Cerchysiella mesosae Yang

Yang, Zhong-Qi, Wang, Xiao-Yi, Cao, Liang-Ming, Tang, Yan-Long & Tang, Hua, 2013, Cerchysiella mesosae Yang sp. nov. (Hymenoptera: Encyrtidae), a parasitoid of Mesosa myops (Dalman) (Coleoptera: Cerambycidae) larvae in China, Zootaxa 3619 (2), pp. 154-160 : 156-159

Cerchysiella mesosae Yang sp. nov.

( Figs. 1–13 )

Etymology. The species epithet is derived from the generic name of its host, Mesosa myops .

Type material. Holotype (deposited in the Insect Museum, Chinese Academy of Forestry, Beijing, China): Ƥ, China: Daxicha Forest Farm, Kuandian County, Liaoning Province, emerged VII-23, 2009 from a larva of Mesosa myops (Dalman) ( Coleoptera : Cerambycidae ) collected on VII-10, 2009 by splitting branch of oak tree Quercus liaotungensis , and afterwards reared in lab. Paratypes: 130Ƥ and 50 3 with same data as holotype. Paratypes deposited with holotype except 10Ƥ and 10 3 in the British Museum (Natural History), London.

Diagnosis. Differential features to distinguish C. mesosae from the two other described Chinese species are given in the key to species provided above. However, it appears to be most similar to a Japanese species, C. togashii Tachikawa (1988) , which is also a parasitoid of a species of Mesosa , M. longipennis Bates, but a pupal rather than larval parasitoid. Cerchysiella mesosae can be distinguished from C. togashii by: 1) length 1.1 mm (the latter 1.4 mm); 2) female with funicle much longer (1.25×) than scape and funicular 1 only 0.5× as long as funicular 6 (the latter with funicle as long as scape, and funicular 1 the same length as funicular 6); 3) male antenna with pedicel 1.2× as long as funicular 1 and funicle gradually widened from basal to apical segments, thus funicular 6 about 1.1× as wide as long (the latter with pedicel only 0.75× as long as funicular 1 and funicular segments not widened with funicular 6 only about 0.75× as wide as long).

Description. Female ( Figs. 1–6, 8–13 ). Body length 1.0 – 1.2 mm. Entire body conspicuously depressed ( Fig. 2 ); brown with weak dark-green metallic lustre except head dark-brown with lustre much stronger. Antenna with radicle and pedicel testaceous, other parts brown. Setae on head, antennae and mesosoma brown. Coxae, femora and apical tarsomeres concolorous with body; mid and hind legs with tibiae and proximal four tarsal segments fulvous; hind leg with tibia, tarsus and proximal four segments brownish. Wings hyaline, venation and setae on wing disc brownish-testaceous.

Head ( Figs 2, 4, 5 ) somewhat prognathous, in dorsal view about 1.3× as wide as mesoscutum and about 2.8× as wide as long; vertex moderately convex; POL 3.5× OOL; OOL slightly longer (4:3.5) than OD; eye 1.46× as long as wide, and 0.76× as long as frontovertex; temple short, about 0.36× as long as eye, distance from posterior ocellus to occipital margin about the same as longest diameter of posterior ocellus; occiput moderately curved anteriorly and posteriorly with the margin abruptly curved downwards but not forming an occipital carina. Head subcircular in frontal view ( Fig. 5 ), about 1.18× as wide as high, with face moderately evenly convex; face with superficial raised reticulation as well as sparse setae, the setae on gena more obvious and denser, and with a line of about five setiferous punctures along inner orbit; eye with obvious but sparse pilosity and separated by 1.37× their length, with inner orbits slightly convergent ventrally. Malar sulcus not visible and malar space 0.63× eye length; toruli obviously below level of lower ocular line and with ventral margins fairly close to lower margin of head, separated from each other by 1.53× their own width; scrobes not developed. Clypeus crescentic with anterior margin 0.43× as wide as mouth cavity, and sloped downwards at about 60° angle relative to lower face, its apical margin moderately emarginate, and its basal margin curved and extending upwards to level of 0.5 length of antennal torulus. Antenna ( Fig. 6 ) with scape about 0.8× as long as eye and about 3.0× as long as wide, dilated and particularly in apical half flattened ventrally, with dorsal surface reticulate and setose; combined length of pedicel plus flagellum 0.93× head width; funicle 1.25× as long as scape; flagellum obviously clavate, with first claval segment widest; relative length:width of pedicel, funicular segments 1–6 and claval segments 1–3 as follows: 25:15, 8:16, 9:19; 9:21, 10:22, 11:23, 14:28, 20:31, 19:30, 16:22; clava 1.1× longer than combined length of distal four funicular segments; apex of third claval segment with an area of micropilosity; each segment of flagellum with a single row of multiporous plate sensilla and relative long setae.

