Exploring genital and pregenital musculature in Synthesiomyia nudiseta (Diptera: Muscidae: Reinwardtiinae): Insights into evolutionary relationships with subfamily Azeliinae

AbstractThe male genital, pregenital skeleton, musculature of male terminalia, and the ovipositor were studied in Synthesiomyia nudiseta (Wulp). A comparison was conducted between the terminal segments and muscles of S. nudiseta and previously studied species of the subfamily Azeliinae. Notable differences were found between previously studied species of the subfamily Azeliinae and Synthesiomyia + Muscina. These differences correspond to apomorphic character states in Synthesiomyia + Muscina, including the large size of the ejaculatory apodeme and the powerful constrictors of the ejaculatory apodeme M 23; the completely membranous sternite VI; the membrane connection of the muscle ISM 5 (lower); the small size of pregonites and postgonites; and the joints of the phallapodeme muscles М 21 at the base of the hypandrial arms. Based on these differences, Synthesiomyia + Muscina can be assigned to the subfamily Reinwardtiinae, as has been confirmed by recent molecular studies. However, similarities in the set of pregenital muscles and the set of phallapodeme muscles between Synthesiomyia + Muscina and the Azeliinae were also noted. These similarities may be considered as plesiomorphic character states, indicating their phylogenetic relationship. It can be argued that Reinwardtiinae + Azeliinae constitute sister groups and occupy the basal position within the family Muscidae.