Cephalaeschna acanthifrons, Joshi & Kunte, 2017

Joshi, Shantanu & Kunte, Krushnamegh, 2017, Two new dragonfly species (Odonata: Anisoptera: Aeshnidae) from north-eastern India, Zootaxa 4300 (2), pp. 259-268 : 260-263

Cephalaeschna acanthifrons sp. nov.

( Figs. 1–2 )

Holotype. ♂ ( NCBS-AQ 279 ), collected between Ramalingam camp and Lama camp, Eaglenest Wildlife Sanctuary, West Kameng District, Arunachal Pradesh, India (precise GPS coordinates unknown); 30.IX.2015; Tarun Karmarkar & Subhajit Mazumder leg.

Paratype. ♂ ( NCBS-AQ 373 ), same locality and collectors as the holotype; date of collection: 4.X.2015.

Etymology. The name ‘ acanthifrons ’ means “pointed face”, derived form the Greek acanthi [=thorn], and Latin frons [=forehead]( Fig. 2 a,b).

Description of the holotype. Head. Eyes colored dark green. Labrum greenish yellow, postclypeus greenish yellow with two irregular rounded brown markings on the basal half. Anteclypeus, labium, mandibles dark brown. Frons greenish yellow basally. This color gradually changes to dark brown towards the border so that the greenish yellow is framed by the dark brown markings. Frons>1/2 width of the face, pointed at apex with a small dark black median ‘horn’, pointed anteriorly in dorsal view. Dark brown near the vertex and the sides. Vertex black, postgenae with yellow markings on both sides near the eye margin, base of the antennae dark brown.

Thorax ( Fig. 1 b). Prothorax yellow on sides along with propimeron; median lobe and posterior lobe dorsally dark brown; mesostigma with greenish yellow markings on the sides. Synthorax with vivid green and yellow markings; dorsal carina black with two green yellow spots at the antealar ridge; the paired dorsal stripes on the mesepisternum of uniform width, anterior 1/4th narrowing outwards; mesepimeron with a broad green stripe almost covering it entirely, marked with a conspicuous circular yellow marking near the metastigma about halfway of the length of the stripe; metepisternum with a short triangular stripe; base of the metepisternum marked with a faint green-yellow triangular marking pointing outwards containing the metastigma; small yellow-green spots on both sides above the metepisternum; metepimeron with a green stripe narrowing anteriorly, with a dark brown basal margin; the green stripe marked with a conspicuous, slightly oblique, longitudinally oval yellow spot like the mesepimeronic stripe. Legs mainly colored with black and brown; coxae brown, marked with a small thin yellow marking on mid and hind legs posteriorly; femur and tibia mainly reddish brown, tarsi and the claws black; the junction of the femur and tibia black, the black marking continuing on the anterior femur about 2/3rd of its length.

Wings. Tinted brown, especially at the apices and the posterior margins; antenodals 19 in the fw, 15(left)– 16(right) in the hw; triangle with 4 cells in the hw and 3 (left) and 4 cells (right) in the fw, anal triangle divided into 5 cells, anal loop divided into 6 cells; pterostigma maroon, weakly braced. IRP2 forking nearer to the pterostigma than the nodus.

Abdomen ( Fig. 1 a,b). Marked with greenish yellow, the dorsal markings not continuous; S1 with a small ‘diamond-shaped’ marking dorsally; laterally greenish yellow with the lateral markings connected on the dorsum anteriorly; S2 dorsally marked with a longitudinally triangular AD spot; paired MD spots very minute embedded in the supplementary transverse carina; the PD half of the S2 with a dorsal stripe broadening slightly towards the center connected to the AD spot; S2 with the ventral half irregularly brown, with a conspicuous AL greenish yellow spot, this longitudinally pointed marking continuing on the auricle till the apex; the anterior half of the auricle laterally bright green-yellow whereas the cavity and the posterior half brown, the serrations black; S3–S6 marked with paired triangular MD spots; S3–S6 thinly yellow at the PD edge this yellow marking continuing on the dorsal carina towards the MD spots but not reaching them, both the MD spots and the PD line reduced on S7; the MD and PD markings more bright yellow-green than the AD and ML markings; S3–S7 with a thin yellow AD stripe, on S3 this line continuing about 2/3rd the length till the transverse carina (jugal line); not extending beyond ½ of the jugal area in other segments, very faint in S6–S7; S8 with a triangular area of tubercles at the posterior end peculiar to this group of dragonflies; this triangular patch contains a small yellow line running about half the length of the segment; S10 with very small AD spots on both sides; longitudinally flattened; S9 and S10 with the ventral half dark yellow; a small triangular spot pointing upwards on the posterior side of the transverse carina on S3–S9, this marking connects very faintly to the MD spots via the transverse carina on S4–S5; S4–S8 with extremely small AL spots at the ventral edge of the segments; reduced on S7–S8.

