Studies on the genus Psephenothrips Reyes from China (Thysanoptera, Phlaeothripinae), with one new species

Abstract Species from China of the Asian genus Psephenothrips are reviewed, with P. eriobotryaesp. nov. collected from the leaves of Eriobotrya japonica in Sichuan Province. A key to the five species known from China is provided and the COI sequence of the new species is also given.


Introduction
Phlaeothripinae, the larger of the two subfamilies of Phlaeothripidae, is generally accepted as including three groups, Haplothripini, Liothrips-lineage and Phlaeothripslineage, with the last one considered to be complex and polyphyletic (Buckman et al. 2013). Of the other two, reasonably well-defined major groups, Haplothripini has been given a formal tribal name (Minaei and Mound 2008), but the Liothrips-lineage of leaf-feeding species remains confused and difficult to interpret. The major reason is that about half of the genera are monobasic, with many poorly-defined genera and no clear suprageneric classification (Stannard 1957;Mound and Marullo 1996;Buckman et al. 2013;Dang et al. 2014). There is a lack of identification systems worldwide to members of the Liothrips-lineage and, for China, a serious lack of field studies of species and genera of the Liothrips-lineage. Dang et al. (2014) provided a key to 100 genera from southeast Asia and China, including 34 genera associated with Liothrips. More recently, Wang and Lin (2020) published keys to 11 genera and 28 species of Liothrips-lineage from Taiwan. However, there is a lack of information about the Liothrips fauna of mainland China and preparation of suitable identification systems will require a great deal of work studying slide-mounted specimens and establishing host associations through extensive field work.
As part of attempted studies on the Liothrips-lineage from China, the Asian genus Psephenothrips is reviewed here. This is one of the poorly-defined genera associated with Liothrips, with which it shares the following characteristics: antennal segment III with one outer sense cone, segment IV with 1+2 sense cones and prosternal basantra absent. However, species of this genus differ in having the maxillary stylets long and close together in the middle of the head, the fore tarsal tooth absent in both sexes and the male sternite VIII without a pore plate (Okajima 2006;Tyagi and Kumar 2012). Worldwide, there are seven species listed in this genus (ThripsWiki 2021), of which the type species P. strasseni was described from Philippines, P. leptoceras, P. cinnamomi and P. machili from Japan and P. moundi from India (Reyes 1994;Okajima 2006;Tyagi and Kumar 2012). Recently, Wang and Lin (2020) reported four species in this genus from Taiwan, of which P. baiheensis and P. cymbidas were new species. Presumably, these species all feed on green leaves, although P. leptoceras and P. baiheensis were collected from dead branches and wood. The new species P. eriobotryae sp.nov. is described here from Sichuan Province and P. leptoceras from Yunnan Province is newly recorded from the Chinese mainland. A key to five species from China is provided and the COI sequence of the new species is also given.

