Whirligig Beetles

Gyrinidae. Spanish: Mamatetas (Costa Rica, Dineutus).

Whirligigs skate and gyrate in groups on the water in stream eddies, in ponds, and at the edges of lakes. They are supremely adapted for life on the surface film with their flat, oval bodies, divided eyes, which enable them to see above and below simultaneously, and long forelegs, with which they snatch prey that has fallen into their paths. Their hind legs are not fringed with hairs but are flattened like oars and function as efficient propellers. All are solid black, some with metallic blue-green or coppery reflections, and varied in size (BL 2—15 mm). They are diurnally active. If frightened, they dive quickly and remain submerged for some time.

The larvae roam the bottom searching out and preying on a variety of other small aquatic invertebrates. They are long and slender and bear conspicuous featherlike gills on the sides and tip of the abdomen.

These common beetles are found almost everywhere in Latin America to about 42 degrees south latitude. The genera Gyretes (fig. 9.3g) and Gyrinus (fig. 9.3h) contain the majority of the approximately 340 species.

When threatened or handled, whirligigs many emit a fruity-smelling, liquid discharge. The secretion emanates from glands near the anus and contain nor-sesquiterpenes, chemicals shown to be toxic or to act as deterrents to fish and the common newt (Newhart and Mumma 1978).

For general information and a bibliography, see Bachmann (1977) and Spangler (1981, 1982).

References

Bachmann, A. D. 1977. Gyrinidae. In S. H. Hurlbert, ed., Biota acuática de Sudamérica austral. San Diego State Univ., San Diego. Pp. 227-231.

Newhart, A. T., and R. O. Mumma. 1978. High-pressure liquid chromatographic techniques for the separation and quantification of nor-sesquiterpenes from gyrinids. J. Chem. Ecol. 4: 503-510. Spangler, P. J. 1981. Gyrinidae. In S. H. Hurlbert, G. Rodriguez, and N. Dias dos Santos, eds., Aquatic biota of tropical South America. Pt. 1. Arthropoda. San Diego State Univ., San Diego. Pp. 155-163. Spangler, P. J. 1982. Gyrinidae. In S. H. Hurlbert and A. Villalobos Figueroa, eds.,

Aquatic biota of Mexico, Central America and the West Indies. San Diego State Univ San Diego. Pp. 349-355.

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