Social recapitulation: moulting can restore social tolerance in aggressive spiderlings

In many taxa, the subsocial route is considered the main pathway to permanent sociality, but the relative contribution of offspring interactions and parental care to the maintenance of cohesion and tolerance at advanced developmental stages remains poorly studied. Spiders are relevant models for this question because they all show a transient gregarious phase before dispersal, and the transition to permanent sociality, which concerns approximately 20 of the ∼50,000 species, is assumed to rely on the subsocial route. Using spiderlings of the solitary species Agelena labyrinthica, we manipulated the social context to demonstrate that tolerance in aggressive juveniles can be restored when exposed to siblings after moulting. We propose that moulting can reopen closed critical periods and renew the imprinting to social cues and thus lead to the reacquisition of tolerance. Our study highlights the critical role of contacts between juveniles in the expression of tolerance, which opens novel avenues for understanding social transitions.