Phaedrus is now recognized as the first writer to compile entire books of fables in Latin, retelling the Aesopic tales in "senarii", a loose iambic metre. The dates of composition and publication are unknown. However, Seneca the Younger, writing between 41 and 43 CE, recommended in a letter to Claudius' freedman Polybius that he turn his hand to Latinising Aesop, ‘a task hitherto not attempted by Roman genius’ ("Ad Polybium" 8.3). This suggests that nothing was known of Phaedrus’ work at that date. By the mid-80s Martial was imitating him and mentions his mischievous humour ("improbi jocos Phaedri"). The next reference is a homage by his fellow fabulist Avianus near the start of the 5th century, who claims the five books of fables as one of his sources in the dedication of his own work.