APPLE-TREE CATERPILLAR DESTROYED BY PARASITES. 199 



The caterpillars which are seen wandering about, everywhere, 

 the fore part of June, all disappear by the middle of that month, 

 having wound themselves up in their cocoons. Straggling indi- 

 viduals, however, may be met with after this time. So late even 

 as the fourth of July, when the winged moths are generally out 

 of their cocoons, I have met with individual caterpillars still 

 lingering upon the leaves of apple trees. Several of these late 

 stragglers I have confined in boxes, deeming they might be infest- 

 ed with internal parasites. But in every instance they refused to 

 eat, and have died within a few days and their bodies have be- 

 come putrid, and no parasites were to be found within them 

 when examined. Hence it is probable that all these late indi- 

 viduals are diseased and too debilitated to spin cocoons, and that 

 they all perish. It will not therefore be worth while to give 

 any care in destroying them when we happen to meet with them. 



When the caterpillars disperse themselves abroad, a few re- 

 main upon the tree and continue to occupy the nest. These also 

 appear to be diseased individuals which are too feeble to roam 

 abroad like their comrades And they eventually form their 

 cocoons within the nest. Thus on tearing open old nests a few 

 cocoons will almost always be found in them. Some of these 

 yield winged moths, but the insects in most of them are destroyed 

 by parasites. There are probably different species of Ichneumon- 

 flies and kindred insects which prey upon and destroy the Lackey 

 moth in its larva and pupa state. Sometimes a very small white 

 cocoon not half the size of a grain of wheat, and of a texture like 

 that of the silk paper on which bank bills are printed, may be 

 found slightly attached to the outer surface of the cocoons of the 

 Lackey moth. The insects make their escape therefrom by cut- 

 ting one end of the cocoon nearly off and pushing it up like a 

 lid. These small cocoons are probably formed by parasitic 

 worms which feed upon and destroy the inmate of the larger 

 cocoon and make their way out of its body as soon as they have 

 attained their growth. 



Many of these cocoons which are found in the old nests of the 

 caterpillars have a large hole perforated in them near one end, 

 this perforation also extending through the shell of the chrysalis. 

 In July and the forepart of August a multitude of minute Chal- 



