492 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1920. 



After the molt the discarded skin is shoved off to one side of the 

 room and the caterpillar proceeds to improve its inherited domicile 

 by putting in a new silk lining. This, when finished, makes a closed 

 inner chamber which fits the caterpillar's present size much more 

 snugly than did the dimensions of the original case. Beneath the 

 eaves of the latter there is now an empty closetlike space on each side, 

 in one of which are stored the old summer clothes. 



Out in the orchard in late fall and all through the winter the tiny 

 yellowish cases may be found stuck about most anywhere on the twigs 

 and branches of the trees or even down against the trunks and on the 

 bases of the larger limbs. Most lie flat against the bark, some are 

 pendent, a few stand on edge, and an occasional one sticks straight up. 

 On windy days they flap from side to side, whirl about on the pivot 

 of their anchorage, or are set into a rapid and continuous vibration. 

 By spring the occupant has been put through a test of equilibrium 

 such as few aspirants for aviation could endure, but its functions 

 have been in no way upset. 



The cases vary somewhat both in size and shape, some being much 

 broader than others in proportion to their length. The larger ones 

 measure about 4 by 2| millimeters, the smaller 3 by If, the varia- 

 tion in width being greater than that of the length. The side formed 

 from the under surface of the leaf, which usually retains some of the 

 original leaf hairs, is flat or a little concave, while the other bulges 

 out, especially along the middle. This difference of the two sides ap- 

 pears to be due to unequal shrinkage of the two leaf layers, since both 

 were of the same size when newly cut out. 



If nothing happens to interfere with the course of its normal life, 

 the hibernating caterpillar will survive in its case all vicissitudes of 

 winter weather, and in spring, about the end of April in southern 

 New England, will change to the chrysalis stage or pupa, finally 

 casting off its larval skin. The pupa (pi. 1, B) is also a soft creature, 

 of a pale yellowish color, which becomes brownish on the fore parts 

 and on the areas covering the future legs and wings. During the 

 next month the moth develops within the pupa and, when all is 

 ready for its emergence, the pupa penetrates the silk wall of its 

 chamber, squirms through the door at the free end of the case, and 

 hangs out over the threshold, with two-thirds of its body in the air. 

 Then its skin breaks at the head end and the moth emerges, leaving 

 the empty pupal shell sticking in the vestibule of the now deserted 

 case (A). 



The arrival of the moth means that the cycle of the insect's life 

 has been again successfully accomplished. But in nature few of the 

 little cases cut out and hung up with such care and labor by the cater- 

 pillars are. destined to give forth moths in the spring. After spend- 

 ing almost their entire existence under cover, either in the mines or in 



