SOCIALIZATION PROCESSES AND BEHAVIORAL PR EADAPTATIONS IN SPIDERS

Spider social species, while being relatively scarce, present a great diversity in their organization. The passage to permanent social life seems to have occurred several times, quite independently, in distinct lineages. Within these lineages the social forms do not differ from t he solitary ones by any marked morphological feature. This suggest tha t socialization consists basically in behavioural changes, and that th ese changes are easily produced. The information collected from extant species lead us to attribute such a phenomenom, at first, to certain characteristics, already present in solitary species, which can he con sidered as preadaptations to social life. All spiderlings are gregario us during their first days of living; in maternal species, spiderlings may show an extension of mutual tolerance and social cohesiveness up to an advanced stage. The evolutionary role of these preadaptations ma y have been amplified by behavioural plasticity, a characteristic foun d in many extant species. Moreover, the extension of interindividual i nteractions is likely to have made possible the emergence of cooperati ve activities, thence increasing the adaptative value of permanent soc ieties.