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Photo Gallery - Planting the forest understory
Beyond their refined appearance and wide-ranging nesting
habits, winnow ants have two qualities that set them apart from
the rest of the ants: the helping hand they give forest plants and
their ability to use tools.
First, let me tell you about their agricultural talents, and the
reason we call them winnow ants. Winnow ants have a special
relationship with forest plants. We all know that many plants make
seeds. Some plants produce seeds with a special coating called
an elaiosome that’s a lot like the hard candy coating on the
outside of an M&M. Like the tasty candy shell, the elaiosome coat
has a special blend of flavors that is irresistible to winnow ants.
As they pick across the forest floor in search of food, winnow ants
often stumble across these seeds. When winnow ants get a whiff
of that elaiosome, they can’t help themselves: They have to pick
up the seed and carry it back to their nests. Once in the nest,
winnow ants feed the outer coating of the seed to their young.
Unlike most of us, who prefer the chocolaty center of M&Ms,
winnow ants eat only the elaiosome and leave the seed inside
alone. When wheat farmers shuck wheat seeds from their husks,
it’s called winnowing. Likewise, winnow ants remove husks from
forest seeds. After the seed has been shucked of its elaiosome,
the ants don’t need it anymore, so they take it back out of their
nest and deposit it on the forest floor. There, the seed, no worse
Two Aphaenogaster foragers are attracted to the ripe elaiosomes of
some fallen bloodroot seeds. - © Alex Wild
for the wear, is free to sprout and grow into a happy forest herb.
Having their elaiosome nibbled away by hungry ant babies does
not hurt the seeds; in fact, it helps them. When ants pick up these
seeds, they protect them from animals that eat the whole seed,
and winnow ants plant seeds far away from the seeds’ parents.
This way, the newly planted seeds don’t crowd their parents as
they grow.
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