Megastigmus stigmatizans Fabricius 1798

A parasitoid of the following gall causers; A. kollari agamic, A. quercuscalicis agamic.

The female wasp measures 5.9-6.8mm which averages out at 6.3mm excluding the ovipositor.
The head is a rich yellow colour with a sharply defined metallic red/green patch on the vertex. The eyes are large and bright red, contrasting vivdly with the rest of the head, the ocelli are dark baige. The antennae are dark, short and heavy with one ring and 7 funicular segments with longitudinal hairs on each segment.
The thorax has varying amounts of well defined metallic red shot green on the top and sides contrasting with yellow with traces of brown beneath. The notaulices are deep and full length and there are some hairs present. The tegulae are colourless testaceous which lead on to the wings which are clear. The stigma is shaped like a dark capsule, twice as long as it is broad, with a cloud surrounding it that may vary in size considerably. The legs are all yellow with metallic hairy coxae. 5 tarsel segments are present and dark claws.
The gaster (abdomen) deeply triangular and is a mainly a dull mid yellow with touches of dark brown above. The ovipositor sheaths are long, hairy and dark and is in length at least as long as the body length, with an average of 113% of the body length.

The male measures in at 4.5-6.3mm with an average of 5.2mm
The head is yellow with a distinct dark green patch on the vertex. The eyes are a conspicuous brown contrasting with the other colour of the head and the ocelli are dark beige in colour. The antennae are dark, short and heavy with one ring and 7 funicular segments with longitudinal hairs on each segment.
The thorax varies considerably with many specimens having metallic green all over to others that have, more or less, yellow on the sides and underneath. They all are hairy and the notaulices are deep and full length. The wings which are clear have a stigma that is shaped like a dark capsule, twice as long as it is broad, with a cloud surrounding it that may vary in size considerably, like in the female. The legs are pale yellow and hairy with dark marks on the rear femora and dark rear coxae. There are 5 tarsel segments and dark claws.
The small gaster square from the side but triangular from above. It is dark chocolate in colour with pale underneath with no yellow band or bar at the tip.

The flight times for this wasp are february and then again in june and july.

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

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