Review of Strongylogaster Dahlbom (Hymenoptera: Tenthredinidae) from Zhejiang Province, China, with the description of a new species

Five species of Strongylogaster Dahlbom, 1835 are recorded from Zhejiang Province, China. They are four known species, S. formosana (Rohwer, 1916), S. macula (Klug, 1817), S. takeuchii Naito, 1980 and S. xanthocera (Stephens, 1835), and a new species. Strongylogaster tianmunica sp. nov., collected from Mt. Tianmu in Zhejiang Province, is here described and illustrated. This new species resembles S. nantouensis Naito, 1990, but differs from the latter by the following characters: female body length 10–12 mm, male body length 8–10 mm; tegula brown to dark brown; pronotum largely yellowish-white; trochanters black, apical half of hind femora and of hind tibiae yellowish-white; malar space as long as radius of median ocellus; antennomere 3 as long as antennomere 4; and ovipositor apical sheath with distinct lateral scapes. A key to the five species of Strongylogaster from Zhejiang Province is provided.


INTRODUCTION
Strongylogaster Dahlbom, 1835 is the largest genus in Selandriinae (Taeger et al. 2010), which occurs in the Palaearctic, Nearctic, and Oriental regions (Wei and Nie 1998). Forty-four previously known species have been recorded worldwide (Taeger et al. 2010), of which 17 species have been recorded from China up to now according to the Electronic World Catalog of Symphyta (https://www.sdei.de/ecatsym/ecatsym.php).
The Tianmu mountain is located in Lin'an District of Hangzhou City, Zhejiang Province, being one of the famous mountains in East China. As a result of three field trips conducted in May and June, 2014 and 2019, we collected a total of 107 specimens of Strongylogaster. Five species were identified and one of them is new to science. The results, including diagnoses, a key, and the description of the new species, are reported herein.

MATERIAL AND METHODS
Specimens studied in this work were collected by sweeping in wooded bog and forest fringe zones in the forest ecosystem of the middle subtropical zone in China. Of the new species, 68 specimens were examined. Names of the mentioned host plants follow the Flora Reipublicae Popularis Sinicae (http://www. iplant.cn/frps). Unless otherwise stated, species distribution data at the level of zoogeographic regions is taken from Wei et al. (unpublished data). The specimens were examined with a Motic-SMZ-171 stereomicroscope. Images of adults were taken with a Nikon D700 digital camera and a Leica Z16APO device. The genitalia were examined with a Motic BA410E microscope and photographed with a Motic Moticam Pro 285A. Images were focus-stacked using Helicon Focus (HeliconSoft, Kharkiv, Ukraine) and further processed with Adobe Photoshop CS 11.0. The terminology of genitalia follows Ross (1945) and that of general morphology follows Viitasaari (2002). For a few terms (e.g., middle fovea and lateral fovea), we follow Takeuchi (1952).
The holotype and part of the paratypes are deposited in the Asian Sawfly Museum, Nanchang, China (ASMN). The remaining paratypes are deposited in the Scientific Research and Management Center of East China Pharmaceutical Botanical Garden, Lishui, Zhejiang, China (formerly Lishui Academy of Forestry, LSAF).
Abbreviations. (OOCL) distance between the lateral ocellus and the occipital carina or the hind margin of the head; (OOL) shortest distance between the compound eye and the lateral ocellus; (POL) distance between the margins of the lateral ocelli.

Strongylogaster Dahlbom, 1835
Diagnosis. Body and wings long. Clypeus short, anterior margin slightly emarginated; eyes large and elliptical, distance between eyes usually broader than length of eye; mandibles stubby, with 2-3 symmetrical teeth, apical tooth weakly curved; temple short, lateral sides narrowed in dorsal view, postocellar area broader than long, hind orbit rounded, occipital carina short or absent; frons conspicuous, with a distinct frontal ridge; malar space 0.3-1.3 times diameter of median ocellus; antennae stout, antennomere 2 broader than long, antennomere 3 approximately as long as antennomere 4; epicnemium narrow, distinctly elevated, epicnemial groove distinct; mesepimeron with a distinct transverse middle carina, lower part of anepimeron concave; apex of inner spur of fore tibia bifid, metabasitarsus much shorter than following four tarsomeres together; tarsal claw without basal lobe, inner tooth absent or small and remote from outer tooth; fore wing with vein 1M weakly convergent or parallel with 1m-cu towards pterostigma, base of vein Rs+M distinctly curved, vein cu-a joining cell 1M at about middle, cell 2M clearly longer than broad, anal cross-vein usually absent; hind wing with cells Rs and M closed, anal cell sessile or with a short petiole; ovipositor sheath usually with lateral branches or scapes, narrow and long in few species; lamnium of lancet longer than radix, mostly with regular serrulae; valviceps of penis valve long oval, dorsal margin with minute teeth.
Remarks. Strongylogaster is morphologically similar to Thrinax Konow, 1885, but it can be distinguished by the following characters: epicnemium distinctly elevated, epicnemial groove broad and deep; anepimeron without a membranous area; frontal ridge low and obtuse; occipital carina absent; the anal cell of fore wing usually without a cross-vein; ovipositor sheath usually with lateral branches or scopas. Thrinax can be differentiated by the following features: epicnemium flat, epicnemial groove suture-like or vestigial; anepimeron usually with a distinct membranous area; the frontal ridge distinctly raised, occipital carina well defined on lower hind margins; anal cell of fore wing with a suberect cross-vein, saw sheath always simple and slender towards apex. At present, 44 previously known species have been recorded worldwide. Among them, 17 species occur in China based on Strongylogaster specimens available in our lab (ASMN).  (Rohwer, 1916) Strongylogaster formosana (Rohwer, 1916) Thrinax formosana Rohwer, 1916: 100.

