The weevil genus Leschenius del Río (Curculionidae: Entiminae: Naupactini) is distributed in the northern Andes, in Colombia and Ecuador. Among its species, L. vulcanorum stands out as an important pest of potatoes in its parthenogenetic form, which is known as "tiroteador de la papa". In this study, the adult male and the larval stage (first and mature larvae) of L. vulcanorun are described and illustrated for the first time. A description of the male of Leschenius bifurcatus is also provided. A new bisexual species was discovered, Leschenius ventrilingulatus sp. nov., and is described from Ecuador. An updated phylogenetic analysis was performed, including the new species, with results indicating a sister group relationship between L. ventrilingulatus and L. vulcanorum. They can be distinguished because the former is usually of smaller size and is covered by denser and thicker setae, has shorter antennae, a subcylindrical shape of the pronotum, shorter elytra (about 1.5×longer than wide at base), the female has ventrite 4 with a posterior rounded projection, and posterior margin of ventrite 5 subacute, not excavated. This paper also includes lectotype designations, a revised key to all known species of Leschenius, habitus photos of males and females, illustrations of genitalia, and a distribution map.
Keywords: Andean species; Immature stages; Leschenius bifurcatus; Leschenius ventrilingulatus; Neotropical region; Parthenogenetic weevils; South America; Sp. nov.
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