Neuroterus floccosus (Bassett, 1881)

Nicholls, James A., Melika, George, Digweed, Scott C. & Stone, Graham N., 2022, Pairing of sexual and asexual generations of Nearctic oak gallwasps, with new synonyms and new species names (Hymenoptera: Cynipidae, Cynipini), Zootaxa 5145 (1), pp. 1-79 : 41-47

Neuroterus floccosus (Bassett, 1881) , comb rev., sexual generation

Figs 121–150

Synonyms: Cynips floccosa Bassett (1881b: 111) , asexual female, gall. Neuroterus floccosus combination by Mayr (1881: 37). Neuroterus verrucarum var. floccosus combination by Kinsey (1923: 70); combination of Mayr (1881) restored by Weld (1951: 621).

Neuroterus verrucarum var. pernotus Kinsey, 1923 . Synonymized by Weld (1951: 621).

Melika & Abrahamson (1997) erroneously synonymized N. floccosus with N. quercusverrucarum .

Material examined: Nine asexual females labelled as “ Canada, Manitoba, Assiniboine Forest, 49.85862°N, - 97.25015°W, GPS ± 10m, S. Digweed, Collected 2005.viii.30 ex Quercus macrocarpa, Reared 15-25.v.2006 ex gall of Neuroterus quercusverrucarum agamic gen.”, determined originally as Neuroterus quercusverrucarum asexual generation females by S. Digweed. Seven sexual females and 4 males labelled as “ Canada, Alberta, Edmonton, Northern Forest Centre, 53.49165°N, - 113.54291°W, GPS ± 10m, Reared 4-13.vii.2006 ex galls of Neuroterus quercusverrucarum ♂ ♀ ex Quercus macrocarpa, S. Digweed ”, determined originally as Neuroterus quercusverrucarum sexual generation females by S. Digweed. Specimens have been deposited at the USNM, PHDNRL and RAM .

Diagnosis. Asexual females of N. floccosus most closely resemble those of N. quercusverrucarum . In N. floccosus , asexual female the gena 0.5× as wide as the transverse diameter of eye in lateral view, diameter of antennal torulus 1.9× as long as distance between them, F1 as long as pedicel; the mesoscutellum trapezoid, the posterior half of which gradually narrows towards its posterior end; the metascutellum 3.0× as high as height of ventral impressed area; the prominent part of the ventral spine of hypopygium 2.0× as long as broad in ventral view, with short sparse setae ventrally. In N. quercusverrucarum the gena 1/3 the width of transverse diameter of eye in lateral view, diameter of antennal torulus slightly greater than distance between them, antenna F1 1.3× as long as pedicel; the mesoscutellum posteriorly rounded; the metascutellum as high as height of ventral impressed area; the prominent part of the ventral spine of hypopygium as long as broad in ventral view, without setae ventrally. Below the description of the asexual female is given according to current morpho-description requirements (the original description by Bassett (1881b) is very superficial).

Description. Asexual female ( Figs 121–131 ). Head, mesosoma, metasoma brown; antenna light brown; legs yellowish to white, with darker femora and tibiae.

