Melikaiella tumifica ( Osten Sacken, 1865 )

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 : 39-41

Melikaiella tumifica ( Osten Sacken, 1865) , asexual generation

Figs 114–118 , 120

Synonyms: Cynips tumifica Osten Sacken (1865: 356) , female, male, gall. Andricus (Callirhytis) tumifica combination by Mayr (1881); Andricus (Callirhytis) tumificus corrected spelling by Dalla Torre (1893); Callirhytis tumifica combination by Dalla Torre & Kieffer (1910); Melikaiella tumifica combination by Pujade-Villar et al. (2014).

Material examined: 15 asexual females labelled as “ Germany, Baden-Württemberg, Schwetzinger Hardt, 10km SW of Heidelberg, ex acorns on Q. rubra , coll. R. Beiderbeck , 2014.10.01, emerge 2017.03.22 ”. Three asexual females have been deposited at the USNM, 12 females at the PHDNRL.

Diagnosis. Three Melikaiella species from eastern North America are known only from their asexual generations: M. fructuosa (Weld, 1922) , M. fructicola ( Ashmead, 1896) , and M. corrugis (Bassett, 1881) , all of which produce galls in acorns of red oaks ( Pujade-Villar et al. 2014). In M. fructuosa the female antenna has 10 flagellomeres and is shorter than in M. tumifica , reaching at most the level of the tegulae. Melikaiella tumifica adults most closely resemble those of M. fructicola and M. corrugis . However, in M. fructicola and M. corrugis the mesoscutum is uniformly dull rugose in between and on either side of the notauli, mesoscutellar foveae without subparallel distinct longitudinal rugae while in asexual females of M. tumifica the mesoscutum is dull rugose between the notauli and delicately reticulate on either side of the notauli, mesoscutellar foveae distinctly divided by a central elevated carina and the bottom of foveae has strong longitudinal rugae.

Description. Asexual female ( Figs 114–118 ). Head and antenna rusty brown, except dark brown to black frons and interocellar area, mouthparts light brown; mesoscutellum, metascutellum, propodeum dark brown to black, legs rusty brown, metasoma dark brown.

Head reticulate, with sparse white setae, transverse, 1.3× as broad as high and broader than mesosoma in frontal view, 2.5× as broad as long in dorsal view. Gena reticulate, broadened behind eye in frontal view, as broad as transverse diameter of eye in lateral view. Malar space with malar sulcus and multiple delicate parallel striae on both sides of sulcus, radiating from clypeus and reaching eye; eye 2.2× as high as height of malar space. Inner margins of eyes diverging slightly ventrally. POL 1.4× as long as OOL; OOL 2.7× as long as diameter of lateral ocellus and 1.8× as long as LOL; all ocelli rounded, of same size. Antennal toruli in the ventral half of head height. Transfacial distance 1.1× as long as height of eye; diameter of antennal torulus 1.2× as long as distance between them, distance between torulus and eye 1.7× as long as diameter of torulus. Lower face reticulate, with white setae, without striae; median area delicately coriaceous, slightly elevated. Clypeus quadrangular, slightly broader than high, smooth, glabrous, with dense long white setae, ventrally slightly emarginate, without median incision; anterior tentorial pit large, rounded, epistomal sulcus and clypeo-pleurostomal line broad, well impressed. Frons reticulate, area under central ocellus and interocellar area coriaceous. Vertex uniformly reticulate, occiput with delicate transverse parallel rugae; postocciput reticulate, glabrous; postgena reticulate, with white setae; posterior tentorial pit large, ovate, area below impressed; occipital foramen higher than height of postgenal bridge; hypostomal carina emarginate, continuing into postgenal sulci which diverge strongly toward occipital foramen, postgenal bridge anteriorly broader than high.Antenna shorter than head+ mesosoma, with 12 flagellomeres, pedicel slightly longer than broad, F1 2.2× as long as pedicel and 1.4x as long as F2, F2 slightly longer than F3, subsequent flagellomeres gradually shorter until F10, F11 2.2× as long as F10 (in some specimens a suture visible so antenna has 13 flagellomeres), placodeal sensilla on F5–F12.

Mesosoma slightly longer than high. Pronotum reticulate with uniformly distributed parallel rugae; propleuron smooth, glabrous. Mesoscutum uniformly rugose between notauli, reticulate on outer side of notaulus, without setae; slightly longer than broad (greatest width measured across mesoscutum level with base of tegulae). Notaulus complete, deep, broad; bottom smooth, glabrous, with transverse rugae; posteriorly slightly broader and slightly converging; anterior parallel line impressed in anterior 1/3 of mesoscutum length; median mesoscutal line in the form of a short impression; parapsidal line distinct, broad, delimited by smooth glabrous area, extending to 2/3 of mesoscutum length; circumscutellar carina broad, smooth, foveolate. Mesoscutellum elongated, slightly longer than broad, trapezoid, posteriorly rounded, uniformly dull rugose, overhanging metanotum. Mesoscutellar foveae separated by narrow elevated rugose central area, transversely ovate, 2.0× as broad as high; bottom smooth, glabrous, with strong longitudinal parallel rugae. Mesopleuron uniformly reticulate; mesopleural triangle rugose, with irregular striae; dorsal and lateral axillar areas reticulate, with a few white short setae; subaxillular bar smooth, glabrous, at posterior end as high as height of metanotal trough; metapleural sulcus reaching mesopleuron in upper 1/3 of its height, upper part of sulcus distinct. Metascutellum rugose, 3.0x as high as height of smooth, glabrous ventral impressed area; metanotal trough smooth, glabrous, with strong longitudinal parallel rugae; central propodeal area smooth, glabrous, with strong irregular rugae; lateral propodeal carinae strong, nearly parallel; lateral propodeal area smooth, glabrous, with strong irregular rugae. Nucha with strong sulci dorsally and laterally. Coxae reticulate, rest of legs smooth, glabrous; tarsal claws simple, without basal lobe.

