Effects of group density on call rate, phonokinesis, and mating success in Palmacorixa nana (Heteroptera: Corixidae)

Abstract

Little information exists on the effects of density on the calling of acoustic insects. In the field, density of Palmacorixa nana males varies markedly. In the laboratory, such variation appears to be a result of males forming groups around each other. When males aggregate, the number of spontaneous calls per male per minute increases exponentially. Females show a phonokinetic preference for the mean call rate of the densest male aggregation. Males show a phonokinetic preference for the less dense aggregations. Females always preferred the greatest acoustic power. Phonokinetic responses of male and female P. nana to groups of conspecific males were consistent with an assessment of the reproductive costs and benefits of associating with a group. As density increased, both the costs and benefits to males of associating with a group increased. In denser aggregations, males had more copulations per mounting attempt but had more agonistic interactions and mating interference from other males.