Males assess chemical signals to discriminate just-mated females from virgins in redback spiders

In species where virgin females have higher reproductive value to males than nonvirgin females, selection will favour males that can discriminate female reproductive status. Similarly, while virgin females may actively seek to attract males, nonvirgin females may seek crypticity after mating if copulation is costly. Here we show that Australian redback spider males, Latrodectus hasselti, discriminate female maturity and mating status based exclusively on web-borne chemicals. Male activity on extracts from webs of virgin females significantly exceeded activity on extracts of webs of juveniles, nonvirgin females and solvent controls. While this level of discernment of female reproductive status has been found in other spiders, here we show that discrimination of web-bound chemicals produced by virgin females disappears rapidly after these females mate. Extracts of webs built by females immediately after copulation elicited no more interest from males than did solvent controls. Redback males dismantle much of their mate's web during courtship, and these results suggest that the web rebuilt by females after mating would not trigger male courtship. We speculate that this rapid shift would significantly reduce the opportunity for polyandry in nature.