The prediction that copulation duration is shorter when sexual size dimorphism increases was tested in
juliform millipedes at the population-level and species-level by tabulating and correlating ratios for mean
sexual size dimorphism ranging from 1.0-1.6 (n=310) with mean copulation duration ranging from 34-
206 minutes (n=391) in 8 taxa: ord. Spirostreptida fam. Odontopygidae gen. Odontopyge (n=2spp.),
Spinotarsus (n=1sp.) and fam. Spirostreptidae gen. Calostreptus (n=1sp.), Doratogonus (n=1sp.); and
ord. Spirobolida fam. Trigoniulidae gen. Centrobolus (n=3spp.). Copulation duration and sexual size
dimorphism were inversely correlated across populations (r=-0.5975, N=11, P=0.05) but not species.
This study contributes to the allometry of copulation.
