Dryocosmus rileypokei Morita & Buffington
Creators: name: Nicholls, James A.
name: Melika, George
name: Stone, Graham N.
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hymenoptera
Cynipidae
Dryocosmus
Dryocosmus rileypokei

description: Dryocosmus rileypokei Morita & Buffington
Figs 46–85
Material examined. Sexual generation: 13 females and 5 males labelled as “ USA, California, 30 km E of Arcata (CA1205), ex Chrysolepis chrysophylla, leg. J. Nicholls, 2009.08.17”; 4 females and 4 males labelled as “ USA, California, Little Jones Creek road (CA1207), ex Chrysolepis chrysophylla, leg. J. Nicholls, 2009.08.14”.
Asexual generation: 3 females labelled as “ USA, California, 30 km E of Arcata, leg. J. DeMartini, coll. 2012.10.0 1, adult emerge 2014.03.15, ex Chrysolepis chrysophylla (spCAb7)”; 1 female labelled as “ USA, California, 30 km E of Arcata, leg. J. DeMartini, coll. 2011.10.27 ex Chrysolepis chrysophylla (CA1308, spCAb7_11)”.
Diagnosis. For the sexual generation see Diagnosis to D. juliae, new species. Asexual females most closely resemble D. castanopsidis. In D. rileypokei asexual females, the head is 2.6x broader than long in dorsal view (Fig. 70), the median mesoscutal line absent, anterior parallel lines impressed, distinct in anterior 1/4 of the mesoscutum, parapsidal lines invisible, parascutal carina broad, anteriorly reaching tegula (Figs 76–77), the radial cell of the forewing 4.3x longer than broad (Fig. 74) while in D. castanopsidis asexual females the head is 2.2x broader than long from dorsal view (Fig. 87), the median mesoscutal line distinct, broad, reaching to 1/10 of the mesoscutum length, anterior parallel lines invisible, parapsidal lines broad, reaching about 2/3 length of the mesoscutum, parascutal carina broad, anteriorly reaching notaulus (Fig. 93), the radial cell of the forewing only 3.6x longer than broad (Fig. 91).
Description. Sexual generation (Figs 46–68). A detailed description of the sexual female is given in Buffington & Morita (2009). Thus, here we provide a description of the males outlining those characters only that differ from the female. Pictures of female and male are given (Figs 46–68).
MALE (Figs 50–53, 55, 62–64, 68). Head dark brown to black; mandibles, labial and maxillar palps yellow; antenna brown; mesosoma and metasoma dark brown; legs uniformly yellow.
Head alutaceous, with sparse white setae, denser on lower face, vertex, occiput postocciput and postgenae. Malar space alutaceous, with striae radiating from clypeus and reaching eye. Inner margins of eyes parallel. POL 1.6x longer than OOL; OOL 1.2x longer than diameter of lateral ocellus, 1.3x longer than LOL; ocelli ovate, all equal in size, larger than in female. Antenna coloured as in female, with 13 flagellomeres, as long as body; F1 distally broadened, excavated in basal half, as long as length of scape+pedicel, as long as F2, F2 1.25x longer than F3, F3=F4, F5–F13 shorter than F4 and nearly equal in length; placodeal sensilla on F3–F13. Mesosoma the same as in female, only the anterior parallel lines are invisible. Body length 2.2–2.5 mm (n=8).
Asexual female (Figs 69–79). Body uniformly reddish brown, antenna and legs slightly lighter than body.
Head alutaceous, with dense white setae, denser on lower face, vertex, occiput, postocciput; 2.6x broader than long in dorsal view; 1.3x broader than high in anterior view and slightly broader than mesosoma. Gena alutaceous, broadened behind eye in dorsal view; as broad as cross diameter of eye in lateral view. Malar space coriaceous, with striae radiating from clypeus and reaching eye margin; eye 1.8x higher than length of malar space. Inner margins of eyes parallel. POL 1.4x longer than OOL; OOL 1.9x longer than diameter of lateral ocellus, 1.9x longer than LOL; ocelli ovate, all equal in size. Transfacial distance 1.4x longer than height of eye and 1.3x longer than height of lower face (distance between antennal rim and ventral margin of clypeus); diameter of antennal torulus 1.6x longer than distance between them, distance between torulus and eye margin 1.3x longer than diameter of torulus. Lower face delicately coriaceous, with white setae, without striae radiating from clypeus, median area not elevated. Clypeus trapezoid, concave, broader than high, coriaceous, with deep anterior tentorial pits, distinct epistomal sulcus and clypeo-pleurostomal line; ventrally straight, not emarginate, not incised medially, with dense long setae reaching far beyond ventral margin of clypeus. Frons alutaceous, with rare short setae; vertex, interocellar area and occiput delicately coriaceous with rare short white setae. Postgena alutaceous, glabrous, with dense setae, postocciput around occipital foramen impressed, smooth, glabrous, with delicate striae along occiput; posterior tentorial pits large, deep, elongate; postgenal bridge narrowed to a stripe towards oral foramen, 2.0x higher than broad; occipital foramen as high as height of postgenal bridge, 1.8x shorter than height of oral foramen. Antenna with 12 flagellomeres, longer than head+mesosoma; pedicel 1.5x as long as broad, F1 shorter than length of scape+pedicel, only slightly longer than F2, F2 1.2x longer than F3, F3 1.1x longer than F4 and slightly longer than F5, subsequent flagellomeres nearly equal in length, F12 1.5x longer than F11; placodeal sensilla invisible on F1–F3, distinct on all subsequent flagellomeres.
