Macrothemis tenuis Hagen 1868
Creators: name: Salgado, Luiz Gustavo Vargas
name: Carvalho, Alcimar Do Lago
name: Pinto, Ângelo Parise
Publisher: name: Zenodo
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Odonata
Libellulidae
Macrothemis
Macrothemis tenuis

description: Macrothemis tenuis Hagen, 1868
(Figures 30–38, 41)
Material. BRAZIL, Rio de Janeiro State: Itatiaia municipality, [district of] Maringá, Rio Preto (roots and litter) [22o19’37.73’’S, 44o34’41.36’’W; 1,107 m a.s.l.], 17.IX.1996, Equipe Entomologia UFRJ leg., 2 ̩ F-0 and 2 Ƥ F- 0, emergence dates unknown. All in DZRJ.
Larva similar to M. imitans imitans described above, differing by the following features: Integument without setae especially long or concentrated.
Head (Figs. 30–34). About 1.5x as wide as long in dorsal view; occipital lobes covered with short spiniform and robust long filiform setae. Frons with a group of short spiniform setae between antennae. Occiput bearing short robust setae. Proportional length of antennomeres: 30, 60, 100, 40, 35, 35, 35. Mandibular formula L 1234 y- abb’ R 1234 y abd or abdd’ (Figs. 30–31); left mandible: molars and incisors with obtuse apex, size b+d>a or dd’>a, size 3>4>1>2, prominence 3>4>1>2, y- poorly developed obtuse; right mandible: a and b with acute apex, d or dd’ and incisors with obtuse apex, size d>b>a or dd’>b>a, size 4>1>3>2, prominence 4>1>3>2, y with obtuse apex. Labium when folded reaching the level between pro- and mesocoxae; Prementum longer than wide in ventral view (Fig. 32); ligula projected 0.4, forming an angle of about 85º; margin of ligula bearing setae with truncate apex, 10 of these distinctly larger. Labial palp with 6 palpal setae (Fig. 33); proximal portion with setella and a group of 6–10 short spiniform setae; proximal half of outer margin with a row of about 6–8 short and robust setae; distal margin with 11 obsolete crenations (almost straight) (Fig. 34); central crenations with 5–7 setae, 3–4 in those closest to outer margin; setae of crenations truncate; inner margin with a row of about 25 setae.
Thorax. Pronotum with short setae; central area with a pair of nipple-like processes with rounded base; posterolateral margins with expansions with concentrations of short claviform setae; inverted “V” spot distinct both in exuviae and larvae. Prothoracic pleural processes with acute apex directed forward with a group of long and short spiniform setae. Legs with few robust setae; femora with row of short and robust setae concentrated in anterior surface; metathoracic femora when directed posteriorly reach posterior limit of S5 tergite; metatibiae when flexed on femora reaching distally the level of proximal half of trochanter; tibiae and tarsi of 3 pairs with 2 parallels rows of simple setae ventrally, extended to the distal middle of tibiae to the third segment of tarsi.
Abdomen (Figs. 35–38). About 2x longer than maximum width (S6); dorsal hooks on S2–9 large and with obtuse apex, S2 tubercle-like (Figs. 35–36); tergites with concentrations of spiniform setae on lateral margins decreasing in size gradually toward apex of abdomen; posterior borders of tergites of S1–5 bearing filiform short setae regularly distributed, those of S5 short and robust with obtuse apex in their 0.17 of lateral extension; posterior borders of tergites of S6–9 with short and robust setae with obtuse apex and S10 with few spiniform setae; lateral spines on S8–9, as long as 0.27 and 0.45 median dorsal length of respective segment; posterior border of sternum of S9 without a row of filiform long setae. Paraprocts with long, thin setae laterally.
Measurements (in mm; n=4). Total length 17.73–19.09; head mediodorsal length 2.17–3.34; head max. width 4.67–4.96; antenna total length 1.22–1.55; length of antennomeres 0.13–0.22, 0.20–0.29, 0.33–0.43, 0.15–0.19, 0.15–0.17, 0.13–0.19, 0.15–0.22; prementum length 3.91–4.44; prementum max. width 3.21–4.00; hind wing sheath length 4.75–5.42; metafemur length 4.67–5.50; metatibia length 5.30–5.96; abdomen length (incl. appendages) 7.57–8.75; abdomen max. width (S6) 4.90–5.69; epiproct length in lateral view 0.87–1.02; paraproct max. length in lateral view 0.65–0.80; cercus length in lateral view 0.61–0.71.
Diagnosis. The F-0 larva of M. tenuis cannot be correctly identified as Macrothemis in all the keys examined (Tables 1–2), being wrongly identified as Dythemis in the majority of them, but also as Brechmorhoga (Costa et al. 2004) and Gynothemis (Carvalho et al. 2002). The main feature that approximates this species, as well as M. hahneli, to those of Dythemis is the distal border of the labial palps with distinctly obsolete crenulations, a character not exclusive of this genus. However, it can be easily distinguished from all Dythemis larvae by the shape of its dorsal hooks (Dythemis features in brackets): present on S2, tubercle-like [absent]; large and with obtuse apex [large or short but with acute apex] on S3–9 (Figs. 35–36). The following combination of characters will separate it from the other described Macrothemis larvae: antennomeres 5–7 distinctly shorter than half of 3; left mandible with tooth y reduced; ligula very prominent, with lateral margins forming an angle of ca. 85o (Fig. 34); rows of premental setae not clearly divided in two groups; crenations of distal margin of labial palps obsolete; setae of distal margin of labial palps cylindrical; lateral spines of S9 straight; dorsal hooks on S2–9 large and with obtuse apex, S2 tubercle-like (Figs. 35–36).
description: Published as part of Salgado, Luiz Gustavo Vargas, Carvalho, Alcimar Do Lago & Pinto, Ângelo Parise, 2013, Larval taxonomy of Macrothemis Hagen, 1868 (Odonata: Libellulidae), with descriptions of four larvae and a key to the fourteen known species, pp. 229-245 in Zootaxa 3599 (3) on pages 238-241, DOI: 10.11646/zootaxa.3599.3.2, http://zenodo.org/record/216117