164 NEW YORK STATE MUSEUM 



since it is spreading rapidly in the adjacent commonwealth of Massachu- 

 setts. It is a serious enemy of fruit trees such as pear, apple, plum and 

 cherry and promises to be a dangerous forest and shade tree pest, since 

 it thrives on oak, maple and elm in the order named, stripping many trees 

 in infested sections. Not only is this species injurious because of its defo- 

 liating trees whenever abundant, but it is also very annoying to man, since 

 the hairs of the caterpillar are exceedingly irritating. This is so marked 

 that serious illness has resulted from persons being in the immediate 

 vicinity of large numbers of cocoons ; particularly is this likely to occur in 

 the case of those in delicate health. 



Description. The male moths have a wing spread of about i '4 inches, 

 are pure white with a satiny luster on the fore wings and have a conspicuous 

 reddish brown tuft at the tip of the abdomen. Sometimes there are a few 

 black spots on the fore wings. The antennae are white and fringed with 

 pale yellowish hairs. 



The females have a wing spread of about 1 3,/j^ inches, are the same 

 color as the males, except that they have no black spots on the wings, and 

 the anal tuft is larger and lighter in color, while the antennae are shorter 

 and with shorter fringes. 



The eggs, laid during July in masses composed of 200 to 300, are placed 

 usually on the underside of the leaves, where they are covered with brown 

 hairs from the tip of the abdomen. They hatch in a short time, and the 

 young feed during the rest of the season on the surface of the leaves, a few 

 days only being required to skeletonize them. The caterpillars begin to 

 make a nest in which they hibernate while still young. It is constructed on 

 the twigs and is made by drawing together a few leaves, lining them with 

 silk, and inclosing them with a mass of silken threads. These tents are so 

 firmly secured to the twigs that they can be removed only with considerable 

 force. 



The young caterpillars emerge from their winter retreats before the 

 leaves begin to appear, often attack swelling buds and complete their 

 growth in the early part of June, when they transform to pupae. The full 



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