Ranatra spinifrons Montandon, 1910, 1905

Tran, A. D. & Poggi, R., 2019, The genus Ranatra Fabricius (Heteroptera: Nepidae) in Borneo, with a redescription of Ranatra spinifrons Montandon and the description of a new species, Zootaxa 4555 (2), pp. 236-246 : 237-241

Ranatra spinifrons Montandon, 1910

( Figs. 1–16 )

Ranatra stali Montandon, 1905: 390 –391 (in part).

Ranatra stali var. spinifrons Montandon, 1910b: 166 .

Ranatra spinifrons Montandon, 1914: 124 –125; Lundblad, 1933: 29, 45; Lansbury, 1972: 339.

Material examined. Syntype, herein designated as LECTOTYPE: 1 male, “ Borneo Sarawak 1865-66 Coll. G. Doria ” (det. Montandon, 1910) ( MSNG) .

Non-type material. BRUNEI: 5 males, 4 females, Belai District, Sg. Melilas, coll. HH Tan, 12 May 1996, THH9615/9625 (ZRC.6.18819).

Redescription. General colouration: mostly light brown to brown; eyes dark brown; anterior lobe of pronotum yellowish brown; all coxae brown; fore tibia, fore tarsus, middle and hind femora yellow and light brown; fore femur, middle and hind tibiae and tarsi annulated brown and yellow.

Measurements: Males: body length 30.0–32.5 (lectotype: 30.0); length of siphon 20.2–22.4 (siphon missing in lectotype); width of head 2.58–2.94 (lectotype: 2.58); width of eye 0.94–1.02 (lectotype: 0.94); interocular width 0.78–0.94 (lectotype: 0.78); anterior width of pronotum 2.06; humeral width of pronotum 2.51; length of anterior lobe of pronotum along midline 5.89; length of posterior lobe along midline 1.98; fore leg: lengths of coxa 5.30, femur 8.50, tibia 3.12, tarsi 0.70; middle leg: lengths of femur 13.50, tibia 11.80, tarsi 2.20; hind leg: lengths of femur 14.0, tibia 16.0, tarsi 2.0.

Females: body length 33.5–36.0; length of siphon 20.0–22.0; width of head 3.06; width of eye 1.03; interocular width 1.00; anterior width of pronotum 2.41; humeral width of pronotum 3.03; length of anterior lobe along midline 6.80; length of posterior lobe along midline 2.50; fore leg: lengths of coxa 6.00, femur 9.30, tibia 3.55, tarsi 0.81; middle leg: lengths of femur 14.40, tibia 12.25, tarsi 2.00; hind leg: lengths of femur 14.60, tibia 17.10, tarsi 2.10.

Head ( Figs. 3 , 6, 7 ): Vertex above eyes with a very high, acute tubercle, height of tubercle about same as width of eye in lateral view; width of eyes subequal to or slightly greater than interocular width; clypeus flat, higher than and surpassing lora; lora bearing long, pale setae along dorsal side, similar setae also on vertex. Antenna: second segment with long, finger-like projection; finger-like projection about two-thirds to three-quarters length of third segment.

Thorax: Prothorax in lateral view distinctly longer than fore coxa (about 1.6× the length of fore coxa) and slightly longer than fore femur; anterior lobe about 2.5–2.8× as long as posterior lobe when measured along longitudinal midline; anterior margin of pronotum with a tubercle on each side of longitudinal midline, distinctly raised when viewed laterally; ratio of humeral width / anterior width (in both sexes) 1.2–1.3; posterior lobe with humeri broadly rounded ( Fig. 7 ). Scutellum with length ca. 1.55–1.95× width, posterior section with narrowly rounded apex. Prosternum with low median carina on anterior part, anterior margin straight. Mesosternum with pair of low tubercles on anterolateral margin, posterior projection between middle coxae truncate, weakly grooved along midline. Metasternum with anterior part weakly grooved along midline, posterior part slightly raised medially and grooved laterally, posterior margin deeply emarginated ( Fig. 8 ). Space between middle coxae narrower than that between hind coxae. Hemelytra uniformly textured, mostly brown, with membrane only reaching mid-length of abdominal tergum VI.

Legs: Fore femur ( Figs. 9–12 ): in both sexes slender, widest at basal part (ratio of maximum width at basal part

/ maximum width at distal part, in males: 1.11–1.24 (lectotype 1.11), in females: 1.23–1.35); ventral margin with a long median carina bearing dense short setae and a tooth on mesal surface situated distally to median carina; distal part with a small tooth on lateral surface of ventral margin, proximal to sinuous pre-apical ventral margin, distal tooth slightly longer than surrounding setae on ventral side of femur; ratio of width of femur across median tooth (excluding tuft of setae) / width of femur at basal part: 0.88–1.05 (lectotype 1.05); ratio of width of femur across median tooth / width at base of tooth at distal side: 1.42–1.52 (lectotype: 1.51); ratio of width of femur across median tooth / width of femur across median carina (excluding setae, on proximal side of median tooth): 1.15–1.31 (lectotype: 1.31). Middle femur slightly shorter than hind femur; hind femur, when folded back parallel to body not reaching posterior margin of abdominal sternum VI. Middle tibia shorter than middle femur; hind tibia longer than hind femur; middle and hind femora both bearing sparsely distributed long, thin, pale hairs along their lengths; middle and hind tibiae both bearing dense fringe of long hairs on posterior margins along their entire lengths.

