Alloparental adoption of offspring by conspecific female spiders regardless of sociality level (Araneae, Theridiidae, Anelosimus).

Maternal care, including offspring feeding, occurs in 20 theridiid, eresid, and agelenid spider species. The objective of this study was to determine whether females of four species of the genus Anelosimus (Araneidae, Theridiidae) feed on the offspring of other mothers and whether they are able to recognize their own offspring. This project focused on females from species of the same genus with different degrees of sociality: a social species (Anelosimus dubiosus Keyserling, 1891), an intermediate species (Anelosimus jabaquara Levi, 1956), a subsocial species (Anelosimus baeza Agnarsson, 2006), and a solitary species (Anelosimus nigrescens Keyserling, 1884). We observed six behaviors he four Anelosimus species, without significant differences in frequency among the species. The lack of offspring recognition could be one of the mechanisms that facilitates the evolution of alloparental care, promotes adoption and cooperation, and increases offspring survival. The evolution of alloparental care is key to elucidating the evolution of cooperative life. These data shed light on the evolutionary pathways leading to different types of sociality in spiders.