Nerthra papaceki, Nieser & Chen & Caspers, 2024

Nieser, Nico, Chen, Ping-ping & Caspers, Max, 2024, Taxonomic notes on toad bug genus Nerthra (Hemiptera: Heteroptera: Gelastocoridae) with description of a new species from Bonaire and Curaçao, Acta Entomologica Musei Nationalis Pragae 64 (1), pp. 33-46 : 39-42

Nerthra papaceki sp. nov.

( Figs 24–30 , 38 )

Type locality. Bonaire, Lac, Cai, 12°11′N, 68°22′W.

Type material. HOLOTYPE: 3: BONAIRE: Lac , Cai, 12°11’N, 68°22’W, Rhizophora , 16.ix.1967, leg. P.W. Hummelinck 880 ( RMNH) . PARATYPES: BONAIRE: same data as holotype, 1 ♀ ( RMNH); Cay, entrance of Lac, Avicennia leaves, 1.ix.1948, leg. P. W. Hummelinck 180a, 1 ♀ ( NCTN). CURAÇAO: Groot St. Joris, shore, 12°12′N, 68°83′W, Rhizophora in muddy sand, 9.iv.1949, leg. P.W. Hummelinck 326, 2 ♀♀ ( NCTN).

Description. Dimensions (in mm). Male ( Figs 24–26 ): Length 5.21, width of pronotum 3.58, width of abdomen 3.61, width of hemielytra over embolia 3.72. Female ( Figs 28–29 ): length 5.77– 5.87 – 5.96 mm, width of pronotum 3.70– 3.85 –3.99, width of abdomen 3.83– 4.16 –4.34, width of hemielytra over embolia 3.99– 4.10 –4.31.

Colouration. Castaneous, pronotum laterally and legs lighter, usually covered with mud and sand.

Structure. Head. Front of head with apex concavely excavated, with a stout, short and blunt tubercle on either edge of the excavation. Lateral tubercles apparently absent, a small pointed tubercle in centre of frons and two low, blunt, distinct tubercles laterally on vertex. Ocelli absent. Pronotum with a pair of strongly elevated submedian elevations accentuated by clavate bristles, anterior quarter of lateral margins convergent, virtually straight; posterior edges rounded, remainder of lateral margins parallel, straight. Width of pronotum subequal to width of abdomen in male, slightly less than width of abdomen in females. Posterior margin of pronotum sinuate, with a pair of short, submedian caudal projections. Scutellum with a central elongate elevation beset with clavate bristles, basal width of scutellum about 1.5 times its median length. Hemielytra fused, membranes reduced. Just behind pronotum midway between scutellum and lateral margin of embolium a small longitudinal elevation beset with clavate bristles, caudally from this halfway between posterior margin of pronotum and caudal tip of the hemielytron a more pronounced elevation also accentuated by clavate bristles. Embolium covering abdomen, its lateral margin rounded, hemielytra leaving a narrow strip of connexivum uncovered. Laterocaudal edges of abdominal segments rounded, accentuated by clavate bristles. Body dorsally sparsely beset with clavate bristles, more densely on the elevations. Legs. Fore trochanter with two blunt projections, fore femur anteriorly not strongly dilated.

Male. Abdominal venter. Sternites II–IV symmetrical, V–VI only slightly asymmetrical, much less so than in other species of Nerthra , sternite VIII with posterolateral corners somewhat produced caudally; sternites VII–IX distinctly asymmetrical ( Fig. 25 ). Genitalia. Pygophore globular; left paramere reduced; right paramere ( Figs 30a,b ) a simple rod with slightly curved apex, middle part of shaft slightly narrowing. (See also Differential diagnosis and discussion.)

Female abdominal sternites almost symmetrical, last sternite (VII) without tumescences, its median length only slightly shorter than that of all preceding segments together, its posterior margin straight, nearly covering the lobes of ovipositor ( Fig. 29 ).

Etymology. Named in honor of the late Professor Dr.Miroslav Papáček (1953–2019) for his wide ranging contributions on biology. Notably the morphology and taxonomy of Gerromorpha and Nepomorpha (see DITRICH et al. 2020).

