Do Ants Sleep? What Researchers Have Measured

Ant sleep looks nothing like ours, so for a long time it was easy to assume ants never rest. Researchers who filmed ants continuously found otherwise: sleeping ants take a distinct posture, fold their antennae and stop responding to nestmates. Below is what has actually been measured, how much it varies between species, why you still see ants on the move at night, and what that means for when baits work best.

What the fire ant sleep study measured

The study most people are quoting, usually without saying so, is by Deby Cassill and colleagues at the University of South Florida, published in the Journal of Insect Behavior in 2009. They took a polygyne (multiple queen) red imported fire ant colony collected in the Brazos Valley of Texas and placed 3 queens, 30 workers and 30 large larvae in a small glass topped chamber, then videotaped it continuously for 4.7 days.

How they told sleep from rest

The researchers did not simply count still ants. They described two inactive states in queens. In deep sleep, the antennae, mandibles and tongue were fully retracted and queens did not respond when workers touched them. In dozing, the antennae were partly extended and queens were more likely to react. During deep sleep the folded antennae often quivered, a pattern the authors called rapid antennal movement and compared, cautiously, with rapid eye movement sleep in vertebrates.

Queens sleep together

The three queens huddled with overlapping bodies when inactive, and their sleep and wake cycles were synchronised. The mechanism was touch: when one queen became active, the movement passed to the others, which the authors likened to a cue ball hitting billiard balls, and the queens moved apart.

Where workers sleep changes how long they sleep

Workers slept in one of three places: the middle of the chamber floor, hanging from the glass ceiling, or pressed against the wall. Ants in the busy centre, where most grooming and feeding happened, were disturbed more often. Mean sleep bouts were 32.8 seconds on the floor, 82.1 seconds on the ceiling and 108.7 seconds against the wall.

How far to trust the numbers

This is one carefully observed lab colony, not a survey of ants in general. Worker sleep was scored from one 24 hour period, and the colony lived at 27°C under a 14 hour light, 10 hour dark cycle. The 253 naps figure is real, but it describes 30 fire ant workers in a small chamber. Other species, and fire ants in a field nest of 80,000 workers, may differ. We have not found a comparable study repeating the measurements in other household ants.

Do queen ants sleep?

Yes, and more than workers. In the Cassill study, queens slept about 9.4 hours a day in about 92 episodes of roughly six minutes, nearly twice the workers’ total. The authors connect this to their reading of colony life: sterile workers are a caste of disposable, short lived helpers whose vigilance buffers the queen. That is a hypothesis about why the pattern exists, not proof that sleep explains why queens live longer. Fire ant workers live 30 to 180 days and queens two to six years, according to University of Florida entomologists; our article on how long ants live sets out the figures for other species.

Do ants ever stop working?

Individually, often. Colonies, almost never. Several studies have measured how much of an ant’s day is spent doing nothing obvious:

• Fire ants: about 20 per cent of workers were asleep at any given time (Cassill and colleagues, 2009).
• Carpenter ants: in a German study of Camponotus rufipes, foragers were inactive up to 50 per cent of their time and nurses about 30 per cent, measured over 1,656 hours of video (Mildner and Roces, 2017).
• Small acorn ants: University of Arizona researchers found that on average 40 per cent of workers in lab colonies of Temnothorax were mostly inactive, and showed that field colonies had the same time budgets as lab ones.

Those inactive ants are not wasted. In a 2017 follow up, the Arizona team removed the most active 20 per cent of workers, and within a week they were replaced mostly by previously inactive ants, which suggests idle workers act as a reserve labour force.

Do ants sleep at night?

Not in the human sense, and it depends on the species and the ant’s job.

Fire ants: no fixed night

In the fire ant study, activity episodes were unaffected by the light and dark periods, and the length of worker sleep bouts did not vary with time of day. The number of workers asleep did change: fewer were asleep between 6 AM and 2 PM than between 2 PM and 10 PM. When the team tested digging, workers excavated longer tunnels in the light, but time of day made no difference, which the authors read as ants reacting to local conditions rather than an internal clock.

Carpenter ants: a body clock that the colony overrides

Carpenter ants do have an internal clock. Mildner and Roces found that both foragers and nurses of Camponotus rufipes kept circadian rhythms when isolated in constant darkness, running slightly short of 24 hours (about 22.4 hours for foragers and 23.1 for nurses), and that activity was mostly nocturnal. Inside the colony things changed. Nurses worked around the clock with no daily pattern, apparently to meet the brood’s needs, and foragers shifted their activity to match when food was available, day or night.

In the US, extension entomologists describe carpenter ants the same way in practical terms. Rutgers calls them primarily nocturnal, and NC State says foraging is usually greater at night when the lights are off or the sun has set, though you may see them by day too.

