Hex Mayflies
Hexagenia limbata
The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.
Featured on the forum
Nymphs of this species were fairly common in late-winter kick net samples from the upper Yakima River. Although I could not find a key to species of Zapada nymphs, a revision of the Nemouridae family by Baumann (1975) includes the following helpful sentence: "2 cervical gills on each side of midline, 1 arising inside and 1 outside of lateral cervical sclerites, usually single and elongate, sometimes constricted but with 3 or 4 branches arising beyond gill base in Zapada cinctipes." This specimen clearly has the branches and is within the range of that species.
Troutnut is a project started in 2003 by salmonid ecologist Jason "Troutnut" Neuswanger to help anglers and
fly tyers unabashedly embrace the entomological side of the sport. Learn more about Troutnut or
support the project for an enhanced experience here.
Mayfly Family Siphlonuridae (Gray Drakes)
These large, slender mayflies have nymphs of the swimming type, like Isonychiidae and Metretopodidae, and they generally inhabit slow water. See Siphlonurus for details -- it is the only genus of known importance to anglers.
Family Range
Identification
To determine whether a specimen of Ephemeroptera belongs to Siphlonuridae, use the Key to Families of Mayfly Nymphs or Key to Families of Mayfly Duns and Spinners.
Specimens of the Mayfly Family Siphlonuridae
2 Female Duns
I caught this specimen two days' walk from my macro lenses, but I don't think I have a dun of this species yet, so I took the best photos I could with my iPhone.
This one hatched in my house after I brought some nymphs home to photograph.
5 Male Spinners
Egg-laying females of this species were the most noticeable insect over the water at dusk on this small trout stream in Wisconsin's Blue Hills. I caught several of them and photographed one, but this was the only male, netted in mid-air mated to one of the females.
This specimen was easy to key to species using the old keys in < id="115" />, and was the basis for IDs of several other Siphlonurus specimens of the same species collected on the same day.
7 Female Spinners
I'm tentatively classifying this one as Siphlonurus alternatus, because it seems to fit that species best in the old keys in Needham's Biology of Mayflies, but I'm hesitant because I can't find documentation that southwest Montana or the surrounding area is within the species' range, although they are widely distributed throughout eastern North American and western Canada.
Egg-laying females of this species were the most noticeable insect over the water at dusk on this small trout stream in Wisconsin's Blue Hills. I caught several of them along with one male netted in mid-air mated to one of the females.
I found this specimen and saw a few more of its kind during midday on a small, steep, rocky creek fairly high in the Cascades, different from the previously reported habitats of its species.
This specimen was identified by association with this male.
This one had some trouble molting out of the dun stage, but I took pictures anyway.
10 Nymphs
I photographed this nymph in the middle of molting between one instar and the next (not hatching).
This specimen was the first record from Montana and the first record from the mountain west except Alberta where it was first described. It was found in temporary ponds.The nymph has double gills on all segments. The abdominal stripe is an important feature for identification
This species emerges very late in the fall often along with Siphlonurus autumnalis just before ice forms on edges of streams.
3 Underwater Pictures of Siphlonuridae Mayflies:
Several fast-swimming Siphlonurus nymphs blend in very well with the silt in this slow backwater along a trout stream.
In this picture: Mayfly Genus Siphlonurus (Gray Drake).
Start a Discussion of Siphlonuridae
References
- Baumann, Richard W. 1975. Revision of the Stonefly Family Nemouridae (plecoptera) : a Study Of The World Fauna At The Generic Level. Smithsonian Contributions to Zoology undef(211): 1-74.
Mayfly Family Siphlonuridae (Gray Drakes)
Taxonomy
1 genus (Edmundsius) isn't included.