basement timbers of pine, oak, and chestnut in old houses. They 
are of no economic importance because the infested wood is al- 
ready more or less destroyed by decay organisms. 
FAMILY SILPHIDAE 
CARRION BEETLES 
Carrion beetles are mentioned here because they are so often 
seen on animal excrement or around the bodies of dead animals 
in the forest. Many of the more common species are brightly 
colored, and their bodies are usually soft and somewhat flattened. 
The larger and more conspicuous species belong to the genera 
Silpha and Nicrophorus. Several small species are also found 
under the bark of logs and dead trees where they probably act as 
scavengers. Agathidium oniscoides Palisot commonly occurs in 
the galleries of bark beetles in hardwoods. 
FAMILY HISTERIDAE 
HISTER BEETLES 
Hister beetles are rather small, sluggish, and hard-shelled. The 
body is often very flat and the wing covers are usually cut off 
square at the tip, exposing the last one or two segments of the 
abdomen. Many are shining black; others may be bronzed, 
greenish metallic or marked with red, yellow, or orange. The 
larvae are soft-bodied and sluggish and may be found in decaying 
organic matter, in fungi, or under the bark of trees. Those of 
Plegaderus spp. feed on the eggs and larvae of bark beetles. 
FAMILY BYRRHIDAE 
Members of this family are oval, convex beetles about 1 to 10 
mm. long. The head bends downward and is concealed from above, 
and the hind femora are wide and extended to the elytra. A few 
species live under the bark of trees, but the majority occur in 
sandy areas where they may be found under debris or at the roots 
of grass and trees. Several species of the genus byrrhus occasion- 
ally injure young trees in forest nurseries and plantations. Adults 
of this genus are about 5 to 10 mm. long, black and grayish in 
color, and densely covered with hairs. 
FAMILY PASSALIDAE 
PASSALID BEETLES 
Passalid beetles are better known by some people by other 
common names, such as betsey bugs, betsey beetles, bess bugs, and 
patent-leather beetles. Three species are known to occur in the 
United States, only one of which, the horned passalus, Popilius 
disjunctus (Ill.), is found in the eastern part. 
Horned passalus adults are large, shining black beetles, from 
30 to 40 mm. long. The plates of the antennal club are rigid and 
incapable of being opened or closed; there is a short, forward 
119 
