Moved from Cerioidini.

Phantastic photo! It very clearly illustrates a robustly-"complete" post-metacoxal bridge...i.e. the uniformly-wide, uninterrupted, entirely-sclerotized band (black here, with subtle transverse striations) spanning the area on the bottom of thorax just behind the attachment points of the hind legs (at the bases of their coxa).

The black "bridge" here (see full-size image) is nestled between two somewhat paler, brownish connective membranes: anteriorly, a slender, shallowly "v"-shaped area between the bridge and the bases of the coxa; and posteriorly, a larger "lune"-shaped area between the bridge and the shiny trapezoidally-shaped sclerite representing the sternite of the 1st abdominal segment. Also visible are the membranous connective tissues joining the anterior sternites laterally to their corresponding tergites...giving a sense of how the cerioidine can move & flex its abdomen, even though it's enclosed by an exoskeleton of relatively rigid abdominal sclerites (i.e. sternites below and tergites above).

A "complete" post-metacoxal bridge (as seen in the left panel of this key couplet from the CJAI Syrphidae key) is one of the main defining characteristics for genus Polybiomyia, along with a petiolate abdomen (= constricted and somewhat elongate 2nd abdominal segment), and a relatively short antennifer (as seen in the right panel of the preceeding key couplet).

In Sphiximorpha, the bridge is "incomplete"...meaning the transverse scleroterized band is clearly interrupted in the middle by a membranous area (i.e. there is no true bridge, it's broken!).