The Encarsia flavoscutellum-group key to world species including two new species from China (Hymenoptera, Aphelinidae)

Abstract Two new species of Encarsia flavoscutellum-group, E. baoshana Li & Geng, sp. n. and E. longchuana Li & Geng, sp. n. are described from China, and photomicrographs are provided to illustrate morphological characters of the new species. A key to all six described species of the E. flavoscutellum-group is given.


Introduction
Encarsia Förster is the largest genus of the family Aphelinidae, and currently contains 441 valid species worldwide, including 103 species from China, of which 45 species are endemic to China including 12 species from Taiwan (Noyes 2017;Li 2013, 2016). Most species of Encarsia with known biology are primary endoparasitoids of Aleyrodidae or Diaspididae (Hemiptera).
The Encarsia flavoscutellum species group was established by Evans et al. (1995) including four species, E. thoracaphis (Ishii, 1938), E. noordami Polaszek, 1995, E. cerataphivora Evans, 1995and E. flavoscutellum Zehntner, 1900 which are known to be specifically parasitoids of Hormaphidinae (Hemiptera, Aphididae). Members of the flavoscutellum-group can be recognized by the following combination of characters: Females: Scutellum always pale. Third valvulae dark in contrast to the second valvifers.
Club 3-segmented. Mandibles with two teeth and a truncation. Mid lobe of mesoscutum with 4-6 pairs of setae. Each side lobe with 3 setae. Axilla large and long, each with a single robust seta centrally, towards the inner margin of the axilla. Scutellum large, as broad as, and more than half as long as, mid lobe of mesoscutum. Scutellar sensilla widely separated. Sculpture on dorsum of mesothorax reticulate and generally robust, scutellum centrally with elongate cells, as in most Encarsia. Tarsal formula 5-5-5. Fore wing uniformly setose. Males: As females except for genital characters and the following: antenna with F2 ventrally bearing a distinctive sensorial complex, F5 partially or completely fused with F6.
Here two new species of this group are described from China. A tentative key to all the known species is provided based on their original descriptions.

