Heteragrion calendulum Williamson, 1919

Heteragrion atrolineatum Donnelly, 1992 . (Holotype ♂, Allotype ♀ in USNM). Syn. nov.

Material Examined. COLOMBIA: 1♂ Holotype, Department of Antioquia, Municipality of Puerto Berrio, La Cristalina Township, 17 February 1917, J.H. and E.B. Williamson . 1♂ and 1♀: Department Risaralda, Municipality of Pueblo Rico, Santa Cecilia Township, Alto Amurrupá Reserve, Ranas de Cristal stream, 5.32033°N 76.17357°W 620m a.s.l., 15 February 2017, J. Sandoval and C. Bota leg . 6♂♂ and 2 ♀♀: PANAMA, Darién, Perresénico River, Estación Rancho Frío, 8.01982°N 77.73257°W 80m a.s.l., 17 November 2014, D. Delgado, A. Ramírez and R. Novelo leg.

Remarks. This species was described based on a single male collected at La Cristalina stream (Puerto Berrio- Antioquia) on February 17 of 1917, by Jesse Williamson and Edward B. Williamson, who were impressed by its beauty and rarity and tried, unsuccessfully, to catch some more specimens (Williamson 1919). Exactly one century after this first collection, a second collection was made on February 15 of 2017 at the Ranas de Cristal stream (Santa Cecilia-Risaralda) by Juliana Sandoval and Cornelio Bota-Sierra who, as the Williamsons tried in vain to get more specimens, luckily caught a pair in tandem. The male specimen matched Williamson’s description exactly (Figs 3i, k; 4b; 6a, i–j). Examination of female genital valves showed several rows of denticles (Fig. 9d) which places it in Lencioni´s group A. Williamson (1919) classified this species within the group B based on the small elongated finger-like paraprocts of male (Fig. 6j), which make this species an intermediate between groups A and B. Further analysis will be needed to determine the monophyly of these groups and where to place H. calendulum .

Specimens deposited in IEXA, collected in Panama and formerly identified as H. atrolineatum using Donnelly´s (1992) taxonomic key and diagnosis, were reexamined and compared to Williamson´s description of H. calendulum, as well as to the Colombian specimens. Also, Dr. Garrison compared the paratypes of H. atrolineatum in his collection to our pictures and description of the new Colombian specimens. After a thorough examination of these specimens, we conclude that H. atrolineatum is a junior synonym of H. calendulum (Figs 3i –k; 4 b–c, h–i; 5b; 6a–b, i–j; 8d). Donnelly (1992) followed Williamson’s (1919) criteria grouping H. atrolineatum with H. chrysops, H. alienum and H. tricellulare because of their pale coloration on dorsum of abdominal segments. Donnelly (1992) recognized a variation in color pattern with the Panamanian males having slightly darker color than Costa Rican males. Mark O´Brien, collection manager of the University of Michigan, Museum of Zoology, photographed the holotype of H. calendulum and Dr. Garrison photographed a Costa Rican paratype of H. atrolineatum, based on this evidence we concluded that the only difference between these specimens is the darker coloration pattern on the holotype of H. calendulum, which probably led Donnelly to confuse them using Williamson´s key. Therefore, we consider that H. atrolineatum is a junior subjective synonym of H. calendulum .

Bota-Sierra et al. (2016) erroneously recorded a second locality for H. calendulum in Amalfí-Antioquia. They were led astray by the similar coloration pattern of the face of H. aequatoriale with that of H. calendulum (Fig. 3g, i). After the rediscovery of H. calendulum and the comparison with diverse populations of H. aequatoriale, it becomes clear that the Amalfí population is a morph of H. aequatoriale, with a variation in face coloration close to H. calendulum .