This fly is easily recognised by its wings which are smoky black from about half way, with (in the male) distinctive white tips. They are usually found close to water, where they feed by catching small freshwater crustaceans and mosquito larvae from the surface. They have a complex courtship dance involving the male waving his wings at the female (hence the “semaphore” name) and then hovering in front of her, before embarking on an aerial display flight.