Harraca and colleagues have demonstrated that bed bug nymphs (Cimex lectularius) produce a chemical signal that interrupts the attempts of adult males to mate with them [4]. Because adult males, females, nymphs and eggs are found in aggregations around where the host sleeps (in the case of humans, our beds), encounters between males and nymphs are common. Copulation between an adult and a nymph is reproductively ineffective, but can be very costly to the nymph and the male; rupture of the cuticle for the nymph, and loss of sperm and other components of the ejaculate for males. As a result the reproductive fitness of the male and survival of the nymphs are parallel interests. These are exactly the circumstances that should favour the evolution of communication, because both signaller and receiver benefit from the information transfer. Two complementary manipulative experiments conducted by Harraca et al. [4] provide convincing evidence of effective communication between nymphs and males. When the glandular source of the scent that is unique to nymphs is blocked, males will copulate with them. When a nymph-specific compound or nymph-specific ratio of compounds were puffed on male-female pairs, mating was disrupted. Furthermore, males have sensory neurons that respond to the nymph odours. Thus, the chemical signal translates into the simple received message that the source nymph is not a reproductive female. The nature of copulation, known as traumatic or hypodermic insemination, may help to explain the evolution of communication between nymphs and males.