Therion is a genus of ichneumon wasps in the family Ichneumonidae. There are at least 20 described species. These are related to bees and wasps – Hymenoptera.
ID is imprecise but “possibly” Therion circumflexum. The adult parasitoid wasps of this species fly from mid-June to September. They parasitize various butterfly species. These butterflies include the small engrailed (Ectropis crepuscularia), the privet hawk moth (Sphinx ligustri), the pine hawk-moth (Sphinx pinastri), and a number of moths (Noctuidae). The female wasp lays its eggs in the caterpillars. The hatched larvae feed on the caterpillar and pupates later in a thin web.