Thursday, February 7, 2013
Neophylax concinnus as the Uenoid I found at the Doyles: Making the case
The Uenoid caddis that I found yesterday at the Doyles appears to be Neophylax concinnus. I'm not yet totally certain of this ID, but the evidence that I've compiled points strongly in that direction. Let me make the case as I see it, approaching the issue in three different ways.
I. Elimination of other choices.
Steven Beaty's description of N. concinnus is brief: "without clavate ventral gills on abdominal segment 1." ("The Trichoptera of North Carolina," p. 86) That is certainly true of this larva. Have a look.
I. e what is missing are these -- the balloon-shaped gills we find, for example. on N. oligius.
Of the Neophylax species that Beaty describes (pp. 86-87), only four lack clavate gills: N. aniqua, N. concinnus, N. toshioi, and N. fuscus. Of these, N. aniqua and N. toshioi both have a "prominent tubercle on [the] head, often semi-blunt." (Beaty, pp. 86-87) The tubercle on N. aniqua looks like this:
There is no such tubercle on the larva I found yesterday. There "might" be a very small, "pimple-like" tubercle on the head, but if there is, it's too small to show up in any photo I've taken. But we can eliminate these three other species in additional ways. N. aniqua, you will recall, is found in first order/headwater streams: this larva was found at a downstream location in the Doyles, close to its confluence with the Moormans. N. toshioi, in addition to having a prominent tubercle on its head, has a head with a "pale eye stripe laterally" (Beaty p. 87) -- not true of our larva -- and it has "lateral gills on abdominal segments 2-5." Our larva appears to lack lateral gills. Finally, N. fuscus, like N. aniqua is a "headwater" taxon which is "relatively rare." (Beaty, p. 87)
II. Confirmation of key features.
In. R. N. Vineyard, G. B. Wiggins, et.al., The Caddisfly Genus Neophylax, p. 46, we read: "Among larvae lacking gills on abdominal segment I [i.e. clavate gills], that of N. concinnus is distinguished by a combination of traits: short spines along the anterior margin of the pronotum, frequent presence of a small frontoclypeal tubercle, and pronotum with microsculpture of transverse rows of spicules."
1. There are short spines on the anterior margin of the pronotum of our larva. But they are not easy to see through the layer of silt at the pronotum's edge.
2. As noted before, there "may" be a small frontoclypeal tubercle on our larva -- I'm not really sure. However, the word "frequent" suggests to me that the tubercle is not always there and certainly not prominent.
3. And I think I can see a "microsculpture of transverse rows of spicules" on the pronotum. The tiny black dots on the pronotum are very small spines.
This source also notes that there are spicules on the posterior of the mesonotum. Those are quite clear in this photo.
III. Location, location, location
Vineyard, et.al., note that N. concinnus "occupies a wider array of habitats than any other single species in the genus" but that "it is generally found in small second- and third-order streams." (p. 48) I'd say that the Doyles fits into that group; I'd call it a second or third order stream. Of greater interest still, this source notes that "Beam and Wiggins (1987) found that in southern Ontario streams N. concinnus occupied the longitudinal zone between N. aniqua (upstream) and N. oligius (downstream)." (p. 48) Perfect! The N. aniqua larva I found was in a small stream in the Blue Ridge; the Doyles River near Whitehall is about 3 miles east of the Shenandoah National Park; and Buck Mt. Creek, where I normally find N. oligius larvae is about 10 miles more to the east. So stream size and location also work in favor of this ID.
As I've already said, for me, at the moment, this ID is a tentative one. I'll be sure to return to the Doyles very soon to see if I can find better samples.