Tersilochinae

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This subfamily includes around 80 mostly small and inconspicuous, somewhat braconid-like species comprising the traditional Tersilochinae and, in part, the former subfamily Phrudinae (genera Astrenis, Phrudus and Pygmaeolus). They have not been separated into tribes, but are usually treated as two distinct groups: the original Tersilochus group, and the Phrudus group, in which there are only eight species. The latter includes some of the smallest British ichneumonids.

Although identification to species and, in most cases, even the genus is extremely unlikely if not impossible from photos, individuals, notably of the Tersilochus group, can generally be recognised as belonging to the subfamily by their forewing venation, without an areola, but with a large, roughly triangular-shaped, pterostigma, coupled with a thickened 2rs-m vein and an angle of 90 degrees or less between the first and second sections of the radius. There are additional features, such as a comparatively large antennal pedicel and a fringe of strong setae on the clypeus, but realistically these require close examination.

The primary genera are Barycnemis (11), Diaparsis (8), Phradis (10), Probles (16) and Tersilochus (20), some of which are further split into various subgenera. The most frequently recorded species in this group are, in order, Phradis interstitalis, Barycnemis harpura, Phradis minutus, Tersilochus cognatus and Tersilochus obscurator. That said, records are very few are far between.

From general appearance and wing venation, the first individual featured below has tentatively been identified as Barycnemis sp. and, if that assessment is correct, Barycnemis harpura would be the most likely species. The second specimen has 16 flagellar segments, which eliminates a number of possible species, but on good advice I'm advised that the genus can't be confirmed without examination of the tip of the ovipositor, so although it can be assigned to the Tersilochus group, it has to be labelled as undetermined.

The majority of species develop as koinobiont endoparasitoids of various Coleoptera larvae. The actual procedure in terms of egg placement varies from one species and host to another, but generally the females start egg laying just a few days after mating, which itself takes place very soon after they've emerged.

Updated, June 26 (v.3)