Warrior or Nanny: Spiders Match Job to Personality

It turns out that spiders are highly social insects, establishing a sort of caste system within their colonies. Female spiders establish division of labor roles based on their personalities - they are either a "warrior" or a "nanny," a new study says.

The findings demonstrate how such social structures work, the researchers added.

Other insects such as ants, bees, wasps and termites also form colonies divided into specialized social standings - for example, the reproductive queen bee and worker males, Live Science reported. But spiders' division of labor takes it a whole other level.

Anelosimus studiosus spiders can be found from North to South America, forming colonies, hunting together and sharing their webs and prey. The females appear to be either one of two types: aggressive or docile.

"Their personalities, unlike in many other species, are very clear-cut," said lead study author Colin Wright, a behavioral ecologist at the University of Pittsburgh.

Previous studies have shown that the aggressive females are more likely to attack intruders and defend the web, and that colonies with a mix of the two personality types do better in the long run than those with exclusively one or the other.

Clearly the aggressive types have an important role to play, but docile ones serve an unknown purpose.

To figure it out, scientists examined how well 141 aggressive and 148 docile female spiders performed individually at various tasks. They also created 60 laboratory colonies consisting of two aggressive and two docile female spiders, observing how they divided up the work.

"When the researchers tested the aggressive and docile spiders on an individual basis, they found that the docile spiders were less likely to pounce on easily available prey and that the webs they constructed were sub-par, compared with their aggressive peers," the Los Angeles Times wrote. "The aggressive females, on the other hand, weren't so great at brood-rearing - they tended to attack and kill the babies while sharing food with them."

The study team hopes that future research can explain what causes personality differences in these species, though they do suspect a genetic component.