This genus includes about 41 species in North America North of Mexico, and is widespread across eastern Noth America. Gyrinus includes most of the smaller species in the Gyrinidae family, while Dineutus contains the larger species. In order to deter predators, members of the genus Gyrinus often give off a foul smell and taste when disturbed. Adults and larvae prefer lotic-depositional habitats along the margins and pools of flowing water. Both larvae and adults are engulfing predators, and scavengers of small organisms, however, unlike the larvae, the adults usually hunt at the water’s surface.
Southeast: 6.3 and higher
Midwest: 3.6 and higher
Mid-Atlantic: 4 and higher
Engulfer / Predator
Widespread (east of the Rocky Mtns.)
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Order: Larvae: Usually without lateral abdominal gills. If gills present, then 4 hooks clustered on segment 10. Thoracic legs each usually with 4 or 5 segments and with 1 or 2 claws; if without legs, head distinctly sclerotized and posterior body (thorax and abdomen) simple, without gills, hair brushes, suckers, or breathing tube. Eye spots usually present, but compound eyes absent.
Family: Legs 5-segmented plus 2 tarsal claws. Abdominal segments 1–9 with lateral gills. Abdominal segment 10 (posterior-most segment) with 4 stout hooks.
Genus: Nasale (anterior most margin of the face) with 2-4 teeth measly along margin. Head elongate, with the collum (neck) nearly as wide as rest of head.