Description of a new species of Megischus Brullé (Hymenoptera, Stephanidae), with a key to the species from China

Abstract A new species of the genus Megischus Brullé, 1846, Megischus kuafu Ge & Tan, sp. nov., is described and illustrated from Guizhou Province, China. The key to all four species from China is included. A distribution map of the Chinese species is added.


Introduction
The small family Stephanidae Leach, 1815, consisting of 364 extant species, is cosmopolitan but mainly restricted to the subtropical and tropical areas (van Achterberg 2002;Aguiar 2004Aguiar , 2006Aguiar and Jennings 2005;van Achterberg and Quicke 2006;Aguiar et al. 2010;Hong et al. 2010Hong et al. , 2011Tan et al. 2015aTan et al. , b, 2018Chen et al. 2016;Moghaddam et al. 2019;Binoy et al. 2020;Gupta and Gawas 2020). Species of Stephanidae are generally parasitoids of coleopterous larvae, including species of Buprestidae, Cerambycidae, and even Curculionidae, but also hymenopterous larvae of Siricidae (Chao 1964;Taylor 1967;Kirk 1975;Königsmann 1978;van Achterberg 2002;Aguiar 2004). The stephanids which are conspicuous by the five tubercles on the head (thus the name stephanos, Greek for crown), are considered to be rare and nearly 95% of all the species are described from a single specimen (Aguiar 2001;van Achterberg 2002). Among them, Megischus Brullé, 1846 is a large genus of Stephanidae with 87 species worldwide and 30 species from the Oriental region (van Achterberg 2002;van Achterberg and Yang 2004;Hong et al. 2010Hong et al. , 2011Binoy et al. 2020). However, there are only three species known from China up to date (Hong et al. 2010(Hong et al. , 2011. Megischus contains the largest known species of Stephanidae with a body length up to 35 mm, excluding the ovipositor (Hong et al. 2011). Here we report the fourth species of the genus from the Oriental part of China with a body length of 39 mm.

Materials and methods
The holotype was collected by sweep net and directly preserved in 70% alcohol. For identification of the family Stephanidae and genera, van Achterberg (2002) and Hong et al. (2011) were used.
Head. Antenna with 39 flagellomeres; the first flagellomere slender, length 3.4 × its maximum width, and length of second flagellomere 1.2 × its width; frons coarsely and transversely rugose (Fig. 1); three anterior coronal teeth large and lobe-shaped, both posterior ones smaller and wider; vertex transversely rugose anteriorly and reticulate-rugose medially, followed by coarsely and slightly curved rugosities reaching occipital carina; temple slightly bulging, smooth and shiny (Fig. 2), except for some fine punctures laterally; occipital carina strongly developed and connected to hypostomal carina; hypostomal carina large and without distinct rugae, only some punctures (Fig. 3).
Legs. Hind coxa rather strong, annular, largely transversely striate, with long whitish setosity strongly inclined towards (Fig. 9); hind femur robust, with scattered punctures and largely smooth and shiny interspaces (Fig. 10), hind femur ventrally with two large teeth and ten minute teeth in between and one small tooth behind large posterior tooth; hind tibia distinctly curved basally (Fig. 11), elongate and 1.2 × longer than hind femur, densely setose and mostly sparsely punctate, basal narrow part of hind tibia 0.5 × as wide as widest part, lateral view of hind tibia below depression nearly parallel-sided and slender, inner side rather convex basally, densely setose; hind basitarsus slender and parallel-sided, bristly setose ventrally, ventral length 7.4 × its maximum width (Fig. 12).
Metasoma. Tergite I transversely striate-rugose (Fig. 13), ca 6.9 × as long as its maximum width and 10.4 × its apical width, 1.9 × as tergite II and 0.7 × as remainder of metasoma; basal 0.1 of tergite II rugose, remainder smooth and glabrous; remainder of tergites (Fig. 14) shiny and with sparse and short setae (except tergite VII densely  setose medially); pygidial area coriaceous, medially moderately convex and distinctly punctate medially and anteriorly, with long straight setae; length of ovipositor sheath ca 1.5 × as long as body and ca 2.8 × as long as forewing, length of subapical whitish band (Fig. 15) twice as long as dark apical part. Ovipositor tip laterally compressed, with minute teeth apically (Fig. 16). Colour. Mostly black; mesosoma, metasoma, antennae, and hind legs black or blackish; head dark reddish brown; tergite II brownish bilaterally; wing membrane light brownish, hyaline, except most of hind portion of first subdiscal cell and apical part of hind wing brown; veins and pterostigma brown or dark brown; fore and mid- dle legs dark brown (except for coxae black); ovipositor sheath largely black and with whitish subapical band.
Male. Unknown. Etymology. The species name is derived from the name of a giant chasing the sun in Chinese mythology, as an analogy of its exclusively large size and a dark reddishbrown head.
Distribution. China (Guizhou). Biology. Collected in May. Host is unknown. Note. The description is based on the pinned holotype. The colour of the head changed from bright red into dark reddish brown after it died (Fig. 19). The genus Megischus contains the largest known stephanids and some of them can be up to 35 mm (Binoy et al. 2020). Although the size of parasitoids varies among specimens of the same species due to the nutritional conditions of the host and other factors, the body length of 39 mm makes M. kuafu the largest known Megischus specimen, and also the largest Stephanidae.
The large size and general colour pattern more or less resemble M. ducaloides van Achterberg, 2004, but it can be easily distinguished from it by the distinct pronotal fold and the rounded shape of the posterior part of the pronotum. The new species runs to M. ptosimae in the key to Chinese species by Hong et al. (2011) in having the temple slightly convex behind eye, a distinct pronotal fold and cavity below it, and vein 1-M of fore wing ca 5.5 × as long as vein 1-SR. However, the new species differs from M. ptosimae in lacking a pale yellowish malar space, vein 1-M 0.8 × as long as vein m-cu of the fore wing, less sculptured scutellum, posterior half of the hind tibia weakly concave ventrally and the hind basitarsus ca 7.4 × as long as wide. This new species runs to M. rubripes (Kieffer, 1916) in the key to Old World Megischus by van Achterberg (2002), but it differs from M. rubripes in having a more irregular sculpture of the vertex, a large, smooth, and shiny concavity before the pronotal fold, blackish hind tibia and hind basitarsus and tergite I ca 6.9 × as long as its maximum width.