This paragraph of Appian (BC 1.101) reads very much like an excerpt from a collection of ‘wittisms’ or ‘memorable sayings’
So terrible was he and so uncontrollable in anger that he slew in the middle of the forum Q. Lucretius Ofella, the one who had besieged and captured Præneste and the consul Marius, and had won the final victory for him. He did this because, in spite of the new law, Lucretius persisted, though Sulla opposed and forbade, in being a candidate for the consulship while he was still in the equestrian order and before he had been quæstor and prætor, presuming on the greatness of his services, according to the former custom, and captivating the populace. Then Sulla assembled the people and said to them, “Know, citizens, and learn from me, that I caused the death of Lucretius because he disobeyed me.” And then he told the following story: “A husbandman was bitten by fleas while ploughing. He stopped his ploughing twice in order to clear them out of his shirt. When they bit him. again he burned his shirt, so that he might not be so often interrupted in his work. And I tell you, who have felt my hand twice, to take warning lest the third time fire be brought in requisition.” With these words he terrified them and thereafter ruled as he pleased. He had a triumph on account of the Mithridatic war, during which some of the scoffers called his government ” the royalty disavowed” because only the name of king was concealed. Others took the contrary view, judging from his acts, and called it “the tyranny confessed.”
The flea parable is particularly interesting in the tradition of parables. The triumphal jokes should be read in light of the tradition of Roman ribald songs as part of the ritual, particularly ones that poke fun of the commander. Cf. comments about Caesar and Nicomedes at the former’s triumph.