TWO INSECTS OF THE ORCHARD SNODGRASS. 487 



When an infested leaf is held to the light the body of the caterpillar 

 can be seen within the mine occupying a clear space at the larger end, 

 the smaller end being filled with a dark mass of granular material. 



Since the caterpillar's whole business at this stage of its life is to eat, 

 it has no affairs to take it outside of its abode in the leaf, and, since 

 it never cleans house, it has no need of either doors or windows. It 

 feeds along the edge of the ever widening larger end of its one room 

 and packs all undigested refuse into the smaller end, which accounts 

 for that dark granular mass just noted. As the caterpillar grows it 

 sheds its skin at least twice, and the discarded garments are thrown 

 into the common rubbish heap. 



By the time the larval shield-bearer has sated its appetite it has 

 constructed a mine from three-eighths to half an inch in length with 

 a widest diameter of about a quarter of an inch, though different 

 mines vary much in size and many are smaller than this. The cater- 

 pillar itself, when fullgrown, reaches a length of from one-tenth to 

 one-eighth of an inch. Its body is flattened, wide in front, tapering 

 toward the rear (pi. 1, F), and consists of 13 segments, with a small 

 head, usually more or less retracted into the large first one. The color 

 is blackish above and below, pale yellowish or orange along the sides. 

 The skin is roughened all over with microscopic rugosities, round or 

 oval in shape, but is naked except for a few minute hairs scattered 

 over its surface and a group of larger ones on the side of each seg- 

 ment. The creature has no legs, but on the back and venter of seg- 

 ments 2, 3, and 11 are pairs of colorless oval spots situated on soft 

 elevations, while on segments 6 to 9 there are similar transversely 

 elongate areas on the ventral surfaces only. The skin on all these 

 areas is thin and flexible, though covered with small oval thicken- 

 ings, and is capable of being puffed out and retracted in such a man- 

 ner as to suggest that these points act as adhesive disks, enabling the 

 caterpillar to retain its position between the two walls of its mine. 

 Those on the lower side of the body are used also as organs of pro- 

 gression, for as we have seen, the caterpillar eventually walks away 

 with the part of its mine it uses for a winter case. Thus the worm- 

 like creature, though legless, can not only maneuver about in its flat 

 dwelling, where legs might be an incumbrance, but, having attained 

 any desired position, is probably able to maintain itself there against 

 the swaying of the leaf by three pairs of adjustable hydraulic wedges. 

 To our imagination such a mode of life in a cell so small that the occu- 

 pant can but worm about on his stomach seems nothing short of medi- 

 eval torture; yet, pleasant or not from a human standpoint, there 

 is always plenty to eat, and if the supposed unfortunate is liberated 

 from his prison he starves to death from helplessness. 



The caterpillar's head is a delicate capsule, conical in outline as 

 seen from above or below, but very much flattened. The jaws are 



