Key to the known species of Dialarnaca

1 Apical area of male cerci curving, styli shorter (0.23–0.24 mm), about 3.92–4.43 times shorter than the length of male subgenital plate along the midline.................................................................... D. longicerca

– Male cerci straight, styli longer, about 2.33–2.47 times shorter than the length of male subgenital plate along the midline... ................................................................................................... 2

2 Posterior area of male subgenital plate slightly projected, posterior margin shallowly concave in the middle....... D. roseola

– Posterior area of male subgenital plate trapezoidal projected, posterior margin nearly straight................... D. zhoui