Argia acridens Garrison & von Ellenrieder, 2018

Garrison, Rosser W. & Ellenrieder, Natalia Von, 2018, Damselflies of the genus Argia (Odonata: Coenagrionidae) from Ecuador with descriptions of five new species, Zootaxa 4470 (1), pp. 1-69 : 7-9

Argia acridens Garrison & von Ellenrieder , n. sp.

Figs. 9 (head, thorax, S1– 3 ♂), 23 (head, thorax, S1– 3 ♀), 34 (S1– 3 ♂), 35 (S7– 10 ♂), 59 (S7– 10 ♀), 69 (mesostigmal plates ♀), 89 (genital ligula), 103 (appendages ♂), 136 (map), 142 (photo).

Etymology. Named acridens (L. adj.) in reference to the large medioventrally directed acuminate tooth on the male cercus.

Types. Holotype ♂: ECUADOR, Manabí Prov., 79 km west of Santo Domingo de los Colorados {0°20' S, 79°46' W, 260 m}, 7 May 1975, Paul J. Spangler et al. leg. [ USNM].

Specimens examined (all paratypes). 14 ♂♂, 3 ♀♀.

ECUADOR, Esmeraldas Prov.: 2 ♂♂, Canandé Reserve (0°31'13'' N, 79°5'12'' W, 470 m), 12–15 May 2015, Jessica Ware & Melissa Sanchez leg. [ RWG] ; Manabí Prov.: 1 ♂, 79 km west of Santo Domingo de los Colorados {0°20'29'' S, 79°46'13'' W, 260 m}, 7 May 1975, Paul J. Spangler et al. leg. [ RWG] ; 1 ♂, highway E40, 5 km west of Solano , stream/waterfall, noon {1°3'52'' S, 79°58'37'' W, 420 m}, 14 April 2010, Jerrell J. Daigle leg. [ RWG] ; 1 ♂ same data but trickle, sheet flow, Jim Johnson leg. [ JJ] ; 1 ♂ same data but highway E40, 5 km west of Solano , trickle, sheet flow {1°3'52'' S, 79°58'37'' W, 350 m}, 4 March 2010, Kenneth J. Tennessen leg. [ FSCA] ; Santo Domingo de los Tsáchilas Prov.: 2 ♂♂, 19 km east of Santo Domingo de los Colorados {0°18'49'' S, 79°1'44'' W, 744 m}, 5 July 1975, A. Langley & J. Cohen leg. [ RWG] ; 2 ♂♂, 1♀ same data but [ USNM] ; 3 ♂♂, 2 ♀♀ [1♂, 1♀ in copula], Tinalandia, 12 km east of Santo Domingo de los Colorados , stream and ditch near golf course, shallow water flowing over a rock face {0°17'2'' S, 79°3'0'' W, 2,000 m}, 6 October 1988, Sidney W. Dunkle leg. [ RWG] .

A medium-sized largely dark species with male cercus armed with a sharp medioventral tooth ( Fig. 103 ) and poorly developed mesostigmal lobe in the female ( Fig. 69 ).

Description of male holotype. Head: labrum, base of mandibles, genae and frons entirely pale (ivory green), anteclypeus brown, postclypeus pale with a well-defined midlateral spot on each side, epicranium black with small pale spot anterolateral to lateral ocellus, large violaceous postocular spot laterally confluent with eye, occipital bar black (as in Fig. 9 ), dorsal surface of postocular lobe black; antennae black, rear of head black above narrowing ventrally toward occipital foramen, remainder of rear of head ivory.

Prothorax black with following areas pale: diffuse rim on anterior lobe, dorsolateral spot on middle lobe confluent posterolaterally with pale propleuron, lateral third of hind lobe of prothorax. Pale areas of synthorax purple laterally, olive dorsally, with broad black middorsal stripe about twice as wide as olive antehumeral stripe, the latter slightly narrowing dorsally; broad black parallel-sided humeral stripe along humeral suture with posterior half merging into lighter shades of brown (as in Fig. 9 ), extending from base of mesinfraepisternum and connecting below antealar crest with middorsal stripe above and with dorsal portion of obsolete interpleural suture; metapleural stripe narrow; pale colors on side of thorax purple (as in Fig. 9 ).

