The Asian longhorned beetle (ALB) Anoplophora glabripennis (Motschulsky) has been accidentally introduced into North America (Haack et al., 1997), and together with citrus longhorned beetle (CLB) A. chinensis (Förster) (including the form malasiaca) (Coleoptera, Cerambycidae) were also unintentionally introduced into Europe from Northeastern Asia (Dauber & Mitter, 2001; Colombo & Limonta, 2001). Both insect pests are considered as serious threats to the urban and natural forests in North America and Europe (Haack et al., 2010). Since 1996, the U.S. government has been pursuing ecological surveys in Asian countries (Smith et al., 2001, 2004, 2007; Williams et al., 2004) and an eradication program against the pest, which has to date established populations in five states, and the beetle has also established in one province in Canada. In conjunction with the eradication program, biological control studies were initiated in order to find, identify, and evaluate parasitoids that could successfully control these longhorned beetles (Hérard et al., 2003, 2004).

In 2013 and 2014, within the native geographical range of both longhorned beetles, explorations for natural enemies were initiated in South Korea where ALB and CLB never did undergo serious outbreaks and were thought to be controlled naturally as proposed by Williams et al. (2004). In 2014, during a field experiment using ALB- and CLB-infested sentinel logs to attract parasitoids, several L1 and L2 CLB larvae were found attacked by braconid larvae that were reared to adult stage. They belonged to genus Spathius. In-depth morphological study consisting of detailed comparisons between Asian Spathius species, led us to the conclusion that the parasitoids were Spathius ibarakius Belokobylskij et Maeto, particularly belonging to the Spathius exarator species group according to Nixon (1943). The species group includes more than twenty species from Korea, China, Japan and Russian Far East (Belokobylskij et al., 2012; Tang et al., 2015).

In the present paper, Spathius ibarakius Belokobylskij et Maeto, reared for the first time from CLB hosts, is provided with diagnostic characters including male and illustrated.

Materials and Methods

The adult parasitoid specimens were preserved in 70% ethanol, before being mounted on glue boards. The specimens were photographed with field emission scanning electron microscope (FE-SEM; SU-70, Hitachi) in the Korea Basic Science Institute (Busan, South Korea). Measurements and illustrations were made with a Leica MZ 12.5 and Nikon SMZ-10A stereomicroscopes. Measurements correspond to the maximal dimensions of sclerites or appendages; lengths for the mesosoma and metasoma were measured in lateral view. Terminology follows van Achterberg (1993) and Belokobylskij and Maeto (2009). Ratios were calculated from 3 females and 3 males (one female used for SEM photography).

These voucher specimens were deposited in the Science Museum of Natural Enemies, Geochang, Korea (SMNE), Korea National Arboretum (KNA) and the Sunchon National University, Suncheon, Korea (SCNU).

Taxonomic accounts

Family Braonidae Nees, 1811 고치벌과

Subfamily Doryctinae Förster, 1862 중국고치벌아과

Genus SpathiusNees, 1819

Spathius ibarakiusBelokobylskij et Maeto, 2009

알락하늘소살이고치벌(신칭)(Figs. 1-6)

Spathius ibarakiusBelokobylskij et Maeto, 2009: 502. (Type locality: Japan, Ibaraki Prefecture)Fig. 2

Materials examined. 1♀. Gwangneung, Pocheon, Gyeonggi, Korea from Anoplophora chinensis (Fӧrster) in Acer tegmentosum Maxim. pupation 4. IX. 2014. emergence 19. IX. 2014. M. Kim (SCNU); 3♀, ditto, pupation 28. IX. 2014, emergence 13. Ⅹ. 2014. M. Kim (SMNE, SCNU, KNA) (one female used for SEM study, deposited in SMNE); 2♂, ditto, pupation 24. IX. 2014, emergence 30. IX. 2014. M. Kim (SCNU, KNA); 1♂, ditto, pupation 11. IX. 2014, emergence 17. IX. 2014. M. Kim (SCNU).

Diagnosis

Female (Figs. 1-4). Length of body 2.5-3.9 mm; length of fore wing 2.2-3.0 mm. Antennae Slender, filiform, 28-34-segmented, about 1.2-1.4 times as long as body (ovipositor excluded). Scape 1.4-1.6 times as long as maximum width. Width of head in dorsal view 1.4-1.6 times its median length, 1.1-1.2 times width of mesoscutum. Vertex finely transversely striate (aciculate). Face mostly striate with fine rugosity between striae, except for a smooth on narrow medial vertical area. Epistomal suture distinct and complete. Fore wing 3.2-3.4 times as long as wide, more or less infuscate, with a longitudinal hyaline band medially. Second tergite densely and almost entirely finely granulate-reticulate; anterior half of third tergite distinctly finely granulate-reticulate, smooth in posterior half.

Male (Fig. 5). Body length 2.1-2.6 mm; fore wing length 1.5-2.0 mm. Antenna filiform, 25-30-segmented, 1.2-1.3 times as long as body. Eye black. Mesosoma sometimes distinctly depressed, its length 1.7-2.0 times maximum width. Length of mesosoma 2.2-2.3 times its height. Petiole (lateral view) weakly curved, its length 2.1-2.5 times maximum width (dorsal view); apical width of tergite 1.3-1.6 times its width at level of spiracles. Median length of second and third tergites combined 1.4-1.5 times basal width of second tergite, 1.1 times their maximum width. Legs partly almost entirely yellow or brownish yellow. Otherwise similar to female.Fig. 3Fig. 4

Distribution. Korea (new record: Central), China (Heilongjian, Jilin, Zhejiang, Fujian, Hunan, Guizhou, Sichuan), Japan (Honshu, Shikoku).

Host and biology.Spathius anoplophorae is an ectoparasitoid of the citrus longhorned beetle, Anoplophora chinensis (Förster) on the Manchurian striped maple, Acer tegmentosum Maxim. Four larvae of A. chinensis in the sentinel logs were parasitized by one or two larvae of S. anoplophorae naturally occurring in the habitat (Fig. 6A, B). Although no larva of A. glabripennis was attacked by S. anoplophorae during summer 2014 in the sentinel logs, additional host specificity testing in the laboratory is necessary before any conclusions is made.

On the other hand, we have classified host lists of the Korean species belong to genus Spathius with Table 1.

Pupae of male (n = 3). Exarate pupa, without spinning a cocoon. Legs, wings and antennae are free from the body and the abdomen is moveable, such that the pupa is capable of limited locomotion. Body milky white, eyes dark brown; length 7.8-7.9 mm (Fig. 6C). Pupal period of male was six days.

Pupae of female (n = 3). Making the cocoon (Fig. 6D). Length 8.2-8.4 mm. Cocoon color dark grayish yellow. Pupal period of female was fifteen days.