Chinese species of the genus Aptesis Förster (Hymenoptera, Ichneumonidae) parasitizing sawflies, with descriptions of three new species and a key to species

Abstract Six species of the genus Aptesis Förster 1850 belonging to the tribe Hemigastrini of the subfamily Cryptinae (Hymenoptera, Ichneumonidae) are reported from China. Three of them, Aptesis elongata Li & Sheng, sp. n., Aptesis melana Li & Sheng, sp. n. and Aptesis nigricoxa Li & Sheng, sp. n. reared from sawflies in China, are new to science. The biology of Aptesis melana is described. A key to the species of Aptesis known from China is provided.


Introduction
Aptesis Förster 1850, belonging to the subfamily Cryptinae of Ichneumonidae (Hymenoptera), comprises 70 described species, of which five are known from the Oriental region, 16 from the Nearctic, one from the Afrotropical, eight from the Eastern Palaearctic and 42 from the Western Palaearctic (two of them are found across the Palaearctic) (Yu et al. 2012).
The cocoons were stored individually in glass tubes (100 mm long and 15 mm in diameter) with a piece of filter paper dipped in distilled water in order to prevent desiccation and plugged with absorbent cotton. Cocoons of Neodiprion huizeensis Xiao & Zhou (Hymenoptera, Diprionidae) were maintained at 23 ± 1 °C with 60 % to 70 % relative humidity and 14 hours to 10 hours light and dark photoperiod. Cocoons of other sawflies were maintained at room temperature. All cocoons were checked daily for sawflies and parasitoid emergence. Emerged parasitoid larvae and pupae were kept in glass tubes at the same temperature until adult emergence. After emergence of sawflies and parasitoids was complete, all remaining cocoons were dissected and their condition (i.e. status of sawflies, and parasitism) was recorded.
Aptesis pallidinervis (Cameron, 1904) was described from India, and there are no host records (Cameron 1904). We were not able to examine specimens of A. pallidinervis and we have compared it to our new species based on the original description.
Images of whole insects were taken using a CANON Power Shot A650 IS. Other images were taken using a Cool SNAP 3CCD attached to a Zeiss Discovery V8 Stereomicroscope and captured with QCapture Pro version 5.1. Morphological terminology is based on Gauld (1991). Wing vein nomenclature and terminology based on Mason (1986Mason ( , 1990. Type specimens are deposited in the Insect Museum, General Station of Forest Pest Management (GSFPM), State Forestry Administration, P. R. China.

Terminology
Postocellar line: the shortest distance between the lateral ocelli. Ocular-ocellar line: the shortest distance between the lateral ocellus and the margin of the compound eye. Wing veins referred to in the text are shown on Fig. 9. Diagnosis. Clypeus weakly to rather strongly convex in lateral review, apex truncate or broadly and gently convex, sometimes faintly concave and sometimes with a median tooth. Mandible of moderate length, its lower tooth the same size as upper tooth or sometimes slightly smaller, rarely slightly larger. Tyloids linear to elliptic or subcircular, on about 5 segments, beginning on flagellomeres 9, 10, or 11. Epomia absent or rudimentary. Mesoscutum rather weakly convex. Notaulus vestigial or reaching as much as 0.3 of distance to scutellum. Sternaulus distinct over more than 0.5 of mesopleuron, its end pointing to lower hind corner of mesopleuron. Juxtacoxal carina complete and strong. Propodeum of moderate length to short, with or without weak apophyses. Costula usually present in males, usually incomplete or absent in females, but sometimes absent in males and sometimes complete and strong in females. Propodeal spiracle circular or short elliptic. Areolet pentagonal, moderate size. Median dorsal carinae of first tergum usually weak and reaching about to the spiracle, rarely longer and stronger. Dorsolateral part of postpetiole usually carinate between spiracle and apex, or rarely rounded. Ovipositor sheath about 0.35 times as long as fore wing. Ovipositor straight, tip usually elongate sagittate but sometimes shorter, teeth on lower valve weak, oblique, separated into a basal and an apical series (Townes 1970). Diagnosis. Clypeus about 1.6 times as wide as long. Malar space approximately 1.3 times as long as basal width of mandible. Postocellar line approximately 1.6 times as long as ocular-ocellar line. Antenna with 21 to 23 flagellomeres. Vein 2-Cu approximately 2.3 times as long as 2cu-a. Hind wing vein 1-cu about 4.0 times as long as cu-a. First tergum about 1.5 times as long as apical width. Ovipositor sheath about 0.7 times as long as hind tibia.

