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.
Jwatersphd on Jun 23, 2007June 23rd, 2007, 2:35 pm EDT
i am curious how to tell rhyacophila from macronema and whether it makes any difference either in terms of size or behavior. in schweibert's first volume from years ago they look very similar. i am awaiting his new two volume set but in the meantime would be curious i if anyone knows. there is definitely a green caddis that is quite prevalent on the gunnison in the black canyon and probably gorge below but i have not been especially successful at devising a good imitation. after looking at oliver edwards's video on czech nymphing, however, i am thinking the big problem is that i did not tie in such a method as to emphasize the heavily segmented body.
Rhyacophila are in the family of free-living caddisflies (Rhyacophilidae), whose larvae are characterized by: only pronotum having a sclerotized plate, mesonotum and metanotum being entirely membranous; sclerotized plate on top of abdominal segment nine; anal prolegs long with large claws.
Macronema (now Macrostemum, at least for those species of interest to flyfishers) are in the family of common net-spinner caddisflies (Hydropsycidae), whose larvae are characterized by: sclerotized plates on notum of all three thoracic segments; anal prolegs terminating in a brush of long setae.
Incidentally, no Macrostemum species are known from Colorado.
Ov10fac on Jul 30, 2019July 30th, 2019, 7:15 am EDT
What is the approximate length and width of this fly. I used to fish something similar to this on the South Platte in Colorado. Seems the ones I fished were a little more brown.
Troutnut on Jul 30, 2019July 30th, 2019, 7:29 am EDT
This one is over an inch long. The genus Rhyacophila is the largest (in number of species) genus of caddisflies, with several dozen different species in North America if I recall correctly. You very likely saw one of the other species of this genus on the South Platte.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist