A new earwig of the genus Echinosoma from Penang Island, Peninsular Malaysia, with notes on the taxonomic and nomenclatural problems of the genus Cranopygia (Insecta, Dermaptera, Pygidicranidae)

Abstract The pygidicranid earwigs (Dermaptera) of Penang Island, Peninsular Malaysia were re-examined based on material collected in extensive field surveys in 2012–2013 and 2015. Echinosoma roseiventre Kamimura & Nishikawa, sp. n. is described and illustrated, and Cranopygia pallidipennis (de Haan, 1842) is reported from the island for the first time. The taxonomic and nomenclatural problems of the genus Cranopygia sensu Hincks (1959) [A Systematic Monograph of the Dermaptera of the World. Part II. Pygidicranidae excluding Diplatyinae. British Museum (Natural History)] are also discussed. For the members of the subfamily Pygidicraninae from Indo-Austral and Oriental regions, the system, definitions of genera, and key of Hincks (1959) are followed. The genus Mucrocranopygia Steinmann, 1986 is synonymized with Cranopygia Burr, 1908. A key to the males of small Echinosoma from the Oriental region is provided.


Introduction
Penang Island (Pulau Pinang) is a 299-km 2 island located in the Straits of Malacca, approximately 5 km from the western coast of the mainland of Peninsular Malaysia. Thirty-one species of Dermaptera (earwigs) from this small tropical island are reported, based on an extensive field survey conducted in 2012-2013 (Kamimura et al. 2016), including an undescribed species of the genus Echinosoma Audinet-Serville, 1839 (Pygidicranidae). An additional field survey by the first author (YK) in 2014 resulted in the discovery of a species from the genus Cranopygia Burr, 1908 (Pygidicranidae) sensu , which was not collected during the 2012-2013 survey (Kamimura et al. 2016). Cranopygia similis  was recorded from "Penang" (Burr 1910 in the early 20 th century, although whether it was collected on the island or from the mainland state of Penang is unclear. Based on a comparison of the samples collected during our surveys with material preserved in museums, the identity of Cranopygia from Penang Island is discussed, as well as the taxonomic and nomenclatural problems of the genus Cranopygia sensu .

Methods
An extensive field survey of earwigs was conducted on Penang Island from March 2012 to March 2013 (see Kamimura et al. 2016 for details). Based on the samples collected during this survey a new species of Echinosoma is described. The type material of the new species and some representative samples collected during this study will be deposited in the collections of the Osaka Museum of Natural History (OMNH; Osaka, Japan) and the Lee Kong Chian Natural History Museum (LKC-NHM; Singapore).
An additional field survey was conducted by YK on 9-13 March, 2015, during which time two Cranopygia samples were collected from Bukit Jambul (5.348821N, 100.285692E). The site is a hill with a maximum elevation of approximately 200 m a.s.l that is covered with plantations of rubber, durian, banana, and other fruit trees, and is surrounded by secondary forests. A nymphal sample collected this location was reared to adulthood in the laboratory. For comparison, we examined specimens of Cranopygia species from Manchester Museum (MM) and the Natural History Museum (NHM), UK, and the entomological specimen collections of the School of Biological Sciences, Univerisiti Sains Malaysia, Penang, Malaysia.
Male and female genitalia removed from the examined specimens were mounted in Euparal (Waldeck GmbH & Co. KG, Münster, Germany) between two cover slips, and attached to the pin of the respective specimen. The terminologies of Klass (2003) and Kamimura (2014) are used for female and male genital structures, respectively.
