When the important hatches of Tricorythodes were first discovered by anglers, Caenis was given the credit. We now know that the Caenis mayflies are a different group, smaller and less common in trout streams, and they hatch in the evening instead of the morning.
» Genus Caenis (Angler's Curses)
7 species aren't included.
They very rarely elicit selective feeding, but when they do they're very tough to match because they're often much smaller than size 28. This difficulty has earned them the nickname "Angler's Curse." Where & When
Time Of Year (?):Most Caenis mayflies emerge in the evenings when other, larger mayflies are abundant on the water. This limits their importance.Hatching BehaviorCaenis mayflies typically emerge, molt into spinners, mate, and oviposit within one hour.Nymph Biology
June through early September; best in June and JulyPreferred Waters:
Rivers and lakes
Substrate: Silt, weedsEvery book says pools and stagnant back-waters are the prime habitats of these nymphs. This is probably true, but I have often found them in gravel, vegetation, and other habitats. They have operculate (
Operculate: Lidlike; usually used to describe the pair of enlarged elytroid gills (called the operculum) which some silt-dwelling mayfly nymphs like Caenis and Eurylophella have developed to shield their other gills from debris.) gills adapted to survival on silty bottoms.
The operculate gills of a Caenis nymph.
Pictures of 11 Mayfly Specimens in the Genus Caenis:
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