Euthygomphus yunnanensis ( Zhou & Wu, 1992 )

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 : 62-68

Euthygomphus yunnanensis ( Zhou & Wu, 1992)

Fig. 4–6 , 7 a–b

Previous reports from Cambodia:

Burmagomphus sp. (part)— Kosterin 2010: 36, 55: 2 teneral ♀ photographed (misidentified), Koh Kong Province, Thma Bang River upstream waterfall, 5 km SW Thma Bang village, 15 iv 2010)

Merogomphus parvus ( Krüger, 1899) —Kosterin 2012: 34, 49, 78, figs 24, 49: still erroneous reidentification of the above photographic record; 1♀, Koh Kong Province, 6.5 km SW Thma Bang village , 23 viii 2011).

Merogomphus parvus ( Krüger, 1899) —Kosterin et al. 2012: 162 (listed).

Merogomphus parvus ( Krüger, 1899) — Kosterin 2015: 28 –29, fig. 21b, table 4: 1 teneral ♂, Pursat Province, O’Som village, 24 iii 2015).

Specimens studied. 1♀ (dry, in envelope), Cambodia, Koh Kong Province, ‘ Microgomphus River’ 6.5 km SW Thma Bang village, 11°38'42–47'' N, 103°23'43–51'' E, 343–346 m a.s.l., 23 viii 2011 ; 1♂ (collected teneral, hardened in captivity overnight, dry in envelope), the same locality, 2 vi 2014 ; 1♀ (teneral, almost uncoloured, preserved in alcohol), Cambodia, Koh Kong Province, Thma Bang River 5 km SW Thma Bang village, 11°39'31'' N, 103°24'14'' E, 366 m a.s.l., 15 iv 2010 ; 1♂ (collected teneral, hardened in captivity overnight, preserved in alcohol), Cambodia, Pursat Province, a river at O’Som village , 12°04'40–45'' N 103°12' 21–35'', 524–531 m a.s.l., 24 iii 2015 ; 1♂ 1♀, Cambodia, Mondulkiri Province, downstream of Buu Sraa Waterfall, ‘ Loringae brook’ upstream its waterfall, 12°33'58''–34'19'' N 107°24'43'' –25'02'' E, 432–515 m a.s.l., 10 vi 2014 (dry in envelopes) ; 1♀, Cambodia, Mondulkiri Province, just downstream of Buu Sraa Waterfall , the main river right bank, 12°34'09'' N 107°25'07'' E, 456 m a.s.l., 4 viii 2016 (acetoned, dry in envelope) ; 1♂, Cambodia, Stung Treng Province, Thala Barivat District , a brook in open low deciduous dipterocarp forest, 13°48'02'' N 105°51'50'' E, 84 m a.s.l., 27 vii 2016 (acetoned, dry in envelope) ; 1♀, Cambodia, Stung Treng Province, Thala Barivat District and Commune, 0.5 km E of Srae Ruessei village, a brook similar to the above, 13°36'04''' N 105°55' 50' E, 67 m a.s.l., 28 vii 2016 (acetoned, dry in envelope); all collected by O. Kosterin, in the author’s collection.

Remarks. The main diagnostic feature of this species is the penis (vesica spermalis) structure. Its distal segment (V4) in lateral view looks narrow, with a small ventrobasal expansion ( Fig. 4 a,c,h–i), as illustrated before ( Asahina 1986, Zhang & Wu 1991) ( Fig. 3 e,m–n). Unfortunately, neither author illustrated the ventral view of the penis of this species. The actual structure of the distal segment (V4) is as follows. Its ventral (outer) surface is almost flat, only slightly lengthwise concave (more in proximal part) ( Fig. 4 f–g,k); its dorsal (inner) surface has two semicircular keels in its basal part ( Fig. 4 j). In ventral view its shape resembles a duck’s beak or a hippopotamus’s muzzle ( Fig. 4 f–g, k) (while the whole penis looks like a duck’s head and neck, Fig. 4 h): it slightly expands at the base and strongly expands at the apex. The apical margin of the ventral surface is somewhat rounded, while that of the dorsal surface is almost rectangular, with the membranaceous distal ejaculation pores between them ( Fig. 4 f–g, k). If preserved in alcohol, the two short membranaceous ventroapical processes on the medial segment (V3) are well seen ( Fig. 4 g–k). No trace of cornua (claws).

