EXPERIMENT STATION BULLETINS. 597 



deal of variation both in the size and shape of these markings. In the 

 younger stages, some of the caterpillars are marked like the adults, 

 while others are unspotted. The worms feed in colonies or bunches, 

 each bunch occupying part of a limb and stripping it of leaves. 

 It is a curious fact that the worms of a single colony are usually marked 

 very much alike, being probably the offspring of a single parent, while 

 different colonies exhibit a good deal of variation. 



After the worms attained full size they descended to the ground and 

 spun very pretty cylindrical cocoons with rounded ends. In color these 

 cocoons varied from white to bronzed-brown, and in size from one-quarter 

 to three-eights of an inch in Jength. They are usually buried in the fallen 

 needles or in the grass under the tree. Fortunately, the great majority 

 of these cocoons are placed directly under the tree, although a certain 

 proportion of the larvae travel some distance before spinning. When 

 placed in breeding-cages and kept in a warm room, the adult saw-flies 

 (Fig. 27) commenced to emerge about November 8, and continued to 



Fig. 27. White-pine Saw-fly (Lophyrus lecontei); adult insect. (Original.) 



come out for over two weeks. Under natural conditions they remain in 

 the cocoon until spring, and then come out in great numbers. 



Some accounts of this insect describe the cocoons as attached to the 

 leaves of the pine. Specimens of cocoons thus placed were received from 

 Centreville, Mich., and these, as well as the accompanying larvae, were 

 indistinguishable from the cocoons and larvaa found here. 



This saw-fly usually has been considered as one-brooded, but its be- 

 havior in this instance would seem to indicate that it is double-brooded 

 and that the July larvne furnished the saw-flies that laid the eggs for 

 the more numerous fall brood. 



Fortunately, these worms are usually kept in check by parasites, but 

 when for some unknown cause the balance of life is disturbed and the 

 parasites suddenly decrease in number, we may expect a sudden appear- 

 ance of the pest and be driven to artificial means for the protection of 

 our parks and shade trees. 



