Carsia sororiata, the Manchester treble-bar, is a moth of the family Geometridae.

In some specimens, the two lines form "bridge" in the posterior half of the wing.

The micropylar rosette is 8-leaved; sides with irregular reticulation, in places undeveloped.

The larva is rather stout, of uniform thickness, the dorsal surface rather deep brownish-red, with very fine blackish-red dorsal and subdorsal lines and a broad bright yellow lateral stripe containing at the folds between the middle segments some beautiful red spots; venter pale greenish yellow with paler, dark-edged central line.

The larvae feed on various Vaccinium species (including V. uliginosum, V. oxycoccos and V. myrtillus) as well as Rubus arcticus.