SeasonalityIn Canada, C. discalis is found from late May to early August.
IdentificationThe most distinctive of Alberta's deerflies. Large, with a length of 8-11 mm. The females overall are pale yellow and grey with black markings. On the head (Teskey 1990) they are black above the antennae and yellow below (except for black spots on the clypeus), and covered all over with grey pruinosity (powder); the ocellar areas are glossy black; the antenna are slender, and darker laterally than dorso-ventrally; the palpi are yellow. The thorax is prominently striped with grey and black; the legs are yellow, with the joints and the apical tarsal segments darkened; the wings have a prominent fenestrated (with window-like openings) pattern. The abdomen dorsally has double rows of black spots, with the spots on tergite 2 united anteriorly; the sternites are yellow (Teskey 1990).
Males are similar but are darker overall, especially on the antennae, wings, scutum, and abdomen.
The fenestrated pattern of infuscation in the wing cells (infuscation around the perimeter of the cells but not in the center) is diagnostic except for some C. fulvaster, but the antennae of the latter are always much more robust. Males of C. discalis are unique in that the eyes are not holoptic (touching) but are separated by the width of an ocellus (Teskey 1990).