Intranidal Mated Offspring Hibernation (IMOH) in the Ant species Leptothorax gredosi (Hymenoptera: Formicidae: Formicoxenini)

Abstract

In a number of ant species belonging to the Myrmicinae, tribus Formicoxenini, the young females (♀♀) mate within, or in the vicinity of, the maternal nests. They shed wings and spend the winter there. In the monogynous Spanish species Leptothorax (Myrafant) gredosi Espadaler & Collingwood 1982, dealate and mated young ♀♀ were found in the nests in fall. Daughter colonies with one such ♀ each and a few workers could easily be established. Several years of laboratory observations revealed that usually in spring the young mated ♀♀ fight and mutilate each other, and are eventually evicted from the colonies. In the field, the ♀♀ probably leave the nests during this period, perhaps together with a few workers, in order to establish own, monogynous colonies. However, young ♀♀ that have been reared and have mated in orphaned colonies begin to fight already in fall. Presumably they develop their ovaries earlier than under the influence of a queen. Survival chances for single ♀♀ during the winter are probably lower than within the mother colonies. Such temporary Intranidal Mated Offspring Hibernation' (IMOH) should not be confused with long-term functional monogyny, but it may constitute an evolutionary route towards the development of functional monogyny as well as of (facultative) polygyny, and for the evolution of social parasitism.