Torymus chloromerus

A member of the family Torymidae, this wasp is parasitoid of cynipid wasps.

The gall hosts of this species is; Macrodiplosis pustularis (=dryobia), which is a small non biting midge and member of the order Diptera. Although a lot is known about the gall and the larva, not alot is known about the adult. The larvae is the causer of a gall on Oak leaves which is evident by a tight folding of the leaf lobe at the tip of a vein. It is green at first then turns brown and is evident from june to september. The gall contains a white larva. The flight times for Torymus chloromerus are from may to july and the again in september.

The female wasp measures in at 2.5-2.9mm, excluding ovipositor, with an average of 2.7mm.
The head is a metallic green with some blue tints, and coriaceous. The eyes are moderatly large and red with large red ocelli. The antennae are dark brassy coloured with prominent pale sensillae and a yellow scape and metallic pedicel. There is one ring and 7 funicular segments, with a distinctive club.
The bright metallic green and blue thorax has plenty of short pale hairs. The notaulices are full length. The tegulae are testaceous leading to the wings which are clear and have pale hairs and pale yellow veins, with a short stigmal vein and a long post marginal vein. The legs have bright metallic green coxae and femora, with brown tibia. The ends of each leg section and the joints are yellow and the tarsel segments, of which there are 5, are brown.
The gaster (abdomen) is a bright metallic green with blue. The underneath fades to a translucent testaceous colour. It is glossy with some sculpture in parts. The ovipositor sheaths are mid length (about 80% length of head and body), mid brown and hairy with short hairs.

The male is 1.5-2.6mm averaging at 2.2mm in length.
The coriaceous head is bright metallic green with strong white hairs. The eyes are moderatly large and red with large deep red ocelli. The antennae are brassy with a bright metallic scape and brown pedicel and prominent pale sensillae. There is one ring and 7 funicular segments leading to a distinctive club.
The thorax is a metallic green with occasional blue tints and sparse white hairs. Full length notaulices and the tegulae are dark and pale brown. The wings are clear, with unobtrusive hairs and pale yellow veins. It has a short stigma and a long post marginal vein. The legs have bright metallic green coxae and femora, with brown tibia. The ends of each leg section and the joints are yellow and the tarsel segments, of which there are 5, are brown.
The gaster is variable in colour from all bright metallic green with some blue tints through to a mix with mid brown. It is narrow, deep and, of a compact shape.

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

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