Hex Mayflies
Hexagenia limbata
The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.
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Some characteristics from the microscope images for the tentative species id: The postero-lateral projections are found only on segment 9, not segment 8. Based on the key in Jacobus et al. (2014), it appears to key to Neoleptophlebia adoptiva or Neoleptophlebia heteronea, same as this specimen with pretty different abdominal markings. However, distinguishing between those calls for comparing the lengths of the second and third segment of the labial palp, and this one (like the other one) only seems to have two segments. So I'm stuck on them both. It's likely that the fact that they're immature nymphs stymies identification in some important way.
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Identification: Key to Genera of Rhyacophilidae Adults
Identification: Key to Genera of Rhyacophilidae Adults
Adapted from Merritt R.W., Cummins, K.W., and Berg, M.B. (2019)
This couplet refers figures (usually designated 'sf') from this source.
You will need the source (make sure to get the same edition!) to see them.
This couplet refers figures (usually designated 'sf') from this source.
You will need the source (make sure to get the same edition!) to see them.
| Option 1 | Option 2 |
|---|---|
Mesoscutellum without long hairs 
| Mesoscutellum with tuft of long, fine hairs |
| Forewings each less than 20 mm long | Forewings each more than 20 mm long |
| Widespread | Pacific states |
| Adults as in sf 10.191 | |
1 Example Specimen | |
| Rhyacophila | Himalopsyche Species Himalopsyche phryganea |
Adapted from Merritt R.W., Cummins, K.W., and Berg, M.B. (2019)
The current couplet is highlighted with darker colors and a icon, and couplets leading to this point have a icon.
Couplet 1 (You are here)
Leads to Rhyacophila:
- Mesoscutellum without long hairs
- Forewings each less than 20 mm long
- Widespread
- Adults as in sf 10.191
Leads to Himalopsyche
(Himalopsyche phryganea):
(Himalopsyche phryganea):
- Mesoscutellum with tuft of long, fine hairs
- Forewings each more than 20 mm long
- Pacific states
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References
- Jacobus, L. M., Wiersema, N.A., and Webb, J.M. 2014. Identification of Far Northern and Western North American Mayfly Larvae (Insecta: Ephemeroptera), North of Mexico; Version 2. Joint Aquatic Science meeting, Portland, OR. Unpublished workshop manual. 1-176.
- Merritt R.W., Cummins, K.W., and Berg, M.B. 2019. An Introduction to the Aquatic Insects of North America (Fifth Edition). Kendall/Hunt Publishing Company.