Comprehensive description of new and known stages of Americabaetis titthion Lugo-Ortiz & McCafferty (Ephemeroptera: Baetidae) Author Amaral, Igor Ferreira 0009-0000-4825-6804 Programa de Pós-graduação em Entomologia, Departamento de Entomologia, Universidade Federal de Viçosa, 36570 - 900, Viçosa, MG, Brazil & Museu de Entomologia, Departamento de Entomologia, Universidade Federal de Viçosa, 36570 - 900, Viçosa, MG, Brazil igor.f.amaral@ufv.br Author Salles, Frederico Falcão 0000-0001-8331-5929 Museu de Entomologia, Departamento de Entomologia, Universidade Federal de Viçosa, 36570 - 900, Viçosa, MG, Brazil frederico.salles@ufv.br text Zootaxa 2024 2024-11-04 5536 2 305 314 http://dx.doi.org/10.11646/zootaxa.5536.2.6 journal article 10.11646/zootaxa.5536.2.6 1175-5326 14033712 3B7164FB-7BC5-4D0F-9182-25F967A9B9C1 Americabaetis titthion Lugo-Ortiz & McCafferty, 1996 ( Figs 1–5 ) Americabaetis titthion Lugo-Ortiz & McCafferty 1996: 167 ; Francischetti et al. 2003: 69 ; Salles et al. 2004: 23 ; Domínguez et al. 2006: 72 ; Salles et al. 2010a: 302 ; Salles et al. 2010b: 26 . Diagnoses. Male adults (modified from Salles et al. 2004 ). 1) turbinate portion of eyes orange, separated by approximately the width of a lateral ocelli, upper surface ellipsoidal ( Fig. 1b ); 2) costal and subcostal area of fore wing tinged with reddish-brown (as in Fig. 2e ); 3) pairs of soft, setose protuberances present on meso- and metasternum ( Figs. 1a, c ); 4) subgenital plate slightly concave ( Fig. 1f ); 5) forceps brown, with segment I/II slightly tapering medioapically and segment III light brown ( Fig. 1f ). Nymphs (modified from Domínguez et al. , 2006 and Salles et al. , 2010b ). 1) frontal keel absent ( Fig. 4b ); 2) lingua broadly pointed apically ( Fig. 3g ); 3) labium with glossa 0.8× length of paraglossa ( Fig. 3i ); 4) apex of paraglossa with 3 rows of pectinate setae; 5) segment II of labial palp with a moderate distomedial projection ( Fig. 3i ); 6) meso and metasternum with a setose paired protuberance ( Fig. 4c ); 7) tarsal claw with 10–12 denticles; 8) posterior margin of abdominal terga with rounded spines ( Fig. 5d ). Descriptions Male imago ( Fig. 1 ). Lengths (in mm). Body: 6.0; Forewings: 5.9. Head ( Figs. 1a, b ). Brown, with cream lateral mark. Antenna light yellowish-brown, flagellum thickened at the base. Lateral and middle ocelli surrounded with black. Ventral portion of compound eye gray. Turbinate eyes separated approximately by the width of lateral ocellus; upper surface ellipsoidal and orange, except for brown edges; basal ⅓ of stalk brown, remainder cream. Thorax ( Figs. 1b, c ). Pronotum brown with lateral margin cream. Mesoscutum predominantly brown; anteronotal protuberance with lateral cream mark; anteronotal transverse impression and medioscutum dark brown; sublateroscutum with anterior portion cream; scuto-scutellar impression cream. Katepisterna brown with cream spot; meso and metasterna light brown, both with pair of triangular protuberances covered with small setae. Wing. Forewing hyaline (as in Fig. 2e ); costal, subcostal and basal area reddish-brown, more pigmented between Sc and RA; veins yellowish-brown; stigmatic area with 8–9 short veins, some incomplete; marginal intercalary veins paired, except between ICu2 and A. Legs. Foreleg 5.1 mm ; coxa brown with cream marks; trochanter, femur, tibia and tarsi brown; tarsus segments in decreasing order: 2, 3, 4, 5, 1; mid and hindleg similar, cream; tarsal segments II, III and IV with ventral projection. Abdomen ( Figs. 1d–f ). Segments I–X brown, VII–X with white inclusions (on terga VI–IX they are absent medially and on sigilla); tracheation black and well visible. Cercus broken-off and lost. Genitalia. Forceps predominantly brown, lighter