Other important characters are:

- Simple male cerci, yellowish white with a brownish base ( Fig. 5 k–m), very slightly arched in lateral view ( Fig. 5 l), pointed to a small apical tooth directed back, below which the apex is rounded, with a black area of low irregular fine knobs ( Fig. 5 m). (Note the cercus is blunt in the Sumatran male of M. parvus , see Lieftinck 1941 and Fig. 1 c).

- Epiproct with the branches rather slender, arched down and slightly hooked apically in lateral view ( Fig. 5 l), in ventral view outer sides of the branches convex ( Fig. 5 m) and incision between the branches shallow, evenly roundish ( Fig. 5 m).

- Female vulvar scale triangular with blunt lobes and a narrowly pointed incision between them ( Fig. 5 n).

- Simple occiput with scarcely defined ridge, straight in males ( Fig. 5 g); in females it varies from nearly straight in specimen from Koh Kong Province ( Fig. 5 h) to having two slight waves in specimens from Mondulkiri and Stung Treng Provinces ( Fig. 5 j); one of the Mondulkiri females has vestigial knobs and the other wellexpressed spines at its sides just near the eyes. The occiput coloration is variable, perhaps geographically. In the male ( Fig. 5 e,g) and females ( Fig. 5 f,i–j) from Mondulkiri Province (eastern Cambodia), most of the occiput is yellow. The male from Stung Treng Province (northern Cambodia) has the occiput black, while the female from there has a central yellow spot. The male from Pursat Province (southwestern Cambodia) has a small indistinct yellow spot in the occiput centre. In both male and female ( Fig. 5 h) from Koh Kong Province (also southwestern Cambodia), the occiput is brownish black. The same variable coloration of the female occiput and presence of the knobs/spines is reported for Thai and Vietnamese specimens by Asahina (1986) as well ( Fig. 3 r–t): of the two Thai females illustrated by him, one had the occiput almost entirely yellow and without knobs ( Fig. 3 p,r), and in the other the yellowish colour was nearly disappearing and there were vestigial knobs ( Fig. 3 q,s); in the female from South Vietnam the knobs looked like minute spines ( Fig. 3 t).

- On metepisternum ( Fig. 5 c–d), dorsal stripes broadly confluent to collar stripes in a hockey-stick-like manner. Collar stripes narrowly interrupted at the middle.

- Antealar spot present invariably. The antehumeral stripes (well expressed in the holotype, see Fig. 3 d) are absent in mature Cambodian specimens ( Fig. 5 a–d, 6a), even in two males collected teneral and kept overnight. However, one of those specimens, the male from Pursat Province, had the antehumeral stripes in its teneral condition ( Fig. 6 c); the teneral females from the Thma Bang River also had these stripes ( Fig. 6 d). Among the five Thai specimens reported by Asahina (1986) the Mae Hong Son female had an interrupted antehumeral streak, others not ( Fig. 3 k). Apparently, the antehumeral stripes are present in teneral specimens and disappear with acquisition of the full colouring. Most probably, the holotype ( Liu 1991) was collected teneral, or perhaps the stripes may be retained in maturity in the northern part of the range (Yunnan).

Interestingly, in about half of the hindwings available (7 of 15, right one missing in one of the Mondulkiri), the 2nd primary antenodal is 6th ( Fig. 7 a–b); otherwise it is 5th (in both wings of both Stung Treng specimens, the left hindwing of one of the females from Mondulkiri and in the left hindwing of the Koh Kong Province female), and in one case 7th (the left hindwing of the Pursat Province male). On the forewing the 2nd principal antenodal is 5th ( Fig. 7 a–b), with two exceptions: in the Pursat Province male it is 6th on the left forewing and in one of the Mondulkiri females it is 4th on the left forewing. An incomplete basal antenodal is present in the forewing ( Fig. 5 a–b, 7b), with exception of the Stung Treng female and one of the Mondulkiri females, in which it is absent on both wings.

Other characters are mostly shared with other species of the genus Euthygomphus .

