First records of the genus Pelionella Kaydan, 2015 in East Asia, with description of a new species (Hemiptera, Coccomorpha, Pseudococcidae)

Abstract Two mealybug species (Hemiptera: Coccomorpha: Pseudococcidae), Pelionella osakaensis sp. n. and P. manifecta (Borchsenius, 1949), are described and illustrated based on adult female specimens collected in Japan, on the Japanese mugwort Artemisia indica Willd. var. maximowiczii (Nakai) H. Hara (Asteraceae). These are the first records of the occurrence of Pelionella species in East Asia. The new species is similar to P. grassiana (Goux, 1989) and P. proeminens (Goux, 1990), but differs in lacking multilocular pores with double loculi rings on the venter and in possessing dorsal cerarii and a circulus. The Japanese population of P. manifecta is morphologically slightly different from the Azerbaijani and French populations in lacking large-type oral-collar tubular ducts associated with clusters formed by multilocular pores and oral-collar ducts on ventral abdominal segments III and IV. A modified key to species of the genus Pelionella Kaydan, 2015, is provided.


Introduction
A genus of Pseudococcidae (Hemiptera: Coccomorpha), Pelionella Kaydan, 2015, was erected by Kaydan (2015) for a genus related to Peliococcus Borchsenius, 1948, based on molecular and morphological analyses. Kaydan (2015) defined the genus Pelionella based mainly on three diagnostic characters: (i) the presence of a special type of multilocular pore, consisting of double rings of eleven loculi, mainly located within pore clusters on the dorsum; (ii) the absence of a type of dorsal seta similar to cerarian setae that lacks a trilocular pore near the basal socket and is not located on an elevated area; and (iii) the presence of one or two sizes of dorsal oral-collar tubular ducts, and smaller ducts present in the center of clusters of multilocular pores with double rings on the dorsum. To date, eleven species of the genus have been recorded from the Western Palearctic and Eastern Nearctic (García Morales et al. 2016;Kaydan 2015) but none from East Asia, including Japan, although some species of the genus Peliococcus have been recorded (Kwon et al. 2003;Tanaka 2017;Tang 1992). Peliococcus and Pelionella can be clearly recognized by some morphological differences, such as presence or absence of a special type of multilocular pore consisting of double loculi rings, and clusters formed by the pores and several types of oral-collar ducts mainly on the dorsal surface.
Recently, the author examined specimens of two species of Pelionella collected from Japan, and recognized among the samples the type species of the genus, Pelionella manifecta (Borchsenius, 1949), and a single specimen of an undescribed species. The former showed slight differences from western populations in some morphological character states. This paper describes or diagnoses and illustrates both species collected from Japan based on adult female morphology, and constitutes the first record of the occurrence of Pelionella species in East Asia. A modified key to species of the genus Pelionella is also given.
This new distribution record for P. manifecta, and the description of a new species of Pelionella with unique morphological features (i.e., presence of several dorsal cerarii distinctly elevated from dorsal surface) may be useful for understanding and furthering studies on the diversity, morphology, and biogeography of this genus and other related mealybug species.

