All Winter, These Ants Make the Ultimate Sweet Sacrifice to Their Colony
06.12.2023 - 23:13
/ atlasobscura.com
Prepping for winter requires serious effort. By the time autumn falls brisk and wet, tree squirrels are already hard at work hoarding and hiding the nuts and seeds they’ll need to sustain themselves through the coldest months. Moles are busying themselves capturing and immobilizing earthworms in underground dungeons. And acorn woodpeckers are drilling and storing up to 50,000 acorns in the dead limbs of “granary trees.”
But while many creatures build some version of a food pantry that will keep them fed through the harsh wintertime, only honeypot ants store their food in living, breathing vessels. When frigid temperatures lead to scarcity above ground, a select group of the ants, abdomens swollen from a season of consuming nectar, keep the colony fed with their vomit.
Around 1,000 ants out of 5,000 in a honeypot colony are conscripted into the sacrificial profession. Like grotesque storage containers, these “repletes” hang largely immobile from specially constructed chambers, explains John Conway, biology professor emeritus at the University of Scranton, who studied Myrmecocystus colonies endemic to desert-like regions of the American Southwest and Mexico. When the cache of rich liquid in their abdomens comes to an end, so do their lives.
Many honeypot ants are filled with the nectar collected from flowering plants and the “honeydew” secreted by aphids, but they aren’t the only fluids contained in the valve-controlled digestive tract of a replete. “Most are a golden to dark golden color, but there are a few of them that are also milky in color, and some ants are clear,” says Conway. “Some of them, we think, store water, and some may store dead insects brought into the nest.” Together, the repletes form a complete nutritional smorgasbord.
The repletes in North American honeypot ant nests aren’t born that way. Entomologists believe that they hatch as worker ants then self-sort sometime later. While the largest worker ants tend to be those that later develop the swollen abdomens, small workers can also make the transformation—though researchers aren’t exactly sure why. No one, says Conway, has yet been able to prove whether there’s “some kind of anatomical peculiarity” that predisposes some ants to the role while leaving others to live as workers.
Whatever the reason, the phenomenon appears to cross species and continents. Ants belonging to entirely different genera—six of them across the world, including in Africa and Australia—appear to researchers to have almost identical physical and behavioral traits. Each group has a population of swollen repletes that regurgitates to feed the nest at times of food scarcity.
“It’s a perfect example of what we call convergent evolution, the formation of the same