Male genital musculature of Therevidae and Scenopinidae (Diptera: Asiloidea):: Structure, homology and phylogenetic implications

The male genital musculature of Anabarrhynchus tristis Bigot (Therevidae) and Metatrichia waterhousei (Paramonov) (Scenopinidae) are examined and compared to other flies of the superfamily Asiloidea (Diptera). Evidence from musculature confirms that the inner stylus of Therevidae is homologous with the gonostylus of other asiloid flies. The 'outer stylus' of Therevidae is an articulated process of the distal margin of the gonocoxite, here termed the 'inner gonocoxal process'. The genital musculature of the Scenopinidae is very similar to that of the Therevidae. Metatrichia waterhousei has what we interpret as modified, fused lateral ejaculatory processes lying above the ejaculatory apodeme. The male genital musculature of the Asiloidea is reviewed and implications for the phylogeny of the Asiloidea are discussed. A striking apomorphy of the Asiloidea (except Bombyliidae and Mydidae) is the presence of a third tergosternal muscle bundle M5(3). The presence of gonocoxal muscles M38 may prove to be a synapomorphy of the Asiloidea (excluding the Bombyliidae). Muscle M33 is a synapomorphy of the clade containing Asilidae, Apioceridae and Mydidae. The division of gonocoxite muscle M33 into two bundles may be a synapomorphy of the Apioceridae.