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Pyrgotid fly from 2013 gathering in AZ - Sphecomyiella nelsoni

Pyrgotid fly from 2013 gathering in AZ - Sphecomyiella nelsoni
Madera Canyon, Pima County, Arizona, USA
July 26, 2013
Came to lights on 2nd night of the 2013 BugGuide summer gathering in AZ.

This keyed clearly to Sphecomyiella in the MND(1), and to species S. valida in the 1978 treatment of Pyrgotidae by Steyskal (which can be read online here).

However, in a 1993 paper of Kondratieff & Fitzgerald, it was noted that S. valida...which had previously been considered the only species in the genus, with a wide geographic range from the eastern US to Arizona...actually consisted of two species: the former S. valida ranging throughout the eastern US west to Colorado; and the new species S. nelsoni with range apparently restricted to the uplands of the Sonoran Desert in southern Arizona. The two species are very similar in appearance, with the distinctions being in details of the genitalia. For more details, see the info pages for S. nelsoni and S. valida.

According to the MND(1), pyrgotid larvae are parasitoids of adult scarabaeid beetles...which adult female pyrgotids oviposit on in flight. The noctural habit of pygotids is presumed to be linked to the nocturnal habits of their scarabaeid hosts. Kondratieff & Fitzgerald state that S. nelsoni may be associated with numerous species of Melolonthinae and Rutelinae. Many Rutelinae were present at the lights where this and my other posts of S. nelsoni were photographed that night...especially Chrysina:

Images of this individual: tag all
Pyrgotid fly from 2013 gathering in AZ - Sphecomyiella nelsoni Pyrgotid fly from 2013 gathering in AZ - Sphecomyiella nelsoni

Do you feel this image should then be moved?

Update to comment below
I wrote to Dr. Kondratieff a while back regarding the question of whether the AZ location indicates S. nelsoni as the most likely ID here, rather than S. valida (as discussed in detail in my "Perhaps so..." comment below). His response was:

    "As you indicated so very well, most likely your images refer to S. nelsoni...but final determination depends on examination of the genitalia."

Returning today to puzzle again over Dr. Fisher's post, I tried zooming in on the full-size version of his image in my browser window, and I "think" I see portions of the terminalia there bearing resemblance to parts depicted in Figs. 1–4 on pg. 555 of Kondratieff & Fitzgerald (perhaps rotated at a little under 90° downward from their orientation in the figures). And, after careful scrutiny, I think those parts (which I believe to be the male's surstyli) do indeed correspond more with Figs. 3 and 4 for S. nelsoni than with Figs. 1 and 2 for S. valida. Hopefully Dr. Konratieff can correct or confirm this...and perhaps settle the issue without any need to invoke range to support a putative ID.

Postscript: I sent Dr. Kondratieff a photo-collage of Dr. Fisher's image...with insets of a zoomed-in view of the terminalia therein, and Figs. 1–4 on pg. 555 of Kondratieff & Fitzgerald. In reference to that photo-collage, and to my remarks above he replied:

"Again, it would be good to actually clip the terminalia, clear in KOH and carefully scrutinize the genitalia for a positive identification, but I do agree with you."

Perhaps so...though it depends on how that ID was arrived at.
John's question under that post addresses the crux of the matter.

If the ID was based on examining terminalia (epandrium/surstyli in male, ovipositor in female) with reference to the details given in Kondratieff & Fitzgerald (1993), then I'd say that post should be left where it is, and mine should be moved from species nelsoni up to the genus node for Sphecomyiella.

But if not (and especially if the ID was made using only Steyskal's 1978 treatment), then I'd think S. nelsoni would be the appropriate (i.e. much more likely) ID...though some purists might argue that all posts ought to be kept at the genus level unless there's a positive ID based on terminalia.

My reasoning is as follows. As mentioned in my remarks under the post, prior to 1993 S. valida had been thought to be the only species in the genus and to be distributed widely from the eastern US (and Ontario) west to Arizona. But after a thorough study examining many specimens from throughout that range, Kondratieff & Fitzgerald determined that all the Arizona material at hand conformed to the characters of their newly described S. nelsoni, while all of their long list of representative specimens of S. valida consisted entirely of records from the eastern and central US, with none occurring west of Colorado...and, in particular, none from Arizona.

Thus, from their work it appeared a reasonable hypothesis that the two species were geographically separable. But of course they hadn't checked every individual from the east coast to Arizona, so couldn't know with absolute certainty whether a specimen with the terminalia of valida might turn up in Arizona...or one with the terminalia of nelsoni might turn up in the east.

So if the terminalia were examined with reference to Kondratieff & Fitzgerald, and determined to correspond clearly with S. valida rather than S. nelsoni, then I'd think that would be a significant observation in relation to the hypothesized geographic separation of the two species implied in the paper of Kondratieff & Fitzgerald. That would have been worthy of comment in the post, and communicating to Dr. Kondratieff.

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