Key to species of Aptesis known in China
Description. Female (Fig. 1). Body length 5.0 to 7.0 mm. Fore wing length 4.0 to 6.0 mm.
Head. Face (Fig. 2) about 1.7 times as wide as long, with fine leathery granulose texture and evenly dense punctures; centrally convex; upper margin concave, with a small median protuberance. Clypeus evenly convex, about 1.6 times as wide as long; basally with texture as face, with weak transverse wrinkles; subapex smooth; apical margin flat. Mandible with dense punctures, upper tooth slightly longer than lower tooth. Malar space with fine granulose texture, approximately 1.3 times as long as basal width of mandible. Gena (Fig. 3) smooth with dense fine punctures; median portion weak convex. Ocellar triangle medially with dense fine punctures; remainder of vertex with fine granulose texture (Fig. 4). Postocellar line approximately 1.6 times as long as ocular-ocellar line. Upper portion of frons flat with fine granulose texture; lower portion concave with fine leathery texture. Antenna with 21 to 23 flagellomeres, ratio of length from first to fifth flagellomeres: 7.0:8.0:6.5:5.5:5.0. Occipital carina complete.
Mesosoma. Pronotum anteriorly with fine wrinkles and dense punctures; medially with fine oblique wrinkles and fine punctures; upper posterior portion smooth, with fine granulose texture and dense fine punctures. Mesoscutum (Fig. 5) weakly convex, smooth with evenly dense punctures. Notaulus evident approximately on anterior half of mesoscutum. Scutellum evenly convex, smooth with dense fine punctures. Postscutellum transverse, with texture as scutellum. Median portion of mesopleuron ( Fig. 6) weakly convex, smooth with evenly fine punctures; lower portion flat, with irregular fine wrinkles and dense fine punctures. Epicnemial carina distinct, approximately reaching subalar ridge; lower portion of subalar ridge weakly concave, with fine transverse wrinkles. Sternaulus distinct, reaching margin of mesopleuron, apically ventral to ventral-posterior corner of mesopleuron. Speculum big, smooth and shiny. Scrobe with strong groove. Metapleuron weakly convex; upper portion smooth with densely fine punctures, lower portion with irregular wrinkles. Juxtacoxal area with fine granulose texture. Juxtacoxal carina and submetapleural carina complete. Legs robust. Ratio of length of hind tarsomeres 1:2:3:4:5 is 19.0:9.0:6.5:4.0:7.0. Fore wing ( Fig. 9) with vein 1cu-a opposite or slightly proximal or distal to 1/M. Vein 3rs-m anteriorly convergent with 2rs-m. Vein 2m-cu meets areolet at about mid-point of cell. Vein 2-Cu approximately 2.3 times as long as 2cu-a. Hind wing vein 1-cu about 4.0 times as long as cu-a. Propodeum (Fig. 7) weakly convex. Area basalis an inverse trapezium, small. Area superomedia elongate, approximately 1.3 times as long as wide, with distinct transverse wrinkles, central portion weakly concave. Costula connecting area superomedia at its middle. Posterior transverse carina of propodeum strong. Area petiolaris weakly sloping, with irregular transverse wrinkles. Area externa with fine granulose texture. Area dentipara with irregular oblique wrinkles. Propodeal spiracle circular, moderately large, near pleural carina, located at anterior 0.2 of propodeum.
Metasoma. First tergum about 1.5 times as long as apical width, with fine leathery texture, smooth. Median dorsal carinae distinct, extending beyond spiracle. Dorsolateral and ventrolateral carinae complete. Spiracle circular, very small, located at apical 0.3 times of first tergum. Second tergum (Fig. 8) approximately 0.7 times as long as apical width, with fine granulose texture; centrally with weak wrinkles. Thyridia present. Third tergum about 0.6 times as long as basal width, with texture as first tergum; basally polished. Fourth to eighth terga with texture as third tergum. Ovipositor sheath about 0.7 times as long as hind tibia. Ovipositor straight and slender, apical portion sharp, with nodus. Apical portion of lower valve with weak ridges.
Remarks. This new species is similar to Aptesis corniculata Sheng 2003, but can be distinguished from the latter by the following combination of characters: face approximately 1.7 times as wide as long; fore wing vein 2-Cu approximately 2.3 times as long as 2cu-a; hind wing vein 1-cu about 4.0 times as long as cu-a; first tergum about 1.5 times as long as apical width. Aptesis corniculata: face approximately 2.0 times as wide as long; fore wing vein 2-Cu approximately 1.5 times as long as 2cu-a; hind wing vein 1-cu about 1.5 times as long as cu-a; first tergum about 1.2 times as long as apical width. Description. Female (Fig. 10). Body length 6.0 to 9.0 mm. Fore wing length 5.0 to 7.0 mm.
Metasoma (Fig. 17). First tergum about 1.3 times as long as apical width, apically with weak wrinkles. Median dorsal carinae distinct, basally parallel. Dorsolateral and ventrolateral carinae complete. Spiracle circular, small, located at apical 0.3 of first tergum. Second tergum approximately 0.5 times as long as apical width, smooth. Third to eighth terga with texture as second tergum. Ovipositor sheath about 0.8 times as long as hind tibia. Ovipositor strong, straight, apically sharp. Apical portion of lower valve with 2 ridges.

