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Syrphid Fly - Ferdinandea - female

Syrphid Fly - Ferdinandea - Female
Lake Elizabeth, Fremont, Alameda County, California, USA
May 21, 2009
I have a series of photos showing several minutes of this fly backing into a sappy crevice and then wiggling her rear as she came out. Then repeating. Probably laying eggs.

See remarks on:

"The larvae are found in tree wounds...
...and have been recorded in Aesculus, Acer, Populus, etc. The adults are occasionally taken on "bleeding" trees or on other tree trunks. Sack (1932) reported the larvae in ants' nests, but gave no particulars."

That quote is from Cole(1), and supports your hypothesis that your syrphid here was laying eggs. Neat find.

The possible connection to ant nests is also intriguing...may want o keep your eyes open for that in the future.

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