Little Yellow Stoneflies
.............................Fly Fishing Yellowstone National Park
05/18/08

Little Yellow Stoneflies (Perlodidae Family) - Nymphs












Little Yellow Stonefly nymphs are far more important than the adults. The species of the
Periodidae family differ in size but their basic color and shape is very  similar. Like all
stoneflies (with rare exceptions), the Little Yellow Stoneflies crawl out of the water to
hatch. The nymphs are much more susceptible to being eaten by trout when they
migrate from their normal locations down between and under rocks on the streambed to
the banks to hatch.
When there is no hatch taking places, the stoneflies are basically safe from the trout. It
is not unusual for one to become dislodged and subject to being eaten. They don't
show up that regular in drift samples; however, and I doubt it is a frequent occasion.
Behavioral drifts, which usually occur under low light conditions or during the night,
usually don't have substantial numbers of stonefly nymphs.
Of all the Little Yellow species, the Yellow Sallies provide the best opportunity for
anglers. They often hatch during the daytime, whereas many other stonefly species
hatch during the evening hours. Some of the Little Yellow Stonefly species that hatch
during very warm weather also hatch during the evenings.

Coming Up Next:
Little Yellow Stoneflies - Adults

Copyright 2008 James Marsh