Wings hyaline with venation black; pterostigma dark brown, surmounting 1 cell in all wings; postnodals Fw 11/11, Hw 9/9; postquadrangular cells Fw 3/3, Hw 3/3; RP 2 at Fw 5/5, Hw 4/4. Coxae and trochanters pale except for black on ventral and anterior portions of coxae and dorsum of trochanters; base of metafemora and external surface of tibiae pale, tarsi and armature black.

Abdomen (as in Figs. 9 , 34, 35) mostly black; S1 with a black basal ring, remainder purple; S2 violaceous with a black stripe laterally extending to apical fourth of segment, broadening dorsally with a narrow dorsal offshoot thus restricting pale dorsum of segment; S3 black with a pale basal ring and a narrowing pale dorsal stripe ending at apical half of segment, a diffuse pale ventrolateral stripe at along medial half of segment thus giving the appearance of a dark, pale, dark pattern when viewed laterally; S4–6 similar to S3; S7 black with small pale basal spot; S8–9 pale (purple) dorsolaterally, black ventrolaterally; S10 black; torus pale, appendages black.

Genital ligula ( Fig. 89 ) lacking microspinulate patch on ental surface proximal to flexure on sclerotized area; distal segment largely membranous armed basally with a curved sclerotized flagellum.

Torus transversely oval, swollen, occupying entire ventral margin of torifer and partially overlapping bilobed epiproct ( Fig. 103b ); area around epiproct and base of same black; cercus ( Fig. 103 a–e) subequal in length to paraproct, longer than wide, swollen basally with medial basal margin strongly convex but narrowing distally and with a strongly acuminate mediolaterally directed tooth; mediodorsal surface of cercus depressed, slightly concave near basal lobe; paraproct ( Fig. 103d, e ) unilobate, almost quadrate in lateral view with a small tuberculate tip.

Dimensions. Hw 19.5, abdomen 27.2, total length 34.8.

Description of female paratype ( Ecuador: Santo Domingo de los Tsáchilas Prov., 12 km east of Santo Domingo de los Colorados, streams south of river): Head, pro- and synthorax and S1–2 as in male ( Fig. 23 ), but pale areas more extensive and dark humeral stripe brown, not as black as middorsal stripe and blue gray; S3 black with an incomplete irregular pale basal ring not connected dorsally, a diffuse pale ventrolateral stripe at along medial half of segment thus giving the appearance of a dark, pale, dark pattern when viewed laterally; S4–5 similar to S3; S7 black with narrow pale basal ring connected to pale lateral stripe ending at apical fourth; S8 black laterally with a narrow basal ring and broader apical ring surrounding pale green dorsolateral spot; S9 black except for small pale dorsolateral spot at apical third; S10 black; ovipositor black with dorsal margin slightly pale, cercus black (Fig. 59). Mesostigmal lobe (as in Fig. 69 ) vestigial with posteromesal margin forming an elongate dorsoanteriorly directed glabrous tubercle slightly elevated above mesepisternum.

Variation in paratypes. Little variation was observed in the paratype series. The humeral stripe can be paler than the one figured for the male and old males have a dusting of pruinosity on sides of thorax. Pterostigma surmounting 1 cell in males (N = 9), 1–1.5 in females (N = 2); postnodals: Fw 11–13 in males, 12–13 in females, Hw 9–12 in males, 10–11 in females; postquadrangular cells Fw 2–3, Hw 2–3 in males, Fw 3, Hw 3 in females; RP 2 at Fw 5–7, Hw 4–5 in males, Fw 6, Hw 4–5 in females. Dimensions. ♂: Hw 21.1 ± 0.06 [19.9–21.9], abdomen 28.8 ± 0.09 [19.9–29.9], total length 36.9 ± 1.1 [35.2–38.7]; ♀: Hw 21.3 ± 1.0 [20.7–22.5], abdomen 25.0 ± 0.03 [24.7–25.2], total length 32.8 ± 0.05 [32.3–33.2].

