Description of three new species of Arescon Walker (Hymenoptera, Mymaridae) from China

Abstract Three new species of Arescon Walker, 1846, Arescon gaoligongensis Jin & Li, sp. n., Arescon sparsiciliatus Jin & Li, sp. n. and Arescon stenopterus Jin & Li, sp. n. are described. A key to the Chinese species is given and photomicrographs are provided to illustrate morphological characters. All the specimens are deposited in the insect collections of Northeast Forestry University, China.

In China, Lin and Xu (2000) keyed Arescon in their key to 19 Chinese genera of Mymaridae and briefly summarized its distribution and hosts. Tian (2009) reported Arescon iridescens (Enock, 1914) from Hainan Province. In this study, we describe 3 new species and provide a key to the Arescon species found in China.

Material and methods
We collected 15 specimens (12 females and 3 males) of Arescon in Yunnan Province and Xizang Autonomous Region (= Tibet) by sweeping, Malaise traps (MT) and yellow pan traps (YPT). Specimens were dissected and mounted in Canada balsam on slides following the method described by Noyes (1982) and modified for Mymaridae by Huber (2015). Photographs were taken with a digital CCD camera attached to an Olympus BX51 compound microscope. Most measurements were made from slidemounted specimens using an eye-piece reticle. Total body length excluding ovipositor was measured with an eye-piece reticle from ethanol-preserved specimens before being dissected. All measurements are given in micrometers (μm). All the specimens listed below are deposited in Northeast Forestry University, Harbin, China (NEFU).
Morphological terminology and abbreviations are adopted from Gibson (1997) and Huber (2012), as follows (with some additions): Fl 2 longer than fl 3 ; fore wing with disc densely setose, with at least 6 irregular rows of setae at broadest part of the wing (Fig. 4)  Fl 2 about as long as or shorter than fl 3 (Fig. 17); fore wing with disc sparsely setose, with at most 3 irregular rows of setae at broadest part of the wing (Fig.  19)  Fore wing relatively narrow, length/width 3.9 (Fig. 4); propodeum relatively short, not more than 0.7× length of scutellum (Fig. 3) 3) with dorsellum rhomboidal; propodeum distinctly shorter than scutellum; phragma broad with posterior margin nearly straight; fore wing ( Fig. 4) 3.93× as long as wide, with venation extending 0.7× length of wing; discal setation rather sparse, with about 7 or 8 rows of setae at the broadest part of wing; base of the wing behind submarginal vein asetose; ovipositor ( Fig. 6) distinctly exserted, 2.12× as long as metatibia.
Description. Female (Holotype). Body length 756. Head yellowish brown with eye, ocelli, middle part of transverse trabecula, supraorbital trabecula and mandible dark brown. Antenna yellowish brown with radicle, scape, pedicel and fl 1 paler. Mesosoma largely yellowish brown except a large round spot on about anterior two fifths and two relatively small spots on lateral margins of mesoscutum, a small spot on each axilla anteriorly, dark brown. Wings slightly infuscated, with venation brown. Legs brown with basal parts of coxae, apical parts of femora and last tarsal segments paler. Metasoma pale brown with exerted part of ovipositor darker.
Head. Head (Fig. 1) width 168. Vertex and face with faint reticulate sculpture. Antenna. Antenna (Fig. 2) sparsely setose. Radicle 0.46× as long as scape; scape about 3.5× as long as wide, with distinct striations which are more or less transverse on base and gradually become oblique distad; pedicel with faint longitudinal striations, about 2× as long as wide, and 2× as long as fl 1 ; all funicular segments much longer than wide, fl 1 distinctly shortest, without mps; fl 2 slightly longer than fl 3 , with 1 mps; fl 3 about as long as fl 4 each with 2 mps; fl 5 slightly shorter than fl 4 , with 2 mps; clava 2.93× as long as wide, longer than scape, shorter than fl 4 and fl 5 combined, divided  Mesosoma. Mesosoma (Fig. 3) length 277. Pronotum entire, with faint longitudinal striations. Mesoscutum with longitudinal reticulate sculpture on mid lobe and isodiametric reticulate sculpture on lateral lobes. Scutellum transverse, distinctly shorter than mesoscutum (30: 51); anterior scutellum (14: 33) subrectangular, with campaniform sensilla a little nearer to lateral margin than to each other. Metanotum with dorsellum rhomboidal. Propodeum smooth, distinctly shorter than scutellum. Phragma broad with posterior margin nearly straight.
Wings. Fore wing (Fig. 4) length 584, width 149, length/width 3.93, with venation extending 0.7× length of wing; longest marginal setae 152, 1.02× as long as greatest wing width. Fore wing base behind submarginal vein without setae, disc behind basal half of marginal vein with 2 or 3 irregular rows of setae, remaining disc distal to middle of marginal vein with 7 or 8 irregular rows of setae and a bare strip present along about distal one third of posterior margin. Hind wing (Fig. 5) length 545, width 17, length/ width 32.4, longest marginal setae 101, about 6× as long as greatest wing width.
Etymology. The specific name is derived from the name of the collection locality of the type species.
Comments. Arescon gaoligongensis sp. n. is similar to A. iridescens, but can be distinguished from it by the key given above. The new species is also similar to A. enocki (Subba Rao & Kaur) in relatively longer fore wing venation and fore wing disc setation, but can be distinguished from it by the relatively shorter clava, 2.9× as long as wide, shorter than fl 4 and fl 5 combined (clava relatively longer, 4.0× as long as wide, much longer than fl 4 and fl 5 combined in A. enocki); broader fore wing, 3.9× as long as wide (much narrower, 4.5× as long as wide in A. enocki); and the ovipositor characters, ovipositor originated from base of gaster, distinctly exserted (ovipositor originated from distal part of gaster, and slightly exserted in A. enocki). Diagnosis. Antenna (Fig. 7) of female with fl 2 distinctly longer than each of fl 3 -fl 5 ; clava 2.2-2.6× as long as wide, slightly shorter than scape; metanotum ( Fig. 8) with dorsellum triangular; propodeum longer than scutellum; phragma broad with posterior margin nearly straight; fore wing ( Fig. 9) 5.05-5.35× as long as wide, with venation extending just about half wing length; fore wing base behind submarginal vein with 2 or 3 rows of setae, with a small oval bare area behind the basal part of submarginal vein along posterior margin, and disc at the broadest part of wing with about 12 or 13 irregular rows of setae; ovipositor (Fig. 11) 1.03-1.19× as long as metatibia, distinctly exserted.

