Macrothemis heteronycha (Calvert, 1909)

(Figures 1–9)

Material. Deposited in the Museu Nacional da Universidade Federal do Rio de Janeiro; Brazil, Rio de Janeiro, 22º14’31” S and 43º42’5” W, 6.III.2004 (alt: 249 m) B. Mascarenhas leg. Ultimate larval instar male emerged 23.III.2004. The exuviae were preserved in 80% ethanol, and adults were dried and preserved in envelopes.

Description. General shape of body typical of Libellulidae, similar to known larvae of Macrothemis (Costa et al.) (Fig. 1): Integument light brown, covered with small spiniform setae.

Head. Large, general shape rectangular, almost twice as wide as long in dorsal view (Fig. 1). Occipital margin concave (Fig 1); eyes large and prominent in dorsal view; cephalic lobes rounded, not bulging, covered with minute spiniform setae. Antenna small, 7-segmented, with third antennomere longest (Fig. 2). Labium small, triangular (Fig. 3), as wide as long, with 8 lateral setae on each side of dorsal surface (5 large, 3 small); ligula not prominent, finely crenulated along margin; articulation of postmentum at level of anterior margin of mesocoxa. Labial palps triangular with 5 setae (Fig. 4); movable hook of moderate size, thick, pointed, as long as palpal setae; distal margin of palps with 10 small crenulations, each bearing two to four smaller setae. Mandibles (Figs. 5, 6) with following formula (sensu Watson, 1956): L 1 2 3 4 ab/ 1 2 3 4 y abd.

Thorax. Pronotum slightly quadrate. Prothoracic processes large with six teeth in posterior margin (Fig. 7). Wing pads parallel extending to distal end of S6. Legs long, the hind leg surpassing distal margin of anal pyramid when extended to side of body, femora with a row of short stiff setae along dorsal margin and with one dark band near to the distal end (Fig. 1).

Abdomen. Ovoid, with dark mid-dorsal bands on S3; small spines on lateral margin of S8 and 9, S9 curved inward (Fig.1). Dorsal hooks present on S3–9, segment 3 small; those on segments 6–9 well developed, highest on S7, declining posteriorly (Fig. 8). Anal appendages short (Fig. 9), a little longer than S10. Epiproct surpassing distal end of paraproct; cerci short, not reaching mid-length of epiproct.

Measurements (in mm). Total length (with appendages) 12; Head length: 2.5; Femur I 2.5; II 3.0; III 3.5;Tibia I 1.8; II 2.3; III 4; Abdomen length 8.0, width 4.5; epiproct 0.7; cercus 0.4; paraproct 0.5.

Diagnosis. The larva of M. heteronycha can be distinguished from M. aurimaculata and M. inequiunguis (alternative state in parentheses) by absence of a dorsal hook on abdominal segment 2 (present), from M. pseudimitans, M. celeno, and M. inacuta by presence of 5 palpal setae and 9 palpal crenulations (6 palpal setae and 7 palpal crenulations, respectively) and from M. musiva by the following characters: palpal setae 5 (4 in M. musiva), cerci short not reaching to half-length of epiproct (large in M. musiva, surpassing mid-length of epiproct).

Biology. The larva of M. heteronycha was collected in a lowland river, ca 2-3 m wide and 0.5-1 m deep, with sandy bottom rich in organic material and marginal riparian vegetation, well-shaded. Other odonate larvae found and reared belonged to Progomphus complicatus Selys. At this site we collected adults of the following species that occur in the Rio de Janeiro State: Acanthagrion gracile (Rambur), A. lancea Selys, Homeoura chelifera Selys, Ischnura fluviatilis Selys, Oxyagrion hempeli Calvert, O. microstigma Selys, Telebasis filiola (Perty), Tigriagrion aurantinigrum Calvert, Coryphaeschna adnexa (Hagen), C. perrensi (McLachlan), Remartinia luteipennis (Burmeister), Diastatops obscura (Fabricius, 1775), Dythemis multipunctata Kirby, Erythrodiplax fusca (Rambur), E. juliana Ris, Macrothemis imitans Karsch, Miathyria marcella (Selys in Sagra), M. simplex (Rambur), Micrathyria artemis Ris, M. catenata Calvert, M. ocellata Calvert, Nephepeltia flavifrons (Karsch), Orthemis discolor (Burmeister), Perithemis mooma Kirby, Planiplax phoenicura Ris, and Tauriphila argo (Hagen) .