A new genus of oak gallwasps, Zapatella Pujade-Villar & Melika, gen. n., with a description of two new species from the Neotropics (Hymenoptera, Cynipidae, Cynipini)

Abstract A new genus of cynipid oak gallwasp, Zapatella Pujade-Villar & Melika, gen. n. (Hymenoptera: Cynipidae: Cynipini), with two new species, Zapatella grahami Pujade-Villar & Melika, sp. n. and Zapatella nievesaldreyi Melika & Pujade-Villar, sp. n., is described from the Neotropics. Zapatella grahami,known only from the sexual generation,induces galls in acorns of Quercus costaricensis and is currently known only from Costa Rica. Zapatella nievesaldreyi, known only from the asexual generation, induces inconspicuous galls in twigs of Quercus humboldtii, and is known only from Colombia. Diagnostic characters for both new species are given in detail. Five Nearctic species are transferred from Callirhytis to Zapatella: Zapatella cryptica (Weld), comb. n., Zapatella herberti (Weld), comb. n., Zapatella oblata (Weld), comb. n., Zapatella quercusmedullae (Ashmead), comb. n., Zapatella quercusphellos (Osten Sacken), comb. n. (= Zapatella quercussimilis (Bassett), syn. n.). A key based on adults for the species belonging to Zapatella is also given. Generic limits and morphological characteristics of Zapatella and closely related genera are discussed.

plesiomorphic characters were used instead of synapomorphies or autapomorphies, and thus the majority of current Cynipini genera in the Nearctic are polyphyletic, instead of being monophyletic. The new data recently obtained on the phylogeny, phylogeography, evolutionary conservatism of host shifts were not considered in the previous reviews and revisions (Liljeblad et al. 2008, Stone et al. 2009).
The validity of some Nearctic species of Callirhytis and there taxonomic position are discussed.

