Baryscapus dioryctriae Yang & Song sp. nov. (Hymenoptera: Eulophidae), a gregarious pupal and larval endo-parasitoid of Dioryctria pryeri Ragonot and Dioryctria abietella Denis & Schiffermüller (Lepidoptera: Pyralidae) is described and illustrated. The hosts are serious pests of the cones, seeds, and twigs of Pinus koraiensis Sieb. & Zucc., a predominant forest tree species in the northeastern China. The parasitoid has potential as a biocontrol agent for the pests, as an average parasitism rate of 19.5% has been observed and 87.7 parasitoid adults (range 41–138) emerge from a single host. Detailed photographs of the key characters of the female and male of the new species are provided. Type specimens were deposited in Insect Museum, Chinese Academy of Forestry, Beijing, and the Insect Collection of Jilin Provincial Academy of Forestry, Changchun, Jilin Province, China, as well as China National Insect Collection at Institute of Zoology, Chinese Academy of Sciences, Beijing.
The pyralid species, Dioryctria pryeri Ragonot and Dioryctriaabietella Denis & Schiffermüller (Lepidoptera: Pyralidae), are two serious borer pests of Pinus koraiensis Sieb. & Zucc. in northeastern China, including Jilin, Liaoning, and Heilongjiang provinces. They severely damage cones, seeds, and twigs of the tree species. In 2016, ∼70% of the cones were damaged by the two pests in the Changbaishan Mountains forests, and in past years even no seeds were harvested from some forest farms (Mao et al. 2006, Zang 2007, Song 2016; Figs. 1–4). Because P. koraiensis is dominant in both natural and managed forests, the two pyralids are considered very important pests. Because the pyralid larvae are concealed inside the cones, insecticides are typically ineffective. To promote environmentally friendly management of the pests, biological control was chosen as the first option. Thus, investigations of insect natural enemies were conducted to select effective species as biocontrol agents. A gregarious endo-parasitoid of pupae and larvae was found during the survey. It is described below as a new species of Baryscapus (Chalcidoidea: Eulophidae: Tetrastichinae). We also provide biological observations and a discussion of its biocontrol potential.
Until recently the genus Baryscapus has remained unrecognized. However, LaSalle and Graham (1990) clarified and recognized Baryscapus as a valid genus. The genus Baryscapus was created by Förster (1856) and redefined by LaSalle and Graham as follows (LaSalle and Graham 1990, Graham 1991, LaSalle 1994): Body dark or metallic, without pale or yellow markings; malar sulcus often strongly curved; POL at least twice as long as OOL; submarginal vein of forewing with two or more setae; propodeal spiracle with entire rim exposed; cercal setae subequal in length, often slightly longer than the setae on the last tergite; midlobe of mesoscutum often with more than a single row of adnotaular setae; mesosternum generally convex in front of trochantinal lobe, without a distinct precoxal suture. Male funicle and clava often without whorls of long dark setae, when these whorls present they are relatively short and only reach about half-way along the segment following the one which bears them. By the characters above, the genus Baryscapus could be separated from the close genera Tetrastichus and Aprostocetus easily.
Graham (1991) revised European species of the genus, divided the genus into two species groups, i.e., evonymellae-group and daira-group, and described 22 new species to science as well as published 27 new combinations with a key to those species. LaSalle (1994) revised North American species of the genus and found 43 species with 24 new combinations. Noyes (2016) made valuable catalogue for the species of the genus. LaSalle (1990) found two species associated with spider egg sacs. LaSalle and Graham (1990) made an important correction work and clarified the genus Baryscapus as well as published 12 new species combinations. LaSalle and Schauff (1992) published two new combinations of species in Nearctic. Doganlar described two new species from USA (Doganlar 1992) and three new species from Europe (Doganlar 1993). Surekha and LaSalle (1995) described a new species of Baryscapus from North America. Kostjukov and Gokhman (2001) described a new Baryscapus species from Kazakhstan. Kostjukov and Tuzlikova (2002) described a new species from Moldova. Askew and Shaw (2005) published a new species of Baryscapus in Europe with description of its biology. Gates et al. (2005) published a new species which parasitized a chrysomelid beetle in USA. Askew described two new species in the Europe (Askew 2007, Askew and Blasco-Zumeta, 1997). Viggiani et al (2007) described a new species from Italy. Narendran (2007) described two new Indian species. Yefremova and Yegorenkova (2009) and Yegorenkova and Yefremova (2014) published four new species from United Arab Emirates. Ribes (2013, 2014) described three new species from Spain. Yang et al. (2015) described a new species from China.
