Kjærandsen (2009) defined this species group where the species are mainly characterized by having vein R4+5 distinctly downcurved [R4+5-bending index 1.44–1.84, 1.66, n = 26, Fig. 3A), by having only one strong bristle on proepisternum, and by a number of characters in the male terminalia such as the stout, subrectangular hypandrial lobe; the dorsointernal branch of the male gonostylus forming a large, strongly asymmetric, blade-shaped fan with blunt lamellae along the margin; the ventral branch of the gonostylus being shaped like a spatula, and bearing less than five strong, characteristically fan-tipped setae ventrally. The pseudocercus is long and slender. The female terminalia has fused, slender, s-shaped cercus, and a long and slender, but sclerotized postgenital plate. The trisignata-group is distributed in the Holarctic and the Oriental regions and the included species are: P. inthanonensis, P. pectinacea, P. trisignata, and P. tuomikoskii (Fig. 1).