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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