The genus is distributed in all continents (Graham 1991). Its hosts are larvae and pupae of many species of various families of Lepidoptera, some Hymenoptera and Coleoptera, occasionally Diptera (Tephritidae), rarely Neuroptera and Hemiptera (Coccoidea) (Graham 1991), as well as spider egg sac (LaSalle 1990). Sometimes it is hyperparasitic in other primary parasitoids (Graham 1991). However, it has been not found that the pyralid Dioryctria spp. are as hosts till now. The new species described in present paper is a first host record for the parasitic group.
Materials and Methods
From 2012 to 2016, surveys were conducted in Jilin and Heilongjiang provinces for natural enemies of Dioryctria pryeri and D. abietella. Cones and twigs of P. koraiensis attacked by the two pyralid pests were collected and searched for larvae and pupae. The pupae and mature larvae were placed individually in vials (75 mm in length and 10–13 mm in diameter) that were tightly sealed with cotton to maintain moisture for rearing in the laboratory. They were reared at 20–25°C and checked daily to collect emerging parasitoid adults. Rates of parasitism and the sex ratio of emerging adults were assessed. The remains of the moth pupae and larvae were later dissected to determine whether or not they contained primary or hyper parasitoids. The parasitoid specimens were preserved in 75% alcohol and later underwent critical-point drying (Gordh and Hall 1979) and mounting on card triangles for taxonomic study. Specimens were examined with a Nikon SMZ1500 stereomicroscope, and the description of the new species is based on both the freshly killed specimens (3 d after emergence) and the critical-point-dried specimens. Photographs of the new species were taken with an Olympus CX31 microscope with the “UV-C Optical Totally Focuses System” developed by Beijing United Vision Technology Co., Ltd. (Beijing, China).
Terminology follows Gibson et al. (1997) and Bouček (1988). The following abbreviations is used: flx = funicle segmentx; clx = claval segmentx; POL = shortest distance between the posterior ocelli; OOL = shortest distance between a posterior ocellus and compound eye. Type materials are deposited both in the Insect Museum, Chinese Academy of Forestry, Beijing, and the Insect Collection of Jilin Provincial Academy of Forestry, as well as the China National Collection in Chinese Academy of Sciences.
This paper and the nomenclatural act(s) it contains have been registered in Zoobank (www.zoobank.org), the official register of the International Commission on Zoological Nomenclature. The LSID (Life Science Identifier) number of the publication is: urn:lsid:zoobank.org:pub:E49EE7EA-1F32-4331-804A-90259A0622D6
Results and Discussion
Baryscapus dioryctriae Yang & Song, n. sp. (Figs. 5–21)
Length 1.8–2.3 mm (holotype 2.2 mm).
In dorsal view, the head is dumbbell-shaped (Figs. 5–13), 2.1 times as broad as long, and about as broad as mesosoma (42:41); temple about 0.3 times as long as eye; POL 2.5 times OOL (Fig. 10); occiput with a longitudinal line and without occipital carina; vertex with relative dense setae and reticulated sculputre; ocellar area with sparse setae and a shallow, but complete, ocellar sulcus. In front view (Fig. 11), head 1.2 times as broad as height; frons 1.3 times as broad as eye height; toruli located at the lower ocular line; scrobal depression deep, extending to anterior margin of median ocellus; parascrobal area bulged with dense setae; eye pilose; malar sulcus distinctly curved and 0.57 times of eye height (Fig. 13); face with reticulate sculpture; lower face slightly convex medially with sparse setae; clypeus produced as two lobes at anterior margin; the distance between the lower margin of torulus and outer margin of clypeus 0.54 times as long as that between the lower margin of torulus and median ocellus. Antennal scape (Figs. 10–13) short, not reaching median ocellus, with length 3.3 times as long as broad, and as long as eye length, with dorsal surface strigose and with dense setae and ventral surface bare and smooth; the combined length of pedicel plus flagellum 0.88 times head breadth and 0.83 times breadth of mesoscutum; pedicel 2.0 times as long as broad; pedicel, funicular and claval segments all with dense long setae; flagellum with one anellus, three funicle segments, and three-segmented clava; each funicle and clava segment with only one row of multiporous plate sensilla; relative measurements (length/breadth) of funicle and claval segments are as follows: segment fl1 26/24, fl2 23/26, fl3 22/28; claval segment cl1 18/32, cl2 21/28, cl3 19/19; apical claval segment with a conspicuous spicula.
