Couplets: 1  2  3  4  5  6  7  8  9  

Key to Adults of Holarctic Blephariceridae: Couplet 4(1)

Lamellae of respiratory organ semicircular, spreading, in the form of thin, flexible, leafy projections or low crests that do not rise high above body...Philorus Kellogg	Lamellae of respiratory organ usually elongate, compact, in the form of dark, rigid, erect, projections; if leaflike, lamellae rise high above body...5