﻿A taxonomic study of Psyllaephagus Ashmead (Hymenoptera, Encyrtidae) from China

﻿Abstract Fifteen species of Psyllaephagus from China are studied. Three species, P.clavus Zou & Zhang, sp. nov., P.obliquus Zou & Zhang, sp. nov., and P.tangae Zou & Zhang, sp. nov., are described as new to science. A diagnosis or a description/redescription, figures of the characters, as well as the known distribution and hosts of each species are provided. A dichotomous key is also given to facilitate the identification of species.


Introduction
In the family Encyrtidae, Psyllaephagus Ashmead, 1900 is one of the largest genera with approximately 246 recognized species (Noyes 2019).Most species of Psyllaephagus are primary parasitoids of psylloids (Hemiptera: Psylloidea), whilst some are secondary (Noyes and Hanson 1996;Trjapitzin 2012).Among Psyllaephagus, three species from Australia have been successfully used for biological control of psylloids.Psyllaephagus pilosus Noyes, 1988 from Australia was introduced and released in California and European countries to control Ctenarytaina eucalypti Maskell, 1890 (Dahlsten et al. 1998;Hodkinson 1999;Chauzat et al. 2002).Psyllaephagus bliteus Riek, 1962 was introduced and released in California to control Glycaspis brimblecombei Moore, 1964 (Daane et al. 2005).Psyllaephagus yaseeni Noyes, 1990 was introduced into Hawaii and south-east Asia for control of Heteropsylla cubana Crawford, 1914 (Beardsley and Uchida 1990).
The greatest number of species occur in Australia where 100 species of Psyllaephagus have been described, although there may be as many as 1,000 species (Noyes and Hayat 1984).Species of Psyllaephagus in the Costa Rican region were studied by Noyes and Hanson (1996).Girault (1915) and Riek (1962) reported a number of species from Australia.Trjapitzin (1989) revised Psyllaephagus and provided a key to 57 species distributed in Palaearctic region.Twenty species of Psyllaephagus are recorded from India (Singh 1996;Hayat 2003), and 22 species from Africa (Prinsloo 1981).The Chinese fauna have been studied by Tan and Zhao (1999), Xu et al. (2000a, b), Tang et al. (2016), and Wu et al. (2021).Several species names used in a Master's thesis by Li (2010) and a PhD thesis by Zhang (2001) are unavailable because these theses have not been formally published.The present paper is intended as a comprehensive taxonomic study of all known species from China.However, we were not able to examine the specimens of Psyllaephagus belanensis (Hoffer, 1963) mentioned by Ma (2004) and P. belanensis is therefore not included in this study.

Materials and methods
Many of the specimens included the present study were reared from psylloids collected from different regions of China.Twigs and/or leaves with psylloids were collected and brought back to the Key Laboratory of Zoological Systematics and Evolution (Institute of Zoology, Chinese Academy of Sciences, IZCAS) and college of Life Science and Technology, Xinjiang University (ICXU).Twigs and/or leaves with psylloids nymphs were kept in nylon bags (100 mesh) for at least one month to allow parasitoids to emerge.Parasitoids were collected and preserved in ethanol (99%).The remaining specimens were collected by using a sweeping net (see Noyes 1982).Part of the newly collected specimens were card-mounted, and others had been dissected and mounted on slides generally following the method described by Noyes (1982).Observation and measurement of specimens were made with a Nikon SMZ-168 stereomicroscope.Microphotographs were taken with a Canon EOS550D digital camera connected to a Leica DM-2500 microscope, and photographs of card mounted specimens were produced using a Nikon D7000 digital camera coupled to a Nikon SMZ-1500 stereomicroscope.All materials examined are deposited in IZCAS and ICXU.
Morphological terminology and abbreviations follow that of Noyes and Hanson (1996) and Gibson (1997) with some modifications.Absolute measurements were used for body length.Abbreviations used in the text are as follows: HW, maximum head width; HL, minimum head length; FV, the width of the frontovertex; OOL, the minimum distance between the eye margin and the nearest posterior ocellus; POL, the minimum distance between the posterior ocelli; SL, the length of the scape; SW, maximum width of the scape; F1 through F6, 1 st to 6 th funicular segments; MSL, mesoscutum length; MSW, mesoscutum width; MT, mid tibia length; MV, marginal vein length; PMV, postmarginal vein length; STV, stigmal vein length; FVL, the maximum length of fore wing; FVW, the maximum width of fore wing; OL, length of ovipositor; GL, length of third valvula.
Abbreviations of depositories:

