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.
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Some characteristics from the microscope images for the tentative species id: The postero-lateral projections are found only on segment 9, not segment 8. Based on the key in Jacobus et al. (2014), it appears to key to Neoleptophlebia adoptiva or Neoleptophlebia heteronea, same as this specimen with pretty different abdominal markings. However, distinguishing between those calls for comparing the lengths of the second and third segment of the labial palp, and this one (like the other one) only seems to have two segments. So I'm stuck on them both. It's likely that the fact that they're immature nymphs stymies identification in some important way.
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Stonefly Family Pteronarcyidae (Salmonflies)
This family contains the largest species of stoneflies in North America, with many female specimens exceeding 50mm. Unlike the large and active predaceous Perlidae Golden Stones, they are primarily detritivores that move about slowly. The most important species is Pteronarcys californica. See its hatch page for details. It takes them three years to develop to maturity, so it is useful for the angler to carry a variety of nymph sizes.
Family Range
Specimens of the Stonefly Family Pteronarcyidae
2 Male Adults
This shows the adult and its exuviae.
3 Female Adults
9 Nymphs
This salmonfly nymph is probably not quite fully grown, as it still has a couple months yet to emerge.
Pteronarcys nymphs live for two years before maturing. This small one is in its first year.
Here are two size classes of Pteronarcys nymphs. These probably represent two different generations. The largest will probably emerge next spring and the other in two years. There is probably another generation, smaller, I did not collect. In a Canadian study they discovered Pteronarcys eggs do not all hatch simultaneously but hatch for a period of nearly two years, making their egg/nymphal life 5 years. The other photo is of a curled nymph, a typical response to disturbance.
1 Streamside Picture of Pteronarcyidae Stoneflies:
Large stonefly nymphs sometimes crawl quite far from the water before emerging. This empty case is from a nymph that hatched about 5 feet up in a tree 10 feet from the river.
In this picture: Stonefly Species Pteronarcys dorsata (American Salmonfly).
Discussions of Pteronarcyidae
High Water
8 replies
Posted by Dbar on Apr 13, 2007 in the species Pteronarcys californica
Last reply on Jun 11, 2017 by Ricofreako
The hatch often occurs during high water (just after peak) so you sometimes have limited visibility during the hatch. Also - I believe that they can occur above 7000 feet.
Love ths site.
Love ths site.
Salmonfly question for you westerners
7 replies
Posted by Troutnut on Jul 30, 2006 in the species Pteronarcys californica
Last reply on Jun 4, 2016 by Chipper
I don't have many reliable sources about this species, so it'd be great if you western fishermen could read over the article and make sure I haven't said anything stupid or omitted anything important. I'll be happy to incorporate any additions you have.
Question
7 replies
Posted by Max29 on Jan 29, 2008 in the species Pteronarcys dorsata
Last reply on Jan 29, 2008 by Taxon
Are stoneflies and salmonflies the same thing or are they just related because here in the mid west we have the stonfly hatch and if they are related the stonfly could be called the salmonfly and the salmonfly hatch is only in the west because I have trouble because I want to become a better insect identifier when it comes to fishing because i went to other sites that so a stonefly is a stonefly and a salmonfly is a salmon fly but yet you say stonefly nymph but in parenteseses you have american salmonfly so is there really no such thing as a salmonfly but it is rather called a stonefly.
Start a Discussion of Pteronarcyidae
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.
- Swisher, Doug and Carl Richards. 2000. Selective Trout. The Lyons Press.
Stonefly Family Pteronarcyidae (Salmonflies)
Taxonomy
Genus in Pteronarcyidae: Pteronarcella, Pteronarcys