I didn’t notice at the time I’d published this post, that these bugs have a black head, which means they are a different species than the Cinnamon bug that I assumed they were and which have a red spot on their heads.
These are Firebugs (Pyrrhocoris apterus). A new garden species!
This year there was a true explosion of these red-black bugs in the garden but now I’m not sure which species it was. Apparently Firebugs can often be found near Mallow and Lime trees . The spot where I saw most of them was indeed within a radius of three meters of both plants.
Here a nymph and an adult feast on a dead Honey bee (Apis melifera).
References1 Nederlands Soortenregister
2 Aukema, B., Th. Heijerman & V.J. Kalkman 2016. Veldgids wantsen deel 1. – EIS Kennis centrum Insecten, Leiden.