» Genus Isoperla (Stripetails and Yellow Stones)
56 species aren't included.
This is page 2 of specimens of Isoperla. Visit the main Isoperla page for:
- The behavior and habitat of Isoperla.
Pictures of 13 Stonefly Specimens in the Genus Isoperla:
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.
Isoperla quinquepunctata (Little Yellow Stonefly) Little Yellow Stonefly Nymph
View 2 PicturesSize - (excluding tails) - 10 mm
Status at time of photo - preserved but no discernible color change as specimen was captured only a few days earlier.
Key characters - unique pattern on dorsal (Dorsal: Top.) head and thorax (Thorax: The thorax is the middle part of an insect's body, in between the abdomen and the head, and to which the legs and wings are attached.); dark medial (Medial: Toward the middle of the body.) terga (Tergum: the dorsal part of an abdominal segment or segments (terga). Also used to describe the entire abdominal dorsum or the thoracic dorsal segments of Odonata.) stripe between two paler stripes
This species is very common in west slope north Sierra watersheds. Richard W. Baumann & Boris C. Kondratieff did a study on the same section and at the same time of year (APRIL 25-29, 2010) where this specimen was taken. No other species of Isoperla were reported from this location and quinquepunctata was very abundant. Their hatches can be very heavy some Springs.