Many people are surprised to learn that ants sleep. Even more surprising is the evidence that suggests they may dream (RAE is a sleep state found in ants and bees characterized by Rapid Antennae Movements and possibly similar to the REM sleep in mammals)
Ants sleep frequently and in funny locations. Generally they will rest their thorax and gaster on the ground, fold their antennae and be very still. They nap for 10min up to an hour. Queen ants will sleep for up to 4 hours at a time.