which castings are ejected and from which a small quantity of sap often flows. In some cases the borer burrows into the wood the first season, but usually it does not enter the wood until the succeeding spring. In small trees the galleries penetrate to the heart, but in old trees they are seldom extended more than an inch beneath the inner bark. The burrows in the wood, like those in the bark, are broad and irregular in shape and usually extend both above and below the surface of the ground. In the northern part of the insect's range a greater proportion of the feeding seems to take place beneath the ground. The writer found larvæ in Maine burrowing downward in the roots to a distance of a foot or more from the base of the trunk, a depth which does not seem to be reached in the South. Many 1-year-old larvæ were also found in Maine that had not yet penetrated into the wood but were still feeding in the bark near the old oviposition scars. In all their feeding larvæ keep an open space about themselves, to allow of free movement, but pack the balance of their burrows with wood fragments. Strings of reddish-brown castings are also thrown out from the tree through small openings in the bark. (Pl. V, C.) In the late summer and autumn preceding the spring during which pupation is to take place, the larvæ excavate galleries leading up the trunk of the tree a short distance beneath the bark. (Pl. VIII, A, B.) At the upper end of this gallery the pupal chamber is formed by slightly enlarging the circumference of the opening and curving the upper end outward to the inner bark. (Pl. VII, A.) The curved upper end is packed lightly with wood dust and a considerable space in the gallery below the pupal chamber is filled with short, excelsior-like strings of wood torn from the walls of the opening. (Pl. VIII, A.) The space for the pupa is often 2 inches or more in length and both the larvæ and pupa when occupying it recede or advance when disturbed, evidently a provision for escaping woodpeckers. The pupal quarters usually are practically completed in the autumn but the larvæ add finishing touches in the spring before they pupate. In small trees the exit holes at the upper end of the pupal chambers are usually within from 4 to 8 inches of the ground, but in large trees it is not unusual to find the place of exit at the terminus of a gallery extending upward from the ground to a distance of 18 inches or 2 feet. Just why the pupal quarters should be made higher in large trees than in small trees does not seem to have been determined. Wintering larvæ begin activities early in the spring and continue to feed until stopped by the cold weather of winter. Probably the annual feeding period in the South is much longer than in the North. A, Borer, first summer in tree. Natural size. B, Second summer in tree. Natural size. C, Cast ings being ejected from tree by borer. A, Young apple tree dying from injuries caused by roundheaded apple-tree borers. B, Trunk of young apple tree marked by beak of woodpeckers searching for borers; the larger wounds show where borers have been removed. C, Adult roundheaded apple-tree borers; male above and female below. Slightly enlarged. D, Borer in apple tree; showing cleared space maintained in burrow to allow of free movement of body. Natural size. |