Friday, March 22, 2013

Predators! Feeding Perlodids and Chloroperlids in Sugar Hollow

Back to Sugar Hollow this morning to explore a jewel of a stream that pours down the mountain near the home of my friend.  The water there is crystal clear.

We didn't find a lot of insects in the leaves and the rocks, but I was pleased to see some fairly mature Chloroperlids (green stoneflies) -- pictured above.  Note how the inner edges of the wing pads diverge, and note the dark hair that covers the wing pads and abdominal segments: both are indications of genus Sweltsa.

I also picked up a nice Ameletid mayfly (Ameletus lineatus, I think -- never got a chance to check it for sure) and a Perlodid stonefly, Isoperla similis.  This little beauty.

But I wasn't vigilant when it came to keeping an eye on the bugs in my tray.  As a result, I never got a chance to photograph that nice Ameletid: before I got to it my "nice" Perlodid got ahold of its throat!

And I noticed a black fly larva as I was taking my photos -- but my Chloroperlid noticed it too!

Little did he know that he'd be sharing that larva with the I. similis nymph.  Between them, they disemboweled it.  Ugh!


If you read this blog in a regular way, you know that this is not the first time that this has happened.  In the winter of 2011, I lost a small minnow mayfly (H. amplum) to a voracious C. clio Perlodid:

Then last fall, a Perlid (common stonefly) bit into a common netspinner while I wasn't watching.


Perlids (common stoneflies), Perlodids (Springflies/Stripetails), and Chloroperlids (green stoneflies) are predaceous -- they like to eat meat.  And they're not very choosy when it comes to picking their prey.  I've noticed a preference for small minnow mayflies (!), but as we can see, black fly and caddisfly larvae will do perfectly well!  And, they will go after each other.  The Chloroperlid in the photo above was chased a couple of times by that I. similis nymph before they both took that black fly to lunch.

The "mouths" of Perlids, Chloroperlids and Perlodids have rather powerful-looking glossae(g) and paraglossae(p) which I suspect are designed for tearing things apart.  Have a look.

Perlid labium:

Perlodid labium:

Chloroperlid labium:

Compare those with the p and g of a large winter stonefly, a stonefly that lives on a diet of algae and leaves (they're shredders, collectors and grazers).

In any event, lesson learned once again -- always carry two trays for collecting your insects!

Note:  The I. similis Perlodid remains one of my favorite stones in terms of its colors and patterns.  We should see mature nymphs this month and next.  My best photos of this particular species date from 4/13/11.  The two nymphs below were in the same stream we went to today.


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