Mesosoma ( Figs. 1–3, 8 ) about 1.8× as long as wide; in lateral view moderately depressed; mesoscutum and scutellum planate, almost at the same level but slightly convex medially. Pronotum short and below level of mesoscutum, slopping downwards in front and without pronotal carina; weakly reticulate, collar slightly narrower than and about 0.15× length of mesoscutum, with a line of setae along posterior margin which is arched anteriorly and notch-like medially. Mesoscutum 1.36× as wide as long, and evenly covered with about 24 setae; dorsum superficially and delicately reticulate. Axillae triangular, width 1.8× lateral length, with very fine superficial reticulation and 2 or 3 setae close to outer anterior angle, anteromedial angles close to each other but not touching. Scutellum as long as wide and 0.91× length of mesoscutum; fairly flat, smooth and shiny with about 18 setae, of which two are very long and close to posterior margin medially. Metanotum with dorsellum concealed under marginal rim of scutellum, but lateral panel well developed, its lateral length 0.25× length of scutellum, and with about 5 oblique striations. Propodeum shiny, without reticulation; relatively long, about 0.25× as long as scutellum, with its anteromedian one-third concealed under apex of scutellum and posterior half descending steeply; plicae visible only in anterior half; lateral panel 1.20× as long as metanotum; spiracle large, separated from anterior margin by distance less than its own length; callus with 2 or 3 short setae; hind margin slightly curved forwards and medially rimmed. Fore wing ( Fig. 9 ) 2.3× as long as wide, greatly exceeding apex of metasoma when directed posteriorly ( Figs 1, 3 ); dorsal surface of costal cell with a complete line of setae close to anterior margin, ventral surface with 2 complete lines of setae; basal cell with a line of about 4–6 setae close to submarginal vein and with about 4 setae forming basal setal line; filum spinosum directed towards junction of marginal vein and parastigma, consisting of a line of about 4 setae, and clearly converging with distinctive line of about 10 setae forming proximal margin of linea calva; submarginal vein plus parastigma with 9 bristles; wing disc densely setose beyond filum spinosum and with oblique bare strip basad filum spinosum wide and somewhat convergent anteriorly; submarginal vein including parastigma 6.8× length of marginal vein; marginal vein 0.8× as long as stigmal vein and 1.86× length of postmarginal vein; stigmal vein about 2.3× as long as postmarginal vein and 0.8× as long as combined length of marginal and postmarginal veins; stigma subquadrate with 4 circular sensilla. Hind wing ( Fig. 10 ) 3.9× as long as wide, densely setose. Mesopleuron moderately convex, with delicate, superficial, even reticulation. Legs ( Figs. 2, 3 , 11–13 ) with all coxae and pro- and metafemora superficially reticulate; profemur 1.27× as long as protibia; mesotibia with 4 apical pegs, and with long tibial spur equal in length to basitarsus plus second tarsomere; mesotarsus ventrally with different number of pegs on tarsomeres 1–4: basitarsus with 5 pegs (3 in a longitudinal line and the other 2 transversely arranged close to apical margin), second tarsomere with 2, and third and fourth each with 1 apical peg; metacoxa well developed, cordiform, 1.23× as wide as long with a pair of bristles in dorsoapical half; metafemur and metatibia stout, 2.4× and 5.0× as long as wide, respectively; metatibia 1.5× as long as metatarsus and with 2 apical spurs, the outer one 0.5× as long as the longer inner spur.

