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Microchrysa flaviventris? - Microchrysa flaviventris - female

Microchrysa flaviventris? - Microchrysa flaviventris - Female
Decatur, DeKalb County, Georgia, USA
April 14, 2020
Size: 3-4 mm
Observed on cool night (53 deg F) on outside of compost bin. At 3-4 mm it is small for M. polita, also the forelegs and antennae are nearly all yellow instead of mostly black. It is therefore likely M. flavicornis or M. flaviventris, which are difficult to distinguish in the females (can tell this is a female because the eyes are separated). According to Woodley "the middle femur in M. flaviventris is wholly yellow, while it is marked with black to nearly wholly black in M. flavicornis and M. polita." My interpretation of the side-view photo is that the middle femur is wholly yellow, so I am leaning towards M. flaviventris. There is also a difference in wing venation related to the closure of the discal cell; it is less conclusive from my photos here, but having looked at pictures of m. Flavicornis wings, they really have a strong outline of this cell that is missing here.

Images of this individual: tag all
Microchrysa flaviventris? - Microchrysa flaviventris - female Microchrysa flaviventris? - Microchrysa flaviventris - female


Moved from Microchrysa.

middle femur in Microchrysa ID
Thanks for taking a look at this observation Dr. Hauser! I wonder what you think about using the color of the middle femur for distinguishing female M. flavicornis and M. flaviventris, as suggested in passing in the article by Woodley? I ask because the only male Microchrysa that I've seen in the location where I made this observation have been two male M. flaviventris (one here ) , and this female and the other one that I've seen had the all-yellow middle femur. Looking at the relatively few photos I could find of females where the discal cell closure feature was unambiguous, the femur color did track with only M. flaviventris all having all-yellow middle femurs (femora?).

You are making a good point h
You are making a good point here... I am used to ID these flies under the scope, so the discal cell character is something I look for because the leg coloration can show more variation - or maybe I have not paid enough attention to this... This genus is very difficult, and here in the US we just have 3 imported species, so it is a bit easier, but the biggest problem are the females of flaviventris and flavicornis, and I agree with you (especially finding males at the same location), this might be flaviventris!

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