This bitter Catullus poem is thought by some to be his last sign-off from Lesbia. It and poem 51, which the same commentators think is probably his first to her, are the only two that he wrote in Sapphic metre. So that would fit neatly, though the evidence is thin. His messengers to her, Furius and Aurelius, come in for very hard words in other poems, notably the grossly rude no. 16. Whether they were really enemies, or friends who had to put up with rough treatment in jest, we don’t know. In the grandiose first part of the poem, Catullus ironically commends Furius and Aurelius for their willingness to travel to the ends of the Earth with him. The high tone is designed to contrast with the very harsh farewell to Lesbia (who is not named) at the end.
See the illustrated blog post here.