Wing polymorphism and asymmetric male genitalia are intriguing morphological phenomena occurring in insects. Among Emesinae, or thread‐legged bugs, the tribe Metapterini Stål exhibits these two interesting morphological attributes. Nonetheless, evolutionary interpretations of these phenomena cannot be put forward because phylogenetic hypotheses for Emesinae are lacking. Thread‐legged bugs are easily recognized among assassin bugs due to their elongated and seemingly delicate body. The tribe Metapterini has 28 genera and approximately 280 described species. The only available phylogenetic hypothesis among Emesinae tribes was proposed by Wygodzinsky (1966), and it hypothesized Deliastini Villiers as the sister group of Metapterini, although this hypothesis has never been tested with cladistic approaches. Recent analyses using character sets of genitalia and prolegs suggest that Metapterini might not be monophyletic. In order to test these ideas, we compiled a morphological dataset of 138 characters that includes external morphological characters, detailed features of prolegs and genitalia of both sexes for Metapterini, which were analysed cladistically including 55 terminals, comprising 24 genera (85.7% of the generic diversity), 43 species of Metapterini and 12 outgroups. Metapterini was recovered as paraphyletic by the inclusion of Bergemesa Wygodzinsky, Palacus Dohrn and Stalemesa Wygodzinsky, all currently assigned to Deliastini. Gardena Dohrn (Emesini) was recovered as the sister group of Metapterini + Deliastini as suggested by Wygodzinsky (1966). Based on these results, we synonymize Deliastini syn. n. with Metapterini sensu n. and propose two new genera: Bacata Castro‐Huertas & Forero gen. n., for three Andean species previously placed in Liaghinella Wygodzinsky, and Valkyriella Castro‐Huertas & Forero gen. n. for Ghilianella borgmeieri Wygodzinsky. Ancestral state reconstruction of wing polymorphism indicates that males and females were fully winged in the ancestor of Metapterini sensu n. with two independent evolutionary transitions to the apterous and brachypterous conditions. The analysis of the symmetry of the male genitalia shows an ancestor with symmetric male genitalia and two independent emergences of asymmetrical male genitalia in Metapterini.

The assassin bug tribe Metapterini belongs to the subfamily Emesinae (Hemiptera: Heteroptera: Reduviidae). Morphologically, it is characterized by the conspicuous basal process of the posteroventral series in the foreleg and the presence of wing polymorphism, with a high proportion of the genera with micropterous or apterous species. Here, the male and female ectodermal genitalic structures are documented for ten genera and twenty-three species of Metapterini, including eight species of the speciose genus Ghilianella Spinola, 1850. Descriptions and digital macrophotographs are provided for abdominal segment 8, pygophore, parameres, and phallus of the male, and for tergite 8, tergite 9, gonocoxae, gonapophyses, gonoplac, and bursa copulatrix of the female. The asymmetric male genitalia within Emesinae are discussed. From this morphological documentation sixty six phylogenetic characters are coded, presented as a data matrix and analyzed cladistically, and their potential usefulness for resolving relationships among Metapterini is discussed.

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Tagalis Stål is recorded for the first time from Colombia and two species are described as new: Tagalis dichroa sp. nov., from Acandí (Chocó), and Tagalis albispina sp. nov., from Gorgona Island (Cauca). Based on the structure of the male genitalia of the known species, we here propose at least four species groups within Tagalis: 1) T. evavilmae, 2) T. femorata, 3) T. baenai, T. grossii, and T. marquesi, and 4) T. dichroa sp. nov., T. inornata, and T. seminigra. Tagalis albispina sp. nov. known only from the female holotype, cannot be placed into this scheme. Digital micrographs of the habitus and genitalia of the new species are provided. An updated key to the species of Tagalis is presented to facilitate the identification of the new species.

Liaghinella Wygodzinsky, 1966 (Hemiptera: Heteroptera: Reduviidae: Emesinae: Metapterini), is an endemic Neotropical genus with two described species, one from Jamaica and one from Colombia. In this paper we describe two additional new species from the high Andes in Colombia, Liaghinella heldamariae sp. nov from Monserrate and Villa de Leyva, and L. tuberculata sp. nov. from Chicaque Natural Park, both in the Eastern Cordillera. The new species were collected very close to the type locality of the previously known Colombian species, L. andina Forero, 2007. These two new species differ from L. andina by having both a pair of conspicuous tubercles on the posterior margin of the pronotum, and by the structure of the male and female genitalia. Species diagnosis and descriptions, digital macrophotographies, and a key to separate the species of Liaghinella are presented. A discussion on the small range distributions exhibited by the high Andean species of Liaghinella is provided.