According to Mommsen, the aerarii were originally the non-assidui (non-holders of land), excluded from the tribes, the comitia and the army.
The distribution of these functions amongst the various comitia, and the differences in their organization, were as follows: The comitia curiata had in the later Republic become a merely formal assembly.
The comitia curiata and the two assemblies of the tribes met within the walls, the former usually in the Comitium, the latter in the Forum or on the Area Capitolii; but the elections at these assemblies were in the later Republic held in the Campus Martius outside the walls.
They were originally a body of jurors which gave a verdict under the presidency of the praetor, but eventually became annual minor magistrates of the Republic, elected by the Comitia Tributa.
Amongst its members the following may be mentioned: Gnaeus Domitius Ahenobarbus, tribune of the people 104 B.C., brought forward a law (lex Domitia de Sacerdotiis) by which the priests of the superior colleges were to be elected by the people in the comitia tributa (seventeen of the tribes voting) instead of by co-optation; the law was repealed by Sulfa, revived by Julius Caesar and (perhaps) again repealed by Marcus Antonius, the triumvir (Cicero, De Lege Agraria, ii.
For the purpose of passing the lex curiata, and probably for its other purposes as well, this comitia was in Cicero's day represented by but thirty lictors (Cic. de Lege Agraria, ii.
The comitia survived the Republic. The last known act of comitial legislation belongs to the reign of Nerva (A.D.
Thenceforward there is no record of the office till 82 B.C., when the senate appointed an interrex to hold the comitia which made yh, Sulla dictator (Appian, Bell.
But in Cicero's time they were elected by the Comitia Tributa.
Under the terms of this the consuls, who were optimates, bound themselves to betray their party by securing, apparently fraudulently, the election of the candidates while they in turn bound themselves to procure two ex-consuls who would swear that they were present in the senate when supplies were voted for the consular provinces, though no meeting of the senate had been held, and three augurs who would swear that a lex curiata had been passed, though the comitia curiata had not been convened (Att.