Description of the last instar larva of Erythrodiplax paraguayensis (Anisoptera: Libellulidae)

Descripción del último estadio larval de Erythrodiplax paraguayensis (Anisoptera: Libellulidae)

Muzón, Javier and Analía Garré

Instituto de Limnología "Dr. Raúl A. Ringuelet", C.C. 712, 1900 La Plata, Argentina; e-mail: muzon@ilpla.edu.ar

ABSTRACT. The last instar larva of Erythrodiplax paraguayensis (Förster) is described and illustrated, based on Iberá (Corrientes, Argentina) specimens. A comparative analysis of all hitherto known larvae from Argentina is provided.

KEY WORDS. Taxonomy. Odonata. Erythrodiplax paraguayensis. Larvae.

RESUMEN. Se describe e ilustra por primera vez al último estadio larval de Erythrodiplax paraguayensis (Förster) sobre la base de especímenes recolectados en los esteros del Iberá (Corrientes, Argentina). Se brinda además un análisis comparativo de las larvas de especies citadas en la Argentina.

PALABRAS CLAVE. Taxonomía. Odonata. Erythrodiplax paraguayensis. Larva.

INTRODUCTION

The American genus Erythrodiplax Brauer is mainly neotropical in distribution. It is composed by more than 50 species, 21 of which are presently known from Argentina (Muzón & von Ellenrieder, 1998). At present, the last instar larva of 18 species has been described (Santos, 1988; von Ellenrieder & Muzón, 2000; Needham et al., 2000; Costa et al., 2001), from which 10 are found in Argentina, i.e. E. anomala (Brauer), E. basalis (Kirby), E. fusca (Rambur), E. juliana Ris, E. latimaculata Ris, E. lygaea Ris, E. melanorubra Borror, E. nigricans (Rambur), E. ochracea (Burmeister) and E. umbrata (Linnaeus). Von Ellenrieder & Muzón (2000) provided a comparative table for the larvae of the known species; later Costa et al. (2001) re-assigned the larval description given by Carvalho et al. (1991) for E. connata to E. fusca and provided a key for the Brazilian species.

Erythrodiplax paraguayensis (Förster) has a large distribution area in South America, ranging from Venezuela to Argentina (Borror, 1942). It is an inhabitant of lentic environments in northeastern and central Argentina (from Misiones and Chaco to Buenos Aires and Córdoba provinces) (Muzón & von Ellenrieder, 1998). Its larva was cited as described by Costa et al. (2000); nevertheless Costa et al. (2001) established later that it is at present not described.

The aim of this contribution is to give a description of last instar larva of Erythrodiplax paraguayensis (Förster) and compare it with all the larvae described.

MATERIAL AND METHODS

Material examined. ARGENTINA. Corrientes, Colonia Pellegrini, laguna Iberá, 28°32´16´´S, 57°11´12´´W, 2/9-X-2004, coll. Garré & Lozano, 1 male (reared) [emergence 24-X-2004]; Estancia El Dorado, esteros del Iberá, 28°44´34´´S, 58°07´36´´W, 20/21-II-2003, coll. Muzón & Pessacq, 1 male. The specimens are deposited in the Collection of the Departamento Científico Entomología, Museo de La Plata, Argentina. Synonymic list includes original description and records from Argentina.

RESULTS

Genus Erythrodiplax Brauer

Diagnosis of larvae. Body without long hairs (except on prothorax); head longer than thorax; antenna third segment the longest; mandibles with four incisives, molar teeth variable (2-4) but never with molar crest; prementum distal margin obtuse and crenulated; abdomen without dorsal hooks (some species with middorsal tubercles bearing tufts of hairs); lateral spines on abdominal segments VIII-IX (also on VII in some species); epiproct, paraprocts and cerci recurved ventrad (except E. umbrata).

Erythrodiplax paraguayensis (Förster)

Diplacodes paraguayensis Förster, 1904: 4 (Type locality: Costa Aquaray).
Erythrodiplax minuscula (Rambur). Calvert, 1906: 249, 267, in part (Argentina); Ris, 1911: 483, 524, in part (Corrientes, Misiones); Ris, 1913: 90, 97 (Chaco, Corrientes and Misiones); Navás, 1927: 22 (Córdoba); Rodrigues Capítulo & Muzón, 1987: 128 (E. Ríos); Rodrigues Capítulo & Muzón, 1989: 150 (E. Ríos).
Erythrodiplax paraguayensis (Förster). Borror, 1942: 152-154 (new comb., redescription, Corrientes and Misiones); Rodrigues Capítulo & Muzón, 1990: 106 (Chaco, Corrientes and E. Ríos). Muzón & von Ellenrieder, 1998: 24 (Bs.As., Chaco, Córdoba, Corrientes, E. Ríos and Misiones).

Description of the last instar larva (Figs. 1-7)

Fig. 1-7. Last larval instar of Erythrodiplax paraguayensis. 1, rigth mandible, inner view; 2, left mandible, inner view; 3, prementum, dorsal view (left palp without setae); 4, Labial palp, dorsal view; 5, lateral spines on terga VIII-IX, dorsal view; 6, terminalia, lateral view; 7, terminalia, dorsal view. Scales 0.5mm, (in Figs. 1 and 4-7 as in Fig. 2).

