Holotype female: China, Hebei; 41°09'11"N, 114°03'40"E; 25 August 2022; Miao-Miao Mao leg.; reared from Chromatomyiahorticola on leaves of Lactucasativa and Brassicarapavar.glabra, deposited in IPP. Paratypes: 1♀ 2♂ with same label data as holotype, deposited in National Animal Collection Resource Center, Institute of Zoology, Chinese Academy of Sciences. 1♀ China, Beijing; 39°52'32"N, 116°11'21"E; 11 May 2019; Qiang Wu leg.; reared from C.horticola on leaves of Sonchusoleraceus and Ixerispolycephala, deposited in National Animal Collection Resource Center, Institute of Zoology, Chinese Academy of Sciences. 2♀ China, Beijing; 39°36'18"N, 116°18'57"E; 20 May 2019; Jing He and Meng Guo leg.; reared from C.horticola on leaves of Hemisteptialyrata, deposited in IPP. 1♀ 2♂ China, Shanxi; 39°11'23"N, 113°15'14"E; 6 June 2017; Zhu-Sheng Zheng leg.; reared from C.horticola on leaves of Lepidiumapetalum, deposited in IPP. 1♀ 2♂ China, Shanxi; 36°11'8"N, 113°04'22"E; 17 May 2018; Jing He and Su-Jie Du leg.; reared from C.horticola on leaves of Cirsiumjaponicum, deposited in IPP. 3♀ 5♂ China, Shanxi; 35°29'33"N, 112°54'16"E; 9 May 2019; Jing He and Su-Jie Du leg.; reared from C.horticola on leaves of Crepidiastrumsonchifolium, deposited in IPP. 2♀ 1♂ China, Hebei; 38°16'48"N, 114°41'59"E; 14 May 2017; Rong-Jun Zhen and Gui-Fen Zhang leg.; reared from C.horticola on leaves of an unidentified Asteraceae, deposited in IPP.

Scape white with apical 1/3–1/2 dark brown (Figs 1–5). The yellow markings on the vertex and face, and those on the male are wider than those on the female. Fore wing with complete vertical infuscate bands below base of marginal and stigmal veins respectively, the two bands are interconnected medially (Figs 1–3, 7); speculum bare, without dense setae and postmarginal vein almost equal in length to stigmal vein (Figs 1–3, 7). Mid and hind femora black with apical 1/4 yellowish-white (Figs 1–3). Fore and mid tibia yellowish-white with a dark ring basally (Figs 1–3). Hind tibia black with apical 1/5 yellowish-white (Figs 1–3). Pretarsus on all legs black (Figs 1–3).

Female (Fig. 1). Body length 1.6mm, Fore wing length 0.8mm. Scape white with apical 1/3–1/2 dark brown. Pedicel and flagellum dark brown. Head dark brown. Eyes red and ocelli brown. Mandibles brownish. Yellow markings on the vertex and face. Pronotum, mesoscutum, scutellum, dorsellum, and propodeum metallic blue-green. Fore wing with two complete vertical infuscate bands below base of marginal and stigmal veins respectively, the two bands are interconnected medially (Fig. 7). Mid and hind femora black with apical 1/4 yellowish-white. Fore and mid tibia yellowish-white with a dark ring basally. Hind tibia black with apical 1/5 yellowish-white. Gaster dark brown.

Head (Fig. 1). Head length 0.6× width in dorsal view, and length 0.9× width in frontal view. POL 1.8× OOL. Malar space 0.7× height of eye, and malar sulcus present. Frons and vertex with distinct reticulation. Eyes with sparse and short setae. Toruli situated below the level of lower margin of eyes. Maxillary palpus with two segments and labial palpus with one segment. Antennal flagellum with two funiculars and three clavomeres; scape 4.0× as long as broad and 2.8× as long as pedicel; pedicel 1.3× as long as broad; F1 1.4× and F2 0.9× as long as broad, F1 1.5× as long as F2; clava 2.4× as long as broad, 1.3× as long as scape, and 3.6× as long as F2.

Mesosoma (Fig. 1). Pronotum without transverse carina, reticulate, shorter than mesoscutum. Mesoscutum 1.2× as long as scutellum; mid lobe with two pairs of long setae; notauli incomplete and diverging posteriorly to meet anterior part of axillae. Setae on pronotum and mesoscutum pale. Scutellum as long as broad with straight sublateral grooves and two pairs of setae. Dorsellum with superficial reticulation with isodiametric meshes, posterior margin round. Propodeum shorter than scutellum and without median carina; callus with five setae. Fore wing with 5–7 setae on dorsal surface of submarginal vein; speculum mainly bare, with few scattered setae; costal cell with two rows of setae, including 15 setae at the base of costal cell and an incomplete row with eight setae in apical part; postmarginal vein almost equal in length to stigmal vein; Fore wing length 1.7× fore wing width. Petiole short and inconspicuous. Gaster subrotund, 1.9× as long as wide in dorsal view; apex acute. Tip of ovipositor sheaths visible in dorsal view.

Male (Fig. 2). Similar to the female. Body length 1.4mm, Fore wing length 0.8mm. Head length 0.5× width in dorsal view, and length 0.8× width in frontal view. POL 1.1× OOL. Scape 4.7× as long as broad, 2.2× as long as pedicel. Pedicel 1.6× as long as broad. Antennal flagellum with two funiculars and three clavomeres, F1 0.8× and F2 0.7× as long as broad, F1 1.2× as long as F2. Clava 3.1× as long as broad, 1.1× as long as scape and 4.6× as long as F2. Mesoscutum 1.2× as long as scutellum. Scutellum as long as broad. Fore wing length 1.7× as long as fore wing width. Gaster 1.8× as long as wide in dorsal view.

Females are slightly larger than males (1.6 mm and 1.4 mm, respectively).

Diglyphusdifasciatus is a larval ectoparasitoid, primarily on Chromatomyiahorticola, and occasionally on Liriomyzabryoniae (Kaltenbach), L.sativae, and L.trifolii (Burgess). The hosts are usually mining in leaves of Asteraceae, Brassicaceae and Fabaceae, especially on Ixerispolycephala Cass. ex DC. and Pisumsativum (Table 1). Diglyphusdifasciatus occurs and reaches its highest occurrence period in May, and then disappears in October. Female Diglyphus exhibit three types of host-killing behavior (Zhu et al. 2000; Liu et al. 2013; Hansson and Navone 2017; Ye et al. 2018). The host-killing behavior of D.difasciatus is not known and requires further studies.

China (Beijing, Gansu, Hebei, Inner Mongolia, Ningxia, Qinghai, Shaanxi, Shandong, and Shanxi).

The name is derived from a combination of the Latin di (double) and fascia (band) by referring to the two vertical infuscate bands in the fore wings.

Diglyphusdifasciatus is very similar to D.bimaculatus (Figs 8–10), but has two complete vertical infuscate bands that are interconnected medially in the fore wing, whereas D.bimaculatus has two infuscate spots in the fore wing. In addition, the scape of D.difasciatus is white with apical 1/3–1/2 dark brown (Figs 1–5), which is less than the scape of D.bimaculatus with white upper surface (Fig. 9). Besides, molecular data support the separation of these two morphologically similar species as distinct species.