Sunday, September 21, 2014

Entry Run yields a Goerid (Weighted-case maker) with an uncommon case

I wasn't sure what to make of this case when I saw it this morning.  This kind of case is common with the Uenoids -- 4 large pebbles on either side of the case used for ballast, and a case that is tapered.  But this case was big -- 16 mm -- much too big to be a Uenoid, and in any event, it's pretty early to see a Uenoid.  Of course, it' not too early to see Goerids (Weighted-case makers): you'll recall that I found this one last week at the Rapidan River

and I found this one this morning in South River, right next to Entry Run.

But Goerids, as we can see from these photos, have "squarish/rectangular" cases with 2 stones on each side, not 4.  There was simply no doubt that this one had 4.

But when I started taking my photos, it was clear that I had found a Goerid, just one with a very unusual case.  As I was taking the photos, I could see the sharp anterolateral points on the pronotum and the mesonotal anterolateral projections, hallmarks of this genus.

When I got home, I re-examined my sources which had this to say on the cases made by Goerids.

Beaty ("The Trichoptera of North Carolina," p. 87): "Case: Similar to that of Neophylax [i.e. Uenoidae] but with a continuous row of larger ballast stones laterally, usually two."

Wiggins (Larvae of the North American Caddisfly Genera, p. 226): "Case: With a row of larger pebbles along each side of the central tube of small rock fragments, larval cases of Goera are similar only to those of Neophylax in North America.  Generally, Goera cases have fewer and larger ballast stones on each side, usually two; Neophylax cases usually have smaller ballast stones, thus more than two."

Ames (Caddisflies: A Guide to Eastern Species for Anglers and Other Naturalists, p.232): Their cases have lateral ballast stones similar to those of Neophylax in Uenoidae, but they are more symmetrical and rarely have more than two stones on each side."

So, lesson learned Goera cases -- on occasion --  can have more than 2 ballast stones on the sides.

Both of the Goerids I picked up this morning turned out to be Goera fuscula -- a "rare" species according to Beaty.  Key features: "4 pairs of sclerites on metanotum; sternal thoracic plates distinct."

Here we can see the 4 sclerites on one side of the metanotum

and the sternal thoracic plates look like this.


Not much else to get excited about today at the stream -- which is typical for this time of year.  But I did find a young Pteronarcys biloba Giant stonefly.  Previously, I've seen nothing in Entry run but Pteronarcys proteus.

The "lateral projections" on the abdominal segments of this particular nymph were really impressive!

And as I suspected, I saw a lot of Strong-case makers, Psilotreta labida.


Fun day.  Love it when we learn something new.  Goera fuscula.

dorsal view of case:

ventral view of case:

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