Tuesday, November 11, 2014

A significant find in Sugar Hollow: new taxon -- the "hooded-case maker" (Molannidae), Molanna blenda

While I was taking advantage of our beautiful weather to play some golf yesterday, my friend in Sugar Hollow was adding a new caddsifly to our EPT list for central Virginia: the "hooded-case maker" Molanna blenda.

Molannidae is often found in still water -- "lakes or the slower currents of rivers and streams" (Wiggins, p. 290), where they are not often easy to find since they "inhabit the sand and mud substrates of these sites."  (Wiggins, Larvae of the North American Caddisfly Genera, 1st ed., p. 290)
But they can be found in "cool spring-fed streams" (Beaty, "The Trichoptera of North Carolina," p. 96) which is where this one was found.  It was on a rock, covered with silt, but gave itself away when it moved.   The stream is that special 1st order stream that flows close to my friend's home.  This one.

Hooded-case makers get their name from their cases -- which indeed have a hood, or "cowl," at the anterior end, and the case is "flanged" on the sides.  Ames notes that the cases also have "a ragged posterior opening on the dorsal side" (Thomas Ames, Caddisflies: A Guide to Eastern Species for Anglers and Other Naturalists, p. 206).   E. g.

dorsal view

ventral view

As you can see, the hood almost completely covers the head of the larva.   For the genus ID -- and there's only one genus in our part of the country, Molanna -- we need a close look at the claws on the hind (metathoracic) legs.  Beaty, "Claw of metathoracic leg shorter and more stout than claws of other legs and setose." (p. 96)  I think we can see that in this live picture (my friend prefers not to preserve any insects).

Beaty's description of M. blenda reads as follows: "larvae 10-12 mm; apex of base of tibial spine extends well past tibiotarsal joint; membranous area at constriction of frons capitate; moderately wide black banding along frontoclypeal and coronal suture."  ("Capitate" means "abruptly enlarged and globular.")  I can't make a call on the tibial spine, but the "enlarged globular" membranous area at the front of the head is very clear in our photos as are the wide black bands that border the frontoclypeal suture.  Another view.


Very cool.  Obviously it's time for me to get my priorities straight and get back to the streams!  Still, it's so nice to play golf at this time of year :)  (Behind the 9th green at Meadow Creek golf course in Charlottesville.)


(Please note that all photos of the Molanna were taken by my friend and posted with her permission.)

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