Which insect can grow larger than a mouse and has mandibles strong enough to snap a pencil in half?

That would be the titan beetle (Titanus giganteus)! Growing up to 6.5 in (16.5 cm) long, this enormous insect can be found in tropical rainforests in parts of South America.

Experts think this critter is about as big as a beetle can get. Why? In insects, the oxygen to keep cells alive isn’t forcefully delivered by lungs and heart. Instead, it seeps through the body largely by diffusion.

That passive method means not enough oxygen could get to the inside of a truly gigantic beetle.