Mesosoma longer than high in lateral view. Pronotum smooth, glabrous; with white setae and without striae laterally; emarginate along lateral edge, followed by deep longitudinal invagination. Anterior rim of pronotum narrow, emarginate; propleuron alutaceous, with few setae, strongly concave in mediocentral part. Mesoscutum alutaceous, glabrous between notauli; longer than broad (width measured across base of tegulae); notauli complete, deeply impressed along full length, broader basally, with smooth bottom; median mesoscutal line absent; anterior parallel lines impressed, distinct in anterior ¼ of mesoscutum; parapsidal lines invisible; parascutal carina broad, anteriorly reaching tegula. Transscutal articulation deep, distinct, straight. Mesoscutellum longer than broad, trapezoid, narrowed towards transscutal articulation, broadest part posteriorly; shorter than mesoscutum, uniformly rugose, overhanging metanotum; scutellar foveae as long as broad, with glabrous, smooth bottom, divided by narrow central elevated area. Mesopleuron smooth, glabrous, with dense white setae along ventral and anterior margins; speculum smooth, glabrous; mesopleural triangle coriaceous, glabrous, with dense white setae. Metapleural sulcus reaching mesopleuron halfway up its height; preaxilla coriaceous, glabrous; dorsal and lateral axillar areas glabrous, alutaceous, with dense setae; axillar carina broad, with longitudinal striae; subaxillular bar narrow, smooth, glabrous, at posterior end as high as height of metanotal trough. Metascutellum rugose, 2.0x shorter than the height of the smooth, glabrous ventral impressed area; metanotal trough smooth, glabrous, with dense white setae. Lateral propodeal carinae distinct, bent outwards at their posterior ends, central propodeal area smooth, glabrous, without rugae; lateral propodeal area smooth, glabrous, with dense white setae; nucha short, glabrous, without longitudinal sulci dorsolaterally and laterally.
Forewing longer than body, with pale yellowish veins, margin with long dense cilia; radial cell 4.3x longer than broad, R1 and Rs nearly reaching wing margin; areolet large, triangular, well-delimited by distinct veins; Rs+M pale, short, its projection reaching basalis at half its height. Tarsal claws simple, without basal lobe. Hind tarsomere 1 as long as hind tarsomeres 2–5.
Metasoma slightly longer than head+mesosoma, as long as high in lateral view, smooth, glabrous, without micropunctures; 2nd metasomal tergite basally with dense white setae only laterally, ring of dense setae interrupted dorsally; 2nd tergite extending at least to 2/3 of metasoma length; prominent part of ventral spine of hypopygium at least 2.0x longer than broad in ventral view, with long white setae ventrally, extending beyond apex of spine but never forming a tuft. Body length 3.5–3.6 mm (n=4).
Gall. Sexual generation galls develop in the cupule part of the fruit (Figs 80–81). The larval chambers are within the mesocarp tissue of the developing fruit; infested fruit do not develop seeds. A detailed description of galls is given in Buffington & Morita (2009).
Asexual generation galls develop in axillary buds (Figs 82–85). Galls are typically ovoid, occasionally more spherical, narrowing towards the point of attachment with the host plant at the base of the gall; approximately 8–9 mm in diameter. The gall surface is textured, with scattered pubescence or small raised bumps (similar to the catkin galls of D. castanopsidis); brownish-purple in colour. As the gall matures, an air space develops between the larval cell and surrounding parenchyma tissue, although the larval cell is never completely free. Galls are quite similar to those of D. demartinii and are induced on the same part of the plant as that species, but are more ovoid in shape, have a textured surface and develop an air space around the larval cell when mature.
Comments. Although the original description of this species was only of females (Buffington & Morita 2009), we have subsequently reared males from galls induced in fruits, thus demonstrating these galls belong to the sexual generation. The asexual generation has been matched with the sexual generation based on DNA sequences. Formal description and diagnosis for the asexual females and their galls are given for the first time.
Biology. Alternating sexual and asexual generations are known. Sexual galls in fruit were collected from July to the first half of September. Adults emerged under laboratory conditions soon after collection. Asexual bud galls develop during late summer/autumn, are mature by October, and fall to the ground to overwinter. Adults emerge the following spring. A proportion of asexual larvae have an extended period of diapause and emerge in early spring two years after galls were induced.
Distribution. USA, California.
description: Published as part of Nicholls, James A., Melika, George & Stone, Graham N., 2018, New species of Dryocosmus Giraud gallwasps from California (Hymenoptera: Cynipidae: Cynipini) galling Chrysolepis Hjelmq. (Fagaceae), pp. 407-433 in Zootaxa 4532 (3) on pages 419-423, DOI: 10.11646/zootaxa.4532.3.6, http://zenodo.org/record/2615473