THE YALUE OF PREBACEOUS BEETLES IN BESTROYING INSECT PESTS. By A. F. BURGESS and C. W. COLLINS, Of the Bureau of Entomology. WORK ON PARASITIC ENEMIES OF INSECT PESTS. During the past few years much attention has been paid to the value of the parasitic enemies of some of our common destructive insect pests, but the greater part of the work has been attempted for the purpose of introducing into this country, or transporting from one part of the country to another, natural enemies which appear to be necessary in order to bring about the control of destructive specie^ which are new in the locality where the damage is most noticeable. As early as 1883 a few beneficial species were introduced into this country by the Division of Entomology, now the Bureau of Ento- mology, United States Department of Agriculture, and since that time the work has been carried on intermittently whenever there seemed to be an opportunity to secure some valuable natural enemies of destructive insects. Similar work has been attempted and carried on continuously for a number of years by the board of horticulture of California, and, more recently, the Hawaiian Sugar Planters' Experi- ment Station at Honolulu has taken up this line and has succeeded in introducing several enemies of insects which affect sugar cane. The largest attempt of this sort is now being made by the State of Massa- chusetts in cooperation with the Bureau of Entomology of the United States Department of Agriculture in an attempt to secure the para- sites and natural enemies of the gipsy and brown-tail moths in Mas- sachusetts. These insects were introduced from Europe a number of years ago and since that time have caused widespread destruction to orchards and forests. USEFULNESS OF PREDACEOUS BEETLES. It is not the purpose of this article to discuss parasite work, but to ' point out one phase of it that is seldom given marked prominence, namely, the value of predaceous beetles. Strictly speaking, they are not parasites, but are often classed as such for convenience, as they are carnivorous and destroy their prey by feeding upon it externally, and in this way accomplish the same object but in a different manner from that of the true parasites, the larvae of which feed internally upon the host. 453 454 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE. Among our native beetles that are predaceous in habit are several species which belong chiefly to two families, namely, the Carabidse, commonly known as ground-beetles, and the Coccinellidse, or lady- birds. It is true that the tiger-beetles (Cicindelidse) and some species of Tenebrionidae are predaceous and that certain elaterids undoubt- edly have similar habits, although very few observations have been made to show how much they accomplish in destroying insect pests. The larvae of many of those already referred to are also predaceous, and this renders each species more effective in reducing and bringing under control injurious insects. June 15, 1910, Mr. H. S. Barber observed near Melrose Highlands, Mass., a small burrow in the ground which contained a larva of one of the tiger-beetles, probably Cicindela 6-guttata Fab. Surrounding the mouth of the burrow (PI. LXII, fig. 1) were the remains of 10 partly grown gipsy moth caterpillars which had been partially eaten by the beetle larva and cast from the burrow. Since that time we have attempted to determine whether adults of this species when kept in captivity would feed upon caterpillars. In each case a few cater- pillars were eaten, but the beetles do not live long under such condi- tions, so that it is a difficult matter to ascertain the amount of food which they normally consume. There are several families of predaceous beetles the adults of "which live in ponds and streams. Some of these are known to feed on young fish, and in this way they may cause injury rather than benefit. The two principal families, however, about which the most is known are the Carabidse and the Coccinellidae. Among the latter are a large number of species which are common in most regions of the United States. BENEFICIAL WORK OF NATIVE LADYBIRDS ( COCCINELLID^ ). Several species, such as A dalia hipunctata L. (fig. 15), the two- spotted ladybird, and various species of the genus Coccinella and other closely related genera feed principally on plant-lice, insects belonging to the family Aphididae, but sometimes attack small larvas of various sorts. Owing to their enormous reproductive capacity, the plant-lice are often very serious pests^ as many generations are produced in a single year, and great damage would result to the crops or trees on which they feed unless their increase were checked by natural enemies or by hand suppression. The latter is seldom necessary, however, owing to the effectiveness of the former, but occasionally, when conditions are unfavorable for the increase of ladybirds, the damage is very great. VAIiUE OF PEEDAOEOUS BEETLES. 