The excellent feature on the beewolf (Sniffing out the Beewolf, November 2017), and the author’s observation that the female wasp extracts recently imbibed nectar from the captured honeybees, reminded me of something last summer.
I saw a field digger wasp stalking some greenbottles along various ivy-rich hedges. Following the struggle there was often a lull, during which the wasp would re-jig its grip and take the fly’s labellum in its jaws ( above).
Could the wasp be drawing nectar from the fly? Steve Smailes, via email
Entomologist Richard Jones replies: I doubt the wasp is extracting partdigested nourishment through the fly’s tongue, as greenbottles rarely visit flowers and take only a little nectar when they do. However, it may be ‘testing’ its prey as to subduedness and tastiness.