Beetles 
2 99 
almost invisible from above. The larvae are white and footless little grubs 
with very strong jaws. The family includes 150 species in North America, and 
because of the recently awakened interest in forestry is now being given special 
attention by entomologists. The losses, by the death of trees and the rid¬ 
dling of timber, caused by these obscure little insects are enormous. Pinchot, 
chief of the United States Bureau of Forestry, has recently estimated the 
annual forest losses caused by insects to be $100,000,000, and most of the 
ravages are due to the Scolytidae. 
Among the most destructive genera are Dendroctonus and Tomicus, 
each with numerous species. They often work in the same tree. For 
example, the famous Monterey pines of California are attacked by Dendroc- 
Fig. 408.—Galleries in Monterey pine, with larvae, pupae, and adults of the engraver- 
beetle, Tomicus plastographus. (Natural size except the single beetle outside, 
which is enlarged three times.) 
tonus valens in the lower three or four feet of the trunk, as many as four 
hundred individuals (larvae, pupae, and adults) occurring in this limited 
space in badly infested trees, while above this zone on up to the top of the 
tree are the mines of Tomicus plastographus (Fig. 408), from thirty to forty 
pairs burrowing into each yard of trunk. It is plain that such a combined 
attack on a single tree means death to it. 
The ambrosia-beetles, including half a dozen genera and many species, 
