Frumentarii Frumentarii were officials of the Roman Empire , originally wheat collectors , who also acted as the secret service of the Roman Empire in the 2nd and 3rd centuries . There are two main sources of information about the " frumentarii " , inscriptions on gravestones and anecdotes where the actions of individual frumentarii are mentioned by historians . From what is known of the Frumentarii , they always worked in uniform . The Empire was based on patronage , not an ideology ( until Theodosius I ) . From inscriptions ; one of the few things known about the frumentarii is that they were mostly attached to individual legions , except for a few centurion frumentarii . Attachment to individual legions suggests that their main function was , as the name suggests , to service those legions with supplies . Frumentarii appear to have spent a lot of time travelling and had a base in Rome at the Castra Peregrina . Frumentarii were obviously proud of their status if they put the rank on their gravestones . There are a number of inscriptions honouring the " genie " of the Castra Peregrina , this suggests that the frumentarii had high morale and social status . History . It had been long - standing policy of the Roman legions and armies of occupation to utilize informers and spies , but never in an organized fashion . This was especially true in the city of Rome which was rife with whispers and endless conspiracies . There are two inscriptions of " frumentario canaliculario " found at Arles and Córdoba which suggest that some frumentarii had special knowledge of inland navigation . For all armies , the most important unit of military intelligence was an enemy ' s geographical location . This included mapped land and communication routes , enemy legion sizes , landmarks , and strategic objectives such as granaries or farms . The Antonine Itinerary might be the product of the frumentarii . Titus used special messengers and assassins of the Praetorian Guard to carry out executions and liquidations ( the Speculatores ) ; however , they belonged to the Guard and were limited in scope and power . By the 2nd century , the need for an empire - wide intelligence service was clear . But even an emperor could not easily create a new bureau with the express purpose of spying on the citizens of Rome ' s far - flung domains . A suitable compromise was found by Hadrian . He envisioned a large - scale operation and turned to the " frumentarii " . The " frumentarius " was the collector of wheat in a province , a position that brought the official into contact with enough locals and natives to acquire considerable intelligence about any given territory . Hadrian put them to use as his spies , and thus had a ready - made service and a large body to act as a courier system . The following story has been used as evidence of the role of the frumentarii : " ( Hadrian ' s ) vigilance was not confined to his own household but extended to those of his friends , and by means of his private agents ( " frumentarios " ) he even pried into all their secrets , and so skilfully that they were never aware that the Emperor was acquainted with their private lives until he revealed it himself . In this connection , the insertion of an incident will not be unwelcome , showing that he found out much about his friends . The wife of a certain man wrote to her husband , complaining that he was so preoccupied by pleasures and baths that he would not return home to her , and Hadrian found this out through his private agents . And so , when the husband asked for a furlough , Hadrian reproached him with his fondness for his baths and his pleasures . Whereupon the man exclaimed : " What , did my wife write you just what she wrote to me ? " . " The " frumentarii " quickly earned the hatred of society . In the 3rd century , association with the heads of the service could produce severe repercussions . In 217 , Macrinus appointed Marcus Oclatinus Adventus , the former head of the " frumentarii " and the prefect of the Praetorian Guard , to the Senate . With one decision , Macrinus alienated most of the Roman establishment and made his own political destruction inevitable — so much were the " frumentarii " resented . Diocletian terminated the " frumentarii " because of their abuses and loathsome reputation . The emperor ' s decision netted him great popularity , but a short time later the equally sinister and far better organized " agentes in rebus " were created in its stead .