The Gtpst and Brown-Tail Moths and Their European Parasites
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THE GTPST AND BROWN-TAIL MOTHS AND THEIR EUROPEAN PARASITES. By L. O. HowABD, Ph. D., Chief of the Bureau of JEntomology. INTRODUCTION AND SPRKaD.OF THE MOTHS IN UNITED STATES. All of the earlier works on the injurious insects of Europe have contained references to and descriptions of the so-called gypsy mpth {Ocne7'ia dispar Linn.). The brown-tail moth (Miprootis chrysorrhœa Linn.) is also a native European insect and for many years has been noted as an enemy to fruit trees. Both of these insects have been introduced into the United States in the vicinity of Boston and have multiplied and spread with alarming i-apidity. The gypsy moth was first introduced in 1868 by Prof. L. Trouvelot, of Harvard University, who was experimenting in the crossbreeding of wild silkworms. An egg cluster of the gypsy moth blew out of his window in Maiden, and he was unable to recover it. Twenty years later, in 1889, the species had increased to such an extent that the cater- pillars were a great nuisance in the city of Maiden, and the State under- took an investigation in the hope of exterminating the species. It was found to have spread until it occupied a territory of about 100 square miles, and during the next ten years the State, by constantly increas- ing appropriations and by the active work of a large number of paid employees, had succeeded in practically controlling all further spread and in greatly reducing the numbers of the insect. In 1900, however, appropriations lapsed, and from that year until 1905 the insect was again allowed to multiply and spread, unhindered save by the opera- tions of private persons. It soon became as numerous as it had been early in the State investigation, and the boundaries of the region inhab- ited by it widened out greatly, until now it has reached as far west as Worcester and occurs all along the New Hampshire line on the north, extending over into that State at Seabrook, Hampton, North Hampton, and Portsmouth (see fig. 1). It has also made its appearance in por- tions of Providence, R. I. The brown-tail moth was first noticed in the early nineties in Somer- ville, Mass., where it was probably introduced in a shipment of roses from Holland. It multiplied and spread, although the work of the gypsy moth commission was directed against this insect as well as against the gypsy moth down to the year 1900. It has since become 123 124 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE. even more abundant and injurious than the gypsy moth, and, owing to the fact that the female flies readily, whereas the female of the gypsy moth does not fly at all, the brown-tail moth has far exceeded the gypsy moth in its spread. It now covers a territory extending from East- port, Me., on the northeast, as far south as Cape Cod, and to the west FIG. 1.—Sketch map of eastern Massachusetts, showing gypsy moth area. as far as Amherst, Mass. It doubtless also exists in many communi- ties in and out of Massachusetts from which it has not been reported. LIFE HISTORY AND DESCRIPTION OF THE GYPSY MOTH. The gypsy moth has but a single generation each year. It winters in the egg stage, and the young caterpillar hatches from the egg about THE GYPSY AJSTD BROWK-TAIL MOTHS. 125 the first of May. It feeds upon the leaves of many different plants. It attacks practically all fruit, shade, and woodland trees, showing some preference for apple, white oak, red oak, willow, and elm. It kills both deciduous and coniferous trees. Woodlands attacked by it in number are stripped bare and many trees are killed. It feeds upon the foliage of shrubs, vines, bushes, and flowers, and will eat grass and garden and field crops. The full-grown caterpillar is 3 inches or a little less in length, and has a dark-gray or sooty color effect. The back is marked with yellow; along the back is a double row of blue spots fol- lowed by a double row of red spots—five pairs of blue and six pairs of red. The young larvae do not show these spots well, but in the full- grown ones they are very evident. About the first of July, or a little later, the larva changes to pupa (PI. I) in a partial cocoon formed of a few FIG. 2.