Defense or Revenge or Both?

Event Reminders:

July 9 field day at the Platte River Prairies. Details here.

Conserving Fragmented Prairies workshop July 25-26. Deadline for registration is July 1 (Friday).

I’m at The Nature Conservancy’s Niobrara Valley Preserve this week. Yesterday morning, I went for a sunrise walk in the prairie. I wasn’t looking for anything in particular to photograph, which almost always leads to fun discoveries.

As the sun rose, I walked toward it and spotted a few adult antlions making short flights in front of me. After a few unsuccessful tries, I found one that let me creep into photo range and captured a few nice images of it backlit against the morning light. For the next few minutes, I found and photographed grasshoppers, bees, and milkweed beetles.

Adult antlion. This creature somewhat resembles a damselfly but has a longer and heavier body and more club-shaped antennae. And a different head shape with smaller eyes, but that’s harder to see from a distance…

My next discovery was a group of ants tending to aphids on the flower head of fourpoint evening primrose (Oenothera rhombipetala). Ants often ‘adopt’ groups of aphids like this, protecting them from predators and harvesting the sweet droplets of honeydew the aphids excrete from their hind ends. I took a few photos and then looked a couple other primrose flowers/buds nearby and was surprised to see ants and aphids on all of them. That’s when the morning suddenly got much more interesting.

Ants tending aphids on fourpoint evening primrose.

As I was looking at some primrose flowers that had just opened up and watching the ants move around their aphid ‘flock’, an antlion flew in to the flower, presumably looking for nectar and/or pollen. It landed on the lip of the flower and scrambled briefly for a foothold.

Antlion landing on the flower to feed.

As soon as it hit the flower, though, it immediately attracted the attention of the ants working with the aphids. Those ants, lightning-quick, swarmed the antlion and attacked it from multiple directions. It was brutal and difficult to watch. The antlion futilely tried to use its legs to dislodge ants but it didn’t stand a chance.

Antlion being swarmed and attacked by ants.

My assumption is that the ants were defending their aphids from danger. Antlion adults feed on nectar and pollen, but at least some are also predators. It makes sense that ants would see this antlion as a threat to the aphids, though I wonder if they knew what it was or just responded to the sudden incursion. Maybe they would have attacked any other creature making a similar approach.

I know it didn’t happen this way, but I also like to imagine the ants might have recognized the antlion as the adult form of the creature that creates the funnel-shaped depressions in sand or other loose soil on the ground. Antlion larvae create those holes and then lie in wait at the bottom of them with only their poison-injecting mandibles exposed. Ants are common victims of antlion larvae because they can slip into the hole if they get too close, sliding inescapably down to the deadly waiting jaws of the larva.

Again, there’s surely no way those ants recognized the antlion adult as the grownup version of that horror-pit-dwelling nightmarish creature. If they did recognize it, though, the attack might have felt that much better as they exacted some measure of revenge upon a creature that likely consumed a number of their kind earlier this year.

As an observer to the event, I felt conflicted. Everyone involved was doing their job and no one was at fault in any way. There was no reason for me to interfere, but that antlion did look awfully pitiful in the jaws of all those ants. After a minute or so, I couldn’t take it any longer, so I took a piece of dried sunflower stem from nearby and lifted the antlion away from the flower. I tried to push some of the ants off of it but their jaws were so tightly clenched, I couldn’t move them. Sadly, I lifted the antlion back to the flower and let the ants finish their work.

This was the third time this year I’ve seen ants farming aphids. Each time, I’ve seen a cluster of ants on a plant and then upon closer inspection spotted the aphids. If you’ve not seen this phenomenon before, just keep your eyes out for multiple ants and take a closer look when you find some. When you find some, you can watch the ants scrambling around, tapping the aphids, and occasionally looking around menacingly for threats.

A couple times, while photographing the ants above, one would stop and turn to face me, lifting its head and torso off the plant toward me. It might have been just trying to get a better look at me, but after seeing what happened to the antlion, I also imagine it might have been issuing a warning. If so, message received!

This entry was posted in Uncategorized by Chris Helzer. Bookmark the permalink.

About Chris Helzer

Chris Helzer is the Director of Science for The Nature Conservancy in Nebraska. His main role is to evaluate and capture lessons from the Conservancy’s land management and restoration work and then share those lessons with other landowners – both private and public. In addition, Chris works to raise awareness about the importance of prairies and their conservation through his writing, photography, and presentations to various groups. Chris is also the author of "The Ecology and Management of Prairies in the Central United States", published by the University of Iowa Press. He lives in Aurora, Nebraska with his wife Kim and their children.

6 thoughts on “Defense or Revenge or Both?

  1. This is all fascinating brand-new information — antilions, ant/aphid world, larva pits. Thank you for opening up a part of world I had no idea existed. You’re a great part of our world!



  2. Hey Chris, one time I actually was touching a plant and I was immediately covered in ants that were moving extremely quickly. I think it’s just a defense mechanism/Territorialism and I don’t know if it’s specific to particular predators or incident objects or what. Right now my common milkweed has at least three kinds of ants on it I think. So far none of them have swarmed me though so I’m not sure why it happens in certain instances.

  3. Hi Chris: Usually I like to ID the ants in a post like this, but none of your otherwise cool photos have the right angle and focus on certain details I would use to do so. Best I can say is something in the Formica integra group of species, which are all famously fond of aphid tending/defending.


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