Rhoptrocentrus quercusi Yan

Cao, Liangming, Yang, Zhongqi, Tang, Yanlong & Wang, Xiaoyi, 2015, Notes on three braconid wasps (Hymenoptera: Braconidae, Doryctinae) parasitizing oak long-horned beetle, Massicus raddei (Coleoptera: Cerambycidae), a severe pest of Quercus spp. in China, together with the description of a new species, Zootaxa 4021 (3), pp. 467-474 : 470-471

Rhoptrocentrus quercusi Yan g et Cao sp. nov.

( Figs 8 , 15–26 )

Type material. Holotype, ♀, China, Liaoning Province, Kuandian County, Daxicha Forest, 1.VI.2009, N40°44′ 58″, E125°11′ 35″, 446 m altitude, Yang Zhongqi and Tang Yanlong collected cocoons, 8.VI.2009 emerged. Paratypes, 1♀2♂♂, same data as holotype.

Description. Body length. ♀/♂ = 3.29–3.31/ 2.34–2.37 mm.

Color. Body black; eyes silvery white; scape and pedicel, flagellum 1–3 joints, maxillary palp, labial palp, legs, ridged portion of median metasomal sternum yellow to brownish yellow; apical 1/3 of each femur with dark irregular spot; female ovipositor brown ( Figs 15, 16 ).

Head. Median length as long as its width in dorsal view; vertex with sparse and shallow wrinkles, each wrinkle centrally with concave dot; eyes big, transverse diameter 1.02 × length of temple, temple slightly swollen behind eyes ( Fig. 19 ); face with wide transverse wrinkles; basal clypeus slightly concave, clypeus triangular; width of hypoclypeal depression 0.65 × width of face, malar space 0.83 × height of eye and 0.59 × basal width of maxillary palp ( Fig. 18 ); antenna 24 segments, scape 2.25 × length pedicel, first segment of flagellum slightly longer than the second segment ( Fig. 17 ); antenna about 0.77 × body length, about as long as fore wing; maxillary palp same length as head length, six-segmented ( Fig. 22 ).

Mesosoma. In lateral view, length twice of maximum height ( Fig. 23 ). Depressed sulcus on pronotum wide and shallow, lateral pronotum with irregular sculptures; anterior mesoscutum steep, with dense disordered small sculptures, notauli and their meeting portion depressed, lateral mesonotal lobe snakeskin-sculptured; scutellar sulcus broad and shallow, median with 1 longitudinal ridge; lateral margin of scutellum ridged basally, 2/3 apically of scutellum smooth, slightly swollen; posterior margin of metanotum ridged, with median and bilateral portion sculptured; propodeum half length of mesosoma, with an inversed “Y”-shaped ridge ( Fig. 20 ).

Legs. Fore coxa with a big odontoid process medially, its length about 2/3 width of coxa; trochantellus as long as coxa; fore femur 0.94 × length fore tibia, and twice of its maximum width; basal 1/3 to sub-apex with 10–12 spines; ratio of fore tarsi I–V = 4:2:1.4:0.8:1.7 ( Fig. 24 ); mid tibia with 11–12 spines medially, apex with two tibial spurs, mid femur 0.83 × length of mid tibia, length ratio of mid tarsi I–V = 3:1.7:1.3:0.7:1.8 ( Fig. 25 ); length of hind femur 0.63 × hind tibia ( Fig. 26 ).

Wings. Fore wing 3.86 × as long as its maximum width; pterostigma 5.5 × as long as its width; 1-R1 about 1.59 × length of pterostigma; radial vein arising from basal 1/3 of pterostigma; SR1 about 1.55 × length of 3-SR; radial vein about 0.6 × length of 2-SR, and 0.27 × length of 3-SR; cu-a vein postfurcal and oblique, m-cu vein enters into second submarginal cell; 1-SR+M vein straight; 1-SR vein about 1/2 length of 1-M vein; r-m vein weakly sclerotized; 3-M and CU1a vein not reaching apex of fore wing ( Fig. 15 ).

Metasoma. Elongate-oblong, first tergite and basal 1/3-1/2 second tergite with irregular striations, other tergites smooth; first tergite length as long as its apical width, first spiracle located at 1/4 sub-basally. Length ratio of tergite I–VII as 4:3.5:4:1.7:1.8:2.1:1.7; Ovipositor 1.35 × body length ( Fig. 21 ).

Male. Antenna 16 segments, other characters are similar to female.

Distribution. China (Liaoning).

Etymology. The new species name derived from the generic name of the tree Q. liaotungensis , the host plant of the longhorned beetle.

Diagnosis. The new species is similar to R. piceus Marshall , and it can be distinguished from the latter as follows: 1. Length of ovipositor 2.6 × length of metasoma ( Figs. 15, 16 ) (ovipositor of R. piceus is 2.0 × length of metasoma); 2. Fore wing CU1a arising from middle of 3-CU1 and CU1b combined ( Fig. 15 ) (fore wing of R. piceus withCU1a arising from upper 1/3 of 3-CU1 and CU1b combined); 3. Sulcus present between second and third metasomal tergites ( Fig. 21 ) ( R. piceus without such sulcus, second and third metasomal tergites fused); 4. Basal 1/3 to 1/2 of second metasomal tergite with distinct striations ( Fig. 21 ) ( R. piceus with basal 1/4 having such striations); 5. Propodeum with an inversed “Y”-shaped ridge ( Fig. 20 ) ( R. piceus without such ridge); 6. Coxae yellow, femora yellowish brown, apical 2/3 of hind tibiae and basitarsi slightly dark brown, other segments of tarsi yellowish brown ( Figs. 15, 16 ) ( R. piceus femora dark brown, hind tarsi yellowish brown); 7. Face with distinct transverse striations ( Fig. 18 ) (face of R. piceus with sculptures and tiny depressions); 8. Posterior 1/3 of mesonotum with a longitudinal ridge ( Fig. 20 ) ( R. piceus without such ridge).

Host. This species parasitizes the second instar larva of M. raddei . Seven cocoons which connected each other and beside a host mummy were collected from the longhorned beetle gallery, and then reared in the laboratory. Only four adult wasps (2♀ 2♂, see types) were successfully emerged.

Remarks. Rhoptrocentrus Marshall comprises three known species (Yu et al. 2012), i.e. South Palaearctic R. claeopatrae, Holarctic R. piceus , and Australasian R. yarramanensis ( Belokobylskij & Maeto 2009) . Here R. quercusi sp.n. is the fourth described species of this small genus.

Figures

FIGURES 5 – 8. 5, young larva of M. raddei under the bark; 6, some of mature larvae of M. raddei from one tree; 7, emergencing of Doryctes petiolatus Shestakov; 8, cocoon of Rhoptrocentrus quercusi sp. n..

FIGURES 15 – 21. Rhoptrocentrus quercusi sp. n., ♀. 15, 16, Habitus; 17, right antennae; 18, 19, head; 20, mesosoma; 21, metasoma. 15, 17, 19 – 21, dorsal view; 16, lateral view; 18, frontal view.

FIGURES 22 – 26. Rhoptrocentrus quercusi sp. n., ♀. 22, Head; 23, mesosoma; 24, fore leg; 25, mid leg; 26, hind leg. 22 – 26, lateral view.