490 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1920. 



hairs on the lower side of the leaf. Had the leaf been inverted the 

 house might have fallen, though as a precaution against such an 

 emergency the caterpillar had already sewed the lower flap of the door 

 to the edge of the leaf. To test the efficiency of this anchorage I 

 gently poked the case out of the hole in the leaf. It dangled safely 

 in mid air, demonstrating that just this contingency had been pro- 

 vided against, except that ordinarily the wind would be the cause of 

 it and not some meddling entomologist. 



Another hour had gone by. During the next hour and a half the 

 caterpillar occupied herself with the weaving of a thin silk lining over 

 the inner walls of her future dwelling. I now put the hanging struc- 

 ture back into its frame and set the twig bearing the leaf before an 

 electric light, thinking that the coolness of the evening might interfere 

 with the worker's activity. In immediate response she poked her 

 head and thorax out of the door at the anchored end, grasped the 

 lower surface of the leaf with her ventral thoracic footpads and drew 

 the case out of its hole, letting it hang as before. But now the time to 

 be off had arrived. The tether was cut by a bite with the mandibles, 

 and with her fore parts protruded the caterpillar dragged her house a 

 short distance from the hole, when suddenly down went both house 

 and occupant — but at the end of a thread run out from the spinneret. 

 The drop had been planned deliberately and a new thread attached 

 to the leaf before the caterpillar relaxed her hold upon it. This hap- 

 pened at just 8 o'clock. Before the case landed on the table it was 

 caught on a leaf, then removed to a piece of twig and the latter placed 

 in a wide bottle. Here the caterpillar traveled about with her house 

 for about 15 minutes and then rested. It was not until after 5 o'clock 

 the following afternoon that she finally came to a permanent anchor- 

 age, selecting as a site the under side of the cork stopper to the bottle. 



During the first part of October one may see many of the shield- 

 bearer cases dangling from the apple twigs at the ends of long threads 

 (pi. 1, G, d), swinging about in all directions or blown out like kites 

 in the wind. Since walking is a very slow means of progression for 

 creatures without legs who must, moreover, carry their houses on 

 their backs, this aerial mode of travel is the more popular style. 

 When the case happens to land on a twig, it is first secured there by 

 a thread and then hauled off to some suitable place where it is made 

 fast for the winter. Most of the caterpillars observed did not go far 

 on foot. Their gait is slow, awkward, and laborious. With the head 

 and thorax out of the case door (pi. 1, /), the support is grasped by 

 the lower thoracic pads, a few strands of silk attached to the bark 

 by dabbing the point of the spinneret against it several times, then 

 by contracting the rear part of the body the case is pulled up over the 

 head and the anchoring threads are stuck to the lower flap of the 

 door. Again the traveler reaches out, dabs on some more silk, draws 

 the case up as before, and secures it in the new position. Since I 



