The sex ratios of Trichoniscus pusillus Brandt (Crustacea: Oniscoidea)

Summary

The frequency of males in the bisexual and parthenogenetic forms of T. pusillus is assumed to be 0·5 and 0·03 respectively. This assumption for the bisexual form is tested with culturing, which demonstrates a numerical equality of the sexes and produces no evidence of differential survivorship of the sexes, and by field sampling of a suspected bisexual population. A statistical technique using the difference in male frequency in the two forms to determine the composition of T. pusillus agg. is presented. Other work on sex ratio in isopods is reviewed.