Note the dorsally "indented" 5th tergite, giving the initial impression of a female here. But the indented 5th tergite here is actually a distinctive character of male A. obsoleta, as mentioned in couplet 12 of the key in Sabrosky (1948)...and dipicted (somewhat weakly) in Fig. 36b of Plate XII of Cole (explanation for figures here).

Note also the very robust size of the abdomen in this Acrocera...Cole (1919) states A. convexa is similarly robust.