Heteragrion alienum Williamson, 1919

Vilela, Diogo Silva, Lencioni, Frederico A. A., Bota-Sierra, Cornelio A., Ware, Jessica L. & Bispo, Pitágoras C., 2023, Taxonomic revision of the Neotropical genus Heteragrion Selys, 1862 (Zygoptera: Heteragrionidae): male morphology, new species and illustrated key, Zootaxa 5356 (1), pp. 1-96 : 20

Heteragrion alienum Williamson, 1919

( Figs. 9a–e )

[Key locator: Key to Group B species, couplet 17 (16)]

Heteragrion chrysops: Calvert 1901: 62–64 (misidentification; key to species, ♁ and ♀ in couplet 3; described morphological and coloration differences with H. tricellulare ).

Heteragrion alienum: Williamson 1919: 13 , 33–34 (key to species, ♁ in couplet d2, ♀ in couplet d2; description as a new species by coloration characters, based on material from Guatemala; comparison with H. albifrons and H. chrysops ; figs. 5, 37, 38, 39, 57, 68, 88, 89, 105, 152, 153);— Paulson 1981: 303–304 (comparison of coloration patterns with other Heteragrion species);— Gonzalez-Soriano et al. 1982: 56 (record in Los Tuxtlas, Mexico);— Novelo-Gutiérrez 1987: 11–22 (description of F0 larvae);— Garrison et al. 2010: 88–89 (list of Heteragrion species; figs. 371, 376–378);— Rodríguez-Tapia et al. 2022: 274 (listed among species with an index of environmental vulnerability);— Carrillo-Muñoz & García-Miranda 2022: 196–203 (species list from Mexico).

Material examined. 2♁♁ MEXICO, Veracruz, “Los Tuxtlas”, Arroyo Tatocapán , 29.viii.1958, G.H. & A.F. Beatty leg., ABMM (two males in the same envelope) .

Known distribution. Guatemala, Southern Honduras (Dennis Paulson pers. comm.) and Mexico.

Diagnosis and remarks. Regarding cercus morphology, H. alienum is close to H. chrysops , H. valgum , H. calendulum and H. eboratum , with which it shares the MP ridge bearing only small teeth and not partially covering ML. This species can be separated from these and other Group B species by the following character combination: BP the longest cercus portion in length ( Figs. 9c–e ); ridge above ML consisting of very small denticles, not partially covering ML ( Fig. 9e ); ML bearing no teeth or carina on its plate ( Fig. 9e ); AP longer than MP, bearing a longitudinal depression ( Fig. 9c ).

Figures

FIGURE 9. Heteragrion alienum: (a) anterior view of head; (b) lateral view of pterothorax; (c) dorsal view of cercus, showing longitudinal depression on AP; (d–e) cercus in mediodorsal view. AP: apical portion.