the nymphs after hatching from the eggs go through instars where they shed the exoskeleton as they grow. most may flies go through 5 to 7 of them in the course of their lives. Thats when you can find them in a white state. just like a blue crab does in a way...mmmm soft shell crab sandwich ( sorry no lunch) stone fly's go through it, most of the Perla were small so still have to shed and grow. A lot of the other nymphs were so small didn't even collect any (size 24-28) when fully grown will be (14-20).
csoult----different in the species..and seasons..early season hatches will have gone through a few before winter, while later in the season flies will still be in egg stage or one instar till spring and summer when they will grow..reason to carry flies in different sizes through the season. minnows are the same, right now all adults, then in late spring/summer you see alot more smaller ones then in fall they are large again...and ya all wonder why I carry so many boxes...lol
There's a small nymph in the last picture of your hendrickson post. Right by the stonefly.
Thanks for this Sandfly. I think most people have some basic knowledge of adults, but nymphs can be very tricky for most. I know I can tell just a few apart, but my knowledge is lacking in this area.
ryguy, small immature yellow sally probably 2 instars to go, maybe next years crop hard to tell with them since full grown they are a 14-16..that one would be a size 24 right now, did find some in the 20-18 size too.