Arescon stenopterus
Description. Female (holotype data in square brackets). Body length 730-980 [780]. Head brown with eye, ocelli, transverse trabecula and part of supraorbital trabecula dark brown. Antenna brown with radicle, scape and pedicel paler. Mesosoma brown with frenum pale yellowish brown. Wings infuscate with base of fore wing brown and largely infuscate behind marginal vein. Legs brown with trochanters and apical parts of femora paler. Metasoma brown with petiole pale yellowish brown and base of gaster and tip of ovipositor pale brown.
Host. Unknown. Etymology. From Greek, stenos meaning narrow and pteron meaning wing. The specific name refers to the relatively narrow fore wing.
Comments. Arescon stenopterus sp. n., is similar to A. dimidiatus (Curtis) in that the fore wing has the venation extending just about half of the wing length and the dorsellum is distinctly triangular, but it can be distinguished from A. dimidiatus by the relatively longer fl 3 , much longer than fl 1 (about as long as or slightly longer than fl 1 in A. dimidiatus); relatively shorter clava, distinctly shorter than fl 4 and fl 5 combined (slightly longer than fl 4 and fl 5 combined in A. dimidiatus); and the dimensions of fore wing length and width, 5.05-5.35× as long as wide (6.5× as long as wide in A. dimidiatus).  Fore wing (Fig. 25) length 600, width 158, length/width 3.8, longest marginal setae 166, 1.05× as long as greatest wing width. Hind wing (Fig. 26) length 550, width 19, length/width 29, longest marginal setae 110, 5.79× as long as greatest wing width.
Comments. Arescon sparsiciliatus sp. n. is similar to A. zenit in that fore wing venation extends almost 3/4 of the wing length and fl 2 -fl 5 are almost subequal in length, but can be distinguished from A. zenit by the relatively more sparsely setose fore wing (more densely setose in A. zenit); relatively wider fore wing, at most 4.1× as long as wide (about 6.7× as long as wide in A. zenit); the longest marginal setae relatively shorter, at most 1.3× greatest wing width (over 2× greatest wing width in A. zenit).