Mating Order Establishes Male Size Advantage in the Polygynandrous Millipede Centrobolus inscriptus Attems, 1928

Diplopoda resembled the majority of invertebrates where Sexual Size Dimorphism (SSD) was reversed. The objective: SSD was to be investigated in the genus Sphaerotherium. Male and female morphological data were obtained from the literature; this included male and female width, volume, and SSD for S. cinctellum, S. commune, S. compressum, S. punculatum, S. spinatum, S. tenuitarse, and S. tuberosum. Linear regressions were performed between the five morphological variables and latitude, precipitation, and temperature. SSD was strongly correlated with precipitation (r=0.76, Z score=1.97, n=7, p=0.02); related to the mating system, seasonality, and oviposition. Female width was related to temperature (r=0.75, Z score=1.93, n=7, p=0.03); related to fecundity selection. SSD was marginally related to temperature (r=0.61, Z score=1.42, n=7, p=0.08).