Earlier this year I enjoyed a short break on the Greek island of Kefalonia. I took quite a few photos of insects, many of which I have still to identify. Needing help I uploaded this image of a wasp to the Hymenopterists Forum on Facebook. Almost immediately Irenel E. Popescu came back suggesting it might belong to the Leucospidae, a small specialised group of ectoparasitoid wasps within the Chalcidoidea superfamily.
Using this as a starting point, and after a further trawl of images on the internet, I concluded that it was most likely the Parasitoid Wasp Leucospis gigas.
This family of wasps is parasitic to a variety of other stinging wasps and bees. The female will use her unusual ovipositor to drill into an already existing nest and lay her eggs. After a few days, these will hatch into voracious larvae that will feed on the ova of the host.
An unusual feature is that the female’s ovipositor is recurved and lies along the dorsal side of the metasoma (the egg laying tube is arched up onto her back) and you can just about see this in the photo. Another diagnostic feature is that the hind femora (thighs) are often greatly enlarged, with a row of teeth-like serrations along the lower margin, as in the related family Chalcididae (Chalcid Wasps).
They are often black with yellow, red or white markings.