Cockroaches, although nonsocial insects, make collective decisions for the good of their populations just as ants, bees and termites do, said a study released by the Proceedings of the National Academy of Sciences.
The paper is part of a larger study on cooperation between insects and robots, said José Halloy, chief researcher from the Université Libre de Bruxelles, in an e-mail from Brussels.
"Less important for the moment, and not related to our project, cockroaches are pests, and to control the population, it is important to understand how they are distributed in space," said Halloy, who studies the social behavior of insects and other arthropods.
Cockroaches are considered gregarious, not social, creatures, in that they live in groups but form colonies.
The researchers used a circular Petri dish with identical shelters to study the patterns of division among cockroaches and how they balance crowding. Each cockroach was free to stay in a chosen shelter or leave for another until the group stabilized, the study said. The cockroaches acted as equals in determining the distribution of the population among shelters.
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"It is well-known that social insects such as ants are able to perform collective choice, which was not so evident among gregarious insects," Halloy said. "Our second hypothesis is that similar mechanisms of communication and decisions are used by gregarious insects and social insects."
If 50 cockroaches could fit into one large shelter, the insects stayed together, the study said. Offered three smaller shelters capable of holding 40 insects each, the 50 would divide equally between two shelters and leave the third empty, the study said.
The division surprised researchers, Halloy said — it shows the roaches are following behavioral rules and seeking cost benefits in deciding to split up.
