Tiny Toilets in Ant Colonies
A group of biologists have discovered that some ants set aside
areas for toilets within their colony.
The researchers at Universität Regensburg in Bavaria
studied Lasius niger ants, the common black garden ant found
across Europe and parts of the Americas and Asia.
They form colonies typically containing 4,000 to 7,000 workers.
Disease is a significant challenge for social animals with large colonies
in confined spaces, as they are especially vulnerable to contagion.
Refuse and fecal matter can be threats.
Many social insects have evolved elaborate procedures
for handling feces and other waste.
Some ants deposit waste material and feces in a special chamber
or in a pile outside the nest.
Scientists call such a pile a "kitchen midden" by analogy with waste
piles in human settlements.
Among the leaf-cutting ants, only the specialized refuse worker ants
enter the refuse chamber.
Yellow Rain: Honeybee Feces or Chemical Weaponry?
Some spider mites that live in social colonies create a fecal pile
just outside the entrance to their silk shelter.
Honey bees go on "defecation flights" to void their feces outside the hive.
Even very young bees which do not otherwise leave the nest do so for
Nest Etiquette — Where Ants Go When Nature Calls
uncovered a previously undescribed ant behavior.
Unlike other "kitchen midden" collection, these patches
contained nothing but fecal material — no uneaten
food or ant corpses.
They truly were ant toilets.
Insect feces are not necessarily harmful, and may have a beneficial role.
Beetle larvae use feces as a defensive shield.
Leaf-cutting ants use their feces as fertilizer for the fungus they farm.
Termites incorporate their feces as building and antimicrobial material.
How Did The Scientists Figure This Out?
The scientists established small colonies in plaster nests with multiple
chambers divided into grids.
They provided two sources of food, a colored sucrose solution and a
differently colored protein source.
Adult worker ants require little to no protein, and consuming protein
or just amino acids can be lethal.
After a while, colored patches appeared within the nests.
The patches were always the color of the sucrose solution.
What they describe as a "dark, mud-like substance" appeared in the center
of the more developed patches.
The fecal patches were mainly in the corners of the chambers.
The ants formed these patches in the corners even when there were many
unoccupied chambers in the nest.
Meanwhile, "kitchen midden" type refuse was piled outside the nests.
This included dead ants, debris, and pieces of the potentially lethal
However, Ant Feces Aren't Necessarily Dangerous
The scientists observed that the ants did not avoid the toilets.
They thought that it might be significant that feces were collected
in specific locations within the nest while dead nestmates are removed.
Maybe the ants use the collected feces as a source of salt or micronutrients.
It's possible that nutrients not used by adult ants and therefore accumulating
in the toilets would be beneficial to larvae.
Maybe the toilets are used as fungal gardens and therefore a source of food.
Ants do things humans wouldn't do, like wash their young in harsh acid.
Formic acid, H-CO-OH
European alchemists and naturalists had noticed that ant hills emitted
an acidic vapor at least as early as the 1400s.
The English naturalist John Ray had the nutty idea of distilling a
large number of ants in 1671.
He discovered HCOOH, a pungent colorless liquid.
We now call it formic acid because formica is the Latin word for "ant".
Ants secrete formic acid for both defensive and offensive purposes.
Continuing The Study
Black garden ants are a common choice for the casual ant farmer.
Maybe you can observe ants building toilets in your very own ant farm!
As for the Bavarian entomologists, they're nowhere near done studying this:
Many further questions await investigation, however:
are brood brought to, or kept from, the toilets?
Do the toilets form via stygmergic mechanisms?
Do the toilets have anti-microbial activities,
or act as a source of dangerous pathogens?
How widespread is this behaviour?
Our description of these ant toilets is a first step in understanding
these distinct nest structures.
Their formation, characteristics, and role are now subjects ripe for study.
You Can Flush But You Can't Hide