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.
|Option 1||Option 2|
|Body typically less than 5 mm long||Body length variable, often more than 5 mm|
|Mesoscutum without setose warts||Mesoscutum often with setal warts|
|Mesoscutellar warts transverse and meeting mesally to form angulate ridge (sf 19.562)||Mesoscutellar warts typically rounded or elongate (sf 19.55)|
|Hind wings narrow and apically acute, and often with a posterior fringe of long setae (sf 19.563)||Hind wings typically broader than at left and apically rounded (sf 19.589); if posterior fringe of setae present, then setae shorter than at left|
|Adults as in sf 10.194|
|Remaining families: Apataniidae, Beraeidae, Brachycentridae, Calamoceratidae, Dipseudopsidae, Ecnomidae, Glossosomatidae, Goeridae, Helicopsychidae, Hydrobiosidae, Hydropsychidae, Hydroptilidae, Lepidostomatidae, Leptoceridae, Limnephilidae, Molannidae, Odontoceridae, Philopotamidae, Phryganeidae, Polycentropodidae, Psychomyiidae, Rhyacophilidae, Rossianidae, Sericostomatidae, Thremmatidae, Uenoidae, and Xiphocentronidae|
2 Example Specimens
I'm tentatively classifying this one as Dibusa angata because I cannot see any ocelli in my dorsal view of the head (and because it has a single spur on each front tibia). However, sometimes they can be difficult to spot when obscured behind setae in general, so I'm not 100 % sure on this one. If there are ocelli I missed, then based on ranges and colors the genus ought to be Stactobiella.
5 Example Specimens
I had some trouble working through the genus key for this one because I'm not great at interpreting caddis wing venation. Fortunately, figure 19.707 in An Introduction to the Aquatic Insects of North America (Fifth Edition) shows the distinctive color pattern of the striking forewings on Hydatophylax argus, which is a perfect match for the pattern as well as venation. As there are no other species in that genus in this area, I can be pretty confident in the species ID.
I first just assumed this was Dicosmoecus based on anglers' conventional wisdom since it's a large orange "October caddis," but Creno set me straight. I should have keyed it out. After another look under the microscope, it lacks an anepisternal wart on the mesopleuron, which rules out Dicosmoecus. The midtibiae have 2 apical spurs and 1 pre-apical spur, and from there the color pattern of the wing points to Onocosmoecus. The location then narrows the species to unicolor.
The setae on the wings make it a big tricky to identify this caddisfly from the "splayed wings" view because they obscure the venation, but several of the side views provide a good look at the important forewing veins. It keys pretty confidently to Ironoquia. Based on species ranges and a photo on BugGuide seemingly of this species and some alternatives, it seems Ironoquia lyrata is by far the most likely option.
|Hydroptilidae||Go to Couplet 2|