There are other long-horned beetles (Cerambycidæ) that are occasionally found breeding in the hickories, and among these may be named the Belted Chion (Chion cinctus), Tiger Goes (Goes tigrinus), Beautiful Goes (Goes pulchra), and the Orange Sawyer (Elaphidion inerme), but they are usually quite too rare to be considered as very destructive insects.
Hickory-bark borer (Scolytus 4-spinosus. Say).—Only once within my memory has this minute but destructive beetle appeared in any considerable numbers in my neighborhood, although I have occasionally received a few specimens from correspondents in various parts of the country, even as far west as the Pacific coast in Washington. This borer is a very small, cylindrical, dark brown beetle, about one-fifth of an inch or less in length, and one-sixteenth in diameter. The hind part of the body is quite blunt (truncate), the males having four short but distinct blunt spines, two on each side, projecting from the hind part of the abdomen, hence the name "4-spinosus." In the females these spines are absent, otherwise they closely resemble the males. These bark borers usually appear here in the Northern States the last of June or early in July, and both sexes attack hickory trees of all species, but appear to prefer the old and nearly mature trees to the young and small with thinner bark. After boring through the bark and reaching the soft cambium layer underneath, upon which these insects feed, the female cuts a vertical channel in this substance, of little over an inch in length.
[FIG. 72]. BURROWS OF HICKORY SCOLYTUS.
This burrow is a little larger than the diameter of her body, and along on both sides she deposits her eggs, to the number of ten to thirty, placing about an equal number on each side. When these eggs hatch, the young larvæ begin to feed on the soft material by which they are surrounded, making minute burrows at first, and at nearly right angles with the parent one; but as they increase in size they are forced to diverge, those above the center working upward, and those below downward, as shown in Fig. 72. These burrows enlarge as the grubs increase in size, as shown, most of them reaching their full development by the time cold weather sets in, but some do not cease feeding until spring, then pass to the pupal stage, and later to the perfect or beetle form, and from the extreme end of these burrows they bore a hole straight out to the surface, and are then ready to begin the cycle of life again, either on the tree from which they have emerged, or others near by. Some fifteen years ago I noticed that the leaves of some of the old hickory trees on my place were turning yellow prematurely, and upon examination I found the bark perforated with minute holes not larger than small bird shot, indicating the presence of the bark borer under consideration. Seven of the very largest and, presumably, the oldest, appeared to be affected, and these were immediately cut down and stripped of their bark, exposing the little grubs to the air and attacks of insect-eating birds. These trees appeared to have been infested for several years, as there was scarcely a spot on the surface of the wood that had not been scarified with this pest. Since the destruction of these trees I have not been troubled with bark borers, although there are still a number of very old and large hickories thriving in the same grove. The only remedy I can suggest is to cut down infested trees as soon as they are discovered, and also encourage the insect-eating birds to remain in and near the nut groves.
There are several other species of bark borers that occasionally attack hickories, one of these, the Chramesus icoriæ, Leconte, infests the small twigs, while another, the Sinoxylon basilare, say, after boring through the bark, continues its course far into the heartwood, showing a preference for this kind of food instead of the living tissues. These pests, however, are rarely constant, but very erratic, in their attacks, and while they may be rather abundant on a few or many trees a season or two, they then disappear, and not one may be seen for several decades.
The hickory-shuck worm (Grapholitha caryana. Fitch).—The parent of this pest is a minute moth of the family Tortricidæ, the small caterpillars mining and boring the green husks, and sometimes into the immature shell, causing the nuts to wither and drop off prematurely, although an occasional one may reach maturity, even in its scarified condition. This insect appears to be somewhat rare in the East, but very abundant some years in the West, where it is frequently destructive to the thick shellbark hickory and pecan. The first fresh specimens of the Nussbaumer Hybrid pecan nut (referred to on a preceding page) were so badly bored and scarified by this worm when received, that they would have been nearly or quite worthless for either planting or other purposes. As this insect attacks the nuts on the very largest trees in the forest and elsewhere, I cannot suggest any other remedy than to gather the immature and infested nuts as they fall, and burn them, with their contents.
Among the larger Lepidoptera (butterflies and moths) there are many species, the caterpillars of which occasionally feed on the leaves of the hickories, but not exclusively; consequently, they cannot be considered as the special enemies of this genus of trees. When they do attack them, it is as much due to accident as design. This is certainly true with the great Luna moth (Attacus luna) and the American silk worm (Telea polyphemus), and various species of the Catocala, as well as the Tent caterpillar (Clisiocampa sylvatica).
There is also a hickory-nut weevil, closely allied to the species infesting the chestnut; and while not quite as large, its habits are similar, and its ravages may be checked by the same or similar means. The grubs bore into the green nuts, causing some to fall before half-grown; others may remain in the nuts until they are ripe and gathered in the autumn; consequently, perforated hickory nuts are not at all rare, even on the stands of venders in our cities.