Merogomphus

Kosterin, Oleg E., 2016, Reconsideration of the genera Merogomphus Martin, 1904, and Anisogomphus Selys, 1857, including erection of a new genus, with a new species and discussion of additional specimens from Cambodia, Zootaxa 4171 (1), pp. 51-76 : 53-56

Merogomphus as an artificial genus

The type species of the genus Merogomphus , M. pavici ranges in S and E China, Taiwan, Laos, Vietnam and Thailand and has the following synonyms: Merogomphus paviei (incorrect subsequent spelling), Anisogomphus pieli Navás, 1932 , Merogomphus chui Asahina, 1968 , Merogomphus lingyinensis Zhou & Wu, 1985 ( Do 2011) . It has characteristic lyrate male cerci with a strong lateral tooth. A closely related M. longistigmus (original combination and spelling Indogomphus longistigma , see above) from Hindustan and M. vespertinus Chao, 1999 , from Sichuan have similar-shaped cerci ( Fraser 1934; Chao 1999). This shape strongly resembles that found in the genus Heliogomphus Laidlaw, 1922 ( Fraser, 1934) . M. femoralis was described as having the cerci “small, pointed, rather lyrate, .... and with a microscopic black tooth externally at about the middle of their length” ( Laidlaw, 1931). Merogomphus vandykei Needham, 1930 also has lyrate cerci but without the spine (Chao 1990).

Two other species, martini and parvus , currently and traditionally placed to Merogomphus are very dissimilar, especially in the shape of the male cerci ( Fig. 1 a–d).

Fraser (1922a) described Platygomphus martini Fraser, 1922 from a pair from Shillong (presently Meghalaya State of India) . In the same year, Fraser (1922b) described the same species again, from a male from ‘Hasimara Tea Estate’ under another name, Burmagomphus duarensis Fraser, 1922 . In his later paper Fraser (1925) used the names martini and duarensis in an interchanging manner, and in the next one he ( Fraser 1926) acknowledged that error and confirmed synonymy of the two species, as resulted from unavailability for comparison of the type of martini at the time of description of duarensis . The species has simple, straight, light-coloured cerci ( Fig. 1 a–b). It ranges in E India, Upper Myanmar and Yunnan of China ( Fraser 1934; Lahiri 1987; Chao 1990).

Fraser (1925) transferred the species martini / duarensis (and also Ophiogomphus cerastis Selys, 1854 , from Nepal and?N. India, misspelled as ‘ cerastes ’; the actual status and taxonomic position unclear, male genitalia and appendages unknown) into the genus Indogomphus (thus first creating the present artificial state of the genus presently known as Merogomphus ). He noted: “the anal appendages of longistigma and duarensis differ widely whilst those of cerastes are unknown, but there are a number of other salient and good generic characters which are common to all, such as the length of the hind femora, the peculiarly specialized armature of these limbs and the relative length of the last four abdominal segments, which resemble somewhat those of Macrogomphus . These in themselves are of sufficient importance to constitute a well-defined genus” ( Fraser 1925: 401). Then a 19-lines long section “Characters of the genus” follows, where the above-mentioned characters were characterised as follows: “Abdomen with the terminal segments prolonged, 8 and 9 of about the equal length, 10 very short; hind femora of great length, extending to apical end of segment 2 and furnished with two rows of very long, very widely sparsed robust spines. Anal appendages variable, lyrate or simple Gomphus sens . strict. design.”.

It is important to stress here that of the mentioned “salient and good generic characters”, the long, sparsely spined femora are in common with Anisogomphus , and the long abdomen is in common at least with some of species of that genus, which was not mentioned by Fraser (1925) at all.

One more species currently attributed to Merogomphus and having simple, light-coloured cerci ( Fig. 1 c–d), as in M. martini ( Fig. 1 a–b), came from Sundaland. Krüger (1899) described Leptogomphus parvus Krüger, 1899 , from a teneral male and a mature female from “Soekaranda” (presently Sukaranda), Sumatra, comparing it with Leptogomphus gestroi Selys, 1891 , L. lansbergei Selys, 1878 , L. semperi Selys, 1878 , and “ Onychogomphus cerastes ” (sic). Schmidt (1935) transferred parvus to the genus Merogomphus , basing on the length and armature of the hind femur as the best common generic characters and a small number of crossveins between the sectors of Arc and the M1-2-M3 bifurcation, as a character distinguishing Merogomphu s from Leptogomphus .

Laidlaw (1931: 211–212) considered Merogomphus to contain the species “ cerastes ”, femoralis , “ longistigma ”, martini , and “ paviei ” but did not mention parvus , which at that time still had not been transferred to that genus. He commented the genus as follows: ‘I ... am forced to the conclusion that these species are also to be referred to the same genus. Important points of agreement are to be found in the venation, in the colouring, in the great length and the armature of the femora, and in the structure of male anal appendages. Martin’s definition of the genus is not altogether complete. ... But the accumulation of evidence afforded by a consideration of all the characters is sufficient to lead one to the conclusion stated above. ... Its nearest ally seems to be the genus Anisogomphus . Characters which serve this alliance are: the long triangle of the hind wing, the occasional tendency for an irregularity of the spacing out of the cross-nerves between M4 and M3-M2, the length and armature of the femora, and the coloured upper pair of anal appendages of the male”. Note that here Laidlaw enumerated precisely the common characters of Merogomphus and Anisogomphus but did not do so for the characters distinguishing them: he pointed where these should be looked for but did not specify which conditions are found in each genus.

