GYPSY AND BROWN-TAIL MOTHS AND THEIR CONTROL 15 



also a considerable mortality of newly hatched larvae during long 

 periods of rainy weather accompanied by low temperatures. 



Evaporation is another climatic factor that is known to influence 

 caterpillar activity. Feeding is noticeably greater when evaporation 

 is high, the loss of water from the caterpillar's body probably acting 

 as the stimulus. This may account for the more rapid feeding in the 

 upper part of the crown than in the lower part. Such feeding serves 

 to open the crown canopy, admitting more light, raising the tempera- 

 ture, permitting a freer circulation of air, and increasing the evapora- 

 tion rate below. Thus the entire crown becomes more and more 

 susceptible to rapid feeding. Young larvae seem to be attracted and 

 older larvae repelled by strong light. 



NATIVE ENEMIES 



No insect enemies of the gypsy moth native to New England cause 

 any noticeable reduction in its numbers. This is shown by the fact 

 that from 1900 to 1905, when no systematic effort was made to sup- 

 press the insect, alarming injury resulted, and native insect enemies 

 did not increase to any marked degree. The same is true of native 

 insect-eating birds, ^liile they undoubtedly feed to some extent on 

 gypsy moth caterpillars, there is no record of their being able to control 

 the insect. The "wilt," a disease that attacks and kills the cater- 

 pillars and pupae, has probably occurred in this country for many 

 years. During some seasons it kills an enormous number of the 

 caterpillars and is often an important factor in reducing the infesta- 

 tion locally. As a rule this disease is more common in heavy infesta- 

 tions, although many caterpillars have been killed by it when the 

 infestation has been relatively light. 



INTRODUCED PARASITES AND OTHER ENEMIES 



In 1905 the State of Massachusetts, in cooperation with the Bureau 

 of Entomology, began to introduce parasites and other natural enemies 

 of the gypsy moth from its native home in Europe and Japan. Since 

 that time a large quantity of parasitized material has been received, 

 and as a result some important natural enemies have become estab- 

 lished in this country and are assisting in the control of the pest. 

 The enemies which have become established, and which destroy the 

 largest number of gypsy moth caterpillars and pupae, are the beetle 

 Calosoma sycophanta L. ; two species of parasitic flies, Sturmia scutellata 

 R. D. and Compsilura concinnata Meig., one of which attacks the 

 caterpillars of the brown-tail moth as well as those of many native 

 insects; and a small wasplike fly, Apanteles melanoscelus Ratz. Two 

 tiny important parasites of gypsy moth eggs have also been estab- 

 lished, one, Oencyrtus kuvanae How., having been introduced from 

 Japan and the other, Anastatus disparis Ruschka, from Europe and 

 Japan. Two other introduced parasites, Hyposoter disparis Vier. 

 and Phorocera agilis R. D., are established in this country, but they 

 have not increased sufficiently to be important factors in gypsy 

 moth control. 



The work of the natural enemies of the gypsy moth has greatly 

 reduced the numbers of the insect. In some sections the reduction 

 has been greater than in others, and their effectiveness has also varied 

 from year to year. 



