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Genus Ilybius

Black water beetle, Dytiscidae? - Ilybius Predacious Diving Beetle larva - Ilybius Predacious Diving Beetle larva - Ilybius Predaceous Diving Beetle - Ilybius fraterculus - female Predaceous Diving Beetle - Ilybius fraterculus - female Dytiscid - Ilybius oblitus ILybius erichsoni (Gemminger & Harold) - Ilybius erichsoni - male Ilybius vancouverensis (Leech) - Ilybius vancouverensis - male
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 Agabinae
Genus Ilybius
Synonyms and other taxonomic changes
NB: Recent revisions have now placed several Agabus spp. in Ilybius, incl. the A.erichsoni and A. opacus groups.(1) The following Nearctic Agabus species have now been transferred to Ilybius : A. erichsoni, A. gagates, A. larsoni, (preceding are in the erichsoni group), A. opacus, A. austrodiscors, A. confertus, A. discors, A. euryomus, A. hypomelas, A. jimzim, A. lineellus, A. vancouverensis, A. vandykei, A. verisimilis, A. walsinghami, and A. wasatjernae (all in the opacus group). See Nilsson (2001) for details.
Explanation of Names
Author of this genus is Erichson, who described it in 1832
Numbers
14 spp. in our area, 30 total (1)
Size
7-13 mm
Identification
Adults:
Notched eyes at antennal bases
Linear row of setae along ventral posterior-apical angle of hind femur
Unequal hind tarsal claws (vs subequal in Agabus)
Overall convex body outline
Usually dark/black in colour with lateral margins paler; many with a pair of subapical red spots on the elytra (with exceptions)
Males have slightly broadened front tarsal segments which bear ventral stalked oval yellow suckers; the last abdominal segment (sternum 6) is broadly rounded
Females have normal sized front tarsi with no suckers; Sternum 6 has a narrow medial notch on the hind margin
Species identification of adults relies mainly on technical features of the legs and ventral surface as well as elytron microsculpture and genitalia; colour is generally not a useful species diagnostic trait
Larvae:
2 whorls of hairs on the cerci (urogomphi)with or without secondary setae
no swimming hairs on tibia and tarsus
lateral margin of head with a horizontal keel and associated spines that run parallel to the keel (to the eyes) (1)
Range
from AK and the southern limits of the Arctic to so. US excluding most of the Gulf States (1) (holarctic genus)
Habitat
Mostly standing water with abundant emergent vegetation
Season
All year round but most often seen in spring and summer
Life Cycle
life cycle either univoltine (larvae overwinter and pupate in the spring, adults mate and lay eggs in the summer) or semivoltine (adults that emerged during the summer overwinter and lay eggs the following summer); the latter is most prevalent in the north, the former, in southern regions (1)
See Also