The soldiers develop to defend the colony against ant attack. They have enormous heads and sometimes have jaws that are so large, they can’t eat, and must be fed by workers. They defend the colony by blocking the narrow tunnels with their gigantic heads, and basically take punishment from ants trying to get down the tunnel. They bite randomly because they can’t see. Can you imagine defending the colony with your face? It gets ripped apart by ants and then another soldier termite steps into the tunnel when the one in front of it falls.

This is from the termite wikipedia article:

“In cases where the intrusion is coming from a breach that is larger than the soldier’s head, defense requires special formations where soldiers form a phalanx-like formation around the breach blindly biting at intruders or shooting toxic glue from the nasus. This formation involves self sacrifice because once the breach is repaired during fighting by the workers no return is provided causing the death of all the defenders.”

Kind of a noble insect… Termites have a lot of other unusual characteristics, like a highly social nature, a queen and a king (where the queen can grow up to being a few centimeters until it’s immobile) and tall colony mounds that are meters high above the ground. They’re one of the few organisms (the only?) that can digest raw cellulose (wood) from a plant, because they have microbes living in their stomach that breaks it down for them.