Heliogomphus promelas ( Selys, 1873 )

Sadasivan, Kalesh, Nair, Vinayan P., Palot, Muhamed Jafer, K., Abraham Samuel & Shereef, Anzil, 2022, Taxonomic notes on the genus Heliogomphus Laidlaw, 1922 (Odonata: Gomphidae), with a redescription of H. kalarensis Fraser, 1934 from southern India, International Journal of Odonatology 25, pp. 107-120 : 109-112

Heliogomphus promelas ( Selys, 1873)

( Figs 2A, 2B , 3 , 5A, 5C, 5E, 5G , 7 A–C )

1873 Gomphus promelas Selys : Selys, Bull. Acad. Belg., 36 (2), 498.

1890 Aeshna promelas : Kirby, Cat. Odon., 68.

1907 Gomphus? promelas : Williamson, Proc. U.S. Natl. Mus., 33, 305.

1922 Gomphus promelas Selys : Laidlaw, Rec. Ind. Mus., 24, 371, 398.

1923b Gomphus promelas Selys : Fraser, J. Bom. Nat. Hist. Soc., 29, 330.

1925 Heliogomphus promelas Selys : Fraser, J. Bom. Nat. Hist. Soc., 30, 848, 849, fig. 1, pl. i, fig. 6.

1930 Heliogomphus promelas Selys : Laidlaw, Trans. Ent. Soc. Lond., 78, 182.

1931 Heliogomphus promelas Selys : Fraser, Rec. Ind. Mus., 33, 444, 447.

1932 Heliogomphus promelas Selys : Needham, Rec. Ind. Mus., 34, 220.

1934 Heliogomphus promelas Selys : Fraser, Fauna Brit. India, Odon., Vol II., 323, 324, 326–329. figs 99, 101a.

1942 Heliogomphus promelas Selys : Fraser, Trans. R. Ent. Soc. Lond., 92 (2), 334, 335, 337, 338. 339, 340, figs 1(1) female, 1(5) male, figs 3 (4), 3 (17), plate 1 (2).

1995 Heliogomphus promelas Selys : Prasad & Varshney, Oriental Insects, 29 (1), 400.

2000 Heliogomphus promelas Selys : Tsuda, A Distributional List of World Odonata .

2005 Heliogomphus promelas Selys : Subramanian, Dragonflies and damselflies of Peninsular India, 114.

2009 Heliogomphus promelas Selys : Sharma, Ramamurthy & Kumar, Biological Forum – An International Journal, 1 (2), 108.

2009 Heliogomphus promelas Selys : Subramanian, A checklist of Odonata ( Insecta) of India, 14.

2011 Heliogomphus promelas Selys : Kiran & Raju, Malabar Trogon, 9 (3), 32.

2013 Heliogomphus promelas Selys : Kiran & Raju, Dragonflies and Damselflies of Kerala, 153.

2013 Heliogomphus promelas Selys : Babu, Subramanian & Nandy, Rec. Zool. Surv. India, 347, 5, 25.

2014 Heliogomphus promelas Selys : Emiliyamma, Rec. Zool. Surv. India, 114 (1), 59, 64.

2017 Heliogomphus promelas Selys : Subramanian & Babu, A checklist of Odonata ( Insecta) of India, ver. 3.0, 9, 29.

2018 Heliogomphus promelas Selys : Subramanian, Emiliyamma, Babu, Radhakrishnan & Talmale, Atlas of Odonata ( Insecta) of Western Ghats, India, 26, 224, 225.

2020 Heliogomphus promelas Selys : Kalkman, Babu, Bedjanic, Coniff, Gyeltshen, Khan, Subramanian, Zia & Orr, Zootaxa, 4849 (1), 34.

