**Mayfly Species Acentrella insignificans (Tiny Blue-Winged Olive)**

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Taxonomic Navigation -?-

Kingdom Animalia (Animals)

» Phylum Arthropoda (Arthropods)

» Class Insecta (Insects)

» Order Ephemeroptera (Mayflies)

» Family Baetidae (Blue-Winged Olives)

» Genus Acentrella (Tiny Blue-Winged Olives)

» Species insignificans (Tiny Blue-Winged Olive)

Common Names

Match	Common Name
	Tiny Blue-Winged Olive
	Miniature Blue-Winged Olive

Pictures Below ↓

This species shares its distribution with the much more common Acentrella turbida over much of it's range. In the West, it overshadows turbida in some locales. It can be differentiated from turbida by the presence of hind wings and from most other baetids by its hind wings having two longitudinal veins (Longitudinal vein: Longitudinal veins are the major long veins running length-wise through an insect's wing, connecting the base to the outer margin, or the major branches from those veins.) and a lack of costal projection (

The costal projection of a Baetidae dun.

Costal projection: A bump or point sticking up from the front margin of an insect's wing, usually the rear wing of certain mayflies. It is sometimes called a costal process.). It was previously classified as Baetis insignificans.

Pictures of 2 Mayfly Specimens in the Species Acentrella insignificans:

Male Acentrella insignificans (Tiny Blue-Winged Olive) Mayfly Dun

View 11 PicturesThis specimen emerged indoors from nymphs I had collected, then partly molted into a spinner but got stuck along the way. I've included a couple pictures showing some of the spinner colors. It got a bit waterlogged after emerging, so the wings aren't in perfect shape, but it still represents one of two Baetids that were emerging and drawing trout to rise on the Yakima. Based on body size and shape, it is most likely the same species as this nymph.

Collected September 12, 2020 from the Yakima River in Washington
Added to Troutnut.com by Troutnut on September 19, 2020

Male Acentrella insignificans (Tiny Blue-Winged Olive) Mayfly Nymph

View 10 PicturesAnother nymph probably of the same species as this one emerged and was photographed as a dun and partly-molted spinner.

Collected September 12, 2020 from the Yakima River in Washington
Added to Troutnut.com by Troutnut on September 19, 2020

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Jargon Defined:

The costal projection of a Baetidae dun.

Costal projection: A bump or point sticking up from the front margin of an insect's wing, usually the rear wing of certain mayflies. It is sometimes called a costal process.

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.

Longitudinal veins: Longitudinal veins are the major long veins running length-wise through an insect's wing, connecting the base to the outer margin, or the major branches from those veins.

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.