Harpagoxenus sublaevis has a remarkable life history. Unlike other ant species, in which the worker ants (wingless females) undertake tasks such as searching for food and defending the nest, Harpagoxenus sublaevis ants enslave Leptothorax ants to do this work instead (8) (9) (10).
This begins when a wingless virgin queen climbs a vertical structure in the vicinity of the nest and releases a sexual pheromone which attracts males and stimulates them to mate (10). Once mated, the queen searches for a Leptothorax nest within walking distance to invade (6).
The queen attacks the Leptothorax colony by using her mandibles like secateurs to dismember defending workers, and also deploys what could be described as a ‘chemical weapon’; the queen secretes a sticky substance which, when smeared on Leptothorax workers, causes the defending workers to attack each other. The substance somehow results in the contaminated worker, and not the slave-maker queen, being perceived as the enemy. As the substance is sticky, it quickly spreads from worker to worker, enabling the queen to slip past the growing chaos to begin her final assault on the Leptothorax queen (9). Once all adult Leptothorax ants have been killed or driven away, the Harpagoxenus sublaevis queen remains with the Leptothorax brood. When the brood hatches, these new workers accept the Harpagoxenus sublaevis queen as their own, and start undertaking all routine tasks such as foraging, nest building and caring for the queen’s new brood. The Harpagoxenus sublaevis workers that hatch from this brood specialise in raiding new nests to refresh the ‘slave’ worker force (6) (11).
A Harpagoxenus sublaevis ‘scout’ locates a Leptothorax nest and then returns to its own nest to recruit a nest mate by releasing special pheromones from its abdomen. The recruited member will then follow the scout back to the host species nest. Once there, either the scout or the newly recruited ant will again return to its own nest and recruit another worker. This occurs until a sufficient number of workers have assembled to lay siege to the host colony (8).
In a similar manner to how the queen invaded a Leptothorax colony, the Harpagoxenus workers use their mandibles to clip the legs and antennae of the host defenders, and secrete a substance that provokes internal battles among the Leptothorax workers (9). Once the siege is over, the host eggs and larvae are eaten and the pupae are removed and returned to the Harpagoxenus sublaevis colony (8). The Leptothorax workers that emerge from this stolen brood then undertake foraging, nest-building, and caring for the brood for Harpagoxenus sublaevis (8) (11). Harpagoxenus sublaevis undertakes any reproductive activity and slave raids during the summer (10).
Unlike many other ant species, Harpagoxenus sublaevis workers are capable of producing viable sons from unfertilised eggs. However, the queen, who would prefer workers to be exclusively putting energy into her young, uses chemical secretions to inhibit the workers’ reproduction. Harpagoxenus sublaevis workers probably only reproduce after the death of the queen (9).