Relative sexual size dimorphism Centrobolus ruber (Attems) compared to 18 congenerics

Abstract

The present research was aimed to study relative sexual size dimorphism of Centrobolus ruber (Attems) compared to 18 congeneric. Millipedes illustrate reversed sexual size dimorphism (SSD) where females are larger than males; and corroborate Rensch’s rule as this dimorphism increases with body size. SSD was calculated in 18 species of the genus Centrobolus and illustrated as a regression. The approximate relative position of C. ruber was shown from measurements taken at Port Shepstone, South Africa (February 1996). The size of C. ruber was 57.8 X 5.0 mm: 62.3 X 6.1 mm (males: females; n=18) and logged (females/x = 3.267; males/y = 3.057) and plotted. The mean volume ratio for C. ruber was 1.621. The evidence suggests the proximate cause for SSD in C. ruber is sexual bimaturism while the ultimate cause in Centrobolus is intersexual competition.