|Sarracenia purpurea, the Purple Pitcher Plant|
The leaves are specialized for this trapping function in various ways.
First, the leaves are hollow in order to hold water. In the photo below, something had nibbled away parts of the hoods of these pitchers so now the water is more visible.
The insects are drowned in this water and processed and utilized by various organisms, including the pitcher plant.Secondly, the pitcher's traps are baited by nectaries near the lip of the hood. Also the plant has color patterns and odors to help attract insects.
Thirdly, the pitchers have various means of causing the insects to loose their footing.
Here is a cross-section of a pitcher showing the hair-lined hood on the right and the dark muck of leftover insect parts an the left.
You can see some lighter colored larvae of the pitcher plant midge in the dark muck. These thrive there on the drowned insect parts despite the fact that the pitcher plant's water is lethal to many other insects
Purple Pitcher Plant.
I also posted on this blog about the Purple Pitcher Plant.