Metasoma in dorsal view elongate-elliptical ( Fig. 1 ), about 1.8× as long as wide and 1.22× as long as mesosoma, and as wide as mesoscutum; in lateral view apex of metasoma truncate ( Fig. 2 ); all tergites shiny without reticulation but with 2 or 3 short setae dorsally and more setae laterally, the setae particularly dense behind spiracle; tergite 1 with hind margin curved forwards; cercus located within about basal one-third, with 3 bristles of which one bristle is 0.5× as long as other two; triangular ovipositor sheath slightly exposed and with dense setae; hypopygium ventrally with dense setae, its posterior margin deeply excised medially, in ventral view appearing as a subcircular hollow ( Fig. 3 ).

Male ( Fig. 7 ). Length 0.9–1.1mm. Similar in color and structure to female except for antenna. Antenna with scape testaceous, pedicel and flagellum light brownish-yellow. Scape moderately dilated in apical one-third, about 2.4× as long as wide, and 0.6× as long as eye length with dense setae dorsally; radicle relative long, about 0.42× length of scape. Combined length of pedicel and flagellum 1.12× head width. Pedicel length 1.4× its width and 1.27× length of funicular segment 1; pedicel with setae about as long as those on scape, but each funicular segment with very long setae about 1.5× as long as length of funicular; funicular segments 1–6 of same length, but increasingly gradually widened, with width of funicular 6 about 1.24× funicular 1. Clava 2-segmented, about as long as distal two funicular segments combined; setae on clava obviously shorter than those on funicle.

Distribution. China: Northeastern China, including Jilin, Liaoning and Helongjiang provinces, as well as Inner Mongolia. The species may eventually be found throughout China where its host, M. myops occurs.

Host. Mesosa myops (Dalman) ( Coleoptera : Cerambycidae )

Biological observations. Cerchysiella mesosae is a gregarious koinobiont endoparasitoid of M. myops larvae. The maximum number of adult wasps reared from a single mature host larva was 434 with an average of 366. The parasitized host larva died and from a milky-white colour gradually became testaceous and hardened ( Fig. 14 ) about 15 days before parasitoid adults emerged. All adult wasps from a single host larva emerged within 1.5 hours from only two or three exit holes that were chewed in the host mummy body wall by the first emerged group of female wasps ( Fig. 15 ). The contents and organs of the host larvae were consumed by the parasitoid larvae. A total of 1464 parasitoid adults were reared from four host larvae with a female:male sex ratio of 2.3:1. The parasitism rate from our rearing was 2.67%. In forests, the parasitoid adult emergence time was from the last ten days of July to the last ten days of August. This parasitoid species has potential as a biological control agent for suppression of M. myops because of the high number of parasitoids reared from a single host and relative high female sex ratio.

Figures

FIGURES 1 – 10. Cerchysiella mesosae Yang, sp. nov. 1, Ƥ habitus, dorsal view. 2, Ƥ habitus, lateral view. 3, Ƥ habitus, ventral view. 4, Ƥ head and antennae, dorsal view. 5, Ƥ head, front view; 6, Ƥ antenna. 7, 3 antenna. 8, Ƥ mesosoma, dorsal view. 9, Ƥ fore wing. 10, Ƥ hind wing.

FIGURES 11 – 15. 11 – 13, Cerchysiella mesosae Yang, sp. nov. Ƥ legs, posterior view: 11, fore leg; 12, middle leg; 13, hind leg. 14, mature larva of Mesosa myops parasitized by C. mesosae. 15, newly emerged adult wasps of C. mesosae and host larval mummy.