Phylogénie Et Evolution Du Comportement Social Chez Les Blattes ...

An n e x e srespectively; their larvae aggregating under small bark fragments, while the adults seem todisperse (Grandcolas, 1993a). These three species have similar morphology, medium-sizedwith a flattened and widened body.S.l. inhabits pendulous bird nests only (Roth, 1973). Young nymphs disperse aftereclosion. But later, during the course of their development, they aggregate with adultsin the same nest (van Baaren et al., 2003) and they hide within its thick woven wall andbottom filling (similar to S. nitor in French Guiana, Grandcolas, 1993a). This species ismorphologically different from other Zetoborinae except P.b., being slender and with longerlegs. P.b. burrows galleries inside rotten trunks of softwood trees. Females stay in chamberswith their neonates during one or two weeks. Then, the young nymphs leave the chamber butremain relatively aggregated (Pellens et al., 2002). All these species are nocturnal, being moreactive during the first part of the night (FL and PG, pers. obs.). T.a. and L.e. move slowlyand, together with the more rapid P.n., they display a strong freezing posture when disturbed.According to phylogeny, S.l. and P.b., the most mobile species in this sample, lost this posture(Grandcolas, 1998b).Behavioral interaction experiments and statistical analysesObservations were carried out on young larvae in order to compare behavioral traitsof solitary, subsocial, and gregarious species of Zetoborinae. All these species have the samenumber of instars and mid-development larvae were selected to carry out the experiments.Larvae were not selected according to their sex, given that preliminary observations have notrevealed any difference in this respect (see also van Baaren and Deleporte (2001) for a similarreport about sex influence on gregariousness in Zetoborinae).Tolerance to crowdingTolerance to crowding was estimated in the first series of observations. Ten larvae ofsimilar size were randomly taken from cultures and placed together on a large plastic plate319