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Geron species possibly G. aridus on Catclaw - Geron - male - female

Geron species possibly G. aridus on Catclaw - Geron - Male Female
Anza-Borrego Desert State Park, San Diego County, California, USA
October 9, 2003
Size: 7-8 mm
Geron aridus possibly? I posted this comment on # 229679, taken in 05/-6/2008. Maybe this photo shows the antennal detail better?

I've been studying this bug and think it may possibly be G. aridus. the 2nd submarginal cell is about twice as long as wide, which puts it into subgenus Empidigeron. In Painter's 1932 revision of Geron, the subgenus only has about6 species.
Traits leading to G. aridus in the key are: First joint of antennae about twice as long as second, and pile on antennae white. Both are true for our bee fly.
This key leads to two possibilities, G. calvus which is mainly a northeastern species (though Cole writes it has been reported from CA) and C. aridus, described from southern AZ. The key separating them, the degree of yellow on the abdominal venter, I could not determine, but based on distribution, G. aridus would be the best bet.

Am I on the right track?

Moved from Geron.

I believe this is subgenus Geron, rather than Empidigeron. The two can be separated based on the relative position of the R4-R5 junction - in Empidigeron it is halfway between the wing edge and crossvein r-m, while in Geron it is closer to the wing edge. This appears to be closer to the wing edge. This fly shows the venation of Empidigeron.

Hall and Evenhuis (2003, Zootaxa 181) revised the Nearctic members of the subgenus Geron. I don't have the paper in front of me, but I believe they found that most species were only reliably identified by examining the internal female genitalia.

Thanks for your comments. They are very useful for trying to distinguish the various genera and subgenera in this large family of desert insects. I especially appreciate your link to the real Geron subgenus Empidigeron. I've added it to my the bee fly wing collection. I have the 2003 article by Hall and Evenhuis on Geron subgenus Meigen, but did not even consider running my photo through the key with so many species. Thanks again.

Nice Shot!
It's funny how this most drab of Bombyliid genera turns out to be one of the most photogenic. It must have to do with its light color. As for IDing this, Jack Hall of UCR was working on the genus back in the late 80's, but was having difficulty. He grumbled to me, "I'd like to take all the types and step on 'em!"

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