H. trilineatus Fabricius.

Syrphus trilineatus Fabr., Syst. Ent., p. 766 (1775). Eristalis trilineatus Fabr., Syst. Antl., p. 238; Wied., Auss. Zweif., ii, p. 168 (1830). Helophilus trilineatus White, Voy. “Erebus” and “Terror” Ins., pl. 7, fig. 19 (1874); Walker, Cat. Dipt. Brit. Mus., p. 607 (1848); Hutton, Cat. Dipt. N.Z., p. 41 (1881); Trans. N.Z. Inst., vol. 33, p. 38 (1901).

A fly closely resembling antipodus, but more robust and much larger.

♀. Differs from antipodus in the following characters: Eyes more approximated, the black of upper front, vertex, and ocellar triangle permanent in all lights only on the triangle, the yellowish-brown of lower front being reflected over upper front and vertex, thus forming brownish mottlings in some lights; transverse band across antennae broader at frontal lunule; vestiture of front and vertex short; oral margin broadly margined with blackish brown, which is not upturned to any extent along anterior margin; oral margin not distinctly notched in front (fig. 77); cheeks cinereous to pale yellow and clothed with whitish hairs; occiput cinereous.

Median black stripe of thoracic dorsum not narrowly spilt anteriorly; upper two-thirds of pleurae cinereous-yellow; scutellum black in some lights but otherwise as in antipodus. Anterior and middle femora blue-black on basal half, otherwise orange—red; posterior femora altogether blue-black, very much broadened to a bristly prominence distally below, and with a stout spinose tooth below near base (fig. 74); around this tooth and distal prominence of posterior femora orange-red, and the lower side distinctly spinose; anterior and middle tibiae and all the tarsi orange-red; posterior tibiae orange-red but for a broad blue-black area at base, and with a distinct apical tooth below.