Jonathan Webb in BBC News:
Colonies of several hundred ants show consistent differences in the way they behave, just like individual people do. Certain behaviours go together – for example, a colony that explores more widely for food also tends to respond more aggressively to an intruder. Such a colony has a more “risk-taking” personality and this was more common in the north, where the climate is colder. “I'm really interested in why personalities exist,” said Sarah Bengston, a PhD student at the University of Arizona who led the research. Her study is published in the journal Proceedings of the Royal Society B. Ms Bengston explained that although we know most animals have personalities, we do not yet understand why these evolved. “Sometimes individuals behave differently from one another, and when they do that repeatedly through time, we say that they have a personality.”
As such, there is nothing to stop a colony of insects from having a personality – as Ms Bengston found when she tracked how colonies behaved up and down the western US, both in the wild and when she bundled them up and watched them in the lab. Once back in the lab, whole colonies of 200-600 ants could be filmed inside transparent containers, and the videos analysed to measure things like the level of physical activity and aggressive behaviour. But some measurements, such as how far the ants would go foraging for food, had to be done in the field.