Natural History of the two Crayfish of Northwestern Iowa, Orconectes virilis and Orconectes immunis

Abstract

The only two crayfish inhabiting northwestern Iowa, O. immunis and O. virilis, are ecologically isolated to pond and stream habitats respectively. The former burrows deeply to escape summer drought and winter cold, while the latter does not burrow extensively and apparently overwinters buried in stream beds. The pattern of reproductive events is basically similar in the two species, but O. virilis generally lags several weeks behind O. immunis. The pond species often matures in one summer under good conditions and may lay eggs in either fall or spring; the stream species is less flexible, not maturing until the end of its second summer and laying eggs only in the late spring.