Wasps are frequently attracted to Sarracenia's, and like many other visiting insects fall into the trap itself.
However unlike other insects, some wasps have the ability to engineer an escape by eating a hole in the side of the pitcher itself.
Once they have fallen into the trap, this allows an easy escape route for any insects that subsequently fall into the pitcher.
This does not create the plant any real problems apart from the fact that any insects subsequently falling into the trap are able to escape via the exit made by the wasp. However what generally happens is that a large fly will tend to become trapped within the hole effectively sealing the escape route. Insects then continue to collect as usual within the pitcher.