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Genus Bidessonotus

Dytiscidae, Hydroporinae, but what genus? - Bidessonotus Bidessonotus inconspicuous (LeConte) - Bidessonotus tiny Hydroporinae - Bidessonotus tiny Hydroporinae - Bidessonotus Bidessonotus - female Dystiscid - Bidessonotus Bidessonotus inconspicuus (LeConte) - Bidessonotus inconspicuus Diver #28 - Bidessonotus
Classification
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Coleoptera (Beetles)
Suborder Adephaga (Ground and Water Beetles)
Family Dytiscidae (Predaceous Diving Beetles)
Subfamily Hydroporinae
Tribe Bidessini
Genus Bidessonotus
Numbers
4 species in North America listed at nearctica.com
2 species in Canada
Size
adult body length 1.7-2.4 mm
Identification
Adult: scutellum covered (hidden) by pronotum; fore and mid tarsi 5-segmented, with fourth segment small but not concealed by lobes of third segment; hind tibia slightly arcuate; hind tarsus with 2 equal claws; pronotum and base of elytra with plicae (longitudinal grooves or impressions)
sexually dimorphic: female stouter than male and has preapical "tooth" on outer margin of each elytron

In B. longovalis, elytral plicae are distinctly longer than pronotal plicae.
In other species, females are identifiable only by association with males, and males are identified by differences in genitalic structure (i.e. in inconspicuus, the aedeagus has a smooth "toe" portion, and its "heel" is not distinctly produced, whereas in pulicarius the aedeagus has a rounded projection on the "toe" portion, and its "heel" is distinctly produced - see pg. 54 in PDF doc by Epler) and in some cases by size (inconspicuus: 1.7-2.2+ mm; pulicarius: 1.7-2.0 mm)
Range
Nova Scotia to Florida, west to Ontario and Texas, south into Mexico
B. inconspicuus and pulicarius are the only species in the northeastern United States and southeastern Canada
Habitat
ditches, ponds, streams, woodland pools; adults are attracted to light
See Also
in Anodocheilus, each elytron has longitudinal carina (keel) running almost to apex
Internet References
preserved adult image of B. inconspicuus, plus description, distribution, habitat, references (Charles Staines, Discover Life in America, dlia.org)
presence in Florida; list of 3 species (Michael Thomas, Florida State Collection of Arthropods)
presence in North Carolina; list of 3 species, with number of pinned specimens (North Carolina State U.)
presence in Ontario of B. inconspicuus and B. pulicarius (NHIC; Ontario Ministry of Natural Resources)
presence in Michigan of B. inconspicuus (U. of Michgian)
Water Beetles of Florida; PDF doc [9 MB] illustrated keys to genera and species in Florida; all pages are photos, so a text search is not possible (J.H. Epler, Florida Dept. of Environmental Protection)