Ammianus Marcellinus Res Gestae 29.4.7

[7] There, as a lion, because he has lost a deer or a goat, gnashes his empty jaws, just when the forces of the enemy were broken and scattered by fear, in place of Macrianus he made Fraomarius king of the Bucinobantes, a tribe of the Alamanni dwelling opposite Mainz. And soon afterwards, since a recent invasion had utterly devastated that, canton, he transferred him to Britain with the rank of tribune, and gave him command of a troop ¹ of the Alamanni which at that time was distinguished for its numbers and its strength. Bitheridus, indeed, and Hortarius (chiefs of the same nation) he appointed to commands in the army; but of these Hortarius was betrayed by a report of Florentius, commander in Germany, of having written certain things to the detriment of the state to Macrianus and the chiefs of the barbarians, and after the truth was wrung from him by torture he suffered the penalty of death by burning.