Druon ignotum ( Bassett, 1881 ) Cuesta-Porta & Melika & Nicholls & Stone & Pujade-Villar, 2022

Cuesta-Porta, Victor, Melika, George, Nicholls, James A., Stone, Graham N. & Pujade-Villar, Juli, 2022, Re-establishment of the Nearctic oak cynipid gall wasp genus Druon Kinsey, 1937 (Hymenoptera: Cynipidae: Cynipini), with description of five new species, Zootaxa 5132 (1), pp. 1-92 : 30-37

Druon ignotum ( Bassett, 1881) , comb. nov.

Figs. 69–100

Cynips ignota Bassett, 1881: 106 , female, gall.

Andricus ignota (Bassett) : Ashmead, 1885: 295.

Dryophanta ignota (Bassett) : Ashmead, 1887: 127.

Diplolepis ignota (Bassett) : Dalla Torre & Kieffer, 1910: 360. [NOT Diplolepis ignota Osten Sacken, 1863 ] Rhodites ignota (Bassett) : Dalla Torre, 1893: 127. [NOT Andricus ignota Bassett, 1900 (junior homonym).] Diplolepis ignota (Bassett) : Weld, 1926: 26.

Andricus ignotus (Bassett) : Weld, 1951: 634.

Type examined. Cotype asexual females: 9 pins with red label “Type”, printed “Waterbury, Ct. H. F. Bassett Coll.”; two pins with Bassett handwritten label “ Dryophanta ignota B. Type” deposited in AMNH, NYC; examined by GM. A type female, No. 10448 , deposited in the Entomology Type Collection at the Academy of Natural Sciences of Philadelphia , was not examined by the authors .

Additional material examined. Asexual generation. Five females: 2 females labelled as “ Canada, Alberta, Edmonton, University of Alberta, University Hall, 53.52428°N, - 113.52601°W, GPS ± 10m, galls coll. 13.ix.2004 ex Quercus macrocarpa, S. Digweed , reared 7–23.iv.2005 ”, determined originally as Andricus ignota asexual generation females by S. Digweed 2005; 3 females labelled as “ Canada, Manitoba, Winnipeg, Living Prairie Museum, 49.88765°N, - 97.2722°W, GPS ± 10m, galls coll. 31.viii.2005 ex Quercus macrocarpa, S. Digweed , reared 13– 29.iv.2006 ”, determined originally as Andricus ignota asexual generation females by S. Digweed 2006. Sexual generation. 4 sexual females and a dozen males labelled as “ Canada, Alberta, Bruderheim, 53.80751°N, - 112.92553°W, aspirated 12.vi.2007 ex Quercus macrocarpa, S. Digweed ”, determined originally as Andricus ignota sexual generation females by S. Digweed 2007. Specimens have been deposited at the PHDNRL and Royal Alberta Museum.

Diagnosis. The asexual form of this species belongs to the group of Druon species in which the front of the head is rusty brown and the posterior part of the head and mesosoma are dark brown to black ( Figs. 69, 72 ). The most similar species is D. fullawayi , but D. ignotum differs in having the mesoscutellar fovea coriaceous, not separated by central carina ( Fig. 77 ), and prominent part of ventral spine of hypopygium slightly longer than broad in ventral view ( D. fullawayi has the mesoscutellar foveae smooth, glabrous, separated by central carina ( Fig. 28 ), and long prominent part of ventral spine of hypopygium). The sexual generation of D. ignotum induces a bud gall on Q. macrocarpa , as yet recorded only in Canada ( Digweed 2010). The galls of sexual generation D. ignotum comprise integral cells that develop within the buds and young growing shoots, causing little or no externally visible deformity or damage ( Fig. 75 ); in contrast, all known the sexual generations of Nearctic Andricus species induce clearly visible bud galls.

Redescription. Asexual female ( Figs. 69–79 ). Head, mesosoma, metasoma chestnut brown; head and antenna slightly paler than mesosoma; clypeus, mandibles and palpi light brown, paler than rest of head; legs light brown, with darker coxae.

