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set out as seedlings twenty years ago. Scarcely a year has passed, since 

 tliey attained a considerable size, -that they have not been more or less 

 disfigured by having some of their branches stripped of their foliage by 

 these cateri)illars. Some seasons they have been so numerous that we 

 have thought it necessary to take measures for their destruction. They 

 are eminently gregarious and therefore easily controlled. They feed 

 side by side as closely together as they can stand, and when they are 

 young a whole brood of them can be taken from the tree by removing a 

 single compound leaf of the walnut. Later in the season, as we have 

 above described, they come down, every time they moult, and mass 

 themselves upon the trunk or large branches. As at this time they are 

 bound together bj^ web, they can be taken off en masse and consigned to 

 to the flames. 



They are, no doubt, kept largely in check by their natural enemies. 

 We have reared from them two large species of Ichneumon flies, the 

 OpMon mundum of Say, and another undetermined species. 



I have often seen flocks of blackbirds alight upon the trees infested by 

 these worms, but I was never near enough to determine whether they 

 fed upon them. But I have seen that efficient destroyer of the hairy cat- 

 erpillars, the American Cuckoo, in the act of devouring them. I observed 

 that it always siezed the insect by one extremity, probably the head, and 

 mashed it, by mumbling it between the tips of its mandibles for a time, 

 before swallowing it. In the article upon Tussock-moth, in my first 

 annual report, I described the manner in which I had seen the Cuckoo 

 shave off the tufts of hair upon the larva of this moth, before swallow- 

 ing it; but the larva of the Datana is but little hairy, especially pre- 

 viously to the last moult, and the only object that I can conceive the 

 bird to have, in crushing the heads of these worms, is to destroy their 

 vitality as nearly as possible. This is undoubtedly a wise precautionary 

 measure, since the presence in the stomach of two or three dozen im- 

 harmed and squirming cateri)illars could scarcely be compatible with 

 that repose after a hearty meal, which is generally supposed to be con- 

 ducive to digestion. 



