The sparkles of incident sunlight reflected by the armour of this small and fast female Omalus biaccinctus [1] (det. Milo van Loon) made it easy to detect on the Salvia plants on which she was hunting. A new garden species!
This rare wasp has several species from the genus Passaloecus as host, among which the garden resident P. gracillis [2]. She does not parasitise the wasp larvae but the aphids that are collected by their host for their offspring [2].
References
1 Nederlands Soortenregister2 PAUKKUNEN, Juho, et al. An illustrated key to the cuckoo wasps (Hymenoptera, Chrysididae) of the Nordic and Baltic countries, with description of a new species. ZooKeys, 2015, 548: 1.