I just played a though influence war with the Arcaean. (BTW, what does mean the WHITE borders?), and even thou I built a LOT (4)of maxed influence starbase near their border, they just seemed un-assimilable. Their influence graph showed that they had a HUGE peak (almost vertical)
But, suddenly, their influenced dropped about for half of its past value, and I got about 1/3 of their empire in my cultural sphere, and about half of them on the border or revolution...
what happened? how can their gain/loose so much influence so quickly?