At this stage the caterpillars may be seen wandering about on fences, trees, and along the roads in search of a suitable place to spin their cocoons, which are creamy white, and look very much like those of the common tent caterpillar, except that they are more loosely constructed.
Within the cocoons, in two or three days they transform to pupæ of a reddish brown color, densely clothed with short pale yellowish hairs. The moths appear in two or three weeks, soon lay their eggs and then die. The insects are not abundant many years in succession, as their enemies, the parasites, increase and check them.
Many methods have been suggested for their destruction, but the most available and economical are to remove the clusters of eggs whenever found, and burn them, and to shower the trees with Paris green in the proportion of one pound to one hundred and fifty gallons of water.
THE STALK BORER.
Gortyna nitela (Gruen.)
The perfect moth, Fig. 19, 1, expands from one to one and a half inches. The fore wings are a mouse gray color, tinged with lilac and sprinkled with fine yellow dots, and distinguished mainly by a white band extending across the outer part. The moths hibernate in the perfect state, and in April or May deposit their eggs singly on the outside of the plant upon which the young are to feed. As soon as the eggs hatch, which is in about a month, the young larvæ, or caterpillars, gnaw their way from the outside into the pith.
The plant does not show any sign of decay until the caterpillar is fully grown, when it dies. The caterpillar, Fig. 19, 2, is about one and one-fourth inches long, of a reddish brown color, with whitish stripes along the body. The stripes on the sides are not continuous, and the shading of the body varies, being darker on the anterior than on the posterior portion. When fully grown, Fig. 20, the color is lighter and the stripes are broader. At this stage of life it burrows into the ground just beneath the surface, and changes into the pupa state. The pupa is three-fourths of an inch long, and of a mahogany brown color. The perfect moth appears about the first of September, and there is only one brood in a season.
The caterpillars feed in the stalks of corn, tomatoes, potatoes, dahlias, asters, and also in young currant bushes, besides feeding on many species of weeds. By a close inspection of the plants about the beginning of July, the spot where the borer entered, which is generally quite a distance from the ground, may be detected, and the caterpillar cut out without injury to the plant. This plan is impracticable for an extensive crop, but by destroying the borers found in the vines that wilt suddenly, one can lessen the number another year.