Today’s trivia is about Ants, and in particular their sleep patterns.
Firstly we can confirm that Ants do sleep and exhibit demonstrable sleep behaviours.
We will dig further into the subterranean life of these invertebrates to understand more about their sleep patterns.
There is only a handful of research papers on sleep in Ants. (Bees are considerably more researched). The paper we are most interested in is this one:
Polyphasic Wake-Sleep Episodes in the Fire Ant Solenopsis Invicta
The research paper covers a particular species, Solenopsis Invicta famous for its stinging ability.
Sleep in Insects
Sleep in insects is particularly interesting because insects have quite different physiology. Another problem is how to actually determine sleep in insects:
Homeostasis: The balance between sleep and awake periods, sleep deprived flies are more sleepy during the day
Alertness: Insects which are sleeping are slow to respond to external stimulus
Circadian Rhythm: Insects that live above ground are likely to have periods of increased activity and periods of rest in line with a daily cycle, insects which live underground are generally polyphasic with no discernable circadian rhythm
Getting an Ant colony
How does one acquire an ant colony to study sleep patterns? Ant hives are constructed entirely underground with only thermal venting sections placed above ground.
In fire ants, the drip floatation method takes advantage of a flood-survival adaptation of the ants to accomplish this task. The key principle is that ants are so small and light that they are naturally buoyant. They also have a waxy coating which helps repel water and allows the entire colony to stay afloat when they cling together. Combined with their ability to self organise they can effectively float an entire colony on water.
- Dig up an ant colony and place it in a large bucket
- After 24 hours the ants will reestablish the structure of the colony with brood in chambers and tunnels to the surface excavated
- Talc powder is used on the sides of the container to prevent the ants climbing the sides.
- Water is dripped slowly into the bucket
- After 4-8 hours the water level rises slowly enough the the colony has gathered on the surface, brood and queens included
- Eventually the colony will form a raft, floating on the surface which can then be transferred to an artificial nest.
Sleep Patterns
Key observation about the sleep behavior as anticipated is that because they are a subterranean species they are not affected by day/night cycles, rather sleep patterns are determined by activity in the hive.
Workers
- Average 253 sleeps per day
- Each sleep about 1 minute
- Total 4.8 hours of sleeping a day
Workers tend to sleep in one of three locations, the chamber floor, ceiling or side of chamber. Those that sleep on the chamber floor were most likely to be woken by other workers passing by. Seemingly the best place to sleep was the side of the chamber.
Queens
- Average of 92 sleeps per day
- Each sleep about 6 minutes
- Total 9.6 hours of sleeping per day
Queens exhibited two observable sleep patterns:
Dozing: antenna extended, stationary, likely to be woken by contact from a worker.
Deep sleep: antenna tucked in close, stationary, unresponsive to external stimulus. Prone to random antenna movement during deep sleep.
Delightfully the queens would synchronise their sleep patterns so that they all would sleep at the same time, and woke up at the same time. They did this by huddling together when they slept, like hounds. When one started to stir the others would wake up as well.
Conclusion
The net result of this experiment found that at any given time there was on average 80% of the work force available to work on grooming, feeding or excavating sand. Queens in this species can live for 6 years, workers only one month.
The hive is always busy (hyper active) at attending to the needs of the Queens and buffering them from environmental effects which might be detrimental. This allows the queens to maintain a high reproductive efficiency and extend their longevity.
References
Video of a sleeping Bee
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