Macrogomphus phalantus Lieftinck, 1935

Kosterin, Oleg E., 2019, New synonyms and a new subspecies of Macrogomphus Selys, 1858 (Odonata: Gomphidae) from continental south-east Asia, Zootaxa 4615 (1), pp. 57-90 : 78-79

Macrogomphus phalantus Lieftinck, 1935

Figs. 12–16

Macrogomphus phalantus , sp. n. — Lieftinck (1935): 201–203, figs 10–12: original description: 2 ♂, 1 ♀, W. Borneo, Singka- wang, swamped forest near Bakoean, low country, 20 vii 1932 (1 ♂) and 15 ix 1932 (1 ♂, 1 ♀), drawings of synthorax, secondary genitalia and anal appendages.

Macrogomphus phalantus Lieftinck—Lieftinck (1954) : 87: report for the eastern Sumatra, Palembang.

Macrogomphus phalantus Lieftinck, 1935 — Dow (2016): 8–9, fig. 3: report for Borneo , Sarawak, Samusan Wildlife Sanctuary, Sungai Samusan, 1 ♀, 18 viii 2015; a habitus photo.

Excluded reports: Asahina (1986) as erroneous (see above); Kemp & Kemp (1989), Norma-Rashid et al. (2001) and Norma- Rashid (2009) as doubtful (Dow 2016).

Remarks. Macrogomphus phalantus was described, in detail, on the basis of two males and a female from W. Borneo, Singkawang, swamped forest near “Bakoean” (Bakuan, Kalimantan Barat Province of Indonesia), as “closely resembling M. parallelogramma albardae Selys but much smaller and with differently shaped anal appendages’ ( Lieftinck 1935: 201). In the diagnosis, such details as “shorter discoidal triangle of the front wing, ... narrower and almost parallel-sided yellow bands on each side of the thorax, and ... more widely separated and more obliquely placed antehumeral thoracic stripes” were mentioned ( Lieftinck 1935: 203). The female was stated to differ from other species by a bifid median prominence on the occipital plate (which was not figured).

Lieftinck abstained from verbal description and comparison of the male anal appendages of M. phalantus but made a confusing statement: “The shape of the inner branch of the sup. anal apps. of the male rather suggests M. borikhanensis Fraser , from the Laos country...” ( Lieftinck 1935: 203). The (incorrect) drawing of the appendages of M. borikhanensis by Fraser (1933: fig. 6a, c; see Fig. 3c , 8d here) hardly resembles their structure in M. phalantus . In fact, M. phalantus exhibits an unique distinct diagnostic character: in dorsal view, the proximal inner swelling of the cercus is very sharp and prominent, and shifted distally off the cercus cleft into its two branches, as indicated with an asterisk in Fig. 15h (after Lieftinck 1935: fig. 12). As a consequence, two more distal swellings are ‘compressed’ to locate closely to each other ( Fig. 15h ). In all illustrations and specimens of M. albardae known to the author ( Figs. 2b ,e–f, 3a–h, 4c, 7a,c, 9a, 11), the proximal inner swelling (indicated by an asterisk in Fig. 1l and 3b ) is smoother and invariably located at the level of the cleft, more proximal swellings also being smoother. The importance of this character could be disputable if I had not collect a series of Macrogomphus males with exactly the same cerci as far from the presumed range of M. phalantus as in Cambodia, but in a similar habitat (see below).

Later the species was reported for Palembang in eastern Sumatra ( Lieftinck 1954). All so scanty reports of this species refer to a habitat unusual for gomphids: swamped forest in low country ( Lieftinck 1935; 1955), a river upstream the Nypa stand and mangroves in lowland rainforest (Dow 2016). The ‘snorkel’ of the elongated terminal abdominal segments of the Macrogomphus larvae suggest ability to live in silt low of oxygen, nevertheless other Macrogomphus spp. are usually found near running water at foothills and mountains.

While studying Odonata of the great Lake Tonlé Sap in Cambodia I was struck to find numerous Macrogomphus sp. at a temporarily inundated forest margin on its northern bank (at the low water season). The male anal appendages appeared to correspond to M. phalantus and the unusual habitat was exactly as in that species. Certain differences of the collected specimens from the original description by Lieftinck (1935), as well as the huge distance of the newly found population from the presumed range of M. phalantu s in Borneo and Sumatra, suggested a new subspecies which is described below.

