EXPLOSIVE FOOD RECRUITMENT AS A COMPETITIVE STRATEGY IN THE ANT MYRMICA-SABULETI (HYMENOPTERA, FORMICIDAE)

Myrmica sabuleti forms mature colonies of about one thousand workers a nd a few queens. Although living in dry and sunny biotopes, this speci es avoids foraging during the warmer hours of the day which correspond to the period of the maximum foraging activity of two sympatric speci es, Formica fusca and F. cunicularia. M. sabuleti is the most frequent ly observed species on the extrafloral nectaries of Vicia sativa, even during the warmer hours of the day, whereas F. fusca is the most freq uent species during those hours at tubes of 1 M sucrose solutions plac ed on the ground. In spite of this temporal segregation, the foraging activity of M. sabuleti and F. fusca overlaps two times a day (10:00-1 1:00 am and 5:00-8:00 pm). Newly discovered large food sources are exp loited by M. sabuleti through an explosively increasing recruitment, w hereas workers of F. fusca forage mainly individually. Interference be tween M. sabuleti and F. fusca was studied when offering sucrose solut ions, large dead insects unretrievable by individual foragers of eithe r species (cockroaches), medium-sized insects retrievable by single fo ragers of F. fusca but not by single M. sabuleti (larvae of Calliphora erythrocephala) and small insects (Drosophila) retrievable by individ ual foragers of both species. Owing to its rapid recruitment, M. sabul eti is able to displace F. fusca from sucrose solution and large dead prey during the overlaping of the activity cycles of both species. Whe n medium-sized corpses are offered, the issue depends on the speed of the events. F. fusca is able to take the prey away only if it discover s it before M. sabuleti has recruited nestmates. Small dead prey do no t lead to interference, but is taken by the first worker that finds it .