Numbers
5 species in North America listed at
nearctica.com, but not the same 5 species listed in
Beetles of Canada and Alaska, which includes an additional species (
A. sylvanus) described by Hilsenhoff
Size
adult body length 10-16 mm
larva length 15-30 mm
Identification
Adult: top of head yellowish with two dark transverse bands, the anterior band undulate or shaped like an M or upside-down W; pronotum yellowish with two dark transverse bands on disc, not terminally, as in Graphoderus; notched spur on hind tibia; elytral mottling or speckling less pronounced than in Graphoderus; elytra punctate (and longitudinally sulcate in female)
Larva: swimming hairs present on last two abdominal segments; ligula (structure located between the maxillary palps) is deeply bifid (2-pronged).
Range
throughout North America, including the arctic
Season
Year-round with adults most frequently encountered in spring during mating season and late summer when they disperse to overwintering sites
Life Cycle
Adults have been reported to overwinter in permanent water bodies and disperse to breeding sites during spring; larvae complete development later in the spring and into the early summer; newly emerged adults disperse to overwintering sites later in the summer and into the fall
(1).
See Also
Graphoderus elytra more heavily mottled or speckled, and dark transverse bands located terminally on pronotum
Internet References
photos and species accounts of
A. fraternus and
A. mediatus (Charles Staines, Discover Life in America, dlia.org)
distribution in Canada; PDF doc of 5 species (D.J. Larson and R.E. Roughley, Dysticidae;
in Checklist of Beetles of Canada and Alaska)
live larva and adult images plus description and habitat (U. of Michigan)
pinned adult images of male and female
A. semisulcatus (Insects of Cedar Creek, U. of Minnesota)