Habitat and distribution. This species is known only from the Caribbean Islands Bonaire and Curaçao ( Fig. 38 ), where it apparently lives in mangroves. This species should be looked for in the mangroves of Aruba, Trinidad, and the northern coast of South America. Apparently it burrows in mud because the holotype ( Fig. 26 ) and paratypes ( Fig. 28 ) were covered by a layer of fine silt concealing its real colouration ( Figs 24, 25 , 29 ). Fused hemielytra have been suggested to enable a burrowing way of life ( TODD 1955). Differential diagnosis and discussion. The shape of right paramere of N. papaceki is very similar to that of N. parvula ( Signoret, 1864) from Chile. However, the aedeagal furrow of N. papaceki is entirely dorsal ( Fig. 30b ), whereas in N. parvula it is visible in ventral view in the apical part of the right paramere. In addition, N. parvula is larger, with the body length of males 5.8–6.1 mm ( TODD 1955), and the hemielytra are not fused and have well-developed membranes.

This species does not run well with the key of TODD (1955). It runs either to N. americana or to N. rugosa ( Desjardins, 1837) , but only the latter is closely related to N. papaceki . Males of N. americana have a large dorsolateral projection on the paramere ( Fig. 15 ), which is lacking in N. papaceki ( Fig. 30 ). Females of N. americana have the caudal margin of the last abdominal sternite deeply incised, leaving the large asymmetrical lobes of the ovipositor uncovered ( Fig. 4 ), whereas the caudal margin of the last abdominal sternite of females of N. papaceki is straight, almost covering the ovipositor lobes ( Fig. 29 ). Alternatively, it could run to N. rugosa , which was described from Mauritius but also recorded from Panamá (Pearl Islands, on the Pacific side, TODD 1955) and Florida, U.S.A. Additional records from Belize, Brazil: São Paulo and Egypt ( POLHEMUS 1995) suggest a possible pantropical distribution. There is also a doubtful record from ʻN.G. Nat. Ver.N. Holl.’ which TODD (1957b) interpreted as Australia. TODD (1959) wrote that it is not known whether ʻN. G.’ referred to New Guinea or ʻN. Holl.’ refers to New Holland, an old name for Australia. However, ANDERSEN & WEIR (2004) did not mention this species in their book on Australian water bugs, so apparently there are no other records of this species from Australia. Nerthra papaceki is similar to N. rugosa , ( Figs 28, 29 ; TODD 1955: 471, fig. 121). The lateral margins of the pronotum are straight in N. papacecki and somewhat convex in N. rugosa . More differences between these species are given below.

Please note that N. papaceki sp. nov. is based on a single male and four females. So far, no males of N. rugosa have been reported. TODD (1955: 470) gave the so far only illustration showing the outline of the female of N. rugosa . The differences between the females of these two species are listed in Table 1.

The presence or absence of an excavation in the anterior margin of the head is considered an important differential character in this genus ( TODD 1955); the remaining differences between the females of N. rugosa and N. papaceki sp. nov. further support that N. papaceki is an undescribed taxon. More material, specifically males and specimens from Brazil, Egypt, and Florida of N. rugosa is needed to further define the boundaries of variability of both species.

Figures

Figs 24–27. Nerthra papaceki sp. nov., holotype, male. 24–26 – habitus: 24 – dorsal view (cleaned, genital capsule removed); 25 – habitus, ventral view (cleaned, genital capsule removed); 26 – dorsal view (before cleaning, genital capsule extended). 27 – genital capsule (ventral view).

Figs 28–29. Nerthra papaceki sp. nov. paratype, female, habitus (28 – dorsal view, before cleaning; 29 – ventral view, cleaned).

Fig. 30. Nerthra papaceki sp. nov., paramere and pygophore (a – ventral view, b – dorsal view).

Figs 38–39. Distribution of treated Nerthra species: 38 – N. americana (Montandon, 1905), N. buenoi Todd, 1955 and N. papaceki sp. nov.; 39 – N. occidua Todd, 1959.

Figs 15–18. Nerthra spp., apex of paramere, ventral view: 15 – N. americana (Montandon, 1905); 16 – N. buenoi Todd, 1955; 17 – N. occidua Todd, 1959; 18 – N. raptoria (Fabricius, 1803).

Figs 1–4. Habitus of Nerthra americana (Montandon,1905):1–2 – male (1 – dorsal view, 2 – ventral view); 3–4 – female (3 – dorsal view, 4 –ventral view).