Sexual bimaturism in the millipede Centrobolus inscriptus Attems (Spirobolida: Trigoniulidae)
Mark Ian Cooper
Millipedes haverndeterminate growth and adult body sizes are fixed. In the sexually sizerndimorphic genus Centrobolus intergenerational sexual differences in bodyrnsize was examined in a population of C. inscriptus. Millipedes werernmeasured with minimum measurement error and volumetric body size calculatedrnaccording to l.π.r2. Four male and five female stadiarnwere detected in the population and figured. One evolutionary explanation forrnthe extra female stage is fecundity selection for larger female size. This isrnpreliminary evidence for sexual bimaturism in arthropods.
Fig.: The sexual differences in the distribution of body volumes (mm3) calculated for the millipede Centrobolus inscriptus from a population sampled during the mating season.