No. 4.] THE GYPSY MOTH. 309 



centres of population. These centres are settled largely by small 

 householders. Flower, fruit and vegetable gardens and small 

 orchards are abundant. The difficulty of carrying on destructive 

 work to good advantage in such localities is evident. 



Circumstances which Favor Plans for Extermination. 



1. The most important and favorable circumstance of all is that 

 the moth is apparently confined to a limited area. 



2. The location of the infested territory. The eastern and 

 a large portion of the southern part of the infested territory' is 

 bounded by the sea. This prevents all danger of the spreading of 

 the moth in these directions. The territory most infested is fre- 

 quently crossed by tidal rivers, which form a perfect barrier to 

 migratious of the insects, except where they can cross the streams 

 on bridges. A large part of the territory along the coast con- 

 sists of salt marsh, and in this the gypsy moth has not been found, 

 and probably could hot live. 



3. The moth was imported more than twenty-one years ago, and 

 has now been found in less than thirty towns. This shows that it 

 has not spread rapidly. 



4. Travel and traffic in the infested territory moves largely to 

 and from Boston. The business portion of Boston offers very little 

 sustenance to leaf -eaters. 



5. There are almost no exports by sea from this district, and 

 the chances of the insect being distributed by the coast trade are 

 therefore very few. 



There are certain known habits of the gypsy moth which may be 

 taken advantage of in making plans for its destruction : — 



1 . The female does not fly except diagonally downward ; this 

 greatly lessons the risk of spreading. 



2. Where there are few moths, and food is abundant, they are 

 likely to remain in the same locality. 



3. The gypsy moth passes the winter in the egg, and remains 

 in this form during the greater part of the fall, winter and earl}' 

 spring. At this time, when the foliage has fallen from deciduous 

 trees, the eggs may be destroyed. 



4. In the outlying districts, where the insects are few, the 

 eggs are found almost entirely upon a few species of trees. Thus, 

 if their numbers are greatly reduced, it is probable that they, 

 like many other insects, will select as food certain trees and 

 shrubs, and can be found and destroyed with comparative ease. 



A cai'eful weighing of the circumstances favorable to extermin- 

 ation, and those which appear unfavorable, leads to the conclusion 

 that the greatest difficulty is experienced after tin; caterpillar is 



