Control? I rather think it's boths ways actually. When the pitchers
are young and still catching insects, they will fill with more
fluid when prey is introduced. I'm fairly sure that after the pitchers
are through with their insect collecting, the Nepenthes then use
the pitchers to regulate the water level *inside* of the plants.
Tapping the water stored in the pitchers when the plant is being
dried by sun or the air. I'm not sure if they can then re-fill
the pitchers themselves or if it's simply the rain which helps
keep their resevior (sp?) filled.
Dave Evans