﻿A study of the mealybug genus Planococcus Ferris, 1950 from China, with description of a new species (Hemiptera, Coccomorpha, Pseudococcidae)

﻿Abstract A study of the mealybug genus Planococcus Ferris, 1950 (Hemiptera, Coccomorpha, Pseudococcidae) known from China is presented and 12 species are recognised. Of these, Planococcuscamelliae Zhang, sp. nov. is described as new to science based on the morphology of the adult female, and P.bambusifolii (Takahashi, 1951) is recorded from China for the first time. Molecular analyses based on the mitochondrial gene cytochrome c oxidase subunit I (COI) of the new species and a key to species of the genus Planococcus in China are also given.


Introduction
The genus Planococcus was erected by Ferris (1950) with the citrus mealybug Dorthesia citri Risso, 1813, as the type species, and now comprises 48 species worldwide (García Morales et al. 2016).The genus Planococcus includes some well-known pests, such as Planococcus citri (Risso, 1813) on citrus, P. ficus (Signoret, 1875) on grapevines, and P. lilacinus (Cockerell, 1905) and P. minor (Maskell, 1897) on cacao (Cox 1989;Williams 2004), which are often intercepted during quarantine inspections.In China, P. lilacinus and P. minor became the top two quarantine scale insects intercepted by China inspection and quarantine on imported plants and plant products from 2005 to 2014 (Gu et al. 2015).

Sampling and morphological identification
Slide-mounted specimens were prepared using the methods of Borchsenius (1950), stained in acid fuchsin, and mounted in Canada balsam.Terminology follows that of Hendricks and Kosztarab (1999) and Williams (2004).Measurements were taken from six specimens.Measurements are given in micrometres (μm) except for the length and width of the body that are in millimetres (mm).Only the known host plants and distribution of each species in China are listed.
Slides of the new species are deposited at the College of Forestry, Jiangxi Agricultural University, Nanchang, China (CFJAU) and the Insect Collection of the Southwest Forestry University, Yunnan, China (SWFU).

Taxonomy
Genus Planococcus Ferris, 1950Planococcus Ferris, 1950: 164. Allococcus Ezzat & McConnell, 1956: 13.Diagnosis.(adapted from Williams 2004).Body of adult female elongate oval to broadly oval.Antennae each with seven or eight segments.Legs well developed, with translucent pores on hind coxa and usually with some on hind tibia, claw without a denticle.Circulus present or absent.Ventral surface of each anal lobe with long apical seta, anal lobe bar and bar seta present.Cisanal setae either longer or shorter than anal ring setae.Anterior and posterior pairs of ostioles present.Marginal cerarii usually 18 pairs, each bearing two conical setae, or some paired flagellate setae, sometimes one or two cerarii of head, each with 3-5 setae; auxiliary setae usually absent, except for anal lobe cerarii.Trilocular pores usually evenly distributed.Oral collar tubular ducts situated on venter, always on abdomen and sometimes on head and thorax; often with indistinct rims when present on dorsum (sometimes termed modified oral collar tubular ducts).Multilocular disc pores rarely present on dorsum, always present on venter of abdomen.Body setae flagellate or short and stiff, sometimes knobbed at apex or almost lanceolate, conical.Discoidal pores present, sometimes larger than trilocular pores.(Ezzat and McConnell 1956;Borchsenius 1962a;Tu et al. 1988;Cox 1989;Martin and Lau 2011).Distribution.Hongkong, Taiwan, Yunnan (Borchsenius 1962a;Tu et al. 1988;Martin and Lau 2011).

Key to adult females of
Remarks.Good descriptions and illustrations of the adult female can be found in Ezzat and McConnell (1956), Tu et al. (1988), andWilliams (2004).Remarks.This is the first record of this mealybug in China.A good description and illustration of the adult female was given by Williams (2004).Other material examined.1 ♀ (mounted on 1 slide), same data as holotype (CFJAU); 8 ♀♀ (mounted on 7 slides), same collection and host plant as holotype, 4.viii.2018,coll.Jiang-tao Zhang (CFJAU).

