The pulvillus is a sort of ball located at the end of the legs of some insects, on the last segment of the tarsus. Pulvilli are always found in pairs.
These elements consist of many adhesive silks that allow the insect to move on smooth surfaces as well as on vertical walls.
Sometimes, pulvilli are used to cushion falls, especially by grasshoppers..
The two brown sacks on the end of the limbs of this fly are the pulvilli, which allow the fly to walk on the walls. © Max xx CC by-nc-sa 2.0