Monday, December 2, 2013

A new "humpless" case-maker, one that's "imperiled" in the state of Virginia: Adicrophleps hitchcocki

First of all, let me be clear that I did not find this insect, and I did not take these photos.  This little case-maker was found yesterday by my friend who lives in Sugar Hollow and explores, in a regular way, those little headwater streams that empty into the Moormans.  It was found in a special stream that flows down the mountain by the side of her home, one that I've been to a number of times.  This one.

The species identification was suggested to us by Steven Beaty.  However, he cautioned that certain anatomical features were not revealed by her photos so he couldn't be totally sure of the ID.  In no way is he responsible for any claims that I make in this entry.

That being said, I'm fairly certain that this caddisfly larva is the "humpless case-maker" Adicrophleps hitchcocki, a species that NatureServe lists as "imperiled" in the state of Virginia.  (See:  Its existence is also attested in Connecticut, Pennsylvania, West Virginia, and Maryland.

I would base our ID on remarks made by Wiggins in Larvae of the North American Caddisfly Genera (Trichoptera), University of Toronto Press, 1977, pp. 52-53.  Four critical points.

1. Case description.  "Larval cases in Adicrophleps are four-sided, tapered, and constructed of pieces of moss arranged transversely; trailing ends frequently left attached to the moss pieces give the case a furry appearance."  (Wiggins, p. 52)  That matches our case exactly.

2. Habitat.  "Larvae were collected in several cold, rapid streams from 1 to 10 m wide from aquatic moss (Scapania) in riffle areas at depths not exceeding 30 cm;  they were exceedingly difficult to find in the moss."  (Wiggins, p. 52)   My friend is a moss specialist, and that is exactly where she found this case.  And remember, this is the stream in which it was found.

 Right width and depth and plenty of moss covered rocks.

3. Description of the head.  "The head of A. hitchcocki has light-coloured muscle scars and bears a pair of longitudinal ridges along the anterolateral margin of the frontoclypeal apotome."  (Wiggins, p. 52)  Right on the money.

4. Mesonotal sclerites.  In his key to Brachycentrids, Wiggins defines Adicrophleps in the following way:  "Each half of mesonotum subdivided into three separate sclerites."  If you look closely at our larva, you can see the three on the right side.

One other thing. Wiggins' illustrations on p. 53 show that this species has very long setae on the anterior and posterior edges of the mesonotum and on the anterior edge of the pronotum.  No question about it.

Other anatomical features that we could look for: 1) larvae have a short prosternal horn, and 2) according to Wiggins, "abdominal gills are lacking and the lateral fringe is absent."  To see those features, and thus be totally sure of our ID, we would have to preserve a larva.  We prefer not to do that when the species is "imperiled."  But, I see no reason to doubt this identification.

Very exciting!  I'll add this to our EPT list.  See postings for 9/8/12 and 10/8/12.

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