Muret offers some help with line 13 – ‘Pyralides are small flying animals, which have four feet and are found in the isle of Cyprus, of such a nature that they live in fire and die when they move a little too far from it. (Pliny, in the 11th book.)’ More recently the pyralids have been identified as fiery flying insects; and their name has been used scientifically for a range of moths and other lepidoptera (~butterflies). Muret also tells us (on line 14) ‘Dolphins die when they touch the land. (Pliny, in the 9th book.)” – though this one is simpler to understand even without the classical reference.
In line 7, the French would translate best as ‘ominous fire’ – fire which carries a good omen. But ‘ominous’ carries bad associations in English which aren’t appropriate here. Blanchemain has a number of variants. Oddly, the first is just punctuation in line 3 – “Quand je nasquis : il estoit …” – but it shifts the meaning of the first clause, which becomes “The star under which I was born Ruled the heavens with its look When I was born: it was…’ Is Ronsard implying it somehow ceased to be a star and moved into Cassandre’s eyes? As usual the changes cluster in the sestet: En toy je suis et tu es dedans moy, En moy tu vis et je vis dedans toy, Ainsi nos touts ne font qu’un petit monde. Sans vivre en toi je tomberois là bas : La pyralide en ce poinct ne vit pas, Perdant sa flamme, et le dauphin son onde. In you I am and you are within me, In me you live and I live within you, Thus we together make just one little world. Without living in you I would fall down below; The pyralid in this way cannot live If it loses its flame, or the dolphin its sea.
Oeuvres de Ronsard 