GIPSY MOTH WORK IN NEW ENGLAND. 21 
Service, has been appointed to take charge of the investigations along 
this line. The table given under t\\e " food-plant experiments" indi- 
cates in a general way the degree qf susceptibility to moth attack of 
some of our more common forest trees. Certain species, however, 
are of little commercial value, and it is desired to discourage their 
growth, as well as those that are particularly susceptible to gipsy- 
moth attack. In the case of valuable species that are susceptible to 
attack and for the growth of which a large portion of the infested region 
is favorable, the only step which can be taken is to determine whether 
or not they can be sufficiently protected from serious damage by 
associating with the less susceptible species in small proportions. Of 
course, the presence of these species may jeopardize the safety of the 
associated species which would otherwise be immmie. However, 
before abandoning these species careful experiments will be made to 
determine whether there are associations with which they can join with 
safety. 
The chief fact that reduces the liability of certain species of trees, 
particularly conifers, to gipsy-moth attack is that the very young cater- 
pillars do not feed upon them. Therefore, if there are present no trees 
or undergrowth upon which the young caterpillars will feed and thereby 
develop to a size which enables them to attack conifers or similarly 
susceptible species, they will not be attacked. Thus it appears that 
certain species can be grown pure or in exclusive association and be 
free from gipsy-moth attack. Any system of forest management 
should endeavor to produce in a given area only trees of commercial 
value, and the foregoing lists (pp. 14-15) indicate the most suitable 
species for selection. 
In converting a given stand of timber into one which shall be im- 
mune from gipsy-moth attack, the different classes of trees should be 
considered for removal in the following order: 
(1) Trees of naturally low commercial value and susceptible to 
gipsy-moth attack. 
(2) Trees of low commercial value on account of growing in un- 
favorable situations and susceptible to gipsy-moth attack. 
(3) Trees of commercial value, favorably situated, and subject to 
gipsy-moth attack. 
(4) Trees of naturally low commercial value, but not liable to 
gipsy-moth attack if properly associated. 
(5) Trees of low commercial value on account of growing in un- 
favorable situations and not liable to gipsy-moth attack. 
(6) Trees of commercial value favorably situated and not liable 
to gipsy-moth attack. 
Silvicultural conditions in the woods of the infested region are very 
poor. Through repeated fires and heavy and inconsiderate cutting, 
the growth of weed trees has been greatly favored and the growth of 
