1. Lice with head wider than thorax and chewing mouth parts. Anterior part of head is triangular .......... Felicola subrostratus
2. Lice with head narrower than thorax and piercing mouth parts .......... Go to: 3 & 4

3. Thorax distictly separate from the abdomen. All tarsal claws are equal. .......... Pediculus humanus
Note: While this louse only lives and reproduces on humans, the cat owner may bring in a specimen and ask if it was acquire from the cat.
4. Thorax NOT distict from the abdomen. All tarsal claws not equal. Abdomen with large tubricles. .......... Pthirus pubis
Note: While this louse only lives and reproduces on humans, the cat owner may bring in a specimen and ask if it was acquire from the cat.