Blue-winged Olives
Baetis
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.
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This dun emerged from a mature nymph on my desk. Unfortunately its wings didn't perfectly dry out.
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Dark Olive Duns
Like most common names,"Dark Olive Dun" can refer to more than one taxon. They're previewed below, along with 3 specimens. For more detail click through to the scientific names.
Mayfly Species Drunella coloradensis
These are very rarely called Dark Olive Duns.
This species is very similar to Drunella flavilinea. In areas where their ranges overlap, they can sometimes be found in the same streams. They are similar enough that anglers sometimes refer to either or both species as "Flavs." Allen and Edmunds (1962) say that Drunella coloradensis tends to favor colder water than Drunella flavilinea and that it may emerge as much as a month later.
The positive species ID on this dun comes from both the spinner that it (or possibly one other dun just like it) molted into and the overwhelming abundance of nymphs of this species in my kicknet samples from the same site.
This spinner molted from this dun, or possibly one other dun I had in the same container that looked just like it.
This one nicely illustrates the variation in coloration within an single Ephemerellid species in a single stream, when compared to its lighter, banded counterpart.
See 7 more specimens...
Mayfly Species Siphlonurus rapidus
These are very rarely called Dark Olive Duns.
This species may reinforce spinner flights of Siphlonurus quebecensis and Siphlonurus alternatus.