Diagnosis. This species is superficially similar to the sympatric A. cuspidata but differs by morphology of the caudal appendages, thoracic and abdominal markings in the male, and morphology of the mesostigmal lamina in the female. Male cercus of A. acridens is broadly convex at basal half ( Figs. 103a, e, c ) and terminates in an acuminate ventromesally directed tooth ( Fig. 103b, c, d ). Male cercus in A. cuspidata has a largely linear carinate ridge basomedially ( Figs. 106a, c ) and the terminal tooth is subapical, broadly rounded apically and is directed ventrally ( Fig. 106b, c, e ). The torus in A. acridens is elongate occupying the entire ventral margin ( Fig. 103a ), not confined to the apicoventral margin as in A. cuspidata ( Fig. 106a ). Thoracic patterns in A. acridens tend to mirror those of A. cuspidata but the dark humeral stripe in A. acridens ( Fig. 9 ) tends to be lighter and in some specimens is distinctly paler than the black middorsal stripe; in A. cuspidata , the humeral stripe is usually as dark as the black middorsal stripe ( Fig. 13 ). Greater differences are found on abdominal S3, 8–9 as follows: Dorsal pale area on S3 of A. acridens is restricted basally as a small narrow posteriorly directed stripe (Fig. 34); in A. cuspidata , the pale dorsal stripe is broader, largely parallel and ends abruptly at apical fourth (Fig. 45). S 8–9 in A. acridens is entirely pale dorsolaterally (Fig. 35); pale areas in A. cuspidata are restricted (Fig. 46) or entirely (Fig. 47) black with pale areas limited to lateral portions of S8 and dorsal blue spot not reaching apical fourth (Figs. 46–47) on S9.

Females of both species are more similar in terms of body markings and they differ in the morphology of the mesostigmal plate. An elongate raised anteriorly directed tubercle confined to the medial half of the mesostigmal lamina characterizes A. acridens ( Fig. 69 ); no such tubercle is present in A. cuspidata , this area instead forming a slight concavity with a gently raised area directly posterior to medial margin of the mesostigmal plate ( Fig. 72 ).

Habitat. Apparently confined to seepages associated with larger rivers and creeks. A pair collected by S. W. Dunkle was found at a "stream and ditch near a golf course" with the habitat characterized as "shallow water flowing over a rock face." Jim Johnson (pers. comm. 9 Dec. 2017) photographed and collected this species at "....a vegetated cliff with water dripping off of it. This was along one side of a road, and close to a high gradient stream that flowed under the road. The adults perched on vegetation along that cliff, and my recollection is that it was in shade when we found them, although I am not completely positive about that."

Distribution. As far as known endemic to Ecuador, restricted to Esmeraldas, Manabí and Santo Domingo de los Tsáchilas Provinces west of the Andes ( Fig. 136 ).

Figures

FIGURES 9–13. Color pattern of male head, thorax, and S1–4. Head, dorsal view, thorax and S1–4, lateral view.

FIGURES 103–106. Male caudal appendages. (a) lateral view; (b) dorsal view; (c) mediodorsal view; (d) posterior view; (e) ventral view.

FIGURES 69–72. Female mesostigmal plates. (a) dorsal view; (b) detail of mesostigmal lobe, dorsal view; (c) frontal (anterior) view; (d) detail of mesostigmal lobe, posterodorsal view (on edge).

FIGURES 89–93. Genital ligula. (a) lateral view; (b) ectal view; (c) entolateral view.

FIGURES 23–27. Color pattern of female. Head, thorax, and S1–4 (23, 24, 26, 27); pterothorax (25). Head, dorsal view, thorax and S1–4, lateral view.

FIGURES 136–137. Distribution of new Argia species and closest congeners in Ecuador.