Pocket Science – wasps airlift ants away from food

By Ed Yong | March 31, 2011 9:00 am

It’s not a very fair fight. In one corner is a tiny ant. In the other is a large wasp, two hundred times heavier and capable of flying. If the two of them compete for the same piece of food, there ought to be no contest. But sometimes the wasp doesn’t even give the ant the honour of stepping into the ring. It picks up the smaller insect in its jaws, flies it to a distant site and drops it from a height, dazed but unharmed.

Julien Grangier and Philip Lester observed these ignominious defeats by pitting native New Zealand ants (Prolasius advenus) against the common wasp (Vespula vulgaris). The insects competed over open cans of tuna while the scientists filmed them.

Their videos revealed that ants would sometimes aggressively defend their food by rushing, biting and spraying them with acid. But typically, they were docile and tolerated the competing wasp. Generally, the wasp was similarly passive but on occasion, it picked up the offending ant and dropped it several centimetres away. In human terms, this would be like being catapulted half the length of a football field.

The wasps never tried to eat the ants, and they never left with one in their jaws. They just wanted them out of the picture. Indeed, the more ants on the food, the further away the wasps dropped them. This may seem like an odd strategy but at least half of the dropped ants never returned to the food. Perhaps they were physically disoriented from their impromptu flight, or perhaps they had lost the chemical trail. Either way, the wasps could feed with fewer chances of taking a faceful of acid.

Reference: Grangier and Lester. 2011. A novel interference behaviour: invasive wasps remove ants from resources and drop them from a height. Biology Letters http://dx.doi.org/10.1098/rsbl.2011.0165

Comments (4)

  1. Daniel

    What I find most interesting here is the fact that wasps or ants would even bother fighting. There is way more tuna here than either group could consume, so it is perplexing to see why the wasp would waste energy removing those ants.

  2. Out in the wild, a food source like that probably isn’t going to be there for long; some bigger scavenger is likely to show up and snarf the lot at any moment.

    But even that is arguably no better than a just-so story. Evolution does not select for optimum strategies; it selects away from strategies that prove disastrous.

  3. That is really neat. I could see why the wasp wouldn’t want to kill the ant, as it could irritate the others, so the delicate transplanting of the insect seems to be the best solution.

  4. ANC

    this is rather interesting cos one would think the wasp wil eat d ant instead it throws it away but wil it continue dis pattern if d ants become large in number?

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