Abdomen: Operculum of male ( Fig. 13 ) about as long as connexivum, medially keeled, apex pointed. Operculum of female clearly longer than connexivum, surpassing the apex of connexivum of about one fifth the length of operculum. Respiratory siphon with only sparse long, thin hairs along its length, not formed into a fringe.

Male genitalia: Paramere ( Figs. 5 , 15, 16 ): strongly constricted at distal half before a broadly curved and slender apical hook, inner side of curve with short setae; apex of hook narrowly rounded; ventral side of paramere before apical hook bearing a large sub-triangular elevation, with long setae; dorsal surface of paramere almost straight, only slightly sinuate at distal third. Phallotheca strongly sclerotised, as in Figs. 4 , 14 .

Discussion. Montandon (1905), when describing Ranatra stali based on a specimen from the Philippines, reported a male specimen from Ternate ( Moluccas) and another male from Borneo. He tentatively treated these two specimens as a simple variety of R. stali and noted that they differed in some aspects from Ranatra stali s.str. from the Philippines. Subsequently, Montandon (1910b) recognised the two specimens from Ternate and Borneo as a new variety, Ranatra stali var. spinifrons Montandon, 1910 , and later as a distinct species ( Montandon 1914) on the basis of the following characteristics: the fore femur has an indistinct tooth on the apical part; the tubercle on the vertex between the eyes is acute, very high and laterally flattened; the middle tibiae are considerably shorter than the middle femora; and the siphon is about two-thirds of the length of abdomen ( Montandon 1910b, 1914).

Montandon (1905, 1910b, 1914) provided slightly different interpretations of the fore femur character. More specifically, in 1905, he noted that the specimen from Ternate had no teeth and a simple sinuosity at the apical end, but subsequently (1910b, 1914) stated the fore femur was less noticeably toothed at apex, implying the presence of a small tooth in the apical part. On the respiratory siphon, Montandon (1905) noted that the specimen from Ternate had the siphon about two-thirds the length of the abdomen, whereas on the specimen from Borneo, he noted that its siphon was missing and the body length was 30 mm. As such, the actual length of siphon in the Bornean specimen was unknown.

The descriptions of characters by Montandon (1905, 1910b, 1914) as mentioned above, unfortunately are insufficient for species diagnosis. To be certain about the species' identity, the male genitalia, the paramere in particular, need to be studied and illustrated. Another problem is that descriptions made by Montandon were not accompanied by any illustrations. Lansbury (1972), in his revision of the Oriental Ranatra , was unable to examine the two syntypes, thus tentatively assigned R. spinifrons Montandon to the R. gracilis species group. He noted that the specimen from Ternate, supposedly deposited in “Coll. G. Breddin”, might have been lost. The collection by Gustav Breddin (1864-1909) was bought in 1910 by the Deutsches Entomologisches National-Museum, now merged in the Senckenberg Deutsches Entomologisches Institut (Müncheberg, Germany), but in fact Gaedike (1971) did not quote Ranatra spinifrons in her catalogue of Heteroptera types preserved in DEI collections. Lansbury also attempted to locate the specimen from Borneo, knowing that it was still in the Civic Museum of Natural History of Genoa, but for unstated reasons, he did not examine it. After the revision by Lansbury (1972), no literature on taxonomy of Ranatra has provided detailed information about the syntypes of R. spinifrons . Thus, the identity of this taxon remained uncertain.

In this study, after examining the syntype collected from Borneo ( Sarawak), which is deposited in the Civic Museum of Natural History of Genoa, we can confirm that it is a distinct species. In addition, we have also studied a sample of Ranatra , collected from Brunei, that is identical to the type of R. spinifrons . This sample represents the first record of R. spinifrons from Brunei. We here designate the syntype from Sarawak, Borneo as the lectotype of Ranatra spinifrons Montandon. Because the descriptions by Montandon (1910b, 1914) did not provide enough information for species identification, we provide the above redescription of R. spinifrons based on the lectotype and additional specimens from Brunei.

