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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 Skwala (Perlodidae) (Large Springfly) Stonefly Nymph from the Yakima River in Washington
This Skwala nymph still has a couple months left to go before hatching, but it's still a good representative of its species, which was extremely abundant in my sample for a stonefly of this size. It's obvious why the Yakima is known for its Skwala hatch.
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 Species of Caudatella Nymphs, Couplet 2

Identification: Key to Species of Caudatella Nymphs, Couplet 2

Adapted from Jacobus 2010 (2010)
Option 1Option 2
Paired medial spines on abdominal terga long and curved (at least on middle segments), some almost hook likePaired medial spines on abdominal terga relatively straight, none longer than respective segment
Remaining species: Caudatella columbiella, Caudatella heterocaudata, and Caudatella jacobi
1 Example Specimen
Caudatella hystrix Go to Couplet 3
Adapted from Jacobus 2010 (2010)
The current couplet is highlighted with darker colors and a icon, and couplets leading to this point have a icon.
Leads to Caudatella edmundsi:
  • Maxillary palp vestigial; tarsal claw with two prominent rows of denticles
Leads to Couplet 2:
  • Maxillary palp with three distinct segments; tarsal claw with only one distinct row of denticles
Couplet 2
Couplet 2

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Couplet 2 (You are here)
Leads to Caudatella hystrix:
  • Paired medial spines on abdominal terga long and curved (at least on middle segments), some almost hook like
Leads to Couplet 3:
  • Paired medial spines on abdominal terga relatively straight, none longer than respective segment
Couplet 3
Leads to Caudatella jacobi:
  • Cerci approximately two thirds length of median filament
  • Abdominal sterna with solid color, never with longitudinal stripes or other such markings
Leads to Couplet 4:
  • Cerci less than one-half length of median filament
  • Abdominal sterna almost always with three dark, longitudinal markings
Couplet 4
Leads to Caudatella heterocaudata:
  • Cerci approximately one-third length of median filament (about the length of the abdomen)
  • Distinct pair of medial spines present only on abdominal terga 2–9, with the spine tips blunt
Leads to Caudatella columbiella:
  • Cerci approximately one-sixth length of median filament (about half the length of the abdomen)
  • Distinct pair of medial spines present on abdominal terga 1–9, with the spine tips sharp

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References

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