Leaf-Cutting Ants in the News

Flickr, by Charles Lam

Never in my life have I seen so much news on leaf-cutting ants! Ok, ok, there's only two findings but that still seems like a lot.

Most ants work in a kind of caste society, dividing labor among morphological subtypes within the colony. In the Atta laevigata leafcutter species, for instance, smaller worker ants take care of fungus growing on decaying leaves inside the colony, while larger workers focus on defending the colony. But all of the ants work on cutting and bringing back fruit pieces, which puzzled scientists Heikki Helantera and Francis Ratnieks. "Fruit is soft and can be cut by smaller workers," they write in the latest issue of Proceedings of the Royal Society B: Biological Sciences. "Why, therefore, are large workers involved?

It turns out that since fruit (unlike leaves) is three-dimensional, ants with larger mandibles can cut and carry much larger pieces back to the colony than smaller ants. Their results show "how size variation among worker ants enhances division of labour." Divide and conquer.

Just when your heart's melted from thinking of all that colonial cooperation, here's something a bit more scandalous. Ant colonies, like bees, have queens. It was thought that these queens developed from larvae that had been randomly selected, then carefully fed and nurtured by the rest of the colony.

But that theory's now been debunked, thanks to DNA fingerprinting done by biologists Bill Hughes and Jacobus Boomsma. Certain males, they found, carried a "royal" gene, making their offspring more likely to become queens. But here's the rub: the sisters of these royal males have no idea that their offspring is getting the shaft. Their results were published in PNAS on March 13. As Hughes (no relation) told LiveScience: "We think the males with these royal genes have evolved to somehow spread their offspring around more colonies and so escape detection. The rarity of the royal lines is actually an evolutionary strategy by the cheats to escape suppression by the altruistic masses that they exploit.�

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