nepenthes phases

[Millipede]

so whats the deal with all the phases a nepenthes goes through? theres lower, intermediate, and upper pitchers. and they all apparently look different? do they gradually morph into the next phase as the vine progresses or just "all of a sudden"? how does the plant know? and - is there a reason for the vine to change like this?

thats a lot of questions i know, but i cant seem to find much good info about this

technical jargon welcome

 

[carnivoure12]

Intermediates are a 'fusion' between lower and upper pitchers so the transition isn't sudden between lowers and uppers. generally plants start vining and produce more slender less colorful, and differently shaped pitchers in order to capture different pray, more liekly flying insects that might be attracted to different colors. Lower pitchers are more adapted to captureinsects that crawl so and so.

How do they know? I guess its the same thing as how does it know when to start ving and stuff it just happens