Planococcus camelliae
Description.In life body oval, covered in white mealy wax, with ~ 18 pairs of short lateral filaments around body margin, found inside ant nests or tents on Camellia oleifera branches and fruits (Fig. 1).
Dorsum.Setae stout, moderate length and with flagellate tips (Fig. 3), sometimes with one or two trilocular pores next to setal bases, each 20-32.5 μm long.Trilocular pores present, each 3-4 μm in diameter, evenly distributed.Oral collar tubular ducts present and without apparent rims, each 8-10 μm long, 3-4 μm wide, in small marginal groups around posterior abdominal segments, usually 1 duct adjacent to some abdominal cerarii, occasionally also present on median areas of abdominal segments.Multilocular disc pores absent.
Venter.Setae flagellate, longer seta each 75-142.5 μm long.Cisanal setae 50-70 μm long, shorter than anal ring seta.Trilocular pores similar to those on dorsum, evenly distributed.Oral collar tubular ducts of two main sizes: the small type, each 6-7 μm long, 2 μm wide, mainly distributed across middle of abdominal segments II-VII, also a few occurring on median areas of thorax and intermixed with marginal ducts; the large type, similar to those on dorsum, present in transverse rows across abdominal segments III-VII, also in marginal groups around head, thorax, and abdomen, but absent from opposite each postocular cerarius (C 4 ).Multilocular disc pores each 8-9 μm in diameter, around vulva, in single or double rows across posterior edges of abdominal segments VII, in single rows across posterior edges of abdominal segments IV-VI, scattered or in single rows across anterior edges of abdominal segments IV-VII or V-VII, sometimes 1-4 pores also on abdominal segment III, a few pores sometimes scattered over median areas of the thorax and head, pores entirely absent from margins of abdominal segments.Host plant.Theaceae: Camellia oleifera.Distribution.China (Jiangxi).Remarks.Planococcus camelliae sp.nov. is similar to P. kraunhiae by having oral collar tubular ducts present on dorsum, but it differs from the latter by the following features (condition of P. kraunhiae given in parenthesis): (i) multilocular disc pores absent from margins of abdominal segments (present on margins); (ii) single dorsal oral collar tubular ducts usually adjacent to some abdominal cerarii (in groups of 2-5 next to some abdominal cerarii); (iii) dorsal oral collar tubular ducts usually similar in size to the large ducts on venter (usually larger than those on venter).The new species also resembles the type of P. citri with oral collar tubular ducts present on dorsum, but it differs from the latter by the following features (condition of P. citri given in parenthesis): (i) multilocular disc pores absent from margins of abdominal segments (present on margins); (ii) dorsal setae stout and with flagellate tips (usually flagellate); (iii) dorsal oral collar tubular ducts usually similar in size to the large ducts on venter (if present, usually larger than those on venter).
The pairwise genetic divergences (by K2P distance) in COI among these six specimens (of five species) are listed in Table 1.The K2P distance is 0.00% within P. camelliae, 10.44-12.21% between P. camelliae and other four Planococcus species list.In mealybugs, the interspecific variation in COI is 11.53% (1.96-19.48%)(Wang et al. 2016), and therefore, our molecular data confirms P. camelliae as a distinct species.
Etymology.The species epithet is derived from the generic name of its host plant, Camellia.
Remarks.Good descriptions and illustrations of the adult female can be found in Tu et al. (1988), Cox (1989), andWilliams (2004).
Remarks.Good descriptions and illustrations of the adult female can be found in Cox (1989), Williams (2004), andPan et al. (2021).

Figure 1 .
Figure 1.Planococcus camelliae Zhang, sp.nov.: A an ant carton that harbours mealybugs inside B mealybugs found inside ant carton with tending ants.

Figure 2 .
Figure 2. Adult female of Planococcus camelliae Zhang, sp.nov.: A Large oral collar tubular duct B trilocular pore C discoidal pore D hind coxa E hind tibia F claw G small oral collar tubular duct H multilocular disc pore I anal lobe cerarius (C 18 ) J anal ring K large dorsal seta L small dorsal seta M cerarius on head.

Figure 3 .
Figure 3. Dorsal setae on Planococcus camelliae Zhang, sp.nov.: A small seta B large seta with trilocular pore next to setal base C large seta without trilocular pore next to setal base.