Placusa pinearum Gao, Ji, Liu

Gao, Jiangyong, Ji, Baozhong & Liu, Shuwen, 2011, A new species of Placusa Erichson (Coleoptera, Staphylinidae, Aleocharinae) from China, Zootaxa 3094, pp. 43-51 : 44-49

Placusa pinearum Gao, Ji, Liu , sp. nov.

Type material. HOLOTYPE (3): China, Jiangsu province, Jurong, 15 May 2008, coll. B.Z. Ji & J.Y. Gao. PARATYPES: 1Ƥ, China, Anhui province, Quanjiao, 2 May 2011, coll. J.Y. Gao; 23, China, Jiangsu province, Lishui, 12 June 2008, coll. J.Y. Gao; 1Ƥ, China, Jiangsu province, Lishui, 12 June 2008, coll. J.Y. Gao. All type specimens are deposited at the Insect Museum of Nanjing Forestry University in China. Description. Body Average body length 2.2 mm (n=41), bicolor with head, pronotum, abdomen dark black and elytra bronze yellow, antenna and legs light yellow (fig. 1).

Head wider than long (HW= 0.31mm; HL= 0.23mm; HW/HL=1.35; n=41) with an obvious neck (fig.1); e ye large nearly occupying most of the visible lateral region of head, diameter of an ommatidium 7um, ommatidiums with sparse setae; antenna with 11 segments, 1–3 elongate, 4–10 transverse, moniliform, usually less than twice as wide as long, and the last segment somewhat clavate (fig. 14).

Mouthparts Labrum transverse, with 18 setae symmetrically arranged on the two sides of longitudinal midline of labrum (fig. 17); the molar region of the dorsal surface of the mandibles with 6 rows of large teeth-like denticles (fig. 12); two-segmented labial palpi with sparse setae; ligula large broadly rounded and with small sensory pores on its surface (fig. 18); maxillary palpi with 4-segfmented (fig. 13), apical segment with a few sensory pores.

Pronotum wider than long (PW= 0.39mm; PL= 0.26mm; PW/PL=1.5; n=41), slightly concave longitudinally; microsetae directed approximately straight posteriad on both sides of the median line of the disc, and 2–3 rows of microsetae directed obliquely laterad near the base of the disc; and posterior margin of pronotum sinuate (fig. 15).

Elytra wider than long (EW= 0.48mm; EL= 0.35mm; EW/EL=1.37; n=41), and longer than pronotum (EL/ PL=1.35); posterior margin straight; hind wings developed.

Abdomen with clear transverse lines, located between pair of spiracles, on two-thirds of abdominal segments; uniformly covered with dense setae below the transverse line of every tergite, without setae in front of the transverse line of every tergite (fig. 16); and brush-shaped edge on the posterior margin of tergite 7.

Male tergite 8 narrowly produced medially and with two lateral teeth (fig. 10); sternite 8 broad and pointed medially (fig. 11); median lobe of aedeagus with enlarged bulbus, tubus slightly curved, apex truncated in lateral view; flagellum long, and coiled about 2 times (fig. 3, 5); ventral process of crista apicalis narrow and pointed apically (fig. 5); paramere as illustrated with 4 macroseatea on apical lobe (figs. 3, 4, 6).

Female tergite 8 with one broad median projection and two lateral teeth (fig. 8), sternite 8 broadly rounded apically (fig. 9); spermatheca with small and spherical capsule, and twisted in median portion (fig. 7).

Diagnosis. Placusa pinearum may be distinguished by the following combination of characters: male and female tergite 8 with one long median projection and two elongate lateral teeth; flagellum coiled and different in form from the other recorded species; and spermatheca with small and spherical capsule, median portion of spermathecal stem twisted and φ-shaped.

Habitat and distribution. The adults of Placusa pinearum were found living in pine shoot tunnels bored by D. rubella (fig. 2). We noted that the species of pine tree in which Placusa pinearum occurred were usually Pinus taeda Linnaeus , P. massoniana Lamb and P. thunbergii Parl , and Placusa pinearum especially preferred to occur in P. t a e d a and P. massoniana (5 to 8 years old).

In China, there are 9 species of Placusa reported from Heilongjiang, Sichuan, Gansu, Yunnan, Guangdong and Hong Kong, but in our study, Placusa pinearum was found in 8 different locations in Jiangsu, Anhui, Hunan, Yunnan (Appendix 2).

Etymology. The specific name is derived from the unique habitat, where the type species was collected.