Diadocidiids are a monogeneric family comprised of close to a dozen species confined to the Holarctic region. Adults of extant forms are sylvan in habit. Larvae spin silken tubes under bark or dead logs.

Only one named species from Baltic amber is known. Matile (1989: 127) recorded an unnamed second species from the Nearctic Region.

*DIADOCIDIA Ruthe, 1831: 1210. Type species: Diadocidia flavicans Ruthe, 1831 [= Mycetobia ferruginosa Meigen, 1830], by monotypy.
ACLADA Loew, 1850b: 33, 35. Type species: Diadocidia parallela Evenhuis, 1994, by original designation.
[Aclada originally proposed without included species. The type species designated is from the first species included within the genus in accordance with the Code.]

parallela Evenhuis, 1994: 138. PA: Baltic Region (Eocene/Oligocene) [A].
[Validated by bibliographic reference to characters of Aclada in Loew (1850: 33, 35), which can serve to diagnose the species under Code Article 13(c).]
parallela Loew, 1850b: 35. Nomen nudum.