While head lice or Pediculus humanus capitis compromise the most prominent insect species, two other types also infest humans. Pubic lice, Phthirus pubis, informally called "crabs," are most frequently spread by sexual contact, bedding and shared linen. Body lice, or Oeducykys gynabys ciroirusm sometimes disparaged as "cooties," are uncommon in the U.S. but are capable of transmitting typhus epidemic relapsing fever.