Acraspis quercushirta ( Bassett, 1864 )

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 : 8-12

Acraspis quercushirta ( Bassett, 1864) , sexual generation

Figs 1–11 , 13

Synonyms: Cynips quercus hirta Bassett (1864: 688) , females and galls. Cynips (Teras) hirta combination by Osten Sacken (1865: 333); Biorhiza hirta combination by Ashmead (1885: 296); Biorrhiza hirta combination and incorrect spelling by Dalla Torre (1893: 60); Philonix hirta combination by Smith (1900: 548); Phylonyx hirta combination and incorrect spelling by Smith (1910: 598); Trichoteras quercus-hirtum combination by Dalla Torre & Kieffer (1910: 404); Biorhiza (Xystoteras) hirta combination by Britton (1920: 319); Acraspis hirta combination by Weld (1922a: 10); Cynips (Acraspis) hirta var. hirta combination by Kinsey (1930: 426); Cynips (Acraspis) hirta combination by Kinsey (1936: 285); Acraspis quercushirta corrected spelling by Burks (1979: 1079).

Acraspis macrocarpae Bassett, 1890 . Philonix macrocarpae combination by Smith (1900: 548); Phylonyx macrocarpae combination by Smith (1910: 598); Acraspis macrocarpa incorrect spelling by Weld (1922a: 13). Syn. nov.

Acraspis undulata Gillette, 1893 . Synonymized by Beutenmueller (1907: 466).

Cynips (Acraspis) hirta var. macrescens Kinsey (1930: 423) , nom. nov. Cynips (Acraspis) macrescens combination by Kinsey (1936: 287). Declared “unnecessarily proposed” by Burks (1979: 1079).

Kinsey (1930, 1936) described seven additional species from the asexual generation within his “ hirta complex”: Cynips (Acraspis) obtrectans Kinsey, 1930 , Cynips (Acraspis) opima Kinsey, 1930 , and Cynips (Acraspis) scelesta Kinsey, 1930 , all from Q. macrocarpa ; and Cynips (Acraspis) packorum Kinsey, 1930 , Cynips (Acraspis) bandero Kinsey, 1936 , Cynips (Acraspis) hirtior Kinsey, 1936 , and Cynips (Acraspis) ulterior Kinsey, 1936 from Q. gambelii . Weld (1951) and Burks (1979) treated Acraspis bandero (Kinsey) , Acraspis hirtior (Kinsey) and Acraspis ulterior (Kinsey) as distinct valid species, while the rest were treated as varieties of A. quercushirta . We follow this treatment, thus Acraspis hirta var. obtrectans (Kinsey) , syn. nov., Acraspis hirta var. opima (Kinsey) , syn. nov., Acraspis hirta var. packorum (Kinsey) , syn. nov. and Acraspis hirta var. scelesta (Kinsey) , syn. nov. all are synonyms of A. quercushirta .

Material examined: Six sexual females labelled as “ Canada, Alberta, Edmonton, Royal Alberta Museum, 53.54218°N, - 113.54289°W, GPS ± 10m, S. Digweed, Collected 22.v.2005 ex Quercus macrocarpa, Reared 25.v.2005 ex gall of Acraspis macrocarpae ♂ ♀ ”, determined originally as Acraspis macrocarpae sexual generation females by S. Digweed 2005. Six sexual females have been deposited at the PHDNRL .

Diagnosis. Closely resembles A. villosa . In A. quercushirta the radial cell of the forewing 4.2× as long as broad; the eye 4.5× as high as length of malar space, inner margins of eyes slightly converge ventrally; POL 2.2× as long as OOL, OOL 1.2× as long as diameter of lateral ocellus. In A. villosa the radial cell of the forewing 5.0× as long as broad, the eye 2.5× as high as length of malar space, inner margins of eyes are parallel; POL 1.8× as long as OOL, OOL 1.75× as long as diameter of lateral ocellus.

Description. Sexual female ( Figs 1–11 ). Head, mesosoma, metasoma uniformly dark brown; antenna slightly lighter than body; mandibles, palpi maxillaris and labialis, legs light brown to yellowish.

