Excursion Bennekom, March 2024.
We found two dead workers and a dead queen inside a piece of branch that was sticking out of a Formica rufa hill. They are all under 3 mm lenght.
piceus or maybe atricolor (see shape of the clypeus)
sorry for the bad photo, made years ago
sorry for the bad photos, made years ago
Myrmecina graminicola maybe?