Measurements (mm): males: forewing 25–26, hindwing 24–25, abdomen without appendages 28–31, total length (with appendages) 39–44, hind femur 7.0–7.3, fore pterostigma 2.5–2.7, hind pterostigma 2.9–3.0: females: forewing 25–26, hindwing 24–25, abdomen without appendages 28–31, total length (with appendages) 39–44, hind femur 7.0–7.4, fore pterostigma 3.2–3.3, hind pterostigma 3.4–3.5. Antenodals: 13–16 on forewing, 9–11 on hindwing; postnodals: 9–11 on both wings.

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.

FIGURE 3. Details of Euthygomphus yunnanensis Zhou & Wu, 1992 as illustrated in literature: a – g—after Zhou & Wu (1992: fig. 19 – 25), therein as Anisogomphus yunnanensis, h – t—after Asahina (1986: fig. 25 – 37), therein as Merogomphus parvus (sensu Asahina 1986 nec Krüger, 1899); a – g—the male holotype from China, Yunnan Province, Wandingzhen; h – n—males from Thailand (h – j—from Saraburi Province, Muak Lek); o – t—females from Thailand (p, r—from Mae Hon Son, q, s—from Saraburi Province, Muak Lek) and S. Vietnam, B’Lao; a, h—anal appendages, lateral view; b, i—ditto, dorsal view; c—head, frontal view; j, p, q—ditto, subfrontal view; r – t—occiput enlarged; e—penis (vesica spermalis), lateral view; f—posterior hamulus; g—anterior hamulus; m – n—secondary genitalia, lateral view; l—metafemur; o—end of abdomen, ventral view. Not to scale; a – b and e – g mirrored.

FIGURE 4. Details of secondary genitalia of males of Euthygomphus yunnanensis from Cambodia: a – c—from Mondulkiri Province, ‘ Loringae’ brook downstream of Buu Sraa Waterfalls; d – f—from Koh Kong Province, ‘ Microgomphus River’ 6.5 km SW Thma Bang village; g – k—from Pursat Province, O’Som village; a—general lateral view; b—hamuli, lateral view; d, anterior hamulus, lateral view; e, posterior hamulus, oblique view; c—penis distal segment (V 4), lateral view; f – g—ditto, ventral view; i—ditto, lateral view; j—ditto, dorsolateral view; h—penis (vesica spermalis), lateral view; k—ditto, ventral view. Not to scale.

FIGURE 5. Details of Cambodian specimens of Euthygomphus yunnanensis: a, e, g, k – m—male from Mondulkiri Province, ‘ Loringae’ brook downstream of Buu Sraa Waterfalls; b – d, f – j, n—females: b – c, f, i – j, n—from the same locality, d, h—from Koh Kong Province, ‘ Microgomphus River’ 6.5 km SW Thma Bang village; a – d—thorax, lateral view; e – f—head, frontal view; g – i—occiput, fromtal view; j—ditto, dorsal view; k—male anal appendages, dorsal view; l—ditto, lateral view; m—ditto, ventral view; n—female vulvar scale, ventral view. Not to scale; b, l mirrored.

FIGURE 6. Individuals of Euthygomphus yunnanensis in life: a—mature male, Cambodia, Stung Treng Province, Thala Barivat District, 27 vii 2016; b—teneral female, Cambodia, Koh Kong Province, Thma Bang River 5 km SW Thma Bang village, 366 m a. s. l., 15 iv 2010; c—teneral male, Cambodia, Pursat Province, a river at O’Som village, 12 ° 04 ' 40 – 45 '' N 103 ° 12 ' 21 – 35 '', 524 – 531 m a. s. l., 24 iii 2015. Not to scale.

FIGURE 7. Wings of Euthygomphus yunnanensis (a—male, from Cambodia, Mondulkiri Province, ‘ Loringae’ brook downstream of Buu Sraa Waterfalls, b—female from Cambodia, Koh Kong Province, ‘ Microgomphus River’ 6.5 km SW Thma Bang village) and A. (E.) schorri (c—male holotype, from Cambodia, Mondulkiri Province, 3.5 – 3.8 km ESE of Sen Monorom, ‘ Culminicola Rivulet; d—paratype female 2 from Cambodia, Mondulkiri Province, downstream of Buu Sraa Waterfalls). Not to scale; c mirrored.