Lice are tiny parasitic bugs that feed on the skin debris and blood of their host. For dogs, there are three species of lice that commonly pester your pet: Linognathus setosus, a blood-sucking louse Trichodectes canis, a louse that bites and feeds on skin debris Heterodoxus spiniger, a biting louse that feeds on blood Female lice will lay their eggs, commonly called “nits,” close to the skin. Because of this, these bugs can linger for weeks, even months on your dog. Nits are incredibly difficult to dislodge, and it takes about 3 – 4 weeks for them to become adult lice and continue the reproduction process. Once they’re adults, they cling onto individual hairs on your dog at the base of the shaft.