author(s)
Mark Cooper

abstract
The present research aimed to study relative sexual size dimorphism of Centrobolus anulatus compared to congenerics. Millipedes illustrated reversed sexual size dimorphism (SSD) as females were larger than males and broke the rule as this dimorphism increased with body size. SSD was calculated in 18 species of the genus Centrobolus and illustrated as a regression. The approximate relative position of C. anulatus was shown from measurements taken in South Africa (2018). The average size of C. anulatus was 74.23529412 X 5.685882 mm (n=17); males measured 69.2 X 5.264 mm (n = 5) and females were 76.3 X 5.861667 mm (n = 12). Log volume measurements were (females/x = 3.31359939 mm³; males/y = 3.2377543 mm³). The difference between the correlation coefficients for the species and the genus were not highly significant (r_a = 0.86207, r_b = 0.85; n_a = 17, n_b = 18; Z = 0.12; P (one-tailed) = 0.4522, P (two-tailed) = 0.9045). The mean volume ratio for C. anulatus was 1.02342521 which differed from 1 (t=3.59722; p-value = 000747; p <.01; n=17). Evidence suggests sexual bimaturism as proximate cause and competition as ultimate cause for SSD in Centrobolus.