THE PINE INVESTIGATION. 



385 



similar to primary galleries except that they are excavated by 

 the adults in a preliminary attack on a healthy, living tree ap- 

 parently for the purpose of weakening its vitality, so that the 

 conditions will be more favorable 

 for the development of broods from 

 eggs deposited during a subsequent 

 attack by other examples of the 

 same species. These preliminary 

 galleries are usually filled with bor- 

 ings and sap, or if in coniferous 

 trees, by turpentine. If in suffici- 

 ent numbers, they cause a diseased 

 condition of the cambium and thus 

 check the growth of wood which re- 

 sults in the death of the tree. If 

 they are not in sufficient numbers 

 to bring about this result, they heal 

 over and do no further damage than 

 to cause slight blemishes or defects 

 in the wood. 



DISTRIBUTION OF SPECIES. 



The distribution of species in the 

 eastern United States, and especial- 

 ly in West Virginia, appears to be 

 governed large ly by the distribution 

 of the trees and plants they attack; 

 and with possibly a few exceptions 

 are not influenced by differences in 

 altitude and other conditions which 

 are known to effect the distribution 

 of many forms of life in this State. Two or three spruce bee- 

 tles, and one birch bark beetle appear to be confined to high 

 altitudes, or to what is termed the Canadian Life Zone; but 

 other spruce and pine infesting species appear to have a wide 

 range of distribution in the State. This is a feature however, 

 which demands further study in order to obtain anything like 

 an accurate knowledge of the influence of the several life areas 



Fig. L VII Hibernating gal- 

 leries of Tomicus in wood of 

 pine twigs, a Gallery of 

 Tomicus cacoyraphus, b Tom- 

 icus pini. 



