These wasps can be very challenging to identify, and may need microscopic and expert scrutiny to define the species.
The female is often seen investigating logs for beetle larvae. Once detected, she will bore down into the wood and into the larva and deposit an egg, the resulting wasp larva will then feed on the beetle grub.
Class Insecta (Insects)
Order Hymenoptera (Ants, Bees, Wasps & Sawflies)
Family Ichneumonidae (Ichneumon Wasps)
Genus Dolichomitus Smith, 1877
Photos: Baggeridge Country Park, South Staffordshire 15th October 2011. © Peter Hillman
Note: This is a black female wasp with orange legs and a very long ovipositor which she has released from the protective sheath and is using to probe a rotting tree stump.