Anatomical origin and isolation of an ethological factor found on the last sternite of the workers of Myrmica rubra L. ( Formicidae, Myrmicinae)

Abstract

On the basis of a logical series of deductions from experiments, it has been shown that the previously described ethological factor found on the last visible sternite of Myrmica rubra workers is a small amount of Dufour gland contents modified on the inner face of the last sternite. The factor may soak the outer surface of the sting or the gonostyles. This factor has, among others, a synergistic effect on the trail pheromone. When laying a trail, food-collecting ants deposit this factor on the ground together with the trail pheromone from their poison glands. The factor can be isolated on silica-gel plates and eluted once with acetone; its R f is 0.36. It resists a temperature of 100°C for at least 5 min and is more volatile than 3-ethyl-2,5-dimethylpyrazine, the trail pheromone of the species.