Description of the F- 0 exuviae of Argia claussenii Selys, 1865 (Odonata: Coenagrionidae) Author Dias-Oliveira, Tomás Matheus Graduate Program in Entomology, University of São Paulo, Ribeirão Preto, São Paulo, Brazil. Author Santos, Jean Carlos Ecology Department, Universidade Federal de Sergipe, São Cristóvão, Sergipe, Brazil. Author Souza, Marcos Magalhães De Federal Institute of Southern Minas Gerais state, Inconfidentes, Minas Gerais, Brazil. Author Vilela, Diogo Silva Federal Institute of Southern Minas Gerais state, Inconfidentes, Minas Gerais, Brazil. text Zootaxa 2025 2025-03-28 5613 3 577 584 https://doi.org/10.11646/zootaxa.5613.3.9 journal article 309364 10.11646/zootaxa.5613.3.9 f1a9095c-2de3-4ed8-a2a9-8dc21e889761 1175-5326 15216927 DE7E8740-A3A3-4479-A1D1-3831148F66BE F-0 exuviae of Argia claussenii Selys, 1865 Figs. 1−5 FIGURE 1 . Argia claussenii , F-0 exuvia: (a) dorsal view of habitus; (b) detail of cephalic lobe; (c) antenna; (d) prementum; (e) detail of prementum with open palps. 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 . Description. Exuviae light brown with lighter colors towards apex of legs ( Fig. 1a ); 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 c−d). Head . Roughly rectangular, 0.51 as long as wide, wider than the thorax and abdomen ( Fig. 1a ). Occipital margin concave; cephalic lobes rounded, bulging at postocular portion, with>20 short spines ( Fig. 1b ). Antenna ( Fig. 1c ) 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 ). Mandibles formula R 1234 y a / L 1+2345 ab, ( Fig. 2a ). 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 ). Prementum ( Figs. 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 ); 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 c−d). FIGURE 2. Argia claussenii , F-0 exuvia: (a) right and left mandibles; (b) maxilla; (c−d) labial palps. Thorax . Brown, darker on the sutures, subtrapezoidal; anterior and posterior wing sheaths reaching anterior margin of S4 (not stretched individuals) ( Fig. 1a ). 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 ). FIGURE 3. Legs of Argia claussenii , F-0 exuvia. Abdomen. With several minute spines, most prominent on dorsal and lateral surfaces; S2–7 with disrupted pale stripe on the midline ( Fig. 1a ). In the lateral view, male gonapophyses sharply pointed, posteriorly directed, reaching basal 1/2 of the S10 sternum, bearing>20 spines each ( Figs. 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 c−d). Cerci conical. Measurements. AL: 8.1; Pfl: 2.5; MsfL: 3.8; MtfL: 4.2; TL: 14.2 (without gills). FIGURE 4. Argia claussenii , F-0 exuvia: ventral (a) and lateral (b) views of male gonapophyses; lateral (c) and medial (d) 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 ). 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 a−b). They also used an angiosperm from the Podostemaceae family for the same purpose.