It’s around that time of year. Whether it’s merciless mosquitos on a hot summer night, spiders in the attic, or an infestation requiring a visit from pest control, you may have seen more creepy crawlers than usual and thought—do these things every sleep?
The answer is yes—bugs are scientifically proven to take the occasional snooze. However, the way that they sleep is somewhat unusual compared to the human shut-eye routine.
When studying organisms so small, it can be difficult to tell whether they’re in true, deep REM sleep or simply “resting.”
Some bugs are nocturnal, depending on when their food is most readily available. For instance, cutworms eat their leaves at night to avoid predators, and bed bugs famously feed while their prey is sleeping. Bees, however, pollinate during the day while the flowers they seek are open sunward, so they sleep through the night.
Some bugs, like butterflies and moths, experience “torpor.” This state between sleep and hibernation occurs when an animal or insect’s psychological and metabolic activity decreases at a certain temperature. Some birds, marsupials, rodents, and even bats also experience torpor.
Bug sleep cycles vary based on factors like sex and age and are even influenced by caffeine and sleep-inducing drugs just like ours. Not all bugs sleep on the same cycle or at the same depth as the average mammal, but the habit of sleeping and its necessary functions remain the same.
Many species of bug have brains that require sleep to function, just like ours do. Rest is necessary for bugs to remain alert during their waking hours. The more sleep a bug gets, the longer it lives (which is why queen ants outlive their overworked subjects). Increased alertness helps bugs avoid predators and search for food with better precision.
Like most other organisms needing sleep, bugs have central nervous systems. Sleep is imperative to central nervous system maintenance. Critical pathways in the brain form during sleep, and your body won’t perform as well on a sleep deficit. The same is true for insects.
Perhaps you’ve been bothered by a bug (like a cockroach, fly, or spider) and noticed that it’s calmed down or disappeared. If you’re unsure if a bug has fallen asleep, there are signs you can look for (and these signs are strikingly similar to ones you’d see in your spouse or roommate).
If a bug has stopped moving or you’ve noticed its muscles relax, it might be asleep. It might also droop toward the floor or whatever surface it’s crawling on. The bug might also have an increased arousal threshold, meaning it’s harder to startle it into alertness. If you’ve ever had to wake someone from a deep sleep, you’ll know that an increased arousal threshold can make for quite the challenge.
How long bugs’ sleep cycles last depends on their species, as well as whether they’re a “queen” or “worker.” For instance, a “queen” fire ant gets around nine hours of continuous sleep, while her workers take short naps, adding up to just five hours. Meanwhile, fruit flies take shorter naps for just over 2.5 hours. Butterflies, moths, and other insects that experience torpor may remain dormant for the entire winter season, like bears in hibernation.
This may seem extreme, but keep in mind that human infants need to sleep for about 66.7% of the day, and even adults spend a third of their lives catching Zs. With this in mind, butterflies missing out on the most brutal season of the year doesn’t seem so unreasonable.
Just like a human would after a particularly rough week of work, some bugs need to catch up on their sleep after they’ve been deprived. This phenomenon, known as “sleep rebound,” is common in many species, also including rats and pigeons. (However, some bugs like bees don’t require a rebound but will instead sleep deeper for shorter periods.)
One study involving fruit flies showed that lack of sleep impaired their performance and vigilance. Another study showed that honeybees kept awake all night were less effective at communicating directions to fellow bees. The typical “waggle dance” used to signal the locations of nearby food sources was not as accurate in sleep-deprived bees.
Extreme sleep deprivation causes cellular damage in bugs like fruit flies, eventually killing them if left untreated. What’s strange about this phenomenon is that toxic molecules accumulate in the gut rather than the brain. Still mysterious to scientists, this process is actually reversible if the flies are fed antioxidants. However, for flies in the wild, days without sleep would mean certain death.
This is true of other animals as well. For mammals like dogs, sleep deprivation can be more lethal than starvation. Some animals, like bullfrogs, have lower arousal thresholds; some, like dolphins, can sleep with half of their brain at a time; and some, like sheep, nap in smaller bursts. But despite all these differences, scientists have yet to find a creature that doesn’t require some form of sleep to survive.
If you’ve seen a strangely sleepy bug recently or found yourself curious about insect biology, you might be wondering about the bugs’ sleeping habits. Bugs have a central nervous system, meaning they need sleep to maintain brain health and alertness for survival. But their sleep habits are not always similar to ours.
For instance, bugs have different circadian rhythms depending on when it is optimal for them to eat or work. As a result, they might sleep in short bursts or for a longer cycle. Some bugs even experience “torpor,” a dormant state activated at a certain temperature (similar to hibernating for the winter).
If bugs don’t sleep, they experience adverse effects and need to “catch up” just like we do. Bug sleep looks much like human sleep—a sleeping bug will be mostly motionless, relaxed, and difficult to stir. So the next time you see a strangely dormant bug or wonder where the butterflies have gone for the colder months, remember that they’ve probably just settled in for a nap.
Yes, bugs feel pain. Research has found that insects, particularly fruit flies, can experience chronic pain as well as sharp pain in short bursts.
Yes, insects can hear. Depending on the species, some insects (like grasshoppers) actually have incredibly powerful hearing abilities.
No, bugs don’t have blood–at least not like mammals do. Instead, insects have hemolymph, a fluid plasma vaguely similar to blood.