ANNUAL REPORTS. 265 



Shade Tree Insects. — In addition to the Brown-tail Moth 

 and Gypsy Moth mentioned above, there are numerous insect 

 enemies of New Hampshire shade trees about which Httle 

 seems to be known and which often require some treatment 

 for their control. The shade trees of New Hampshire are 

 one of its chief attractions and we therefore propose to make 

 a study of some of the more common injurious but little 

 known pests of our common shade trees. Among these have 

 been brought to our attention the mites which produce the 

 galls upon maple leaves (Bryophyes spp.) and also various 

 species of plant lice which affect the maple, birch, oak and 

 elm. Several of these have done considerable injury during 

 the past season, but we were unable to devote time to their 

 careful study. 



Hibernation of Insects. — The numbers of many kinds of 

 injurious insects are dependent upon the mortality of these 

 insects in hibernation during the winter. It is generally 

 known, therefore, that weather conditions during fall, win- 

 ter and spring often largely control the numbers of these 

 pests. The exact weather conditions which are conducive 

 to the multiplication or to the mortality of an insect are not, 

 however, definitely known and very little exact study has 

 been given to this important subject. During the past two 

 years we have made preliminary studies upon the relation of 

 temperature to the hibernation and time of emergence of 

 insects in the spring, especially with the Brown-tail Moth, 

 Apple Tree Tent Caterpillar and the Rusty Tussock Moth. 

 With more assistance and better equipment it is now possible 

 to prosecute this research more carefully, and during the 

 present and coming winters we expect to secure considerable 

 exact data concerning the immediate relation of the tem- 

 perature during the period of hibernation to the time of 

 emergence of insects in the spring, and also the relation of 

 low temperatures to their mortality, as well as the relation 

 of various temperatures to the time required for the various 

 stages in the transformation of insects. It is unnecessary 

 to point out the practical bearings of such investigations in 

 this place, but the fact that the daily press last winter widely 