Head alutaceous, with white setae, denser on lower face and postgena, with distinct rows of setae along inner margin of eye; rounded, 1.1× as broad as high and as broad as mesosoma in frontal view, 1.8× as broad as long from dorsal view. Gena alutaceous, not broadened behind eye in frontal view, narrower than transverse diameter of eye in lateral view. Malar space alutaceous, glabrous, with very delicate striae that radiate from clypeus and do not reach eye; eye 4.5× as high as length of malar space. Inner margins of eyes slightly converge ventrally. POL 2.2× as long as OOL, OOL 1.2× as long as diameter of lateral ocellus and slightly shorter than LOL, all ocelli small, ovate, of same size. Transfacial distance as great as height of eye; diameter of antennal torulus 1.3× as long as distance between them, distance between torulus and eye as long as diameter of torulus; lower face alutaceous, matte, slightly elevated median area alutaceous. Clypeus rounded, nearly as broad as high, alutaceous, matte, with a few long setae; ventrally rounded, slightly emarginate, without median incision; anterior tentorial pit small, rounded, epistomal sulcus distinct, clypeo-pleurostomal line well impressed. Frons and interocellar area uniformly alutaceous, without striae and setae. Vertex, occiput and postocciput alutaceous; postgena smooth, glabrous, with dense white setae; posterior tentorial pit small, rounded, area below impressed; occipital foramen as high as height of postgenal bridge; hypostomal carina emarginate, continuing into postgenal sulci which are not united and diverge toward occipital foramen, postgenal bridge anteriorly as broad as occipital foramen. Antenna longer than head+mesosoma, with 12 flagellomeres, pedicel slightly longer than broad, flagellomeres slightly broader towards apex; F1 2.4× as long as pedicel and 1.4× as long as F2; F2 slightly longer than F3; F3 1.2× as long as F4, F5 slightly longer than F6, all subsequent flagellomeres equal in length; placodeal sensilla on F2–F12, absent on F1.

Mesosoma 1.1× as long as high, with sparse white setae, except for dense setae on lateral propodeal area, mesopleural triangle and propleuron. Pronotum smooth, matte, with sparse setae, without striae laterally; propleuron alutaceous, matte. Mesoscutum smooth, glabrous, with sparse white setae along notauli, slightly longer than broad (greatest width measured across mesoscutum level with base of tegulae). Notaulus incomplete, extending to 2/3 of mesoscutum length, shallow, broad, bottom smooth, glabrous, posteriorly broader and slightly converging; anterior parallel line and median mesoscutal line absent; parapsidal line indistinct, in the form of an impressed line; circumscutellar carina narrow, distinct, reaching notaulus. Mesoscutellum ovate, slightly longer than broad, with semi-parallel sides, coriaceous, overhanging metanotum, posteriorly rounded; disk alutaceous with delicate rugae laterally and posteriorly. Mesoscutellar foveae absent, anterior part of mesoscutellum is not impressed, in the same plane as the mesoscutellar disk, alutaceous to smooth. Mesopleuron smooth, matte, setae only on posteroventral quarter of mesopleuron; mesopleural triangle delicately coriaceous, matte, with some delicate longitudinal parallel striae and a few setae; dorsal and lateral axillar areas smooth, glabrous, with dense setae; subaxillular bar smooth, glabrous, triangulate, gradually higher toward posterior end, at posterior end as high as height of metanotal trough; metapleural sulcus reaching mesopleuron slightly below half of its height, upper part of sulcus indistinct. Metascutellum coriaceous, as high as height of coriaceous ventral impressed area; metanotal trough smooth, matte, without setae; central propodeal area lyre-shaped, rugose, matte, with net of irregular rugae continuing onto nucha; lateral propodeal carinae bent slightly outwards in posterior 1/3, complete or incomplete, do not reaching anterior end of propodeum; lateral propodeal area coriaceous, matte, with long white setae. Nucha with net of irregular rugae dorsally and laterally. Tarsal claws with basal lobe.

Forewing longer than body, hyaline, with long dense cilia on margin, veins brown, radial cell open, 4.2× as long as broad; R1 and Rs reaching wing margin; areolet small, triangular, closed, distinct. Rs+M narrow, reaching basalis at mid height.

