M. florae added to show venation difference.
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The wing venation proves it to be Eristalis, which sometimes does have a suggestion of the bat shape on the thorax. Basically, the veins above the looped vein meet the margin separately in Myathropa, but joined and with a petiole (like here)in Eristalis.
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Well spotted Ian, thank you...
An iSpot Project- HELP WITH IDS - UK & Ireland Community - PLANTS
Lat/Lng: 53.2055, -0.5631
OS grid ref: SK960685
Backies woods, Boultham Moor, Lincoln.