Argia smithiana Calvert 1909

Cezário, Rodrigo Roucourt, Vilela, Diogo Silva & Guillermo-Ferreira, Rhainer, 2018, Final instar larvae of Argia mollis Hagen in Selys, 1865 and Argia smithiana Calvert, 1909 (Odonata: Coenagrionidae) from the Brazilian Cerrado, Zootaxa 4514 (1), pp. 137-144 : 140-142

Description of the final instar larvae of Argia smithiana Calvert 1909

Figs. 7–12 .

Material examined. 1 ♂ F0 exuvia ( Fig. 7a ): BRAZIL, Serra da Canastra , Rio do Peixe (20°25’68.89” S, 46°40’96.11” W), 14-xii-2017, Guillermo-Ferreira leg. , 1 ♂ (reared in laboratory).

Head. Approximately rectangular, wider than long, cephalic lobes convex, bulging and bearing small setae ( Fig. 7b ). Ventral margin of eyes at mandibles level. Antenna 7-jointed, longer than head, third antennomere being the longest, about as long as combined length of antennomere 1+2 ( Fig. 8 ); antennomere 1 ochre, 4–7 yellowish to pale; length of antennomeres: 0.19, 0.30, 0.46, 0.42, 0.24, 0.10, 0.08 ( Fig. 8 ). Prementum ( Fig. 9 a–c) 0.75 as wide as long, dorsal surface bare, ligula moderately prominent with small claviform setae ( Fig. 9a ); labial palp with two teeth, both smaller than movable hook, medial (outer) one the longest; 1 short palpal setae at base of movable hook ( Fig. 9b ); lateral row of 10 or 11 small setae ( Fig. 9c ). Mandibles with molar teeth but without molar crest, with the following formula: L 1234 0 b (1>3>2>4), R 1234 y 0 a (1>2>3>4) ( Fig. 10 ).

Thorax. Pronotum yellow, rounded, bearing no setae. Wing pads yellow with dark borders, extending up to segment 4. Legs yellow with weak dark annular spots, two on each femora and one on the mid portion of tibia ( Fig. 7a ).

Abdomen. Mostly yellow, with dark markings on S1–4 distal ring, S5–10 with dorsolateral spots, larger and darker from S7–10 ( Fig. 7a ). Cerci ( Fig. 11 a–b) rounded, with apparent small excavations in mediodorsal view ( Fig. 11a ); in lateral view with rounded tip, small concave dorsal excavation, pointed forwards ( Fig. 11b ); sternum S9 with 9 setae on its posterior half; gonapophyses blunt with one row of 4 claviform setae and 1 mediolateral setae on ventral margin; only surpassing to 25% of S10 length ( Fig. 11 c–d). Caudal lamellae ( Fig. 12 a–b) laminar (sensu Novelo-Gutierrez, 1992), narrow at base, foliaceous median lamella tip ( Fig. 12a ); lateral lamellae with a filamentous tip ( Fig. 12b ); both lateral and median lamellae dark with two transverse pale stripes interrupted medially; on lateral lamellae one at 50% and the other at 75% of its length; on median lamella at 30% and 60% of the length; median lamella shorter than lateral lamellae ( Fig. 12 a–b). Tip of lateral lamella missing a small part.

Measurements (n = 1). Total length without appendages: 13.57. Total length of head: 1.72; max.width: 3.21. Prementum length: 2.86; max. width: 2.1. Total length of labial palp: 1.24; max. width: 0.40. Femur I: 2.16; II: 2.69; III: 3.36. Tibiae I: 1.87; II: 2.00; III: 2.32. Inner wing pads: 3.9; external wing pads: 3.82. Medial caudal lamella: 3.3; lateral caudal lamella: 4.07.

Habitats: The larvae of A. smithiana was collected in a small section of the stream, among leaves that piles on the margins.

Remarks. Differential diagnosis. Argia larvae are commonly found inhabiting streams, rivers and palm swamps ( Vilela et al. 2016) and they are usually found among submerged vegetation, gravel and rocks (Novelo- Gutierrez 1992). The larvae of A. mollis and A. smithiana fit better on the second group proposed by Novelo- Gutierrez (1992) which comprises species with ligula moderately prominent (see Table 1). They differ from the five Brazilian hitherto described Argia larvae by the ligula shape: in A. insipida (described by Geijskes 1943), A. serva (described by Del-Palacio et al. 2018), A. sordida (described by Santos 1968) and A. croceipennis (described by Costa et al. 2008) the ligula is prominently convex and in A. pulla (described by Novelo-Gutierrez 1992) it is slightly prominent ( Table 1). Argia smithiana shares with A. insipida , A. croceipennis , A. mollis and A. serva the presence of only one palpal setae basal to the movable hook, whereas A. sordida has no palpal setae and A. pulla has two. Cerci of A. smithiana are similar to those of A. pulla by having a more forward orientation but differ from those of this species by exhibiting less conic apices and a slightly concave excavation on their dorsal portion. Argia croceipennis and A. sordida have bigger and rounded cerci. Argia mollis cerci are similar to A. croceipennis because they are short and rounded. Argia mollis shares with A. pulla bluntly pointed appendages. Argia sordida has short cerci with rounded apex. Argia mollis and A. smithiana share small excavations at the cerci in medio dorsal view. The cerci of A. insipida are undescribed. Final instar larva of A. smithiana can be further distinguished from that of A. insipida , one of the most similar species, by lacking spines on each side of prementum basal surface, having larger medial teeth in labial palp, mandibles lacking molar crest, bearing no setae and ventral portion of male gonapophysis bearing less setae. Argia smithiana also seems to be lighter in coloration in comparison to A. insipida , which has dark brown body coloration ( Geijskes 1943). Argia mollis can be distinguished from A. smithiana by the presence of two molar teeth in its left mandible and seems to be darker in coloration in comparison to A. insipida .

Figures

FIGURE 11a–d. Argia smithiana. 11a. mediodorsal view of F0 exuvia cerci, 11b. lateral view of right cercus, 11c. lateral view of F0 exuvia S9 and S10, 11d. ventral view of F0 exuvia gonapophyses.

FIGURE 12. Argia smithiana. Median and lateral lamellae of F0 exuvia.

FIGURES 7–10. Argia smithiana. 7a. F0 exuvia habitus, 7b. detail of cephalic lobe; 8. antenna; 9. prementum: 9a. detail of distal margin ligula, 9b. mediodorsal view of labial palp, 9c. lateral detail of setae; 10. right and left mandibles.