Swarm's body is completely covered in bees and as such is technically intangible as he can have his bees separate.
Swarm's origins different depending on continuity: in some he's a NAZI scientist named Fritz von Meyer who was devoured by the bees, and another says he's the creation of bees being in contact with an alien energy. In the Ultimate comics Swarm is a female mutant who can control insects, and many other versions.