﻿90 New York State College of Forestry 



which go into details of the life history or habits, have evidently 

 been based on limited material appearing in collections. 



It is not at all strange that specimens have been rare since the 

 species is adapted to life in a manner which precludes its frequent 

 collection. In the primitive forest or on all larger trees the insect 

 occurs probably only on the outer part of branches in the upper 

 ]^art of the tree, or at least far from easy capture by the entomolo- 

 gist. Only the fortunate occurrence of numerous young yellow 

 birch trees in a cut-over and burned tract at the State Forest 

 Camp has furnished the opportunity to note the mode of life and 

 stages of growth which apparently have escaped the attention of 

 entomologists up to the present. 



Life History 



While field observations have been limited to the summer months 

 and we are, of course, without ocular evidence concerning con- 

 ditions during the winter months, the fact that the active part of 

 its life cycle is practically completed between June 1 and Sep- 

 tember 1 makes it possible to detail the life cycle w4th entire 

 confidence. The remainder of the year from egg deposition in late 

 summer till egg hatching in late May must be passed in the egg 

 stage within the twigs of birch. The earliest date of egg hatching 

 is not known, but Dr. Drake has observed A'cry young nymphs, 

 evidently first instars, as early as May '-iO and nymphs of third 

 or fourth instar are found by July 1. The earliest adult female 

 noted in 1920 was July 13 and the first male July 16. So we may 

 conclude that the period of development from egg to adult is close 

 to six or seven weeks. The rate of growth is not entirely uniform 

 or else the eggs of different clusters hatch at different times as 

 nymphs of many sizes and different instars have been noted during 

 the first two weeks of July w'ith stragglers as late as the first 

 week in August and adults have been emerging from July 13 to 

 as late as the 29th. Adult females appeared July 16, but mating 

 activity was not noted until July 23. 



Emergence of adults from nymph case appears to come in the 

 early morning, such emergence being noted from the 17th to the 

 19th and between eight and ten. One individual, a male, which 

 was followed most closely, had split the nymph case along the 

 dorsal line of head and prothorax when observed at a little before 

 eight o'clock in the morning. It was attached to the underside of 

 the petiole of a leaf with the head toward the tip of the leaf and 

 in a position with reference to the twig which would place it 

 nearly head downward, attachment to petiole being entirely by 

 the tarsi of the nymphal case. The head, pronotum and base of 

 abdomen were exposed, as also the forelegs, and the wings were 

 out but scarcely longer than the wing pads, their tips being folded 

 under. The pronotum w-as no longer than in the last instar nymph 

 and did not expand until after expansion of the wings. In this 

 condition the insect remained fairly quiet for a time, as if resting 



