LIBRARY

538
COLLEGE ENTOMOLOGY
readiness for a quick getaway. They also hide in the mud or under debris on
the bottom and cling to water plants. At night they may swarm over the land
in quest of new water and often gather about strong lights. They are also at·
tracted to bright tin roofs and automobiles. Adults are able to live on land for
long periods, and innumerable specimens have been observed under stones in
the bottom of dried pools and stream beds. Running and standing fresh water
and rarely brackish water are inhabited, including thermal and rarely subterranean
springs. 1 The eggs are laid in masses or separately on objects in the
water or they may be. inserted in the tissues of aquatic plants. The larvre live
a free and hunting life and because of their ferociousness are called water tigers.
A B c
FIG. 181. The European predacious diving beetle. Dytisclls morgitlolis Linn .• in cells in the
ground. A. larva: B. pupa and cast larval skin; C, adult and cast pupal skin. (Drawn from
phot(ls by Hugh Main. 1934.)
They leave the water when mature and excavate a cell in the earth above the
water line in which to pupate, the pupre being terrestrial. In size the adults
vary from the small black and gold European CceZambus confluens (Fab.) ,
2.5-3.0 mm., to Dytiscus latissimus Linn., the largest European species which
is 36-44 rum. long.
The family contains about 90 genera and 2,050 species which are chiefly
Holarctic although representatives are to be found throughout the world.
The members are closely related to the predacious ground beetles of the family
CARABIDJE.
The important genera are Canthydrus Sharp, 80 spp. (cosmopolitan excepting
Australia); Laccophilus Leach, 167 spp. (cosmopolitan); Hyphydrus IlUger,
53 spp. (Palrearctic, Ethiopian, Indo-Malaysian, Australian); Bidessus Sharp,
200 spp. (cosmopolitan); Hydroporus Clairville, 181 spp. (HoI arctic, Neotropical,
Australian). H. marginatu5 Duft and H. melanarius Strum are European,
and H. melanocephalus Marsham is Holarctic. Deronectes Sharp, 72 spp.
1 Certain members of the'Palrearctic genUs SieltiUa A. de Perrin are blind and inhabitors of
subterranean springs.