186 MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
Adelocera discoidea (Web.) and A. aurorata Say in pine, A. avita 
Say and Hemicrepidius bilobatus (Say) im hickory, as well as Chalco- 
lepidius spp. are also predaceous on wood borers. Several species of 
EHlater are common under bark of dead and dying trees. 
Faminirs MELASIDAE and TRIXAGIDAE 
The Cross-Wood Borers 
The cross-wood borers resemble the Elateridae but lack their power 
to spring, although they are very active and difficult to catch and hold. 
They are most remarkable, however, because of the peculiar modifica- 
tion of larval characters, particularly a reduction of the mouth parts 
and mandibles and the development of sawlike teeth or keels on the 
side of the head for cutting the wood by a rasping movement. The 
larvae are elongate, parallel, much depressed, legless forms (except 
Trixagus= (Throscus) ) with rudimentary mouth parts. The labrum 
and clypeus are formed into the nasale, and usually the mandibles are 
immobile. The thorax is often enlarged like that of the buprestids 
and bears strongly chitinized markings or T-like rods, and the ninth 
abdominal segment is formed into a broad dentate plate or bears a 
pair of spines. 
The larvae of many species cut characteristic mines across the grain 
of the wood, which readily distinguishes their work. In the pupal 
cell they double up on themselves like buprestids. Certain forms with 
greatly reduced mouth parts can feed only by imbibing the liquids 
from the medium in which they are boring. In some forms the adults 
bore into the wood to make egg tunnels similar to those of the scolytids 
and some bostrichids. They are interesting forms but of little eco- 
nomic importance in the eastern part of the > United States, confining 
their attack to dead, often somewhat rotted wood. 
Melasis pectinicornis Melsh. Lsorhipis ruficornis (Say), and Fornaa 
badius (Melsh.) feed in beech, chestnut, hickory, maple, tulip, iron- 
wood, sweetgum, pine, and other hardwoods, the wood of which is 
fairly firm, while 7rivagus constrictor Say is found in moist logs on 
the ground. Drapetes geminatus (Say) is common in dead hickories, 
killed by the hickory bark beetle. Dirhaqus Dea (Lec.) has 
been reared from sycamore; Vematodes astropos (Say) from oak, and 
Promaeolus striatus (Lee.) from chestnut and pine, although they are 
not very abundant. For notes on the biology of this family see Van 
Horn (42/) and Kirk (266). 
Faminty RHIPICERIDAE 
Of the family Rhipiceridae, Zenoa picea (Beauv.), a rare species, 1s 
mentioned because of its peculiar larva which mines in dead hardwood 
logs. This larva is an elongate, cylindrical, darkly chitinized form 
resembling some elaterids but with the head more globular and the 
ninth abdominal segment ending bluntly im an operculum enclosing 
the tenth segment. The adult is a robust, dark-reddish-brown beetle, 
with serrate antennae. 