Fire ants in summer heat

Temperature matters more than darkness for many species. Texas A&M AgriLife says fire ants forage when soil surface temperatures are between 70 and 90°F, and that during the summer they forage mostly at night to avoid the heat.

Do ants sleep standing up?

Fire ants do not lie down the way mammals do. In the Cassill study, sleeping workers stayed where they stopped: 53.8 per cent of sleepers were on the chamber floor, 27.3 per cent hanging from the glass ceiling and 18.9 per cent huddled against the wall. What marks sleep is posture, not position: the antennae fold in and the mandibles retract, and in deep sleep the ant ignores contact from nestmates.

Why you see ants on the move at night

Three things keep a trail going after dark. Staggered naps mean most workers are always awake. Some species, carpenter ants above all, forage mainly at night. And in summer, heat pushes daytime foragers such as fire ants into the evening. An ant trail on the kitchen counter at midnight is normal behaviour, not a sign of a bigger problem, although a steady night trail of large black ants is worth tracing because it may lead to a carpenter ant nest. Our ant identification guide helps tell which ant you have.

What sleep and activity mean for baiting

Baits only work when foragers find them and carry them home, so timing them to the ants’ active hours matters more than the time that suits you.

Two things undermine baits. Sprays and cleaners near bait placements can deter ants from feeding, according to the University of Kentucky. And wiping a trail with vinegar or soapy water removes the scent marks without touching the nest, which we cover in does vinegar kill ants. Carpenter ants in structural wood, or nests you cannot find, are a job for a licensed professional.

When ants are most active through the year

Our analysis of iNaturalist research grade records shows carpenter ant sightings peaking in May and June, at about 1.6 times their usual share of all records. Red imported fire ants, confined to the southern US, show their highest share in winter and early spring, partly because they remain visible through mild southern winters while insect records elsewhere collapse, so read their line as relative visibility rather than peak activity. These are outdoor sightings, not indoor activity.

Frequently asked questions

How long do ants sleep?

In the most detailed study, fire ant workers slept about 4.8 hours a day in roughly 253 naps of about a minute each, and queens about 9.4 hours in roughly 92 naps of about six minutes. That was one lab colony studied by the University of South Florida in 2009, so treat the figures as a well measured example, not a rule for every species. Other species, such as carpenter ants, show different daily patterns.

Why should you not squish ants?

Because the ants you see are a small part of the colony. University of Kentucky entomologists say thousands more ants and one or more queens stay hidden in the nest, and that spraying only visible ants usually fails. With about 80 per cent of fire ant workers awake at any moment, the trail refills quickly. Baits that foragers carry back to the nest reach the queen; squashing does not.

Do ants have feelings?

Nobody can measure feelings in an ant directly, and researchers avoid claiming them. What has been measured is behaviour that responds to the social world: ants have recognisable sleep states, carpenter ants change their daily rhythms to suit colony needs, and a 2015 study found that carpenter ant workers kept alone had a greatly reduced lifespan compared with workers kept in groups of ten.

What smells do ants absolutely hate?

There is little good evidence that any household smell keeps ants away for long. Ants follow invisible odour trails, so wiping a trail with a cleaner can break it for a while, but the colony is untouched and the ants usually return. The University of Kentucky warns that sprays and cleaning agents near baits can stop ants feeding on them, which works against control.

Sources

• Cassill, Brown, Swick and Yanev, Polyphasic wake/sleep episodes in the fire ant, Solenopsis invicta, Journal of Insect Behavior 22, 313 to 323, 2009.
• Mildner and Roces, Plasticity of daily behavioral rhythms in foragers and nurses of the ant Camponotus rufipes: influence of social context and feeding times, PLoS ONE 12(1): e0169244, 2017.
• Charbonneau, Hillis and Dornhaus, “Lazy” in nature: ant colony time budgets show high “inactivity” in the field as well as in the lab, Insectes Sociaux 62, 2015.
• Charbonneau, Sasaki and Dornhaus, PLoS ONE 2017, as described by the University of Arizona.
• Koto, Mersch, Hollis and Keller, Social isolation causes mortality by disrupting energy homeostasis in ants, Behavioral Ecology and Sociobiology 69, 2015.
• Merchant, Texas AgriLife Extension L-5070, the Two-Step Method for fire ant control.
• University of Florida IFAS Featured Creatures EENY-195, Red Imported Fire Ant, Collins and Scheffrahn.
• Rutgers Cooperative Extension FS1101, Carpenter Ants and Their Control, 2019.
• NC State Extension, Biology and Control of Carpenter Ants, Crawley and Hayes, reviewed 2023.
• Utah State University Extension, Odorous House Ants, Davis and Taylor, 2019.
• University of Kentucky Entomology ENTFACT-619, Ant Control for Householders, Potter.
• The Pest Control Brief analysis of iNaturalist research grade records, pulled October 2026.