1. SP. ICILIUS, was one of the three envoys sent by the plebeians, after their secession to the Sacred Mount, to treat with the senate. (B. C. 494.) He does not appear to have been elected one of the first tribunes, upon the establishment of the office in B. C. 493; but he was chosen tribune of the plebs for the following year (B. C. 492). In his tribunate he vehemently attacked the senate on account of the dearness of provisions, and as the patricians attempted to put him down, he introduced and procured the enactment of a law ordaining, that whosoever should interrupt a tribune when addressing the people, should give security to the tribunes for the payment of whatsoever fine they might inflict upon him, and that if he refused to do so, his life and property should be forfeited. ( Dionys. A. R. 6.88, 7.14, 17; comp. Cic. pro Sest. 37.) Niebuhr remarks (Hist. of Rome, vol. ii. p. 232), that this law could not have been passed before the Publilian law (B. C. 471), which transferred the election of the tribunes from the comitia centuriata to the comitia tributa, and which gave the tribunes power to originate measures in the comitia tributa, a power which they had not possessed in the comitia centuriata. He therefore supposes that the Icilian law was enacted in B. C. 471, in which year a Sp. Icilius is mentioned as one of the first five tribunes elected by the tribes. (Liv. 2.58.) It is therefore most probable that this law was not passed till B. C. 471; but there is no reason for believing that the Sp. Icilius who was tribune in B. C. 492, is a different person from the tribune of B. C. 471. Dionysius speaks (9.1) of a Sp. Icilius, who was tribune of the plebs in B. C. 481, and who attempted to force the patricians to pass an agrarian law, by preventing them from levying troops to carry on the war against the Aequi and Veientes. This tribune is called by Livy (2.43), Sp. Licinius ; but if the name in Dionysius is correct, he is probably the same as the tribune of B. C. 492, so that Sp. Icilius would have been tribune for the first time in 492, the second time in 481, and the third time in 471.

In the year after his first tribunate (B. C. 491), according to the common chronology, Sp. Icilius was elected to the aedileship, and took an active part in the prosecution of the proud patrician, Coriolanus. He and his colleague L. Junius Brutus, were commanded by the tribunes to seize Coriolanus, but were driven away by the patricians by main force; and when they afterwards attempted to hurl him down from the Tarpeian rock, they were again prevented by the patricians. (Dionys. A. R. 7.26, 35.)