Forewing longer than body, hyaline, margin without cilia, veins dark brown, radial cell open, 2.6× as long as broad; R1 and Rs reaching wing margin; areolet absent, Rs+M distinct along entire length, reaching basalis slightly above its mid height.

Metasoma longer than head+mesosoma, longer than high in lateral view; 2nd metasomal tergum extending to 1/3 length of metasoma in dorsal view, without setae anterolaterally, microreticulate in posterior 1/3; all subsequent terga microreticulate, glabrous. Prominent part of ventral spine of hypopygium slightly longer than broad in ventral view, narrowing towards apex, with short setae ventrally which do not extend beyond apex of spine. Body length 3.1–3.3 mm (n = 5).

Gall. Sexual generation gall ( Fig. 119 ) is a large, multilocular thickening of the leaf midrib/petiole. Asexual galls ( Fig. 120 ) are in acorns ( Beiderbeck & Nicholls 2014). The acorns are stunted, smaller than a non-infected acorn, and contain up to 6–7 cryptic larval chambers; the cotyledons are brown or used up by the larvae ( Beiderbeck & Nicholls 2014).

Biology. See Beiderbeck (2012), Beiderbeck & Nicholls (2014), and Pujade-Villar et al. (2014) for the biology of this species. The sexual generation develops on Q. rubra and Q. velutina ; the asexual only known so far from Q. rubra . Sexual generation leaf galls develop in early spring; adults emerge in May-June. Asexual acorn galls were found in October - November, maturing in November. Adults overwinter in galls and emerge in the following spring.

Distribution. USA: New York, Virginia, North Carolina, Illinois, Iowa ( Burks 1979).Also an introduced species in Germany (Heidelberg) on introduced Q. rubra ( Beiderbeck 2012, Beiderbeck & Nicholls 2014).

Molecular taxonomy. Alternate generations (using larvae of the asexual generation) were matched with sequence data by Beiderbeck & Nicholls (2014); here we supplement those data with additional sequences from sexual and asexual adults. In total, nine individuals (four asexual females, two sexual females, three sexual males) were sequenced for cytb and seven individuals (four asexual females, two sexual females, one sexual male) were sequenced for ITS2; these individuals were sourced from an introduced population in Germany as well as a nativerange population in North Carolina, USA. Cytb sequences were on average 0.18% divergent (range 0–0.46%; GenBank accessions MG 821060 , MW 326694 , OM 321634 – OM 321640 ) ; ITS2 sequences were 0–0.20% divergent ( OM 331823 – OM 331829 ) .

Comments. The genus Melikaiella Pujade-Villar, 2014 ( Pujade-Villar et al. 2014) is allied to “true” Callirhytis from the Western Palaearctic, or as previously called, Callirhytis ‘sensu stricto’ ( Pujade-Villar et al. 2012a). It thus makes good sense that their asexual generations develop in cryptic galls inside acorns, as is also the case for Callirhytis sensu stricto. Melikaiella was described with three new species from Mexico: M. amphibolensis Pujade-Villar, 2014 , M. bicolor Pujade-Villar, 2014 and M. reticulata Pujade-Villar, 2014 ; and one from the USA, M. ostensackeni Pujade-Villar, 2014 . The species Callirhytis sonorae Weld, 1944 from Mexico, C. corrugis , C. flora Weld, 1922 , C. fructicola , C. fructuosa , C. lupana Weld, 1944 and C. tumifica were also transferred to Melikaiella , and Callirhytis petrosa Weld, 1922 was synonymized to Melikaiella corrugis ( Pujade-Villar et al. 2014) . The species status of Cynips papula Bassett, 1881 from the USA, an earlier synonym of Callirhytis quercusmodesta ( Osten Sacken, 1861) , was restored and this species was also transferred to Melikaiella , under the new name combination M. papula ( Pujade-Villar et al. 2014) . Subsequently, Medianero & Nieves-Aldrey (2014) described the species Callirhytis cameroni from Panama, and although they mentioned that it most likely belonged to the genus Melikaiella , it was not formally transferred. Thus, the number of species in this genus is currently 12.

Figures

FIGURES 114–118. Melikaiella tumifica (Osten Sacken), asexual generation, female. 114, general habitus, lateral view. 115, head, frontal view. 116, propodeum, dorsal view. 117–118, head and mesosoma: 117, dorsolateral view, 118, dorsal view.

FIGURES 119–120. Melikaiella tumifica (Osten Sacken). 119, sexual gall. 120, asexual gall.