Mesosoma (Figs. 5, 7–9, 16)
In dorsal view, mesoscutum convex and 1.2 times as long as broad. Pronotum narrow and descending abruptly forwards to neck, without pronotal carina, with reticulate sculpture and with sparse setae. Mesoscutum 1.7 times as broad as long with fine engraved longitudinal strigose reticulation; notauli wide and deep; breadth of anterior margin of mid-lobe 1.2 times its length and 1.9 times as broad as its posterior margin breadth, and its surface with a shallow but obvious longitudinal median sulcus and about 15 adnotaular setae; side-lobes with raised reticulation and sparse setae; axillae 0.38 times mesoscutum length and with dense raised reticulation. Scutellum convex and 1.3 times as broad as long with two submedian grooves and two lateral grooves; submedian lines of scutellum about equidistant from each other and from sublateral lines, with enclosed space 2.5 times as long as broad; its surface with engraved reticulation which is finer and denser than on mesoscutum; three setae on the posterior half of scutellum next to each submedian groove. Dorsellum crescentic and about 0.18 times as long as scutellum medially, its surface with weakly strigose nearly shiny. Propodeum with breadth anteriorly about 9.0 times its median length, and its length 0.22 times as long as scutellum medially; median carina weak but complete and without plicae, submedian area with engraved reticulation; spiracle oval and large, closed to anterior margin with spiracles 1.0 times their diameter from hind edge of metanotum, and 1.3 times their diameter from posterior margin of propodeum, its rim exposed distinctly (Fig. 5, 8, 9, 16); callus with approximately five setae. In lateral view, metatibia 1.14 times metafemur length and 1.33 times metatarsus.
Wings (Figs. 5, 7, 14, 15)
Forewing 2.13 times as long as broad; ratio of lengths of submarginal, marginal, and stigmal veins 96:102:38; submarginal vein with three or four setae (in most individual with 4); basal cell bare above and basal setal line complete with about four setae; cubital setal line complete but starting close to the lower outer margin of basal cell. Hind wing (Fig.15) 4.1 times as long as broad.
Metasoma (Figs. 5–7, 9)
Metasoma oval acuminate and 1.85 times as long as broad, its length 1.4 times as long as thorax and 1.1 times as long as head plus thorax; its breadth 1.14 times mesonotum breadth and 1.11 times head breadth; all terga with notably raised reticulation and posterior margin of each segment slight convex; terga 1–6 with few setae laterally and hairless medially, syntergum setos; the relative length of terga1–7: 76:88:92:72:44:18; syntergum triangular with length the same as its basal breadth; cercus with four setae all the same length and not longer than the setae on syntergum; ovipositor protruding slightly (Figs. 5–7, 9). Hypopygium 0.56 times the length of gaster.
Body dark green with metallic luster, but face, mesoscutum, and scutellum with bronze tint; scrobes dark yellow-brown; antenna yellow-brown and scape with green tint; all coxae the same color as body, femora brown with blue-green tint, tibiae and tarsi yellow but metatibia with basal 2/3 testaceous, all last segments of tarsi brown; wings (Figs. 12–14) hyaline with veins pale-brown, and the surface microtrichia brown.
