Farmers in my Forest

Carpenter ant checks out a spindle gall

The aphid looked like a kid that wants to be called on in a classroom.

But instead of hands, the creature’s rear legs were waving for attention. And in less than a minute, he got it—from an ant. The ant reached for the aphid. Then a glistening drop of honeydew—liquid poop—emerged from the aphid’s posterior.

And the ant…

…ate the poop. I knew about ants ‘farming’ aphids for honeydew, but I’d never seen it live in my own backyard. Last weekend I was weeding and trimming when I saw not just aphids, but also scale insects on a few trees and shrubs. At first, I didn’t give the leaf-sucking insects much thought because their numbers were minor, and I saw no threat to the greenery. But when I saw ants crawling through the same branches, I realized what might be happening. So I took a closer look.

Carpenter ant harvests honeydew from a scale insect
Carpenter ant harvests honeydew from a scale insect

If you haven’t heard of their mutualistic relationships, ants and honeydew-producing insects help each other out. The insects suck sap from leaves in such large quantity that they excrete a sweet liquid. Ants have sweet tooths and not only do they lap up the other insects’ poop, they protect them from predators to ensure the supply. Not all ants do this. But my closer look revealed these were indeed the ‘dairy farmers’ I’d read about. Carpenter ants were in one tree milking scale insects. On another tree, it was smaller ants (I can’t tell the species) harvesting honeydew from aphids.

I watched for a long while, capturing video, until the sight was becoming mundane. Then I noticed that one funny aphid was waving its back legs. Here’s the part when the ant responds. (Keep your eyes peeled. I’ve inserted some arrows, but the honeydew drop is small.) Did you notice ants’ antennae stroking aphids’ backs? That’s how the ants say, ‘poop, please.’ When an aphid’s loaded, it responds. I never read of an aphid advertising to an ant, however. Usually they just ‘go’ when they need too—hence the honeydew drops dappling our truck’s windshield when it was parked under some aphid-infested foliage. So, my waves-for-attention aphid probably wasn’t really asking for an ant to stop by. Was he just doing handstands, maybe? And perhaps you noticed another aphid released a honeydew pearl just before the last ant left the scene. The ant had stroked its back but didn’t stay for the sweet reward.  Waste not, want not, Ant!

In the photo at the top of this post, you see spindle galls on the leaves, caused by microscopic mites laying eggs. The leaf responds by growing tissue that protects the hatchling mite as it develops. The carpenter ants poked around the galls when they weren’t stroking scale insects. So I wonder if these particular galls produce honeydew—I’m aware that some do. More to learn about!

Finally, I saw a different kind of entertaining aphid behavior. Take a look.  Do you suppose those aphids were playing follow the leader? Or maybe this was some kind of a stadium wave.

Image Credits: Carol Doeringer.

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