THE GIPSY MOTH AS A FOREST INSECT. IS 



mixed stands of oak and pine, birch and pine, oak and birch, etc., 

 were selected. 



A circle 100 feet in diameter was laid off around a central tree in 

 the midst of the forest selected, every tree included was numbered, 

 and notes were made covering its species, size, general condition, and 

 degree of infestation. The total number of egg masses to be found 

 ■v\athin the circle was recorded, and their increase or decrease from 

 year to year, together with the actual extent of injury resulting in 

 cases of bad infestation, was to be taken as the measure of resistance 

 offered by that particular type of forest. 



Although the work is not yet complete, the results already secured 

 are too pertinent and valuable to be reserved until its conclusion. 



Rather for convenience than because the proposed classification 

 is altogether natural the more common shade and forest trees of 

 New England may be separated into groups in accordance with their 

 susceptibility to injury. 



The first of these groups consists of those trees upon which the moth 

 following its establishment normally increases to the point of complete 

 or nearly complete defoliation. After the first defoliation the moth's 

 numbers may be very greatly reduced or they may remain practically 

 the same. In the one case one or more years may elapse before de- 

 foliation is repeated. In the other, the forest may be defoliated for 

 several years in succession. In either case the trees are likely to be 

 severely injured and to die. 



This group, so far as known, is composed exclusively of the various 

 oaks, with the possible but not proved exception of the shrubby 

 species. These may be considered as representing the most favored 

 food plants of the gipsy moth. 



The second group consists of those trees wliich appear to be espe- 

 cially favorable to the increase of the moth immediately follo\\'ing 

 its establishment. Almost always, however, at about the time when 

 defoliation would result were the colony to remain healthy, it receives 

 a setback. The trees are rarely completely stripped, and though they 

 may be from one-half to three-fourths defoliated for several successive 

 years, death rareh" follows. 



The most notable representatives of this group are several of the 

 tree willows and the gray birch. It is possible that some other trees 

 ^\-ill eventually be included; but none other so commonly encoun- 

 tered in the territory at present mfested by the gipsy moth wUl 

 compare directly ^^'ith bii-ch or willow. These, through the protec- 

 tion which they afford to incipient colonies of the gipsy moth, act 

 as incubators or breeders. 



In the tliii'd group are to be placed those trees upon which the 

 gipsy moth rarely increases to the extent usual upon gray birch or 

 willow. Upon some it will increase until a fair degree of infestation 



