives in colonies, at first remaining close to- gether upon the leaf near where the eggs were laid, but later congregat- ing about the bases of the leaf-stalks or hiding, together with individuals of the more advanced stages and the parent insect, under nearby clods or rubbish, or in any convenient retreat, and coming forth toward dusk in search of food. The nymphs cast their skins five times before reaching the mature condition, increasing their growth after each molt. Three days alter hatching, the nymph having attained a larger size molts and assumes the second stage, which is illustrated at 6. In this stage it lives eight or nine days before under- going the next molt. The N fo ~w ra third stage, illustrated at ¢, ( requires seven to eight, and the fourth six days. The fifth stage, shown at e, is passed in eight days, when the fifth and final molt takes place and the insect appears as a full-sized bug. In its last stage the insect contin- ues to feed, but with the dis- appearance of its food sup- ply, caused by the dying or Bee egortiicteron on | 7G 8 Aneee ticle nvmte: a, pels paved ty which it has fed, it seeks stage—all about twice natural size (author's illustra- shelter in any convenient pow rubbish, under boards or stones, old vines or similar vegetation, or under the loose bark on dead trees, or in cracks of barns and outhouses, and here passes the winter. Hibernation in the District of Columbia, where the periods above mentioned have been observed by the writer, begins some time in September. NATURAL ENEMIES. The disgusting odor of this insect, as well as its habit of remaining hidden during the day in various places of concealment, serves doubt- less in a great measure to protect it against rapacious birds and some sorts of insects. Nevertheless it falls a victim to certain parasitic ene- mies, among which a Tachinid fly,? which appears at about the same time as its host, deposits its eggs upon and develops within the living body of the adult insect, is the most abundant and conspicuous. It is also parasitized by small Chalcidid flies, one species of which has been recorded by Miss M. E. Murtfeldt to have destroyed as many as 80 per cent of its host. Three chalcidid parasites of the eggs of this insect are also known.’ The bugs themselves are reported sometimes to develop ‘In the District of Columbia the bugs have been observed to appear first about the second week in June. 2Trichopoda pennipes Fab. ° Hadronotus anase Ashm.; Ooencyrtus anase Ashin., and Hupelmus reduvii How. SMITHSONIAN INSTITUTION WAAL 088 01272 6980 cannibalistic propensities, the older ones killing the younger and weaker and extracting the vital fluids from their bodies. In addition to this the species is subject to a bacterial disease.! METHODS OF CONTROL, This insect 1s unusually resistant to insecticides, and this is partic- ularly true of the adults. A wash strong enough to kill the mature insect will at the same time destroy the vines. This renders it neces- sary to proceed against it by hand and by cultural methods. Hand-picking early in the season.—A lookout for the bugs should be kept early in the season, and these as well as the eggs should be picked off or cut away with shears and destroyed. The eggs, on account of their large and conspicuous appearance when deposited in clusters while the vines are young, are readily seen, and the grower should make a practice at the beginning of each season of going over the vines every few days. Such young as may hatch in spite of these precautions may be killed by kerosene emulsion applied upon their first appearance. Trapping the bugs.—The bugs may also be trapped by placing on the ground at intervals through the garden, boards, shingles, pieces of bark, or similar material, to which the insects will be attracted for shelter. Here they should be looked for and destroyed every morning or so during the early season. Protection to cucurbits other than squash, and perhaps pumpkin, can be secured by growing these plants with the others to serve as trap crops. Attack will thus be centered upon a few plants where the insects can be the more readily controlled. Other methods.—A number of the remedies in use against the striped cucumber beetle” and other insect enemies of cucurbits will assist in the destruction or control of this species. Among these are the protec- tion of young plants with coverings, the use of repellents, such as land plaster or gypsum saturated with kerosene or turpentine, the planting of an excess of seed to distribute attack, the stimulation of the growth of the plant by manures or other proper fertilizer, and lastly, clean cul- tural practice. If the precaution be taken to gather the vines as soon as the crop is harvested and burn them, many bugs in their different stages will be destroyed and the crop of insects will be reduced for the ensuing year. ' Bacillus entomotoxicon Dugegar. 2 See Circular No. 31, Div. Ent., The Striped Cucumber Beetle, pp. 4-7. Approved : JAMES WILSON, Secretary of Agriculture. WASHINGTON, D. C., March 23, 1905. O