74 INSECTS AND HUMAN WELFARE 



of the gipsy moth in New England. Since this insect bids 

 fair to become one of the worst forest insects over a consid- 

 erable portion of North America, it may be worth while to 

 review its status, in regard to natural control by parasites, 

 in both Europe and America. It was first introduced into the 

 I'^nited States about 1868, in a little town near Boston where 

 it did not become sufficiently abundant to attract attention 

 for nearly twenty years. Since then it has spread very slowly, 

 but persistently, in spite of the various repressive measures 

 undertaken to prevent its multi]>lication and dissemination 

 (Fig. .34). At the present time it is the most abundant cater- 

 pillar feeding upon trees over a large part of its range, and 

 has caused unbelievable havoc in the woodlands of eastern 

 Massachusetts and contiguous territory. 



The slow rate of spread of the gipsy moth is in striking 

 contrast to that of the European cabbage butterfly which has 

 been cited on another page, and aside from the vigorous re- 

 pressive measures undertaken to delay its dispersion may 

 perhai)s be due to the inability of the adult female moths to 

 fly. On this account, aside from accidental transportation, 

 the species must depend upon the larva for migration, and, 

 when newly hatched from the egg, these are commonly blown 

 to considerable distances by the wind. Nevertheless, a 

 closely related European moth, the brown-tail moth {Ewproc- 

 iis chrysorrhcpa) first detected in 1897, at almost the same 

 place as the gipsy moth, has in twenty years encompassed 

 but little more territory. It is now distributed over a narrow 

 coastal strip scarcely over 100 miles in width from Cape Cod 

 northward through Maine in Canada. The slow movement 

 of these pests is gratifying from an economic standpoint, but 

 is of only temporary significance, as both are undoubtedly 

 destined to cross the entire continent, and to assume nation- 

 wide importance. The cause of the slow spread of the brown- 

 tail moth is not easily to be pointed out, as this species flies 

 readily and finds its favorite food plants widely distributed. 

 Several factors are undoubtedly concerned, relating to me- 

 teorological conditions, as well as the nomadic instincts of the 

 moths themselves. 