Head alutaceous, sides of frons delicately coriaceous, with sparse setae, denser on lower face, transverse, slightly broader than high and slightly broader than mesosoma in frontal view; 2.6× as broad as long in dorsal view. Gena alutaceous, strongly broadened behind eye in frontal view, narrower than transverse diameter of eye in lateral view. Malar space alutaceous, with numerous delicate striae radiating from clypeus and reaching eye; malar sulcus absent; eye 3.0x as high as length of malar space. Inner margins of eyes parallel, with row of white setae along inner margin of eye. POL 3.3× as long as OOL, OOL slightly shorter than diameter of lateral ocellus and slightly shorter than LOL, all ocelli ovate, of same size. Transfacial distance as long as height of eye; toruli located in the upper half of head and frons shorter than height of lower face, diameter of antennal torulus 1.2× as long as distance between them, distance between torulus and eye 1.2× as long as diameter of torulus; lower face alutaceous, glabrous, with white setae, without striae; slightly elevated median area alutaceous, without setae. Clypeus ovate, slightly broader than high, alutaceous, with long setae along ventral edge; ventrally rounded, not emarginate and without median incision; anterior tentorial pit large, rounded, distinct, epistomal sulcus distinct, clypeo-pleurostomal line well impressed. Frons uniformly alutaceous, without striae and setae, interocellar area alutaceous. Vertex, occiput, postocciput alutaceous; postgena smooth, with numerous setae; posterior tentorial pit large, elongated, area below impressed; occipital foramen slightly shorter than height of postgenal bridge; hypostomal carina emarginate, continuing into postgenal sulci which diverge toward occipital foramen, postgenal bridge anteriorly broader than occipital foramen. Antenna longer than head+mesosoma, with 11 flagellomeres, scape+pedicel longer than F1; pedicel longer than broad; F1 1.9× as long as pedicel and 1.2× as long as F2, F2 slightly longer than F3, F3 slightly longer than F4, F4=F5=F6, F7 till F10 equal in length; F11 longer than F10; placodeal sensilla on F6–F11, absent on F1–F5.

Mesosoma 1.2× as long as high, with a few white setae. Pronotum smooth, glabrous, with numerous delicate parallel striae extending across entire lateral length of pronotum; foveolate along anterior rim. Propleuron delicately smooth, glabrous. Mesoscutum uniformly and entirely alutaceous, slightly longer than broad (greatest width measured across mesoscutum level with base of tegulae). Notaulus complete, posteriorly broader and strongly converging; at most posterior end the distance between notauli shorter than distance between notaulus and side of mesoscutum; anterior parallel line visible at the most anterior end of mesoscutum, extending to 1/7–1/8 of mesoscutum length in the form of narrow impressed stripes; parapsidal line indistinct; median mesoscutal line absent; circumscutellar carina broad, reaching notaulus; mesoscutum with longitudinal impression medially, starting at anterior end and extending to 4/5 of mesoscutum length; parascutal carina reaching notaulus. Mesoscutellum ovate, longer than broad, broadest part in posterior 1/3 of mesoscutellum; disk of mesoscutellum delicately rugose to coriaceous in midpart and dull rugose laterally and posteriorly, overhanging metanotum, with a few sparse long setae; circumscutellar carina present. Mesoscutellar foveae finely rugose, indistinctly separated; mesoscutellum anteriorly (along mesoscutum) slightly impressed compared to mesoscutellar disc; longitudinal impression smooth, glabrous with some delicate sub-parallel striae radiating from disc and reaching mesoscutum; elevated central carina absent. Mesopleuron with delicate interrupted parallel striae, which are absent along posterior edge of speculum and in the most anteroventral part; setae along ventral edge. Mesopleural triangle smooth, glabrous, with a few strong irregular striae and long white setae; dorsal and lateral axillar areas alutaceous, glabrous, with a few setae; axillula with delicate parallel longitudinal striae; subaxillular bar smooth, glabrous, triangulate, at posterior end as high as height of metanotal trough; metapleural sulcus reaching mesopleuron below half of its height, delimiting broad smooth, wrinkled, glabrous area; upper part of sulcus indistinct, separating smooth, glabrous area, with some setae. Metascutellum rugose, slightly narrower than height of smooth, glabrous ventral impressed area; metanotal trough smooth, glabrous, with irregular rugae, without setae; central propodeal area smooth, glabrous, with irregular interrupted rugae; lateral propodeal carinae strong, distinct, bent outwards in posterior 1/3; lateral propodeal area smooth, glabrous, with scattered long white setae, with rounded bump at the base of each seta. Nucha with strong rugae dorsally and laterally. Tarsal claws with acute basal lobe.

Fore wing longer than body, hyaline, with short dense cilia on margin, veins brown, radial cell open, 4.1× as long as broad; Rs and R1 nearly reaching wing margin; areolet small, triangular, closed, indistinct. Rs+M pale brown along 2/3 of its length, its projection reaching basalis at half of its height.

Metasoma longer than head+mesosoma, as long as high in lateral view; all metasomal terga and hypopygium smooth, glabrous; second metasomal tergum extending to nearly half-length of metasoma in dorsal view, with white setae anterolaterally and laterally, without micropunctures; metasomal tergum 3 with band of micropunctures posteriorly; all subsequent terga entirely delicately micropunctate. Hypopygium without micropunctures, prominent part of ventral spine of hypopygium slightly longer than broad in ventral view, with white setae ventrally. Body length 2.4–2.7 mm (n = 4).

The following is the first description of the sexual generation.

