A New Record of Proreus simulans (Dermaptera: Chelisochidae) in Korea

Abstract

The earwig Proreus simulans($St{\aa}l$, 1860) has been recently reported from Jeollanam-do in the far southern section of the Korean Peninsula. Natural photographs of this species were obtained from Gwangyang Province for the first time in 2013, with specimens being physically collected in light traps from Suncheon Province in 2018. The species is widely distributed throughout the Oriental region, where its main habitat is lowland paddy fields. The earwig belongs to family Chelisochidae, subfamily Chelisochinae, and genus Proreus, which are newly recognized in Korea. The diversity of the order Dermaptera is currently estimated to be 6 families, 14 genera, and 24 species in Korea.

INTRODUCTION

Since the first record of Opisthocosmia komarowi(now Timomenus komarowi) by Semenov (1901) in Korea, the diversity of the order Dermaptera has been summarized as containing 11 species in the study by Kamijo (1934), 16 species in the study by Cho (1969), and 17 species in the study by Kim and Moon (1985). However, a number of new species or newly recorded species have occasionally been reported, including Gonolabis distincta (now Mongolabis distincta) in a study by Moon (1993), Challia taewooi and C. gigantia in a study by Nishikawa (2006a), Anisolabis seirokui in a study by Nishikawa (2008), Labia minor in a study by Nishikawa and Han (2015), and Spongovostox sakaii in a study by Kim and Nishikawa (2017).

An unrecognized earwig was photographed by the second author of the present study in Gwangyang Province in the southern part of the Korean Peninsula in 2013 (Fig. 1A, B). It was temporarily identified as Proreus simulans by the first author; however, owing to the specimen not being physically collected at the time, only the photographs were privately presented on an internet blog (Kim, 2018). Since then, collection attempts of this species to confirm its occurrence in the same locality have failed. Finally, this species was collected in light traps in 2018 from the neighboring southern locality, Suncheon Province. Consequently, its characters were studied in detail and its identity confirmed in the present study as Proreus simulans. The Oriental earwig belongs to family Chelisochidae, subfamily Chelisochinae, and genus Proreus, which are newly recorded in Korea. In the present study, the systematic terminology used is that referred to by Steinmann (1986).

Fig. 1. Natural photographs of Proreus simulans. A, B, Male (31 Jul 2013, Gwangyang Province); C, D, Female (12 Sep 2018, Suncheon Province).

SYSTEMATIC ACCOUNTS

Order Dermaptera De Geer, 1773

Family Chelisochidae Verhoeff, 1902

Diagnosis. Body stout or robust, moderately depressed; antennomeres cylindrical or subcylindrical, 4th usually shorter than 3rd, often subconical; pronotum generally widened posteriorly and rarely transverse; tegmina perfect or abbreviated, keeled or smooth; wings generally well developed; legs rather short and compressed; 2nd tarsomere with narrow ventral lobe produced beneath 3rd tarsomere.

Distribution. Ethiopian, Oriental, and Indo-Australian regions(three subfamilies). New to Korea.

Subfamily Chelisochinae Verhoeff, 1902

Diagnosis. Head with well-marked postfrontal and coronal sutures; tegmina and wings present, lateral margin of tegmina without ridge-like edge; posterior margin transverse or obliquely truncate; wings absent or sometimes fully developed; tibiae not obviously flattened laterally, or sulcate or flattened only at distal apex. Male genitalia well developed, distal lobe prominent; external parameres vary.

Distribution. Ethiopian, Oriental, and Indo-Australian regions(13 genera). New to Korea.

Genus Proreus Burr, 1907

Proreus Burr, 1907: 129; 1910: 136; 1911: 64; Bey-Bienko, 1936: 117; Srivastava, 1976: 49; Steinmann, 1993: 99; Chen and Ma, 2004: 195.

Type species: Forficula simulans Stål, 1860.

=Erotesis Burr, 1910: 114 (type species: Spongiphora sphinx Burr, 1900).

Diagnosis. Body slender and small; antennae slender, cylindrical, 5th antennomere longer than 3rd; 4th antennomere cylindrical or ovate, never clubbed nor conical; tegmina and wings developed; legs moderately short; tibiae with groove or at least flattened near extreme; abdomen cylindrical, lateral sides gently curved; forceps well developed; male parameres typical, with basal vesicle.

Distribution. Oriental and Indo-Australian regions (18 species). New to Korea.

