In addition to the butterfly and T-Rex, the representatives of pre-historic time, there are other symbols in "A Sound of Thunder":

• The Time Machine

One of man's inventions, the time machine interferes with the universe by turning time back so that people can act out their fantasies. This machine creates a tenuous situation, one that must be carefully managed; for one small error can cause massive complications.

• The Metal Path

The Path is the walkway that is suspended six inches above the real ground with its flora and fauna.  The time-travelers  assiduously remain on the path at all times, lest they interfere with the ages that follow the one into which they travel.

• Lesperance

With a name that resembles the French word for hope, Lesperance is the man who arranges the time travel trips.  For, he coordinates the time of creatures' deaths and marks them with a red paint ball.  Checking his watch and exhibiting other nervousness, Lesperance cautions the tourist/hunters "Stay on the Path. Stay on the Path!"  Always he seems to be hoping that nothing will go wrong.  When Eckels becomes afraid at the sight of the "Tyrant Lizard," Lesperance tells him "Don't run...Turn around.  Hide in the Machine."

Fortunately, the dinosaur is shot in time so that Time is not upset:

"There."  Lesperance checked his watch. "Right on time.  That's the giant tree that was scheduled to fall and kill this animal originally."

He hopes that is all there is to the trip. But, of course, it is not.