The copulation duration allometry in Centrobolus (Diplopoda: Spirobolida: Pachybolidae)

Abstract

Of the determining factors of copulation duration across arthropods, I reviewed copulation duration variance in forest millipedes. The objective was to calculate the variance in copulation duration. The null hypothesis was mean copulation duration and copulation duration variance were independent of body mass. Copulation duration and standard deviation squared for 4 populations of millipedes were seen in the literature. Copulation duration correlated with it's variance (r=0.95, r 2 =0.90, n=5, p=0.01). Durations ranged from C. anulatus (34.9 minutes) to C. inscriptus (303 minutes). Female mass was correlated to copulation duration variance (r=0.95, z-score=1.86, n=4, p=0.03). Millipedes were similar to some arachnids where the duration of copulation and variance in copulation duration correlated with intraspecific size variation. Female mass correlated to copulation duration (r=0.99, z-score=2.71, n=4, p<0.01). Sexual size dimorphism (SSD) was related to male mass (r=-0.97, z-score=-2.17, n=4, p=0.01). Prolonged copulation duration was interpreted to have correlated with the intensity of sperm competition and female control of copulation duration. Females are thought to control the duration of copulation based on mass.