290 INSECTS OF MASSACHUSETTS. 



the " Insects of Massachusetts," I placed this moth, the impcri- 

 alis of Drury, in the genus Ccratocampa, from which, however, 

 it must be removed, on account of its very small feelers, and the 

 position of its wings ; and I now refer it, with some hesitation, to 

 the genus Dryocampa, with which it agrees so well in the moth 

 state, although its caterpillar differs a good deal from those of the 

 other insects of the same genus. The imperial moth, Dryocampa 

 imperialism has wings of a fine yellow color, thickly sprinkled with 

 purple-brown dots, with a large patch at the base, a small round 

 spot near the middle, and a wavy band towards the hinder margin 

 of each wing, of a light purple-brown color ; in the males there is 

 another purple-brown spot, covering nearly the whole of the outer 

 hind margin of the fore-wings, and united to the band near that 

 part ; the body is yellow, shaded with purple-brown on the back, 

 and with three spots of the same color on the thorax. It expands 

 from four inches and a half to more than five inches. In a variety 

 of this moth, of which I have a colored drawing done by Mr. 

 Abbot, the purple-brown color prevails so much as to cover the 

 wings, with the exception only of a large triangular yellow spot 

 contiguous to the front margin of each wing. This moth appears 

 here from the twelfth of June to the beginning of July, and then 

 lays its eggs on the button-wood tree. The caterpillars may be 

 found upon this tree, grown to their full size, between the twen- 

 tieth of August and the end of September, during which time 

 they descend from the trees to go into the ground. They are 

 then from three to four inches in length, and more than half an 

 inch in diameter, and, for the most part, of a green color, slightly 

 tinged with red on the back ; but many of them become more or 

 less tanned or swarthy, and are sometimes found entirely brown. 

 There are a few very short hairs thinly scattered over the body ; 

 the head and the legs are pale orange-colored ; the oval spiracles, 

 or breathing holes, on the sides, are large and white, encircled 

 with green ; on each of the rings, except the first, there are six 

 thorny knobs or hard and pointed warts of a yellow color, cov- 

 ered with short black prickles ; the two uppermost of these warts 

 on the top of the second and of the third rings are a quarter of an 

 inch or more in length, curved backwards like horns, and are of a 

 deeper yellow color than the rest ; the three triangular pieces on 



