As far as I can tell, this species has only previously been reported from one site in Oregon along the Columbia gorge. However, the key characteristics are fairly unmistakable in all except for one minor detail:
— 4 small yellow spots on frons visible in photos
— Narrow occipitalspinule row curves forward (but doesn’t quite meet on stem of ecdysial suture, as it's supposed to in this species)
— Short spinules on anterior margin of front legs
— Short rposterior row of blunt spinules on abdominal tergae, rather than elongated spinulesdorsally
I caught several of these mature nymphs in the fishless, tiny headwaters of a creek high in the Wenatchee Mountains.
Fork IV: A fork in the media of caddisfly wings formed by the branching of veins M3 and M4. Typically, this fork is present in forewings but absent in hind wings.
This other word references the same concept: fork 4.
In this Hydatophylax argus caddisfly, Fork IV is extremely short in the forewing. It appears to be slightly present (not marked) in the hind wing as well, although it's not supposed to be there.
