Delayed juvenile dispersal benefits both mother and offspring in the cooperative spider Anelosimus studiosus (Araneae : Theridiidae)

Anelosimus studiosus juveniles usually remain in their natal webs with their mothers until maturity, forming temporary colonies in which individuals cooperate in web maintenance and prey capture. In a semi-natural environment, we experimentally removed juveniles from their natal webs at mid-development. In the control group, the juveniles were immediately replaced in their natal webs; in the experimental removal group, the juveniles were not replaced and a sample of them were allowed to build individual webs. Colonies and solitary juveniles were exposed to natural prey densities and censused regularly for numbers and stages of spiders, and for prey capture. On average, juveniles in colonies survived longer, developed faster, and had more resources per individual than did solitary juveniles. However, some of the solitary juveniles obtained more resources than individual juveniles in colonies. Mothers in the control group survived longer and produced second broods earlier than mothers in the experimental removal group. Within the control group, older and larger colonies captured more and larger prey. Larger colonies had a lower coefficient of variation in prey captured per juvenile. Overall, delayed juvenile dispersal benefits both juveniles and mothers.