Experimental manipulations of dispersal in the subsocial spider, Theridion pictum

Summary

Theridion pictum (Walckenaer) is a subsocial spider, that is, the mother actively takes care of her offspring for an extended period of time after they emerge. It is demonstrated that spiderling dispersal is affected by the availability of food in the maternal web. Experimental manipulations indicate that in those webs where less food was provided, spiderlings dispersed significantly earlier and in significantly greater numbers. These results illustrate the importance of food availability as a permissive factor in the evolution of social spiders from subsocial ancestors. Food availability also affects the pattern of sex-biased philopatry and dispersal. Although both sexes are more likely to remain in the maternal web when more food is available, females are relatively more likely to do so. When less food is available, females are relatively more likely to disperse than are males.