Fecundity and size in the housefly: investigations of some environmental sources and genetic correlates of variation

Environmental sources and genetic correlates of variation in fecundity and size were studied in field and laboratory housefly populations in central Iowa, U.S.A. Electrophoresis of enzymatic proteins was used to monitor genotypes and heterozygosity. In the field, mean fecundity declined as adult densities increased. Fecundity varied greatly within breeding seasons. Fly body size varied spatially and temporally during summer and winter. Fecundity and size were positively correlated. Size was independent of genotypes at the six loci studied. No relationship was observed between heterozygosity and the magnitude or variability of body size.