Characteristics & Similar Species
Clusiodes terminalis (holotype figured to right) is a darkly-pigmented species with pale fore legs and a nearly white face, gena and occiput. Other dark Nearctic representatives of the C. geomyzinus species group can be distinguished from C. terminalis by slight colour differences (see key), but genitalic differences are pronounced and should be examined to verify species determinations.

Clusiodes orbitalis and C. nitidus both differ from C.  terminalis in having the wing infuscated along the entire costal margin, and C. caestus differs in having a darker face and shoulders (rarely with white stripe).

Clusiodes terminalis is nearly identical to C. ater, but the male face and fore leg of C.  terminalis are yellow (light yellow to dark brown in C. ater), and the thin anterodistal process of the surstylus is somewhat smaller in C.  terminalis. These characters appear to be weak justification for separating these sympatric sister species, and we suspect that C. ater and C.  terminalis are synonyms.

Biology
Clusiodes terminalis species has been collected in Populus/Picea dominated woodland, but otherwise nothing is known of the biology of this species.