Female spiders living in a colony may divide themselves into either "warrior" or "nanny" roles depending on their personalities.
The findings can help researchers gain insight into how different personalities in species can help divide up labor, LiveScience reported.
Species such as "ants, bees, wasps, [and] termites" often form societies that are separated into "castes" that can include sterile workers as well as soldiers, reproductive queens, and males, LiveScience reported.
The Anelosimus studiosus spider is found in the Americas; they live on communal webs that often house dozens of spiders, the Los Angeles Times reported.
The female spiders are believed to be either passive or docile, which helps determine their role in society. Aggressive females are more likely to attack intruders and prey.
Webs with females of both personality types tend to be more successful than those with all-docile female spiders.
"Although docile females don't participate very much at all in prey capture, aggressive spiders share prey with docile individuals," lead study author Colin Wright, a behavioral ecologist at the University of Pittsburgh, told LiveScience. "Everyone gets to eat."
The researchers were not sure about the role docile females played in the colony.
"[Docile females] have an overall negative impact on colony success," Wright told LiveScience. "Other studies, however, showed that mixed colonies performed better than colonies composed of either 100 percent docile or 100 percent aggressive colonies, showing that docile individuals must be doing something important in these colonies."
In order to determine the docile females' role, researchers looked at how 141 aggressive and 148 docile female spiders performed on certain tasks. They created 60 laboratory colonies consisting of two aggressive and two docile spiders; the purpose of this was to see how the spiders divided up the labor.
They found aggressive females were over twice as effective at capturing prey than docile ones and created webs that held prey for two-thirds longer. They also "repaired webs, attacked potential prey and defended against invasive funnel weaver spiders (Barronopsis texana)," three times more often, LiveScience reported.
On the other hand, offspring raised by docile females were twice as likely to survive as those raised by aggressive mothers.
"We were surprised at how good of parents docile spiders turned out to be," Wright said. "They're much better parents than aggressive spiders."
The study only looked at female spiders because males do little more than seek out mates and exhibit very little difference in personality.
"We hope other researchers will pay close attention to personality differences in their systems because animal personalities are seemingly ubiquitous across the animal kingdom," Wright told LiveScience.
The work was described in the Proceedings of the National Academy of Sciences.
