An otherwise unknown female deity to whom the Arvales fratres devoted the sacrifice of the month of May; nothing is known about the connection of the Dea Dia (DD) with a Dia from Amiternum (CIL I2 2, 1546) and the Greek Dia. Her name derives from the adjective dius and is connected with the space of heaven, probably the ‘good light of heaven’. The thesis that DD is an indigitation ( Indigitamenta) of Tellus or of Ceres cannot be maintained.
Bibliography
R. Schilling, Rites, cultes, dieux de Rome, 1979, 366-370.