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The switch point theorem posits that both sexes should exhibit behavioural flexibility, switching between discriminant and indiscriminate mating, as their perceived demographic conditions change. The theorem also predicts that an individual’s mate choice should be more dependent on its own intrinsic characteristics and ecological conditions than on the exaggerated sexually selected traits possessed by potential mates. To test these predictions, we manipulated the operational sex ratio (OSR), a demographic factor, of adult Jamaican field crickets (Gryllus assimilis) under controlled laboratory conditions and evaluated whether the mate choices of females and males were influenced by their social environment, their own body size and the difference in the body size of available potential mates. Body size is under sexual selection in this species, with females preferring larger males and larger males exhibiting …