Saturday, June 11, 2016

Always a nice surprise: the "green stonefly" (Chloroperlidae), genus Alloperla

So small -- but so pretty.  Chloroperlid -- green stonefly -- Alloperla sp. I don't see this one often, but I have found them before in Buck Mt. Creek, my destination this morning.  However, in reading Beaty's description of Alloperla ("The Plecoptera of North Carolina," p. 27, Vers. 4) I discovered why they seem scarce.  "Alloperla and some other chloroperlids are likely under-collected due to the nymphs presence in the hyporheos."  (The hyporheos is "a region beneath and alongside a stream bed where there is mixing of groundwater and surface water." -- Wikipedia.)  Glad I've started to spend more time digging around in the substrate.

These stoneflies are small -- this one measured 6.5 mm -- but the green color helps us to spot them.  For the ID, "Nymphs 5.7-9.6 mm.  Head with posterolateral margins rounded with eyes large and set midlaterally;

pronotum with setae usually restricted to corners;

mesal portion of posterior margin of abdominal sternum eight lacking setae; middle and distal segments of cerci with a dorsal and ventral fringe of long setae, each segment with 2-6 long intercalary setae."  Don't have a real good photo of this, but this does show the numerous long setae on the distal segments.

Beaty doesn't note the feature that I thought was important: the inner edges of the wingpads angle away from the central axis of the nymph.

Species name?  Beaty advises us to stay at the level of genus noting: "North Carolina has a least seven species of Alloperla of which three are undescribed in the immature aquatic stage."  Well, that means that four species have been described, so I'll have to do some research to see what I can find.  In the meantime, the known species are atlantica, chloris, lenati, nanina, neglecta, petasta and usa.


Actually, my goal today was to find more Perlesta -- and I did.

Hope to say something soon on distinctions I'm noting on the Perlestas from various streams

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