Gasterupteron jaculator Female
This is one of the largest parasitic wasps, about 40mm long, including the ovipositor.
I saw two or three of these visiting, and landing on, the flat cut surface of a Weeping Willow log, from a tree felled several years ago. Their presence, together with “sawdust” on the ground at the base, told me their hosts were nesting in the wood.
For several years, I have been aware of the presence of burrowing bees/wasps in dead trees in our garden but have never seen one clearly, let alone photographed one. That was about to change. (More images are to follow in further topics).
Olympus EM-1 (aperture priority), Olympus 4/3 x2 TC, Olympus 4/3 50mm f2 macro, 1/80 at f10 ISO 2,000, bright overcast, hand-held.
The stereo is crosseye.