Morphology of the male genitalia in Brachymyrmex Mayr (Hymenoptera: Formicidae), and their implications to the Formicine phylogeny

The male genitalia of Brachymyrmex Mayr are examined, and homologies established to a novel character state of the lateral apodeme on the penisvalvae, the dorsal crest.  The functional morphology of the dorsal crest is described for the Brachymyrmex depilis Emery and Brachymyrmex patagonicus Mayr species groups, and hypotheses are presented as to its evolution. The dorsal crest of Brachymyrmex and the dorsal position of the penisvalvae lateral apodeme in Myrmelachista are evaluated within the context of molecular phylogenies. We transfer Brachymyrmex, and Myrmelachista into the resurrected tribe Myrmelachistini, based on the morphology of the penisvalvae, and correlation to molecular studies. We describe histological methodologies adapted from parasitology for the preparation, differentiation, and permanent storage of minute ant genitalia structures and musculature therein.