Dispersal polymorphism (the occurrence of migratory and flightless forms in the same population) is a widespread phenomenon among insects. For most insects including planthoppers (Homoptera: Delphacidae), there is a reproductive cost associated with dispersal ability as evidenced by the reduced fecundity and delayed oviposition of migratory compared to flightless females. Corresponding information for males on the relationship between dispersal ability and reproductive success is virtually absent. As a result, our understanding of the evolution, maintenance, and population consequences of variation in dispersal capability is based almost exclusively on females. Failure to establish fitness differences between male wing forms challenges our current knowledge of the ecological and evolutionary basis for the existence of dispersal polymorphisms. Several characteristics of planthopper mating systems suggest the presence of costs associated with migratory ability in males and that migratory and flightless males contribute differentially to population dynamics at different densities. The research outlined herein seeks to elucidate intrinsic differences between migratory and flightless males of the planthopper Prokelisia dolus in their 1) competitive ability (male / male interactions, ability to locate mates, attractiveness to females, 2) survivorship, propensity to disperse, ability to inseminate mates, and 3) mating success and contribution to population growth across a range of density conditions. This research will supply the empirical basis for the development of more general hypotheses (which include both male and females) to examine the widespread phenomenon of dispersal polymorphism in insects.
