Saturday, May 7, 2011

Exploring New Waters: Finding More Treasures

Today a friend took me to yet another trib to the Moormans that, like the others I visit, stays unnamed -- it's on private land.  I collected a lot of neat bugs, got ready to take some pictures, and proceded to tip over my container!  Yuck!  But I did manage to hold on to this one (and a few others).

This is a spectacular Limnephilid -- Northern case-maker caddis -- genus Pycnopsyche.  This is the genus that often makes a three-sided case out of leaves when it's small, but it turns to other construction materials as it matures.  Here's a perfect example of that.  The back of the case is still the three-sided case made of precisely clipped sections of leaves: the front of the case is made out of pebbles.  Case-makers do not abandon their cases as they outgrow them; rather, they enlarge their cases by adding things on at the front.  Here's a good look at the case on its own.  (The case, by the way, was 1 1/2" long, and the larva was an inch long.)

A thing of beauty.  All of these building blocks are "glued" together with the silk that the larva produces inside its body; the silk is generated by special silk glands at the front of the head.    Although it's sometimes difficult to get these larvae to stick their heads out for a picture, this one almost crawled right out of its case as I was watching.

I was fairly certain of the Pycnopsyche identification.  Nonetheless I preserved this so I could check it out in my lab (and, yes, I wanted it for my reference collection!).  Pycnopsyche for sure.  The two key features again:  1) sclerites at the back edge of the lateral humps; and 2) the "SA1" metanotal sclerites are not fused.  Here are the photos for confirmation.

This stream -- like just about all of our streams at the moment -- was loaded with spiny crawlers, genus Ephemerella.  I'll spare you the photos.  But I also collected: Common stoneflies, Roach-like stoneflies (lots of them), a free-living caddisfly (creamy white color), several common netspinners (genus Diplectrona), a "small" Giant stonefly, and lots of flatheaded mayflies, genus Epeorus.   I did get a good photo of one of those.

This one still has a while to go before it thinks about hatching.  I also found several Perlodid stoneflies that I think are the same genus and species that I found at the Rapidan River on Thursday.  Here's a look.

This nymph is more mature than those that I found on Thursday (note the spread in the wing pads), and under the microscope, the brown stripes on the abdomen that are typical of Isoperlas were very clear.  So, I do indeed think we've run into yet another species of Isoperla -- I think there's a very good chance that it's Isoperla transmarina (I'll keep you informed).

As I headed back into town from Sugar Hollow, I decided to have a brief look at the Doyles River, hoping to find a new brood of small minnow mayflies.  I didn't succeed.   I did see a lot of Epeorus flatheaded mayflies and some of our new species of Isoperla.  But I also found a fair sized Polycentropodid -- a "trumpetnet" caddisfly larva.  We don't see too many of these, though I think that volunteer samplers often record them as fingernet larvae.  Here's a decent photo that I managed to take -- actually, it's the first time I've gotten a live shot of this insect.

Samplers often take one look at the burnt orange head and write this off as a fingernet.  But there's not a hint of yellow or orange in the body (as there would be were this a fingernet).    Polycentropodids are either creamy white, like this one, or a pale shade of tan.  But the key thing to note is the head.

The "freckles" that cover the head are called "muscle scars," and "muscle scars" are a distinguishing trait of this caddis family.  The other feature that helps us to make this identification requires the use of the microscope.  The "fore trochantin" -- sort of the front shoulder blade -- is pointed.  Have a look.

One final note on this insect.  The genus is Polycentropus -- the only genus I've seen around here.  How do we know?  Well, it's a case of "X marks the spot".  A Polycentropus Polycentropodid has a black X on the back of its anal proleg.

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