A new species of Leptostygnus Mello–Leitão, 1940, Leptostygnus yarigui sp. nov. from Colombia (Santander department) is described and illustrated. Photographs of Leptostygnus leptochirus Mello-Leitão, 1940 (type species of the genus) and L. marchantiarum (González-Sponga, 1987), a map with geographical distribution and a key to the species of the genus are given. The first SEM images of a penis of a Leiosteninae member are shown with comments about the genital morphology in the subfamily.urn:lsid:zoobank.org:pub:3E5D9155-6BFF-4B63-A2C4-15D8172FCDD1