Sexual female ( Figs. 80–84 ; 91–95 ). Head, mesosoma, metasoma dark brown to chestnut; antenna pale brown; legs pale brown with dark brown coxae; clypeus, mouthparts yellowish.

Head alutaceous, with sparse white setae on lower face, 1.2× as broad as high and slightly broader than mesosoma in frontal view, 2.2× as broad as long in dorsal view. Gena alutaceous, broadened behind eye in frontal view, as broad as transverse diameter of eye in lateral view. Malar space alutaceous, glabrous, with short delicate striae radiating from clypeus but not reaching eye, malar sulcus absent; eye 3.8× as high as length of malar space. Inner margins of eyes parallel. POL 3.0x as long as OOL, OOL as long as diameter of lateral ocellus and shorter than LOL, all ocelli ovate, of same size. Transfacial distance only slightly shorter than height of eye; diameter of antennal torulus 2.0× as long as distance between them, distance between torulus and eye as long as diameter of torulus; lower face alutaceous, glabrous, with white setae, without striae; slightly elevated median area alutaceous, glabrous, with a few setae. Clypeus slightly broader than high, smooth, glabrous, with long setae; ventrally rounded, not emarginate and without median incision; anterior tentorial pit large, rounded, distinct, epistomal sulcus and clypeo-pleurostomal line distinct, well-impressed. Frons and interocellar area uniformly alutaceous, without striae or setae. Vertex, occiput, postocciput, postgena alutaceous; posterior tentorial pit large, ovate, area below impressed; occipital foramen higher than height of postgenal bridge; hypostomal carina emarginate, continuing into postgenal sulci which are not united and diverge strongly toward occipital foramen, postgenal bridge anteriorly as broad as occipital foramen. Antenna longer than head+mesosoma, with 12 flagellomeres (sometimes suture between F11 and F12 indistinct), pedicel semiglobular, F1 2.0× as long as pedicel and 1.2× as long as F2; F2=F3; F3 slightly longer than F4, F5=F6, F7=F8 and slightly shorter than F5 and F6; subsequent flagellomeres nearly equal in length; placodeal sensilla on F5–F11.

Mesosoma longer than high, with sparse white setae. Pronotum smooth, glabrous, with sparse setae, with numerous parallel delicate striae laterally; propleuron smooth, glabrous. Mesoscutum uniformly alutaceous, with sparse white setae, longer than broad (greatest width measured across mesoscutum level with base of tegulae). Notaulus complete, deep, broad, notaulus furrow smooth; anterior parallel line indistinct, marked with smooth line; parapsidal line distinct, marked with smooth line; median mesoscutal line absent; circumscutellar carina broad, reaching notaulus. Mesoscutellum ovate, longer than broad, with nearly parallel lateral sides, disk of mesoscutellum alutaceous to delicately coriaceous, glabrous; laterally and posteriorly with net of strong irregular rugae, posteriorly rounded; circumscutellar carina present; not overhanging metanotum. Mesoscutellar foveae ovate, only weakly impressed, indistinctly separated from disk of mesoscutellum, smooth, glabrous, separated by elevated alutaceous central carina. Mesopleuron alutaceous, with very indistinct delicate transverse subparallel striae, speculum alutaceous, glabrous; mesopleural triangle smooth, glabrous, with sparse white setae and transverse delicate striae, extending across entire width of mesopleural triangle; dorsal and lateral axillar areas smooth, glabrous, with a few white setae; subaxillular bar smooth, glabrous, triangulate, gradually higher towards posterior end, at most posterior end as high as height of metanotal trough; metapleural sulcus reaching mesopleuron at half of its height, delimiting delicately coriaceous area, lower and upper parts of sulcus distinct. Metascutellum smooth, glabrous, as high as height of smooth, glabrous ventral impressed area; metanotal trough smooth, glabrous; central propodeal area smooth, glabrous, with some longitudinal rugae which do not reach anterior edge of propodeum; lateral propodeal carinae narrow, indistinctly elevated in anterior part of propodeum, bent outwards in mid-height; lateral propodeal area smooth, glabrous, with white setae. Nucha with parallel sulci dorsally and laterally. Tarsal claws with basal lobe.

Fore wing longer than body, hyaline, with cilia on margin, veins light brown, radial cell open, 4.4× as long as broad; R1and Rs not reaching wing margin; areolet small, distinct. Rs+M narrow, inconspicuous, reaching basalis slightly below its mid height.

Metasoma slightly longer than head+mesosoma, longer than high in lateral view; second metasomal tergum extending to 1/3 length of metasoma in dorsal view, with white setae laterally; all terga smooth, glabrous, without micropunctures. Hypopygium without micropunctures, prominent part of ventral spine of hypopygium short, slightly longer than broad in ventral view, with a few short setae ventrally which do not extend beyond apex of spine. Body length 1.8–2.0 mm (n = 4).

