Do ants sleep?

Do ants work all the time and do they ever sleep?

Ants do seem to work very hard, but they also rest and sleep. The reason why you think they are always working is because there are always ants working at every hour. All of the workers look the
same, so you think they are working 24 hours a day. --Ant and UMI

Some ants are sleeping like behavior have been observed: some workers of a colony laying around in a so-called sleeping position (Australian Carpenter Ants, Camponotus perthiana). When they are "awakened", they show a sluggishly moving. --E.O. Wilson