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 is an interesting one. Following the keys in Merritt R.W., Cummins, K.W., and Berg, M.B. (2019) and Jacobus et al. (2014), it keys clearly to Ephemerella. Jacobus et al provide a key to species, but some of the characteristics are tricky to interpret without illustrations. If I didn't make any mistakes, this one keys to Ephemerella mucronata, which has not previously been reported any closer to here than Montana and Alberta. The main character seems to fit well: "Abdominal terga with prominent, paired, subparallel, spiculate ridges." Several illustrations or descriptions of this holarctic species from the US and Europe seem to match, including the body length, tarsal claws and denticles, labial palp, and gill shapes. These sources include including Richard Allen's original description of this species in North America under the now-defunct name E. moffatae in Allen RK (1977) and the figures in this description of the species in Italy.
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Caddisfly Family Thremmatidae
This caddisfly family is important in the fall. Neophylax may be important nationwide, but Oligophlebodes is only known to provide fishable action in the West.
Where & when
In 189 records from GBIF, adults of this family have mostly been collected during October (34%), September (23%), August (15%), July (12%), and June (9%).
In 136 records from GBIF, this family has been collected at elevations ranging from 30 to 11191 ft, with an average (median) of 1880 ft.
Family Range
Specimens of the Caddisfly Family Thremmatidae
1 Female Adult
This large caddisfly looks really neat close-up.
3 Larvae
The size of the head compared to the body in this larva is surprising, and I think this means it's a fairly early instar of something which is going to get a lot bigger, but I'm not sure.
See the forum comments for notes on the identification of this specimen.
2 Underwater Pictures of Thremmatidae Caddisflies:
A variety of cased caddisfly larvae, probably mostly Neophylax, have clustered along the backside of a rock in fast water. There seem to be some Helicopsychidae larvae clustered along the bottom, and a few other taxa are mixed in. It's interesting that several larvae have especially large stones placed over the front openings of their cases, perhaps to block the case off for pupation.
It does seem to be the wrong time of year for Neophylax to be pupating, but that was the ID given for one of these which I collected and photographed up close.
It does seem to be the wrong time of year for Neophylax to be pupating, but that was the ID given for one of these which I collected and photographed up close.
A wide variety of caddis larvae and other insects have clustered together on the backside of this rock in fast water.
In this picture: Caddisfly Genus Neophylax (Autumn Mottled Sedge).
Start a Discussion of Thremmatidae
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.
Caddisfly Family Thremmatidae
Taxonomy
Genus in Thremmatidae: Neophylax, Oligophlebodes