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Study finds ants secrete milky fluid to feed their young

"The first few days after hatching, larvae rely on the fluid almost like a newborn relies on milk."

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Close up of red leaf cutter ants focussed on stripping down the fresh greens on the plants in tropical Costa Rica
(Nature's Charm via Shutterstock)

By Mark Waghorn via SWNS

Ants secrete a milky fluid to feed their young - in a critter version of breastfeeding, according to new research.

Adults harvest it from pupae - to boost fitness of the colony. The phenomenon has been likened to the parental-care of mammals - including humans.

The study has important implications for our understanding of how insect societies evolved and are organized.

Lead author Professor Daniel Kronauer, of The Rockefeller University in New York, said:
"The way ants use this fluid creates a dependency between different developmental stages.

"It just shows to what extent ant colonies really operate as an integrated unit."

Ant eggs hatch to form larvae, which pupate before emerging as adults. Entomologists presumed the pupae do not interact with the colony.

Just before hatching, pupae secrete large amounts of a nutrient-rich substance, comparable to mammalian milk.

It is either consumed directly by adult ants or by the developing larvae, which are placed on the pupae by the adults. The behavior plays a vital role in colony survival.

via GIPHY

Larvae that cannot access the secretion exhibit stunted growth and poor survival, while pupae left to stagnate in their own secretions develop fungal infections and die.

The fluid also contains hormones and psychoactive substances, and so may influence the behavior and physiology of colony members.

The health of the entire colony appears to hinge on the prompt consumption of this nutrient-packed fluid.

First author Dr. Orli Snir said: "These interactions lie at the very heart of understanding insect societies but, because of the inherent challenges, they haven’t been investigated systematically."

In lab experiments, she removed ants at different developmental stages from the colony and examined how social isolation affected the insects.  

She noticed the fluid building up around isolated pupae. Only when Snir removed the fluid manually did the pupae survive into adulthood.

Dye tracing tests showed adults and larvae were drinking it. An analysis found the fluid is derived from a conserved process found in all insects called molting.

Insects shed their old cuticle to grow. While non-social insects recycle the molting fluid to conserve nutrients, ant pupae share it with their nestmates.

The fluid is rich in nutrients, psychoactive substances, hormones and some components found in the royal jelly that honeybees reserve for queen bee larvae.

And while ants of all ages seem to enjoy the fluid, young ant larvae need it. Those deprived of the fluid in their first four days of life fail to grow, and many eventually die.

Kronauer said: "The first few days after hatching, larvae rely on the fluid almost like a newborn relies on milk.

"The adults also drink it voraciously and, although it's not clear what it does to the adults, we're confident that it impacts metabolism and physiology.

"It probably evolved once, early in ant evolution, or even preceding ant evolution."

The ant colony is sometimes referred to as a superorganism - one unified entity composed of many organisms working in concert.

Snir said: "Pupal social fluid is the driving force behind a central and hitherto overlooked interaction network in ant societies.

"This reveals a new aspect of dependency between larvae and pupae, and pupae and adults."

She added: "This study only provides 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 governing social organization, and how these mechanisms evolved."

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