Maternal regurgitation in Anelosimus baeza and A. nigrescens (Araneae: Theridiidae)

In the social behaviour of arthropods, regurgitation (feeding of the young) is a component of maternal care. In this paper, we describe regurgitation under laboratory conditions in species that share the same habitat, one subsocial (Anelosimus baeza) and a species considered to be solitary (Anelosimus nigrescens). The recently emerged spiderlings were fed by five of the nine A. baeza and six of the eight A. nigrescens females. In both species, the mother is critical in the initial stages, as spiderlings cannot feed themselves until the second instar. Our data suggest that A. nigrescens may be a subsocial species; this is the first report of regurgitation in these species. This fact shows the importance of regurgitation contributing to cooperation in live spiders. Future studies on maternal behaviour in these species are needed to elucidate the degree of sociality.