Synergus minutus Lobato-Vila & Pujade-Villar, sp. nov.

(Figures 1–2)

urn:lsid:zoobank.org:act: 3FD2C68B-502B-4ED3-936D-487983EB1D98

Type material. HOLOTYPE ♂ deposited in CNU with the following labels: ‘ KOR: 32, Mt 1–32, Otan-ru, Yeong- dong-eup, Yeongdong-gun, Chungcheongbuk-do (South Korea)’ (white label) / ‘Ex. Trichagalma acutissimae (asexual), Q. variabilis, (25.vi.2019) 1–15.vii.2019, M. J. Kang leg.’ (white label) / ‘ Holotype ♂ Synergus minutus Lobato-Vila & Pujade-Villar, desig. Lobato-Vila 2020’ (red label). PARATYPES (3♂ & 1♀) deposited in CNU (1♂) and UB (2♂ & 1♀) with the following labels: same as the holotype: 1♀ (deposited in UB); ‘ KOR: 31, Mu- deung-ro, Buk-gu, Gwangju (South Korea)’ (white label) / ‘Ex. Trichagalma acutissimae (asexual), Q. acutissima, (24.ix.2019) 21.x.2019, S. B. Choi leg.’ (white label) / ‘ Paratype ♂ Synergus minutus Lobato-Vila & Pujade-Villar, desig. Lobato-Vila 2020’ (red label) (3♂; 1♂ deposited in CNU, 2♂ deposited in UB).

Etymology. Adjective relative to the small size of both sexes.

Diagnosis. Synergus minutus, sp. nov. is similar to S. chinensis . However, it differs from this species by having the head weakly sculptured, with minute and sparse piliferous punctures (conspicuously punctate in S. chinensis); the head 1.8 times as wide as long in dorsal view (about 2.5 in S. chinensis); F1 2.0 times as long as F 2 in both sexes (1.3 in females and 1.5 in males of S. chinensis) and about 1.5 times as long as pedicel in both sexes (2.0 times in S. chinensis); F1 of males slightly expanded apically (more conspicuously expanded apically than basally in S. chinensis); the median mesoscutal groove short, not reaching the half of the mesoscutal length, sometimes appearing as a small incision (long, almost reaching the pronotal margin, in S. chinensis) and the radial cell of fore wings weakly pigmented and about 2.6 times as long as wide (easily traceable and about 3.0 times as long as wide in S. chinensis). Furthermore, both females and males of S. minutus are about 1.0 mm long (from 2.1 to 3.5 mm long in both sexes of S. chinensis).

Description. FEMALE. Length. Body length 1.1 mm (n = 1).

Color (Figs 1a, 1c). Lower face and genae light brown; frons, lateral sides of vertex and occiput, dark brown; ocellar area, black. Antennae yellow. Mesosoma dark brown; tegulae yellow. Metasoma chestnut. Legs yellow. Wings hyaline, veins pale, hardly traceable.

Head. Round to subtrapezoid, about 1.2 times as wide as high in anterior view (Figs 1c, 2a), genae not expanded behind compound eyes. Face faintly pubescent, lower face with striae radiating from clypeus, reaching compound eyes and toruli. Clypeus indistinct, ventral margin straight, not projected over mandibles. Malar space somewhat more than 0.6 times as long as height of compound eye. Anterior tentorial pits visible; pleurostomal and epistomal sulcus absent. Transfacial line almost 1.2 times as long as height of compound eye. Toruli situated slightly under mid-height of compound eyes; distance between torulus and compound eye about as long as diameter of toruli; distance between toruli shorter than diameter of toruli. Frons delicately alutaceous to coriaceous, with minute and sparse piliferous punctures; lateral frontal carinae narrow, discontinuous, reaching lateral ocelli. Head in dorsal view (Fig. 2b) is about 1.8 times as wide as long. Vertex delicately alutaceous to coriaceous, with minute and sparse piliferous punctures. POL: OOL: LOL = 9: 5: 4.5 and diameter of lateral ocelli, 3.0. Occiput delicately alutaceous to coriaceous.

Antennae (Fig. 2e). 14-segmented (5: 4: 6: 3: 3: 3.5: 4: 4: 4: 4: 4: 4: 4: 9); subclavate, slightly broadened apically; pubescence dense and short; placodeal sensilla on F1–F12. Pedicel almost 2.0 times as long as wide; F1 2.0 times as long as F2, F2 as long as F3. Last flagellar segment about 3.5 times as long as wide and almost 2.3 times as long as F11.

Mesosoma. About 1.2 times as long as high in lateral view including nucha (Fig. 2g), with moderately long but not dense pubescence. Ratio of length of pronotum medially/laterally: 0.3. Pronotal plate indistinct. Lateral pronotum coriaceous with weak carinae; lateral carina present and complete, but weak. Mesoscutum (Fig. 2h) about 1.3 times as wide as long, delicately coriaceous with some weak discontinuous transversal spaced carinae; anterior grooves shallow, short. Notauli complete and well defined, deep, somewhat convergent posteriorly. Median groove short, not reaching the half of the mesoscutal length, interrupted by the sculpture of the mesoscutum; sometimes appearing as a small incision. Parapsidal grooves shallow, surpassing tegulae. Scutellum (Fig. 2h) rounded, about as long as wide, weakly wrinkled; circumscutellar carina absent; scutellar foveae shallow, bottom smooth and shiny, subtriangular, well defined and separated by a narrow carina. Mesopleuron (Fig. 2g) finely and uniformly striate, interspaces smooth and shiny; slightly pubescent basally. Metapleural sulcus reaches about 4/5 parts of mesopleural height. Propodeum (Fig. 2j) faintly pubescent, smooth; propodeal carinae narrow and parallel, slightly convergent distally. Nucha weakly sulcate dorsally and laterally (Fig. 2g).

Legs. Tarsal claws bidentate, with a basal lobe (Fig. 2i).

Wings. Fore wings pubescent with long marginal setae, slightly longer than body length. Radial cell closed and 2.6 times as long as wide; areolet with the only posterior vein well pigmented. Rs+M inconspicuous, not reaching the basal vein. Basal cell sparsely setose.

Metasoma. About as long as head+mesosoma, slightly longer than high in lateral view (Fig. 2k). First metasomal segment sulcate dorsally and laterally. Syntergite smooth, anterolateral pubescence composed of a few setae, posterodorsally with micropunctures forming a small patch somewhat laterally extended (Fig. 2l); slightly dorsodistally incised, not pointed. Hypopygial spine about as long as wide and with a few lateral setae; without apical setae.

MALE. Similar to female, except for the following morphological traits: body length 1.1–1.2 mm (n = 4). Antennae (Fig. 2f) filiform, 15-segmented (6: 5: 7: 3.5: 4: 4: 4: 4: 4: 4: 4: 4: 4: 4: 5.5); F1 slightly curved, weakly incised medially, slightly expanded apically. POL: OOL: LOL = 10: 4: 5, diameter of lateral ocelli 3.5 (Fig. 2d). Transfacial line about as long as height of compound eye. Malar space almost 0.6 times as long as height of compound eye (Fig. 2c). Metasoma shorter than head plus mesosoma. Lower face and genae, yellow; frons and vertex, black; mesosoma dark brown to black (Figs 1b, 1d).

Distribution. South Korea. Chungcheongbuk-do and Jeollanam-do provinces.

Biology. Reared from asexual galls of Trichagalma acutissimae on Quercus variabilis and Q. acutissima .