Friday, January 30, 2015

Cabin fever sets in -- time to get to a stream

The wind and cold couldn't stop me this morning.  With no warm weather in sight, I decided to brave it and check out a small stream in Sugar Hollow.

I was hoping to find two different things, and I found both.  That's one in the photo at the top of the page: the free-living caddisfly larva, Rhyacophila banksi complex.

I've found this species before in this stream, along with R. fuscula, R. nigrita, R. glaberrima and R. carolina.  This is the best stream I know of for finding Rhyacophilids.    This larva matches the description for the species R. banksi, but entomologists feel R. banksi can't be distinguished from a number of similar species.  Hence, "R. banksi complex" (which belongs to the R. invaria group).

On January 28 of last year, I posted a thorough review of how we arrive at this identification.  There's no need to go over that detail again.  But, two of the features that nail this down are

1) There is a single, large, ventral tooth on the anal claw,

and 2) the second segment of the maxillary palp is twice as long as the first.


My second goal was to find one of those Isoperlas that I think might be I. kirchneri (see the entry of 1/25) -- and I was successful.

Whatever species it turns out to be -- I. montana, I. kirchneri, or something else -- this is the same nymph that I've found here in previous years: no "bars" or "stripes" behind the ecdysial suture.

Since I had none of these in my collection, I preserved it so I could see what the lacinia looked like.  But, nothing unusual there: same shape and make up that we normally see on most Isoperlas.

This was a young one.  Have to get back here in March and April to see one that's mature.


The most common taxon today?  Not much question about it: the large winter stonefly, Taenionema atlanticum -- and this one was fairly mature.

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