How many setae are located on each segment of an earthworm?

Except for the first and last segments, which have no setae, there are eight tiny bristle-like structures that can not be seen with the naked eye called setae on each segment of an earthworm. The arrangement of the setae is one factor that helps in the identification of earthworms, as they can be closely or widely paired in four pairs or separate. Setae grip the soil to help the earthworm move about and sense the enviroment.