In June 2017 I stopped at Iping Common, West Sussex with the intention of photographing Silver-studded Blue butterflies (Plebejus argus). But I also payed a visit to a colony of the slave-making ant Formica sanguinea which live in a small Aculeate-friendly sand quarry at the edge of the common.
As I tried to photograph the sanguinea workers returning to their nest I noticed that some were being attacked by Lasius platythorax workers which had a nest entrance close to a trail used by the F. sanguinea. As a sanguinea came close to the nest she was attacked by 10-12 platythorax workers which swarmed over her, grasping her legs and antennae and quickly disabling the much larger ant as she struggled to get away.
Most of the sanguinea passed by far enough away to be unaffected, or to only be attacked by a few of the platythorax and escape, but those that passed over, or very close to the nest entrance were being killed. The sanguinea workers seemed unable to offer much resistance once under attack, or to be aware of the danger beforehand, Formica sanguinea workers on the trail that came across a dead nest mate were collecting the bodies and carrying them towards the nest.
This seemed to be a continuous process, with F. sanguinea workers that came too close to the Lasius platythorax nest being attacked and killed then taken away by their nest mates. I was surprised how little resistance the sanguinea seemed to offer, and that no alarm or avoidance behaviour was in evidence.