Synergus dimorphus Osten-Sacken 1865

Synergus dimorphus Osten-Sacken, 1865

(Figure 11)

Synergus dimorphus Osten-Sacken, 1865. Proc. Entomol. Soc. Phil. 4: 376. Type material: MCZ.

Type material (examined). LECTOTYPE ♀ with the following labels: ‘ S. dimorphus O.S.’ (white lable, handwritten) / ‘Osten Sacken Coll.’ (white label) / ‘Type 13969’ (red label) / ‘MCZ-ENT 00592792’ (white label, QR code) / ‘ Lectotype ♀ Synergus dimorphus Osten-Sacken, 1865, IL-V desig-2019’ (red label). PARALECTOTYPES (2♂ & 2♀) with the following labels: ‘Osten Sacken Coll.’ (white label) / ‘Type 13969’ (red label) / ‘MCZ-ENT 00592793’ (white label, QR code) / ‘ Paralectotype ♀ Synergus dimorphus Osten-Sacken, 1865, IL-V desig-2019’ (red label) (2♀ in the same pin); same data, but with the following QR codes: 00592791 (1♂), 00013969 (1♂).

Diagnosis. Synergus dimorphus belongs to a group of species characterized by having the mesopleuron entirely sculptured, including the speculum, without smooth spots; hyaline wings and radial cell of fore wing at most 2.5 times as long as wide; frons coriaceous, weakly wrinkled and/or with punctures, never with sharp striae running from toruli; gena not broadened behind eye; POL longer than OOL but less than 2.0 times; F1 longer than F2, antenna of females with 13 segments, 15 in males; margins of pronotum rounded, not swollen aside; mesoscutum with transversal carinae, interspaces sculptured; notauli complete, reaching the posterior margin of pronotum, well defined in their entire length; metasoma of females longer than high in lateral view; and syntergum without micropunctures posteriorly or just with a posterodorsal patch never laterally extended. This species differs from others belonging to this group (S. digressus, S. brevicornis and S. lignicola) by having yellow coxae in females (basally black in the rest of species); POL 1.2 times as long as OOL and OOL 1.7 times as long as diameter of lateral ocelli (Fig. 11c) (POL more than 1.5 times as long as OOL and OOL 1.3 times as long as diameter of lateral ocelli in the rest of species); and metasoma of females as long as head plus mesosoma (shorter in the rest of species), among others (see the identification key).

Redescription

FEMALE. Length. Body length 2.5–3.0 mm (n = 3).

Color. Black and rufous. Gena brownish orange, lower face infuscate medially; frons, vertex and occiput black. Antenna dark yellow. Mesoscutum, mesoscutellum and propodeum, black; pronotum and mesopleuron almost completely black, but posterodorsal sides of pronotum and dorsal mesopleuron, dark brown; tegulae dark yellow. Metasoma rufous to chestnut, dorsally black. Legs mainly yellow, tarsi and metatibiae, darker. Wings hyaline, veins yellow.

Head. In frontal view subtrapezoid, 1.2 times as wide as high, gena not broadened behind eye, face subtriangular. Face faintly pubescent, lower face with striae radiating from clypeus. Clypeus indistinct, ventral margin slightly projected over mandibles. Malar space about 0.6 times as long as height of eye. Anterior tentorial pits visible; pleurostomal and epistomal sulcus absent. Transfacial line slightly longer than height of eye. Toruli situated slightly under mid-height of eye; distance between torulus and eye about as long as diameter of torulus; distance between toruli slightly shorter than diameter of toruli. Frons coriaceous, with some scattered small punctures; frontal carinae very short, branched, almost inconspicuous. Head in dorsal view is about 2.1 times as wide as long. Vertex coriaceous, with some scattered small punctures. POL: OOL: LOL = 6: 5: 3 and diameter of lateral ocelli, 3. Occiput finely coriaceous, without punctures.

