Argia chelata Calvert

Novelo-Gutiérrez, Rodolfo, 2013, Description of the larva of Argia chelata Calvert, 1902 (Odonata: Coenagrionidae), Zootaxa 3745 (4), pp. 479-485 : 480-484

Argia chelata Calvert

Figs. 1–9

Material. Two exuviae (♂ ♀, reared), 24 F-0 larvae (11 ♂, 13 ♀), 31 younger larvae (13 ♂ 18 ♀, most probably F- 3). MEXICO: Chiapas; Municipality of Angel Albino Corzo, Reserva de la Biosfera “El Triunfo” (15° 39’ 51’’ N; 92° 48’ 49” W, elevation 1979m asl, cloud forest), 14 May 2005, R. Novelo leg (2 ♀). Veracruz; Municipality of Coatepec, Río Pixquiac at Consolapa (19° 29’ 02” N; 96° 56’ 49” W, elevation 1239m asl, disturbed cloud forest), 15 May 2004, R. Novelo leg (1 ♀ 1 ♂ emerged on 20 May 2004 at 0 945 h and on 27 May 2004 at 0 730 h, respectively); Municipality of Banderilla, La Martinica Protected Natural Area (19° 35’ 39” N; 96° 57’ 00” W, elevation 1430m asl, cloud forest), R. Novelo leg (24 ♂ 30 ♀). All specimens deposited at Colección Entomológica del Instituto de Ecología, A.C., Xalapa (IEXA).

Description. A moderately robust larva ( Fig. 1 ), ground color brown to dark brown with light areas, legs with wide dark bands separated by narrow pale areas. Abdomen cylindrical; caudal lamellae mostly grayish-violet on basal 0.75, remainder variable but usually pale with an indefinite, transverse, whitish band.

Head: wider than long, posterior margin widely concave, dorsal color pattern as in Fig. 1 a. Cephalic lobes rounded with posterolateral margins bearing spiniform setae. Labrum yellowish brown, poorly setose; clypeus trapezoidal, light brown, with a pair of parallel, white narrow lines along middle third. Antennae 7-segmented ( Fig. 2 ), scarcely longer than head, basal half of scape brown, apical half creamy pale, sometimes totally pale, antennomeres 2–4 and basal half of 5 yellow to yellowish-brown, distal half of 5 and antennomeres 6–7 creamy pale; size proportion of antennomeres (from basal to apical): 0.4, 0.7, 1.0, 0.8, 0.5, 0.3, 0.15. Mandibles ( Fig. 3 ) with molar teeth but lacking molar crest, with following formula: L 1’1 2 3 4 0 a b / R 1’1 2 3 4 y a 0, both mandibles with a ventral and dorsal, transverse, row of setae; basal-external surface setose. Ventral pad of hypopharynx subrectangular ( Fig. 4 ), with a tuft of 3–4 long, robust setae located subapically to each anterolateral corner, and a transverse row of smaller setae on anterior margin. Maxilla: galeolacinia with 6 teeth, three dorsal teeth approximately of the same size, three ventral teeth of different sizes, apical one the longest, a row of stiff setae preceding both ventral and dorsal teeth. Labium creamy-pale. Prementum-postmentum articulation almost reaching basal half of mesosternum. Prementum 0.80 times as wide as long ( Fig. 5 ), with a row of 19–21 spiniform setae along distal half of lateral margins, and a group of 5–6 basidorsal spiniform setae of different size; ligula moderately prominent (3.3 times wider at its base than long, measured dorsally), with closely set, minute claviform setae on distal margin. Premental palp ( Fig. 5 ) with two end hooks shorter than movable hook, the ventral (medial) one longest, internal margin of palp finely serrate, external margin of smaller end hook with a row of minute, sharp denticles; setae on palp variable (N=24): with two long setae (45.8%), with two long setae plus one setella (45.8%) ( Fig. 5 ), with three setae (8.4%), an irregular row of 21–23 short, spiniform setae along dorsal margin; two stout, spiniform setae at base of palp articulation.

