Tuesday, October 8, 2013

Off to Sugar Hollow: The first Perlodid stonefly of the young season, Malirekus hastatus

This is not something I expected to find in Sugar Hollow this morning, but it was the very first insect that I picked up.  The Perlodid stonefly, Malirekus hastatus.  The small stream that I went to is a stream in which I've found them before.  This is one that I collected there on February 13th, 2012.

Gorgeous!  But it's also a "killer."  Don't put these in a tray where you're keeping small mayflies!

A quick review of how this one is ID'd.  "Nymphs 15-19 mm; distinctive pale "M" pattern on head; conical submental gills; triangular lacinia with low marginal knob bearing a tuft of setae and venral surface with a cluster of approximately 50 clothing hairs near base; single curved row of spinules on back of head, obsolete near midline."  (Steven Beaty, "The Plecoptera of North Carolina," p. 26)  Those features look like this.

1. head pattern (for a detailed description, see Stewart and Stark, Nymphs of North American Stonefly Genera, pp. 416-417)

2. conical submental gills

3. triangular lacinia

4. clothing hairs on ventral lacinial surface

5. and the row of spinules on the back of the head

So, the Perlodid stoneflies are here -- my favorite time of the year!

But I was in for another surprise when I found this very small mayfly.

It's the spiny crawler, genus Eurylophella.  What on earth is it doing here now?  This is an insect I expect to see in the spring, but here it is in October.  The key feature marking the Eurylophella genus ID is already easy to see: the large operculate gills on segment 4, the gills that cover those on segments 5-7.

Given its size -- 2.5 mm -- I doubt that I'll be able to determine the species.  The species I see in Buck Mt. Creek is E. verisimilis.  But my friend who explores these small streams in Sugar Hollow in a regular way has found E. funeralis as well.  I'll have to give the ID a try.

What else?

1. Giant stoneflies, Pteronarcys proteus.  They are plentiful in this stream, and some, like this one are starting to get pretty big.  (Note small "Roach-like" stonefly [Peltoperlid] riding on its side.)

2. Common stonefly, Eccoptura xanthenses.  Also a species we commonly see in these small mountain streams.

3. And a few common netspinner caddisfly larvae: Diplectrona modesta and Hydropsyche betteni.  (Note the low, rounded tubercle at the back of the head on H. betteni.)


Perlodid stonefly, Malirekus hastatus.

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