Dark Olive Duns

Mayflies

Caddisflies

Stoneflies

Scientific Names

Match	Scientific Name
	Drunella coloradensis
	Siphlonurus rapidus

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. 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.

Drunella coloradensis (Small Western Green Drake) Mayfly Nymph

View 11 PicturesThis one nicely illustrates the variation in coloration within an single Ephemerellid species in a single stream, when compared to its lighter, banded counterpart.

Collected July 25, 2019 from in
Added to Troutnut.com by on July 26, 2019

Male Drunella coloradensis (Small Western Green Drake) Mayfly Dun

View 8 PicturesThe 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.

Collected July 28, 2019 from in
Added to Troutnut.com by on July 30, 2019

Male Drunella coloradensis (Small Western Green Drake) Mayfly Spinner

View 9 PicturesThis spinner molted from this dun, or possibly one other dun I had in the same container that looked just like it.

Collected July 28, 2019 from in
Added to Troutnut.com by on July 30, 2019

See 6 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.

Jargon Defined:

Dun: Mayflies have two adult stages. They first emerge from the water as duns (scientifically known as the subimago stage). They then molt into the spinner (imago) stage, in which they mate and die. Sometimes the word "dun" is confusingly used to refer to a brownish gray color in fly tying materials.

Nymphs: The juvenile, underwater stages of mayflies, stoneflies, dragonflies, and damselflies and other aquatic insects whose juvenile stages are covered by hard exoskeletons. The word can also refer to the fishing flies which imitate these creatures, in which case it is used as a blanket term for flies imitating any underwater stage of an invertebrate (except for crayfish and leeches).

Spinner: There are two winged stages of adult mayflies. They emerge from the water as duns, molt on land (usually) into their fully mature stage, spinners. As spinners, they mate, lay eggs, and die.