455 Nearly every spring plant-lice are abundant on some one or more of our common cultivated crops, or trees and shrubs. The apple aphis (Aphis mali Fab.; fig, 16), is sometimes very abundant and causes FIG. l^.—Adalia Upunctata: a. Larva ; h, mouth parts of same ; c, claw of same ; d, pupa; 6, adult; f, antenna of same. All enlarged. (From Marlatt.) serious injury to apple trees, especially to seedlings and young stock in nurseries. It seldom becomes noticeable until the leaves on the terminal twigs or shoots begin to curl (fig. 17), owing to the presence FIG. 16.—The apple aphis (Aphis mali) : a. Winged agamic form ; h, pupa ; c, wingless agamic form ; d, recently born aphis. All greatly enlarged. (From Quamtance.) of large numbers of the aphides which are feeding on the sap. Be- fore the injury proceeds very far the increase of the plant-lice is usually prevented by the inroads made upon their numbers by the more common species of ladybirds, which in both adult and larval 456 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE. forms feed upon these pests. It is true that some species of aphides are controlled almost completely by parasites and many are preyed upon by syrphids and lace-wing flies. The value, however, of lady- birds in accomplishing the control of many of our common species of plant-lice has never been overestimated, and it is probable that too little credit has been mven these beneficial insects. FIG. 17.—Terminal shoot of apple infested with the apple aphis (Aphis mali), showing condition of leaves. (From Quaintance.) Early in the spring of 1898 Mr. A. F. Burgess observed in Maiden, Mass., that the gray birches over a considerable area were thickly cov- ered with small, black aphidid eggs. These were kept under obser- vation for several weeks, and as soon as the weather became a little warmer, about the middle of April, several species of ladybirds, the principal ones being Adalia hlpiinctata L., Cocchiella sanguínea L., Yearbook U. S. Dept. of Agriculture, 19t 1. PLATE LVII SALTlMOtlB. SOME NATIVE AND IMPORTED SPECIES OF CALOSOMA. FIG. 1. —Calosoma scrutator. FiG. 2. —Calosoma wiUeozi. Via. 3. — Calosoma frigidum. FIG. i. —Calosoma ealidum. FIG. S. —Calosoma exiernum. FiG. 6. —Calosoma lugubre. FIG. 7. — Calosoma semilm>c. FIG. 8. — Calosoma sayi. FiG. 9. — Calosoma maximowiczi. FIG. 10. —Calosoma chirw.nse. FIG. 11. — Calosoma auropunctatum. FIG. 12. — Calosoma reiiculatum. FIG. IS.—Calosoma inquisitor. Natural size. (Original.) Yearbook U S Depf of AgricuHure, 1911. PLATE LVIII. THE GIPSY MOTH IPORTHETRIA DISPAR. Fig. 1.—Male moth. Fit;. 2.-Female moth. Fig. .3.—Male pupa. Fig. 4.—Female pupa. Fig. .ï.—Egg cluster. Fig. u.—Caterpillars; the largest are less than half grown. (From Rogers and Burgess.) VALUE OF PREDACEOUS BEETLES. 457 G, 9-notata Herbst (fig. 18), G, trifasciata L., and Anatis 15-punctata Oliv., made their appearance in large numbers and fed freely on the ç^gg masses. Numerous experiments were made to determine the number of eggs that were consumed by one of these beetles, as it was apparent that the development of the aphidid was being seriously checked by the destruction of the eggs before hatching. Control ex- periments showed that an ^à\x\t Adaliahipunctata^x^YdigQà to destroy 100 aphidid eggs daily. Owing to the enormous number of eggs that had been deposited the previous fall it was inevitable that a large number of the aphidids would escape, but these were followed up by the ladybirds and their larvae, so that before midsunimer it was almost impossible to find a specimen in the region which had been badly infested, and in the fall the eggs of this species could be found on the trees only after prolonged search. In this case the aphidid was brought under complete control by ladybirds. During the spring feed- ing experiments were con- ducted to determine the number of aphidids which were being consumed by the various species of Cocci- nellidae which were found abundantly among the in- fested trees. As a result of FIG. 18,—Coccînella 9-notata: /, Adult; g, larva of this work it was determined ^^°^^- ^" enlarged ; size indicated by hairline at riifht. (From Chittenden.) that on the average each beetle destroyed 60 aphidids daily, while the average number killed by each beetle larva amounted to 53 daily. The number of eggs laid by a single fernale of various species of ladybirds, when in captivity, ranged from 19 to 426, and seemed to depend largely upon food supply. The length of time required to develop a generation in early summer was from 30 to 52 days, depending upon the species. It is interesting to note that several somewhat similar experiments were conducted by Dr.