Male genitalia of Exeretonevro Macquart (Diptera : Xylophagidae): Structure, function and phylogenetic implications

The search for phylogenetically informative, adult morphological characters to clarify the relationships of the xylophagid genus Exeretonevra with oth er members of the lower Brachycera has yielded few synapomorphies. In this study, the male genital musculature of Exeretonevra angustifrons Hardy is e xamined and compared with other members of the lower Brachycera to ascertai n whether this data set can support the inclusion of Exeretonevra in the in fraorder Xylophagomorpha. Most genitalic muscle complexes of Exeretonevra c onform to the plesiomorphic brachyceran configuration, with those of the ce rci, epandrium and hypandrium possessing some apomorphic features. Although larval morphology and molecular evidence conclusively place Exeretonevra i n the Xylophagidae, the male genital musculature suggest an affinity with t he superfamily Asiloidea (infraorder Muscomorpha). In particular, Exeretone vra is the only taxon outside the infraorder Muscomorpha with a third tergo sternal muscle bundle M5(3) present. No synapomorphies of genital musculatu re support the inclusion of Exeretonevra within the Nemestrinidae, a placem ent that has been supported by previous authors. We show that changes in th e plane of movement of sclerotised structures may be correlated with change s in muscle attachments. Phylogenetic conservatism and extensive homoplasy are features of the male genitalic musculature of lower Brachycera and Exer etonevra is no exception.