1. Nothomyrmecia macrops workers forage individually; no recruitment communication or group retrieval of prey has been observed; prey items measure less than 4 mm in length; huntresses grasp live prey with the mandibles and forelegs and sting it to death. 2. Field and laboratory observations confirm that workers from neighboring nests can forage on a single tree without antagonism. Alien conspecifics might be attacked, however, if attempting to enter foreign nests. 3. Field and laboratory observations suggest that chemical trails do not play an important role during homing by foragers, indeed they might not be produced. Although strictly nocturnal,Nothomyrmecia seems to navigate primarily by visual cues, possibly using the canopy silhouette overhead. However, chemical markers might be important in localization and recognition of nest entrances. 4. No antagonistic behavior has been observed between foragers from different colonies, yet in a laboratory test nestmates appear to show a greater tendency to cluster than non-nestmates. Worker interchange between neighboring laboratory nests was observed and experiments suggest that it is facilitated by loss of the queen in one colony. These results explain in part the findings ofWard andTaylor (1981) thatNothomyrmecia nestmates are not always full sibs. 5. All records to date indicate that matureNothomyrmecia colonies are monogynous, but can be founded by pleometrosis (Taylor, 1978). In an experimentally assembled group of 15 workers with 2 queens (neither of which was the mother of any of the workers) one queen exhibited dominance behavior towards the other. The subordinate was finally expelled by the workers. 6. Nothomyrmecia employs chemical alarm communication when other ant species attempt to enter its nests. The mandibular gland secretion is an effective close-range alarm pheromone. Dufour's gland secretions also elicit attraction, but the ants react more slowly. Secretions from the pygidial gland appear to function as an alarm-repellent substance.