A study that was investigating how most animals can tell what time of day it is even if the animal cannot see the Sun or the Moon has found that flies can tell what time of day it is. A fly’s concept of time is not as complex as that of humans but the similarity of fly brain chemistry to mammals may hold a clue to how animals know what time it is.
Two groups of flies were trained to associate the time of day with an odor. One group was trained to associate the morning with the smell of sugar (sucrose) while the other was programmed to associate the afternoon with the smell of sugar. The two groups were trained to associate the smell of menthol with the opposite time of day that they smelled sugar. The training lasted for two days.
The scientists tested the fly’s sense of time. The flies retained their memory of time for an infinite period of time as long as the two different odors were separated by four hours or more. The flies could tell the difference in the time of day even in total darkness. The flies lost their ability to “tell time” in a situation that involved 24 hours of light. Flies that were genetically altered to lose the time keeping genes that control the circadian rhythm could not tell time at all.
This is the first known instance of an insect being trained to be able to tell the time of day. The chemical functions that allow flies to tell time have yet to be unraveled. The researchers seem certain that there is some gene sequence that is common to flies and all animals that have a sense of the time of day including man.
