Mean adult longevity by sex, treatment, and milieu. Female (circles) and male (squares) longevity was measured in both single sex (open symbols) and mixed sex (closed symbol) milieu. Cages were treated as replicates in all cases. The treatment (stud vs. dud) × milieu interaction is non-significant in both sexes (Table 2). Points are offset in some cases for clarity. Error bars are ± SE.