82 INSECTS INJURIOUS TO VEGETATION. 



of the branch. Having reached its full size, which it does towards 

 the end of the summer, it divides the branch at the lower end of 

 its burrow, by gnawing away the wood transversely from within, 

 leaving only the ring of bark untouched. It then retires backwards, 

 stops up the end of its hole, near the transverse section, with 

 fibres of the wood, and awaits the fall of the branch, which is 

 usually broken off and precipitated to the ground by the autumnal 

 winds. The leaves of the oak are rarely shed before the branch 

 falls, and thus serve to break the shock. Branches of five or six 

 feet in length and an inch in diameter are thus severed by these 

 insects, a kind of pruning that must be injurious to the trees, and 

 should be guarded against if possible. By collecting the fallen 

 branches in the autumn, and burning them before the spring, we 

 prevent the development of the beetles, while we derive some 

 benefit from the branches as fuel. 



It is somewhat remarkable that, while the pine and fir tribes 

 rarely suffer to any extent from the depredations of caterpillars 

 and other leaf-eating insects, the resinous odor of these trees, 

 offensive as it is to such insects, does not prevent many kinds of 

 borers from burrowing into and destroying their trunks. Several 

 of the Capricorn-beetles, while in the grub state, live only in pine 

 and fir trees, or in timber of these kinds of wood. They belong 

 chiefly to the genus Callidium, a name of unknown or obscure 

 origin. Their antennae are of moderate length ; they have a 

 somewhat flattened body ; the head nods forwards, as in Stenoco- 

 rus ; the thorax is broad, nearly circular, and somewhat flattened 

 or indented above ; and the thighs are very slender next to the 

 body, but remarkably thick beyond the middle. The larvae are of 

 moderate length, more flattened than the grubs of the other Capri- 

 corn-beetles, have a very broad and horny head, small but power- 

 ful jaws, and are provided with six extremely small legs. They 

 undermine the bark, and perforate the wood in various directions, 

 often doing immense injury to the trees, and to new buildings, in 

 the lumber composing which they may happen to be concealed. 

 Their burrows are wide and not cylindrical, are very winding, 

 and are filled up with a kind of compact saw-dust as fast as the 

 insects advance. The larva state is said to continue two years, 

 during which period the insects cast their skins several times. 



