Cyclops bicuspidatus

Cyclops bicuspidatus -- now considered a member of the genus Diacyclops—is a species of copepod found throughout the world, except Australia, but relatively rare in North America; it inhabits small perennial and ephemeral ponds and wetlands. Because of earlier taxonomic changes, in North America D. bicuspidatus has been confused with the primarily planktonic Diacyclops thomasi (S.A. Forbes, 1882) and with the primarily benthic D. navus (Herrick, 1882) which were formerly considered as subspecies of D. bicuspidatus but are now considered as separate species. D. thomasi occurs from Alaska to Texas and is characteristic of the Laurentian Great Lakes of North America. In contrast to D. bicuspidatus, D. thomasi is a winter or cold water species found throughout the year in the Laurentian Great Lakes with peak abundance occurring in May or June. Males grow up to 0.8–1.0 millimetre (0.031–0.039 in) long, while females are larger at 0.9–1.6 mm (0.035–0.063 in). In North America, D. bicuspidatus has been reported from Canada and the USA as far south as Louisiana whereas D. thomasi has been reported from Alaska and Canada as far south as Morelos Mexico.