Male ant genitalia: musculature, functional morphology and homology

The genitalia of male ants are interpreted in the context of the broader Hymenoptera. For the first time, muscle homologies are established across distantly related ant subfamilies. Moreover, the homology of ant genital valves with the basal Hymenoptera is established. Fifteen muscles in total are found in the external genitalia of male ants and all are homologous with the musculature of basal Hymenoptera (Schulmeister, 2001). Secondary fusion, reduction or losses of muscles have occurred in different ant lineages. Possible movements of the genital valves are largely consistent across the ant subfamilies, with the most variation occurring for the penisvalvae and volsellae. The identity of the true digitus of army ants (Ecitoninae) is revealed to be a small plate of variable form and attachment at the base of the distivolsellar shaft.