Wednesday, August 01, 2007

New role for majors in Atta leafcutter ants

via Ecological Entomology

Abstract. 1. Atta (Hymenoptera: Formicidae) leafcutter ants display the most polymorphic worker caste system in ants, with different sizes specialising in different tasks. The largest workers (majors) have large, powerful mandibles and are mainly associated with colony defence.

2. Majors were observed cutting fallen fruit and this phenomenon was investigated in the field by placing mango fruit near natural Atta laevigata and Atta sexdens colonies in São Paulo State, Brazil.

3. Ants cutting the fruit were significantly heavier (mean = 49.1 mg, SD = 11.1 mg, n = 90) than the ants carrying the fruit back to the nest (mean = 20.9 mg, SD = 9.2 mg, n = 90).

4. Fruit pieces cut by majors were small (mean = 15.9 mg), approximately half the weight of leaf pieces (mean = 28.5 mg) cut and carried by media foragers. It is hypothesised that it is more difficult to cut large pieces from three-dimensional objects, like fruit, compared to two-dimensional objects, like leaves, and that majors, with their longer mandibles, can cut fruit into larger pieces than medias.

5. The study shows both a new role for Atta majors in foraging and a new example of task partitioning in the organisation of foraging.

New role for majors in Atta leafcutter ants
Ecological Entomology (OnlineEarly Articles).

Image: Atta Cephalotes; photograph © Alex Wild 2004


  1. Cool. Thanks for the heads up on the article. Two years ago, in my first field season on BCI, I was welcomed by the ants island by observing an Eciton raid on an Atta colony---something I now refer to as the Clash of the Titans. I found a new appreciation for the destructive abilities of the Atta majors--though in the end it seemed that the army ants got the better of them. It was amazing.

  2. "Atta (Hymenoptera: Formicidae) leafcutter ants display the most polymorphic worker caste system in ants.."

    I wouldn't instantly agree. Pheidologeton workers display polymorphism too, and it would be equally interesting to learn their labor division. But this kind of study is a luxury here.

    Regards from Indo-Australia

  3. I haven't read the new article, but Atta soldiers cutting fruits may be old news. Mintzer reported such behavior and it was noted here:

  4. Actually, I noticed that it's a 1995 Wetterer paper that is referenced in that article that actually says this explicitly:

    "Atta colombica majors are known to forage alongside smaller workers and cut the tough skin of fallen fruit (Wetterer 1995)"

  5. it's so cool to know someone dedicates to studying these great little creatures, in Venezuela they are called Bachacos... there is a band in Miami that honors this ants, they are called Bachaco. check them out at and you'll see their biography where they reference the ant.