Head. Pale, with diffuse dark pattern on dorsum, setose; 2.4 times as wide as long. Occiput with four pale strips, posterior margin concave. Mandibular formula according to Watson (1956) (Figs. 1-2): L 1 2 3 4 0 a b / R 1 2 3 4 y a b d. Labium (Fig. 3-4) reaching caudad to second coxae; prementum pale, anterior margin slightly crenulated with 18 or 19 setae, ligula obtuse, ratio of maximum width to maximum length 1, lateral setae 10 (1.3 mm the longest). Labial palp with minute black spots and a large one on the inner angle, with 7 or 8 setae; anterior margin slightly crenulated with 10 or 11 setae, inner margin no crenulated with nine setae.
Thorax. Pale; prothorax with a mid-dorsal diffuse black spot. Wing pads reaching caudad to abdominal segment VII; femora with two annular dark bands, one subbasal and one subapical.
Abdomen. brownish, with a middorsal pale stripe in segments VIII-X and epiproct; lateral spines on segments VIII and IX brown with a transverse pale stripe at 0.3 from base, ratio of spine length to maximum length of corresponding segment 0.4 / 0.33 (reared specimen) and 0.62 / 0.5 (reared specimen) respectively (Fig. 5). Paraprocts (Figs. 6-7) nearly five times as long as segment X; ratio relative to paraprocts: epiproct 1, cerci 0.61. Epiproct wide at the base, apex acute. Paraprocts, epiproct and cerci tips slightly recurved ventrad.
Measurements (exuviae in brackets, if different) (mm): Head maximum length: 1.4 [1.5]; head maximum width: 3.4 [3.6]; prementum maximum length: 2.3 [2.5]; prementum maximum width 2.4 [2.5]; labial palp maximum length: 1.6 [1.7]; movable hook length 0.5; inner wing pads: 3.7; length of femora: I, 1.7 [1.9]; II, 2.1 [2.3]; III, 2.75 [2.8]; length of tibiae: I, 1.9 [2.1]; II, 2.2 [2.4]; III, 2.95 [3.3]; length of abdominal terga: VI, 0.55 [0.65]; VII, 0.5 [0.6]; VIII, 0.5 [0.6]; IX, 0.4 [0.5]; X, 0.15; width of abdominal terga: VI, 3.4 [4.3]; VII, 3.4 [4.1]; VIII, 3.1 [3.7]; IX, 2.1 [2.7]; X, 1.1 [1.3]; lateral spines on abdominal segment VIII: 0.2; on segment IX: 0.25; cerci: 0.5; paraprocts: 0.7; epiproct: 0.7.

DISCUSSION

The current knowledge of the immature stages of the genus Erythrodiplax is still scarce, with only a third of its species presently known from the larval stage. Considering that most of the larval descriptions were made on non Argentinean specimens, and that the larvae of many of the species sympatric with E. paraguayensis in Argentina are still unknown, the elaboration of a useful regional key is not yet possible. Nevertheless, Costa et al. (2001) provided a key to the Brazilian species including all the known larvae recorded from Argentina. In order to include E. paraguayensis in that key we propose a modification from couplet 7, as follows:

7. Labial palp with 7 - 9 setae.......................................................... 9

7´. Labial palp with 6 setae.......................................................... 8

8. Two setae at the labial palp articulation..........................................................E. basalis

8´. Three setae at the labial palp articulation..........................................................E. fusca (in part)

9. Two setae at the labial palp articulation..........................................................10

9´. Three setae at the labial palp articulation..........................................................12

10. Cerci in dorsal view as long as or longer than 0.5 epiproct length. Labial palp with 7-8 setae. Prementum with 10-11 setae.......................................................... 11

10´. Cerci in dorsal view shorter than 0.5 epiproct length. Labial palp with 9 setae. Prementum with 12. setae..........................................................E. ochracea

11. Labial palp with 7 setae. Prementum with 11 setae. Spines on abdominal segments VIII-IX long (0.4 mm)..........................................................E. melanorubra

11´. Labial palp with 8-9 setae. Prementum with 10. setae. Spines on abdominal segments VIII-IX short (0.2- 0.25 mm)..........................................................E. paraguayensis

12. Epiprocts shorter than paraprocts..........................................................nigricans

12´. Epiprocts as long as paraprocts.......................................................... E. fusca (in part)

The information provided in the descriptions and redescriptions of the Argentinean Erythrodiplax larvae shows uniformity of metric and morphological characters, being the distinction between species very difficult (Tables I-II). The last larval instar of E. paraguayensis is similar in size to E. basalis and can be distinguished from it by the number of labial palp setae, the mandibular formula and short lateral spines of abdominal segments VIII-IX (see Tables I-II). It can be distinguished from the other hitherto known Argentinean species by its smaller size and by the number of labial palp setae (from E. ochracea and E. umbrata), the number of prementum setae (except from E. fusca, E. latimaculata and E. lygaea) and the mandibular formula (except from E. nigricans) (see Tables I-II).

Table I. Head main characters of the last larval instar of Erythrodiplax species recorded from Argentina. Additional sources: 1 Venezuelan specimens cited by Limongi, 1991; 2 Klots, 1932; 3 Needham & Westfall, 1955; 4 Calvert, 1928; 5 Costa et al., 2001; 6 Carvalho et al., 1991; * based upon the description's figures.

Table II. Thorax and abdomen main characters of the last larval instar of Erythrodiplax species recorded from Argentina. Additional sources: 1 Venezuelan specimens cited by Limongi, 1991; 2 Klots, 1932; 3 Needham & Westfall, 1955; 4 Calvert, 1928; 5Costa et al., 2001; 6 Carvalho et al., 1991; *based upon the description’s figures.

ACKNOWLEDGEMENTS

We thank very much to Natalia von Ellenrieder for their critical reading of the manuscript. This work was partially financed by The National Geographic Society project # 7104-01.

LITERATURE CITED

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Recibido: 10-III-2005
Aceptado: 16-V-2005