Head alutaceous, with a few setae on lower face, 1.2× as broad as high and as broad as mesosoma in frontal view, 1.9× as broad as long in dorsal view. Gena alutaceous, not broadened behind eye in frontal view, 0.5× as wide as the transverse diameter of eye in lateral view. Malar space alutaceous, with distinct malar sulcus, eye 3.6× as high as height of malar space. Inner margins of eyes converge slightly ventrally. POL 2.0× as long as OOL; OOL 1.4× as long as diameter of lateral ocellus and equal to LOL; all ocelli ovate, of same size. Transfacial distance slightly longer than height of eye; diameter of antennal torulus 1.9× as long as distance between them, distance between torulus and eye 1.5× as long as diameter of torulus. Lower face and median slightly elevated area alutaceous, with white setae, without striae. Clypeus quadrangular, as broad as high, alutaceous, with long setae along ventral edge; ventrally not emarginate, without median incision; anterior tentorial pit small, rounded, indistinct; epistomal sulcus and clypeo-pleurostomal line impressed, distinct. Frons and interocellar area alutaceous, without setae. Vertex, occiput, postocciput, postgena alutaceous; posterior tentorial pit large, ovate, area below impressed; occipital foramen 1.5× shorter than height of postgenal bridge; hypostomal carina emarginate, continuing into postgenal sulci which are widely spaced, diverge only slightly toward occipital foramen, postgenal bridge only slightly broader than high anteriorly. Antenna longer than head+mesosoma, with 11 flagellomeres, flagellomeres half as wide as scape and pedicel, gradually broadening until F11; pedicel as long as scape, 1.5× as long as broad; F1 as long as pedicel, 1.2× as long as F2, F2 1.2× as long as F3, F3=F4, F5=F6, F7=F8=F9=F10, F11 slightly longer than F10; placodeal sensilla on F2–F11.

Mesosoma slightly longer than high. Pronotum alutaceous, without setae in front view; alutaceous laterally; propleuron alutaceous. Mesoscutum uniformly alutaceous, without setae; slightly longer than broad (greatest width measured across mesoscutum level with base of tegulae). Notaulus, anterior parallel line, median mesoscutal line and parapsidal line absent; circumscutellar carina present, narrow. Transscutal articulation absent, mesoscutum fused with mesoscutellum; as a result of fusion of the mesoscutum and mesoscutellum, the boundary between these structures is not straight but slightly curved towards the mesoscutum; the mesoscutum is emarginate posterolaterally and slightly elevated above the dorsoaxillar area. Mesoscutellum trapezoid, longer than broad, posterior half gradually narrowing towards posterior end, uniformly smooth, glabrous, without setae, overhanging metanotum. Mesopleuron higher than broad in lateral view, smooth, glabrous; mesopleural triangle smooth, glabrous, with interrupted delicate striae, without setae; dorsal and lateral axillar areas smooth, glabrous, without setae; subaxillular bar smooth, glabrous, at posterior end as high as height of metanotal trough; metapleural sulcus reaching mesopleuron at half its height, delimiting a narrow smooth area along mesopleuron; upper part of sulcus absent. Metascutellum smooth, 3.0x as high as height of narrow, smooth, glabrous ventral impressed area; metanotal trough smooth, glabrous, without setae; propodeum smooth, glabrous; propodeum uniformly alutaceous, without carinae, striae or setae. Nucha short, smooth, without sulci. Tarsal claws simple, without basal lobe.

Forewing longer than body, hyaline, margin with dense long cilia, veins brown, distinct, radial cell open, 5.0× as long as broad; R1 and Rs reaching wing margin, Rs reaching wing margin; areolet large, triangular, distinct, Rs+M brown, visible along 2/3 of its length, projection reaching basalis in the lower 1/3 of its height.

Metasoma slightly longer than head+mesosoma, slightly longer than high in lateral view; all terga weakly sclerotized, thus limits of terga hardly visible. 2nd metasomal tergum extending to 1/3 of length of metasoma in dorsal view, without setae; all terga smooth, glabrous, without micropunctures.Hypopygium without micropunctures, prominent part of ventral spine of hypopygium short, 2.0× as long as broad in ventral view, with short sparse setae ventrally. Body length 1.1–1.3 mm (n = 4).

Sexual female ( Figs 132–136 , 142–147 ). Head, mesosoma, metasoma brown; mandibles, palpi, antenna, legs lighter than body.

