The behavioral ecology of mating in harvester ants (Hymenoptera: Formicidae: Pogonomyrmex)

1. The four sympatric species of Pogonomyrmex (P. barbatus, P. desertorum, P. maricopa and P. rugosus) frequently conduct their nuptial flights on the same days; however the daily timing rhythms of their mating swarms differ strongly. 2. Mating takes place on species-specific, perennial mating sites. In our study area the mating sites of P. barbatus and P. rugosus were located on the ground, those of P. desertorum and P. maricopa on bushes and trees. 3. Males mark these mating sites with the secretions of their mandibular glands. Apparently additional males as well as females are attracted by these secretions. 4. During mating activities a strong male competition exists. In P. barbatus and P. rugosus an average of 4-5 males, in P. desertorum and P. maricopa an average of 2-3 males simultaneously, compete, for access to one female. 5. Multiple matings have been observed in all four Popogonomyrmex species. 6. Sexual behavior is regulated by a stimulation pheromone produced in the female's poison glands and apparently also by a species-specific surface pheromone which the males perceive only when they approach closely enough to make direct antennal contact. 7. The combination of distinct daily activity rhythms, partial mating site isolation together with the ability of males to discriminate conspecific females from females of the other species isolates the sympatric Pogonomyrmex species from each other. 8. The mating aggregations of Pogonomyrmex are compared with the lek behavior of vertebrates.