Neoneura ethela Williamson, 1917

Souza, Luiz Onofre Irineu De, Pepinelli, Mateus & Neiss, Ulisses Gaspar, 2012, The larva of Neoneura ethela Williamson, 1917 (Odonata: Protoneuridae), Zootaxa 3318, pp. 63-67 : 64

Neoneura ethela Williamson, 1917

Exuvia ( Figures 1 – 8 )

Material - Brazil, Goiás State, Caldas Novas Municipality. Rio Quente River, 17o46’24’’S 48o45’23’’W, 08.vi.2008 (M Pepinelli) – 1 male (reared), last-instar larva collected attached in a streamside vegetation (emerged in laboratory on 05.vii.2008).

Description - Overall color pale brown with two longitudinal darkish brown stripes; caudal lamellae blackish. Head - Wider than long, occiput concave; pale brown postocular lobes angulate, with small spiniform setae on posterior border ( Fig. 1 ). Antennae ( Fig. 8 ) long and slender, pale brown, paler at articulations; 7- segmented, the 3rd twice as long as 2nd and the 4th, three times as long as the 1st. Mandibles ( Figs. 4, 5 ) with stout teeth and the following mandibular formula: L 1+2345 0 ab; R 1+2345 y a. Prementum ( Fig. 2 ) broad triangular with one pair of premental setae; lateral border of prementum with 14 spiniform setae; anterior lobe slightly triangular with external margin finely denticulate. Articulation of prementum and postmentum situated between the first pair of coxae. Labial palp ( Fig. 3 ) with four setae; anterior border with two teeth on distal end, the external one short and rather bi-pointed and with the dorsal margin denticulate, the inner longer, curved and pointed; movable hook large and curved inward, about twice as long as the inner tooth ( Fig. 3 ).

Thorax – Pro-, meso- and metathorax hexagonal, with prominent lateral lobes and posterior margins almost straight; legs long, with short spines; femora with two dark bands, partially fused and forming a broad band; tibiae with a distinct dark band at the middle and with apical region enlargement darkness; margins of femora and inner side of tibiae with a row of short spines; wing pads reaching S5 ( Fig. 1 ).

Abdomen - Cylindrical, narrowing posteriorly; S3–9 marked with two darker longitudinal dorsal bands; S8–10 with a row of short spines along distal border ( Fig. 1 ). Gonapophyses triangular, apex bluntly pointed with posteromedial margin slightly concave, reaching just over the hind margin of S9. Cerci almost globe-shaped, 1/4 length of S10. Caudal lamellae ( Figs. 6, 7 ) long and foliate, tips acute; darker than body: basal portion sclerotized, dark brown and blackish markings on remaining thin part of lamellae; sclerotized basal part extending to 1/3 of dorsal margin and 1/2 of ventral margin; nodus marked with a dark crescent: nodus on median lamella situated at 1/3 and on lateral gills at the middle of the lamella length; lateral lamellae ( Fig. 7 ) with dorsal and ventral margins and lateral carina armed with a row of short spines on proximal end: four on dorsal margin, 24 on lateral carina and 24 on ventral margin increasing in size distally; median lamella ( Fig. 6 ) with dorsal and ventral margins and lateral carina armed with a row of short spines on proximal end: two on the dorsal margin, nine on lateral carina and five on ventral margin; principal and secondary tracheae amply visible, more on the anterior and median part.

Measurements (mm) - Total length 9.9 (without appendages); head length 1.8; head width 2.9; antennae total length 1.98; antennomere I 0.2, II 0.3, III 0.6, IV 0.45, V 0.2, VI 0.15, VII 0.08; length of prementum 1.8; basal width of prementum 0.7; maximum width of prementum 1.4; length of labial palp 1.1; width of labial palp 0.25; length of movable hook 0.5; anterior length of wing pads 3.9; posterior length of wing pads 3.4; femur I 1.8, femur II 2.5, femur III 2.9; tibia I 2.1, tibia II 2.1, tibia III 2.1; length of abdomen 5.5; maximum width of abdomen 1.4; length of median caudal lamellae 3.8; maximum width of median caudal lamellae 0.9; length of lateral caudal lamellae 5.2; maximum width of lateral caudal lamellae 1.1.

Bionomics - The larva of Neoneura ethela was collected from a thermal water river in Caldas Novas municipality which is one of the largest hydrothermal resorts in the world. The name Rio Quente ("Hot River") refers to its thermal waters. The bottom of the river is composed of stones and sand. Water flow is moderate; depth is 1 m and width is 3 m. The temperature of the water was about 35o C, one of the highest temperatures recorded for an aquatic insect in Brazil. This locality increases the geographical distribution of this species to the central region (Goiás state) of Brazil.

Discussion - All known larvae of South American species of Neoneura share these characters: antenna 7-segmented, one pair of premental setae (two in N. kiautai ), external tooth on labial palp short and truncated and the lamellar gill divided into a basal sclerotized part and a thin leaf-like apical part. A complete table of the diagnostic characters for the known larvae of Neoneura is available at Anjos-Santos et al. 2011. The number of palpal setae varies slightly: 4 in N. ethela , 3-4 in N. fulvicollis , 4 in N. kiautai and 4 (female) and 5 (male) in N. joana . The larva of N. ethela can be distinguished from all other South America larvae by the following combination of characters: one pair of premental setae, S8–10 with a row of short spines along distal border, lateral gills a little longer than length of abdomen, ventral border of lateral gill armed with a row of about 24 spines. Another two species, N. carnatica Selys and N. maria (Scudder) are endemic to Cuba, and their larva have been described ( Needham 1939, Westfall, 1964). They can be distinguished from the other four species cited above in having legs heavily fringed with long hairs. The key below can be used to distinguish the known larvae of South American Neoneura species; however, we recommend using it cautiously, as more than 80% of Neoneura species recorded for South America still remain with the larval stage unknown. To identify genera of Neotropical Protoneuridae , a key with comments is now available ( Neiss & Hamada 2012).

Figures

FIGURE 1. Neoneura ethela, last-instar exuvia, male, dorsal view.

FIGURES 2 – 8. Neoneura ethela, last-instar exuvia, male: 2) Labium, dorsal view; 3) Labial palp, teeth detail; 4) Right mandible, inner side; 5) Left mandible, inner side; 6) Median gill, lateral view; 7) Left lateral gill, lateral view; 8) Antennae.