Phylloteras poculum ( Osten Sacken, 1862 )

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 : 62-67

Phylloteras poculum ( Osten Sacken, 1862) , sexual generation

Figs 206–223 , 225

Synonyms: Cecidomyia poculum Osten Sacken (1862: 201) , galls. Xystoteras poculum combination and description of adult females by Weld (1922a: 7); Phylloteras poculum combination by Lyon (1993: 133).

Material examined: Five males and five females of the sexual generation, labelled as “ CANADA: Alberta, Edmonton, Brennan Crescent, 53.51746°N, - 113.682957°W, Google Maps, bud/shoot/ament galls collected 21.v.2018 ex Quercus macrocarpa, S. Digweed , reared 24-30.v.2018 ”. Specimens have been deposited at the USNM, PHDNRL, RAM .

Diagnosis. This is the first sexual generation to be described for Phylloteras . Lyon (1993) gave a key to adults and galls of the asexual generation.

Description. Asexual female ( Fig. 205 ). Apterous, ant-like. Head, antenna, mesosoma, legs entirely black; metasoma dark brown.

Sexual female ( Figs 206–210 , 216–221 ). Head and mesosoma black, metasoma dark brown to black; mandibles dark brown, palpi yellow; scape, pedicel, F1 and F2 yellow, all subsequent flagellomeres uniformly dark brown; legs yellow with brown coxae.

Head alutaceous, with sparse white setae on lower face; nearly rounded, only 1.2× as broad as high and broader than mesosoma in frontal view, 2.0× as broad as long in dorsal view. Gena alutaceous, not broadened behind eye in frontal view, 1/3 width of transverse diameter of eye in lateral view. Malar space alutaceous, without malar sulcus or striae; eye 3.9× as high as height of malar space. Inner margins of eyes slightly converging ventrally. POL 2.0× as long as OOL; OOL 1.3× as long as diameter of lateral ocellus and slightly shorter than LOL; all ocelli ovate, of same size. Transfacial distance as long as height of eye; diameter of antennal torulus slightly longer than distance between them, distance between torulus and eye as long as diameter of torulus. Lower face nearly as high as height of frons, alutaceous, without striae, with white scattered setae. Clypeus rounded, nearly as long as broad, alutaceous, with a few setae scattered all over; ventrally rounded, emarginate, without median incision; anterior tentorial pit small, indistinct; epistomal sulcus impressed, distinct; clypeo-pleurostomal line semi-lunar, impressed, distinct. Frons and interocellar area alutaceous, without setae. Vertex, occiput, postocciput, postgena alutaceous; posterior tentorial pit large, ovate, area below impressed; occipital foramen shorter than height of postgenal bridge; hypostomal carina emarginate, continuing into postgenal sulci which are widely separated and diverge toward occipital foramen, postgenal bridge only slightly broader than high anteriorly.Antenna longer than head+mesosoma, with 12 flagellomeres, scape slightly longer than pedicel; pedicel longer than broad, F1 1.4× as long as pedicel and as long as F2, F2 1.4× as long as F3, F3=F4, F5 to F11 equal in length; F12 longer than F11; placodeal sensilla on F3–F12, absent on F1–F2.

Mesosoma slightly longer than high. Pronotum dorsally alutaceous, with white setae along anterior rim in frontal view; smooth, matte laterally, with impressed foveolate sculpture along anterior edge; propleuron alutaceous, matte. Mesoscutum smooth, glabrous, with a few scattered setae only along sides; 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 but 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 longer than broad, ovate, posteriorly rounded, uniformly dull rugose, with more delicate coriaceous sculpture toward anterior end; strongly overhanging metanotum. Mesoscutellar foveae in the form of a narrow semilunar impression with smooth glabrous bottom, without central longitudinal carina or elevation. Mesopleuron, including speculum smooth, matte, with short delicate striae, together the striae form a line extending across mesopleuron from posteroventral to anterodorsal edges; mesopleural triangle smooth, matte; dorsal and lateral axillar areas smooth, matte, with a few setae; subaxillular bar smooth, glabrous, at posterior end as high as height of metanotal trough; metapleural sulcus reaching mesopleuron in upper 1/3, delimiting broad smooth and wrinkled area along mesopleuron; upper part of sulcus hardly traceable. Metascutellum narrow, smooth, as high as height of smooth, glabrous ventral impressed area; metanotal trough smooth, glabrous, without setae; propodeum smooth, glabrous; central propodeal area broad, smooth, matte, with a few irregular interrupted rugae; lateral propodeal carinae strong, elevated, bent outwards in posterior 1/3 of propodeum height; lateral propodeal area smooth, glabrous, without setae, with irregular short rugae, with dense long white setae in most lateroventral parts. Nucha short, with irregular rugae dorsally and laterally. Tarsal claws with acute basal lobe.

Forewing longer than body, hyaline, margin with long cilia, veins dark brown, radial cell open, 5.25× as long as broad; R1 and Rs reaching wing margin and extending along margin; areolet small, triangular, distinct; Rs+M dark brown, visible along 2/3 of its length, projection reaching basalis at its mid height.

