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Lateral view of a Male Baetis (Baetidae) (Blue-Winged Olive) Mayfly Dun from Mystery Creek #43 in New York
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.

Dorsal view of a Limnephilidae (Giant Sedges) Caddisfly Larva from the Yakima River in Washington
This specimen resembled several others of around the same size and perhaps the same species, which were pretty common in my February sample from the upper Yakima. Unfortunately, I misplaced the specimen before I could get it under a microscope for a definitive ID.
27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.
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Identification: Key to Genera of Glossosomatidae Larvae, Couplet 2

Identification: Key to Genera of Glossosomatidae Larvae, Couplet 2

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.
Option 1Option 2
Mesonotum with 3 sclerites (sf 19.157)Mesonotum with 2 sclerites (sf 19.156)
Ventral apotome of head slender laterally, parallel-sided (sf 19.160)Ventral apotome of head not as slender, broader laterally than mesally (sf 19.159)
Remaining genera: Culoptila, Padunia, and Protoptila
Go to Couplet 3 Agapetus
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
Couplet 2

You are here
Couplet 2 (You are here)
Leads to Couplet 3:
  • Mesonotum with 3 sclerites (sf 19.157)
  • Ventral apotome of head slender laterally, parallel-sided (sf 19.160)
Couplet 3
Leads to Agapetus:
  • Mesonotum with 2 sclerites (sf 19.156)
  • Ventral apotome of head not as slender, broader laterally than mesally (sf 19.159)
Leads to Padunia
(Padunia jeanae):
  • Each tarsal claw apparently trifid, with 3 points subequal in length (sf 19.161)
  • Southeast
Padunia
(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
Leads to Culoptila:
  • Basal seta of each tarsal claw short and stout, larger than basal process (sf 19.162)
  • Case constructed of uniformly small stones (sf 19.168)
  • Northwest, West
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

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