BIOLOGY OF THE TERMITES OF THE EASTERN UNITED STATES. 23 
able to penetrate more rapidly to the heartwood and honeycomb the 
interior. 
Termites quickly disintegrate the wood of dead trees and stumps, 
which soon becomes converted to humus, the rapidity with which 
this is done depending on the relative resistance of the species of 
wood. This beneficial réle in nature, however, is offset by the enor- 
mous destruction they accomplish in rapidly rendering insect, fire, 
and disease killed timber unmerchantable and by the damage they 
inflict to the roots and trunks of injured living trees. Termites will 
infest the heartwood of living trees injured at the base by fire, dis- 
ease, or other insects (Pl. III), and sometimes in such trees they 
excavate upward, throughout the dead heartwood, longitudinal tun- 
nels, irregular in diameter, the sides of which are lined with earth 
mixed with excrement. These insects also infest the roots of living 
trees, finding ingress through abandoned burrows of the large, 
roundheaded (Prionid) borers. Sometimes they girdle young trees— 
forest-tree nursery stock, for example—eventually cutting the trees 
off near the ground, examination disclosing that the stems were 
honeycombed. ‘This is not necessarily due to the presence of dead 
wood near by, since termites will tunnel for long distances under- 
ground. While usually confining their work to moist or decaying 
timber or to vegetable material of any sort, and to books (Pl. IV) 
and papers that are somewhat moist, termites will attack seasoned, 
dry wood, provided there is access to moisture elsewhere; 1. e., they 
use moist frass and earth in extending the burrows, thus creating 
more favorable conditions. In the Southern States termites will 
infest the bark and outer layers of the wood of the base of yellow 
pines killed by barkbeetles before the foliage has all fallen; trees 
that have been killed in the spring and show reddish-brown needles 
and much fallen foliage being infested by the middle of August. 
Trees killed in the spring will also have the outer layers of wood of 
the base honeycombed by the following December. (Fig. 6.) The 
larger-celled, thin-walled spring wood is eaten away first, leaving the 
smaller-celled, harder summer wood uneaten. (Pl. V.) 
Where the heartwood is decayed in a standing living tree termites 
will work for a considerable distance above the ground, completely 
honeycombing the heartwood. In a living chestnut tree at Falls 
Church, Va., with the decayed heartwood exposed in a long scar, 
termites had infested the heartwood to a height of from 45 to 50 feet 
above the ground. The outer shell of living sapwood was intact. 
(Pl. VI.) 
Termites are quite effective in clearing fields of old snags and 
stumps, but this benefit is offset by the damage they do to posts and 
buildings. | 
62896°—Bull. 94, pt 2—15 

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