230 MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
going into the wood or into the bark to pupate. The thickness of the 
bark fr equently governs the position of the pupal cell. The presence 
of bark is necessary for the protection of the early stages of nearly all 
forms. Weoclytus caprea Say, N. acuminatus F., “ Hylotr upes bajulus, 
and certain species of Kbuwria and Smodicum are powder- -post-forms 
and spend but a small part or none of the larval period under the bark. 
Many roundheaded borers, as Prionus, Distenia, Tetraopes, and Mecas, 
are root feeders on the roots of living trees, shrubs, or herbaceous 
plants. One prionid, Homaesthesis, feeds on the roots of sod- forming 
grasses. 
A very characteristic mode of feeding is found among the twig gir- 
dlers and pruners. This pecuhar habit appears In Many unrelated 
genera of the family. The twigs are girdled either by the adult beetle, 
as Oncideres and Oberea, or by the larva. Some larvae (X ylotrechus 
quadrimaculatus Hald.) sever the branch about where the egg was laid, 
whereas others bore down the stem, gradually hollowing it and cutting 
off the twig at several places and finally entering the Toot to pupate. 
The manner in which the twigs are cut is characteristic of the dif- 
ferent species of borers and serves to identify them. 
A few forms, such as Desmocerus, are pith feeders in shrubby plants. 
Several forms among unrelated genera cause galls, as Saperda obliqua 
Say, in alder, Desmocerus piperi ‘Webb in elder, and Y ylotrechus aceris 
Fisher in red maple. The seeds of some plants are attacked by ceram- 
bycids and the dry, hard cones of Pinus attenuata frequently contain 
larvae of Paratimia. 
Just as the galleries of many species are characteristic, so is the 
boring dust or frass pushed aside by the larva in excavating its tunnels. 
Some forms produce fine, powdery frass, others flaky chips or long 
fibrous, excelsiorlike shreds. ‘These types of frass are usually charac- 
teristic of certain types of mandibles. The frass may be either 
plugged tightly behind the larva or pushed out and the burrows kept 
continually open. Some forms use the opening through which the 
frass is extruded to emerge as adults, but in most forms the adult and 
not the larva gnaws the exit hole. 
The pupal cells and the place of pupation in the bark, sapwood, or 
heartwood show endless variation. Many forms produce a simple oval 
cell and others an elongate curved cell, with curious trapdoor arrange- 
ments or peculiar wads plugging the exit. Some of the root-feeding 
forms make a pupal cell of earth firmly held together by a secretion. 
All these characteristics are just as distinctive of the species as are 
the anatomical features and are used to a large extent in keys and in the 
discussion of the various forms. 
The roundheaded borers can be distinguished from all other wood- 
boring larvae by a few prominent larval characters. They are always 
fleshy, thin-skinned, white or yellowish in appearance, and more or 
less cylindrical or slightly depressed i inform. ‘They may taper some- 
what posteriorly, but the anterior segments are never suddenly and 
conspicuously larger than the following segments, as with the flat- 
headed borers. They are never curved with the last segments curled 
up beneath, toward the head, as are the white grubs, nor are any found 
with the last segment developed into prolegs or gripping processes. 
Between each of the body segments are two overlapping, circular 
bands of skin which permit longitudinal expansion and contraction 
