The scramble competition mating system of the sphecid wasp Palmodes praestans (Kohl)

Males of the wasp Palmodes praestans engage in non-territorial patrolling behaviour within a scramble competition mating system, showing great fidelity to their wide-ranging patrolling routes without attempting to monopolize the areas covered. Scramble competition appears adaptive given that mating opportunities are not spatially aggregated in this species, whose females build isolated, single-celled nests. Because of the female distribution pattern, a male's reproductive success in P. praestans probably depends upon the ability to find highly scattered, unmated females. The females of some close relatives of this sphecid wasp form fairly dense nesting aggregations. As mating system theory predicts, the males of some (but not all) of these species focus their searching at these concentrated nesting/emergence sites where potential mates are clustered spatially.