Closeup insects from the Lower Yuba River
Female Skwala curvata (Large Springfly) Stonefly Adult
View 2 PicturesThis female dropped her eggs just before this photo was snapped. The distinctive notch in the subgenital plate identifies the species. An interesting observation is how active they get when exposed to direct sunlight. Trying to stage this specimen was most difficult. In the shade it would calm right down, but when exposed to direct sun it would immediately go nuts, scampering all over quickly without pause. Perhaps this explains why they don't seem to be found out and about on overcast days, but if the sun peeks out... She was 24 mm long, head to wingtip. Hesperoperla pacifica (Golden Stone) Stonefly Nymph
View 1 PicturesThis monster started to feed within a few minutes of sharing the inspection tray with its victims. This nymph is a voracious predator of small invertebrates and has even been noted for feeding on small fish and salmonid alevins. The niche it fills in fast water is equivalent to the Dragonfly nymphs that inhabit slower water.
Hesperoperla pacifica nymphs are easily distinguished from other western perlids by the presence of anal gills (obfuscated by algae in the tray) in combination with an hour glass shaped pale mark on the front of their heads.
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