(Herrick, 1879) (a calanoid copepod)

Habitat: Freshwater lakes.
Life History: Females may carry up to 20 eggs; develop from egg to adult in 15 days at 25°C and in 66 days at 10°C; females average 1.2 mm in length and males average 1.0 mm; feeds on algae but is also a fierce and selective predator on small animals such as rotifers.
Native Range: Central United States south to Texas and Louisiana and the Mississippi drainage.
Nonindigenous Range: First found in Lake Ontario in 1967; present in Lake Erie, Lake Huron, Lake St. Clair, Saginaw Bay and Saginaw River.
Impacts: Impacts remain unclear; however, maximum densities in Lake Erie coastal marsh reached 10,000/m³.
Comments: Introduction into the Great Lakes could have been accidental by fisherman or recreational boaters, or some scientists believe this species exists in lakes and wetlands around the Great Lakes and could have been occasionally flushed into the lakes.

  (Poppe, 1885) (a calanoid copepod)

Habitat: Euryhaline species, found in estuaries, saltmarshes, brackish waters and freshwater lakes, ponds and reservoirs.
Life History: Planktonic or epibenthic grazer, feeding on plankton and organic detritus; females can produce multiple clutches of eggs; females 1.1-1.5 mm, males 1.0-1.5 mm; overwinters as eggs, juveniles and adult stages found between April and January.
Native Range:  Europe, Asia and coastal North America.
Nonindigenous Range: Found in a few locations in Massachusetts and Virginia; the Hudson River in New York; the District of Columbia; Lake Ontario in 1958 and Lake Erie; present in all of the Great Lakes.
Impacts: Unknown.
Comments: Possibly introduced with fish stocking.