Synergus villosus Gillette, 1891

Lobato-Vila, Irene & Pujade-Villar, Juli, 2021, The genus Synergus Hartig (Hymenoptera: Cynipidae: Synergini) in the New World: a complete taxonomic revision with a key to species, Zootaxa 4906 (1), pp. 1-121 : 95-97

Synergus villosus Gillette, 1891

( Figure 38 )

Synergus villosus Gillette, 1891 . Bull. State Lab. Nat. Hist. 3: 202. Type material: USNM.

Type material (examined). LECTOTYPE ♀ with the following labels: ‘ Mich’ (white label) / ‘ Ac. Cat. 224’ (white label) / ‘ Gillette’ (white label) / ‘12’ (white label, handwritten) / ‘ Synergus villosus Type, n.sp.’ (white label, handwritten) / ‘na Gil’ (white label, handwritten) / ‘ AccNo 71950, USNM to be loaned only to ColoAgCol’ (white label) / ‘USNMENT 00802410’ (white label, QR code) / ‘ Lectotype ♀ Synergus villosus Gillette, 1891 , IL-V desig-2017’ (red label).

Diagnosis. Synergus villosus belongs to a group of species characterized by having the mesopleuron entirely sculptured, including the speculum; hyaline wings and radial cell of fore wing at most 2.5 times as long as wide; POL longer than OOL; F1 as long as F2 and female antenna with 14 segments, rarely 15; mesoscutum with transversal carinae, interspaces sculptured; notauli complete, reaching the posterior margin of pronotum; tarsal claws bidentate, with a basal lobe; first metasomal segment completely sulcate dorsally and laterally; and syntergum posteriorly with a band of micropunctures. Synergus villosus differs from the rest of species sharing these traits ( S. ficigerae , S. ochreus , S. duricorius , S. beutenmulleri , S. linnei , S. erinacei , S. nigroornatus , S. oneratus and S. rutulus ) by having lateral pronotum coriaceous, without transversal carinae nor wrinkles ( Fig. 38a ) (wrinkled or carinated, sometimes coriaceous but at least with some carinae or wrinkles ventrally in the rest of species); mesoscutum weakly sculptured, imbricated, without carinae nor transversal elements, with some punctures ( Fig. 38b ) (strongly or weakly, but always densely, transversely carinated, rarely coriaceous with weak transversal elements not forming true carinae in the rest of species); speculum medially with a small smooth spot (without a smooth spot in the rest of species); and female antenna with 15 segments (14 in the rest of species, except in S. ochreus ).

Redescription

FEMALE. Length. Body length 2.1 mm (n = 1).

Color ( Fig. 38 ). Black and yellow. Lower face and gena, yellow; frons, vertex medially and occiput, black. Antenna yellow. Mesosoma black; tegulae, yellow. Metasoma yellow lateroventrally and posteriorly, black dorsally and laterodorsally. Legs yellow. Wings hyaline, veins yellow.

Head. In frontal view ( Fig. 38c ) subtrapezoid, about 1.2 times as wide as high, gena not broadened behind eye. Face faintly pubescent, lower face with striae radiating from clypeus. Clypeus indistinct, ventral margin straight, not projected over mandibles. Malar space about 0.5 times as long as height of eye. Anterior tentorial pits visible; pleurostomal and epistomal sulcus absent. Transfacial line slightly shorter than height of eye. Toruli situated midheight of eye; distance between torulus and eye as long as diameter of torulus; distance between toruli as long as diameter of toruli. Frons ( Fig. 38c ) finely coriaceous and punctate; frontal carinae narrow and weak, branched before reaching lateral ocelli. Head in dorsal view is about 2.0 times as wide as long. Vertex finely coriaceous and punctate. POL: OOL: LOL = 16: 9: 8 and diameter of lateral ocelli, 7. Occiput weakly coriaceous and punctate.

Antenna ( Fig. 38b ). 15-segmented; filiform, nearly as long as the body, not broadened apically; pubescence dense and short. Scape plus pedicel slightly shorter than F1; pedicel 1.5 times as long as wide; F1 and F2 subequal; the following segments progressively shorter. Last flagellar segment about 3.0 times as long as wide and 1.7 times as long as F12.

Mesosoma. About 1.2 times as long as high in lateral view, including nucha, with short and not dense pubescence ( Fig. 38a ). Ratio of length of pronotum medially/laterally: 0.28. Pronotal plate indistinct. Lateral pronotum coriaceous; lateral carina absent, lateral margins of pronotum rounded seen from above. Mesoscutum ( Fig. 38b ) about 1.2 times as wide as long, imbricated, glabrous and shining, with some punctures; anterior parallel lines shallow, reaching 1/3 of the mesoscutum; notauli complete and well impressed in their whole length, wider and convergent posteriorly; median mesoscutal line weakly impressed but visible, reaching almost 1/3 of the mesoscutal length; parapsidal lines weakly impressed, almost inconspicuous. Mesoscutellum ( Fig. 38b ) about as long as wide, wrinkled; circumscutellar carina weak but visible, obscured by wrinkles; scutellar foveae ovate, shallow, weakly sculptured bottom, the posterior margin not well defined and separated by a narrow carina. Mesopleuron ventrally regularly striated, anteriorly reticulated, speculum striated, medially with a smooth spot. Metapleural sulcus reaching 3/4 of mesopleural height. Nucha sulcate dorsally and laterally.

Legs. Tarsal claws with a strong basal lobe.

Wings. Fore wing pubescent with short marginal setae, slightly longer than the body length ( Fig. 38a ). Radial cell closed, about 2.5 times as long as wide; areolet small, almost indistinct. Rs+M inconspicuous, not reaching the basal vein. Basal cell with sparsely spaced setae.

Metasoma. About as long as head plus mesosoma and about 1.3 times as long as high in lateral view ( Fig. 38a ). First metasomal segment sulcate dorsally and laterally. Syntergum smooth, anterolateral pubescence composed of a few setae and posteriorly with a very narrow band of micropunctures extended at most 1/6 its length; strongly dorsodistally incised, not pointed. Hypopygial spine as long as wide and with a few lateral setae; without apical setae.

MALE. Unknown.

Distribution. USA: Iowa ( Gillette 1891).

Biology. Reared from galls of Acraspis villosa Gillette, 1888 ( Gillette 1891) .

Remarks. Synergus villosus was described from two specimens ( Gillette 1891: 203), which seem to be females according to the original description. We located and examined 1♀ belonging to the type series deposited in USNM, which has been designated as lectotype. The first label of the lectotype reads ‘Mich’ instead of ‘Io’ o ‘Iowa’. Also, Burks (1979) states that this species is known from Michigan instead of Iowa, probably due to what the label of the lectotype says. We believe this to be an error.

The host plant is neither mentioned in the original description nor in subsequent works; however, A. villosa is commonly found on leaves of Q. arizonica , Q. grisea , Q. macrocarpa , and Q. gambelii ( Burks 1979) .

Figures

FIGURE 38. Synergus villosus (lectotype, USNMENT 00802410): a) lateral habitus; b) dorsal habitus; c) head in frontal view.