Salmonfly
Pteronarcys californica
Key Identification Characters - Nymph 2
- Two tails half the length of abdomen or less.
- Thick filamentous gills on underside of thorax and first two abdominal segments.
- Body uniformly colored dark brown to black; lighter color along underside of abdomen.
- Large. Body length of mature nymphs (excluding tails) 40-50mm.
Similar nymphs: 3
The family Pteronarcyidae includes two genera (Pteronarcys and Pteronarcella) and five species all of which are found in western streams. The species of Pteronarcella can be quickly differentiated from Pteronarcys by the number of abdominal segments with gills: Pteronarcys - first two segments with gills; Pteronarcella - first three segments with gills. Pteronarcys californica nymphs can be recognized from the two other species of Pteronarcys (P. dorsata & P. princeps) by the long, slender, and sharply pointed corners of the prothorax (segment immediately behind head).
Key Identification Characters - adult 3
- Two tails one half or less the length of abdomen.
- Wings heavily veined and grayish in color.
- Body color light to dark brown above and pale orange to bright orange below. Obvious orange band in front and behind prothorax.
- Remnants of gills present on first two abdominal segments.
- Very large. Body length (excluding tails) 40-50mm. Males noticeably smaller than females.
Nymphal shucks can help confirm which species of stonefly is emerging, and are therefore useful to collect along with the adults.
Similar adults: 3
The size and color of Pteronarcys californica make it distinct from most other stoneflies. Pteronarcys species also have gill remnants on the first two abdominal segments while species of Pteronarcella have gill remnants on the first three segments. These non-functional gill remnants on adults are easily seen with a small hand lens.
Habitat & Distribution 3
Nearly all stoneflies have a strong preference for moderate to fast riffles and runs with a large rocky substrate. This preference apparently reflects the need of stonefly nymphs for well oxygenated water. Salmonfly nymphs share this preference, and when present the nymphs will be found in riffles and runs. Though salmonflies occur throughout the West, many streams with good habitat lack good populations. When present they are generally quite abundant.
Like other areas of the West, Pteronarcys californica occurs across Oregon, but in many streams it is rare or absent. On some rivers, the lower Deschutes River for example, salmonflies thrive in large numbers producing legendary hatches.
Life Cycle - Emergence 3
Pteronarcys californica nymphs require two to four years to complete their development. As a result small immature nymphs can be found throughout the year in a range of sizes. Final instar nymphs (i.e. fully grown) begin moving from mid-channel riffles and runs to areas near shore a week or more before they crawl from the water and emerge into winged adults. Actual emergence typically occurs after dark. Depending on location and elevation emergence may begin as early as early May or as late as mid July. Generally emergence doesn’t start until the water temperature is close to 50 degrees.
Oregon Emergence Period: mid May to mid June.
Metolius: rare?
McKenzie: Present, but in sparse numbers.
Necanicum/Nehalem: Present, but sparse numbers at best.
Sources and Credits
- (c) Jerry Schoen, all rights reserved, uploaded by Jerry Schoen
- Adapted by Jerry Schoen from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Pteronarcys_californica
- (c) Jerry Schoen, some rights reserved (CC BY-SA)