Materials and methods
Examined materials were collected by I. Takahashi, J. Imai, or K. Fujimoto in the fall (from October to November) of 2014. The adopted slide-mounting method is a slight modification of Kawai (1980) which uses lemosol (95% limonen) as a substitute for xylene. Slide-mounted specimens were examined under a phase-contrast compound microscope (Olympus BH2-PH, Tokyo, Japan). The description format and morphological terminology mostly follow Kaydan (2015). The holotype material of the new species and the voucher specimens of P. manifecta examined in this study are deposited in the National Museum of Nature and Science, Tsukuba, Japan (NSMT). The remaining materials of P. manifecta examined and used for description in this study are deposited in the Dr. Kawai scale insect collection in Tokyo University of Agriculture.
Venter. Setae of two types: (i) slender hair-like setae, each 10-142 μm long, longest setae situated medially on head; and (ii) spine-like setae in submarginal areas, each 4-12 μm long. Apical setae of anal lobes 198-228 μm long. Multilocular disc pores with single ring, each 5.0-6.8 μm in diameter, present in 15-25 clusters on medial areas of abdominal segments III and IV; each cluster containing 1-5 (usually 2-3) multilocular disc pores surrounding a small oral-collar tubular duct; similar multilocular disc pores present also in single rows on other abdominal segments, as follows: V 7-8, VI 43-47, VII 62-69, VIII + IX 38-46. Multilocular pores with double rings, each 6.6-7.9 μm in diameter, restricted to submarginal areas of head, thorax, and abdomen, usually not arranged in clusters. Quinquelocular pores, each 3.2-5.6 μm in diameter, scattered medially on head, thorax, and medial area of abdominal segments. Trilocular pores, each 2.6-3.2 μm in diameter, scattered throughout. Minute discoidal pores, each 0.8-1.3 μm in diameter, few. Oral-collar tubular ducts of two sizes: small ducts restricted to within clusters; and large-sized ducts, each 2.1-2.9 μm wide, present on body margin and in single rows across posterior abdominal segments; also a few on head, thorax and abdominal segments II and III.
Discussion. The Japanese specimens of Pelionella manifecta described here differ slightly from the Azerbaijani and French material described by Kaydan (2015) in having many more multilocular disc pores on the venter of the abdominal segments, much smaller tubular ducts and pores (Table 1) and in lacking the large oral-collar tubular ducts associated with multilocular pore clusters on venter of abdominal segments III and IV. However, these morphological differences are herein tentatively regarded as intraspecific variation, because the number of tubular ducts and multilocular pores is known to vary greatly in some mealybug species (Cox 1983;Charles et al. 2000;Chatzidimitriou et al. 2016), considerable geographical morphological variation within P. manifecta has been also recorded (Kaydan 2015), and hitherto, the morphological variation of P. manifecta and taxonomic significances of the ducts' and pores' sizes have not been sufficiently studied. This description of the Japanese population may be useful for understanding phenotypic variation in the species. Future molecular studies may help elucidate the extent of variation in P. manifecta.
In Japan, this species was collected from Kansai International Airport, one of the largest airports in the country, and from the large sea-port island of Kobe City (Minato-jima), both of which are centres of international trade. Furthermore, the species has not hitherto been recorded further east than Kazakhstan. This suggests that the species  might not be truly endemic to Japan, but be a recent introduction. Studies of the detailed distribution of the species in Japan, and the current condition of the species at the sites where it was collected originally, may be important from both biological and plant-quarantine perspectives.
(NSMT-I-Ho 00081). Diagnosis. Eighteen pairs of cerarii present on body margin. Several slightly elevated dorsal cerarii also present on dorsal surface. Clusters of multilocular pores with double rings present on dorsum; each cluster contains 1-2 multilocular pores with double rings, 0-1 small oral-collar tubular ducts, 0-2 large oral-collar tubular ducts, and 0-3 minute discoidal pores. Multilocular pores with double rings and clusters of multilocular disc pores with single ring and oral-collar tubular ducts absent on venter. Circulus oval, present on posterior part of third abdominal segment of venter. Translucent pores absent on hind legs.
Etymology. The species is named after the prefecture in Japan where it was collected. Discussion. Pelionella osakaensis sp. n. is quite similar to P. grassiana (Goux, 1989) and P. proeminens (Goux, 1990) in having clusters containing one or two multilocular pores with double rings on dorsum and more than 16 pairs of cerarii. However, P. osakaensis differs from the latter species in having a circulus on the posterior part of the third abdominal segment, several slight elevated dorsal cerarii, and in lacking translucent pores on hind legs. Although the presence or absence of a circulus can be variable within a mealybug spe-cies, it may be a useful, readily observable diagnostic character for P. osakaensis given the current status of classification of Pelionella species. Pelionella osakaensis is also similar to P. stellarocheae (Goux, 1990) in lacking translucent pores on hind legs and in having smaller number of multilocular pores with double rings in each cluster on dorsum; however, it clearly differs from P. stellarocheae in having 18 pairs of cerarii plus dorsal cerarii. The presence of dorsal cerarii is one of the important features of P. osakaensis, although it may appear to conflict with the generic definition of Pelionella proposed by Kaydan (2015).
Here the importance of the presence of multilocular pores with double rings in the clusters is emphasized, so the new species is considered to belong to the genus Pelionella. Further research into the generic definition of the genus Pelionella is still much needed.
Pelionella osakaensis has only been collected from the site of Kansai International Airport, one of the largest airports in Japan, so it is possible that it is not endemic. A more detailed distributional study of the species and the current population level and distribution of the species at the airport may be important in relation to plantquarantine measures.