Dryocosmus destefanii Cerasa & Melika, 2018

Cerasa, Giuliano, Verde, Gabriella Lo, Caleca, Virgilio, Massa, Bruno, Nicholls, James A. & Melika, George, 2018, Description of Dryocosmus destefanii new species (Hymenoptera: Cynipidae: Cynipini) from Quercus suber L. in Italy, Zootaxa 4370 (5), pp. 535-548 : 538-544

Dryocosmus destefanii Cerasa & Melika new species

Figs 1–4 ; 9–27

Type material. HOLOTYPE female: ITALY: Sicily, Cefalù , loc. Campella, ex Quercus suber , 09.VI.2016, 38°1'19.06"N 13°59'15.49"E, 200m, ex small leaf galls, em[erged]. 07–15.VIII.2016, (N. 6051), G. Cerasa (Museo Civico di Storia Naturale ‘ Giacomo Doria’, Genoa, Italy) . PARATYPES: two females with the same labels as the holotype, but “em. 20–22.VIII.2016, (N. 6 044) G. Cerasa ( Collection Giuliano Cerasa , Giuliana (Palermo) Italy); two females labelled Italy , Sicily, Cefalù (PA) loc. Campella 9.VI.2016 on Quercus suber em. 20–22.VIII.2016 (N. 6044) G. Cerasa (Plant Health and Molecular Biology Laboratory, National Food Chain Safety Office, Budapest, Hungary).

Description. ASEXUAL FEMALE (holotype). Head amber, except for dark brown to black occiput and vertex; mandibles brown, maxillary palps and labial palps yellowish; antennae amber, last 5–6 flagellomeres amber to brown; eyes dark brown to black. Mesosoma amber, legs yellow-amber; tarsal claws brown. Metasoma dark brown, T2 dorsally and laterally light brown, subsequent tergites dark brown. Wings hyaline, veins yellow-brown to brown. Body length 1.1–1.3 mm.

Head nearly 1.2 times as broad as high in anterior view, 2.1–2.2 times as broad as long in dorsal view; glabrous and smooth except for a few short and indistinct or very weak striae irradiating from clypeus, more pronounced near antennal foramen. Gena very slightly broadened behind eye in anterior view. Clypeus projected over mandibles. Lower face and malar space alutaceous, with a few scarce and short white setae; frons glabrous, with impression under central ocellus. Malar space short, 0.3–0.4 times as long as height of eye. Transfacial distance 1.3–1.4 times as long as height of eye and 2.1 times as long as height of lower face (distance between antennal rim and tip of clypeus); diameter of torulus nearly equal to distance between them, distance between torulus and inner margin of eye 1.8 times as large as diameter of torulus. Ocelli slightly elevated over dorsal margin of head; OOL slightly shorter or equal to POL; OOL 4 times as long as diameter of lateral ocellus, 1.8 times as long as LOL. Inner margins of eyes slightly converging ventrally. Clypeus small, trapezoid, delicately coriaceous, with strongly elevated central area, anterior tentorial pits, epistomal sulcus and clypeo-pleurostomal line distinct, shallow, ventrally emarginated. Frons, vertex and occiput smooth, glossy, without surface sculpture. Labial palpus 3–segmented, maxillar palpus 4–segmented. Antenna filiform, with 12 flagellomeres, 1.4–1.5 times as long as body length, with long and sparse hairs; pedicel as long as broad, 0.5 times as long as scape; pedicel and scape slightly broader than flagellomeres, not more than 1.5–1.7 times broader than flagellomeres; F1–F12 nearly equal in breadth, F5–F12 very slightly broader than F2–F4; scape 1.3 times as long as F1; F1 slightly longer than F2, F3–F9 distinctly longer than broad; F10–F11 only slightly longer than broad and F10 nearly equal in length to F11; F12 nearly equal in length to F1; placodeal sensilla present on all flagellomeres, hardly traceable on F1. In some specimens an indistinct suture appears on the last antennomere.