Male (Figs. 18–21)
Body 1.3–1.6 mm in length, similar to female. The relative breadth/length of head, mesosoma, and metasoma as 25/12, 25/36, 22/36, respectively. Antenna with scape pale-brown, all other segments pale yellow; scape moderately flattened; the relative length/breadth of scape, pedicel, funicle 1, 2, 3, 4 and clava 1, 2, 3: 20/8, 5/4, 5/5, 6/6, 6/6.5, 5/6.5, 4/6, 6/5.5, 5/4.5; scape dorsally with sparse setae and ventrally side bare, having a dark brown ventral plaque at basal 3/4 length; funicle four-segmented and each with a compact subbasal whorl of yellow setae extending beyond apex of segment and reaching only to the base of next segment’s whorl of setae (Fig. 17); apical claval segment with a conspicuous terminal spine about 1/3 length segment.
In airdried specimens, the female gaster is strongly collapsed and is narrower than in fresh or critical point dried specimens, with its breadth only 0.8 and 0.75 times and its length 3.8 and 1.2 times head and mesosoma, respectively. In critical-point dried specimens, the female gaster breadth is 1.3 and 1.2 times and the gaster length 4.8 and 1.6 times the head and mesonotum, respectively.
The specific epithet is derived from its host genus name “Dioryctria” (Dioryctria pryeri and D. abietella).
The present new species is in many characters close to Baryscapus herhidanus (Erdös, 1954) (Graham, 1991), but could be separated from the latter by the characters below: female of the new species with funicle segment 1 slightly longer than breadth (1.08 times); propodeal spiracles moderately larger; mid lobe of mesoscutum with median line not complete (anterior 1/5 obliterated) and gaster 1.85 times as long as its breadth. The new species is also close to a Chinese species, Baryscapus beijingensis Yang (2015), but it can be distinguished from the latter by the characters below: female of the new species with funicle segments 1–3 each having length greater than breadth (fl1 1.4, fl2 1.3, and fl3 1.2 times); mesoscutum with about 15 adnotaular setae; gaster 2.3 times as long as broad and ovipositor only protruding slightly.
Holotype ♀, managed forest of Pinus koraiensis, Lushuihe Forest Bureau, Jilin Province, 22 June 2015, reared from pupa of Dioryctria pryeri collected in the twigs of the P. koraiensis. Paratypes: 52♀, 38♂, data are the same as holotype; 22♀, 19♂, 28 June 2015, reared from pupa of Dioryctria abietella collected in the twigs of P. koraiensis; 20♀, 10♂, reared from larva of Dioryctria pryeri collected in the twigs of P. koraiensis. All specimens collected by Li-Wen Song, Xing-Peng Li, and Zhong-Qi Yang; The holotype and most paratypes of the new species are deposited in the Insect Museum of the Chinese Academy of Forestry, Beijing, China, with the paratypes 20♀10♂ deposited in Insect Collection of Jilin Provincial Academy of Forestry, Changchun, Jilin Province, China; and 20♀10♂ deposited in China National Insect Collection at Institute of Zoology, Chinese Academy of Sciences, Beijing.
Baryscapus dioryctriae sp. nov. is a gregarious endo-parasitoid of Dioryctria pryeri and D. abietella pupae and mature larvae (Figs. 22, 23), producing 41–138 wasp individuals from a single host, with an average of 87.7(±8.1) and a female:male ratio of 2.6:1. The natural parasitism rate ranged from 12.6%–27.4%, with an average of 19.5%. The first emerging female wasp chewed a hole in the pupal wall to exit the pupa and other emerging wasps in the brood often used the same hole (Fig.22). Baryscapus dioryctriae appears to have the characteristics of a superior biological control agent for suppression of its hosts because of its relatively high parasitism rate, the relatively large number of wasp individuals reared from a single host pupa, and the high female:male sex ratio. Mass rearing technique is easier, as we have successfully reared the new parasitoid on several other pyralid pupae as substitute host, such as Ostrinia nubilalis (Hübner) and Galleria mellonella (L.) (Lepidoptera).
We thank the following three funds for supporting the present survey and study: Forestry Research Special Funds for Public Welfare Projects (201304411) and Chinese Postdoctoral Science Foundation (2014138636), as well as the Sci. & Tech. Development Foundation of Jilin Province (20150204060NY). We specially thank Dr. Juli Gould, Otis Pest Survey, Detection, and Exclusion Laboratory, APHIS, USDA, Otis ANGB, MA, for her kind review of the manuscript and giving valuable comments.