Xenos vesparum is a parasitic insect species of the order Strepsiptera that are endoparasites of paper wasps in the genus Polistes (most commonly Polistes dominula) that was first described in 1793. Like other members of this family, X. vesparum displays a peculiar lifestyle, and demonstrates extensive sexual dimorphism. Morphology Males and female of this species show remarkable sexual dimorphism according to their mating system. Both develop inside the abdomen, where males pupate and emerge, while females permanently reside inside. Males Adult males are free-living, flying insects, whose extremely short (<5 hours) adult lives are solely dedicated to finding a mate, which they are thought to locate by scent. After locating a mate (who is protruding from the host wasp's abdomen), the male lands on the wasp's abdomen, holding on with its legs and wings, while avoiding the brushing of the wasp's hindlegs, which could potentially dislodge it. The male then inseminates the female by either spreading sperm around the female's genital opening, where...