Proreus simulans(Stål, 1860)(Figs. 1-3)

Forficula simulans Stål, 1860: 302 (type locality: Java, male, type deposited in Naturhistoriska riksmuseet, Stockholm).

Forficula modesta Stål, 1860: 302 (type locality: Hongkong, male).[synonymized by Burr, 1911]

Fig. 2. Habitus of Proreus simulans. A, Male dorsal view; B, Male ventral view; C, Female dorsal view; D, Female ventral view.

Fig. 3. Terminalia of Proreus simulans. A, Male forceps dorsal view; B, Male genitalia extracted between forceps ventral view; C, Female forceps dorsal view.

Lobophora simulans: Dohrn, 1865: 74.

Lobophora modesta: Dohrn, 1865: 74.[synonymized by Burr, 1911]

Chelisoches simulans: Scudder, 1876: 309; Bormans and Krauss, 1900: 87, fig. 34; Kirby, 1904: 34.

Spongiphora sphinx Burr, 1900: 91 (type locality: Sarawak, Male and Female). [synonymized by Burr, 1911]

Labidurodes formosanus Shiraki, 1906a: 92, fig. 2 (type locality: Formosa, Female not male, see Nishikawa, 2005).[synonymized by Shiraki, 1928]

Labidurodes okinawaensis Shiraki, 1906b: 189 (type locality: Okinawa, Male and Female). [synonymized by Burr, 1913]

Proreus simulans: Burr, 1907: 131; 1910: 137, fig. 85; 1911: 64, Pl. 5, fig. 21, Pl. 6, fig. 3; 1916: 9, Pl. 2, fig. 8; Shiraki, 1928: 14; Bey-Bienko, 1936: 118; Nishikawa, 1975: 66; 1996: 119; 2005: 1, figs. 1-3, 7-10; 2016: 182, figs. 08- 09, -10, -11; Srivastava, 1976: 50; Barrion and Litsinger, 1985: 25; Sakai, 1986: 21 (1101), 71 (1151); 1987: 1240, Pl. 20, 1243-1, Pl. 24; 1989: 151, Pl. 16, fig. 87; 2000a: 192; 2000b: 49; Azuma et al., 1987: 189; Hirashima, 1989: 60; Steinmann, 1993: 112, figs. 181-183; Chou, 1998: 160; Chen and Ma, 2004: 197, fig. 97a-c, Pl. IV-15.

Erotesis sphinx: Burr, 1910: 114. [synonymized by Burr, 1911]

Redescription. Body smaller, slender. General coloration orange-red or yellowish-brown, varied with tawny; tegmina and wings yellowish-orange with median dark black margins, legs yellow, forceps red-brown. Head depressed, orange-red; frons slightly tumid; postfrontal sutures and coronal suture distinct, posterior margin weakly concave; compound eyes small, black, considerably shorter than length of head behind eyes; antennae darkish, 17-19 segmented; scape thickly well developed, yellow cylindrical, elongate, narrower in base, as long as distance between both antennal cavities; pedicel smallest, quadrate; 3rd antenomere slightly longer than 4th; 5th antenomere almost as long as 3rd; remaining flagellums more elongated, all cylindrical and slender; maxillary and labial palps bright yellow. Pronotum depressed, orange-red, 1.2 times longer than wide; longitudinal furrow distinct, darkish; anterior margin truncate, slightly narrower than posterior margin of head, anterior angle obtuse; posterior margin slightly widened, convex, posterior angles rounded; lateral margins straight; prozona 1.2 times longer than metazona. Prosternum 2 times longer than wide with posterior margin truncated; mesosternum as long as wide, wider than prosternum with posterior margin truncated; metasternum shorter than wide, wider than mesosternum with posterior margin emarginated. Tegmina orange-yellow, rather narrow, as long as combined lengths of head and pronotum, narrow dark band along the suture and costal fields on lateral margins; lateral ridge absent; posterior margin truncate; wings prominent, surpassing tegmina, covering on 3rd abdominal tergite, tranparent when fully expanded. Legs short, orange-yellow; lengths 1st<2nd<3rd; tibiae adequately shorter than femora; 2nd tarsomere smallest with a narrow ventral lobe prolonged beneath 3rd; 1st tarsomere as long as 3rd; claws simple, symmetrical; arolium not developed. Abdomen red-brown, rather broad, dilated in the middle; lateral glandular folds distinct on 3-4 tergites, more blackish dark; forceps well developed, stout and larger in male.

