Diodorus Siculus relates how the Sybarites, whose city had been destroyed by Croton, were assisted by other Greeks in founding Thurii in 446/445 BC.
According to Diodorus, the Sybarites had assigned the most important offices to themselves, had their wives sacrifice to the gods the first and took the land which lay the closest to the city.
[5] Wonder argues the cities formed this alliance in the second half of the 5th century BC because they felt threatened by neighboring Greek city-states in Southern Italy.
[5] In the early fourth century BC the situation drastically changed when Dionysius I of Syracuse and the Lucanians threatened the Greek cities of Southern Italy.
Wonder thinks Sybaris on the Traeis probably was a member of the league together with Croton, Caulonia, Thurii, Rhegium and Velia by 389 BC.
[5] Diodorus Siculus writes that Sybaris on the Traeis was eventually destroyed by the Bruttii, but does not give a specific date.