Eupelmus vesicularis

Previous synonym of this wasp was Macroneura vesicularis. It is a member of the family Eupelmidae and primarily parasitises the Cynipidae gall wasp Andricus quercuscalicis on Oak. It has also been reported to be found in Diastrophus rubi galls on Rubus spp., Myopites olivieri (Dipt., Tephritidae) on Dittrichia and Mikiola fagi (Dipt., Cecidomyiidae) on Fagus. Specimens have also been reared from galls of Rhopalomyia (Dipt., Cecidomyiidae) on Artemisia, Liposthenus kerneri on Nepeta latifolia, Phanacis caulicola on Picris echioides Phanacis centaureae on Centaurea nigra and on C. scabiosa, Timaspis phoenixopodos on Lactuca viminea and Diplolepis rosae on Rosa canina, which was first thought doubtfull, however one was reared from D. spinosissimae, which may make this more likely.

The female measures about 2.8mm in length excluding ovipositor
The head is very dark bronze and metallic green, lightly alutaceous. The mid sized eyes are red and the ocelli are pale red and inconspicuous. The antennae dark brassy in colour and strongly tapered, with one ring and 7 funicular segments. The scape is fat and yellow and the pedicle is metallic green, tiny and slender.
The thorax again is metallic green and has no notaulices nor a median line. This wasp is wingless, or rather the wings are much reduced (Brachypterous) and the apex of the rudimentary forewing is rounded. The legs have metallic coxae, dirty yellow trochanters, with dark brown femora with a yellow tip. The tibia are yellow with a brown infusion towards the tip. The 5 tarsi segments are yellow with a dark tip and a row of black pegs.
The plump gaster (abdomen) is dark neutral brown with a short testaceous base, segmented with the segments having bronze edges. It is alutaceous and punctate. The ovipositor sheaths are tiny with a dark base and tip and thicken in the centre which has a yellow band.

The male measures about 1.6mm in length
The head is a metallic dirty olive green with some purple lights. It is coriaceous and has short hairs. The mid sized eyes are red-brown in colour and the ocelli also are red-brown. The antennae are black with a scape that is faintly narrowly yellow below. There is one ring and 7 comparatively long and untapered funicular segments, segments 1 to 3 have a bump below and set with a group of specialised sensillae which are difficult to spot.
The thorax is a dirty metallic olive green with some bright green tints in parts. The notaulices are full length but there is no median line. The mesepimeron is glossy above and strigose-coriaceous below. The tegulae are neutral brown and lead to the wings which are clear. The long marginal vein is several times the length of the post marginal and stigmal veins which are both the same length. The legs have metallic purple coxae, and the femora are dark with a yellow base. The front tibia is generally a dirty yellow, where as, the middle and hind tibia have a yellow base with well defined dark ends. The tarsi consist of 5 segments.
The gaster is a very dark metallic bronzy-green with a shallow coriaceous sculpture and hairs around the edge. It is wide, shallow and segmented with stepped edges.

More detailed descriptions and identification keys are available from Robin Williams at the British Plant Gall Society.

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