112 



THE FOREST TENT CATERPILLAR 



then splits open along the back, and the caterpillar crawls out, 

 clad in a new skin that had gradually been forming beneath 

 the old one. This skin-shedding process is called moulting: 

 it is the general way in which insects provide for increase in 

 size. Some of the cast skins are shown in Fig. 39. 



Wherever they go, these little larvas spin a silken thread 

 which marks their pathway, although the thread is so slender 

 that a single one is generally to be seen only through a lens, 

 but in places where the larvae congregate to rest when not feed- 

 ing, a habit that they have, it becomes quite noticeable. It is 

 especially so after moulting, for then one can often find on the 

 end of a forked twig such a miniature tent as is represented in 

 the picture on the title page of this bulletin, the cast skins 

 being intermingled with the silken threads. 



Soon after the first moult the caterpillars begin feeding 



again, eating, of course, 

 more and more of the foli- 

 age as they become larger. 

 A week or so later they 

 again moult, a process which 

 is repeated twice, thereaf- 

 ter, at similar intervals. At 

 the time of the later moults, 

 the caterpillars are in the 

 habit of congregating upon 

 the trunks or larger limbs 

 of the tree, often not far 

 from the ground. Beneath 

 the mass of larvae there is 

 an inconspicuous web, in 

 which the feet are more or 

 less entangled. The ap- 

 pearance of the caterpillars 

 at such times is well shown 

 in the photograph repro- 

 duced in Fig. 40. At the 

 end of about five weeks from the time of hatching from the 

 egg, the Forest Tent Caterpillars become full grown in this, 



Fig. 41. — Cocoons in Apple Leaves. 



