Physopelta Amyot & Serville, 1843

Souma, Jun & Ishikawa, Tadashi, 2021, A taxonomic review of the genus Physopelta (Hemiptera: Heteroptera: Largidae) from Japan, Korea, and Taiwan, with a new record of Ph. parviceps from China, Zootaxa 4951 (3), pp. 461-491 : 463-464

Genus Physopelta Amyot & Serville, 1843

Physopelta Amyot & Serville, 1843: 271 .

Type species by subsequent designation ( Hussey 1929: 28): Physopelta erythrocephala Amyot & Serville, 1843 [= Cimex albofasciatus DeGeer, 1773 ].

Diagnosis. Recognized among other largid genera by a combination of the following characters: head as long as its maximum width across compound eyes; antennomere III more than 0.5 times as long as antennomere IV; labium reaching between meso- and metacoxae; lateral margin of pronotum not or slightly emarginate between calli and disc, always without wrinkle; calli sometimes more convex in male than in female; fore wing in male longer than abdomen; corium of fore wing always without wrinkle; procoxa sometimes with a projection (procoxal projection); protrochanter sometimes with wrinkles (protrochanteral wrinkles); all femora in male sometimes with two longitudinal furrows throughout its length in ventral surface; longitudinal furrow of all femora in male always with a single row of denticles; profemur sometimes wider in male than in female; male protibia sometimes with a single tooth in apical part and/or a single row of denticles throughout its length ventrally; parameres curved inward, widest in basal apodeme, not crossing each other in rest, not surpassing infolding of ventral rim of genital capsule; crown of paramere with a number of setae on dorsal and ventral surfaces; and crown of paramere apically narrowed, rounded at apex.

Remarks. Physopelta strongly resembles the genus Delacampius Distant, 1903 , but the former can be distinguished from the latter by the following characteristics: antennomere III more than 0.5 times as long as antennomere IV; calli sometimes more convex in male than in female; lateral margin of pronotum not or slightly emarginate between calli and disc, always without wrinkle; corium of fore wing always without wrinkle; procoxa sometimes with a horn-shaped projection (procoxal projection); and protrochanter sometimes with wrinkles (protrochanteral wrinkles). In contrast, Delacampius has the following features: antennomere III approximately 0.5 times as long as antennomere IV; calli equally convex in both sexes; lateral margin of pronotum deeply emarginate between calli and disc, sometimes with several wrinkles (stridulatory organ); corium of fore wing sometimes with several wrinkles (stridulatory organ); procoxa always without projection; protrochanter always without wrinkle.

In the genus Physopelta , four subgenera are currently recognized: Afrophysopelta and Physopeltoides from the Afrotropical Region, Neophysopelta from the Oceanian, Oriental, and Palaearctic Regions, and the nominotypical Physopelta from the Oriental Region ( Stehlík 2013). Five species of Physopelta , all belonging to Neophysopelta , have been known from Japan, Korea, and Taiwan: Ph. (N.) cincticollis, Ph. (N.) gutta gutta, Ph. (N.) parviceps, Ph. (N.) quadriguttata , and Ph. (N.) slanbuschii ( Stehlík 2013; Ishikawa 2016). Conclusively, we recognize five species of Physopelta , all belonging to Neophysopelta , from Japan, Korea, and Taiwan: Ph. (N.) gutta gutta, Ph. (N.) fusciscutellata sp. nov., Ph. (N.) lutaspidata sp. nov., Ph. (N.) parviceps , and Ph. (N.) quadriguttata .

Species of the subgenera Physopelta s. str. and Neophysopelta have sexual dimorphism in the swelling degree of the calli, the width of the femur, and the curvature of the protibia ( Stehlík 2013). Sexual dimorphism is more distinct in larger male than in smaller male ( Stehlík 2007).

Physopelta species were diagnosed by previous authors based on the differences in the morphological characteristics such as body shape, size of the compound eye, shape of the antenna, and the presence or absence of the procoxal projection and protrochanteral wrinkles (e.g. Stål 1863; Blöte 1931; Rédei et al. 2009; Kohno et al. 2012; Stehlík 2013). These characteristics are also useful for the identification of the new species described below. In addition, the structure of male and female terminalia provide good characters for identification among at least the eastern Asian species.

An apparatus consisting of a projection of procoxa and wrinkles of the protrochanter has been named “stridulatory organ” by Stehlík (2013); however, the stridulatory behavior of Physopelta species has not been observed so far. Also, the procoxal projection on procoxa in Ph. (N.) parviceps is present in macropterous morph but is absent in brachypterous morph, and Ph. (N.) lutaspidata sp. nov. has only the wrinkles in the protrochanter. Therefore, a horn-shaped projection of procoxa and wrinkles of the protrochanter are here renamed as procoxal projection and protrochanteral wrinkles, respectively.

The antennomeral oligomery is confirmed in Ph. (N.) gutta gutta ( Fig. 1A ) and Ph. (N.) parviceps ( Fig. 2B, F ). These three individuals lack antennomere III. Similar teratological forms are known in Cimicomorpha Leston, Pendergrast & Southwood, 1954, Gerromorpha Popov, 1971, Leptopodomorpha Popov, 1971, and Pentatomomorpha ( Leston 1952; Štusák & Stehlík 1978; Yasunaga 2018; Taszakowski & Kaszyca-Taszakowska 2020, etc.). Thus, the antennomeral oligomery may be common in other Physopelta species as other heteropterans.

Although only dozens of individuals are found on their host plants at noon, hundreds of individuals of Physopelta species are sometimes attracted to artificial light at night ( Fig. 17 ). On the other hand, Ph. (N.) gutta gutta was collected from a volcanic island, whose flora does not include its host plants, Mallotus japonicus (L.f.) Müll.Arg. ( Euphorbiaceae ) and its close relatives (cf. Ohba 1989; Komatsu et al. 2009). Thus, some species of Physopelta appears to have strong phototaxis and flight ability.

Figures

FIGURE 1. Habitus images of four Physopelta (Neophysopelta) species, dorsal view: Ph. (N.) gutta gutta, male (A) and female (B) from Japan proper; Ph. (N.) fusciscutellata sp. nov., male from the main island of Taiwan (C) and female from the Ryukyu Islands, Japan (D); Ph. (N.) quadriguttata, male (E, G) and female (F) from the main island of Taiwan; Ph. (N.) lutaspidata sp. nov., male from the main island of Taiwan (H). Arrows mark antenna with antennomeral oligomery and malformed calli. Scale bar: 5.0 mm.

FIGURE 2. Habitus images of Physopelta (Neophysopelta) parviceps, dorsal view: macropterous male (A) and female (B) from Japan proper; macropterous male (C, E) and female (D, F) from the Ryukyu Islands, Japan; brachypterous male (G) and female (H) from Japan proper. Arrows mark antennae with antennomeral oligomery. Scale bar: 5.0 mm.

FIGURE 17. A number of individuals of Physopelta (Neophysopelta) quadriguttata from the main island of Taiwan attracted to artificial light.