Foraging strategies and recruitment behaviour in the European harvester ant Messor rufitarsis (F.)

Most of the approximately 40 species of the Old World harvester ant genus Messor live in warm and dry Mediterranean areas. One species, M. rufitarsis, is found in isolated Northern temperate habitats in Rheinhessen and the Rheingau area in Hessen, West Germany. These habitats are characterized by a great diversity of spermatophytes, so that permanently changing seed resources are available for the ants during the growing period. M. rufitarsis has maintained its granivorous specialization under these habitat conditions and collects most of the seed resources, which show a large fluctuation in quantity, quality and distributional pattern throughout the year. M. rufitarsis is very flexible in using different foraging strategies. For discovering newly ripened food resources and collecting wide-spread single seeds, an individual foraging strategy is used. However, dense seed resources are exploited through an effective recruitment system. Nestmates are guided to the feeding place by means of orientation-recruitment trails from Dufour's gland. Additional invitation behaviour enhances the success of recruitment. From analysis of slow-motion movies it is concluded that stridulation is the crucial signal of the invitation behaviour.