Facing impending death at the hands of the career tributes, Katniss (with Rue's help) knocks down a nest of Tracker Jackers from a tree; the swarm of Tracker Jackers attack the tributes and alter their minds with horrific images. Katniss gets stung herself, but with more of Rue's help, is able to flee the area and escape the careers. It's an incredibly tense and exciting scene that needs to be in the movie.
The Tracker Jackers are going to be difficult to explain without a few quick scenes or flashbacks that show the lab experiments that created the genetically-altered horrors, but we have faith that it will be included.
