Stabbing on Maulden Heath

There were three of these 6cm long wasps, which I presume to be some type of Ichneumon, working over a pile of conifer logs on Maulden Heath on Sunday afternoon (4th Nov 07). Once a larva was detected within the timber they would raise their abdomen, unsheath the ovipositor (occuring in this picture) and push it into the victim. Two were contending over one location so there clearly must have been something beneath the surface there, obvious to them with their antennae, but not to me with my eyes.

Picture by Keith Balmer