Male (Figs. 2A, B, 3A, B): Length with forceps 14.5-14.7 mm, tegmina 2.7-2.8 mm, forceps 3.5-3.8 mm. Ultimate tergite broad, rectangular, pair of small compressed tubercles in the middle, and crenulated obtuse projections on each side; posterior margin gently sinuate; pygidium small and short, transverse rectangular; penultimate sternite broadly rounded with posterior margin narrowly truncated; forceps depressed with straight outer margins and branches remote at the base, thick more proximally rather than gradually slender towards apex, incurved and weakly upcurved; inner margin with sharp triangular big tooth near median portion, and second smaller tooth near apex; inner margin smooth from base to big tooth, crenulated between both teeth, almost smooth from smaller tooth to apex. Genitalia (Fig. 3B) very narrow shaped; virga within genital lobe very long; external parameres moderately broad at distal part, very acuminate apex.

Female (Figs. 2C, D, 3C): Length with forceps 13.4-14.5 mm, tegmina 2.6-3.1 mm; forceps 3.5-4.0 mm. Similar to male in size and coloration, sexual differences not significant. Ultimate tergite without remarkable tubercles in the middle, hardly crenulated obtuse projections on each sides; posterior margin gently sinuate; pygidium slightly larger than male, transverse trapezoidal, posterior margin narrowly truncated with acute lateral angular marginations; penultimate sternite broadly rounded; forceps almost straight, gradually slender towards apex, incurved and weakly upcurved; inner margin without big tooth, but serrulated two-thirds from the base to apex as double rows among these dorsal, one scarce only presented in middle portion.

Material examined (8 specimens). Korea: 2 males and 6 females, Jeollanam-do, Suncheon-si, Haeryong-myeon, 522- 1 Nongju-ri, light trap, 12 Sep 2018, leg. Kim Sangsu (voucher specimens deposited in the National Institute of Biological Resources).

Distribution. New to Korea (Jeollanam-do: Gwangyang, Suncheon), China (Guangxi, Hainan, Yunnan, Hongkong), Japan (Ryukyu Islands), Taiwan, Philippines, Vietnam, Myanmar, Thailand, Malaysia, Singapore, India, Indonesia (Borneo, Java, Sumatra), Bismarck Islands: widely distributed throughout the Oriental region.

Remarks. This species is mainly found in or near lowland paddy fields(Fig. 5), the macropterous forms are well attracted into light traps as shown in this collection (Fig. 4A-C). Earwigs often hide inside grass leaves during daytime to use as refuge or main habitats, and thus regarded as important predator of leaf folders(Pelopidas mathias) on rice or as the natural enemy of the Oriental maize borer(Ostrinia furnacalis) in the Philippines(Barrion and Litsinger, 1985). However, earwigs are regarded as a nuisance when they fly in mass populations inside houses(Nishikawa, 2016).

Fig. 4. Collection method (light trap).

Fig. 5. Map of collection location (Jeollanam-do, Suncheon-si, Haeryong-myeon, 522-1 Nongju-ri)

Table 1. Checklist of Korean Dermaptera​​​​​​​

DISCUSSION

Korean Dermaptera was intensively studied between 1983 and 1995 (Moon and Kim, 1983, 1985a, 1985b, 1991; Kim and Moon, 1985; Moon, 1985, 1993; Moon and Lee, 1995a, 1995b). However, owing to it being a smaller order with only a few species for taxonomic study was standing still on the way in Korea, besides which concern was shift towards conservational studies(Yoon and Moon, 1996, 1997).

Because more than 20 years has passed since that period, it is informative to present a brief list of the Dermaptera species found in Korea (Table 1). There are some questionable species contained in this list in which the real specimens have not been reconfirmed since the first records, for example C. fletcheri, F. auricularia, F. mikado, and Eparchus yezoensis (see Moon and Kim, 1991; Nishikawa, 2006a). However, it is reasonable to maintain these species in this list if there is no clear evidence for it to be excluded from the Korean fauna. Because the Korean Peninsula has been divided into two political countries since 1945, this order has not been comprehensively studied throughout North Korea. Besides, the cosmopolitans or Oriental earwigs have recently been found in South Korea (Kim and Nishikawa, 2017), which have been continuously reported. The current diversity of the order Dermaptera is estimated to be 6 families, 14 genera, and 24 species(including 1 subspecies) in Korea.