From the Super Mario Wiki
Flaming Chomps appear in the levels Seesaw Scramble, Chomp Shark Chase, and Chomp Rock Challenge, all volcano-themed levels. They attack by flying out of a volcano in the background and falling down at a high speed while engulfed in flames. Flaming Chomps are invincible to any attack, except turning into Stars after touching a Middle Ring when one is nearby, and usually come downwards in set patterns. The spot where they land on is indicated by a harmless wall of flame that appears below them. Unlike their regular relatives, they never attack solid ground, and can only destroy breakable blocks. If a Yoshi touches one, he will catch fire and immediately lose a life.