Possibly a species complex. Forewing with large, obvious pterostigma. Gastral collar broad and very short, entire breadth of gaster covered anteriorly by strigose sculpture radiating from gastral collar. Antennal Scape usually mostly black but sometimes entirely yellow. 

Unless identified by a recognised expert, a photo is required and the specimen should be examined with a microscope. In the comments box, state the key or ID method used and describe the size and identifying characters.

Hyperparasite parasite of aphids.

Unknown.

Unknown.

Fergusson, N.D.M. (1980) A revision of the British species of Dendrocerus Ratzeburg (Hymenoptera: Ceraphronoidea) with a review of their biology as aphid hyperparasites. Bulletin of The British Museum (Natural History) Entomology, 41, (4), 255-314.