EXCUBIÆ, in antiquity, the watches and guards kept in the day by the Roman soldiers. They are contradistinguished from the vigiliae which were kept in the night. The excubiæ were placed either at the gates and intrenchments or in the camp; for the latter there was allowed a whole manipulus to attend before the prætorium, and four soldiers to the tent of every tribune. The excubiæ at the gates of the camp, and at the entrenchments, were properly called stationes. One company of foot and one troop of horse were assigned to each of the four gates every day. To desert their post, or abandon their corps of guards, was an unpardonable crime.
The triarii, as the most honourable order of soldiers, were excused from the ordinary watches; yet being placed opposite to the equites, they were obliged to have an eye over them.