Thorax: pronotal disk mostly light brown with spiniform setae on anterodorsal surfaces, lateral margins dark brown, strongly convex, and covered with stout spiniform setae; propleura dark brown. Synthorax mostly dark brown with irregular pale areas on dorsum of mesepisterna, and dorsal half of mesepimera and metepimera ( Fig. 1 a). Wing sheaths mostly dark brown, with a transverse, pale band at basal 0.40 of their length, anterior pair reaching basal half of S5, posterior pair reaching posterior margin of S5. Legs rather long (i.e., tip of metatibiae surpassing well S10 when fully extended), pro- and mesotibiae longer than respective femora, metafemora and metatibiae of the same length. Femora with two large, wide, dark bands connected with each other by a thin line at middle, an incomplete basal and apical dark ring narrowly connected with the subbasal and subapical large dark band, respectively, the pale intervening spaces reduced ( Fig. 1 a); tibiae largely creamy pale, with a dark, wide, well-defined subbasal band and a basal, incomplete, dark ring; dorsal and ventral borders of femora, external surface of profemora, and internal and external borders of tibiae with robust spiniform setae, these spiniform setae intermingled with long, stiff setae on dorsal borders of femora and external borders of tibiae; apical-internal border of tibiae with some large, robust, reddish, spine-like setae intermingled with tridentate setae; tarsi creamy pale, with abundant, yellow, stiff setae on ventral surface, and long, delicate, whitish setae on dorsum; claws simple with pulvilliform empodium.

Abdomen: wider at base, reaching maximum width at S3 and then slightly and gradually narrowing caudally. Tergites with a variable complex color pattern ( Fig. 1 a), but mostly dark brown with five pale spots on S2–7 as follows: one laterobasal oval-shaped at each side, which in some individuals becomes a stripe along the total length of tergites, two submedian, triangular shaped spots with the base of triangle directed caudad, one triangular spot on midline with base of triangle directed basally, which in some individuals can be a mere pale line or stripe; S8–9 dark brown with a triangular pale spot on midline, S10 brown with a transverse, subrectangular, pale spot at middle and a triangular pale spot at each side of midline; S1 pale. Lateral margins of S1–6 expanded and folded ventrally forming a carina beset with small spiniform setae, slightly divergent caudally, not folded and straight on S7–10 with small spiniform setae; tergites 1–10 with small setae, posterior margin of S1–4 smooth, S5–10 with spiniform setae, scattered on 5 and increasingly abundant caudally. Sternites 1–7 mostly yellow-brown ( Fig. 1 b), brown laterally and on posterior margins, with a darker spot at middle of posterior margins; sternites 8–10 brown ( Fig. 1 b). Sternites 1–10 covered with small setae, sternites 8–10 with some scattered spiniform setae, posterior margins of 1–6 and middle third of 7 smooth, lateral thirds of posterior margin of sternite 7 and posterior margins of 8–10 with spiniform setae, stouter on 10. Male gonapophyses ( Fig. 6 ) pyramidal, with tips sharp, in ventral view ( Fig. 6 a) internal margins divergent, reaching basal 0.40 of sternite 10; ventral-external surface with 13–15 spiniform setae ( Fig. 6 b). Female gonapophyses ( Fig. 7 ) exceeding posterior margin of S10 by 0.50 length of S10; lateral valves, in ventral view ( Fig. 7 a), with tips pointed, ventral border with 7–9 stout, spiniform setae on basal 0.75; in lateral view ( Fig. 7 b) with 0–3 stout spiniform setae and several minute spiniform setae on external surface; median valves the longest, smooth. Male cerci short ( Fig. 8 ), roundly pointed ( Fig. 8 a), appearing globose in dorsal, dorsolateral, and ventral views ( Figs. 8 b – d). Female cerci more or less triangular in lateral view ( Fig. 8 e). Caudal lamellae ( Fig. 9 ) narrowing at both ends with moderately acuminate tips; most of lamellae with a more or less uniform grayish-violet coloration on basal 0.75, remainder variable but usually with an indefinite, transverse whitish band. Lateral lamella (paraproct) ( Fig. 9 a) moderately inflated (saccoid) on basal 0.65 on external side, apical 0.35 laminar, 2.8 times longer than its widest part; a lateral, longitudinal carina along the inflated part of lamella bearing stout, long, spiniform setae, this carina closest to the inferior margin of lamella than to the dorsal one; dorsal border with spiniform setae on basal 0.25, remainder smooth with sparse, small, white, delicate setae, ventral border with spiniform setae on basal 0.55, remainder fringed with white delicate setae. Central lamella (epiproct) ( Fig. 9 b) moderately inflated at basal 0.40 on both sides, 2 times and little more longer than its widest part; a very weak lateral carina on basal 0.10 at both sides of epiproct, bearing a row of spiniform setae; dorsal border with spiniform setae on basal 0.30, remainder fringed with white, delicate setae, ventral border with spiniform setae on basal 0.25, remainder with sparse, small, white setae, color pattern as in Fig. 8 b.

