Scientists believe that a spider may be sleeping when its legs are tucked under its body, as in hibernation. There is very little research on the subject of spider sleeping habits. Spiders have a circadian rhythm of activity and rest.
When spiders are sleeping, they prefer their webs or small cracks and crevices for protection. Researchers did a study on the effects of drugs and web-making ability. Drugs cause some spiders to pass out, while other spiders simply make really strange webs. Some spiders also lose consciousness as they are mating, although this is not considered to be the same thing as sleeping.