Heteragrion triangulare Hagen in Selys, 1862

(Figs. 65a–d)

[Key locator: Key to Group A species, couplet 4 (3)] Heteragrion triangulare: Hagen in Selys 1862: 22–23 [20–21 reprint] (♀ description);— Selys 1886: 58–59 (description of ♁ and ♀ unsure if they are conspecific);— Calvert 1909: 112–114, Fig. 39 (description of ♁ and ♀, illustration of ♁ appendages in mediodorsal view);— Williamson 1919: (key to species, ♁ in couplet d1, ♀ in couplet c1; discussion on species, authorship and Selys’s 1886 descriptions, illustrations of ♁ and ♀ head and prothorax in dorsal view, ♁ appendages from Calvert 1909; figs. 17–18, 112, 137–138);—St. Quentin 1970: 259 (erroneously designates Vienna female as lectotype instead of holotype);— Lencioni 2005: 142 (data on description and distribution, illustration from Calvert, 1909; fig. 89a);—Machado 2006: 1068–1069 (differences from H. mantiqueirae and H. dorsale);— Garrison et al. 2010: 88 (list of Heteragrion species);— Storari et al. 2019: 488 (list of species);— Lencioni 2013: 14 (synonymic list, information on types, distribution, diagnosis; figs. 25, 34d–f, 35, 40d–g, 41, 47g –h, 55, 65, 75);— Lencioni 2017: 161–162 (general taxonomic information; distribution; figs. 84–85);— Dalzochio et al. 2018: 7 (list of species from Rio Grande do Sul).

Heteragrion beschkii: Lencioni 2005: 128 (misidentification).

Material examined. 2♁♁ BRAZIL, Mato Grosso state, Chapada dos Guimarães, Olho de Peixe, xi.1963, Werner & Alvarenga leg., ABMM; 1 ♁ Goiás State, Barro Alto, 20.v.2009, (-15.0883, -48.9738), S.L. Dutra, N.S. Pinto, C.C. Nóbrega & E. Santos leg., FAAL .

Known distribution. Argentina and Brazil (states of Goiás, Mato Grosso, Minas Gerais, Santa Catarina, Paraná, Rio de Janeiro and Rio Grande do Sul).

Diagnosis and remarks. The IUCN Red List currently classifies H. triangulare as Data Deficient. However, this assessment requires updating, as additional data on collections and taxonomy of this taxon have been added since its publication in 2009 (von Ellenrieder 2009c; Lencioni 2013). This species possesses a tubercle or apophysis on the ventral BP portion, a feature that is shared only with H. ictericum and H. pemon . The following character combination distinguishes this species from the remainder of Group A species: ML narrow, with squared apex (Fig. 65c), ridge slightly curved, small, bearing strong teeth (Fig. 65c–d).