Blue-winged Olives
Baetis
Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.
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This one seems to tentatively key to Holocentropus, although I can't make out the anal spines in Couplet 7 of the Key to Genera of Polycentropodidae Larvae nor the dark bands in Couplet 4 of the Key to Genera of Polycentropodidae Larvae, making me wonder if I went wrong somewhere in keying it out. I don't see where that could have happened, though. It might also be that it's a very immature larva and doesn't possess all the identifying characteristics in the key yet. If Holocentropus is correct, then Holocentropus flavus and Holocentropus interruptus are the two likely possibilities based on range, but I was not able to find a description of their larvae.
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Identification: Key to Genera of Glossosomatidae Larvae, Couplet 5
Identification: Key to Genera of Glossosomatidae Larvae, Couplet 5
Error: Tried to access a key that isn't live.
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 |
|---|---|
Pronotum excised 1/3rd anterolaterally to accommodate coxae (sf 19.165) 
| Pronotum excised 2/3rds anterolaterally to accommodate coxae (sf 19.166) |
| Dome-like case of stones with transverse ventral strap of finer sand and interchangeable ends (sf 19.38, 19.459a, 19.459b) | Case similar to that at left |
| Widespread | West |
1 Example Specimen
I caught this tiny larva without a case, but it seems to key pretty clearly to to Glossosomatidae. From there, the lack of sclerites on the mesonotum points to either Glossosoma or Anagapetus. Although it's difficult to see in a 2D image from the microscope, it's pretty clear in the live 3D view that the pronotum is only excised about 1/3 of its length to accommodate the forecoxa, not 2/3, which points to Glossosoma at Couplet 5 of the Key to Genera of Glossosomatidae Larvae.
| |
| Glossosoma | Anagapetus No further information about this genus is available on Troutnut.com at this time. |
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.
Leads to Couplet 2:
- Mesonotum with 2 or 3 sclerites (sf 19.156, 19.157, sometimes hard to see)
- Head with ventromesal margins of genae not thickened
- Posterior median ventral ecdysial line about 1.5 times as long as each anterior divergent branch (sf 19.159, 19.160)
- Anal opening without dark, sclerotized line on each side
Couplet 2
Leads to Couplet 5:
- Mesonotum without sclerites
- Head with ventromesal margins of genae thickened
- Posterior median ventral ecdysial line about as long as each anterior divergent branch (sf 19.158)
- Anal opening with dark, sclerotized line on each side (sf 19.60, 19.164)
Couplet 5
Leads to Padunia
(Padunia jeanae):
(Padunia jeanae):
- Each tarsal claw apparently trifid, with 3 points subequal in length (sf 19.161)
- Southeast
Padunia
(Padunia jeanae)
(Padunia jeanae)
Leads to Couplet 4:
- Each tarsal claw with normal single point, basal seta and basal process much smaller (sf 19.162, 19.163)
Couplet 4
Leads to Protoptila:
- Basal seta of each tarsal claw long, thin, and arising from side of stout basal process (sf 19.163)
- Case constructed with some relatively large stones (sf 19.167)
- Widespread
Couplet 5 (You are here)
Leads to Glossosoma:
- Pronotum excised 1/3rd anterolaterally to accommodate coxae (sf 19.165)
- Dome-like case of stones with transverse ventral strap of finer sand and interchangeable ends (sf 19.38, 19.459a, 19.459b)
- Widespread
Leads to Anagapetus:
- Pronotum excised 2/3rds anterolaterally to accommodate coxae (sf 19.166)
- Case similar to that at left
- West
Anagapetus
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References
- 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.