Thursday, January 10, 2013

Another new caddisfly family: Goeridae, genus Goera

(Note: I did not take the photos posted in today's entry.  As I've mentioned before, I have a good friend who lives in Sugar Hollow who shares my entomological passion, and the two of us always share photos and information on all of our findings.  This is a caddis larva that she found on Tuesday in a small mountain stream near her home.  All photos are of the live insect, taken with a 65 mm macro lens.  The insect was safely returned to the stream.)

This new -- for us -- caddisfly larva is a member of the Goeridae family, and we're quite sure it's genus Goera.   Goera, like Apatania, was once considered a genus in the Limnephilidae family (The Northern case-makers).   Apatania, you will recall, is now one of five genera in the Apataniidae family, and Goera is one of four genera in the newly created family Goeridae.  (See Glenn B. Wiggins, Larvae of the North American Caddisfly Genera (Trichoptera), 1977, pp. 226-227, and pp. 228-229 in the second edition of that work, published in 1996, University of Toronto Press.)

Beaty ("The Trichoptera of North Carolina," p. 87) describes Goera in the following way:

Genus Diagnosis: Two pair of sclerites on mesonotum; pronotum produced anterolaterally into wide, sharply pointed processes; abdominal gills with up to 3 filaments; ventral and dorsal chloride epithelium present on abdomen; head pointed anteriorly and with many secondary setae.  Small streams to medium sized rivers, in riffles on rocks.

Case: Similiar to that of Neophylax but with a continuous row of larger ballast stones laterally, usually two.  Case also tends to be smoother in exterior texture.

Since this larva was not preserved, it was not removed from its case.  Therefore, we cannot show you the abdominal gills, nor do we have photos of the chloride epithelium abdominal marks.  The presence of the gills is important since Goera has them, Goerita, another genus, does not.  However, Goerita larvae are very small -- 4 - 6 mm -- this larva was in a case that measured 9 mm X 11 mm.
Also, the Goera case illustrated in Wiggins (Larvae, 1977, p. 227) matches the case that we found; that of Goerita (p. 233) does not.  We're convinced that Goera is the right call to make.

Back to our Goera description -- the pointed anterolateral pronotal projections are very clear in the photo at the top of the page, as are mesonotal anterolateral projections.  

For the two pairs of sclerites on the mesonotum, let's use a different view. 

The "pointed" head shows up clearly in the following photo.

Finally, let's have a look at the case.

It seems very clear that this case is damaged: the large ballast stone that ought to be there to match the one on the right has been knocked off.  But, yes, Goera cases have two sizable pebbles on each side: Uenoid cases, remember, have three are four larger side pebbles, but they're not nearly this large.  Ames (Caddisflies, p. 231) uses the common name "Weighted-case maker" for Goeridae, which seems very fitting.  

For those of you out looking for insects in streams, this is very important: Uenoids, Apataniids and Goerids all have these cases of sand grains and pebbles, they're all out there right now, and they often occupy the very same rocks.  Still, the shape of the case, and the number and size of the pebbles on the sides of the case will help you to tell them apart.

Can we ID this to the level of species?  There are two possibilities: G. fuscula or G. stylata.  Both taxa are found in the mountains, both are large (8-11 mm), and both have 4 pairs of sclerites on the metanotum.  That's what we find on our larva.

How do they differ?  G. fuscula -- "...face with central area smooth; posterior carina sharp and high."  G. stylata -- "...face covered entirely with spicules; posterior carina low and broad."  (Beaty, p. 87)  

This is a toughy.  Since the face of our larva looks to us to be pretty smooth, we are tempted to go with G. fuscula.  But we're holding off on species ID for the moment, since we're not yet sure about the shape of the carina.  See what you think.

It's certainly "broad," but to know if it's "sharp and high" or "low," we simply need more information.   We'll certainly be collecting more larvae.  But -- it's Goeridae, Goera, and possibly Goera fuscula.  Another taxon to add to our EPT list of central Virginia.

Below:  Photos of the stream in which this larva was found.  A small mountain stream, fairly high elevation, a tributary to the Moormans River in Sugar Hollow.

1 comment:

  1. Thanks again for the earlier photos that we used on the Wiki site. These shots are great. I particularlly like the Neophylax shots; I do ecological work on them periodically. I'll plop a link into the Trichoptera facebook page where even more folks can appreciate them. You might enjoy the Trichoptera conference - they move around the planet every 4 years and the next one may end up in New Jersey.