1896.] NATURAL SCIENCES OF PHILADELPHIA. 13 



the upper or under side. When suddenly disturbed they drop from 

 their perch, suspending themselves by a silken thread, which is at- 

 tached to the leaf from which they started. They retain this habit 

 until they are nearly full-grown, which occurs about the middle or 

 toward the end of June. They then begin to wander, leaving the 

 trees on which they have fed, often crawling to others, and some- 

 times travelling several hundred feet from the starting point before 

 deciding to pupate. When they are ready for the change they spin 

 their whitish cocoon in any convenient place ; in the angles of 

 wooden tree boxes, under the rails of fences, in the interstices of bark 

 of the trees themselves, and in fact in any likely or unlikely place 

 except a perfectly Hat, smooth surface. The caterpillar has a very 

 small supply of silk only, and to eke this out uses its own hair 

 which it breaks off close to the body and forms the cocoon by a sort 

 of felting process, the silk serving to give form and holding together 

 the hair. In the cocoon the larvse change to dirty yellowish or 

 gray pupre, the male much smaller than the female and showing 

 rudiments of the future wings, while the female is nearly double the 

 size and is grub or slug-like in form. Less than two weeks there- 

 after the final change takes place and the adults emerge — the sexes 

 strikingly dissimilar in appearance. The male has two pairs of 

 broad dusty gray wings, the anteriors crossed by narrow black 

 lines, and with a more or less prominent white spot toward the 

 lower outer angle. The feelers or antennae are broadly feathered 

 and prominent, while the fore-legs are plumed and tufted, stretched 

 straight forwaixl when the moth is at rest, so as to be the most 

 conspicuous feature of the insect. The female, on the other hand, is 

 entirely without wings, and somewhat slug-like, consisting princi- 

 pally of an abdomen, which is enormously distended with eggs. 

 AVhen she emerges from the pupa, she crawls upon the cocoon to 

 which she clings, almost motionless for the balance of her life. 

 Egg-laving begins soon after impregnation, the eggs being laid upon 

 the old cocoon and covered with a frothy mass, which soon be- 

 comes bard and brittle and is snowy-white. As the eggs are laid, 

 the female diminishes in size, eventually shrinking almost into 

 nothingness and finally drops off dead. Neither male nor female 

 takes food in this stage, their adult existence is devoted merely to 

 reproduction. From the egg-masses above described, a second 

 brood of larvre hatches in July and the same life cycle is repeated, 

 the adults of this brood appearing in September. The eggs laid at 

 this time of life remain unhatched during the winter."^ 



It will be readily seen from this life history that the females 

 being wingless the species can only be distributed by the crawling 

 propensity of the caterpillar ; this, together with the fact that the 

 eggs are all laid in a mass, gives the key to the method of destroy- 

 ing them. Each egg-mass destroyed means the death of about three 



^Eept. Ent. Dep., N. J. Agric. Col. Exp. Station, 1894. 



