Giant salmonfly (Pteronarcys californica)
May and June signify a lot of things here in our area, sun, rain, sun, wildflowers, rain, rafting season, migratory birds arriving, fishing season heating up – but above all, they signify the arrival of the giant salmonfly (Pteronarcys californica).
While salmonflies are a crawly we’ve met before, they are truly a local celebrity and warrant a reintroduction every five or six years!
For folks new to our area, we’re about to answer the question of, “What the heck are those ginormous insects flying all over the area right now?”
While giant salmonflies are neither salmon, nor flies, they are giant and fascinating by any moniker. Salmonflies are stoneflies in the order Plecoptera, one of many orders of flying insects. We have stoneflies in various sizes and colors year-round from teeny winter stoneflies to lovely, lemony yellow and lime green stoneflies in spring and summer, but the salmonfly is the rock star of stoneflies.
Topping out at up to two and one-half inches in length, our local giant salmonflies are the largest of all the stoneflies in North America. Their “three-mile orange” markings also make them a standout.
What has given them national fame, however, is their hatching out habit.
Most stoneflies hatch out here and there throughout their given season. You’ll see golden, green and yellow stoneflies here and there all spring and summer long. True to their name our winter stoneflies likewise hatch throughout the winter months.
Salmonflies, however, hatch en masse over a period of a few weeks, and those weeks are here right now.
Even our recent, cool, wet weather didn’t slow their quest to leave behind the life aquatic and become airborne. Because salmonflies are so large, they take three years to fully mature as nymphs. Once the time has come for their final morph, the three-year nymphs come out from under the rocks they’ve hidden under all their young lives and head for the shallows.
The hatch starts earlier downstream and moves up, from warmer to cooler waters, so as June goes on, you’ll see more salmonflies the closer you are to the William Jess Dam.
When hatching, nymphs who aren’t gobbled up by hungry trout, hit the shore, then climb out onto riparian vegetation (trees, grass or even man-made structures) beginning around sunset and begin that final morph. Their adult life is brief, only a couple of weeks, and it’s no picnic getting it started.
Once the nymph is out of the water it’s a 45-minute to one-hour chore to extract their adult form from their nymphal exuviae (exoskelleton). Salmonflies take lots of time to rest during the process, and many literally die trying, they just don’t have the energy to complete the morph.
Once they are able to take wing, the odds are still against them as they are everyone’s favorite snack. Nesting birds love nothing more than a big, protein packed salmonfly.
Their real claim to foodstuff fame though, is that by do they get the trout jumping. Anglers from all over the United States hit local rivers when the salmonflies begin to hatch. The female salmonflies, especially, are an easy meal for salmonids. They fly low, and not well, over the water to deposit their eggs. Often, they’ll fall into the water or get pulled in by a wave and it’s a trout buffet.
During the hatch anglers use a mix of exquisitely tied salmonfly flies and/or bait up a hook with a live salmonfly (please don’t use live egg-bearing females – see photo – we want lots more salmonflies to hatch three years from now!)
Adult salmonflies don’t eat, so they lack mandibles, thus can’t bite and don’t sting. They help the economy by drawing in those fisher folks from all over to our little corner of the world!
Salmonfly nymphs are “shredders” feeding on large particular organic and leaf materials that have collected in debris dams or behind boulders or logjams, this helps keep our rivers and streams clean.
Adult salmonflies are food for fish, birds (especially nestlings), reptiles and small mammals, they’re practically a keystone species for our area.
While they may look quite odd as they eclose from nymph to adult, they are nifty natives which benefit all of us.