Flies spend their days buzzing around with friends and they get pretty tired out by the end of the day. At nightfall, they find a place to land and sleep for the night. Their favourite places include twigs, branches, tree trunks and fences in the garden. Indoors, a fly might rest on a ceiling or on a window. Flies are so good at gripping things that they can also sleep upside down if they need to. They’ve been known to settle down on curtains, walls and even bath stalls.
While it may come as a surprise to many, flies do in fact need sleep and they often take short naps during the daytime as well. Just like humans and most other living creatures, flies require sleep in order to function properly.
Flies have very small brains and their needs for sleep are relatively modest, but they do need to be able to respond to their surroundings so they can avoid threats. In experiments, flies that have their sleep disrupted die much earlier than a control group that gets enough sleep.
Previous research in mammals has shown that different phases of mammalian sleep can be identified by changes in the electrical activity of neurons. While a complete study of sleep in flies has yet to be performed, there are indications that fruit flies undergo similar changes. However, the thalamocortical system that distinguishes the different phases of mammalian sleep is not present in flies so REM and other sleep-related EEG events are probably not occurring in flies.