Methods
The descriptions, photomicrograph images and drawings were produced from slide-mounted specimens using an Olympus BX53 microscope with a drawing tube. The abbreviations used for the pronotal setae are as follows: am -anteromarginal, aa -anteroangular, ml -mid-lateral, epim -epimeral, pa -posteroangular. The unit of measurements is the micrometre. All specimens studied here are deposited in the School of Bioscience and Engineering, Shaanxi University of Technology (SUT), Hanzhong, China, with some specimens in the National Zoological Museum of China (NZMC), Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
Diagnosis. Head as long as broad or longer than broad; postocular setae well developed, shorter or as long as eyes. Antenna eight-segmented, segment III with 0+1 sense cone, IV with 1+2 sense cones. Maxillary stylets long, reaching eyes and close together in the middle of head and maxillary bridge absent. Prothorax usually with five pairs of setae, sometimes am minute; notopleural sutures complete; basantra absent. Mesopresternum boat-shaped or divided into two parts; metathoracic sternopleural sutures present or absent. Fore tarsus without tooth in both sexes. Fore wing parallel-sided, with numerous duplicated cilia. Pelta broadly triangular; abdominal tergites II-VII with two pairs of sigmoid wing-retaining setae; tergite IX with S1 and S2 setae shorter or as long as tube. Male without a pore plate on abdominal sternite VIII.
Comments. The species of Psephenothrips are similar to Liothrips, but they are distinguished by the long maxillary stylets that are close together in the middle of the head and abdominal segment VIII without a pore plate in the male. This genus is also closely related to Eurhynchothrips in body shape as well most characters including those above (Mound 1968). In this study, these two genera could not be separated from each other. However, according to the generic diagnosis (Mound 1968;Dang et al. 2014), Psephenothrips can be distinguished from Eurhynchothrips only by having no stout maxillary bridge and that is the reason this new species, P. eriobotryae sp.nov., is considered to be a species of Psephenothrips. They both are poorly-defined genera in the Liothrips-lineage and the relationship between them is extremely confused and requires further considerable study.
Comments. Described recently from Taiwan, this species was based on three females collected from dead wood. However, as it shares the characteristics of the Liothripslineage, it presumably feeds on green leaves. In this study, no specimen was examined, but antennal segments VI-VIII were described as uniformly dark brown and this distinguishes the species within the genus Psephenothrips.
Comments. As with P. baiheensis, this species was described from Taiwan and was based on six females and three males from Cymbidium. We did not see any specimens of P. cymbidas and the original description "mid tibiae greyish brown and fore wings pale brown" is not strong evidence for distinguishing the species from P. strasseni and other Psephenothrips species. The mesopresternum, divided into two parts that may be narrowly connected, could be an obvious distinguishing characteristic, but its form needs to be verified in further study. Diagnosis. Body uniform brown (Fig. 8); head as long as wide (Figs 1, 8), postocular setae shorter than eyes, very weakly expanded at apex (Fig. 1); maxillary stylets retracted into eyes, little wide apart (Figs 1, 8); pronotal am minute, other four pairs of major setae well-developed, weakly expanded at apex (Fig. 1); mesopresternum boat-shaped with a protrusion (Figs 5, 10); metathoracic sternopleural sutures absent; fore wing subbasal setae S1 about as long as S2, expanded at apex, S3 small, pointed (Fig. 4); female abdominal tergite IX setae S1 and S2 shorter than tube (Figs 2, 15); male abdominal sternite without a pore plate, S2 setae of tergite IX short and stout (Figs 6, 14).
COI sequence. It includes 1492 bp with the GenBank number MW567215.
Etymology. This species name is composed of one Latin word, eriobotryae, based on its host plant.
Comments. This new species can be distinguished from the other members of Psephenothrips by having pronotal am minute. It is similar to P. leptoceras in body shape and colour, but differs in having postocular setae shorter than eyes (Figs 1, 8), sub-basal setae S3 small and pointed at apex (Fig. 4), and posteromarginal setae of tergite IX much shorter than tube (Figs 2, 15). In P. leptoceras, the postocular setae are about as long as eyes (Fig. 16), sub-basal setae S3 are as long as S2 and expanded at apex (Fig. 21), and posteromarginal setae of tergite IX are slightly shorter than tube (Fig. 19).

Psephenothrips leptoceras Okajima Figs 16-25
Psephenothrips leptoceras Okajima, 2006: 554. Comments. Described from Japan on dead branches, this species was recorded from Taiwan on Rhus semialata by Wang and Lin (2020). It is here recorded from the Chinese mainland in Yunnan Province for the first time, based on five females and one male from a mango tree. Although the original description stated this species was collected from dead branches, it could be feeding on green leaves.

Psephenothrips machili (Moulton)
Rhynchothrips machili Moulton, 1928: 313. Comments. Described from Taiwan by Moulton (1928), this species was transferred by Okajima (2006) to the genus Psephenothrips after checking the types and many specimens from Japan. Subsequently, Liothrips machilus Ananthakrishnan and Varadarasan (1978) from India was synonymised with P. machili by Tyagi and Kumar (2012), based on all paratypes and three females. These specimens were all collected from leaves of Machilus sp., but no specimen was examined in the present study. According to the redescription by Okajima (2006), this species is similar to P. eriobotryae sp.nov., but can be distinguished by the well-developed pronotal am setae and sub-basal wing setae S3 developed and expanded at the apex. Moreover, they feed on different plants.