A new species of Antennoseius (Vitzthumia) Thor (Acari: Mesostigmata: Ascidae) from China, with a key to species of the genus recorded from China

The subgenus Antennoseius (Vitzthumia) Thor, 1930 is recorded from China for the first time by description of a new species, Antennoseius (Vitzthumia) heterochaetus Long & Yi n. sp. that was collected from leaf litter of subtropical forest in Sichuan Province, China. The new species can be distinguished from other members of the subgenus by podonotal shield with four pairs of spur­like setae (j2–j4, z2), j1 short and barbed distally, setae av1 on trochanters III and IV slightly swollen with fine distal tip. The holotype of Antennoseius ningxiaensisBai &Ma, 2006 was examined and because the leg I avoid pretarsus and claws and also tibia III bear eight setae, the species distinguished as a member of the subgenus Antennoseius (Antennoseius). A key to Chinese species of the genus Antennoseius is given.

The species of Antennoseius have been found in different habitats, occur in soil, salt marshes, rotting plant, litter, moss, carabid beetles, as well as in nests of mouse, birds and ants (Bai & Ma 2006; Beaulieu et al. 2008; Faraji et al.. 2017; Kazemi 2018. In a field survey of soil mites in southwest China, the specimens belonging to the subgenus Vitzthumia were found, representing the first record of the subgenus Vitzthumia from China and a new species to science. This paper aims to describe it as well as clearing the taxonomic status of Antennoseius ningxiaensis Bai & Ma 2006 by examining the holotype.

Materials and methods
Mites were extracted from shed leaves samples using modified Tullgren funnels equipped with 40 Watt bulbs, and preserved in 75% alcohol. Mites were cleared in Nesbitt's solution and then mounted on microscope slides in Hoyer's medium (Krantz & Walter 2009). Line drawings were prepared with the aid of a drawing tube attached to a Nikon Ni E microscope and figures were edited with Adobe Photoshop CC 2018. All measurements were taken with the software (Nikon NIS Elements AR 4.50) and given in micrometres (μm).
Idiosoma lengths were measured along their midlines. Setae were measured from the bases of their insertion to their tips. Legs I-IV were measured from the base of coxa to the distal tip of the tarsus excluding the pretarsus (stalk, claws and pulvillus). The palps were measured from the base of the trochanter to the apex of the tarsus. The idiosomal setal nomenclature follows Lindquist & Evans (1965) with modifications for the posterior region as given by Lindquist (1994). Leg setal notation and palp chaetotaxy are based on Evans (1963a) and Evans (1963b). Distinction between gland pores and poroids (lyrifissures) follows AthiasHenriot (1971AthiasHenriot ( , 1975; notation for porelike structures on the idiosoma mostly follows Kazemi et al.. (2014). Remarks -Antennoseius ningxiaensis was originally described by Bai & Ma (2006) based on one female from Ant Myrmos sp. nest in Ningxia Hui Autonomous Region, China, but the subgeneric status of the species was not clear. Here, we examined the holotype of the species and observed the absence of pretarsus and claws on leg I and tibia III with eight setae. Therefore, we consider it a species belong to the subgenus Antennoseius.

Diagnosis
Dorsal shield with reticulate ornamentation. Podonotal shield with 20 pairs of setae, of which j2-j4, z2 short, strongly thickened and spurlike, j1 short and barbed distally. Opisthonotal shield with 15 pairs of setae, of which J3-J5, Z3-Z5, S2-S5 barbed distally, Z5 about twice as long as others. Anterior margin of sternal shield slightly convex, posterolaterally eroded, with median process, st1, st3, iv3 and st4 in soft cuticle. Setae st5 on epigynal shield. Deutosternum with seven rows of denticles, each with 6-12 denticles, and first to sixth rows connected with lateral margins of deutosternal groove. Seta pc greatly swollen with fine distal tip. Anterior margin of epistome slightly convex and denticulate, dorsal surface of epistome with a transverse row of denticles. Setae av and pv on coxa I and pv on coxa II obviously swollen with fine distal tip. Tibia III with eight setae (pl2 absent).

Etymology
The species name heterochaetus refers to the dorsal shield with several different types of setae.

Differential diagnosis
Antennoseius (Vitzthumia) heterochaetus Long & Yi n. sp. resembles A. perseus Beaulieu, 2008 (smooth morph) in the shape of setae ad1, pd1 on femur I, pd2 on genu I (spinelike) and seta pc (greatly swollen and with fine distal tip), sternal shield (posterolaterally eroded and with median process), seta st3 location (on soft cuticle), dorsal shield smoothly reticulate, number of setae on tibia III (eight setae, pl2 absent) and podonotal shield (20 pairs). The new species can be differentiated from A. perseus by the following characters. In the new species, j2-j4, z2 spurlike, one spinelike setae on genu I, setae av and pv on coxae I greatly swollen with fine distal tip, seta av1 on trochanters III and IV also obviously swollen with fine distal tip, and j1 barbed distally; while in the latter setae j2-j5, z2 spurlike, two spinelike setae on genu I with, setae av or pv on coxae I evidently swollen and with fine distal tip, setae av1 on trochanters III and IV normal, and j1 acicular and smooth. Antennoseius heterochaetus also resembles A. bregetovae Chelebiev, 1984. Both of them have four pairs of spurlike setae of the j and/or z series on podonotal shield, three circumanal setae on anal shield, and smoothly reticulate on dorsal shield. The new species can be differentiated from A. bregetovae by the following characters. The new species has 20 pairs of setae on podonotal shield, of which j2-j4, z2 are spurlike, three spinelike setae on femur I, and setae st3 locate on soft cuticle, sternal shield posterolaterally eroded, with median process; while the latter has 18 pairs (j3-j5, z3 are spurlike), one spinelike seta on femur I, and setae st3 locate on sternal shield, sternal shield normal.

Discussion
Most of species of the genus Antennoseius are associated with carabid beetles. However, there is no relevant research in China. The future research should be focused on different habitats in China.