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Giant, or Burrower, Mayfly (Imago) - Hexagenia bilineata - female

Giant, or Burrower, Mayfly (Imago) - Hexagenia bilineata - Female
Hwy 55 at Sedwick, Durham County, North Carolina, USA
July 6, 2004
Size: 29 mm
A very large species (body length 29 mm, excluding tail) found under a light. Compare to Troy Bartlett's photo:

Thanks to Kerry Matz for the identification. (See comments.)

Moved from Hexagenia. Thanks for the ID, Lloyd!

H. bilineata female imago
Kerry mentioned bilineata in the earlier discussion, and this dark species is usually one of the easiest to distinguish from the various limbata morphs in photographs. The slight cloudiness near the bases of the wings that Kerry noticed is not unusual in some imagos and can also be seen in Troy's photograph (thumbnail).

Large Mayfly
The size, hindwing, and tarsi/femora ratio suggests Hexagenia sp. (Ephemeroidea: Ephemeridae: Ephemerinae). H. limbata would be a good guess based on the coloration, looks like an female imago.

Thanks very much!
I may post some more images of mayflies--nice to have an expert on board.

Thanks again.

Patrick Coin
Durham, North Carolina

No expert here
Had a chance to work with mayflies in the past, luckily had some reference material at hand. The Hexagenia are usually at the forefront in the literature because of their size and emergence numbers. Around the Great Lakes region, snowplows have been used to clear bridges of the spent adults.

A possible resource for identifying mayfly and/or stonefly images would be a local fly-fishing shop, some of these people are well versed in what inhabits their region. Don't be surprised if some old geezer in ratty clothes corrects your pronunciation of latin.

Thanks, others in guide
I see you've looked at some others in the guide. What about these two images of Troy's? They look rather like Hexagenia to my untutored eye:

Patrick Coin
Durham, North Carolina

Hexagenia ??
Patrick, I've changed my mind about your image(s), the cloudy wing visible in front of the body suggests that this is a female SUBIMAGO. Troy's are very likely a male imago (clear wings) of Hexagenia (for now limbata, another species, H. bilineata should be considered, I'm not sure what it's coloration is in the adult stages.

For most mayflies; the subimago is duller and has cloudy or colored wings, it still has that layer to moult. The imago usually is brighter (although the coloration change can be dramatic, as in really different) and the wings become clear and glassy (hyaline).

This is likely a female imago. Although the female doesn't have the long forelegs and extremely long tails of the male imago, the iridescent sheen on the wings is usually a tip-off. (You can also see the dark costal margin of the right forewing through the other wing.) The wings of most subimago mayflies are covered with tiny hairs that make them fairly unwettable (or hydrofuge--an asset during emergence). In all but a few mayflies, this is shed leaving a glassy iridescent look.

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