Couplet 91

91a:  Tarsi with 4 distinct tarsomeres; hind coxal plates greatly expanded, hiding most of first ventrite; hind wing, when developed, often fringed with long setae; length 0.7 - 2 mm

Clambidae   p.417

91b:  Tarsi with 5 distinct tarsomeres; hind coxal plates distinct but not hiding most of first ventrite; wing not fringed; size variable