Theoretical analysis of the communication system for chemical mass recruitment in ants

Abstract

Different possible communication systems for chemical mass recruitment in ants are investigated and the results from computer models simulating recruitment are compared with experimental observations reported in the literature. The communication system more likely to be used by ants in chemical mass recruitment is one in which the pheromone concentration on the trail is maintained constant by scout ants and is related to the quality of the food. Equilibration of recruitment is achieved by the ants by reacting to increasing ant densities on the food source, and on the trail, with decreasing recruitment efforts. The general conclusions that can be drawn from this theoretical analysis are the following: o (a) The participation of an important proportion of scout ants in therecruitment process is essential. The optimum proportion depends mainly on the distance to the food. The net result is a high percentage of ants on the trail returning to the nest without carrying any food. (b) Orientational cues different from the trail pheromone increase the recruitment efficiency. (c) Attraction to the trail and orientation along the trail to the foodsource need to be maintained as separate events. This can be achieved if there are two different behavioural thresholds towards the same pheromone ( Atta for example) or if there are different pheromones for each purpose ( Myrmica for example). (d) A decrease in recruitment effort at increasing ant densities on thetrail produces more efficient recruitment. (e) Complete depletion of food sources at long distances from the nest are unlikely. As the food available decreases, the probability that the colony will be unable to exploit it increases.