Color: General body color dull smoky black but abdomen, especially caudal part, pygidium, and forceps reddish brown or rosy (Fig. 1a). Mouth parts brownish. Antennae dark brown except for first three segments dirty white. Legs dirty white but femora with a broad fuscous band near the base. Caudal margin of tegmina with distinct, narrow whitish band. First abdominal segment whitish. Body covered with obtuse bristles sparsely. Head (Fig. 2) slightly broader than long; frons convex; transverse and median suture indistinct; caudal margin feebly emarginated in middle. Antennae (Fig. 3); 17 segments (left side partly broken, 16 segments remaining), segments mostly stout; 1 st expanded apically, nearly half long as the distance between antennal bases; 2 nd short, quadrate, almost as long as broad; 3 rd long, twice as long as broad; 4 th and 5 th short, as long as broad; 6 th and beyond gradually becoming longer and narrowing basally rendering some segments subpyriform. Eyes long, approx. as long as the post-ocular length. Post-ocular margin with a row of five long bristles. Pronotum (Fig. 2) broader than long; surface rough; sides rounded; frontal and caudal angles weakly and strongly rounded, respectively; caudal margin convex with distinct emargination in middle; prozona distinctively raised; median sulcus week but visible; row of long bristles on frontal and lateral margins. Tegmina almost as long as pronotum; surface rough; humeral angle weak and anal angle shortly rounded off to show a small, triangular scutellum; caudal margin obliquely truncate, outer and caudal margins with long bristles. Hind wings wanting. Legs stout; femora not compresed, ecarinate; arolium small; hind tarsi with 1 st segment longer than the third. Abdomen stout, more or less parallel-sided, except first three segments narrowed; sides of segments almost straight; tergites with scattered granules or very short obtuse bristles with whitish apex; first two tergites and lateral sides of 3 rd tergites onward with long bristles near caudal margins. Penultimate (c, d, h, i) male genitalia; (f) female genitalic region and ovipositor. The red and blue arrowheads indicate the expanded outer angle of the parameres (c) and the distal process of the virgae (c, d, i), respectively. Abbreviations: AP, anal plate; ce, cercus (=forceps); gl8, gonoplac (=coxal lobe) VIII ; gl9, gonoplac (=coxal lobe) IX; gp8, gonapophysis VIII; gp9, gonapophysis IX; LC9, laterocoxa IX; LP, lateral plate; TG8-TG10, tergum VIII-X. Scale bars: 3 mm in a, b, e, and g; 1 mm in c, f and h; 200 µm in d and i. sternite ( Fig. 4) transverse, narrowed posteriorly with caudal margin being nearly half of the anterior, widely emarginated. Ultimate tergite (Fig. 5) transverse, with small rounded swellings above the base of forceps; caudal margin almost straight. Pygidium short, rectangular, transverse. Forceps (Fig. 5) short, strongly curving inwards, tapering apically; surface, smooth at tips. Genitalia (Figs. 6-9) with slender, finger-like parameres with obtuse tips and broad base (Fig. 7); penis lobe almost twice length of parameres; virga very long, more than five times longer than parameres, tubular and simple (Figs 6,8); penis lobes also enclose a funnel-shaped sclerite at the base of virga, and a long ellipse sclerite distally (Fig. 9). Paratype (male). Length of body (without forceps), 6.5 mm; length of forceps, 0.8 mm; head width, 1.2 mm; pronotum width, 1.2 mm; pronotum length, 0.8 mm. Antennae broken, five (right) and eleven (left) segments remaining. Tegmina longer, approx. 1.5 times longer than pronotum. Penultimate sternite not strongly narrows posteriorly, almost rectangular.
Distribution. Penang Island, Peninsular Malaysia Etymology. The specific epithet refers to the characteristic rosy abdomen of this new species.
Remarks. Echinosoma roseiventre sp. n. is very close to E. andamanensis Srivastava, 1988, described from India. Currently these two species can only be distinguished by differences in the length of the virgae (shorter than five times the parameres in E. andamanensis), the shape of the pygidium (longer than broad in E. andamanensis), and body coloration (E. andamanensis is generally dull smoky black but the abdomen, pygidium, and forceps are shiny; Srivastava 1988).
In addition to the species listed in the key below, E. rufomarginatum Borelli, 1931, which Hincks (1959,  and Srivastava (1988) treated as a doubtful species, also has a small body size (body length with forceps of ~11 mm; . However, according to the original description by Borelli (1931), the male penultimate sternite of this species has a very deep emargination on the caudal margin.
The male genitalia of E. burri , recorded from Java and Sumatra, are very similar to those of E. roseiventre sp. n., but the body size is much larger (male body length with forceps of 18-20 mm; . Key to the small Echinosoma species (body length + forceps = 10 mm or less) from the Oriental Region (males only) Remarks. First record for Penang Island.

