Phthiraptera - (lice)
This order includes wingless and ectoparasitic insects like the human louse. They parasitise mammals or bird and are often blood sucking. Others live on hairs or skin parts.
The order contains around 3500 species, typically between 1 and 5 mm long. Their body is flat and the legs are suitable for holding on to their hosts. They move to a new host during close contact.
For details see the respective page in Wikipedia.
The following families are currently included under Phthiraptera: