Seasonal polydomy: Its possible causes and its consequences for kinship and intra-specific parasitism in Leptothorax tuberum (Hymenoptera : Formicidae)

The relationship between nest queen frequency, worker number and month of s ampling, in the ant Leptothorax tuberum where both queen frequency and work er number reach a maximum during December and January and a minimum during the summer, supports the thesis of seasonal polydomy, where nests coalesce in the winter and fragment in the summer. Coalescence was found to occur ra ndomly, between nests, in the laboratory whereas in the field coalescence s eems to occur genealogically. Coalescence in the laboratory appeared to be facilitated the closer to the winter solstice the nests were sampled in the field and more so when one or both nests tested did not have a queen. From these observations we provisionally conclude that a proximate cause of coa lescence is day length. We also report a possible role for thermoregulation as the ultimate cause of seasonal polydomy and cooperative behavior in thi s species with seasonal temperature variation as an additional proximate ca use of this condition. Furthermore the seasonal coalescing and fragmenting of nests may explain a phenomenon, previously recorded in this species, at present uniquely in ants, of a form of intra specific parasitism known as e gg dumping.