Trigonospila unicaldasi new specie, is described for the first time for science. In order to differentiate it from other rarely occurring species in the Americas, key characteristics of the adult were identified through scanning electron microscopy. The species was found parasitising adult weevils of the genus Compsus sp. (Coleoptera: Curculionidae) associated with citrus crops in the central coffee-growing region of Colombia. The interesting symbiotic phenomenon of control described in this paper is considered unusual in the biology of Tachinidae given that only 5-10% of the family parasitise their hosts at the adults stage.