Argia bicellulata Calvert, 1909

Vilela, Diogo Silva, Guillermo-Ferreira, Rhainer, Del-Claro, Kleber & Cordero-Rivera, Adolfo, 2018, Females of two species of Argia from Chapada dos Guimarães National Park, Brazil (Odonata: Coenagrionidae), Zootaxa 4420 (3), pp. 430-438 : 431

Remarks on the female of Argia bicellulata Calvert, 1909

Figs. 1–11 .

Material examined. 3 ♀ (LESTES, Cod. ACR 0 3297, ACR 3322, ACR 3323), BRAZIL, Mato Grosso, Chapada dos Guimarães National Park, Rio Paciencia (15.3438° S, 55.8322° W, 280 m), 25 x 2015, R. Guillermo-Ferreira leg. [RGF].

Measurements. Fw 14.3, Hw 13.8, abdomen 18.8, total length 23.4.

Variations on the specimens examined (n = 3). The mesostigmal plates illustrated here ( Figs. 2‒3 ) are from Calvert's single female. No variation on mesostigmal plate morphology was detected, comparing our specimens to figures of Calvert's female ( Figs. 2‒3 ); Wing venation: no variation RP2 branching and postquadrangular cells; postnodal varied as follows: 10–11in Fw and 9–11 in Hw ( Table 1); size varied as follows: abdomen 18.3–20.2 (19.1±0.9), total length 23.3–25.9 (24.2±1.4), Fw 14.3–14.9 (14.5±0.3), Hw 13.8–14.6 (14±0.4). Body coloration had little variation on the specimens examined ( Figs. 4–11 ), being more visible on the slightly different post ocular spots coloration ( Figs. 10–11 ).

Differential diagnosis. Argia bicellulata is the smallest known species of this genus (Garrison & von Ellenrieder 2015). Females are similar to males ( Figs. 1a‒b ) in having the black ventral thoracic coloration, a unique trait distinguishing A. bicellulata from its sympatric congeners ( Figs. 8‒9 ). The narrow posterodistally pointed digit-like mesostigmal lobe ( Figs. 2‒3 ) differs from other sympatric species including the broadly arcuate lobe in A. botacudo Calvert, 1909 ( Figs. 12‒13 ) and broad thumb-like lobe in A. tupi ( Figs. 15‒16 ). As stated by Calvert (1909), A. bicellulata females have a coloration that resembles the male and by examining the females with living colors ( Figs. 4‒11 ), we noticed some differences from its original description. The dorsal spot on the S2, blue in Calvert’s female, is pale on the examined females of this study. On the contrary, the S9 dorsal spot was pale in Calvert’s female, and our females have it in blue. The postocular spots are smaller than in males, and its coloration is violet, instead of the blue that is found in males. A remarkable trait is the number of Fw postquadrangular cells ( Table 1), numbered three in all our specimens (a frequent occurrence to Argia species), which enforces the synonymy of Diargia Calvert, 1909 with Argia , where Diargia does not present strong enough characteristics to be considered a different genus ( Gloyd 1968). All other morphological traits on our specimens agree with Calvert’s description, such as the lack of vulvar spines on S9, hyaline wings with a reddish venation at the base, darkening distally.

Habitats and ecology. Both sexes were collected in palm swamp (i.e. veredas, Vilela et al. 2016) areas, in the same locality from where a new Argia species was recently discovered (Vilela et al. 2018). At Paciência River the palm swamp had dense vegetation and was connected to the stream although we found A. bicellulata only within palm swamp including small slow streams within the palm swamps. This species can be confused with Ischnura Charpentier, 1840 or Argentagrion Fraser, 1948 species due to its small size and flight behavior, flying through the dense grass vegetation of the swamp.

Figures

FIGURE 1 a‒b. Argia bicellulata (Calvert) BRAZIL: Chapada dos Guimarães; 1a. ♀ (ACR 3322); 1b. ♂ (ACR 3326)

FIGURES 2‒3. Argia bicellulata (Calvert) BRAZIL: "Chapada" (paralectotype) mesostigmal lobes; 2. anterior view; 3. dorsal view.

FIGURES 4‒11. Argia bicellulata (Calvert) BRAZIL: Chapada dos Guimarães; 4. S1‒10, ♀ (ACR 3322); 5. S1‒10, ♀ (ACR 3326); 6. S8‒10, ♀ (ACR 3326); 7. S8‒10, ♀ (ACR 3322); 8. thorax, ♀ (ACR 3322); 9. thorax, ♀ (ACR 3326); 10. head, ♀ (ACR 3326); 11. head, ♀ (ACR 3322).

FIGURES 12‒13. Argia botacudo (Calvert) BRAZIL: “Chapada” mesostigmal lobes; 12. ♀ dorsal view; 13. ♀ anterior view.

FIGURES 15‒16. Argia tupi (Calvert) BRAZIL: Serra do Cipó mesostigmal lobes; 15. ♀ dorsal view; 16. ♀ anterior view.