REPORT OF THE STATE ENTOMOLOGIST 1902 97 



habits to a greater degree than when they are very abundant, 

 since in this case the supply of food is soon exhausted and 

 they are forced to migrate. When these caterpillars molt, they 

 gather in masses on the branches and cover themselves with a 

 scanty mass of silk. When preparing to change to the pupal 

 stage, several of the caterpillars spin up in a common cocoon 

 within the leaves at the tip of the branches. When numerous, 

 they frequently pupate in masses under fences and clapboards, 

 or on the trunks and larger branches of the trees. 



The webs of the brown tail moth should not be confounded 

 with those of the tent caterpillar or the fall web worm. They 

 may be distinguished from those of the tent caterpillar by being 

 placed at the tips of the branches, while the tent caterpillar con 

 structs its tent in a fork of the limbs. The latter insect rarely, 

 if ever, attacks pear, which is a favorite food plant of the brown 

 tail moth. The fall webworm, while often found on peartrees, 

 spins a large open web at the ends of the branches and feeds 

 within this web. This insect does not appear until after the 

 brown tail moth has ceased to do damage. 



Food plants. This species has been recorded on a considerable 

 number of food plants, but, according to Professor Fernald, pear 

 seems to be the favorite of this insect in the infested region, 

 though winter webs have been found in addition on apple, quince, 

 plum, cherry, peach, oak, maple, elm, rose and grape. 



Irritation caused by the hairs. This has been referred to above ; 

 and, as there stated, is frequently very severe and annoying. 

 Investigations by Mr F. J. Smith show that the trouble is a 

 mechanical one, and is not, as at first was supposed, due to any 

 poisonous irritant substance in the hairs. The nettling of the 

 skin may be caused by contact with the caterpillars, both old 

 or young, or the cocoons, though in the latter case contact is not 

 necessary since hairs from them are blown about by the winds. 

 Professor Fernald cites the statement of an English journal to 

 the effect that travelers are often affected, when the wind blows 

 strongly from infested hedges along the road. 



Natural enemies. A number of parasites have been bred from 

 the pupae in this country. Professor Fernald records the rearing 

 of Phaeogenes hebe Cress., Diglochis omnivora 

 Walk., Euphorocera claripennis Macq. and a large 

 number of unnamed dipterous parasites. He states that the 

 work of Diglochis is specially valuable and worthy of commen- 



