Hexagenia limbata

Photo Credit: Jessica Louque, Smithers Viscient, Bugwood.org. License: Creative Commons Attribution 3.0 License (http://creativecommons.org/licenses/by/3.0/us/)
Hexagenia limbata
Common Name: giant mayfly
Animal Guild: Insect
Class > Order > Family: Insecta > Ephemeroptera > Ephemeridae
Where is the species found?
States & Provinces
AL, AR, CA, CO, CT, FL, GA, IA, IL, IN, KY, ME, MI, MN, MO, MS, MT, NC, ND, NE, NH, NS, NV, NY, OH, OK, ON, OR, SC, SD, SK, TN, TX, UT, VA, WA, WI, WY
Which phenophases should I observe?
Do you see/hear...?
Activity Adults
One or more adults are seen or heard moving about or at rest. Mayfly adults (imagos or spinners) are brighter in color than subadults, and have clear, glassy wings.
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What is the intensity of emergence?

  • Slight: Less than 100 individuals are seen within the immediate observation area (approximately 5 feet in any direction).
  • Light: Between 100 and 500 individuals are seen within the immediate observation area (approximately 5 feet in any direction).
  • Moderate: Consistent coverage of surfaces is seen (ground, building walls and windows, vegetation, etc.), or small groups of individuals are seen under lights.
  • Heavy: Thick coverage of surfaces is seen, or very noticeable groups of individuals, including small to medium piles, are seen under lights.
  • Very heavy: Very thick coverage of surfaces is seen (with minimal surface area exposed), or large groups of individuals, including large piles, are seen under lights.
Reproduction Mating
A male and female are seen coupled in a mating position, usually one on top of the other.

For abundance, enter the number of individual animals observed in this phenophase.
Egg laying
A female is seen laying eggs directly onto the water surface, or attached to aquatic plants.

For abundance, enter the number of individual animals observed in this phenophase.
Development Subadults
One or more subadults are seen moving about or at rest. Mayfly subadults (subimagos or duns) are duller in color than adults, and have cloudy wings with a fringe of small hairs.

What is the intensity of emergence?

  • Slight: Less than 100 individuals are seen within the immediate observation area (approximately 5 feet in any direction).
  • Light: Between 100 and 500 individuals are seen within the immediate observation area (approximately 5 feet in any direction).
  • Moderate: Consistent coverage of surfaces is seen (ground, building walls and windows, vegetation, etc.), or small groups of individuals are seen under lights.
  • Heavy: Thick coverage of surfaces is seen, or very noticeable groups of individuals, including small to medium piles, are seen under lights.
  • Very heavy: Very thick coverage of surfaces is seen (with minimal surface area exposed), or large groups of individuals, including large piles, are seen under lights.
Dead adults
One or more dead adults are seen.

What is the intensity of death?

  • Slight: Less than 100 individuals are seen within the immediate observation area (approximately 5 feet in any direction).
  • Light: Between 100 and 500 individuals are seen within the immediate observation area (approximately 5 feet in any direction).
  • Moderate: Consistent coverage of surfaces is seen (ground, building walls and windows, vegetation, etc.), or small groups of individuals are seen under lights.
  • Heavy: Thick coverage of surfaces is seen, or very noticeable groups of individuals, including small to medium piles, are seen under lights.
  • Very heavy: Very thick coverage of surfaces is seen (with minimal surface area exposed), or large groups of individuals, including large piles, are seen under lights.
Method Individuals at a light
One or more individuals are seen at a light, whether flying or at rest.

For abundance, enter the number of individual animals observed in this phenophase.
Individuals in a net
One or more individuals are seen caught in a net.

For abundance, enter the number of individual animals observed in this phenophase.
Individuals in a trap
One or more individuals are seen caught in a trap.

For abundance, enter the number of individual animals observed in this phenophase.
What do these phenophases look like?

There is currently no photoguide available for this species. If you'd like help us create one, use the guidance document and species template provided here. Then send it via email to education@usanpn.org when it is complete.