These "hosts" are species of "Formica" ants in the groups "F. fusca" and "F. neogagates". A newly mated female of "P. mexicanus" enters the nest of a potential host, employing pheromones to subdue the resident workers. She then kills the existing "Formica" queen and becomes accepted by the "Formica" workers. These then proceed to rear her brood as well as maintaining the nest and feeding the dulotic queen and the ants which develop from the eggs she lays. The dulotic ants are unable to carry out these tasks themselves. The workforce of the colony is periodically replenished by a raid being undertaken on another nearby colony of "Formica" ants. The raid is made by the "Polyergus" worker ants and usually takes place on a hot afternoon in the summer. A scout ant locates a suitable target nest and a column of dulotic ants move towards it. On arriving at the nest they may mill around for a while, perhaps clearing debris such as small stones or twigs away from the entrance. They then surge inside and quickly begin to emerge carrying host pupae, prepupae and sometimes late-stage larvae back to the dulotic nest. There, the host workers care for them as well as the dulotic young developing from eggs laid by the "Polyergus" queen. Newly mated female dulotics may take advantage of raids to enter host colonies during the chaotic situation that exists during a raid.