Ichneumonidae

 
The Ctenopelmatinaea are a subfamily of Ichneumonidae wasps comprising of 95 genera that are mainly parasites of Symphyta larvae.
 

Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Ichneumonidae
Genus: Diplazon
Species: D. laetatorius
 
 

The ichneumon wasps are solitary insects, and most are parasites - the larvae feeding on or in another insect which finally dies - of the larvae of butterflies and moths, and some ichneumons also parasites of sawfly and beetle larvae.

Identification key to the subfamilies of Ichneumonidae (Hymenoptera) by Gavin Broad of the Dept. of Entomology, The Natural History Museum.
 
This key is a 9MB pdf and a little complicated to use without a specimen.
 

Identifying ichneumonids can be a daunting process, with about 2,400 species in Britain and Ireland. These are currently classified into 32 subfamilies (there are a few more extralimitally). Rather few of these subfamilies are reconisable on the basis of simple morphological character states, rather, they tend to be reconisable on combinations of characters that occur convergently and in different permutations across various groups of ichneumonids.