Pitcher choice by insects; height, color, size or nectar?

[chibae]

I have a N. red leopard that has a fairly tall main vine, which produces uppers, and two shorter basals. The main vine is twice the height of the basals, while the lower pitchers are easily twice the size of the uppers.

Now, I have noticed over the weeks that this nep has been summering outside, that the uppers are crammed with deteriorating insects while the lowers remain empty.
So, what is attracting them to the uppers? Pitchers higher up so they are noticed first? Sweeter smelling nectar? Does the smaller size matter? Or is it color as the uppers are green not the coloration associated with red leopard lowers.

Thanks all

 

[kulamauiman]

need to ID the insects. if moths being attracted to the uppers they might just be reflecting more ambient light at night. maybe lighter to us they may have a different UV reflective profile.

 

[chibae]

need to ID the insects. if moths being attracted to the uppers they might just be reflecting more ambient light at night. maybe lighter to us they may have a different UV reflective profile.

Didn't detect moth wings or heads but can see yellow jacket bodies

 

[Whimgrinder]

Newer pitchers produce more nectar. It might be that alone.

 

[NemJones]

Newer pitchers produce more nectar. It might be that alone.

I was going to say the same thing because I notice that my newest pitchers are dripping with
nectar, and the older ones loose their luster and glossy liquids on the peristome disappear.