Communication and orientation during foraging and emigration in the ant Formica fusca

1. Scout ants of Formica fusca lay a hindgut trail from the newly discovered food source to the nest; however, the hindgut material does not have a recruitment effect on nestmates. 2. Inside the nest the recruiting ant performs a waggle motor display and food offerings when facing nestmates head-on. Nestmates are alerted by this behavior and subsequently follow the trail to the food source. 3. Experiments have shown that neither Dufour's gland secretions nor poison gland substance can release trail following behavior. Only ants stimulated by the recruitment performance of the scout ant would follow the hindgut trail. Orientation experiments demonstrated that the hindgut trail serves as an important orientation cue during foraging activities. 4. Also during nest emigrations recruiting ants lay chemical trails with hindgut contents, and again it could be demonstrated that the trails function only as orientation cues. Also in this case the alerting signal consists of a specific motor display. During nest emigrations most of the recruits, however, are carried to the target area by only a relatively small number of so-called "transporting specialists." 5. The recruitment technique employed by Formica fusca, in regard to its organizational level, can be placed between "group recruitment" on the one side and "chemical mass communication" on the other. 6. Although the comparative analysis of the organizational levels of recruitment techniques employed by different formicine species does not necessarily provide direct evidence of the evolutionary pathways of recruitment behavior, it at least allows us to develop a model of the evolutionary steps leading to the highly sophisticated stage of mass communication.