At last Fraser (1934) had to compare the genera Anisogomphus and Merogomphus and to state the following: “The genus [ Anisogomphus ] closely resembles Merogomphus and, except for the characteristic anal appendages, can hardly be separated therefrom. Thus the venation of the wings and the armature of the femora agree, including the stalked character of the discoidal cell of the hind-wing and also the long legs and excessively long widely spaced spines on the hind femora, these latter being most evident in the female” ( Fraser 1934: 189). However, he did not place these genera in the same couplet in his generic key, the structure of which was as follows:

“Superior anal appendages as long as branches of inferior appendage and furnished beneath with a black and robust spine”— Anisogomphus ;

- “Superior anal appendages longer than branches of inferior appendages, simple and without spines or processes beneath”—to Mesogomphus , Merogomphus and Stylogomphus ( Fraser 1934: 159) .

So in fact we had only a formal opposition of the ventral spine to the lateral one or none. Chao (1990: 456) adopted Fraser’s distinction of Anisogomphus and Merogomphus and at last placed them in the same key couplet, as follows:

“Superior anal appendages with ventral black protuberance or big tooth................ Anisogomphus ; - Superior anal appendages without ventral black protuberance or tooth.................. Merogomphus ”

This key, however, paid no attention to the absence of any “protuberance or big tooth” in one species placed to Anisogomphus , A. koxingai Chao, 1954 ( Fig. 1 e–f). This resulted in a long-lasting confusion discussed in detail in the next section.

The species Gomphus torpens Needham, 1930 , from Sichuan was transferred to Merogomphus by its author ( Needham 1941); it is so far known by females only, and M. vespertinus may in fact be its junior synonym.

Merogomphus chaoi Yang et Davies, 1993 , described from Yunnan is strongly dissimilar to other species described in Merogomphus up to that time ( Yang & Davies 1993): it is large (hind wing 35–39 mm, abdomen 41– 44 mm), has entirely dark appendages, simple cerci ending with a spine and very large and broad, strongly laterally protruding branches of the epiproct. Most probably it was attributed to Merogomphus for the formal reason of the simple cerci without any processes. In fact it is no doubt a junior synonym of Anisogomphus pinratani Hämäläinen, 1991 , described from the neighbouring North Thailand ( Hämäläinen 1991). All detail of both sexes coincide except a small central occipital swelling present in the female of A. pinratani but seemingly absent in the female of M. chaoi , but it is unclear at which angle of view it was drawn in the latter ( Yang & Davies 1993: fig. 11). So M. chaoi Yang & Davies, 1993 = Anisogomphus pinratani Hämäläinen, 1991 , syn. n.

The name chaoi Yang et Davies, 1993 , originally proposed in the combination Merogomphus chaoi , becomes a secondary junior homonym of Anisogomphus chaoi Liu, 1991 but as soon as it is invalid as a junior synonym, no replacement name is needed for it because of the taxonomic system proposed in this paper.

Merogomhus tamdaoensis Karube, 2001 , was described from North Vietnam as close to M. chaoi (that is to A. pinratani ), hence placed to the same genus. It differs by being even larger (hind wing 46–50 mm, abdomen 50–56 mm) and having the female vulvar scale incision deep but narrow versus short and triangular in A. pinratani . In his later paper, Karube (2014) acknowledged relatedness of A. pinratani , M. chaoi and M. tamdaoensis and stressed the differences of the last from the other two but not of the first from the second. Anyway, neither Merogomphus chaoi nor Merogomphus tamdaoensis in fact belong to Merogomphus in any sense. While the former is a junior synonym, a new combination is proposed for the latter:

Anisogomphus tamdaoensis ( Karube, 2001) , comb. nov.

Figures

FIGURE 1. Diagnostic details of males of some Euthygomphus spp. as illustrated in literature: a – h—anal appendages; i – j, l – m, o—distal part of penis (vesica spermalis); k, n—secondary genitalia; a – b, i – j— E. martini (therein considered as Merogomphus martini): a—after Fraser (1934: fig. 95 b); i—after Fraser (1940: plate 3.3); b, j—after Lahiri (1987: fig. 364 – 365,314 – 315); c – d, k— E. parvus (as Merogomphus parvus): c, k—from South Sumatra, Lampoeng residency, Giesting near Talang Padang, Wai Teboe River after Lieftinck (1941: plate 13, fig. 3 – 5); d—from Malay Peninsula, Central Perak, Sungai Plus, near Lasah after Lieftinck (1964: fig. 46); e – f, l – m, p – q— E. koxingai (as Anisogomphus koxingai): e, l, p—the holotype, after Chao (1954: fig. 293 – 297); f, m, q—from China, Guandong after Wilson & Xu (2009: fig. 1 e – g); g, n— E. fujianensis, the holotype of Anisogomphus fujianensis, after Zhou & Wu (1992: fig. 16 – 18); h, o, r— A. chaoi, the holotype of Anisogomphus chaoi, after Liu (1991: fig. 3 – 8). Not to scale; i, b, k mirrored.