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small-headed fly - Pterodontia westwoodi - male

small-headed fly - Pterodontia westwoodi - Male
4 miles east of Ithaca, Tompkins County, New York, USA
June 26, 2013
Size: 5mm
Fuzzy view of one antenna.

Images of this individual: tag all
small-headed fly - Pterodontia westwoodi - male small-headed fly - Pterodontia westwoodi - male small-headed fly - Pterodontia westwoodi - male small-headed fly - Pterodontia westwoodi - male small-headed fly - Pterodontia westwoodi - male small-headed fly - Pterodontia westwoodi - male

Hi Joyce
Just wanted to let you know that I used a crop of the antennae here in a composite post to flesh out details for a post of a female of P. westwoodi, see thumb below:

It turns out this species is sexually dimorphic with respect to color pattern on distal abdominal tergites. (And also with respect to density and color of hair...or so it appears.)

These guys (and gals) are rare and interesting...hope you get to see and document more in the future :-)

Also that's a nice info page on Pterodontia that you put up.

Yes I have photos of one from Mt Diablo that I need to post... too darn much going on all the time to have time to post. :( At least I got outdoors a lot in July.


Yes, too darn much to do
...and we should probably go check if there may be a current crop of those Epilobium galls in Del Puerto sometime too :-)

I look forward to your Pterodontia post (I'm impressed you recognized it to genus :-) With luck, you may have gotten an image showing the shape of the flagellomere, like your shot above...though the antennae are usually too inconspicuous to see in most images, and/or are hidden from view .

Hope you're doing well :-)

Note the unusual antennal position & form in this genus
This image illustrates well the unusual form and placement of the antennae in members of the genus Pterodontia.

The antennae in Pterodontia are inserted low on the head, at the top of the "face". But the face here is extremely reduced in size, and is squeezed into a small area at the bottom of the head, beneath where the long contiguous forward edges of the eyes separate. The antennae consist of a stacked pair of short, somewhat flattened disks (the scape and pedicel) followed by an apically swollen flagellum with a few bristle-like hairs splayed forward at its tip.

So, in case it's not clear...the thin, tear-drop shaped blob near the bottom of the head, with 4 straight hairs splayed downwards is the terminal segment (or flagellum) of the left antenna here. Looking closely, I think I can make out the downward splayed hairs of the right antenna as well (and maybe even the pedicel and/or scape).

Moved from Pterodontia.

Fuzzy by your exceptionally high standards...
...but perfect in regards to what I was hoping for!!

Revisiting the 1st couplet of the Pterodontia key on pg. 390 of Sabrosky (1948), I measured the length-to-width ratio for the terminal antennal segment (which is so nicely and clearly visible in your terribly "fuzzy" image! :-)

Eureka! The ratio is indeed about 5:1, and far from the "nearly equal" (i.e. 1:1 ratio) for the opposing choice in the 1st couplet. And, as expected, it's also a clear match with the appropriate Fig. 20a in Cole (1919) (rather than Figs. 21a and 22a for the opposing choice).

So I'd say this photo clinches the ID here.

Moreover, your other additional (6th) photo of the wing venation, in conjunction with a careful reading of couplet 3 of Sabrosky's key, gives an extra test of the putative ID...which it passes with flying colors.

So...unless I've overlooked a later reference, or there's been an unpublished "folklore-type" development with this taxon (i.e. one of those sinister discussions in smoke-filled backrooms leading to informal agreements among oficionados on how certain taxa should be lumped or split into something new)...then this has got to be Pterodontia westwoodi.

Congratulations on another great find, Joyce. It's not only a first for BugGuide, but Sabrosky describes it as an interesting and rarely collected species, of which he was able to access only one specimen: a male from Seacliff, Long Island, NY.

And...beyond the ever-abundant, robotically generated, and annoying content-free, template-type taxonomy web pages that are constantly proliferating on the web...a Google Search on "Pterodontia westwoodi" seemed to yield no images or references of interest.........that is,except for this very nice item.......from someone associated with an outfit calling itself the Cornell University Insect Collection. Is that anywhere near where your photos were taken? :-)

Funny that one of the few other specimens collected was found in Ithaca. Really great to have an ID on this, especially since it's turned out not to be very common. Thanks for all the sleuthing on this one Aaron.

Your welcome, Joyce.
I thoroughly enjoy the sleuthing, and the learning that goes with it. Besides, I'm happy to do it because, as you should already know, you're one of my heros :-)

PS: I encourage you to follow the advice at the end of the Cornell writer's post...and spend more of your Sunday's looking for acrocerids, and less on household chores.

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