26 o 
Beetles 
About one hundred and fifty species of Hydrophilidae are known in this 
country. The largest species belong to the genus Hydrophilus, are shining 
bluish or greenish black, and measure nearly two inches in length. “In the 
genus Hydrocharis the metasternum is prolonged somewhat, but does not 
form a long, sharp spine as in Hydrophilus and Tropisternus, and the sternum 
of the prothorax bears a keel-shaped projection. Our most common species 
is Hydrocharis obtusatus; this measures about five-eighths of an inch in 
length. 
“ Some of the smaller species of this family are not aquatic, but live in 
moist earth and in the dung of cattle, where, it is said, they feed on dipterous 
larvae.” 
The rove-beetles, Staphylinidae, form a large family, numerous in species 
and individuals over the whole country, and one whose members are readily 
recognized by the elongate flattened soft body, narrow and parallel sides, 
with short truncate leathery elytra under which the hind 
wings are compactly folded so as to be wholly concealed. 
They are mostly carrion-feeders and with the Silphidae 
(p. 261) are almost sure to be found whenever a mass of 
decaying flesh or excrementitious matter exposed on the 
ground is turned over. They run swiftly when disturbed 
and curve the tip of the flexible abdomen up over the 
body in a sort of threatening way, as if they would sting. 
They cannot; they can simply smell bad. Although the 
more familiar rove-beetles are of fair size, from half an 
inch to nearly an inch long, the majority of the one 
thousand or more species found in this country—9000 
species are known in the world—are very small. In 
Fig - 355 - Larva California great swarms of minute rove-beetles dance in 
of a rove-beetle, . . . . 
Xanthalinus the air m April and May, and are a worn! nuisance to 
lentus. (After people driving or bicycling. They get into one’s eyes, 
natural size^ 1CG and when crushed by rubbing, their acrid body-fluids 
both smell bad and burn. Among these smaller Sta- 
phylinids are numerous predaceous species and many which are found in 
flowers, probably feeding on pollen. Others are found on fungi, on mud, 
and in other damp places, and some live in ants’ nests (see Chapter 
XV, p. 552). 
The larvae (Fig. 355) are found in the same places as the adults, and 
are elongate, narrow-bodied, and rather like those of the Carabidae, but 
each foot has but a. single claw. The pupae of some species are enclosed 
in a sort of exudation that dries into a firm protecting coating rather like 
the horny cuticle of a lepidopterous chrysalid. 
Among the more familiar rove-beetles are species of the genus Creophilus. 
