thers offer childcare services.
In species like A. eximius, spiders are essentially clones. Brothers and sisters mate with each other, generation after generation, so that colonies become highly inbred.
Since adolescent spiders do not go off in search of new colonies, there is no influx of new genetic material. For that reason, some suspect that spider personalities develop as a result of early life experiences, not genetics. "In spite of a lack of genetic diversity, they exhibit this exquisite diversity in terms of their personalities," Pruitt says.
In 2013, he and his colleagues looked at a social spider called Stegodyphus sarasinorum, native to India, Sri Lanka, and Nepal. They found that individual personality traits predict which job each spider performs.
S. sarasinorum is found in dry scrubland. But like the spiders I found in the rainforests of Peru, these arachnids work cooperatively to build and maintain their webs and to capture food.
Social spiders have distinct personalities
Using tiny dabs of paint applied to the spiders, Pruitt and his team were able to track 40 from each of two different wild colonies. Individuals that were bolder were more likely to be involved in attacking prey – but other characteristics, like body size or a spider's level of aggression, did not factor into their vocation.
"Responding to stimuli from a prey caught in the web elicits different responses according to a set of individual characteristics," they concluded.
In other words, social spiders have distinct personalities, which in turn help to define their roles in the community.
In a way, that is not so different from human societies. Bold, risk-taking people might be more likely to wind up fighting fires or enrolling in a police academy, while the more calculating, deliberative types wind up as lawyers or architects.
Despite lacking a backbone, invertebrates like insects and arachnids lend themselves well to studying complex social behaviour. "When it comes to a behaviour that any sort of animal can do, insects [and arachnids] can do it, if not do it better," says entomologist Phil Torres.
After all, they have been evolving on our planet for a lot longer than any bird or mammal has.