Anting is a maintenance behavior during which birds rub insects, usually ants, on their feathers and skin. The bird may pick up the insects in its bill and rub them on the body (active anting), or the bird may lie in an area of high density of the insects and perform dust bathing-like movements (passive anting). The insects secrete liquids containing chemicals such as formic acid, which can act as an insecticide, miticide, fungicide, or bactericide. Alternatively, anting could make the insects edible by removing the distasteful acid, or, possibly supplement the bird's own preen oil. Instead of ants, birds can also use millipedes. More than 200 species of bird are known to ant. A possibly related behaviour, self-anointing, is seen in many mammals.