Head alutaceous, with sparse white setae, denser on lower face; slightly higher than broad and narrower than mesosoma in frontal view, slightly broader than long in dorsal view. Gena alutaceous, not broadened behind eye in frontal view, narrower than transverse diameter of eye in lateral view. Malar space alutaceous, with deep malar sulcus; eye 3.7× as high as height of malar space. Inner margins of eyes parallel. POL 2.5× as long as OOL; OOL slightly longer than diameter of lateral ocellus and slightly shorter than LOL; all ocelli elongate, ovate, of same size. Transfacial distance shorter than height of eye; diameter of antennal torulus longer than distance between them, distance between torulus and eye longer than diameter of torulus. Toruli located in upper 1/3 of face (lower face+frons) height. Lower face alutaceous, without striae, median area not elevated. Clypeus trapezoid, longer than broad, alutaceous, with a few setae scattered all around; ventrally rounded, not emarginate, without median incision; anterior tentorial pit large, rounded, distinct; epistomal sulcus and clypeo-pleurostomal line impressed, distinct.Frons and interocellar area alutaceous, without setae; area under frontal ocellus impressed, alutaceous. Vertex, occiput, postocciput, postgena alutaceous; posterior tentorial pit large, ovate, area below impressed; occipital foramen less than 0.5× as long as height of smooth, matte postgenal bridge; hypostomal carina emarginate, continuing into postgenal sulci which diverge toward occipital foramen. Antenna as long as head+mesosoma, with 11 flagellomeres, scape shorter than pedicel, scape+pedicel longer than F1, pedicel 2.0× as long as broad, F1 1.2× as long as F2, F2–F4 nearly equal in length; F5 shorter than F4; F5–F10 equal in length; F11 slightly longer than F10; placodeal sensilla on F3–F11, absent on F1–F2.

Mesosoma slightly higher than long in lateral view, without setae. Pronotum alutaceous, without striae laterally; propleuron alutaceous. Mesoscutum smooth, glabrous, as long as broad (greatest width measured across mesoscutum level with base of tegulae). Notaulus, anterior parallel line, median mesoscutal line and parapsidal line absent; circumscutellar carina narrow but present. Transscutal articulation absent, mesoscutum fused with mesoscutellum; as a result of fusion of the mesoscutum and mesoscutellum, the boundary between these structures is not straight but slightly curved towards the mesoscutum; the mesoscutum is emarginate posterolaterally and slightly elevated above the dorsoaxillar area. Mesoscutellum rounded, as long as broad (broadest part at mid height); posteriorly rounded, uniformly smooth, glabrous, with very few short scattered white setae, slightly overhanging metanotum. Mesoscutellar foveae absent, mesoscutellum with semilunar impression anteriorly. Mesopleuron and mesopleural triangle uniformly alutaceous, without setae; dorsal and lateral axillar areas alutaceous, without setae; subaxillular bar smooth, glabrous, triangular, highest part at anterior end and gradually narrowing towards posterior end; most anterior end higher than height of metanotal trough; metapleural sulcus reaching mesopleuron slightly below half its height, delimiting broad smooth area along mesopleuron; upper part of sulcus distinct, delimiting a narrow area along mesopleuron. Metascutellum smooth, 3.0x as high as height of smooth, glabrous ventral impressed area; metanotal trough smooth, glabrous, without setae; propodeum smooth, glabrous; central propodeal area alutaceous, with delicate longitudinal interrupted rugae; lateral propodeal carinae absent; lateral propodeal area smooth, glabrous, without setae. Nucha short, smooth, with strong longitudinal sulci dorsally and laterally. Tarsal claws simple, without basal lobe.

Forewing longer than body, hyaline, margin with dense long cilia, veins light brown, radial cell open, 3.5× as long as broad; R1 and Rs reaching wing margin; areolet small, triangular, distinct, Rs+M indistinct, projection reaching basalis in the lower 1/3 of its height.

Metasoma as long as head+mesosoma, 2.0× as high as long; all terga weakly sclerotized, thus limits of terga hardly visible. 2nd metasomal tergum extending to half the length of metasoma in dorsal view, without setae; all terga smooth, glabrous, without micropunctures. Hypopygium without micropunctures, prominent part of ventral spine of hypopygium short, as long as broad in ventral view, with a few long setae ventrally. Body length 1.0– 1.2 mm (n = 6).