Antenna. 13-segmented; filiform, not broadened apically; pubescence dense and short. Scape plus pedicel as long as F1; pedicel about as long as wide; F1 1.5 times as long as F2, F2 and F3 subequal; the following segments progressively shorter. Last flagellar segment about 3.0 times as long as wide and about 2.0 times as long as F10.

Mesosoma. About 1.2 times as long as high in lateral view, including nucha, with short and not dense pubescence. Ratio of length of pronotum medially/laterally: 0.4. Pronotal plate indistinct. Lateral pronotum wrinkled, interspaces coriaceous; lateral carina absent, lateral margins of pronotum rounded seen from above. Mesoscutum about 1.2 times as wide as long, densely and discontinuously carinated, interspaces finely coriaceous to alutaceous; anterior parallel lines weakly impressed, reaching 1/4 of the mesoscutum; notauli complete and visible in their whole length; median mesoscutal line absent; parapsidal lines shallowly impressed, surpassing tegulae. Mesoscutellum rounded, about as long as wide, wrinkled, interspaces strongly coriaceous; circumscutellar carina visible and well defined; scutellar foveae ovate to subtriangular, weakly sculptured, shallow, not well defined posteriorly and separated by a narrow carina. Mesopleuron finely and irregularly striated. Metapleural sulcus reaching about 3/4 of mesopleural height. Propodeum pubescent and weakly sculptured; propodeal carinae slightly curved and convergent posteriorly, medially with a weak carina. Nucha sulcate dorsally and laterally.

Legs. Tarsal claws with a small basal lobe.

Wings. Fore wing pubescent with short marginal setae, about as long as mesosoma plus metasoma. Radial cell ambiguously closed (especially the posterior third), about 2.5 times as long as wide; areolet visible, but only the posterior vein well pigmented. Rs+M inconspicuous, not reaching the basal vein. Basal cell with sparsely spaced setae.

Metasoma. About as long as head plus mesosoma and about 1.2 times as long as high in lateral view. First metasomal segment sulcate dorsally and laterally. Syntergum smooth, anterolateral pubescence composed of a few setae and with a small posterodorsal patch of micropunctures; not dorsodistally incised, slightly pointed. Hypopygial spine almost 3.0 times as long as wide and with a few lateral setae; without apical setae.

MALE (Fig. 11). Similar to female, except for the following: body length 2.5 mm (n = 2). Antenna 15-segmented; F1 about 1.8 times as long as F2; F1 long, slightly curved, weakly incised medially, more broadened apically than basally. Malar space almost 0.7 times as long as height of eye. Metasoma shorter than head plus mesosoma. Head yellow, except for a black spot in the ocellar area; pronotum and mesopleuron almost completely yellow.

Distribution. USA: Washington D.C. (Osten-Sacken 1865). Also, from Michigan (Gillette 1896) and California (Fullaway 1911; McCracken & Egbert 1922), but these records need to be confirmed.

Biology. Originally reared from an unknown gall (Osten-Sacken 1865; Gillette 1896; McCracken & Egbert 1922). Gillette (1896) presumably obtained this species from ‘woody twig galls on red oaks’, and Fullaway (1911) presumably identified S. dimorphus from galls of Cynips multipunctata (Beutenmüller, 1911) on Q. lobata, which corresponds to Besbicus conspicuus (Kinsey, 1930) (= Cynips (Besbicus) multipunctata var. conspicua Kinsey, 1930), according to Kinsey (1930), but these records need to be confirmed.

Remarks. Synergus dimorphus was described from ‘numerous ♀ and two ♂’ (Osten-Sacken 1865: 377). We located and examined 2♂ and 3♀ belonging to the type series deposited in MCZ. A lectotype has herein been designated.

Kinsey (1930) differentiated several varieties for the gall wasp Cynips multipunctata, among which Cynips (Besbicus) multipunctata var. conspicua, now Besbicus conspicuus following Weld (1951) and Burks (1979), corresponds to the host gall of both S. dimorphus and S. ochreus (Kinsey 1930: 230).