32 OUR SHADE TREES AND THEIR INSECT DEFOLIATORS. 



maimer, instead of the narrow girdling* baud, had had the bark irregu- 

 larly removed for the extent of an inch or more. All these later falling 

 twigs showed the interval that had elapsed between the injury and the 

 fall, in that the roughened edges of the bark left by the gnawing had 

 healed over with the peculiar roughened aud rounded enlargement fol- 

 lowing the deposit of the reparative material under such conditions. 

 Some of the twigs gathered gave excellent illustration of the ascent of 

 the sap through the outer wood, and its return, after assimilation in the 

 leaves, through the inner bark. In one instance, where the leaves were 

 unusually large, the descending sap, arrested at the girdled point, had 

 built up structure in the tip until its diameter was more than double 

 that of the starved internode below, while the immediate point of the 

 arrest was quite enlarged from the material there deposited. 



"This peculiar attack did not extend to the other principal food- 

 plants of the Orgyia, as the horse-chestnut, maple, apple and plum, 

 nor would it be expected to occur in connection with growth and struct- 

 ure so different from that of the elm." 



Pupation. — Six days after the third molt a portion of the larvae spin? 

 up; all these produce male moths. The female caterpillars, which up 

 to this time have been undistinguishable from the male caterpillars, 

 undergo a fourth (and, as it appears from more recent experience, in 

 some instances even a fifth) molt and acquire twice the size of the 

 male caterpillar. This last, wheu full grown, measures about 20 milli- 

 meters in length. The cocoon spun by the male caterpillar is of whitish 

 or yellowish color and sufficiently thin to show the insect within. It 

 consists of two layers, the hairs of the tufts and brushes of the cater- 

 pillar being interwoven with the outer layer. The female cocoon is 

 correspondingly larger, of gray color, and much more solid and denser 

 than the male cocoon. The male chrysalis (Fig. 13 tf), which is soon 

 formed within the cocoon, is of brownish color, sometimes whitish on 

 the ventral side, and covered on the back and sides with fine white 

 hairs. The female chrysalis (Fig. 13c) is much larger than the male, 

 and otherwise (lifters, especially in lacking the wing-sheaths aud in hav- 

 ing on the three first segments after the head transverse, flattened pro- 

 tuberances composed of scales, which are much less visible in the male. 

 The duration of the pupa state is less than a fortnight. 



The Imago. — The male (Fig. 15) is a winged moth with feathery an- 

 tenna* and very hairy fore legs. The general color is ashy-gray, the front 

 wings being crossed by undulated bands of darker 

 shade, with two black markings on the outer edge 

 near the tip and a white spot on the inner edge also 

 near the tip. He may frequently be seen sitting on 

 the trunks of trees or on th£ shady side of houses, etc., 

 as he rests during the day, and flies only after dusk, 

 often being attracted by light. The female (Fig. 13a) 

 is totally different from the male in appearance and 

 -orcjyia icu- resembles a hairy worm rather than a moth, since she 

 tigma: male. possesses the merest rudiments of wings. She is of a 

 pale gray color, the antennae being short and not feathered, the legs 



