Argia claussenii Selys, 1865

F-0 exuviae of Argia claussenii Selys, 1865 View in CoL

Figs. 1−5 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5

Material examined. 3 F-0 exuviae (3 ♂♂ emerged in laboratory), BRAZIL, Minas Gerais state, Parque Estadual do Pico do Itambé, Rio Vermelho (18°23’14.8” S 43°18’14.3” W, 1178m asl), collected and emerged between May–Sep 2024, T.M. Dias-Oliveira leg., CBVS GoogleMaps .

Description. Exuviae light brown with lighter colors towards apex of legs ( Fig. 1a View FIGURE 1 ); slender; femora dark brown with pale bands; caudal gills dark brown with pale apical spots, laminar, 39% (medial) and 47% (lateral) of total body length ( Figs. 4 View FIGURE 4 c−d).

Head. Roughly rectangular, 0.51 as long as wide, wider than the thorax and abdomen ( Fig. 1a View FIGURE 1 ). Occipital margin concave; cephalic lobes rounded, bulging at postocular portion, with>20 short spines ( Fig. 1b View FIGURE 1 ). Antenna ( Fig. 1c View FIGURE 1 ) long and filiform, 7-segmented, segments light-brown colored, pale at the joints, 3rd antennomere longest, proportional lengths of antennomeres: 0.31, 0.5, 1, 0.77, 0.47, 0.27, 0.15. The compound eyes were rounded and laterally prominent ( Fig. 1a View FIGURE 1 ). Mandibles formula R 1234 y a / L 1+2345 ab, ( Fig. 2a View FIGURE 2 ). Maxilla: galeolacinia with seven teeth (one dorsal very short), four of them in the dorsal portion slightly incurved, with a basal row of minute setae; three ventral teeth of different sizes and robustness being the basal one roughly vestigial, with a patch of basal setae ( Fig. 2b View FIGURE 2 ). Prementum ( Figs. 1 View FIGURE 1 d−e) roughly pentagonal, longer than wide, lateral margins nearly straight, laterodorsally with a row of>15 spiniform setae; ligula tip very prominent, tapering to rounded apex, finely crenulated ( Fig. 1e View FIGURE 1 ); one nearly transparent premental setae on each side; basal row of>8 setae on each side. Labial palp with one palpal seta; two teeth, both smaller than movable hook, medial (outer) longest, with hooked apex; inner teeth about 0.6 length of medial teeth; movable hook slightly 0.4 labial palp length, with acute apex ( Figs. 2 View FIGURE 2 c−d).

Thorax. Brown, darker on the sutures, subtrapezoidal; anterior and posterior wing sheaths reaching anterior margin of S4 (not stretched individuals) ( Fig. 1a View FIGURE 1 ). Legs dark brown with pale bands, tip of metathoracic tarsi almost reaching S10 when extended; dorsal and ventral borders of femora with a row of spiniform setae (>15 pro-,>20 meso-, and>20 on metafemur); tarsi <0.50, length of tibiae, with two ventral rows of setae and claws with acute apex ( Fig. 3 View FIGURE 3 ).

Abdomen. With several minute spines, most prominent on dorsal and lateral surfaces; S2–7 with disrupted pale stripe on the midline ( Fig. 1a View FIGURE 1 ). In the lateral view, male gonapophyses sharply pointed, posteriorly directed, reaching basal 1/2 of the S10 sternum, bearing>20 spines each ( Figs. 4 View FIGURE 4 a−b). Caudal gills 2 (medial) 2.7 (lateral) times longer than widest part; ventral and dorsal margin of lateral gill covered with minute setae; dorsal margin of median gill covered with minute setae, ventral margin with sparse setation on first 1/2, remainder covered with small setae ( Figs. 4 View FIGURE 4 c−d). Cerci conical.

Measurements. AL: 8.1; Pfl: 2.5; MsfL: 3.8; MtfL: 4.2; TL: 14.2 (without gills).

Diagnosis. The larva of A. claussenii belongs to the first group proposed by Novelo-Gutierrez (1992) according to the premental ligula and number of palpal setae. This group is composed of species in which the larvae present a very prominent premental ligula. In Brazil, the only species with this condition are A. insipida and A. reclusa . From these species, the larvae of A. claussenii can be separated by the following character combination ( A. insipida and A. reclusa in parenthesis): male gonapophyses sharply pointed (quite rounded with a blunt apex in A. insipida ; similar to A. reclusa ), medial (outer) teeth of labial palp with hooked apex (nearly straight apex in A. insipida ; similar to A. reclusa ); basal row of>8 setae on each side of prementum (bearing three setae on each side in A. insipida ; no setae on A. reclusa ); “b” tooth on left mandible present (absent in A. insipida and A. reclusa ). The imago of A. claussenii was confirmed by comparing its anal appendages, genital ligula and overall thoracic pattern with unpublished photos and drawings provided by R. Garrison ( Fig. 5 View FIGURE 5 ).

Habitat and biology. The study area is characterized by cerrado vegetation, with patches of rupestrian field physiognomy. Adults were found flying along the course of waterfalls (in a 2 nd order river, with a rocky bed) in Vermelho River, perched on the edges of marginal vegetation and even on exposed rocks within the watercourse, as observed by Lencioni (2006). The larvae were found associated with these environments, especially in places with calmer and reddish waters and accumulated fallen leaves, which served as support for them ( Figs. 6 View FIGURE 6 a−b). They also used an angiosperm from the Podostemaceae family for the same purpose.