2021 Heliogomphus promelas Selys : Nair, Samuel, Palot & Sadasivan, Entomon, 46 (3), 192, 214 fig. 2C, 228, 233.

2022 Heliogomphus promelas Selys :Sadasivan, Nair & Samuel, J. Threat. Taxa, 14 (6), 21214, 21225.

2022 Heliogomphus promelas Selys : Nair, Samuel, Palot & Sadasivan, Entomon (in press).

Diagnosis

Antehumeral stripe separated from the mesothoracic collar; sides of thorax with two black stripes; external spine of cerci of moderate size; antehumeral stripe straight; lateral spine of cerci followed posteriorly at the most by a very shallow concavity; superior humeral spot absent; female with vesicle projecting posteriorly with two long, outwardly curved horns ( Fraser, 1942).

Specimens examined (n = 5 males)

NHMUK # 014666648 , male, Burliyar, Nilgiris , Tamil Nadu; Col. Fraser FC ; NHMUK # 014666649 , male, Mudis Hills , Tamil Nadu, 04.v.1929 Col. Fraser FC ; TORG #1015 , male, Pandipathu, Peppara WLS, Trivandrum , Kerala, 24.iii.2022, Col. Kalesh Sadasivan ; TORG #1016 , male, Edamalakudi, Munnar , Kerala, 02.v.2022, Col. Kalesh Sadasivan ; TORG #1017 , male, Kanichar , Kannur, Kerala, 12.vi.2022, Col. Vinayan P Nair.

Other specimens studied in the field (not collected). (n = 7 males). 3 males Pandipathu, Peppara WLS, Trivandrum , Kerala, May 2022, Kalesh Sadasivan; 2 males,Edamalakudi, Munnar, Kerala, May 2022, Kalesh Sadasivan; 2 males, Kanichar , Kannur, Kerala, June 2022, Vinayan P Nair.

Measurements (in mm) (n = 3). Total length (including appendages). 47–48, abdominal length 34–35, forewing length 30–32, hindwing length 30–31, HFL 6. Nodal Range. FW: 15–17 & Px 13–15; HW: Ax 11–12 & Px 11–13.

Morphological variation

We have not found any ambiguity in the description and diagnosis of, or the keys to, H. promelas from that which has already been provided by Fraser (1934, 1942), so that no redescription is required here. Nevertheless, some aspects regarding the melanotic variant, structure of secondary genitalia, and the epiprocts are discussed below.

Melanotic variant ( Figs 7B, 7C ). Fraser (1942) mentioned a melanotic variant of H. promelas in which the large greenish yellow stripe on the metepisternum is highly reduced, appearing as a streak or spot occupying its dorsal half. In some individuals, this reduced streak is split up into two yellow spots. This heavily marked variant is thus easily recognized ( Fig. 7B ). In cases of doubt, examination of the epiprocts and/or vesica spermalis will provide clarity.

Secondary genitalia ( Figs 3B, 3C , 5C ). Colour dark amber-brown to blackish brown. Anterior hamule shorter than the posterior hamule in lateral view, distal half tapering and curved into a hook with its tip directed posterolaterally; body of posterior hamule broader than anterior hamule, tapering and curved gradually towards its tip; the tip of the posterior hamule is relatively pointed, occasionally notched, and is directed anteromedially. Sheath of the vesica spermalis (ligula) broad, higher than the posterior hamule, directed posteriorly, covering the distal portion of Segment 2 and Segment 3 of the vesica spermalis. The structure of the vesica spermalis and the posterior hamule is illustrated in Figs 3B–C . The middle segment of the vesica spermalis in lateral view has a rectangular extension directed posteriorly ( Figs 3C , 5C ). Auricle semicircular in outline in ventral view, with a series of small, medially-directed spines on its posterior and medial portions.

Anal Appendages ( Figs 2B , 3D–F , 5E, 5G ) The epiprocts were not explicitly described by Fraser (1934). In dorsal view, the male cerci are directed posterolaterally, profile of the cerci much straighter; its tip curled in on itself laterally ( Fig. 5G ). Lateral horns of the epiproct angulated dorsally at its middle, posterior half tapering, and directed posterolaterally ( Fig. 5G ); tip of the epiprocts bulbous, bearing a small rudimentary spine directed dorsally.