Key to species of
Diagnosis. Female body length 6-7 mm; male body length 5-6 mm. Body black, following parts yellowish-brown: labrum, clypeus, posterior half of pronotum, posterior margins of all abdominal terga, tegula and legs; other parts of all abdominal terga black. Head, pronotum, all abdominal terga, posterior margin of mesepimeron and metapleuron with dense microsculptures, shiny. Malar space broader than diameter of middle ocellus; median fovea large and round, fine carina of lateral foveae high; postocellar area broad, lateral furrow deep and oval rounded; antennae long, approximately 3× length of breadth of head, antennomere 3 shorter than antennomeres 4 and 5. Claw without subapical tooth. Fore wing without anal cross-vein, vein 2r joining inner of vein 3r-m; petiole of anal cell in hind wing slightly shorter than breadth of anal cell. Ovipositor slightly short, scape branch shaped, divergent towards the back; cercus extending into sheath apex. Annuli of serrulae low and flat.
Material examined. Diagnosis. Female body length 5-7 mm. Body black, following parts yellowish-brown: labrum, clypeus, posterior half of pronotum, tegula and legs; median parts of all abdominal terga with yellowish-brown maculae of various shapes, basal and apical parts black. Head, lateral sides of median mesoscutal lobe, pronotum, all abdominal terga, mesepimeron and metapleuron with dense microsculptures, those of head slightly rugose, frontal area and lateral parts with lustre, mesepisternum with small punctures, interspace between punctures slightly smooth. Malar space broader than diameter of middle ocellus; median fovea large and round, fine carina of lateral foveae high; postocellar area broad, lateral furrow deep and oval rounded; antennae long, approximately 3× slightly shorter than breadth of head, antennomere 3 shorter than antennomeres 4 and 5. Claw without subapical tooth. Fore wing without anal cross-vein, vein 2r joining inner of vein 3r-m; petiole of anal cell in hind wing slightly shorter than breadth of anal cell. Ovipositor slightly short, scape branch shaped, divergent towards the back; cercus extending into sheath apex. Annuli of serrulae low and flat. Distribution. China (Anhui, Chongqing, Gansu, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangxi, Shaanxi, Zhejiang), Europe, Japan, North America.
Host plant. Athyrium filix-femina (L.) Roth (Athyriaceae), Pteridium aquilinum (L.) Kuhn (Pteridaceae) (Liston 1995). Naito, 1980 Strongylogaster takeuchii Naito, 1980: 392. Diagnosis. Female body length 6 mm. Body black, following parts white: labrum, clypeus, posterior margin of pronotum, tegula, median parts, posterior margins and lateral sides of abdominal terga; legs yellowish-brown, basal half of all coxae, dorsal sides of middle tarsomeres, dorsal sides of hind tibiae and hind tarsomeres blackish-brown. Dorsal side of head with dense microsculptures, frontal area smooth; thorax smooth, pronotum, posterior parts of mesopleuron and metapleuron with fine microsculptures, posterior margin of mesoscutellum with some punctures; all abdominal terga with dense microsculptures. Median fovea triangular, lateral foveae as broad as median fovea, oval rounded, dorsal margin with fine carina; frontal ridge acute, frontal area five-pointed; lateral furrow of postocellar area deep and oval; malar space as long as diameter of middle ocellus; antennae 3× length of breadth of head, antennomere 3 clearly shorter than antennomere 4. Claw without subapical tooth. Petiole of anal cell of hind wing as long as breadth of anal cell. Ovipositor sheath in dorsal view as long as cercus, scape branch shaped, slightly parallel. Annuli of serrulae slightly prominent.
Strongylogaster tianmunica sp. nov. Diagnosis. This new species resembles S. nantouensis Naito, 1990, but differs from the latter by the following characters: female body length 10-12 mm, male body length 8-10 mm; tegula brown to dark brown; pronotum largely-yellowish white; trochanters black, apical half of hind femur and of hind tibia yellowish-white; malar space as long as radius of median ocellus; antennomere 3 as long as antennomere 4; and ovipositor apical sheath with distinct lateral scapes.
