Reproductive interference between two sibling species of gift-giving spiders

► We provide evidence of reproductive interference between two spider species. ► Males of both species offer a prey wrapped in silk as a nuptial gift to females. ► Nuptial gift construction and acceptance is induced by species-specific cues. ► Individuals of different sexes and different species pay highly asymmetric costs. ► Selective pressure for species recognition is stronger on the smaller species.