• Metamorphosis: gradual (egg to nymph to adult).
  • Immature: looks like the adult.
  • Adult: sucking mouthparts, wingless, very small, head slender and pointed.


The sucking lice are ectoparasites of humans and other mammals. Some species vector diseases.

Classification and Groups

families and 70 species in North America.
About 500 species worldwide.

Medically Important Families:

  • Pediculidae: includes the human head and body louse (Pediculus humanus and Pediculus capitis)
  • Pthiridae: contains the human pubic louse or crab louse (Pthirus pubis).