towards apex. Forceps base with distomedial projection; forceps segment I tapering towards fusion with segment II; forceps segment III elongate; posterior margin of subgenital plate slightly concave. FIGURE 1a–f. Male imago of Americabaetis titthion . a. Head and thorax (lateral view); b. Head and thorax (dorsal view); c. Thorax (ventral view); d. Abdomen (lateral view); Abdomen (dorsal view); f. Genitalia. (Scale bars: 0.5 mm; white arrows indicate mesosternal and metasternal projection). FIGURE 2a–e. Female imago of Americabaetis titthion . a. Head and thorax (lateral view); b. Thorax (ventral view); c. Foreleg; d. Abdomen (lateral view); e. Right wing. (Scale bars: 0.5 mm; white arrows indicate mesosternal and metasternal projection). FIGURE 3a–h. Nymph of Americabaetis titthion . Nymph mouthparts. a. Labrum (dorsal view); b. Labrum (detail); c. Left mandible; d. Left incisors and prostheca; e. Right mandible; f. Right incisors and prostheca; g. Hypopharynx; h. Left maxilla; i. Labium. (Scale bars: 100 µm; black square in 3a indicates the detail in 3b). FIGURE 4a–f. Nymph of Americabaetis titthion . a. Habitus; b. Head (frontal view); c. Meso and metathorax (ventral view); d. Fore leg; e. Middle leg; f. Hind leg. (Scale bars: 1 mm). FIGURE 5a–f. Nymph and egg of Americabaetis titthion . a. Dorsal view of abdominal segments III–VI; b. Ventral view of abdominal segments VI–IX; c. Tergum VI; d. Detail of tergum IV; e. egg; f. chorion detail. (Scale bars: a, b: 1 mm; c, d: 100 µm; e: 10 μm; f: 2 μm). Female imago ( Fig. 2 ). Length (in mm). Body: 6.0; Forewings: 6.6. Head ( Fig. 2a ). Cream; antenna and lateral and middle ocelli similar to male imago; compound eye gray; posterior margin of head elevated. Thorax ( Figs. 2a, b ). Predominantly light brown; prothorax with lateral margin cream; anteronotal transverse impression and anterolateroparapsidal suture brown; apex of scutellum and scuto-scutellar impression cream; meso and metathorax sterna light brown; Wing similar to male; Legs ( Fig. 2c ). foreleg 2.6 mm , light brown, slightly longer than mid and hindleg; mid and hindleg similar to male, tarsal segments light brown. Abdomen ( Fig. 2d ). Cercus reddish-brown. Nymph. Length (in mm). Body: 7.00; Cerci: 3.8; Antenna: broken. Head ( Fig. 4b ). Labrum ( Fig. 3a, b ). 0.6× wider than long; dorsal surface with scattered short, fine, simple setae and pair of long, submedial simple setae; dorsolateral arc of setae composed of 6–9 + 1 long simple seta; ventral surface with 8–10 spine-like setae near lateral margin; lateral margin with short, fine, simple setae. Hypopharynx ( Fig. 3g ). Lingua longer than superlinguae, apex acute covered with fine setae; superlinguae expanded. Maxilla ( Fig. 3h ). Proximal inner margin of galealacinia with one row of 7–9 simple, fine setae. Labium ( Fig. 3i ). Glossa with 3–4 pectinate setae in distal outer margin; apex of paraglossa with pectinate setae. Abdomen. Gills II–V broader and larger than VI and VII, gills VII small and rounded ( Figs. 4a , 5a ); margins of sterna VII–IX with blunt spines ( Figs. 5b ). Eggs ( Figs. 5e, f ): Diameter: 51.5 µm; Height: 103.7 µm. Oblong; chorion with small irregular cells net-like. Micropyle unknown. Material examined: BRAZIL , Minas Gerais , Araponga , Pousada Remanso , 1 male imago and 2 female imagos; 20° 39’ 18’’ S 42° 27’ 12” W 1062 m .a.s.l.; 21/iii/2023 ; F.F. Salles col. BRAZIL , Minas Gerais , Araponga , Cachoeira do Boné , 2 nymphs ; 20° 38’ 45’’ S 42° 27’ 26’’ W 945 m . a.s.l.; 24/ix/2018 ; F.F. Salles ; D. Belicchi ; M.I. Passos ; J.F. Marulanda-Lopez cols. BRAZIL , Santa Catarina , São Joaquim , Rio Pelotas , 5 nymphs ; 28° 26’ 50.3’’ S 49° 52’ 58.3’’ W 936 m .a.s.l.; 31/viii/2009 ; N. Hamada ; P. Cruz ; R. Boldrini .