Thursday, June 7, 2012

As Promised -- an Adult Perlesta stonefly: a Mix of Good Insects at the Lynch River This Morning

Fly fishermen call adult common stoneflies (Perlids) "Golden Stones," obviously for very good reasons.  While I can't swear that this is a genus Perlesta golden stone, I'd be willing to put money on it.   Perlesta nymphs are common in a lot of our streams at the moment -- as you know if you've been reading along --
and I can't really think of anything else this would be.   Some more photos of this beautiful terrestrial insect.

And here's another look at the nymph that turns into this insect when it hatches.

I found quite a few of these nymphs, mostly by looking in leaf packs, and I also saw a lot of "shucks" on the rocks, "skins" left behind by those nymphs that have already hatched.  But I also found a Perlesta nymph that I feel sure must be a different species than the one that I commonly see.

Note the dark bands crossing the abdominal tergites, the dark spots on the pronotum, and the dark area on the head in front of the rear ocelli.  Sure wish I could say this is a different species for sure, but, as you know, most Perlesta nymphs remain "undescribed".

There were some other treasures today: it was a very satisfying trip to the stream.

1. Another genus Alloperla "green stonefly" (Chloroperlid): I've now found these lime green nymphs in three different streams.  This is the first year that I've seen them.

2. Small minnow mayflies: most were Plauditus dubius, but I also found a second Baetis flavistriga nymph, on which, see the entry from yesterday.

Plauditus dubius, male:

Plauditus dubius, female:

Baetis flavistriga, female.  (The one I found yesterday was a male.)  Note the paired "kidney-shaped spots" on the abdominal terga and the medial band on the tails.  This photo is much clearer than those I was able to get yesterday.

3. A flatheaded mayfly, genus Maccaffertium.  This was a fairly large specimen, and the wing pads were already long.  I'll work on the species ID.  Maccaffertium ithaca should be around at the moment, but I'll have to see what I can find in our keys.

4. And a Darner dragonfly nymph, the first I've seen this season.

The long, thin shape of the nymph is one of the keys to family ID.  But the critical thing is the shape of the prementum -- it's wider at the front than it is at the back.  (You'll need to put the nymph on its back to see this.)

We can ID this to the level of genus: Boyeria.  One of the distinguishing features of Boyeria Darners is the way the paraprocts curve inward at the tips.

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