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].
Literature
1 Nederlands Soortenregister2 Paukkunen, J., Berg, A., Soon, V., Ødegaard, F., & Rosa, P., 2015. An illustrated key to the cuckoo wasps (Hymenoptera, Chrysididae) of the Nordic and Baltic countries, with description of a new species. ZooKeys, (548), 1.