Hyposoter longulus (Thomson, 1887) Anilasta longula Thomson, 1887: lectotype ♀ in MZLU, designated by Fitton (1982), examined by Horstmann. The species is fairly readily identifiable; the central colour of the hind tibia is usually yellowish orange and, even when it is paler, the contrast between the median area and the subbasal and apical rings is less strong than in Hyposoter vividus. The hind tibia coloration is often very similar to that of Hyposoter inquinatus, but the latter has pale fore and mid coxae, and usually a darker hind femur. Shaw et al. (2016) listed rearings in the UK from Orgyia antiqua (Linnaeus) (Lepidoptera, Erebidae), Acronicta psi (Linnaeus) and Cucullia verbasci (Linnaeus) (Lepidoptera, Noctuidae).A further male in NMS was reared in the UK from Lycophotia porphyrea (Denis & Schifferm̧ller) (Lepidoptera, Noctuidae), and a male in NHMUK was also reared from O. antiqua. 2 females in NHMUK were reared from Acronicta psi or A. tridens (Denis & Schifferm̧ller) The lectotype is from Sweden. We have seen specimens from the UK and Germany. It has been variously reported, though with uncertain reliability, in addition from Austria, Finland, and France. Limited phenological data shows specimens taken from May to August, with peaks in June and August.

Published as part of Galsworthy, Anthony, Shaw, Mark R. & Haraldseide, Håkon, 2023, A key to European species of Hyposoter Förster, 1869 (Ichneumonidae: Campopleginae) with descriptions of 18 new species, and notes on all included species, pp. 1-73 in Zootaxa 5290 (1) on page 52, DOI: 10.11646/zootaxa.5290.1.1, http://zenodo.org/record/7959256