When Hugo Deans pointed out some seed-like objects near an ant nest, his father, Andrew, recognised them as oak galls – plant growths triggered by insects.
“I was surprised that ants would collect galls,” says Hugo, now age 10, “because why would they do that?”
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When certain wasps lay eggs in an oak leaf, the tree surrounds them with hard-cased galls, protecting the leaf and sheltering the wasp larvae.
Some flowering plants also make edible growths that ants relish, and through eating them, the insects help to disperse seeds.
Now all three things have been linked by Andrew Deans and fellow entomologists at Pennsylvania State University and their findings have been published in The American Naturalist.
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Upshot is that a gall wasp stimulates an oak tree to make a gall, but with a cap that ants love to eat.
The galls drop, are harvested by ants and taken to their nest, where the wasp larvae may get extra protection.
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The researchers call it a “mind-blowing” set of interactions, never before noticed until Hugo watched his backyard ants.
Main image: an Aphaenogaster ant holds an oak gall containing wasp larvae. Researchers discovered an elaborate relationship among ants, wasps and oak trees. © Andrew Deans/Penn State