Monday, August 2, 2010

Skipper Mystery Solved

Every year at this time, I get one or more of these "little brown thingies." I'd always labeled them as Tawny-Edged Skippers, Polites themistocles.


Trouble is, Crossline Skippers P. origenes can look like this as well. So which is it?

Here were the shots from above, first the male and then the female.



The evidences in favor of Tawny-Edged were

(1) TEs are usually flat brown on the hindwing below. Crosslines usually have a spot-band around the edge of the disc. Confusingly, TEs may have a hint of spot-band, and Crosslines may not have it.

Example of Crossline(?) with spot-band.

In my case, I was looking at six individuals which uniformly showed no spot-band or maybe the barest hint of one.

(2) TEs are small, the size of Peck's Skipper. Crosslines are larger, the size of Dun Skippers. My individuals were all smallish.

Here's a size comparison:


On the other hand, the following evidences favored Crossline:

(3) Crosslines are the more common of the two.

(4) Crosslines are more likely found in yards and meadows; TEs on the edges of wet meadows.

I posed this question to several knowledgeable folk and got opposite answers. What to do? The answer came in the form of an article by Nick Grishin describing how to differentiate these two species by examining the genitalia of the male.

Quoth my wife: "You have got to be kidding me!"

So: I reverted to my childhood, got a net, and captured two males that were a little worn. They were placed in an ad-hoc killing jar, and their abdomens prepared for examination under the microscope. Here were the results:




With reference to Nick's article, can you make the call?


1 comment:

Scott said...

That's Tawny-edged Skipper genitalia if I've ever seen it!