Distribution

Kerala: Coorg landscape— Malabar, Kanichar in Kannur; Munnar landscape—Edamalakudi, High Range subunit; Agasthyamalai landscape— Ponmudi Hills Ponmudi Hills in Kulathupuzha Reserve and Peppara WLS, (Travancore) (Nair et al., in press). Tamil Nadu: Anamalai and Mudis Hills; Nilgiri Hills—Burliyar, Mettupalayam, and Kotagiri Ghats ( Fraser, 1922, 1925, 1931, 1934, 1942). Karnataka: Coorg—Mercara, Mangalore Ghat, Sampaji River. Goa: Dudhsagar Falls , Cotigao WLS, Derode ( Rangnekar et al., 2010). Odisha: ( Subramanian et al., 2018).

Annotations

In addition to the diagnostic features provided by Fraser (1942) and mentioned above, examination of H. promelas specimens in the BNHM (NHMUK # 014666648), fresh specimens from Western Ghats (12 males, not collected), and voucher specimens in the TORG collection revealed that none of these specimens had antehumeral or occipital spots in agreement to Fraser (1934, 1942) and that the spots on the prothorax were variable. The epiproct of this species is divergent, flat, and curved posterodorsally, with its extreme tip hooked and recurved ( Figs 2B , 3E , 5E, 5G ). This character is constant and reliable for species identification, even when the structure of the cerci is inconclusive, and differentiates it from H. kalarensis . When a specimen labelled ‘ H. unifasciatus Fras. ’ was found in the BMNH collection (NHMUK # 014666649, male, Mudis Hills, Tamil Nadu, 04.v.1929 Col. Fraser FC) and carefully studied it was revealed that the morphological features, notably the epiproct, are those of H. promelas . This taxon name was untraceable in Fraser (1934, 1942) and Paulson et al. (2022), and we found no literature citing this species, hence it must be treated as a nomen nudum.

Figures

Figure 2. Specimens of Heliogomphus from the BMNH, London: (A) Dorsal habitus of H. promelas NHMUK #014666648, male, Burliyar, Nilgiris, Tamil Nadu; (B) close-up in ventral view of epiprocts of H. promelas, NHMUK #014666649; (C) dorsal habitus of H. kalarensis holotype, male, NHMUK #013384589, Kallar, Nilgiris, Tamil Nadu; (D) close-up in ventral view of epiprocts of H. kalarensis, holotype male, NHMUK #013384589; (E) dorsal habitus of H. pruinans NHMUK #013324357, male, Buruliyar, Nilgiris, Tamil Nadu; (F) close-up in ventral view of epiprocts of H. pruinans, NHMUK #013324357. Photos courtesy of BMNH, London.

Figure 3. Specimen of H. promelas, TORG #1015, male, Pandipathu, Peppara WLS, Trivandrum, Kerala: (A) Dorsal view of synthorax; (B) ventral view of genital fossa; (C) right lateral view of vesica spermalis extruded in ventral exposure; (D) right lateral view of anal appendages; (E) ventral view of anal appendages showing dorsally curved epiprocts; (F) dorsal view of anal appendages showing cerci.

Figure 5. Comparison of H. promelas and H. kalarensis males: (A) Ventral view of right auricle of H. promelas; (B) ventral view of right auricle of H. kalarensis; (C) expansion on the middle segment of the vesica spermalis of H. promelas; (D) expansion on the middle segment of the vesica spermalis of H. kalarensis; (E) ventral view of the epiprocts of H. promelas; (F) ventral view of the epiprocts of H. kalarensis; (G) dorsal view of the cerci of H. promelas; (H) dorsal view of the cerci of H. kalarensis.

Figure 7. Schematic overview of the variation in the markings on the synthoraces of H. promelas and H. keralensis: (A) H. promelas; (B) H. promelas melanotic variant; (C) H. promelas melanotic variant; (D) H. kalarensis with upper humeral spots; (E) H. kalarensis without upper humeral spots.