“…Gregarious behaviour in cockroaches is a famous example of presocial behaviour (Schal, Gautier & Bell, 1984;Gautier, Deleporte & Rivault, 1988;Nalepa & Bell, 1997;Grandcolas, 1999;van Baaren et al, 2002van Baaren et al, , 2003b. It has been recently analysed in a molecular and morphological comparative framework in the subfamilies Zetoborinae and Blaberinae (Grandcolas, 1991(Grandcolas, , 1993a(Grandcolas, , b, 1998Pellens, Legendre & Grandcolas, 2007a;Pellens et al, 2007b), which provided both a phylogenetic reference and a natural history context for the interpretation of social behaviour observed in the laboratory (Grandcolas, 1991;van Baaren & Deleporte, 2001;van Baaren et al, 2002van Baaren et al, , 2003a. In a first attempt to understand the evolution of social behaviour, relevant categories such as 'gregarious', 'solitary' and 'subsocial', have been mapped onto a phylogenetic tree based on morphology (Grandcolas, 1993a(Grandcolas, , 1998.…”