Anal appendages ( Fig. 1 c,d). Ventrum of S10 and paraprocts covered with dried soil; cerci colored black, paraprocts dark brown. Dorsally posterior 2/3 of cerci expanded, outer margin straight, inner margin curved, apical margin rounded pointing slightly outwards, outer margin of cerci faintly yellow. Paraprocts dark brown laterally, ventrally, and on dorsal margin. The central groove of the paraprocts dark-yellow. Paraprocts reaching about half the length of cerci in lateral view, slightly curved upwards, darkened at the apex. Laterally apex of cerci pointed; a medial ridge running on cerci, the ventral margin is straight while the upper margin is curved for apical 1/3 of cerci, medially.

Measurements (mm): abdomen (including anal appendages)=38.9, hw=38, fw=37.4.

Variation in the paratype. Paratype is a younger male than the holotype (wings completely hyaline vs. wings tinted brown in the holotype). Triangle divided into 5 cells in all wings; anal loop 7-celled in right hw, 6-celled in other three wings. Only the PL half of S1 marked with a green-yellow stripe connecting dorsally. The PD edge of the S2 marked thinly with yellow. The AL spots on S4–S8 larger and more conspicuous than the holotype, yellow line at the PD edge less broad. The yellow markings on the outer margin of cerci are very faint in the paratype compared to the type.

Measurements (mm): abdomen (including anal appendages)=38.5, hw=38.1, fw=37.6.

Female: Unknown.

Diagnosis. This species can be distinguished from its congeners by the following set of characters: (a) outwardly pointed apex of cerci in dorsal view; (b) distinctive abdominal markings; and (c) the apex of the frons elevated into a blunt ‘horn’. The dorsal stripe present on the posterior half of S3–S7 is thin, a condition similar to the Indian C. viridifrons (Fraser, 1922) . The pointed and protruding frons is an interesting character also shared by the Chinese C. cornifrons Zhang & Cai 2013 ; add the Indian C. acutifrons (Martin, 1909) also has pointed frons but not sharply pointed as in cornifrons or acanthifrons sp. nov. as seen in dorsal view ( Figure 2 ). C. acanthifrons can be diagnosed from C. acutifrons by the number of cells in the anal triangle (3 vs. 5) and from C. cornifrons by the reduced abdominal markings and the shape of cerci in dorsal view ( Zhang & Cai 2013).

Cephalaeschna masoni (Martin, 1909) and acanthifrons sp. nov. are similar to each other, having the apex of the frons dark, anal triangle with 5 cells each, IRiii forking nearer to the pterostigma and green thoracic stripes. However, acanthifrons sp. nov. can be diagnosed from C. masoni based on: (a) the middorsal yellow line, running intermittently with transverse striae at the posterior of each segment; and (b) the elevated pointed medial lobe of frons (rounded in C. masoni ), pointing anteriorly in dorsal view.

Figures

FIGURE 1. Cephalaeschna acanthifrons sp. nov., holotype male (NCBS-AQ 279); (a) dorsal habitus, (b) lateral habitus, (c) anal appendages: dorsal view, (d) face, and (e) anal appendages: lateral view.

FIGURE 2. Comparison of heads of C. acanthifrons sp. nov.: a: dorsal, b: frontal, and C. acutifrons (Martin, 1909) [from Asahina 1981]: c: dorsal, d: frontal.