Acerpenna pygmaea

Acerpenna pygmaea · Order: Ephemeroptera · Family: Baetidae

No source yet on danger. We have no source yet on whether it bites, stings or damages anything.
Acerpenna pygmaea
Photo: Even Dankowicz, CC BY

Acerpenna pygmaea is a tiny mayfly often called the blue-winged olive. It is a small minnow mayfly that belongs to the family Baetidae. The species is found throughout Canada and the continental United States.

Source: Wikipedia

How to recognize it

The bug is known as the tiny blue-winged olive.

Source: Wikipedia

Where it is found in the US

Recorded in 18 of 51 states and DC. Most records: Illinois, Vermont, Kansas, Michigan, Indiana, Alabama, Massachusetts, Maryland.

Darker = more records. Counts are museum and citizen-science records, not population size.

Source: GBIF

Status: native in North America; native in Canada. Source: iNaturalist

Months it is reported in the US

JFMAMJJASOND

Source: GBIF

Same family (Baetidae)

Pond OlivePond OliveCloeon dipterumSpeckled DunSpeckled DunCallibaetis pictusLarge Dark OliveLarge Dark OliveBaetis rhodaniLittle Blue-winged OliveLittle Blue-winged OliveBaetis tricaudatusPale WateryPale WateryBaetis fuscatusAcentrella turbidaAcentrella turbida

Sources

  • Wikipedia: https://en.wikipedia.org/wiki/Acerpenna_pygmaea

Look it up elsewhere: GBIF · iNaturalist · BugGuide · ITIS · Wikipedia

Text written 2026-10-24 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-24.

How this page works

This is one bug's fact sheet. The colored box at the top says whether it is dangerous. Sections below cover how to recognize it, whether it is a pest, and how to deal with it. The US map shows which states have records; tap a state to see other bugs there.

Every fact on Bug FAQ comes from a named source (university extension sites, government agencies, GBIF, iNaturalist, Wikipedia). The source is linked next to each section. If we have no source for something, we leave it out.