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Lateral view of a Male Baetis (Baetidae) (Blue-Winged Olive) Mayfly Dun from Mystery Creek #43 in New York
Blue-winged Olives

Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.

27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.
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Mayfly Genus Caenis (Angler's Curses)

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.

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 : June through early September; best in June and July

Preferred waters: Rivers and lakes

Most Caenis mayflies emerge in the evenings when other, larger mayflies are abundant on the water. This limits their importance.

In 320 records from GBIF, adults of this genus have mostly been collected during July (28%), June (26%), August (24%), May (10%), and September (8%).

In 145 records from GBIF, this genus has been collected at elevations ranging from 26 to 8022 ft, with an average (median) of 2690 ft.

Genus Range

Hatching behavior

Caenis mayflies typically emerge, molt into spinners, mate, and oviposit within one hour.

Nymph biology

Substrate: Silt, weeds

Every 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 gills adapted to survival on silty bottoms.

Specimens of the Mayfly Genus Caenis

1 Female Dun
1 Female Spinner
9 Nymphs

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Mayfly Genus Caenis (Angler's Curses)

Genus Range
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