Saturday, December 27, 2014

Not a total waste anyway: a new Crane Fly larva, Dicranota sp.


I plan to do a lot of exploring this winter: new streams, new waters, and I hope some new insects.  That means getting into small streams higher up in the mountains.  This morning I tried a small stream that empties into the Doyles even though it wasn't all that remote.

Sort of struck out.  Oh, I found plenty of insects: large winter stoneflies (Taeniopteryx), some common stones (A. abnormis), some flatheads, one small minnow mayfly, and lots of Uenoids (all were the "tolerant" N. oligius).    The stream was in the woods at the top of a hill.  Still, there was a farm up above it, and the rocks -- and the insects as well -- were covered with silt.  Ugh!

One thing of interest: this little larva (10 mm), one I've not seen before.  From my live photos, it's easy to see the prolegs on the venter, but I needed a microscope photo to see if they were paired, and how many there were.


Five pairs on segments 3-7.


It took me awhile to find a Tipulidae (Crane Fly) with that exact number of prolegs, but there it was on pp. 776-777 of Merritt, Cummins and Berg (An Introduction to the Aquatic Insects of North America, 2008).

Paired prolegs (pseudopods) with sclerotized apical crochets (curved hooks) on venter of abdominal segments 3-7; larvae in wet to saturated soil along streams..... most Dicranota

As I recall, this one was in a pretty muddied up leaf pack.  However, if you look at some of the internet sources, you'll find that it's a fairly intolerant insect.  Tom Murray has posted a photo of one that was "netted from a fast flowing rocky mountain stream" (http://bugguide.net/node/view/264471/bgpage), and the North Carolina list of tolerance values gives a TV of 0.0 to Dicranota spp.  Maybe I need to see if I can get into this stream upstream from that farm!



From what I can tell, it's very difficult to key this one down to the level of species.

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