Studies on Formica lugubris Zetterstedt in Ireland (Hymenoptera, Formicidae)

This thesis is based on studies of Formica lugubris from 1972-1975. While this species' range is diminishing in Ireland, the nests are quite common in the State plantations of South Tipperary. It is not certain that the species is indigenous. Above-ground activity occurs from late-February to the end of October; foraging begins in April. Two territorial "spring-battles" between neighbouring nests are described. Most active nests produced alatae of both sexes and flights were observed on successive June mornings above l7.5°C air temperature. Both polygyny and polycaly seem to be rare. Where the nests occur commonly, the recorded densities are similar to those reported from the continent. Most nests persisted at the same site since 1973. The nest-sites are described by recording an array of nest, soil, tree, vegetation and location variables at each site. Pinus sylvestris is the most important overhead tree. Nests seem to be the same age as their surrounding plantation and reach a maximum of c. 30 years. Nearest-neighbour analysis suggests the sites are overdispersed. Forager route-fidelity was studied and long-term absence from the route, anaesthetization and "removal" of an aphid tree had little effect on this fidelity. There were no identifiable groups of workers specifically honeydew or prey-carriers. Size-duty relationships of workers participating in adult transport are described. Foraging rhythms were studied on representative days: the numbers foraging were linearly related to temperature. Route-traffic passed randomly and an average foraging trip lasted c. four hours. Annual food intake to a nest with 25 000 foragers was estimated at approximately 75 kg honeydew and 2 million prey-items. Forager-numbers and colony-size were estimated using the capture-mark - recapture method: paint marking was used for the forager estimate and an interval radiophosphorus mark, detected by autoradiography, was used for the colony-size estimate. The aphids attended by lugubris and the nest myrmecophiles are recorded.