Silk of females performing maternal care elicits reduced courtship responses in male spiders

Chemical communication plays an important role during many mating interactions. Female chemical signalling for mate attraction is expected to vary based on the females' state in order to maximize fitness, to attract males when females are fertile adults and to avoid superfluous matings; for example, during maternal care. We tested if females of the spider Pisaura mirabilis vary in their silk-bound signalling during developmental, reproductive and maternal care states by observing male courtship responses upon contact with their silk lines. We expected females to signal, and males to increase their courtship efforts, when adults (as opposed to juveniles or subadults) and when free from tending their eggs. Males were indeed more likely to court silk of sexually receptive adult females and less likely to court silk of egg-carrying females. This may suggest variation in female signalling, pointing to costs of continued mate attraction during maternal care. Egg fertilization appears to be an important factor linking maternal care to signalling, as males courted silk of egg-caring mated females less than that from unmated females with unfertilized eggsacs. Insemination alone, on the other hand, is not relevant, as we found no differences between courtship of silk of unmated and mated females, probably due to the nutritional benefits of male nuptial gifts and the indirect benefits of polyandry to females. In such a system, selection is likely to favour male discriminatory abilities to reduce reproductive costs associated with nuptial gifts. (c) 2025 The Authors. Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour. This is an open access article under the CC BY license (http://creativecommons.org/licenses/ by/4.0/).