Host plants. Pinus armandi, Larix principis-rupprechtii (Pinaceae).
Biology. The mature larva of A. melana forms a cocoon outside the body of the N. huizeensis larva and inside the cocoon of the host. The mature larva of A. melana is cream-colored (Fig. 19). The pupa changes continuously as development continues. The young pupa is cream-colored, the compound eyes light red. After three days, the compound eyes change to dark red (Fig. 20). Two days later, the head and mesosoma are blackish brown (Fig. 21). After two days, the head and mesosoma change to black; the first and second terga blackish brown, third to eighth terga brown (Fig. 22); the basal portion of flagellomeres brown, median portion yellowish white and apical portion yellowish brown. The mature pupa is the same color as the adult. Of 537 A. melana reared from N. huizeensis, the female to male ratio was 1.7: 1. The average parasitism rate of N. huizeensis by A. melana was 8.7%. Adults of A. melana emerged between 17th February to 12th March under laboratory conditions.
Remarks. This new species is similar to Aptesis albibasalis (Uchida, 1930) but can be distinguished from the latter by the following combination of characters: malar space about 1.4 times as long as basal width of mandible; postocellar line about 1.4 times as long as ocular-ocellar line; first tergum about 1.3 times as long as apical width; Diagnosis. Clypeus about 1.9 to 2.0 times as wide as long. Malar space approximately 1.2 to 1.4 times as long as basal width of mandible. Postocellar line approximately 1.5 times as long as ocular-ocellar line. Antenna with 30 to 31 flagellomeres. Fore wing vein 3rs-m almost parallel with 2rs-m. Vein 2-Cu approximately 1.5 times as long as 2cu-a. First tergum about 1.5 times as long as apical width. Ovipositor sheath about 0.7 times as long as hind tibia.
Head. Face (Fig. 24) about 2.0 to 2.1 times as wide as long, with short brown setae and dense punctures; centrally weakly convex, punctures sparser than remainder of face; face orbits granulose with sparse punctures. Epistomal suture distinct. Clypeus about 1.9 to 2.0 times as wide as long, with sparse punctures; basally evenly convex; apically flat, with transverse wrinkles, apical margin distinct. Mandible strong, with dense fine punctures; upper tooth slightly longer than lower tooth. Malar space with fine granulose texture, approximately 1.2 to 1.4 times as long as basal width of mandible. Gena (Fig.  25) smooth, with dense fine punctures; centrally weakly convex. Ocellar triangle densely punctate; outside of ocellar triangle with fine leathery texture and sparse fine punctures (Fig. 26). Postocellar line about 1.5 times as long as ocular-ocellar line. Frons densely punctate, medially weak transverse convexity, evenly concave ventrally, smooth with weak wrinkles; orbits of frons with sparse punctures. Antenna with 30 to 31 flagellomeres, ratio of length from first to fifth flagellomeres: 7.0:8.0:7.0:6.0:5.0. Occipital carina complete.
Metasoma (Fig. 30). First tergum about 1.5 times as long as apical width, smooth with weak wrinkles. Median dorsal carinae distinct, almost parallel. Dorsolateral and ventrolateral carinae complete. Spiracle circular, small, located at apical 0.3 of first tergum. Second tergum about 0.6 times as long as apical width, mostly with fine longitudinal wrinkles, apically smooth with fine punctures. Third to eighth terga shiny, densely punctate. Ovipositor sheath about 0.7 times as long as hind tibia. Ovipositor straight, strong, with small nodus, apically sharp.