A new Atrococcus species (Hemiptera, Coccomorpha, Pseudococcidae) from China, with a key to Chinese species

Abstract A new mealybug species Atrococcus rushuiensis Zhang, sp. nov., collected under the leaf sheath of Sporobolus fertilis (Poaceae) in Fuzhou City, Jiangxi Province, China, is described and illustrated. A new combination is introduced, transferring Allotrionymus shanxiensis Wu to the genus Atrococcus as A. shanxiensis (Wu), comb. nov. A key is presented for the species of Atrococcus recorded from China.

Based on a study of mealybugs from Russia and neighbouring countries, Danzig and Gavrilov-Zimin (2015) found that there is no difference between Allotrionymus and Atrococcus, and treated Allotrionymus as a junior synonym of Atrococcus. Hence, we follow Danzig and Gavrilov-Zimin (2015) in regarding Allotrionymus as a junior synonym of Atrococcus.
In China, Tang and Li (1988) first recorded Atrococcus from Inner Mongolia and reported three species: A. achilleae (Kiritchenko) (on the root of Bassia scoparia), A. innermongolicus Tang in Tang and Li (on the root of Artemisia apiacea) and A. paludinus (Green) (on Leppula intermedia). Later, Tang (1992) recorded two Allotrionymus species: Al. elongatus Takahashi (on Heteropappus altaicus) and Al. multipori Kawai (on Chloris radiata) from Inner Mongolia; the former was a misidentification of Chorizococcus scorzonerae Tang found by Wu (2000). Meanwhile, Tang (1992) also transferred Spilococcus pacificus (Borchsenius) to Atrococcus and Trionymus plurostiolatus Borchsenius to Allotrionymus. The above-mentioned four species were placed under Atrococcus by Danzig and Gavrilov-Zimin (2015). Subsequently, Wu (1999) described a new species Allotrionymus calamagrostis Wu (under the leaf sheath of Calamagrostis sp.) from Henan; this species was placed in the genus Atrococcus by Danzig and Gavrilov-Zimin (2015). Recently, Wu (2000) provided a study of Atrococcus and its related genera, reporting a new species, Allotrionymus shanxiensis Wu (under the leaf sheath of Melica scabrosa) from Shanxi, which is transferred to Atrococcus as A. shanxiensis comb. nov. following the present generic diagnosis. Wu (2000) also reported a new Chinese record, A. cracens Williams, collected from Inner Mongolia (on Artemisia halodendron?) and Shanxi (on Artemisia sp. and Heteropappus altaicus). Including the new species described here, there are ten Atrococcus species recorded in China: A. achilleae, A. calamagrostis, A. cracens, A. innermongolicus, A. multipori, A. pacificus, A. paludinus, A. plurostiolatus, A. rushuiensis sp. nov., and A. shanxiensis comb. nov. In this study, a new species, A. rushuiensis Zhang, sp. nov., is described from China, and a key to the Chinese Atrococcus species is also provided.

Materials and methods
All mealybug specimens were collected from under the leaf sheaths and transferred into 75% alcohol, then prepared and mounted mainly according to the method of Borchsenius (1950). The terminology for the morphological features used in the description are mainly explained by Williams (1962Williams ( , 2004. Photograph was taken with a Nikon D7500 camera. The descriptions and measurements were made using a light microscope (SOPTOP BH200) fitted with an ocular micrometre, and six slide-mounted specimens were studied for measurements. Measurements are in micrometres (μm) except the lengths and widths of the bodies are given in millimetres (mm); all measurements are given as minimum and maximum. Drawings are presented as is usual for Coccomorpha, with the central drawing showing the outline of the body and the dis-tribution of characters (dorsum on the left side, venter on the right), with the enlarged details (not to scale) showing the structure of important characters around the margin.
All specimens examined are deposited in the College of Forestry, Jiangxi Agricultural University, Jiangxi, China.
Dorsum. Setae short and slender, each 15-25 μm long. Trilocular pores each 3.5 μm in diameter, evenly distributed. Oral rim ducts each 9-10 μm long, 6 μm wide, in more or less single transverse rows on most segments. Oral collar tubular ducts absent or present, if present, each 6-7 μm long, 3 μm wide, having fewer numbers marginally on abdominal segments VI or VII. Multilocular disc pores each 7-8 μm in diameter, forming transverse rows or scattered on medial abdominal segments V-VII (V has 0-7 pores, VI has 1-7 pores, VII has 3-12 pores), occasionally few present on margin of abdominal segments V-VII. Discoidal pores minute, scattered. type of oral collar tubular duct C disc pore D trilocular pore E oral rim duct F hind coxa G claw H small type of oral collar tubular duct I multilocular disc pore. Dorsum (J-P) J anal lobe cerarius K anal ring L multilocular disc pore M oral rim duct N trilocular pore O disc pore P dorsal seta.
Venter. Setae slender, longer than those on dorsum, each 36.3-80 μm long. Trilocular pores similar to those on dorsum, evenly distributed. Oral rim ducts same as those on dorsum, present on margin and submargin areas of thoracic and abdominal segments. Oral collar tubular ducts of two types: a large type, similar to those on dorsum, present in transverse rows across abdominal segments III-VIII or IV-VIII, also in marginal groups on abdominal segments V-VIII or VI-VIII, and a small group (together with multilocular disc pores) present on prothorax in front of anterior spiracles (4-11 ducts and 6-17 pores); a small type, each 5 μm long, 2 μm wide, mainly distributed across middle areas of abdominal segments III-VIII or IV-VIII, a few also present on margin with large ducts. Multilocular disc pores same as those on dorsum, numerous, present posterior to vulva, in transverse rows at posterior edges of abdominal segments IV-VII, in transverse rows at anterior edges of abdominal segments VI-VII, a few occurring on submargin areas of abdominal segments II-IV near oral rim ducts, also forming groups along margin of abdominal segments V-VIII or VI-VIII. Discoidal pores minute, scattered.
Host plant. Poaceae: Sporobolus fertilis. Distribution. China: Jiangxi (Fuzhou). Biology. Living under the leaf sheath of its host plant. Remarks. Atrococcus rushuiensis sp. nov. is very similar to A. luffi (Newstead) in the number of cerarii and multilocular disc pores present on both body sides, but it differs from the latter by the following features (condition of A. luffi given in parenthesis): (i) dorsal margin oral collar tubular ducts absent or few (numerous, with multilocular disc pores in submarginal groups up to segment III); (ii) ventral oral rim ducts absent in median areas of prothorax and mesothorax (present in these areas); (iii) translucent pores duct-like (normal, not duct-like) [The morphology of A. luffi is mainly based on Williams (1962)].
The new species also resembles A. paludinus in possessing fewer than 20 oral rim ducts on each segment, which is different from A. luffi in having about 20 oral rim ducts on each segment, but differs from the latter by the following features (condition of A. paludinus given in parentheses): (i) cerarii numbering one pair only (cerarii numbering 6-7 pairs); (ii) Translucent pores duct-like (normal, not duct-like) [The morphology of A. paludinus is also mainly based on Williams (1962)].
In A. rushuiensis sp. nov., the number of ducts and pores vary among individuals, which belong to intraspecific variation. Some specimens have only a small number of ducts and pores, but in other specimens those ducts and pores are much more numerous.
Key to adult females of Atrococcus known from China