The slave-making ant Harpagoxenus canadensis and its host species (Leptothorax species A and L. canadensis) nest in beetle galleries in small pieces of rotting pine wood that are lying on the ground.
Above, the Harpagoxenus queen is the large ant just right of centre. The ant just left of centre at the bottom is a Harpagoxenus worker. At the top left is a second Harpagoxenus worker as it looks when seen from below. We can see its underside because it is walking on the inside of the transparent lid of the artificial nest. The other four four ants are Leptothorax canadensis slaves. Two slave-species worker pupae are at centre bottom. The whitish "blobs" with dark centres are large larvae.
Slave raids begin when Harpagoxenus workers leave the nest to scout for a host-species target colony. Here a returned scout is surrounded by several other large-headed slave-makers and smaller-headed L. canadensis slaves. By examining the scout, the other ants can tell what kind of ants the scout has encountered.
During slave raids, the Harpagoxenus workers and their slaves attack and dismember target-colony workers wherever they encounter them. Here a Harpagoxenus worker examines a winged queen from the target nest while a slave attacks her. A second slave stands by at the left with open mandibles. At the top, two slaves and two target-colony workers are engaged in a four-way fight. At centre right is a leg which the Harpagoxenus worker has bitten off the queen.
Harpagoxenus workers and their slaves recruit one another to the scene of fighting by the slow process of tandem running, in which one ant leads a single follower. Target-colony workers recruit nestmates in the same way. Here one target-colony worker leads another into battle.
Harpagoxenus workers use their large mandibles to dismember the adult inhabitants of target nests. In the left panel, a Harpagoxenus is about to bite a target-colony worker, near where a second target-colony worker has already been seriously injured. In the centre panel is a decapitated target-colony winged queen. At right is another partially dismembered target-colony worker.
Here a Harpagoxenus worker enters the target nest with mandibles gaping. Note the decapitated head of a target colony worker attached to the slave-maker's right front leg. This disembodied head remained on the slave-maker's leg for two days after the raid.
After the target-nest's defences have been breached, the slave-makers and their slaves carry target-nest worker pupae back to the slave-maker nest, where they are reared to produce additional slaves.
Alternatively, the slave-maker colony sometimes abandons its old nest and moves into the nest previously occupied by a vanquished target colony. Here an L. canadensis slave carries a Harpagoxenus to her new home.