Do Insects Sleep
Insects live short lives. They don't worry about passing tests or paying mortgages. They may be different from humans in so many ways, but one thing we have in common is sleep.
It seldom crosses our minds, but interestingly, most insects do spend periods resting. Some insects rest during the day, while others rest at night. It depends on the insect: what they eat, what likes to eat them, whether they are nocturnal or diurnal. Dragonflies, for instance, rest at night. Their metabolism slows down. They become sluggish, and they are somewhat oblivious to what is going on around them. This is known as a state of torpor, which differs from sleep because the insect is still aware of its surroundings,
but doesn't respond as quickly to stimuli as it would if it were totally awake.
Ants, termites, flies, beetles, bees, and cockroaches all go through a period everyday when they appear to be resting. Certain bees attach themselves to the ends of plant leaves and stay like that for hours at night, not moving. Some wasps will similarly leave their nests and rest at night.
The New Zealand weta, a large cricket-like insect, is unusual because every night when its mountain habitat reaches freezing temperatures, the weta freezes, and then thaws out in the morning. Ladybugs use hibernation, also known as diapause, to survive the winter months. Bedbugs can also lower their metabolic rate so they use less energy and can survive long periods without food.
Some desert dwelling insects lower their metabolic rate during times of drought. This is not considered sleep because insects don't have higher brain function like humans and mammals. They can't dream, for example. However, since insects don't have eyelids, how can we tell if they are simply resting, or if they closer to what we would consider sleep?
A recent University of Pennsylvania study monitored the adenosine levels in the brains of fruit flies, a chemical the human body produces, as well. The researchers observed that the fruit flies would spend about seven hours every night in a restful position with their head down, they would not move, and they would be difficult to arouse by tapping on their glass container. If the fruit flies were not allowed to “sleep” during the night, then they would try to make up for the slack of rest by resting more later, making up for sleep deprivation much the same way humans do. The chemical adenosine builds up in human brains during times of activity and then decreases when we are sleeping. Caffeine interrupts the intake of adenosine causing us, and fruit flies, to be more alert. In the study, fruit flies were more alert when given doses of caffeine and went to “sleep” when given adenosine.
Maybe inducing sleep will become the newest pest control tool, or at least it's something interesting to think about before drifting off to dreamland.
20 Aug 2009, 07:56
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