6 BULLETIN 111, U. S. DEPARTMENT OF AGRICULTURE. 
It is evident that the entire girdling of about 0.5 per cent of the 
older infested trees is accomplished by more than one larva which 
happen to infest these trees at one and the same time. Each larva 
evidently tries to get as far away from its neighbor as it can, and 
thus the tree is girdled. But, as indicated, plural infestation is rare. 
To test this point experimentally the writer has several times planted 
in captivity two larvae on one piece of wood, and invariably one of 
them left the sustaining slab. On a few occasions when, because 
Fig. 3.— A lodgepole pine tree infested by the sequoia pitch moth. The new, flowerlike exudation 
indicates present infestation. (Original. ) 
none vacated, the writer supposed he had made a success of "double 
planting," he found later that one of the larvae was dead. 
Tunnels in trees infested only the second year, as well as those in 
trees that have been infested by several successive generations of the 
insect, look as if they had been engraved by the larvae eating the 
wood, but such is not the case. The appearance is caused by the 
larvae preventing the wood from forming a new layer across the 
tunnel. Thus the tunnel, in the course of many seasons, gradually 
becomes deeply embedded in the wood tissues. 
In rare cases the tunnel is slightly slanting, running on one side of 
the center, a few inches below the surface of the ground, while the end 