Metasoma as long as head+mesosoma, longer than high in lateral view; 2nd metasomal tergum extending to 1/3 length of metasoma in dorsal view, without setae or micropunctures; subsequent terga smooth, glabrous, without micropunctures. Hypopygium without micropunctures, prominent part of ventral spine of hypopygium longer than broad in ventral view, with a few short setae ventrally which extend beyond apex of spine. Body length 1.8–1.9 mm (n = 4).

Male. The male as in Acraspis villosa ; it is impossible to distinguish males of the two species using morphological characters (see male description for A. villosa ).

Gall ( Fig. 13 ). Sexual galls develop in the innermost scales in apical and lateral buds, a brittle, thin-walled, seed-like, sub-ovoid cell approximately 2 mm long, tan or orange-brown when mature, with faint longitudinal striations and sparse, pale hairs. Galls form in the basal portion of the scale and often leave the scale apex intact, which extends as a flat flap beyond the gall.

Biology. See Bassett (1864), Weld (1922a, 1926), and Kinsey (1930, 1936) for the biology of the asexual generation. Asexual generation galls ( Fig. 12 ) have been recorded on leaves of Q. chapmanii , Q. gambelii , Q. macrocarpa , Q. michauxii , and Q. montana . Adult females of the asexual generation emerged in Edmonton from late September to early November, with the peak occurring during the last half of October. Bassett (1864) noted that adult females of the asexual generation bore exit holes in their galls some time prior to emerging. This behaviour was observed in Edmonton as well, with females often remaining for days or weeks just inside emergence holes. Completion of emergence was often triggered by cooler temperatures. Leaves with galls have mostly fallen to the ground when the brachypterous females emerge in Edmonton, so they walk to a bur oak tree bole, climb it, and oviposit into bud scales, remaining active for up to 2–3 weeks, often at temperatures below freezing.

Galls of the sexual generation usually occur singly, but up to six galls were found around a single bud. Galls and inhabitants survived freezing in late April 2005 in Edmonton that destroyed new shoots on many bur oaks. Emergence typically occurs through holes chewed near gall apices. Empty galls can persist around bases of new shoots for weeks or months, but are easily detached as bud scales slough off during shoot maturation. Adults of the sexual generation emerged in Edmonton from late May to early June. Galls of the asexual generation appeared on leaves starting in late June or early July.

Distribution. USA: Connecticut south to Virginia, Illinois, Michigan, Texas, Utah ( Burks 1979), Colorado, New Mexico, Oklahoma ( Kinsey 1930). Canada: Alberta, Saskatchewan, Manitoba, Ontario, Quebec, New Brunswick. Probably everywhere east of the Rocky Mountains in the USA and Canada where white oaks occur ( Kinsey 1930) or have been introduced as urban trees (e.g., bur oak in Alberta).

Molecular taxonomy. Alternating generations were matched using DNA data, with four individuals (two asexual females, two sexual females) from Canadian Q. macrocarpa rearings sequenced for both cytb and ITS2. Cytb sequences were 0–0.23% divergent (GenBank accessions OM321608 – OM321610 , OM321612 ); ITS2 sequences were identical ( OM331800 – OM331802 , OM331805 ).

The conspecific status of A. macrocarpae and A. quercushirta was confirmed by comparing sequences from the four Canadian individuals (originally determined as A. macrocarpae ) with those from two south-eastern USA individuals (determined as A. quercushirta ; cytb: KX683594 , OM321611 ; ITS2: OM331803 – OM331804 ). Cytb haplotype divergence between the two regions averaged 2.08% (range 2.54–1.62%), with greater variation (3.23%) actually observed between the two USA haplotypes. ITS2 sequences were 0.38% different between Canadian and USA specimens, with four additional single base indels in polyA or polyT repeat units.

Figures

FIGURES 1–6. Acraspis quercushirta (Bassett), sexual female. 1–4, head: 1, frontal view, 2, dorsal view, 3, posterior view, 4, lateral view. 5, antenna. 6, pronotum and propleuron, frontal view.

FIGURES 7–11. Acraspis quercushirta (Bassett), sexual female. 7–8, mesosoma: 7, lateral view, 8, dorsal view. 9, metascutellum and propodeum, posterodorsal view. 10, forewing, part. 11, metasoma, lateral view.

FIGURES 12–13. Acraspis quercushirta (Bassett). 12, asexual gall. 13, sexual gall.