Enargia fausta Schmidt 2010

Description. Head and thorax – Colour ranging from pale ochre, yellow ochre, to rusty orange yellow, otherwise not differing from that of E. infumata. Wings – Forewing length: males 17.5 mm (n = 6), females slightly larger overall at 19.4 mm (n = 5); forewing ground color varying from yellowish ochre to rusty ochre, but not exhibiting the very pale ochre or greyish phenotypes observed in E. infumata; dark markings varying from charcoal grey to brownish grey, usually highly contrasting and sharply defined; angle of antemedial line rounded and obtuse, but less so than in E. infumata, averaging 110°–120°; postmedial line evenly slightly sinuate medially, only rarely evenly rounded; medial band moderately to poorly developed, co-varying with dark terminal and subapical shading but without the variation extremes seen in E. infumata; pale subterminal line present in specimens with dark terminal shading (Figs 12, 15); reniform and orbicular usually paler than ground colour, rarely concolorous; reniform and orbicular with sharply defined, uninterrupted border; base of reniform (toward anal margin) with dark grey spot of varying size, but spot nearly always darkest of forewing markings; fringe concolorous with ground colour; ventral forewing less variable than dorsum, ground colour pale yellowish ochre with postmedial line and reniform spot variously developed, more so in specimens with contrasting dorsal markings, and antemedial line absent. Hindwing ground colour pale yellowish ochre with maroon-grey dark shading of varying extent, but not as grey or extensive as variants of E. infumata; postmedial line and broader, diffuse subterminal band visible when dark markings developed, varying to entirely absent; medial line better defined ventrally, with ventral discal spot similarly dark (rarely visible dorsally). Abdomen – not differing from that of E. infumata. Male genitalia – (Figs 56, 60). As for E. infumata, but differing in following characters: valve length 3.3–3.5 mm; vesica with free apex of both cornuti equal in size to each other, ranging from 0.11– 0.15 mm; right cornutus small, i.e., length of sclerotized plate of right cornutus only 2.0–2.5 × greater than length of free apex of cornutus (Fig. 60). Female genitalia – (Fig. 65). As for E. infumata, but differing in size and shape of corpus bursae, in that basal duct-like part shorter and more poorly defined, with a more gradual widening toward apical sac-like chamber; corpus bursae 3.5–4.0 × length of segment VIII.

Distribution and biology. Enargia fausta has a narrower distribution than E. infumata and is essentially restricted to the boreal forest and boreal-deciduous forest transition zone, and unlike E. infumata does not range south along the Rocky Mountains nor as far north. Specimens examined range from central Alberta to New Brunswick (but see also Remarks, below) and in the East as far south as the Ottawa River Valley, but the species presumably also occurs in appropriate habitats in northern New York and New England; Ferguson (1954) illustrates a specimen from Glennville, Nova Scotia. Reports of this species from northeastern Ohio (Rings et al. 1992, as E. infumata) need to be verified. Flight dates range from late July to early September with most records after mid-August. As discussed under E. infumata, the peak flight of E. fausta is three to four weeks later than that of E. infumata. Available records indicate that this species is much less common than E. infumata. It appears that the preferred larval host is white birch (Betula papyrifera Marsh.) based on specimens reared from larval collections by the Forest Insect and Disease Survey (NOFC), and also trembling aspen (Populus tremuloides Michx.), with a single stunted specimen reared from balsam poplar, Populus balsamifera L.. A preference for birch would explain the narrower habitat preference, more restricted range, and lower abundance of this species compared to E. decolor and E. infumata, both associated with aspen.