Wing-clapping is a conspicuous and poorly understood behavioural trait in damselflies. Its function has long been debated and several hypotheses have been proposed to explain why damselflies clap their wings, even when there is no other damselfly nearby. Here, I outline the existing hypotheses: (i) the territorial declaration hypothesis, which suggests that wing-clapping is used by males to proclaim territorial ownership to rivals; (ii) the thermoregulation hypothesis, which suggests that wing-clapping cools the body; and (iii) the courtship hypothesis, which suggests that wing-clapping is integral to the courtship behaviour of males. To these I add a fourth hypothesis, the mating call effect, which states that males use wing-clapping as a conspicuous signal to attract mates, prior to courtship. I tested these hypotheses in the neotropical calopterygid Mnesarete pudica. The investigation was conducted in the field in Minas Gerais and São Paulo, Brazil, with frequencies of different behaviours being recorded by direct observation of marked individuals. The results show no support for the territorial, thermoregulation, or the courtship hypotheses. A strong association between wing-clapping and other potential signals such as brief flights and perch shifts is evident. I conclude that wing-clapping behaviour in Mnesarete pudica, and perhaps in other damselflies, may increase male conspicuousness to females and attract them to territories.