Two new species of Entomobryidae (Collembola) of Taibai Mountain from China

Abstract Taibai Mountain is the highest peak of Qinling Mountain Ridge, a climate and geographical demarcation of the southern and northern China. Collembolan species of family Entomobryidae are reported from this region for the first time in this paper. Two new species, Homidia taibaiensis sp. n. and Sinella triseta sp. n. of Entomobryinae are described. Illustrations and differences with similar species are provided.


Introduction
Entomobryidae is the largest family of Collembola with 1736 species recorded worldwide (Bellinger et al. 1996(Bellinger et al. -2013. Among them, 60 and 64 species belong to the genera Homidia and Sinella, respectively. The two genera are affiliated to Entomobryinae, without scales on body and abundant mac (Chen and Christiansen 1993;Pan et al. 2012). The genus Homidia is characterized by spines present on the inner edge of dentes and "eyebrow" mac on anterior Abd. IV in adults, 8+8 ommatidia, mucro bidentate with subapical tooth larger than apical one, and mostly with a significant colour pattern (Pan et al. 2011). Sinella is characterized by reduced ommatidia number and pigment, bidentate mucro and without apical bulb on Ant. IV (Brook 1882).
Qinling is the east-west axial ridge, forming a natural climate and geographical barrier between the southern and northern China. Taibai Mountain is the highest peak along this ridge, located in Baoji City, Shaanxi Province, with a peak rising up to 3767.2 m. Before our study, there was no Entomobryinae species first reported from Taibai Mountain. Hear, two new species of this group are described.

Materials and methods
Specimens were cleared in lactic acid, mounted under a coverslip in Marc André II solution, and observed using Nikon 80i microscope with phase contrast. Photographs were taken with a Nikon SMZ1000 stereomicroscope mounted with a Nikon DS-Fi1 camera. Illustrations were completed to photographs using Photoshop CS2 (Adobe Inc.). All length data were measured with NIS-Elements Documentation 3.1 software (Nikon). Cephalic dorsal chaetotaxy for the genera Homidia and Sinella were designated following Szeptycki's (1973) and Chen and Christiansen's system (1993), respectively, with labial palp chaetae after Fjellberg (1998), labial chaetae after Gisin (1964), dorsal chaetotaxy of terga after Szeptycki (1979).
Abbreviations: Ant. -antennal segment; Th. -thoracic segment; Abd. -abdominal segment; ms -Specialized microchaeta(e); s -Specialized ordinary chaeta(e); macmacrochaeta(e); mic -microchaeta(e). Colour pattern. Ground colour yellow in alcohol, including ventral side; ommatidium patches dark blue; whole head dark brown; antennae yellow except Ant. IV with slight brown pigment and gradually deeper from base to tip; dorsal side of Th. II to Abd. II with slight brown pigment and gradually lighter, posterior Abd. II with a middle and narrow white band close to Abd. III; Abd. III and Abd. V dark brown except bilaterally; Abd. IV with brown pigment and gradually deeper from anterior to posterior edge; coxae of fore and mid leg with slight brown pigment; ventral tube and furcula also yellow (Figs 1-3).
Ecology. Found in the leaf litter of Brassica campestris L. on farmland, altitude 1165±8 m.
Remarks. This new species is characterized by unique colour pattern, such as ground colour yellow (especially VT and furcula), dark brown head (including ventral side), Abd. II with posterior white band, labial basal chaetae E and L 1 ciliate, m5 as mac on Abd. I and 8 mac present on median posterior Abd. IV.
The new species is closest to Homidia socia Denis, 1929 in chaetotaxy, relative to the ciliate labial base chaetae E and L 1 , m5 on lateral Abd. I as mac, A4-6 and B4-6 as mac on posterior Abd. IV. However, it can be easily discriminated from the latter by colour pattern (without longitudinal stripe in the former, three stripes in the latter) and other characters, such as 3 mac in S sets on dorsal head (4 in the latter), m3 as mac on middle Abd. III (as mic in the latter) and without mac anterior to "eyebrow" on Abd. IV (with 2 mac in the latter). Also, this species is similar to Homidia similis Szeptycki, 1973 in chaetotaxy, detailed differences between them are listed in Table 1.  Etymology. Named using the Latin words "tri+seta" (three mac on each side of posterior Abd. IV).

Remarks.
This new species is characterized by 3 mac on posterior middle Abd. IV, ommatidia absent, labial base chaeta R subequal to M in length, X 2 and X 3 on ventral side of head absent, Abd. I-III with 6, 4, 4 mac, respectively, and clypeus with 7 mac arranged in two lines.
This species is most similar to Sinella yunnanica Zhang & Deharveng, 2011 in colour pattern, without ommatidia, claw, mucro, lateral process of labial palp, manubrial plaque and chaetotaxy of head and Th. II-Abd. III. However, it differ from latter in labial base chaeta R subequal to M (obviously short in the latter), X 2 absent (present in the latter), 3 central mac on Abd. IV (5 in the latter), ventral tube with 5+5 mac on anterior face (about 8 in the latter) and 8-9 smooth chaetae on posterior face (12 in the latter). Also, this new species is similar to Sinella colorata Zhang et al. 2010 and Sinella pauciseta Qu et al. 2010 in 3 mac on posterior median Abd. IV, detailed differences between them are listed in Table 2.