Page:Popular Science Monthly Volume 68.djvu/218

214 the annual cycle of metamorphoses and emerges as a beetle of that generation about a year after the egg is hatched. The burrows are made by the strong horny jaws of the larvæ, which shred every particle of the wood in the course of the burrows, all of it passing through the intestinal canal of the larvae. Only the scanty protoplasmic contents of the wood cells, however, are digested for nourishment, and the dry refuse, resembling fine saw-dust, is packed behind the larva as it progresses in its burrow. The burrows are comparatively large and when numerous, as usually they are, they cut across the wood fiber so frequently that the trunk and larger branches are often completely riddled by them.

Such is the condition to which the wood of the black locust tree is habitually reduced by those insects and to which it is the special object of this article to call public attention. It is almost needless to add that such burrows render the wood useless for timber, of little value as fuel, and more subject to decay than is the uninjured wood. Many and various kinds of insects burrow in the dead wood of different kinds of lumber and fuel and thereby do much injury, but comparatively few species bore exclusively in living wood, and these are extremely injurious. The destructive borer of the locust tree and the smaller but hardly less destructive borer of the mezquite tree, already mentioned, are two of the best-known examples of the latter kind. Perhaps the best-known example of the former kind is the hickory wood borer, which householders often find in their fuel; especially that which has been felled in late winter or early spring. These borings in hickory wood are closely like those which are made in the living locust trees, and the locust and hickory borers are so nearly alike in appearance in all three of their metamorphoses that it is difficult for the ordinary observer to distinguish them apart. The hickory borer, however, burrows only in recently felled dead hickory wood, its incubation therein beginning in the spring; while the locust borer burrows only in the living wood, its incubation beginning in late summer and continuing until frosts prevail. This last-mentioned fact is important with reference to any remedies against the ravages of the locust borer that may be proposed. Hickory wood which is felled in autumn or early winter is likely to escape its borers by becoming too dry to serve their needs when they reach the beetle stage in the spring; but for the locust tree, after its sapling stage, there is no immunity from its borers so long as it lives.

Apparently there are several reasons why the ravages of the locust borer have largely escaped popular attention, such as the destruction of fruit and foliage by insects receives. The bark of the tree usually remains intact long after the wood beneath it is greatly injured. The small pits and punctures which are made in it by the female beetle for depositing her eggs are not ordinarily noticeable, and even the holes by