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Genus Acilius

Dytiscid - Acilius semisulcatus Another diving beetle - Acilius semisulcatus Acilius athabascae (Larson) - Acilius athabascae Dytiscidae - Acilius - female female diving beetle - Acilius confusus - female predacious diving beetle - Acilius semisulcatus - male Acilius  - Acilius - male Acilius (mediatus?) Diving Beetle - Acilius mediatus
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Coleoptera (Beetles)
Suborder Adephaga
Family Dytiscidae (Predaceous Diving Beetles)
Subfamily Dytiscinae
Tribe Aciliini
Genus Acilius
Synonyms and other taxonomic changes
revised in (1)
Explanation of Names
Acilius Leach 1817
7 spp. in our area, 13 total(2)(1)
adult 10-16 mm, larva 15-30 mm
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).
in Graphoderus elytra more heavily mottled/speckled, and dark transverse pronotal bands located apically
key to spp. in (1)
Holarctic, widespread (including the arctic)(1)
submergent vegetation
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(3)
Acilius confusus Bergsten described in 2006
Works Cited
1.Taxonomic revision of the Holarctic diving beetle genus Acilius Leach (Coleoptera: Dytiscidae)
Bergsten, Johannes & Miller, Kelly B. 2006. Systematic Entomology, 31: 145-197.
2.A World Catalogue of the Family Dytiscidae, or the Diving Beetles (Coleoptera, Adephaga)
Nilsson and Hajek. 2019. Distributed by authors.
3.Predaceous Diving Beetles (Coleoptera: Dytiscidae) of the Nearctic Region, with emphasis on the fauna of Canada and Alaska
D.J. Larson, Y. Alarie, and R.E. Roughley. 2001. NRC 43253.