» Order Plecoptera (Stoneflies)
1 family isn't included.
This is page 12 of specimens of Plecoptera. Visit the main Plecoptera page for:
- The behavior and habitat of Plecoptera.
- 6 underwater pictures of Plecoptera.
Pictures of 147 Stonefly Specimens:
Suwallia pallidula (Sallfly) Stonefly Nymph
View 6 PicturesThis specimen keys out to Suwallia, for which I did not find any nymph species keys. However, I'm placing it in Suwallia pallidula because I caught a few adults in the same spot that closely resembled the abundant nymphs and keyed them out to species. Features I noted under the microscope when keying this specimen to genus included apical (Apical: Close to the apex; tip or end.) hairs of cercal segments that were directed at posterior (Posterior: Toward the back of an organism's body. The phrase "posterior to" means "in back of.") angles, and the longest apical (Apical: Close to the apex; tip or end.) hairs of distal (Distal: Far from the point of attachment or origin; near the tip.) segments were shorter than their following segment. Female Isoperla fusca (Yellow Sally) Stonefly Adult
View 13 PicturesThe family ID on this one was a little bit tricky. Just going by the size, shape, and color, it looks like Chloroperlidae. However, the second anal vein of the forewing is does not appear to be forked, and the apical (Apical: Close to the apex; tip or end.) maxillary palpal segment is close to the length of the penultimate segment, both of which rule out that family. The position of the cubitoanal crossvein (Crossvein: Short cross-wise veins in an insect wing which connect the long longitudinal (length-wise) veins.) relative to the anal cell in the forewing -- touching it in this case -- indicates Perlidae (and it really doesn't have the "look" of Perlidae at all), but other characteristics, such as the metathorastic sternacostal sutures and lack of gill remnants, point to Perlodidae. That's the right answer. Moving on to Perlodidae, the key characteristics in Merritt & Cummins lead straightforwarly to Isoperla, and the species key in Jewett 1959 (The Stoneflies of the Pacific Northwest) leads to Isoperla fusca.
There is one caveat: That source does suggest a May-July emergence, whereas this one was collected in mid-September.