Material and methods
Specimens were collected from Yunnan, Henan, Shaanxi and Sichuan Provinces, China by sweeping or using yellow pan traps. Specimens were dissected and mounted dorsally in Canada balsam on slides following the method of Noyes (1982) and morphological terminology following Huang & Polaszek (1998) except metasoma is used for the petiole plus gaster.
Photographs were taken with a digital CCD camera attached to an Olympus BX51 compound microscope, and most measurements were made from slide-mounted specimens using an eye-piece graticule. All the specimens listed below are deposited in Northeast Forestry University, Harbin, China.
The following abbreviations are used: Diagnosis. Female. Length, mesosoma plus metasoma, 0.63-0.71mm. Head with occiput dark brown. Mid lobe of mesoscutum mostly dark brown. Wings hyaline. Legs pale yellow with hind coxae pale brown. Metasoma dark brown except apex of T7 pale yellow. Frontovertex with transverse rugose sculpture. Mandibles weakly dentate, with two weak teeth and a truncation. F1 shorter than F2 and F3 respectively, with 1-2 longitudinal sensilla. Ovipositor 1.07-1.15× as long as mid tibia, and 0.84-0.89× as long as mid tibia and basitarsus combined. Length of second valvifer and third valvula combined 1.28-1.35× as long as hind tibia.
Mid lobe of mesoscutum ( Fig. 4) with 10 setae, each side lobe with 3 setae. Axilla with 1 robust seta centrally, towards the inner margin of the axilla. Mid lobe of mesoscutum, axillae and scutellum with reticulate sculpture. Scutellum 1.65× as wide as long, 0.75× as long as mid lobe of mesoscutum. Distance between placoid sensilla on scutellum 6.67× the maximum width of a sensillum. Distance between anterior pair of scutellar setae 1.10× as long as the distance between posterior pair. Endophragma long and rounded at apex, extending to the middle of T2. Fore wing (Fig. 5) 2.55× as long as wide, uniformly and densely setose except basal area below submarginal vein, marginal fringe 0.21× as long as width of disc, costal cell with 9 setae in a row, basal cell with four setae, submarginal vein with two setae, marginal vein with seven setae along anterior margin and 1.3× as long as submarginal vein. Hind wing (Fig. 6) 6.86× as long as wide, marginal fringe 1.07× as long as width of disc. Tarsal formula 5-5-5 (Fig. 7). Mid tibial spur 0.88× as long as corresponding basitarsus, the latter 0.29× as long as mid tibia. Hind tibia 0.88× as long as mid tibia.
Etymology. The specific name is derived from the collection locality name. Discussion. Encarsia baoshana sp. n. is close to E. thoracaphis (Ishii) in having a relatively longer ovipositor compared with hind tibia, and weakly dentate mandibles, but can be distinguished from the latter by the colour of legs, hyaline wings, mandi-bles, and number of longitudinal sensilla on F1 as listed in foregoing key. Furthermore, the length of second valvifer and third valvula combined 1.28-1.35× as long as hind tibia (vs 1.5×), and anterior margin of marginal vein with 6-8 setae (vs 10-11).
The new species is also closely related to E. longchuana sp. n., and the differences were listed in the key, and also see the discussion under E. longchuana sp. n.. Diagnosis. Female. Length, mesosoma plus metasoma, 0.77mm. Head with occiput above occipital foramen dark brown. Anterior half of mid lobe brown. Wings hyaline. Legs pale yellow. Metasoma dark brown except apex of T7 pale yellow. Mandibles with two weak teeth and a truncation. F1 slightly shorter than F2 and F3 respectively, with three longitudinal sensilla. Ovipositor 0.95× as long as mid tibia and basitarsus combined. Length of second valvifer and third valvula combined 1.4× as long as hind tibia.
Mesosoma 0.77× as long as metasoma (Fig. 17). Mid lobe (Fig. 18) of mesoscutum with 10 setae, each side lobe of mesoscutum with 3 setae. Axilla with 1 robust seta centrally, towards the inner margin of the axilla. Mid lobe of mesoscutum, axillae and scutellum with reticulate sculpture. Scutellum 1.47× as wide as long, and 0.87× as long as mid lobe of mesoscutum. Distance between placoid sensilla on scutellum 6.75× the maximum width of a sensillum. Distance between anterior pair of scutellar setae 1.11× as long as the distance between posterior pair. Endophragma long and rounded at apex, extending to the anterior margin of T2. Fore wing (Fig. 19) 2.44× as long as wide, uniformly and densely setose except basal area below submarginal vein, marginal fringe 0.16× as long as width of disc, costal cell with 12 setae in a row, basal cell with five setae, submarginal vein with two setae, marginal vein with eight setae along ante-rior margin and 1.14× as long as submarginal vein. Hind wing (Fig. 20) 6.3× as long as wide, marginal fringe 0.92× as long as width of disc. Tarsal formula 5-5-5 (Fig. 21). Mid tibial spur as long as corresponding basitarsus, and the latter 0.31× as long as mid tibia. Hind tibia 0.9× as long as mid tibia.
Male. Unknown. Host. Unknown. Etymology. The specific name is derived from the collection locality name. Discussion. Encarsia longchuana sp. n. is closely related to E. baoshana sp. n. in having relatively longer ovipositor compared with hind tibia, similar structure of mandibles, similar coloration of legs and wings, but can be separated from the latter by the coloration of occiput and thorax, setation of hind wing, relative length of hind wing, F1, ovipositor and the third valvula as listed in the key. Furthermore, E. longchuana sp. n. with clypeus and malar sulcus yellowish brown (vs dark brown in E. baoshana sp. n.) and maximum width of outer plate of ovipositor about 1.48× as wide as minimum width (vs 1-1.27× in E. baoshana sp. n.).