ENTOMOLOGY 291 



eter, and there are usually 400 to 500 eggs in a cluster, though occa- 

 sionally 1000 may be found in an egg mass. 



The young caterpillar is slightly over one-tenth of an inch 

 long just after it emerges from the egg. It has a black head, the 

 body is brownish yellow and well clothed with long hairs. There 

 is a prominent hairy tubercle on either side of the segment next the 

 head; this gives the caterpillar a peculiar broad-headed appearance, 

 especially in its early stages. The markings become plainer as it 

 increases in size, and when full grown it is from 2 to 2 1 / inches 

 long. This caterpillar has a double row of conspicuous warts or 

 tubercles down its back, the eight anterior blue, the 12 remaining 

 red, not counting the four blue ones just behind the head. Similar 

 tubercles also occur on the sides. 



The somewhat conical, dark brown pupa ranges from % to 

 1.1/2 inches long. It is usually found lying among a few threads 

 and securely attached to them by its terminal spine. 



The male and female moths differ markedly. The former, a 

 slender, olive brown, black-marked creature with feather-like an- 

 tennae and having a wing spread of about 1^ inches, may be seen 

 flying in the late afternoon and early evening in considerable num- 

 bers. The female is much heavier and lighter colored. She has a 

 wing spread of about 2 inches and is a white or buff white color 

 with more or less distinct black markings. The abdomen is tipped 

 with 'buff. The female moth does not fly though she apparently 

 has well developed wings. 



The winter is passed in the egg-mass, which is remarkably re- 

 sistant to atmospheric and other agencies. Experiments have 

 shown that even w r hen the egg clusters were broken up and freely 

 exposed to the elements, the eggs were apparently not harmed, and 

 a normal proportion of the caterpillars appeared at the usual time, 

 which, in the vicinity of Boston, is from the last of April until the 

 middle of June. The feeding period extends from the first of May 

 to about the middle of July, a caterpillar requiring from about 9 to 

 11 weeks to complete its growth and enter the pupal stage. The 

 young caterpillars remain on the egg clusters from one to five or 

 more days and then commence feeding on the leaf hairs. Soon 

 they eat out small holes in the leaves and, after the third or fourth 

 molt, about as many feed on the edge of the leaf as eat out holes. 

 The caterpillars are largely nocturnal, remaining in clusters on 

 limbs and trunks, or hiding in some crevice during the day, and 

 beginning between 7 and 8 o'clock in the evening leisurely to 

 ascend the tree, where they feed on the foliage at intervals during 

 the night, descending about 3 o'clock in the morning. 



The larvae transform to pupse during the month of June, the 

 moths appearing from the latter part of June till the latter part of 

 July. In exceptional cases these dates may be considerably ex- 

 tended. Males emerge in advance of the opposite sex, and shortly 

 afterwards the females appear, pairing takes place and egg deposi- 

 tion begins. The embryos are frequently well developed within 

 the egg in two or three weeks after oviposition, but as a rule the 