Metasoma longer than head+mesosoma, slightly higher than long in lateral view; 2nd metasomal tergum extending to nearly 1/3 length of metasoma in lateral view, with a few setae anterolaterally; all terga smooth, matte, without micropunctures. Hypopygium without micropunctures, prominent part of ventral spine of hypopygium needle-like, 3.5× as long as broad in ventral view, with a few setae ventrally. Body length 1.8–1.9 mm (n = 3).

Male ( Figs 211–215 , 222–223 ). Similar to female, also in coloration, but head with larger eyes, interocellar area and ocelli strongly elevated; ocelli bigger than in female; antenna slightly longer than body, with 13 flagellomeres; scape short, as long as pedicel, pedicel slightly longer than broad; scape+pedicel slightly longer than F1, F1 slightly curved, not broadened apically, longer than F2; F2 longer than F3; F4 and F5 nearly equal in length, both shorter than F3; F5 twisted, curved, apically broader; F7–F12 with distinct long setae apically; F13 longer than F12; placodeal sensilla on all flagellomeres. Mesosoma and nucha slightly longer than in female; disc of mesoscutellum smooth, glabrous; metasoma as long as mesosoma; 2nd metasomal tergum extending to half the length of metasoma in dorsal view; all terga smooth, matte, without micropunctures. Body length 1.7 mm (n = 3).

Gall. Sexual galls ( Fig. 225 ) are exposed, thin-walled, seed-like, ovoid, brown chambers in buds, catkins, and proximal regions of immature leaf midribs and laminae. Sometimes with a sparse pubescence of fibrous, tan hairs; sometimes these hairs are more abundant as a distal tuft. Adults emerge through holes chewed in the distal half of galls. Aging galls can persist on buds and leaves into autumn. Galls of the asexual generation ( Fig. 224 ) on Q. alba are as described by Osten Sacken (1862) and Weld (1922a).

Biology. See Weld (1922a) for the biology of the asexual generation. Galls of the asexual generation became evident on bur oak leaves in Edmonton in July, and were fully mature in September, when many separate easily from the leaf lamina, falling to the ground. Galls are susceptible to drying, and rearing experience suggests that desiccated galls produce no emergents. Females of the asexual generation overwinter and pass the entire subsequent summer in their galls, emerging in late autumn and winter – generally from late October to December with a peak in mid-November, but when a large number of galls was reared over winter 2016-2017 in Edmonton, a small number of females emerged in all months from January through April 2017. Weld (1922a) reared adults in Evanston, Illinois, in March. The brachypterous females were observed in Edmonton to crawl up through any accumulated snowpack, climb bur oak stems, and oviposit in buds. Emergence and adult female activity appeared delayed in autumn during periods of warmer weather, and was observed during a period of sustained temperatures ranging from -10°C to -17°C during early January 2017 in Edmonton. Galls of the sexual generation became apparent in early May in Edmonton, with adults emerging from mid-May through mid-June.

This species has not been previously recorded from Q. macrocarpa ; earlier records are from Q. alba and Q. montana . Another congeneric species, Phylloteras volutellae ( Ashmead, 1897) , is also found on Q. macrocarpa .

Distribution. USA: Virginia, New York, Vermont, New Hampshire, Illinois, Missouri ( Burks 1979). Canada: Manitoba, Alberta.

Molecular taxonomy. Alternating generations were matched using DNA data, with six individuals (four asexual females, two sexual females) sequenced for both cytb and ITS2. Cytb sequences were on average 0.85% divergent (range 0–1.62%; GenBank accessions MZ 935719 , OK041500 , OM 321657 – OM 321660 ) . Two ITS2 alleles were observed that differed only by a 5bp indel ( OM 331845 – OM 331850 ) ; four Canadian samples (sexual and asexual females) shared the same ITS2 allele while the other allele was present in two North Carolina asexual females.

Figures

FIGURE 205. Phylloteras poculum (Osten Sacken), asexual female, general habitus.

FIGURES 206–215. Phylloteras poculum (Osten Sacken), sexual generation. 206–209, head, female: 206, frontal view, 207, dorsal view, 208, posterior view, 209, lateral view. 210, antenna, female. 211–214, head, male: 211, frontal view, 212, dorsal view, 213, posterior view, 214, lateral view. 215, antenna, male.

FIGURES 216–220. Phylloteras poculum (Osten Sacken), sexual generation, female. 216, pronotum and propleuron, frontal view. 217, mesosoma, lateral view. 218, mesoscutum, dorsal view. 219, mesoscutellum, dorsal view. 220, metascutellum and propodeum, posterodorsal view.

FIGURES 221–223. Phylloteras poculum (Osten Sacken), sexual generation. 221, metasoma, female, lateral view. 222–223, male: 222, mesosoma, dorsal view, 223, mesosoma and metasoma, lateral view.

FIGURES 224–225. Phylloteras poculum (Osten Sacken). 224, asexual gall. 225, sexual gall.