Mating frenzies, sperm hoards, and brood raids: the life of a fire ant queen – Walter R. Tschinkel


It’s June, just after a heavy rainfall, and the sky is filling with creatures
we wouldn’t normally expect to find there. At first glance,
this might be a disturbing sight. But for the lucky males and females
of Solenopsis invicta, otherwise known as fire ants,
it’s a day of romance. This is the nuptial flight, when thousands of reproduction-capable
male and female ants, called alates,
take wing for the first and last time. But even for successful males
who manage to avoid winged predators, this mating frenzy will prove lethal. And for a successfully mated female,
her work is only beginning. Having secured a lifetime supply of sperm
from her departed mate, our new queen must now single-handedly
start an entire colony. Descending to the ground, she searches for a suitable spot
to build her nest. Ideally, she can find somewhere
with loose, easy-to-dig soil— like farmland
already disturbed by human activity. Once she finds the perfect spot,
she breaks off her wings— creating the stubs
that establish her royal status. Then, she starts digging
a descending tunnel ending in a chamber. Here the queen begins laying her eggs,
about ten per day, and the first larvae hatch within a week. Over the next three weeks, the new queen relies on a separate batch
of unfertilized eggs to nourish both herself and her brood, losing half her body weight
in the process. Thankfully, after about 20 days, these larvae grow
into the first generation of workers, ready to forage for food
and sustain their shrunken queen. Her daughters
will have to work quickly though— returning their mother
to good health is urgent. In the surrounding area, dozens of neighboring queens
are building their own ant armies. These colonies
have peacefully coexisted so far, but once workers appear, a phenomenon known as brood-raiding
begins. Workers from nests
up to several meters away begin to steal offspring
from our queen. Our colony retaliates, but new waves of raiders
from even further away overwhelm the workers. Within hours, the raiders have taken
our queen’s entire brood supply to the largest nearby nest— and the queen’s surviving daughters
abandon her. Chasing her last chance of survival, the queen follows the raiding trail
to the winning nest. She fends off other losing queens
and the defending nest’s workers, fighting her way
to the top of the brood pile. Her daughters help their mother succeed
where other queens fail— defeating the reigning monarch,
and usurping the brood pile. Eventually,
all the remaining challengers fail, until only one queen—
and one brood pile— remains. Now presiding over several hundred workers
in the neighborhood’s largest nest, our victorious queen begins
aiding her colony in its primary goal: reproduction. For the next several years,
the colony only produces sterile workers. But once their population
exceeds about 23,000, it changes course. From now on, every spring, the colony will produce
fertile alate males and females. The colony spawns these larger ants
throughout the early summer, and returns to worker production
in the fall. After heavy rainfalls,
these alates take to the skies, and spread their queen’s genes
up to a couple hundred meters downwind. But to contribute
to this annual mating frenzy, the colony must continue to thrive
as one massive super-organism. Every day, younger ants feed the queen
and tend to the brood, while older workers
forage for food and defend the nest. When intruders strike, these older warriors fend them off
using poisonous venom. After rainfalls,
the colony comes together, using the wet dirt to expand their nest. And when a disastrous flood
drowns their home, the sisters band together
into a massive living raft— carrying their queen to safety. But no matter how resilient, the life of a colony must come to an end. After about 8 years,
our queen runs out of sperm and can no longer replace dying workers. The nest’s population dwindles,
and eventually, they’re taken over
by a neighboring colony. Our queen’s reign is over,
but her genetic legacy lives on.

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