22 



FIELD WORK AGAINST GIPSY AND BROWN-TAIL MOTHS. 



by silk spun by the caterpillars. As the season advances more 

 leaves are drawn into the web, and this is lined with silk and serves 

 during the winter as a hibernaculum for the larva?. The caterpillars 

 do not remain in a single large cell. The web is divided by cross 

 partitions into small pockets in each of which one or more of the 

 larvae remain during the winter. The webs (fig. 4) are very con- 

 spicuous on the trees during the winter, as they are usually located 

 at the tips of the branches. (See fig. 5.) During the first warm 

 days of spring the caterpillars come forth from the webs and begin 

 feeding on the bursting buds. In cases where the trees are badly 

 infested the tiny leaves are devoured as fast as they develop. The 

 caterpillars feed until about the 20th of June before becoming full 

 grown. They molt four or five times in the spring, and when ready 



Fig. 4.— Winter webs of the brown-tail moth ( Evproctis duyborrhaa). (Original.) 



to spin their cocoons are about an inch and a half in length. The 

 body is nearly black and cohered with rows of yellow spines and 

 barbed hairs which arise in tufts on the back and sides. There is 

 also a row of nearly white tufts on the full-grown larvae, which arise 

 along each side of the dorsal abdominal segments. The next to the 

 last two segments each bear a small coral-red tubercle on the dorsal 

 part. As soon as the caterpillars are full-fed they seek shelter and 

 spin up loose cocoons, within which they pupate. 



THE PUP.E. 



The cocoons (PI. IV, fig. 1) may often be found in leaves which 

 have been webbed together by the larvae, in crevices in the bark, 



