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I think only one row is postocular, with the rest being occipital or something like that.

The name pallifrons suggests a pale frons.

Here is the Nearctic key (from the mid-1980s):

39. Genal bristle about one-half to three-fifths length of vibrissa. Head densely setose behind eyes, with postocular setae in numerous irregular rows. Mid tibia with four to five anterodorsal bristles. Wing crossveins often banded ... Crumomyia Macquart (including Fungobia Lioy)

... Genal bristle less than one-half length of vibrissa. Head with a single row of postocular bristles. Mid tibia with zero to two anterior and zero to two dorsal bristles. Crossveins not banded unless longitudinal veins also darkened ... 40

40. Scutellum with four long marginal bristles only. Hind tibia with an anteroventral bristle below middle. Frons entirely reddish brown to blackish ... Borborillus Duda

... Scutellum with at least six marginal setae, although some may be minute. Hind tibia with only weak anteroventral setae. Frons yellow or orange anteriorly ... 41

41. Hind tibia with a strong apicoventral bristle. Scutellum with four long and two to many tiny marginal setae. Frons completely pruinose ... Copromyza Fallén

... Hind tibia without a strong apicoventral bristle. Scutellum with 8-10 short stout marginal setae. Frons with ocellar triangle mostly bare ... Lotophila Lioy