Male ( Figs 137–141 , 148 ). Similar to female but body light brown, mandibles, palpi, antenna, legs yellow. Antenna nearly as long as body, ocelli at least 2.0× bigger than in female; forewing longer than body, 2nd metasomal tergum in the form of a narrow long petiole; metasoma shorter than mesosoma. Antenna with 12 flagellomeres, scape shorter than pedicel, scape+pedicel nearly as long as F1, pedicel 1.8× as long as broad, F1=F2, F2=F3=F4; F5 shorter than F4; F5=F6, F7–F10 equal in length; F12 slightly longer than F11; placodeal sensilla on F1–F12. Body length 0.8–1.0 mm (n = 4).

Gall. Sexual generation minute (approximately 1mm long), ovoid, seed-like integral leaf galls, smooth and only covered with normal leaf pubescence ( Fig. 150 ). Galls are visible and project slightly from both upper and lower leaf surfaces, and often but not always occur alongside major leaf veins. Galls appear reddish-brown from above and paler tan from below. Exit holes of adult insects generally occur on the underside of the leaf.

Biology. See Bassett (1881b), Beutenmueller (1910), and Weld (1926) for the biology of the asexual generation. Asexual galls ( Fig. 149 ) have been recorded on leaves of Q. bicolor and Q. macrocarpa . Galls become apparent in August as small depressions filled with loose, pale wool on the underside of new, terminal, long shoot leaves. Multiple galls often co-occur on a single leaf, which causes the leaf to curl, and galls tend to be found on stumps or damaged trees bearing vigorous, long late-season shoots. Adult females of the asexual generation emerge the spring following gall induction, from mid-April to late May. Galls of the sexual generation first appeared in late May on Q. macrocarpa in Edmonton, and adults emerged in late July and early August.

Distribution. USA: from Virginia west to Illinois ( Burks 1979). Canada: Ontario ( Burks 1979), Manitoba. This species was only reared in sleeves in Edmonton, Alberta, and does not naturally occur on bur oak there.

Molecular taxonomy. Alternating generations were matched using DNA data, with five individuals (three asexual females, two sexual females) sequenced for both cytb and ITS2. Two cytb haplotypes were found across the five individuals, differing by 0.23% (GenBank accessions OM321641 – OM321645 ); ITS2 sequences were identical ( OM331830 – OM331834 ).

The distinctiveness of N.floccosus from its close relative N.quercusverrucarum was confirmed with both cytb and ITS2 data (GenBank accessions OM321650 – OM321651 and OM331839 – OM331840 for N. quercusverrucarum ). On average, cytb haplotypes differed between the two species by 5.20% (range 4.85–5.54%), while ITS2 sequences differed by 2.38% (with two indels). These values are consistent with those expected between distinct congeneric species.

Figures

FIGURES 121–126. Neuroterus floccosus (Bassett), asexual generation, female. 121–124, head: 121, frontal view, 122, dorsal view, 123, posterior view, 124, lateral view. 125, antenna. 126, pronotum and propleuron, frontal view.

FIGURES 127–131. Neuroterus floccosus (Bassett), asexual generation, female. 127, mesosoma, lateral view. 128–129, mesosoma, dorsal view. 130, metascutellum and propodeum, posterodorsal view. 131, metasoma, lateral view.

FIGURES 132–141. Neuroterus floccosus (Bassett), sexual generation. 132–135, head, female: 132, frontal view, 133, dorsal view, 134, posterior view, 135, lateral view. 136, antenna, female. 137–140, head, male: 137, frontal view, 138, dorsal view, 139, posterior view, 140, lateral view. 141, antenna, male.

FIGURES 142–146. Neuroterus floccosus (Bassett), sexual generation, female. 142, pronotum and propleuron, frontal view. 143, mesosoma, lateral view. 144, mesosoma, dorsal view. 145, mesoscutellum, dorsal view. 146, metascutellum and propodeum, posterodorsal view.

FIGURES 147–150. Neuroterus floccosus (Bassett). 147–148, sexual generation, metasoma, lateral view: 147, female, 148, male. 149, asexual gall. 150, sexual gall.