Diagnosis.
Female.Body length 0.8-3.0mm usually dark brown with green or blue sheen and with metallic luster; occiput margin often rounded, rarely carinate; mandible with one tooth and a truncation (Fig. 1B), or with two teeth and a truncation (Fig. 2B), rarely with three teeth; funicle 6-segmented; clava often 3-segmented or entire, rarely 2-segmented; fore wing fully developed, often hyaline, rarely with a smoky spot under marginal vein and stigmal vein; marginal vein usually punctiform or slightly longer than wide (Fig. 15C), rarely 2-3× as long as broad; postmarginal vein usually shorter than stigmal vein, occasionally absent, in some species as long as or even longer than stigmal vein; mesopleuron in side view clearly separated from base of metasoma by propodeum; mid tibia spur usually shorter than basal tarsus; hypopygium very rarely reaching apex of metasoma; ovipositor hidden, slightly to strongly exserted.Male essentially similar in appearance except for antennae and genitalia: the funicle varying from whiplike with long setae to flattened with short setae, clava entirely; the genitalia usually developed and exserted.
Comments.The specimens studied here agree well with the original description of P. arenarius, except the length of clava is slightly shorter than F3-F6 combined; in the original description, the clava is approximately as long as F3-F6 combined.
Etymology.The specific name refers to its enlarged clava.Host.Unknown.Distribution.China (Xinjiang).
Comments.Psyllaephagus clavus was erroneously treated as P. nartshukae Trjapitzin, 1986in Tang et al. (2016).A detailed study of the morphological characters shows that it is an undescribed species.Using the keys in Trjapitzin (1989), it runs to P. nartshukae Trjapitzin but can be separated from P. nartshukae by F1-F6 broader than long (in P. nartshukae, F1-F5 longer than broad); clava obviously longer than F3-F6 combined(in P. nartshukae, clava slightly shorter than F4-F6 combined, or as long as F4-F6 combined).
Comments.The specimens studied here agree well with the original description of this species, except the slight variation in dimension of F2.In some specimens here, F2 is slightly shorter than broad (see also Myartseva 1979).We regard this difference falls within variation of a species.
Description.Female.Body length ~ 2.2 mm, metallic green; frontovertex and face with green-violet sheen.Antenna scape and pedicel dark brown, funicular segments brown but F6 yellow; mesoscutum with a coppery sheen; axilla and scutellum with blue sheen; basal 1/2 of tegula yellow, apex dark brown; mesopleuron metallic green mixed with golden sheen; legs yellow, but mid and hind coxae dark brown; basal 1/4 of metasoma with a metallic green sheen, remainder coppery; wings hyaline, venation brown.
Variation.A little variation was found in coloration of the scape: the scape is not always totally dark brown, sometimes the base is yellow (Fig. 5A).
Variation.A little variation was found in coloration of the mid and hind coxae: the mid coxa is not always completely yellow, sometimes the base can be dark brown (Fig. 7C); the hind coxa varies from partly to totally dark brown (Fig. 7D).
Comments.The material above was treated as P. punctatus by Zhang (2001) in his thesis, which was not formally published but later cited by Tang et al. (2016) and Wu et al. (2021).Diagnosis.Female.All coxae dark brown; F1 at least as long as or slightly longer than pedicel; F1-F5 obviously longer than broad, F6 slightly longer than broad or subquadrate (Fig. 12A); OL ~ 1.5× MT.
Variation.In P. longifuniculus, a little variation was found in lengths of F1 and F6: F1 is not always shorter than the pedicel, sometimes it is ~ 1.1× as long as pedicel; F6 is sometimes quadrate (Fig. 12A).
Male.Length 1.6-1.8mm; generally similar to female in body coloration, except the antenna yellow; clava and flagellum have long bristles.
Etymology.The specific name refers to its strongly obliquely truncated clava.
Description.Female.Body length ~ 1.0 mm, with greenish blue sheen; head and face generally dark with blue reflections; axillae with purple sheen; mesoscutum, axillae, and scutellum with bronze sheen; tegula entirely yellow; scape dark brown except apex yellow; basal 1/2 of pedicel dark brown, the remainder yellow; funiculus yellow; all coxae dark brown; hind femur dark brown but yellow at apex (Fig. 17D-F); wings hyaline, venation brown.
Mesoscutum distinctly convex; dorsally with reticulate sculpture similar to that on frontovertex; sculpture of scutellum with large cells in basal half and small cells near apex; marginal vein punctiform, slightly longer than wide; postmarginal vein ~ 1.5× as long as wide; stigmal vein 4.7× as long as wide, STV ~ 3.0× PMV; mid tibia spur ~ 0.6× as long as basitarsus.FWL 31.6;FWW 18.1.
Male.Unknown.Etymology.This species named after Miss Tang who contributed so much to the study of Encyrtidae. Host.Unknown.

