Determinants of male mating success in a scorpion

Abstract

The scorpion, Euscorpius flavicaudis, occurs in a large, well established colony at Sheerness in Kent. Males exhibit a life-history polymorphism: some males mature at the sixth instar, and some delay maturity until the seventh. The reproductive ecology of this population was studied, both at Sheerness and in the laboratory. Males became vagrant before the mating season, and searched for ‘cracks’ occupied by a female. Females did not become receptive to males until their offspring became independent. When a male encountered an unreceptive female, he cohabited with her, and attempted to repel intruding males. In ‘ownership’ contests, larger males were more successful than smaller males, but if the contestants were matched in size, the owner usually won. Large males had a higher mating success than small males, which reflects their ability to take over guarded females and to mate with reluctant females. The costs and benefits of being either a sixth or a seventh instar male are discussed.