Brian V. Brown notes that Megaselia is a difficult genus to deal with, containing as it does one-half of the described Phorid flies of the world. Both he and R.H.L. Disney agree that "its monophyly is doubtful" (Brown, writing in Brown et al., 2010).
Of the life histories of members of this genus, Brown comments, they are "scavengers, predators, parasitoids, and herbivores, but the life history of most species is unknown" (Brown, writing in Brown et al., 2010).
Photo location: Boquete, western Panama.
American Insects site