Friday, January 2, 2015

A rare one this morning: the "humpless case-maker" (Brachycentridae), Adicrophleps hitchcocki


I did not expect to see this this morning, and I didn't know what I had when I headed back to the car to start taking photos.  I was digging around in a very small stream/spring seep at high elevation in Sugar Hollow, sifting through gravel, hoping to find another Theliopsyche (see the posting for 12/21).  I picked up this case -- not even sure that it was a case -- until I saw a little brown head sticking out.


It was only when I looked through my camera that I knew what it was: the "humpless case-maker," Adicrophleps hitchcocki.  This is an insect that is listed as "imperiled" in the state of Virginia (http://eol.org/data_objects/28878539), but it's the second larva that we've found in Sugar Hollow's small headwater streams.  You may recall that my friend found one in December, 2013, and I posted an entry describing the find on 12/2.


Her photos were excellent -- and taken with a 65 mm lens (I use a 60 mm) -- and I encourage you to look again at that entry.  But to review...  since this larva hasn't been found in NC, we use the Wiggins book for our detail (Glenn B. Wiggins, Larvae of the North American Cadddisfly Genera, 1977 [1st edition], pp. 51-53).

1. There is only one Adicrophleps species -- hitchcocki.

2. To date, A. hitchcocki has only been found in Connecticut, Maryland, Pennsylvania, Virginia, and West Virginia.  (See Nature Serve Explorer.)

3. Wiggins keys out the genus in following way: "Each half of mesonotum subdivided into three separate sclerites, posterior margin not conspicuously raised or coloured." (p. 51)  (Note that the separation between sclerites 2 and 3 on each side is difficult to see, but they are distinguished by color.)


4. To this Wiggins adds, "The head of A. hitchcocki has light-coloured muscle scars and bears a pair of longitudinal ridges along the anterolateral margins of the frontoclypeal apotome." (p. 52)  Both features are clear in this close-up.


Actually, those ridges on the sides of the head are visible in one of my photos.


5. On the case -- "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."  We can see that in all of our photos, and the transverse arrangement of the moss pieces shows up nicely in the photo that shows us the ridges.

6. I also noted in my post of 12/2/13, that in Wiggins' illustration of the larva on p. 53, it is clear that there are very long setae on the anterior edge of the pronotum.  No question about it.  (Also note the "divot" in the pronotum, a defining trait of the family.)


7.  One final point.  On the habitat -- "Larvae were collected in several cold, rapid streams from 1 to 10 m wide from aquatic moss in riffle areas at depths not exceeding 30 cm; they were exceeding difficult to find in the moss."  As I mentioned, I found this little larva (case was 6 mm long) in sand and gravel, and this was the stream.

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That was a treat... and what a nice way to start the new year!


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