Ranatra spinifrons Montandon can be determined by the following diagnostic characteristics: (a) the tubercle between the eyes is very prominent, with its height about equal to the eye width in lateral view ( Figs. 3 , 6 ); (b) the paramere is strongly constricted before the slender, broadly-curved apical hook, with the ventral side of the paramere before the apical hook possessing a large sub-triangular process with long setae ( Figs. 5 , 15, 16 ); (c) the fore femur is slender, with a small (but distinct) tooth on the lateral surface of the ventral margin before the apex, the distal tooth is slightly longer than the surrounding setae on the ventral side of the femur ( Figs. 9–12 ); and (d) the hind femur is short and does not reach the posterior margin of abdominal sternum VI when folded back parallel to the abdomen. In addition, the siphon of the lectotype was missing. Montandon (1910b, 1914) clearly made an assumption about the relative length of R. spinifrons , two-thirds the length of abdomen, based only on the specimen from Ternate. Based on the recent sample from Brunei, we now know that the respiratory siphon of R. spinifrons is longer, about two-thirds the length of body and is slightly longer than the length of the abdomen (in males) or subequal to the length of the abdomen (in females). Therefore, the other syntype of R. spinifrons , from Ternate, probably belongs to a different species because its siphon was shorter, only about two-thirds the length of abdomen, as noted by Montandon (1905).

Ranatra spinifrons Montandon belongs to the R. gracilis species group (sensu Lansbury 1972) in having the following characteristics: the vertex has a prominent tubercle; the prothorax is longer than the fore coxa and femur; and the metasternum has an emarginated posterior margin. To date, this species group consists of eight species: R. gracilis Dallas, 1850 ; R. parmata Mayr, 1865 ; R. stali Montandon, 1905 ; R. distanti Montandon, 1910a ; R. spinifrons Montandon, 1910b ; R. lansburyi Chen, Nieser & Ho, 2004 ; R. schuhi Polhemus & Polhemus, 2012 , and R. heoki sp.n.

Among the taxa of the R. gracilis group, R. spinifrons is relatively similar to R. schuhi from Myanmar, in the general form of the paramere. However, it can be easily separated from the latter by following features. In particular, the tubercle on the vertex of R. spinifrons is very high, about same as the eye width in lateral view, whereas that of R. schuhi is only about one-third the eye width. The paramere of R. spinifrons is more strongly constricted before the apical hook, and the apical hook is longer than that of R. schuhi (compare with Polhemus & Polhemus 2012: Figs. 3A, 3B ). Other differences between R. spinifrons and R. schuhi include the siphon of R. spinifrons is relatively longer, about two-thirds the body length (while in the latter, it is about one-third the body length); the hemelytra of R. spinifrons is uniformly textured, mostly yellowish brown and shorter, with the membrane only reaching the mid-length of abdominal tergum VI (in R. schuhi , the hemelytra are reddish brown, with the membrane reaching the posterior margin of abdominal tergum VII); the fore femur of R. spinifrons is more slender, with the distal part narrower than basal part (in R. schuhi , the basal part of fore femur is narrower than the distal part); the hind femur of R. spinifrons in both sexes is shorter and does not reach the posterior margin of abdominal sternum VI when folded back parallel to the abdomen (in R. schuhi , the male hind femur reaches the anterior half of the operculum and the female hind femur does not reach the posterior margin of abdominal sternum VI).

Polhemus & Polhemus (2013: 35) reported a male specimen from Selangor, Peninsular Malaysia and tentatively assigned it to R. spinifrons . Polhemus & Polhemus (2013) had doubts about the identify of that specimen because the type of R. spinifrons was not available for their study and the descriptions by Montandon were not sufficiently informative, but referred to it as R. spinifrons , mostly based on the prominent tubercle on the vertex as well as the relative lengths of the siphon and abdomen. Based on our examination of the type of R. spinifrons , and comparison with illustrations made by Polhemus (2013: Figs. 15, 16 ) we conclude that the respective specimen studied by Polhemus & Polhemus (2013) belongs to another taxon, and is probably a new species. In particular, the paramere of that specimen is more similar to that of R. stali Montandon , as also noted by Polhemus & Polhemus (2013), and is clearly different from that of R. spinifrons .

Distribution. Borneo: Sarawak; first record for Brunei.

Figures

FIGURES 1–5. Ranatra spinifrons Montandon, lectotype. (1) specimen labels. (2) habitus, dorsal view. (3) head and anterior part of prothorax, lateral view. (4) male genitalia, lateral view. (5) paramere. (figures not to same scale)

FIGURES 6–16. Ranatra spinifrons, specimen from Brunei. (6) head and prothorax, lateral view. (7) head and prothorax, dorsal view. (8) metasternum. (9, 10) left fore leg and femoral teeth, lateral view. (11, 12) left fore leg and femoral teeth, mesal view. (13) operculum. (14) phallotheca. (15) paramere. (16) apical part of paramere. (scale bars: 6, 7, 9, 11 same scale; 10, 12 same scale; 8, 13 same scale)