Figures

FIGURE 1. Details of the specimens identified as Macrogomphus parallelogramma s. str.: the holotype female (a) and males (b–i), as illustrated by Hagen in Selys (1858: planche 5, fig. 5 and planche 20, fig. 4) (a–f); of a male specimen from “Java mer.” from RBINS collection (Courtesy of Jérôme Constant) (g–j): and of a male specimen from “W. Java. 100 m. /, Djaniga / Tjibarangbang / 30.IV.1939 / over stream p.m. / M.A. Lieftinck” and kept in RMNH (courtesy of Jan van Tol) (k,l); a—head, dorsal view; b,h—S8–10 (dorsal view); c,i—ditto (lateral view); d—S10 and appendages, lateral view; e—epiproct, ventral view; f–g,k—cerci, posteriodorsal view; j–k—labels.Asterisk marks the bulge of the inner cercus margin. Not to scale.

FIGURE 2. Details of some male specimens of Macrogomphus albardae kept in RMNH (courtesy of Jan van Tol): a–d—the male syntype (the labels ‘Holotype’ are misleading); e—“W. Borneo, 0 m. / Singkawang / Penanring / L. Coomans de Ruiter / 24. II. 1932”; f—“S. Sumatra / Terbanggi-Hilir / nr. Menggala / Lampang distr. / 18. VIII. 1936 / M. Bartels”; a—general habitus; b, e–f—S10 and anal appendages, dorsal view; c—head and thorax, dorsolateral view; d—labels of the male syntype. Not to scale.

FIGURE 3. Anal appendages (a–h) and secondary genitalia (j–k) of Macrogomphus albardae as illustrated in literature: aafter Lieftinck (1935: fig. 9) (as M. parallelogramma albardae); b—after Orr (2005: p. 64) (as M. parallelogramma albardae); c—after Fraser (1933: fig. 8a, c) (as M. borikhanensis); d—after Asahina (1986: fig. 8–9) (as? M. phalantus): e, j—after Asahina (1986: fig. 4–6) (as M. borikhanensis); f, i—after Chao (1982: fig. 1, 3, 6) (as M. guilinensis); g—after Wilson (2005: fig. 17 d, e) (as M. guilinensis); h—after Karube (2014: fig. 13) (as M. guilinensis). Not to scale; j mirrored. Asterisk indicates the proximal inner swelling of the cercus.

FIGURE 8. Holotype of Macrogomphus borikhanensis Fraser, 1933 and its labels (BMNH): a—dorsal view; b—lateral view. Not to scale. Courtesy of Benjamin Price.

FIGURE 12. Holotype, male (a), and paratype, female (b) of Macrogomphus phalantus jayavarman subsp; nov. Cambodia, Siem Reap Province, 1.5 km SSW of Kampong Pluk village, 70 m S from northern bank of Lake Tonlé Sap, low, open temporarily flooded forest, 13.1956° N, 103.9725° E, 3 m a.s.l., 15 vi 2018, O. Kosterin leg.

FIGURE 13. A male paratype of Macrogomphus phalantus jayavarman subsp; nov. in live colours (the same data as in Fig. 9).

FIGURE 14. Males of Macrogomphus phalantus jayavarman subsp; nov. in nature (the same data as in Fig. 9). On the left upper photo a dead colony of bivalve mollusks is seen on the branch, which appeared when the forest was inundated.

FIGURE 15. Details of male specimens of Macrogomphus phalantus: a–f—M. p. jayavarman subsp; nov., the holotype; gh—M. p. phalantus (After Lieftinck 1935: figs.11–12); a—head, frontal view; b–c,g—secondary genitalia, lateral view; d—anal appendages, dorsal view; e—ditto, lateral view; f—ditto, ventral view; h—dorsal and lateral view. Scale bar 1 mm. Asterisk indicates the proximal inner swellings of the cerci.

FIGURE 16. Details of the female paratype of Macrogomphus phalantus jayavarman subsp; nov., the holotype; a—head, frontal view; b—occiput, frontal view; d—right part of vulvar lamina, ventral view. Scale bar 1 mm.