Color. Body black; palp mostly blackish-brown; broad band on posterior margin and lateral corners of pronotum, yellowish-white; tegula, median blotch of abdominal tergum 1, narrow but distinct posterior margins of abdominal terga 1-8, narrow posterior margins of sternites 1-6, indistinct median carina and posterior margin of abdominal tergum 10, pale brown; apical margins of fore and middle coxae, apical 2/5 of hind coxa, about apical half of each femur and basal half of all tibiae, yellowish-white; apical half of fore tibia and tarsomeres, apical half of middle tibia, almost entire middle tarsomeres and base of metabasitarsus, brown; apical half of hind tibia and hind tarsus except base blackish-brown to black. Wings hyaline, apical third barely infuscate, basal 1/2 of vein C in fore wing and entire vein C in hind wing pale brown, other veins and stigma blackish-brown. Body hairs silver, hairs on sheath and antennae blackish-brown.
Wings (Fig. 1). Fore wing with R+M short, M straight, almost parallel to 1m-Cu, anal cell without anal cross-vein, cu-a joining cell 1M at middle, vein 2r joining cell 2Rs at apical 1/4, cell 2Rs longer than cell 1Rs; hind wing with cell Rs slightly shorter than cell M, anal cell sessile.
Legs. Apical spurs of hind tibia subequal in length, slightly longer than apical breadth of hind tibia, hind basitarsomere Strongylogaster from Zhejiang, China, and a new species much shorter than following 4 tarsomeres together (13: 16); claw with a minute inner tooth (Fig. 8).
Ovipositor sheath. Ovipositor sheath in lateral view as shown in Fig. 9 and in dorsal view as shown in Fig. 10, lateral scapes small but distinct, divergent backwards in dorsal view; lancet as shown in Fig. 13, distinctly tapering towards apex, apical half of lancet as in Fig. 14. Male. Body length 8-10 mm (Fig. 2); color and structure similar to female except as follows: narrow posterior margin of abdominal terga 3-4 yellowish-brown; narrow posterior margin of terga 5-8 whitish; narrow apex of each coxa white; apical half of fore femur, apical third of middle femur and apical fifth of hind femur, fore and middle tibiae entirely and base of hind tibia, yellowish-brown; fore and middle tarsi pale brown at basal part and dark brown towards apex; hind tibia except for base and hind tarsus blackish-brown; head, in dorsal view, more strongly narrowed (Fig. 5); antennomere 3 broader and shorter than antennomere 4 (40: 46), length ratio of antennomeres 5-9 as 44: 38: 35: 32: 25 (Fig. 12); subgenital plate slightly longer than broad, apical margin subtruncate (Fig. 7); gonoforceps as shown in Fig. 15, harpe clearly longer than broad; penis valve as shown in Fig. 16, dorsal margin of valviceps with many minute teeth.
Host plants. Unknown. Distribution. China (Zhejiang). Etymology. The specific epithet "tianmunica" is derived from Mt. Tianmu in Zhejiang Province, where the type specimens were collected.
Material examined.

DISCUSSION
Five species of Strongylogaster, including the new species, are recorded from Zhejiang Province. Habitat photographs of the collecting sites of these five species are provided (Figs 17-18). According to data we have already obtained, there are more than 500 species of sawflies in Zhejiang. Mount Tianmu is the area with the highest diversity of sawflies. In Mt. Tianmu, Chanyuan Temple is apparently the most suitable habitat for collecting sawflies, with an altitude of about 400-500 m above sea level.

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Mount Tianmu is the highest mountain in northern Zhejiang Province, where the highest peak is Xianrending (1,506 m above sea level). The subtropical deciduous-evergreen broad leaf forest vegetation of the mountain is well developed and has a very high biodiversity. A great number of new sawflies were found there in the past decades (for example, Shinohara and Wei 2016). Besides Mt. Tianmu, there are a lot of well forested mountainous regions in Zhejiang Province, especially the western and southern regions neighboring Jiangxi and Fujian mountainous areas. There are many gaps in field collecting in those regions till present. We guess that more species of Strongylogaster will be discovered from Zhejiang in future.