Measurements. Total length (without caudal lamellae) 12.1–15.8 (mean= 13.65; N=19); maximum width of head 4.0–4.3 (mean= 4.1; N=23); hind femur 4.1–4.8 (mean= 4.5; N=23); abdomen 6.5–8.9 (mean= 7.8; N=19); paraprocts (without tip) 6.0–6.6 (mean= 6.1; N=11); epiproct (without tip) 5.2–6.0 (mean= 5.5; N=10).

Habitat. Larvae of Argia chelata inhabit 2nd (width 1.5–2 m, depth 0.30–0.50 m approx.) to 4th (width 10 m, depth 0.40 m approx.) order shallow streams in cloud forest, crawling among debris, fine sand and mud where the water flow is slow or still, close to the shoreline.

Discussion

Argia chelata falls into the group of Argia larvae with moderately prominent ligula and two palpal setae (Novelo- Gutiérrez 1992) (although some specimens rarely present three setae in one palp). It shows a general resemblance to the group comprising A. lacrimans (Hagen) (Novelo-Gutiérrez 1992) , A. pima Garrison (Hoekstra & Smith 1999) , and A. tonto Calvert (Westfall 1990, Novelo-Gutiérrez 1992), sharing with them the following features [other species in square brackets]: a complex color pattern on legs and abdomen [ lacrimans , pima , tonto ]; the same proportion of antennomeres [ pima , tonto ]; the first 4 antennomeres of the same color [ pima , tonto ]; femora and tibiae with dark, wide bands [ lacrimans , pima , tonto ]; tergites variable but without a middorsal pale stripe [ pima , tonto ]; S10 mostly dark brown [ pima ]; male and female gonapophyses pyramidal, sharply pointed, beset with spiniform setae on ventral border [ lacrimans , pima , tonto ]; caudal lamellae mostly uniform grayish-violet [ tonto ]. Of all these species, the larva of A. chelata can be separated by the following combination of characters: labial palp with 2 setae plus one basal setella; length of ligula 30% of maximum width; basal tergites (1–5) lacking long, fine setae, mainly on midline; S8–10 mostly dark brown; paraprocts with spiniform setae on basal 0.25 and 0.55 of dorsal and ventral borders, respectively.

When Calvert (1902) originally described Argia chelata , he stated “this species is very similar to Argia lacrymans ....” At first glance, larvae of both species look very similar but with detailed examination they differ in several aspects [those of A. lacrimans in square brackets]: antennal scape yellow to light brown [creamy pale]; length of ligula 30% of maximum width [24%]; no pale stripe along middorsal line on abdomen, and long, fine setae lacking [a pale middorsal stripe with long, fine setae]; sternites 8–10 dark brown [yellow-brown with a pale V-shaped spot to each side of gonapophyses]; external surface of female lateral valvae with 0–3 stout spiniform setae [8–9 stout spiniform setae]; caudal lamellae variable but usually uniformly grayish-violet in most of their surface, with some white dots and spots on apical third [usually with a mottled aspect]. In summary, the larvae of Argia pima and A. tonto appear as the closest relatives of A. chelata .

Figures

FIGURE 1. Dorsal (a) and ventral (b) views of F 0 male larva of Argia chelata.

FIGURES 2 – 6. Details of larval morphology of A. chelata. 2) Left antenna, dorsal view. 3) Mandibles: a and b, right and left mandibles, respectively, ventrointernal view; c and d, Idem but ventral view. 4) Hypopharynx, ventral view. 5) Prementum, dorsal view. 6) Sternites 9 – 10 showing male gonapophyses: a, ventral view; b, lateral view.

FIGURES 7 – 9. Details of larval morphology of A. chelata. 7) Sternites 9 – 10 showing female gonapophyses: a, ventral view; b, lateral view. 8) Cerci: a, lateral; b, dorsal; c, ventral; d, dorsolateral (a – d male); e, female cerci, lateral view. Ce = cercus. 9) Caudal lamellae: a, lateral lamella, left lateral view; b, central lamella, left lateral view.