Quirks & Quarks

Ants share vomit to feed each other and communicate within the colony

Ants vomit into each other's mouths as a way of establishing and maintaining social connections, as well as passing along nutrients — not unlike milk from mammals.

The regurgitated material includes nutrients, but also chemical signals

These carpenter ants aren't kissing, one is vomiting into the mouth of the other. (Submitted by Adria LeBoeuf)

Feeding through regurgitation is called trophallaxis and is known in many animals, including many species of ant. But in ants this phenomenon seems to also serve an important role in organizing the colony.

Like a lot of other insects, ants have a foregut, midgut and hindgut. The midgut and hindgut are for digested food. The foregut is known as the "social gut" because this is where material is stored before it is vomited into another ant's mouth. 

According to a new study by Adria LeBoeuf, an assistant professor of biology at the University of Fribourg in Switzerland, this behaviour has a few functions, but a major one is to create what is called a "social circulatory system" for the colony.

Ants form 'social circulatory systems' through the exchange of nutrients, proteins and hormones in their vomit. (Submitted by Adria LeBoeuf)

The colony that vomits together...

Her work suggests trophallaxis in ants helps keep the members of the colony connected. She found that beyond nutrients, ants are passing along proteins, hormones, and fragments of genetic material — RNA. 

In colonies the exchange of vomit can be seen happening 20 times in a minute. The vomit is usually a clear liquid. 

Welcome to the world of trophallaxis (Cell Press)

The role an individual ant plays in the colony can be determined by the contents of its social stomach, in particular the proteins it carries. For example, nurse ants that care for the young generally were found to have higher amounts of anti-aging proteins than others. LeBoeuf suggested this may be a way that ensures that they survive to care for future generations. 

Produced and written by Mark Crawley