—The gypsy moth {Ocneria dispar): a, female moth; 6, male moth; c, halfgrown larva; d, mature larva. Slightly enlarged (original). türeads of silk, sometimes connecting leaves together. From the mid- dle of July to the middle of August the winged moths appear (fig. 2), The male is brownish yellow, and has a slender body and a wing expanse of about li inches. It is an active flier. The female moth is nearly white, somewhat spotted with black. It is very sluggish, and its body is so heavy that it can not fly. Its wing expanse is about 2i inches. The eggs are deposited by the females shortly after issuing, and are laid in masses, each containing about öOO eggs closely packed with yellowish hair from the body of the female, oval in shape and about li inches long by three-fourths of an inch wide. The eggs are laid on the trunks of trees, on the sides of houses, fences, stone walls, and other places. The females seem especially attracted to recesses where the eggs are 126 YEABBOOK OF THE DEPARTMENT OF AÖRIOÜLTURE. more or less hidden. Large holes in old trees will be found filled with them, and they are often found in the crevices between stones in a stone wall, or in the hollow of an old stump or log. The larvae (fig. 2), especially after they reach some size, feed princi- pally at night and try to hide themselves during the day. In daytime they will descend upon the larger limbs and trunk and try to find some place under the bark or in a large hole where they can secrete them- selves. It is this habit that has led to the use of burlap bands around the trunks of trees, under which they will hide during the day and where they can be found easily and destroyed. LIFE HISTORY AND DESCRIPTION OF THE BROWN-TAIL MOTH. The caterpillar of the brown-tail moth is primarily an enemy of pear, apple, cherry, peach, and other fruit trees, but it is also found commonly upon various shrubs that grow in door- yards; in Massachusetts it has begun to attack the for- est trees and now affects especially the oaks. Young oaks—oak scrub—are appar- ently particularly attractive to it at present. The insect does not hiber- nate in the egg stage, as does the gypsy moth, but as the young caterpillar. It has, like the gypsy moth, but one generation each year. FIG. Z.—The hrown-t&n moth {EuprocHs chrysmrhœa): Fe- The CggS are laid in maSSCS male moth above, male moth below, right. Slightly enlarged (original). ^^'^^^'^' ^' on the under side of the leaves in the latter part of July. The egg masses are brown and covered with hair, and each con- tains about 300 eggs. The masses.are much smaller than those of the gypsy moth, averaging about two-thirds of an inch in length by about one-fourth of an inch in width. The eggs hatch during August, and the young caterpillars feed in clusters on the upper surface of the leaves, a little later beginning to spin their winter webs by drawing together a number of leaves with silk, in which web a large number of caterpillars stow themselves away for the winter. These webs or nests, composed of leaves and silk, will average from 5 to 6 inches in length, and each will contain 200 or more caterpillars. They feed until cold weather, when all enter the web and close the exit holes. They are then about one-fourth grown. Early the following spring, as soon as the buds begin to appear on the fruit trees, they issue from the o ver-wintering THE GYPSY AND BBOWN-TAIL MOTHS. 127 nests and.attack first the buds and the blossoms, and later the foliage. The full-grown larva is about 2 inches long, reddish brown in color, with a broken white stripe on each side and two red dots on the back near the hind end. They will migrate from one tree to another, com- pletely stripping the foliage as they go. When full grown they spin their cocoons either on the tree trunks or within the leaves on the branches of the trees. 'r ^ M^ 1 PIG. 4.—Hairs of the caterpillar of the brown-tail moth, highly magni- fied (adapted from Kirkland). The moths are pure white, except that the female has a conspicuous bunch of brown hair at the tip of the abdomen, from which it derives the name '^ brown-tail moth.'^ The female expands about 1^ inches and the male is smaller. Both male and female (fig. 8) fly readily, largely at night, and are greatly attracted by electric lights. It is not alone by its damage to the foliage of fruit and other trees that the brown-tail moth is a pest. The hairs of the larvae are finely 128 YE AEBOOK OF THE DEPARTMENT OF AGRICTJLTUBE, barbed and brittle (see fig. 4), and where the caterpillar comes in con- tact with the human skin the hairs enter the skin pores, break off, and cause a severe irritation.