We go together! – Groups of European fire ants, Myrmica rubra, distinguish between pheromone blends, and follow pheromone trails for longer distances than individual ants

European fire ants (EFAs), Myrmica rubra, have become major pests in their invaded North American range. They sting aggressively, rendering infested gardens and parks unusable for recreational activities. According to prior studies, foraging EFAs that have discovered a food source return to their nest depositing a trail pheromone (3-ethyl-2,5-dimethylpyrazine) from their venom gland that leads nest mates to the food source. As shown in bioassays with groups of ants, synthetic 3-ethyl-2,5-dimethylpyrazine elicits equivalent behavioral responses. Here we tested the hypotheses (1) that groups of ants follow trails for longer distances than single ants, and (2) that multiple-component trail pheromone blends such as 3-ethyl-2,5-dimethylpyrazine in combination either with two other antennally-active EFA venom gland constituents or with trail pheromones of heterospecifics modulate trail-following behavior of EFAs. To test these hypotheses, we marked the circular circumference of a filter paper in 1-cm intervals, treated it with synthetic trail pheromone, and video-recorded the distance EFAs, tested singly or in groups of five, followed pheromone trails. According to our data, groups of EFAs follow pheromone trails for longer distances than individual ants, a 3-component trail pheromone blend more effectively induces trail-following than 3-ethyl-2,5-dimethylpyrazine alone, and the presence of heterospecific trail pheromones has a weak adverse effect on trail following by EFAs.