4 BULLETIN 295, U. S. DEPARTMENT OF AGRICULTURE. 



were found empty pupa cases/' or "Empty chrysalids were found in 

 the pitch masses.'' 



Since no other pitch moth so seriously destructive to the trunks 

 of mature or nearly mature trees leaves the entire pupa shell 

 within the bark or the pitch which sheltered the immature insect, 

 its identity is quite easily determined. 



The eggs deposited in July appear to hatch within about two weeks. 

 During the latter part of August the young larva manifests its presence 

 in infested trees rather plainly by the mixture of coarse castings and 

 brown bark dust which is thrown out through the entrance and other 

 holes in the bark made by the larva. Unlike the larva? of the sesiid 

 pitch moths, the pine moth caterpillar does not work into the cam- 

 bium and stay there. Quite often, if not always, after attaining 

 nearly half its full growth, it leaves the place where it hatched and 

 drills into the tree tissues again at a spot which presumably suits it 

 better, not infrequently several feet away from the original spot. 

 To this migratory habit probably must be attributed the frequent 

 occurrence of but one larva in a wound, except in instances where the 

 work of woodpeckers accounts for their isolation. This assumption 

 seems to be supported by the fact that all such hermits when located 

 are developed well toward maturity. 



As the larva grows and the inactive season approaches, this pro- 

 miscuous gnawing of holes in the bark ceases. In no case even 

 where most of them remain where they first saw the light is migra- 

 tion resumed the following spring. In the spring each larva prepares 

 for pupation in its own individual tunnel, though under the same 

 space of infestation, by lining it with silky thread. Packard states * 

 that "the worm in July spins a whitish, thin, papery cocoon in the 

 mass of exuding pitch, which seems to act as a protection to both the 

 larva and the chrysalis." This applies to the insect in the East. 

 In the West the caterpillar of the pine pest restricts its weaving 

 operations before pupating to the above-mentioned lining of the 

 tunnel. Cocoons which answer Packard's description are frequently 

 found in these tunnels, but they are of a parasite which will be 

 referred to later. 



On approaching maturity, about the middle of June, the larva 

 grows sluggish and is found to be transformed into the chrysalis 

 within a few hours. When the moth has attained full development, 

 29 days from the time the pupa was formed and a year after the egg 

 was laid, it merely bursts the chrysalid skin, leaving the empty shell 

 within the tunnel, and pushes its way out through the very thin 

 pitch covering at the mouth of the tunnel. The period of pupation 

 in captivity under very varying temperatures and during all seasons 



1 Packard, \. S., Insects Injurious to Forest and Shade Trees 5th Rpt. U. S. Ent. Com., 955 p. (p. 

 731), 38 pi., 300 fig., 188G-1890. 



