Aquatic Insects of Central Virginia: Photos from the Rapidan River

I went up to the Rapidan River on Monday to see if I could find any insects. The water was high and fast, but I found quite a few things in balls of vegetative matter close to shore.

At the top of the page, a pretty cased caddisfly that really drew my attention. The case looked a little unique, and at first I thought it might be a species I'd not seen before.

I preserved it and went home to do some microscope work. The first thing to check was the lateral hump which looked like this.

The orange sclerite behind the hump signaled genus Pycnopsyche. Since I often find Pycnopsyche scabripennis up there in the spring and summer, that immediately came to mind. But the case looked somehow different. At issue, the sticks extending back from the top of the case. This brought to mind P. guttifera, a species that often makes this kind of case. From the descriptions of Pycnopsyche larvae in Beaty's manual ("The Trichoptera of North Carolina," pp. 84-85) it became clear that the choices were guttifera or scabripennis. These species share one thing in common -- both have "2 major setae" on the "ventral margin of the femora" (Beaty, p. 85). That I could see.

(Note that the large setae behind these two is actually on the dorsal side of the femur.) But, the species differ in one significant way -- on the venter of the first abdominal segment, there are more than 15 setae on guttifera, while on scabripennis there are less. Microscope photo.

I've pointed to three of the setae; in all I counted ten. So, I guess it was P. scabripennis after all, just a young one with much room to grow.

Since I was so intent on getting good pics of the caddis, I totally ignored the spiny crawler mayfly that was hitching a ride on its case. Pretty sure it was Ephemerella invaria, but I should have preserved it just to be sure. Very unusual colors.