Mesosoma very high, only 1.1 times as long as high, smooth, glossy, without pubescence, except some scattered white setae along notauli and lateral edges, on mesopleural triangle and mesoscutellum. Pronotum smooth, glossy, with delicate striae in posterodorsal part and with scattered white setae along anterolateral edge; emarginated along ventrolateral edge, with distinct striae along the impressed emarginated anterior rim; anterior rim of pronotum narrow, amber to brown; propleuron amber, delicately coriaceous, concave in mediocentral part with a few scattered white setae. Mesoscutum slightly broader than long in dorsal view (largest width measured at the level of the base of tegulae). Notaulus complete, well impressed along all its length, converging at the posterior end; parapsidal lines and anterior parallel lines absent, median mesoscutal line absent; parascutal carina distinct. Mesoscutellum, rounded, nearly as long as broad from dorsal view; smooth, glossy, without surface sculpture, emarginated along lateral and posterior edges, slightly overhanging metanotum; the part which overhangs metanotum is areolate-rugose along lateral sides and with wrinkles posteriorly (visible in posteroventral view on Fig. 19 ). Scutellar foveae subtriangular, deep, with smooth glossy bottom, separated by median carina with diverging sides, wider and shorter, 1/8 of mesoscutellum length. Mesopleural triangle with sparse and short white setae and some wrinkles. Mesopleuron smooth, glossy, without striae, acetabular carina delimiting a very narrow area laterally. Preaxilla delicately coriaceous, glossy; dorsal and lateral axillar areas smooth, glossy, with sparse short white setae; axillar carina narrow, without longitudinal striae; axillula smooth, glossy, without setae or with rare and scattered white setae; subaxillular bar triangular, narrow, coriaceous, glossy, at most posterior end as high or slightly shorter than height of metanotal trough; metapleural sulcus straight, reaching mesopleuron slightly above 1/3 of its height ( Fig. 17 ). Metascutellum trapezoid, irregularly sculptured, slightly curved inferiorly, nearly 1.5 times as broad as high; equal or slightly higher than height of smooth, minutely wrinkled ventral impressed rim of metanotum; metanotal trough alutaceous, without setae. Central propodeal area smooth, glossy, with numerous delicate irregular wrinkles; lateral propodeal area coriaceous, with rare white setae; lateral propodeal carina strongly curved outwards in the middle. Nucha very short, with irregular longitudinal wrinkles dorsolaterally and laterally.

Forewing pubescent, hyaline, much longer than body, with very long marginal cilia (marginal cilia length/ forewing width=0.12); radial cell open, 4.5 times as long as broad; R1 and Rs reaching wing margin, R1 imperceptibly extending along wing margin and Rs slightly extending along wing margin; 2 r almost straight, only slightly curved; areolet distinct, triangular, large; Rs + M reaching basal vein in its lower half.

All tarsal segments longer than broad, T1 the longest one, tarsal claws simple, without basal lobe; fore leg tarsomere I to V ratio as 1.0:0.5:0.4:0.3:0.6; tibial spur of foreleg very long, curved inward, bifid at apex, nearly 0.6 times as long as basitarsus.

Metasoma strongly compressed laterally, higher than long in lateral view; slightly shorter than head + mesosoma; slightly larger than mesosoma; metasomal tergite 2 occupying nearly half the length of metasoma in dorsal view; all tergites smooth, glossy, without setae and micropunctures or with rare and scattered white setae anterolaterally on metasomal tergite 2. Prominent part of ventral spine of hypopygium short, less than 1.6 times as long as broad, with long and scattered white setae reaching beyond apex but never forming apical tuft.

Gall ( Figs 1–4 ). Asexual generation. Gall is 1–3 mm in diameter, subsphaerical to ellipsoid in shape, with the longest axis parallel to the leaf surface. Young growing galls are red, with warty surface covered with translucent tiny blister-like humps ( Figs 2–3 ); when mature they turn reddish-brown. Galls are fixed to the median or lateral veins of lower leaf surface through a short, whitish stalk; typically 3–8 or even more galls can be found on one leaf (maximum number observed is 17 galls on a leaf). The gall wall is thin ( Fig. 4 ), spongy on its inner surface and slightly woody externally. A single larval chamber is present in each gall.

Biology. Only the asexual generation is known, and induces tiny subspherical leaf galls on Quercus suber L. This is the only oak host known for this species, with no records from other sympatric section Cerris oaks, Quercus cerris L. or Quercus gussonei (Borzì) Brullo. Galls develop in May, complete their development whilst remaining fixed to the leaf on the tree and adults emerge in August and the first half of September. The biology of other Dryocosmus species suggests that a sexual generation, if one exists, should be found on the same oak host.

The new species has emergence in August, which is unusual for asexual females compared with other oak gall wasp species with heterogonic life-cycles. In other species associated with Q. suber , the asexual females never emerge in late summer, but instead in late winter or the early spring of the year following gall induction. It is possible that the new species has a life history similar to that of D. kuriphilus and D. zhuili , i.e., it does not have a sexual generation and only reproduces asexually (cf. Zhu et al., 2015). Alternatively, the differences in the adult emergence period between the new species and other heterogonic congeners are due to the peculiar climatic conditions of Sicily.

Etymology. The species is named in honor of the distinguished Italian entomologist Teodosio De Stefani Perez (1853–1935) for his contributions to the study of cecidology and systematics of Hymenoptera .

