Macrothemis heteronycha ( Calvert, 1909 )

Costa, Janira M., Carriço, César & Santos, Tatiana C., 2010, Description of the final instar of Macrothemis heteronycha (Calvert) (Anisoptera: Libellulidae), Zootaxa 2506, pp. 65-68 : 65-67

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) .

Figures

FIGURE 1 – 11. Macrothemis heteronycha: (1) larva, dorsal view; (2) antenna; (3) labium; (4) labial palp; (5) left mandible; (6) right mandible; (7) prothoracic process; (8) abdomen, lateral view; (9) caudal appendages, dorsal view (10) Macrothemis inacuta, labial palp (after Novelo-Gutiérrez & Ramirez, 1998), (11). Macrothemis pseudimitans, labial palp (after Limongi, 1989).