The nigrella species group may be characterized by the following combination of characters: spermatheca club-shaped, capsule approximately spherical and constricted to a narrow duct connected to a narrow, tubular and sinuate stem (Figs 169, 178, 187, 188); median lobe of aedeagus with moderately large bulbus which is streamlined with tubus in dorsal view (Figs 165, 173, 182), the internal sac with two pronounced subapical sclerites (Figs 164, 165, 177, 178, 181, 182); female sternite 8 emarginated medially (Figs 171, 180, 189).
Species included: G. minuta Klimaszewski and Webster, G. nigrella LeConte, G. saccharina Klimaszewski and Webster.