Diagnosis. The new species most closely resembles Dryocosmus caspiensis Melika, Sadeghi, Atkinson, Stone & Barimani , in which the pedicel and scape are very broad, at least 2.2–2.5 times broader than flagellomeres; flagellomeres broadened towards the apex, F8–F12 at least 2.0 times as broad as the first few flagellomeres; the mesoscutum distinctly broader than long in dorsal view; the mesoscutellum quadrangular, elongated, with nearly parallel lateral sides, 1.5 times as long as broad from dorsal view; the scutellar foveae are subquadrangular, separated by a distinct long and narrow median carina, median carina occupying 1/4 of the mesoscutellum length; the metapleural sulcus is curved; metascutellum alutaceous to delicately coriaceous, very short, only slightly higher than the height of the ventral impressed area of metanotum, which is smooth, glossy, without wrinkles; the metanotal trough alutaceous, with very few short white setae; R1 not reaching the wing margin while Rs nearly reaching it; the ventral spine of the hypopygium with very few short white setae, not extending beyond the apex of the spine. In contrast in D. destefanii new species, the pedicel and scape are slightly broader than flagellomeres, not more than 1.5–1.7 times broader than flagellomeres; F1–F12 nearly equal in breadth, F5–F12 very slightly broader than F2–F4; the mesoscutum slightly broader than long in dorsal view; the mesoscutellum rounded, nearly as long as broad from dorsal view; the scutellar foveae are subtriangular, separated by short median carina with diverging sides, wider and shorter, median carina occupying 1/8 of the mesoscutellum length; the metapleural sulcus is straight; the metascutellum trapezoidal, irregularly sculptured, slightly curved inferiorly, broad, nearly 1.5 times as broad as high, equal or slightly higher than the height of the ventral impressed rim of metanotum; which is smooth, with minute wrinkles; the metanotal trough alutaceous, without setae; R1 and Rs reaching wing margin ( Fig. 15 ), R1 imperceptibly extending along wing margin and Rs slightly extending along wing margin; the ventral spine of the hypopygium with long and scattered white setae reaching beyond the apex of spine ( Figs 23–24 ). It also somewhat resembles Chilaspis israeli (Sternlicht) and C. nitida (Giraud) , but has scutellar foveae are separated by a median carina and distinctly delimited posteriorly, whereas the scutellar foveae in the latter species are not separated by a median carina and are not distinctly delimited posteriorly. In addition, the asexual generation of C. nitida antenna has 11 flagellomeres and the female of the sexual generation of C. israeli has antennae with 13 flagellomeres and central tarsomeres (Ts2–Ts4) that are very short, strongly transverse ( Fig. 6 in Pujade-Villar et al. 2003). In D. destefanii new species, the antenna has 12 flagellomeres ( Fig. 15 ) and tarsomeres are of normal length ( Fig. 25 ). Finally, adult females of the sexual generation of C. nitida are 2.3–2.8 mm in length while in D. destefanii adults are 1.1–1.3 mm in length. D. destefanii and C. nitida were also reported from the same localities in Sicily.

Similar galls. The overall form of the gall is similar to the asexual generation of Dryocosmus caspiensis . In D. destefanii new species the surface of the gall is warty, covered in translucent hairs with clubbed tips; the galls are fixed to the leaf through a short and thin peduncle, while in D. caspiensis the surface of the gall is covered in dense brownish hairs with pointed tips and the peduncle is a little longer and thicker ( Fig. 8 ).

Distribution. Currently known only from Sicily ( Italy).

Comments. A 433 base-pair fragment of the cyt b gene was successfully amplified for 24 individuals representing 10 species (GenBank accession numbers KY655905 - KY655925 ). Variation within species was minimal, ranging from 0 to 1.3% ( Table 2; values on diagonal). The cyt b sequence for D. destefanii new species was most similar to the complex containing D. caspiensis , D. mayri and D. tavakolii (divergences between 4.1% and 6.3%; Table 2). The observed divergence between D. destefanii new species and the morphologically very similar D. caspiensis is approximately the same or greater than the divergence seen between other recently described Iranian/European species pairs: Andricus schoenroggei Melika & Stone from Iran and A. sieboldi (Hartig) from Europe (4.7%), A. csokai Melika & Tavakoli from Iran and A. quercusradicis (Fabricius) from Europe (6.8%), A. chodjaii Melika from Iran and A. seckendorffi (Wachtl) from Europe (2.3%), and A. megatruncicolus Melika from Iran and A. truncicolus (Giraud) from Europe (2.3%; Tavakoli et al. 2008). These divergence values are consistent with those expected for within- and between-species variation both in gallwasps ( Nicholls et al. 2012) and among insects in general ( Hebert et al. 2003), supporting the distinctiveness of the newly described D. destefanii .

Figures

FIGURES 1–9. 1–4, Dryocosmus destefanii new species, galls: 1–3, general appearance; 4, dissected gall, showing thin gall wall; 5–7, Chilaspis nitida, galls: 5–6, general appearance; 7, dissected gall, showing the small larval chamber and the thick gall wall; 8, Dryocosmus caspiensis, galls, arrows show the peduncle; 9, Dryocosmus destefanii new species, habitus, asexual female (lateral view).

FIGURES18–27. Dryocosmus destefaniinew species,asexual female:18,metascutellum and propodeum, posterodorsal view, 19, Magnification of the metascutellumand propodeum (postero-ventral view); 20, pronotum and propleuron, frontal view; 21, forewing;22, metasoma (lateral view); 23, ventral spine of hypopygium, ventral view; 24, ventral spine of hypopygium, lateral view; 25, fore tarsus and protibial spur; 26, mid tarsus andmid tibial spur; 27, hind tarsus and hind tibial spur.

FIGURES 10–17. Dryocosmus destefanii new species, asexual female: 10, head (front view); 11, head (posterior view); 12, head (dorsal view); 13, head (lateral view); 14, Magnification of the lower face and malar space; 15, antenna; 16, mesoscutum and mesoscutellum (dorsal view); 17,mesosoma (lateral view).