Supporters from both sides turned up in numbers to the Murray Barracks oval to watch what was the main game of the day played in dry and windy conditions.
Flies took a 4-0 lead after only 9 minutes and extended this to 10-2 at half time after a 90 metre try from Gabby Taune.
The second 40 minutes of play belonged to Souths who held the Flies scoreless.
A penalty and a try put the score at 10-8 with 24 minutes left on the clock.
10 minutes later, Souths took the lead after a try from prop Kingston Kambi.