Ants secrete a milky fluid to feed their young in their own version of breastfeeding, new research has revealed.
The discovery was compared to the parental care mammals provide for their offspring after the fluid was found to play a vital role in colony survival.
The study also has important implications for our understanding of how insect societies evolved and are organised.
The researchers found that adult ants collect the milky fluid from pupae just before hatching when they secrete large amounts of the nutrient-rich substance, similar to mammalian milk.
Ant eggs hatch to form larvae, which pupate before emerging as adults, yet entomologists previously assumed that the pupae did not interact with the colony.
Indeed, the fluid is consumed directly by the adult ants or by the developing larvae, which are given the nutrient-rich substance by the adults.
Larvae that cannot access the secretion show stunted growth and poor survival, while pupae left to stagnate in their own secretions develop fungal infections and die.
Lead author Professor Daniel Kronauer, from Rockefeller University in New York, said: ‘The first few days after hatching, the larvae rely on fluid almost like a newborn baby relies on milk.
“Adults also drink it voraciously, and while it’s not clear what it does to adults, we’re confident it has an impact on metabolism and physiology.
“It probably evolved once, early in ant evolution, or even before ant evolution.”
The fluid contains hormones and psychoactive substances, and thus is thought to affect the behavior and physiology of colony members.
Fluid consumption affects the health of the entire colony
The health of the entire colony appears to depend on the rapid consumption of this nutrient-rich fluid.
In laboratory experiments, first author Dr. Orli Snir, removed ants in different stages of development from the colony to examine how social isolation affected the insects.
He noticed the fluid building up around the isolated pupae, and only when he manually removed it did they survive to adulthood.
Dye-tracing tests showed adults and larvae were drinking the milky substance, and analysis found that it results from a conserved process called moulting, in which all insects shed their old cuticle to grow.
While nonsocial insects recycle moulting fluid to conserve nutrients, ant pupae share it with their nest mates.
The fluid is rich in nutrients, psychoactive substances, hormones and some components present in royal jelly that honey bees reserve for the larvae of the queen bee.
While ants of all ages seem to enjoy fluid, young ant larvae need it as those deprived of fluid in their first four days of life fail to grow and many eventually die.
The professor. Kronauer said: “The way ants use this fluid creates a dependency between different stages of development.
“It just shows the extent to which ant colonies really operate as an integrated unit.”
The ant colony is sometimes referred to as a superorganism, a unified entity made up of many organisms working in concert.
Dr Snir said: ‘The pupal social fluid is the driving force behind a central and hitherto overlooked interaction network in ant societies.
“This reveals a new aspect of the dependence between larvae and pupae, and pupae and adults.”
He added: “This study provides only a glimpse into the intricate interaction networks of insect societies.
“Our long-term goal is to gain a deep understanding of the neural and molecular mechanisms that govern social organization and how these mechanisms have evolved.”