[Illustration: 33_a_. Io moth larvæ on willow. Photograph by M. V. S.] _Sibine stimulea (Empretia stimulea)_, or the saddle-back caterpillar (fig. 32), is another which possesses nettling hairs. This species belongs to the group of Eucleidæ, or slug caterpillars. It can be readily recognized by its flattened form, lateral, bristling spines and by the large green patch on the back resembling a saddle-cloth, while the saddle is represented by an oval, purplish-brown spot. The small spines are venomous and affect some persons very painfully. The larva feeds on the leaves of a large variety of forest trees and also on cherry, plum, and even corn leaves. It is to be found throughout the Eastern and Southern United States. [Illustration: 33_b_. Io moth. Full grown larva. Photograph by M. V. S.] [Illustration: 34. Io moth. Adult. Photograph by M. V. S.] _Automeris io_ is the best known of the nettling caterpillars. It is the larva of the Io moth, one of the Saturniidæ. The mature caterpillar, (fig. 33), which reaches a length of two and one-half inches, is of a beautiful pale green with sublateral stripes of cream and red color and a few black spines among the green ones. The green radiating spines give the body a mossy appearance. They are tipped with a slender chitinous hair whose tip is readily broken off in the skin and whose poisonous content causes great irritation. Some individuals are very susceptible to the poison, while others are able to handle the larvæ freely without any discomfort. The larvæ feed on a wide range of food plants. They are most commonly encountered on corn and on willow, because of the opportunities for coming in contact with them. [Illustration: 35. Larva of brown-tail moth. (Natural size). Photograph by M. V. S.] The larvæ of the brown-tail moth (_Euproctis chrysorrhœa_) (fig. 35 and 36), where they occur in this country, are, on account of their great numbers, the most serious of all poisonous caterpillars. It is not necessary here, to go into details regarding the introduction of this species from Europe into the New England States. This is all available in the literature from the United States Bureau of Entomology and from that of the various states which are fighting the species. Suffice to say, there is every prospect that the pest will continue to spread throughout the Eastern United States and Canada and that wherever it goes it will prove a direct pest to man as well as to his plants.