We report the first know case of male hind-wing aptery among the net-winged beetles (Lycidae). Five male specimens of Cautires apterus sp. nov. were discovered by sifting forest litter in a very small (approximately 300 meters by 50 meters) Kamwala Forest within the North Pare Mountains, Tanzania. Besides being wingless, males of C. apterus sp. nov. have remarkably small body, shortened elytra and reduced pronotal and elytral costae. Generic assignment of this externally unusual new species is based on the molecular phylogenetic analysis, the structure of the male genitalia and the shape of the pronotum. We discuss biological and evolutionary significance of the discovery and suggest that the winglessness of male lycid beetles correlates with the female neoteny.