The male genitalia of the L. phaea species-group resemble those of the L. skraelingia speciesgroup, but the uncus is broadly flattened and spatulate with a squared-off apex and the digitus is longer, extending below the valve. Females have a distinctly different bursa than those of the L. skraelingia species-group. Th e corpus bursae is ovoid, not rounded, with less sclerotized signa. Th e appendix bursae is attached to the dorsal corpus bursae rather than to the left side and extends dorsally and to the left. Its surface is grooved producing a weak spiral of approximately 1.5 turns. Th e male antenna is beadlike (L. phaea) to biserrate (1.5× as wide as shaft in two Asian species (Lafontaine and Kononenko 1988)).

Lasionycta phaea is the only North American member of the species-group. Three additional species, L. alpicola Lafontaine & Kononenko, L. buraetica Kononenko, and L. corax Kononenko, are found in central and western Asia (Lafontaine and Kononenko 1988).

The species in this species-group were included in the L. skraelingia species-group by Lafontaine and Kononenko (1988). In addition to the structural differences between the species-groups, L. phaea fails to group with L. skraelingia and L. taigata on CO1 distance analysis, instead clustering near L. secedens (Fig 247).