APPLE-TREE CATERPILLAR THE YOUNG WORMS. 193 



At length driven to migrate elsewhere or perish from starvation, 

 they leave the tree, one following the track of another, travel- 

 ing in the direction in which they discern or suppose they dis- 

 cern other trees to be standing. If it is pasture land in which 

 they are traveling, every stalk of clover, every dandelion leaf 

 and other weed which they come to is examined to its summit 

 in search of something which is edible. I once saw a heap of 

 dry brush, every limb of which was overspread with the threads 

 of a swarm which was thus emigrating, so little ability have 

 they for discerning where food can be found. Their track may 

 commonly be traced through the grass by the threads which they 

 spin, to a distance of one or two rods, it gradually becoming 

 less distinct as one worm after another has strayed away from it, 

 impatient to find something wherewith to appease his hunger. 

 Being already famished before leaving the tree it is probable 

 that most of them perish before finding anything nutritious on 

 which to feed. The cherry puts forth a scanty crop of new 

 leaves after the worms have left it : and I have known trees to 

 be totally defoliated three and four years in succession by these 

 caterpillars, without being killed. But when thus assailed they 

 grow but little, if any, and acquire a decrepit appearance from 

 which they do not recover for several years. 



The larvae when they first come from the eggs are 0.08 long, slightly taper- 

 ing, of a black color, the under side and legs pallid, and they are slightly 

 clothed with soft gray hairs. After they commence feeding they show a pale 

 ring at each of the joints, and a faint pale stripe lengthwise along the back upon 

 each side of its middle, and another low down upon each side. The head is 

 deep black, and some deep black dots may be discovered upon the body, from 

 which the hairs arise. When they are a few days old and before the first 

 moulting, they have increased to double their original size, and show some 

 ash-gray or whitish lines more or less distincly, running lengthwise upon the 

 back and sides. 



A worm which I confined by itself cast its skin the first time on the 6th of 

 May, again on the 12th, a third time on the 15th, a fourth time on ttie 19th, and a 

 fifth time on the 28th, being now an inch long. I think it would not have 

 moulted again, but as it escaped from its confinement, a week after the last 

 date, I cannot be certain upon this point. 



Jlftcr the first moult this worm was 0.20 long, of a dark gray color with 

 two ashy-white lines along the back and two along each side, the space above 

 the upper lateral line having a large blackish spot on each segment. The 

 hind edges of the segments and the under side of the body was' also pale ash 



[Assembly, No 215.] 13 



