Limnogeton scutellatum Mayr, 1863

Ribeiro, José Ricardo I., Meyin-A-Ebong, Solange E., Le-Gall, Philippe & Guilbert, Eric, 2014, A taxonomic synopsis of Limnogeton Mayr, 1853 (Insecta: Hemiptera: Heteroptera: Belostomatidae), Zootaxa 3779 (5), pp. 573-584 : 581-583

Limnogeton scutellatum Mayr, 1863

( Figs. 5 A–D)

Limnogeton scutellatum Mayr, 1863: 361 .

Limnogeton scutellatum: Mayr (1871) : 431. Limnogeton scutellatum: Poisson (1949) : 7.

Limnogeton scutellatum: Linnavuori (1971) : 356.

Types. The species was described based on a holotype of unknown gender (Africa), deposited in NHMW, according to Mayr (1863) and Montandon (1896).

Material examined. EGYPT [?, see above]. 1880, (Letourneux), J. R. I. Ribeiro det. 2011, A. L. Montandon det. 1899: 2 m and 1 f ( MNHN). ETHIOPIA. 1971, (G. de Rougemont), J. R. I. Ribeiro det. 2011: 1 f ( MNHN). CAMEROON. Garoua, 2012, (Meyin), S. E. Meyin det. 2013: 3 m and 1 f (SM); Yagoua, 02.VIII.1971, (F. Puylart), J. R. I. Ribeiro det. in 2013: 1 m ( MRAC). GHANA. No 38, “Endródi Sebo”, ex. Mus. Budapest, N. Nieser det. 1970: 1 m (NC). CENTRAL AFRICAN REPUBLIC. Lamaboké, 08.VIII.1966, (R. Pujol), J. R. I. Ribeiro det. 2011 (identified as L. fieberi ): 1 m ( MNHN). DEMOCRATIC REPUBLIC OF THE CONGO. Molindi River, Albert National Park, “Kib., 1000”[?], “30–14/”, 02.V.1934, (G. F. de Witte): 1 m ( MRAC); 02.V.1934, R. Poisson det. in 1945: 1 f ( MRAC) [391]. CONGO. Brazzaville, V.1959, (L. Vincent), J. R. I. Ribeiro det. 2011: 2 f ( MNHN). ZAMBIA. Muliba, Stanley Pool, 25.IX.1957, (Bula-Matori), [Coll. Mus. Congo], R. Poisson det. 1959: 1 f ( MRAC). Prov. Nyonga, V.1925, (G. F. de Witte), J. R. I. Ribeiro det. in 2013: 1 m ( MRAC) [with eggs on dorsum]; 1 f ( MRAC).

Distribution. Limnogeton scutellatum has been reported from Africa (“aus Afrika”, Mayr 1863: 361), Egypt ( Poisson 1949), Zambia (Molindi River) ( Poisson 1949) and White Nile (‘Nil Blanc”, Poisson 1949: 7); the latter locality is not particularly precise because it refers to a region comprising at least five countries. In addition, Congo ( Poisson 1949) is now known as Democratic Republic of the Congo and Republic of the Congo, which left the range of L. scutellatum in doubt. As argued in Polhemus et al. (1995), Linnavuori (1971) believed that Poisson’s (1949: 7) reference to “ Égypte ” for this species refers to Sudan in the former Anglo-Egyptian Sudan. This species are herein newly recorded from Garoua and Yagoua ( Cameroon), Lamaboké ( Central African Republic), Ethiopia, and Ghana.

Measurements (m / f): Total length (from apex of head to apex of abdomen at rest): 42.5–50.0 / 47.0–49.0; greatest width of body: 20.5–23.1 / 22.0–24.0.

General coloration. Almost uniformly brown. Body ovate with wings almost covering abdomen. Head, thorax, and abdomen. Pronotum with longitudinal median carina usually extending only onto posterior portion; prosternal keel cylindrical and straight, spiniform, acute at apex, not projecting anteriorly (females usually with prosternal keel more robust). Pilosity poorly developed, covering almost half of connexivum, slightly constricted between spiracles, not extending posteriorly along genital operculum (as Fig. 3 C).

Male genitalia. Parameres symmetrical with apex strongly curved; length of phallotheca about 1.5 times ventral diverticulum in dorsal view; ventral diverticulum not robust; dorsal arms of phallotheca directed laterally, slightly divergent, connected or fused along basal portion, U-shaped, rounded at apex ( Fig. 5 C); ventral diverticulum with anterior margins not strongly sclerotized, somewhat robust, parallel posteriorly in ventral view ( Fig. 5 D, MVD).

Taxonomic notes. There is no significant difference in male styli among specimens of L. expansum and L. scutellatum , but the former species clearly comprises the majority of the largest specimens studied. Poisson (1949) stated that the alleged “differences” in male styli, also stressed and discussed by Linnavuori (1971), are not enough to differentiate these species. Poisson thus considered them as conspecific, with L. expansum representing merely large specimens of L. scutellatum . Nevertheless, we have found evident male genitalic characteristics distinguishing L. scutellatum from L. expansum , and these are apparently linked to the differences in growth among these insects (see above). For example, L. scutellatum male specimens, the majority of which are smaller than those of L. expansum , have the dorsal arms ( Fig. 5 C, DA) not gradually narrowing at the apex and shorter than in L. expansum ( Fig. 1 D, DA).

Figures

FIGURE 1. Limnogeton expansum Montandon, external morphology and male genital structures. 1 A, Dorsal habitus showing pronotum with longitudinal median carina. 1 B, Head showing prosternal carina, lateral view. 1 C, Ventral aspect of abdomen showing development of pilosity which covers half of connexivum. 1 D – E, Male genital structures: 1 D, Dorsal apical membranous processes arising from phallotheca. 1 E, Ventral diverticulum of phallosoma showing anterior margins, ventral view. LMC, longitudinal median carina; MVD, margins of ventral diverticulum; PC, prosternal carina; PIL, pilosity of connexivum.

FIGURE 3. Limnogeton hedenborgi (Stål), external morphology and male genital structures. 3 A, Dorsal habitus showing pronotum with longitudinal median carina. 3 B, Head showing prosternal carina, lateral view. 3 C, Ventral aspect of abdomen showing poorly developed pilosity covering almost half of connexivum. 3 D – F, Male genital structures: 3 D, Dorsal apical membranous processes arising from phallotheca. 3 E – F, Ventral diverticulum of phallosoma showing anterior margins, ventral view. DA, dorsal arms of phallotheca; LMC, longitudinal median carina; LOM, lateral outer margins of ventral diverticulum; MVD, margins of ventral diverticulum; PC, prosternal carina; PIL, pilosity of connexivum.

FIGURE 5. Limnogeton scutellatum Mayr, external morphology and male genital structures. 5 A, Dorsal habitus showing pronotum. 5 B, Head showing prosternal carina, lateral view. 5 C – D, Male genital structures: 5 C, Dorsal apical membranous processes arising from phallotheca. 5 D, Ventral diverticulum of phallosoma showing anterior margins, ventral view. LMC, longitudinal median carina; MVD, margins of ventral diverticulum; PC, prosternal carina.