Male ( Figs. 85–89 ; 96–98 ). Similar to female; head, mesosoma, metasoma dark brown to black; mandibles and mouthparts pale brown, antenna brown; legs pale brown with darker coxae and femora. Ocelli much bigger than in female; POL 5.6× as long as OOL, OOL much shorter than diameter of lateral ocellus and more than 2.0× as short as LOL, all ocelli ovate, of same size, big. Transfacial distance shorter, 0.75× as long as height of eye. Antenna as long as body, with 14 flagellomeres; scape+pedicel as long as F1; F1 curved, slightly broadened apically. Placodeal sensilla on all flagellomeres. Notaulus complete, mesoscutellum overhanging metanotum. Propodeal carinae incomplete or indistinct in most anterior part of propodeum; second metasomal tergum in the form of a long narrow petiole, metasomal tergum 3 occupying half-length of metasoma. Body length 1.9–2.1 mm (n = 4).

Gall. Asexual galls ( Fig. 99 ). Small (2–3 mm long) brown, thin-walled and gregarious ovoid galls firmly attached to the underside of the leaf midrib in clusters of up to 30 or more. The entire cluster is covered with a dense coating of long woolly hairs, which is initially cream-coloured or pink but fades to brown over the winter, and sometimes wears away. Sexual galls ( Fig. 100 ) occur singly or in groups in buds of Q. macrocarpa . They are apparently undifferentiated ovoid cells approximately 2 mm long, integral within buds and young growing shoots, and cause little or no visible external deformity or damage. Galls are generally only detectable by the emergence holes left by the adult insects.

Biology. Alternate asexual and sexual generations are known (see comments). See Bassett (1881) and Weld (1926) for the biology of the asexual generation. Asexual galls have been recorded on leaves of Q. bicolor and Q. macrocarpa (Section Quercus , Series Prinoideae), mature in October–November, adult females emerge very early the following spring (late March to late April in Edmonton, Alberta, Canada), often on the first warm days after accumulated snow has melted and fallen leaves bearing galls are exposed. Emerged females fly up to buds and oviposit. The sexual generation adults emerged in Edmonton in early June. Females were observed ovipositing multiply along the midrib on the upper leaf surface in a zipper-like pattern, suggesting that asexual females in a given gall cluster are sisters. Galls of the asexual generation first became apparent on leaves in Edmonton in late July.

Distribution. USA: Massachusetts, Connecticut, Illinois, Minnesota ( Burks 1979), Nebraska ( Weld 1926); Canada: Alberta, Manitoba.

Comments. Alternate sexual and asexual generations were proposed but not described by Digweed (2010: 216) and are hereby confirmed using DNA data. Two sexual generation and two asexual generation individuals were sequenced for cytb and ITS2, with between 0 and 0.92% divergence apparent for cytb (GenBank MW388886 , MZ935704 – MZ935706 ) and ITS2 alleles that were either identical or differed only in a single T insertion in one sequence ( MZ927174 – MZ927177 ).

Figures

FIGURES 69–74. Druon ignotum, comb. nov., asexual female. 69–72, head: 69, frontal view, 70, dorsal view, 71, lateral view, 72, posterior view. 73, antenna. 74, mesosoma and propleura, frontal view.

FIGURES 75–79. Druon ignotum, comb. nov., asexual female. 75, mesosoma, lateral view. 76, mesoscutum and mesoscutellum, dorsal view. 77, mesoscutellum, dorsal view. 78, metascutellum and propodeum, posterodorsal view. 79, metasoma, lateral view.

FIGURES 80–89. Druon ignotum, comb. nov., sexual generation. 80–84, female: 80–83, head: 80, frontal view, 81, dorsal view, 82, lateral view, 83, posterior view; 84, antenna. 85–89, male: 85–88, head: 85, frontal view, 86, dorsal view, 87, posterior view, 88, lateral view. 89, antenna.

FIGURES 90–94. Druon ignotum, comb. nov., sexual generation, female. 90, mesosoma and propleura, frontal view. 91, mesosoma, lateral view. 92, mesoscutum, dorsal view. 93, metascutellum, dorsal view, 94, metascutellum and propodeum, posterodorsal view.

FIGURES 95–98. Druon ignotum, comb. nov., sexual generation. 95, metasoma, lateral view, female. 96–98, male: 96, mesoscutum and mesoscutellum, dorsal view, 97, metascutellum and propodeum, posterodorsal view, 98, mesosoma and metasoma, lateral view.

FIGURES 99–100. Druon ignotum, comb. nov., galls: 74, asexual galls, 75, sexual galls.

FIGURES 26–29. Druon fullawayi, comb. nov., asexual female. 26, mesosoma, lateral view. 27, mesoscutum, dorsal view. 28, mesoscutellum, dorsal view. 29, metascutellum and propodeum, posterodorsal view.