Problems in the taxonomic treatment of Cranopygia Burr sensu Hincks (1955)
Within the family Pygidicranidae, the subfamily Pygidicraninae Verhoeff, 1902 is characterized by a medium to large body size (rarely less than 20 mm), antennae with 25 segments or more in which the 4 th and 5 th are wider than they are long, depressed femora, and equally developed right and left penis lobes , Srivastava 1988). Indo-Austral and Oriental species of this subfamily are usually classified in the genus Tagalina Dohrn, 1863, in which the second tarsal segments are characteristically enlarged, or the genus Cranopygia Burr, 1908sensu Hincks (1955. The taxonomy of the latter is rather unstable and unsettled. Including this group, for several species that were formerly in the genus Pygidicrana Audinet-Serville, 1831,     were apparently unknown to Zacher, which resulted in a lack of agreement as to how to distinguish between Cranopygia and Kalocrania (see  for more details). To settle this problem,  consistently examined the male genitalia of this group for the first time, and redefined the genus Cranopygia based on the shape of the virga. Simultaneously, Pyge was synonymized with Kalocrania, and a new genus Acrania was established (type species, Pygidicrana picta Guérin-Méneville, 1838). , who examined the genital armatures for many more species in this group, concluded that Cranopygia, Kalocrania, and Acrania could not consistently be distinguished based on their genital morphologies, and he later synonymized the latter two genera with Cranopygia, with the formation of five species groups . Several species formerly in the genus Dicrana were also included in Cranopygia by . Nearly 25 years later,  erected three new genera, Epicranopygia (type species: Pygidicrana picta Guérin-Méneville, 1838), Mucrocranopygia (type species: Pygidicrana horsfieldi Kirby, 1891), and Paracranopygia (type species: Forficula pallidipennis de Haan, 1842), for the species of Cranopygia sensu  with virgae that were not straight. Srivastava (1993a) considered that the traits for diagnosing these genera (i.e., the shapes of the penis lobes and the virgae) were unstable and therefore unsuitable for generic classification. Instead, he focused on the shape of the parameres, which are robust and resistant to the artifacts of mounting, and reinstated Acrania for species with parameres that are neither knobbed nor hooked externally or internally (but occasionally with a slight convexity of the external apical angle). Engel and Haas (2007), who omitted to cite Srivastava (1993a), noted that the generic names Acrania and Pyge, which Steinmann (1986) considered invalid, were available for the group containing the respective type species. Accordingly, they reinstated Acrania and Pyge, making Epicranopygia and Paracranopygia junior objective synonyms. Although they did not provide the species lists for Cranopygia and Mucrocranopygia (sensu Steinmann 1986), Engel and Haas (2007) followed  taxonomic system for the subfamily, except for the abovementioned changes in generic names. Srivastava's (1993a) taxonomic treatment is also problematic. He reinstated Acrania, the type species of which is Pygidicrana picta Guérin-Méneville, 1838. However, he simultaneously synonymized Epicranopygia, which was created with the same type species (P. picta), with Cranopygia. According to his list of new combinations, Srivastava (1993a) transferred three species of Epicranopygia to Cranopygia, but transferred three others, including E. picta, to Acrania. Thus, the declaration of synonyms in Srivastava (1993a), and those cited in subsequent papers (Srivastava 1993b(Srivastava , 1995 are incorrect: Srivastava (1993a) synomyzed Epicranopygia (pars) and Paracranopygia (pars) with Acrania and Cranopygia.
Subsequently, Sakai (1996Sakai ( , 2000 generally followed Srivastava's (1993a) system (and possibly the identification key), but concurrently adopted  species-group level classification. However, instead of using the C. siamensis species group , he treated Paracranopygia as a valid subgenus for most species of Paracranopygia sensu , as well as including C. tianshanskyi and C. chirurga, which were originally described by Gorochov and Anisyutkin (1993) under the genus Paracranopygia.
In addition to these nomenclatural problems, recent studies have shown that the morphology of earwig virgae, particularly the length, evolves rapidly due to sperm competition, resulting in considerable variation even among very closely related congeners (Kamimura 2000, 2014, Lieshout and Elgar 2011. Therefore, although useful for species diagnosis, generic classification systems based primarily on virgal characteristics (e.g., length, convolution) likely do not reflect accurately the phylogenetic relationships. In contrast, the functional significance of male genital parameres is largely unknown for earwigs (Kamimura 2014). Nevertheless, the presence or absence of a tooth or process of the parameres, which Srivastava (1993a) proposed to distinguish Cranopygia and Acrania, is also likely an unreliable trait for the generic classification of this group. For example, male Cranopygia vittipennis Hincks, 1955 have a tiny process at the outer angle of the paramere, whereas a similar but weaker process is found in Acrania luzonica (Brindle, 1955) in the equivalent position (compare figs. 2 and 12 of Srivastava 1993a). A similar observation was made for Cranopygia pallidipennis from Penang Island, which is described below. Therefore, for the taxonomy of pygidicranine earwigs, we propose to follow the system, definitions of the genera, and key of ; that is, all of the species from Indo-Austral and Oriental regions (except for some species of Dacnodes) are classified either in the genera Tagalina (species with an enlarged second tarsal segment) or Cranopygia (species with a simple second tarsal segment). Accordingly, we propose to place all of the following species in the genus Cranopygia.
is a member of the contemporary earwig fauna of the island, whereas the identity of Burr's specimen of Cranopygia from "Penang" requires further investigation including determining the exact location from which it was collected.