LIBRARY

COLEOPTERA 539
(Holarctic and Ethiopian); Copelatus Erichson, 196 spp. (cosmopolitan excepting
South America); Agabus Leach, 162 spp. (Holarctic); Hydrati'cu5
Leach, 104 app. (cosmopolitan); Dytiscus Linn., 27 spp. (Holarctic). D. circumfiexus
Fab. (Palrearctic) and D. marginalis Linn. (Holarctic) are two very
common species. Cybister Curtis, 64 spp., is cosmopolitan except for South
America. Several of the common species such as C. sugillatus Erichson and
C. tripunctatus (Olivier) are used by the Chinese for food and medicinal purposes.
Dried specimens can now be purchased in the Chinese stores in San
Francisco.
Eretes stictus Linn., a small ocherous species with black spots and punctures
on the dorsum, 10-14 mm. long, is gathered around the brackish ponds of India
as the larvre leave the water for pupation in the soil and as the newly emerged
adults seek the water. Both stages are used for food.
II. Superfamily GYRINOIDEA Leng 1920
Family GYRINIDlE Leach 1815, 1817 (Gy-rin'i-dre, from the Greek "flJpos,
round, circular movement; because of the gyrations of the adults on the
surface of the water). German, Kreiselkafer. French, Tourniquets.
Whirligig Beetles, Surface Swimmers.
Small to medium-sized, elongate-oval, convell:, smooth, shiny, active, aquatic
beetles which are usually black in color and gyrate with great speed upon the
surface of fresh water. The body is furnished with a lateral marginal keel
which "rides" on the surface of the water. Head small and somewhat triangular.
Antenna! short and thick: ll-segmented. Eyes large, divided so that upper
parts are above and the lower portions below the surface of the water. Legs
modified; the fore pair long, strong, and prehensile for grasping and holding
prey; fore tarsi of males dilated and with suckers. Middle and hind legs short
and paddle-like to propel the insects over the surface. Hind coxre rigid. Wings
developed in most forms. Abdomen with seven visible sternites. Larvre aquatic,
long, slender, flattened, with small head. well-developed legs, and a pair of
lateral, plumose tracheal gills on each abdominal segment, and an extra apical
pair on segment IX.
These beetles are familiar and interesting objects to all observers of nature
and constitute a distinct and easily recognized group. They are predacious
and air breathers but frequently dart to the bottom for rest and protection
only soon to arise and glide like a figure skater on the surface. They usually
occur in groups which may aggregate hundreds of individuals and prefer quiet,
shallow water for their activities although many species definitely prefer
streams and others ponds and lakes. The adults secrete an odor that is quite
pronounced. They fly readily at night, and some are attracted to lights. The
eggs are laid on objects in the water. The larVa! are predacious upon small
aquatic animals and breathe by means of gills. They pupate in flimsy cocoons
attached to rocks, sticks, water plants, and other objecj:s in the water. In size
they vary from the small European Gyrinus minutus Fab .• 3.5-4.5 mm. long,