Genus Dytiscus

dye-TISS-cuss

revised in (1)

Dytiscus Linnaeus 1758

12 spp. in our area (10 in Canada), 27 total(2)(3)

adults 22-40 mm, larvae up to 60 mm

Pronotum with or without pale borders. Elytra usually bordered with yellow. Pronotum and/or elytra of female variably smooth or grooved. Metatibiae much longer than broad, outer apical spur very thin. Protarsi of male have two large disks (and small disks) used to grasp female during mating. Hind legs move synchronously while swimming; adults often attracted to light.

Larvae with prominent cerci and dense lateral fringes of hair on the last 2 abdominal segments and cerci. The anterior portion of the head is rounded.

Holarctic; throughout NA(4)

permanent or temporary freshwater ponds and pools (D. marginicollis may occur in saline ponds), plus streams and rivers; usually found on or among aquatic plants

adults fly from March to November (varies by species)

fish larvae, mosquito larvae, other aquatic invertebrates, sometimes tadpoles and salamanders

one generation per year; mating occurs in late fall and/or early spring; eggs injected singly into underwater plant stems; fully-grown larvae creep out of water and pupate in moist earth, then emerge as adults in about a week and return to water; overwinters as an adult in permanent waters (D. hybridus may overwinter on land)

Cybister • Hydrophilus