From the Super Mario Wiki
A Bzzap! is a bee enemy found in Flower Fields in the game Paper Mario. This enemy attacks by stinging its enemies. A Bzzap!'s sting sometimes poisons Mario. They usually hide in the trees; when Mario whacks the tree with his Hammer, the Bzzap! escapes and attempts to sting Mario as a First Strike.
Bzzap!s also appear at the end of Forever Forest in a beehive. Near the beehive is an HP Plus Badge. They are off the forest's main path in a second exit. By hitting the tree they are hanging on, Mario can coax the Bzzap!s out of hiding.