Promalactis is represented by the combination of the following characters: the smooth head with metallic lustre, the lanceolate forewings with various dark or white markings against yellow to deep ochreous-brown groundcolour; the variously shaped symmetrical or asymmetrical valvae and a narrow to very broad sacculus in the male genitalia; and a developed to ill-defined lamella postvaginalis and an elongate thin ductus bursae in the female genitalia.
Biology
Little is known about the biology of this genus. Meyrickreported that larvae fed on rotten wood or bark of Pinaceae and other trees.