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Acorn's smallest residents

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My husband, Jack, studies ants and he often charms me with his inexhaustible supply of insect stories. On a recent stroll, we found a scattering of Gambel oak acorns littering the trail. Stooping down to pick one up, Jack told me the story of the "acorn ants."

These well-named Temnothorax ants — temno meaning slight — are so tiny that a colony of 200 of them can make their home in a single acorn! To my eyes, they are perhaps the cutest species of ant I’ve ever seen. 

Acorn ants are described as being extremely peaceful. They gather sugar that comes from the bodies of plant-sucking aphids, and collect small protein sources like springtails and flies. 

But Jack described a more complex picture. These little ants are too weak to be able to bust through the hard-outer core of the acorn shell, so they have to rely on the acorn weevil to provide a home for them. 

These half-inch-long brown weevils have long, slender snouts called rostrums. The females bore holes into young, summer acorns with the chewing mouthparts at the end of their rostrums. Then, the weevil does an about-face, and deposits her eggs right into the kernel of the acorn. The eggs hatch into pale, legless stubby grubs. 

The larvae live there until fall, when the acorns drop to the ground. Then it’s go time for the grubs! These little creatures bore through the acorn shell and out into the wide world of the forest floor, where they live for a year before emerging as a new adult weevil to repeat their own small circle of life.

And that leftover hollow in the acorn shell? Perfect for the next tenants — an active colony of Temnothorax ants.

This is what I love about trees. Whether you are observing them from the huge landscapes of our mountain forests or in the miniature arena of a single acorn, you’ll always find something to amaze you.

Dr. Nalini Nadkarni is an emeritus professor of both The Evergreen State College and the University of Utah, one of the world’s leading ecologists and a popular science communicator. Dr. Nadkarni’s research and public engagement work is supported by the National Geographic Society and the National Science Foundation. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation. @nalininadkarni
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