Friday, April 27, 2012

Cinygmula subaequalis: Back to the South River

It was sort of "the day of the flathead" up at South River: the bottoms of rocks were covered with Epeorus pleuralis, Epeorus vitreus, and this little beauty, Cinygmula subaequalis.  To date, this is still the only place where I've seen Cinygmula nymphs.  This is a genus you can pick out with a good loupe by looking down at the head.  The maxillary palps are visible at the sides of the head, as is the fact that the front of the head is emarginate.

This is a species we only find in high quality streams: tolerance value, 0.0.  And I can attest that they are hatching.  On one of the nymphs I picked up, the wing pads had already separated and lifted up from the body revealing the adult wings underneath ready to unfurl.

The Epeorus vitreus nymphs that I found were very large, and they were brown:  the E. vitreus nymphs that I'm used to seeing are a greenish yellow.

Remember that we can pick out this species by the four, irregular shaped spots at the front of the head. (Please click to enlarge.)


I found a real mix of insects today, though here, as elsewhere, there were more spiny crawlers than anything else.  To my surprise there were still a lot of Isoperla namata Perlodids: in Albemarle county they've become pretty scarce.  Some photos.

1. Common netspinner larva: Diplectrona modesta (the species we only find in good streams).

and with a spiny crawler

2. Two very colorful and elaborately patterned spiny crawlers, both E. dorothea.

3. A Nemourid stonefly, genus Amphinemura -- with wing pads that are starting to flare away from the body.  Note the "cervical" gills sticking out from the neck (bright white).

4. And one of many Isoperla holochlora nymphs that I saw, one that's much less mature than those I found on Tuesday at Powells Creek in Crozet.


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