Contribution to the morphology and descriptive biology of Caurinella idahoensis (Ephemeroptera: Ephemerellidae)

Reared specimens from Bridge Creek, Idaho County, Idaho, provide the bases for the first descriptions of Caurinella idahoensis egg and alate stages and redescription of the larval stage. Larvae are distinguished from other Nearctic Ephemerellinae species by the distinctive posterolateral projections on abdominal segment 9. Male adults have a unique combination of characters associated with their genitalia. Larvae were associated with the colonial blue-green alga Nostoc parmelioides in a clear, cold headwater stream. Several other Diptera, Ephemeroptera, Plecoptera, and Trichoptera also were found in cohabitation with C. idahoensis. Amorphous detritus appears to be a major component of the diet of C. idahoensis, and larvae may defend small territories on rock surfaces. Larvae exhibited prolonged preemergence behavior in the laboratory rearing apparatus.