For woodlice, also known as pill bugs or roly polies, serenity is contagious. The gregarious bugs congregate in large social groups, and when one roly poly is calm, it makes the others calm too, a pair of researchers from Université Libre de Bruxelles in Belgium report in PLOS Computational Biology

The woodlice in question were caught in a university garden. The researchers put various groups of them in a circular enclosure at different times and watched how they interacted, and how fast they moved (a measurement of their anxiety or serenity). 

The more time the excited woodlice spent together with calm woodlice, the calmer they became. The researchers hypothesize that being with other woodlice “may promote a collective entry into a behavioral quiescence or sleep-like state,” which might explain why groups of the bugs don’t always run away in dangerous conditions (for example, when exposed in the open) while individual pill bugs do. The larger their group, the slower the bugs were to respond to danger.  

The researchers suggest that because of their social lifestyle, woodlice might be a good model for studying collective group behavior.