Sheep body lice (Bovicola ovis) are small insects, generally less than 2 mm in length with a broad reddish head and a pale body. Adult lice have brown stripes across the body but these are absent in the younger stages. They feed on scurf, wool wax, superficial skin cells and bacteria and cause most of their economic effects by irritating sheep and causing them to rub and bite at their fleece. All stages live on sheep and most lice die within a week when separated from their host.

Spread between sheep occurs almost exclusively by sheep to sheep contact. If lice can be eradicated from a flock and other lousy sheep excluded, the flock will remain lice-free in all but extremely rare instances.

Two other species of lice are also sometimes found on sheep. These are blood feeding lice, larger than the common sheep louse, often appearing bluish in colour and generally found on the legs or face of sheep, or sometimes on the scrotum of rams. These species are of little economic importance.

More detailed information on biology is found in Biology of sheep lice.