A COMPARISON OF SIZE, SEX-RATIO, AND DISPERSAL IN 3 COCCINELLIDS

Relationships between body size, sex ratio, dispersal and abundance pa tterns of three congeneric coccinellids [Hippodamia convergens Guerin- Meneville, H. tredecimpunctata tibialis (Say), and H. parenthesis (Say )] were investigated. Sex ratio differed from 1:1 for H. tredecimpunct ata and H. parenthesis; in both cases there was an excess of females. Sex ratio differed among years for all three species. Body size differ ed among sexes for two of the three species, with females being larger than males. Body size differed among years for all three species. A r anking of species with respect to relative variation in body size amon g years was H. parenthesis > H. tredecimpunctata tibialis > H. converg ens. An identical arrangement of species was obtained when comparing t he range of variation in sex ratio among years. A dispersal index, rep resenting propensity for flight, displayed the opposite arrangement, b eing smallest for H. parenthesis and largest for H. convergens. If a p opulation in a year was composed of large adults, larvae were abundant the next year for H. convergens and H. tredecimpunctata tibialis. If adults of these two species were abundant in a particular year there w as a shift in sex ratio towards more males the following year. A high percentage of females in a particular year tended to result in an abun dance of immatures the following year. Comparison of the size and sex ratio of coccinellids caught in agricultural fields and on flight inte rception traps stationed adjacent to fields indicated that males and f emales of each species from field collections were larger than those f rom traps. Sex ratios of beetles from fields did not differ from those from traps. Results are discussed in terms of the life history strate gies of the three species that permit them to exploit spatially and te mporally varying agricultural landscapes.