AMBARVALIA, an annual festival of the ancient Romans, occurring in May, usually on the 29th, the object of which was to secure the growing crops against harm. The priests were the Arval Brothers (q.v.), who conducted the victims—ox, sheep and pig (suovetaurilia)—in procession with prayer to Ceres round the boundaries of the alter Romanus. As the extent of Roman land increased, this could no longer be done, and in the Acta of the Fratres, which date from Augustus, this procession is not mentioned; but in Virgil, Georg., i. 338 et seq., and in Cato's de Re Rustica (i4i) we have full details and the text of the prayers used by the Latin farmer in thus "lustrating" his own land. The Christian festival which seems to have taken the place of these ceremonies is the Rogation or Gang week of the Roman Catholic Church. The perambulation or beating of bounds is probably a survival of the same type of rite.
See W. W. Fowler, Roman Festivals (5899).