‘Mine or thine’: indiscriminate responses to own and conspecific webs and egg sacs by the false black widow spider, Steatoda grossa (Araneae: Theridiidae)

Female false black widows, Steatoda grossa (Araneae: Theridiidae) , build energy-costly webs. We tested the hypotheses (H1, H2) that females prefer their own webs and the chemical extract of their own webs to those of conspecifics, and (H3) that mated females discern between their own egg sacs and those of conspecifics. In choice bioassays, females indiscriminately accepted both their own webs and egg sacs and those of conspecific females, although they chose extracts of webs based on their chemical cues. The females’ indiscriminate responses to webs or egg sacs are likely due to a lack of selection pressure to reject webs or egg sacs of conspecific females.