Distribution. China (Xinjiang).
Comments.This species had been erroneously treated as P. nikolskajae in Tang et al. (2016).Further study of the morphological characters indicate it is an undescribed species.Using the key of Trjapitzin (1989), the species runs to P. tokgaevi Myartseva but differs as follows: clava nearly as long as F2-F6 combined (in tokgaevi, clava approximately as long as F3-F6 combined); OL ~ 5.6× GL (in tokgaevi, OL ~ 4.5× GL).Psyllaephagus tangae is similar to P. belanensis but can be separated from P. belanensis by F4 smaller than F3 (in P. belanensis, F4 not smaller than F3 according to Trjapitzin 1968); F1 and F2 quadrate (in P. belanensis, F1 and F2 longer than wide); head as wide as thorax (in P. belanensis, head distinctly wider than thorax).

Figure 1 .
Figure 1.Psyllaephagus arenarius ♀ A antenna B mandible C fore wing D mesonotum E fore leg F mid leg G hind leg H ovipositor.

Figure 2 .
Figure 2. Psyllaephagus caillardiae ♀ A antenna B mandible C fore wing D mesonotum E fore leg F mid leg G hind leg H ovipositor.

Figure 4 .
Figure 4. Psyllaephagus colposceniae ♀ A antenna B fore wing C mesonotum D fore leg E mid leg F hind leg G ovipositor.

Figure 5 .
Figure 5. Psyllaephagus densiciliatus ♀ A antenna B fore wing C scutellum D fore leg E mid leg F hind leg G ovipositor.

Figure 6 .
Figure 6.Psyllaephagus elaeagni ♀ A antenna B fore wing C mesonotum D fore leg E mid leg F hind leg G ovipositor.

Figure 13 .
Figure 13.Psyllaephagus longiventris ♀ A antenna B mandible C fore wing D mesonotum E fore leg F mid leg G hind leg H ovipositor.

Figure 14 .
Figure 14.Psyllaephagus obliquus sp.nov.♀ A antenna B fore wing C fore leg D mid leg E hind leg F ovipositor.

Figure 15 .
Figure 15.Psyllaephagus ogazae ♀ A antenna B mandible C fore wing D mesonotum E fore leg F mid leg G hind leg H ovipositor.

Figure 16 .
Figure 16.Psyllaephagus stenopsyllae ♀ A antenna B fore wing C mesonotum D fore leg E mid leg F hind leg G ovipositor.

Figure 17 .
Figure 17.Psyllaephagus tangae sp.nov.♀ A antenna B fore wing C mesonotum D fore leg E mid leg F hind leg G ovipositor.