**Mayfly Species Acerpenna pygmaea (Tiny Blue-Winged Olive)**

Mayflies

Caddisflies

Stoneflies

Taxonomic Navigation -?-

Kingdom Animalia (Animals)

» Phylum Arthropoda (Arthropods)

» Class Insecta (Insects)

» Order Ephemeroptera (Mayflies)

» Family Baetidae (Blue-Winged Olives)

» Genus Acerpenna (Tiny Blue-Winged Olives)

» Species pygmaea (Tiny Blue-Winged Olive)

Common Names

Match	Common Name
	Tiny Blue-Winged Olive
	Medium Olive Dun

Pictures Below ↓

This species is known in older taxonomies under the former name Baetis pygmaeus.
It is a diminutive baetid with distribution across every region. It is reported to have localized hatches of occasional importance.

Where & When

Regions: East, Midwest, West

Time Of Year (?): Early August through mid-September

Nymph Biology

Current Speed: Slow

Substrate: Vegetation

The nymphs may inhabit freestone streams, but they avoid the faster currents.

Pictures of 4 Mayfly Specimens in the Species Acerpenna pygmaea:

Specimen Page:12

Acerpenna pygmaea (Tiny Blue-Winged Olive) Mayfly Nymph

View 3 PicturesThis is a very rare mayfly in western Montana. The shape of the last gill is a key to its identification. I have collected this species in only one location.

Collected May 5, 2007 from the Upper Stillwater River in Montana
Added to Troutnut.com by Bnewell on June 26, 2011

Male Acerpenna pygmaea (Tiny Blue-Winged Olive) Mayfly Spinner

View 8 Pictures

Collected August 1, 2020 from the Henry's Fork of the Snake River in Idaho
Added to Troutnut.com by Troutnut on August 18, 2020

Female Acerpenna pygmaea (Tiny Blue-Winged Olive) Mayfly Spinner

View 6 Pictures

Collected July 31, 2020 from the Henry's Fork of the Snake River in Idaho
Added to Troutnut.com by Troutnut on August 17, 2020

Specimen Page:12

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Jargon Defined:

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).

Useful References:

Arbona, Fred Jr. 1989. Mayflies, the Angler, and the Trout. Nick Lyons Books.

Knopp, Malcolm and Robert Cormier. 1997. Mayflies: An Angler's Study of Trout Water Ephemeroptera . The Lyons Press.

Leonard, Justin W. and Fannie A. Leonard. 1962. Mayflies of Michigan Trout Streams. Cranbrook Institute of Science.