Material and methods
Adult gallwasps of an undescribed species were reared from acorn galls collected on Quercus costaricensis by the second author (PH) in Costa Rica; specimens belonging to yet another species were reared from galls collected on Q. humboldtii by the first author (JPV) together with Claudia A. Medina and Miguel Torres in Colombia.
We follow the current terminology of morphological structures Ronquist 1998, Melika 2006). Abbreviations for forewing venation follow Ronquist and Nordlander (1989), cuticular surface terminology follows that of Harris (1979). Measurements and abbreviations used here include: F1-F12, 1st and subsequent flagellomeres; POL (post-ocellar line) is the distance between the inner margins of the posterior ocelli; OOL (ocellar-ocular line) is the distance from the outer edge of a posterior ocellus to the inner margin of the compound eye; LOL (lateral ocellar line), the distance between lateral and frontal ocelli. The width of the forewing radial cell is measured from the margin of the wing to the Rs vein.
Digital images of wasp anatomy were produced with a digital Nikon Coolpix 4500 camera attached to a Leica DMLB compound microscope, followed by processing in CombineZP (Alan Hadley) and Adobe Photoshop 6.0 by the last author (GM). The SEM pictures were taken with a Stereoscan Leica-360 by Palmira Ros-Farré (Barcelona University, Spain) at a low voltage (15KV) and with gold coating; the forewing of Z. nievesaldreyi was taken by JPV with a digital camera Cannon SX-210-IS, attached directly to the ocular of a stereomicroscope. Gall images of Z. grahami were taken by P. Hanson; galls of Z. nievesaldreyi by the fourth author (M T).
The type material is deposited in the following institutions: Diagnosis. Partially resembles Callirhytis, Bassettia and Plagiotrochus. However, in Zapatella, the malar sulcus is absent; mesosoma strongly arched, short, as long as high in lateral view; mesoscutum with numerous fine short, interrupted transverse striae with numerous longitudinal anastomosis connecting transverse striae and together forming a net-like, delicately reticulate, irregular sculpture; the pronotum laterally delicately reticulate; the metascutellum rugoso-reticulate; the metanotal trough and the lateral area of the propodeum with dense white setae. In Callirhytis a distinct malar sulcus is present; the mesosoma less arched, always at least slightly longer than high in lateral view; the transversely orientated rugae on the mesoscutum are much stronger with much fewer anastomoses between them; the pronotum with distinct strong rugae laterally; the metascutellum rugose, never reticulate; the metanotal trough and the lateral area of the propodeum without or with very few setae. In Bassettia the mesosoma is strongly compressed dorsolaterally, distinctly longer than broad; the head always more massive from above and nearly rounded in anterior view, broader than the mesosoma. In Plagiotrochus the sculpture of the mesopleuron, the shape of propodeal carinae and the length of the prominent part of the ventral spine of the hypopygium are quite different. The most striking characters that differentiates Zapatella from the abovementioned genera are the long prominent part of the ventral spine of the hypopygium, which is 6.0-8.5 times longer than broad; hind coxae with dense white setae on the dorsoposterior surface, while in the other mentioned genera the prominent part of the ventral spine of the hypopygium is very short, at most 2-3 times longer than broad, and hind coxae without dense setae. For more details see also the Discussion.
Description. Body, including antennae and legs, predominantly chestnut brown; in some species head partially, mesoscutellum and stripes on mesoscutum dark brown to black. Head 1.3-1.5 times as broad as high in anterior view, massive from above and slightly broader than mesosoma. Gena broadened behind eye, as broad as transverse diameter of eye; malar sulcus absent. Antenna with 11 flagellomeres in female, 13 in male.
Mesosoma strongly arched, short, as long as high in lateral view. Pronotum delicately reticulate laterally; mesoscutum with numerous fine interrupted short transverse striae with numerous longitudinal anastomosis connecting transverse striae and together forming a net-like, delicately reticulate, irregular sculpture. Notauli complete (only in Z. herberti) or incomplete, extending to 1/2-2/3 length of mesoscutum, converging, deep and broad posteriorly [in some species, on first view, notauli seem to be complete; however, these are just darker lines, not impressed notauli, e.g. Z. quercusmedullae]. Anterior parallel lines extending to 1/2 length of mesoscutum; parapsidal lines distinct and broad, starting from posterior margin and extending to 1/2 length of mesoscutum; median mesoscutal line present or absent. Mesoscutellum 0.5 times as long as mesoscutum, as long as broad, not or only slightly overhanging metanotum, center of disk reticulate, sides and posterior 1/3-2/3 dull rugose; scutellar foveae present, indistinctly delimited posteriorly. Mesopleuron uniformly delicately reticulate, smooth and shiny basally. Metascutellum rugoso-reticulate; metanotal trough and lateral propodeal area with dense setae. Central propodeal area delimited by distinct subparallel or slightly bented outwards lateral propodeal carinae. Dorsoposterior surface of hind coxa with dense white setae. Tarsal claws simple, without basal lobe. Forewing venation pale yellow, indistinct, R1 inconspicuous, hardly traceable; wing margin without cilia. 2nd metasomal tergite with felt-like dense ring of white setae, interrupted dorsally and few setae scattered on lateral surface of tergite; narrow posterior band on 2 nd metasomal tergite and all subsequent tergites with very delicate dense micropunctures. Prominent part of ventral spine of hypopygium very long, 6.0-8.5 times longer than broad, with very few short white setae in two rows, directed ventrally; subapical setae absent.
Etymology. Based on a word-play in football, a joke often used between some coauthors and prof. Graham N. Stone (Edinburgh University), in honour of whom one of the species is named.
Gender. Feminine. Biology. According to the emergence dates of adults obtained from the collected galls, both sexual and asexual forms are present in the newly described genus. However, the emergence periods of alternate generations are overlapping. Moreover, no morphological differences have been observed between sexual and asexual females. The duration of life cycle is probably more than one year. In the Neotropical area the sexual form (Z. grahami Pujade-Villar & Melika, sp. n.) is obtained from acorn galls, while the asexual form (Z. nievesaldreyi Melika & Pujade-Villar, sp. n.) from twig galls; in the Nearctic area the asexual forms are obtained from twig and bud galls (Z. cryptica (Weld), comb. n., Z. herberti (Weld), comb. n., Z. quercusmedullae (Ashmead), comb. n.), Z. oblata (Weld), comb. n., while the sexual form, Z. quercusphellos (Osten Sacken) comb. n. (= quercussimilis (Bassett), syn. n. from twig galls. A detailed study of the biological cycles is necessary to solve this problem, which might be partially similar to that found in Plagiotrochus amenti Kieffer which has two reproductive modes: a heterogonic life cycle with alternation of generations in the circum-Mediterranean region, and an asexual, parthenogenetic life cycle in North America (Garbin et al. 2008), but the most important aspect is that in the Mediterranean area P. amenti has a partially overlapping emergence of the asexual and sexual forms (Benia et al. 2009). The same heterogenetic life cycle was also found in another Western Palaearctic gallwasp, Andricus quadrilineatus Hartig (Folliot 1961(Folliot , 1964. Distribution. Currently known from the Neotropics (Costa Rica and Colombia) and the Nearctic (USA, from California, through Texas to Florida and along the Atlantic coast, up to New York state), after transferring 4 Callirhytis species. Diagnosis. In Zapatella three species, Z. oblata, Z. grahami sp. n. and Z. nievesaldreyi sp. n., have the head and mesosoma partially dark brown to black. Z. oblata differs from the two other mentioned species by a very long median mesoscutal line which extending to 2/3 of the mesoscutum length, while in Z. grahami and Z. nievesaldreyi the median mesoscutal line is absent or present in a form of a very short triangle. In Z. grahami the females are much darker, POL 1.4 times as broad as OOL (Fig. 2), bottom of scutellar foveae with rugae ( Fig. 11), and the prominent part of the ventral spine of the hypopygium 7.5-8.5 times as long as broad (Figs 14,16). In Z. nievesaldreyi the females are lighter, POL equal OOL (Fig. 20), bottom of scutellar foveae smooth and without rugae (Fig. 22), and the prominent part of the ventral spine of the hypopygium 6.0-7.0 times as long as broad .
Length. 2.6-3.2 mm (n=15). Coloration. Body, including antennae and legs predominantly dark to chestnut brown. Head, brown with more or less extensive black areas on lower face, basal part of genae, central part of frons and vertex; posteriorly head dark brown to black. Antenna uniformly dark brown, F1-F5 lighter; mesosoma laterally black, except brown dorsolateral area of pronotum; propleura black; mesoscutum brown, with black stripes along anterior parallel and parapsidal lines; mesoscutellum dark brown to black, with slightly lighter scutellar foveae. Propodeum uniformly black; axillula yellowish; legs uniformly brown, with darker hind legs; metasoma brown, anterodorsally darker.
Head (Figs 1-3). Uniformly and delicately reticulated, with few white setae, 1.8-2.0 times as broad as long from above, 1.3-1.5 times as broad as high in frontal view and slightly broader than mesosoma. Gena broadened behind eye, as broad as transverse diameter of eye; malar space 0.35-0.4 times as long as height of eye, with delicate striae radiating from clypeus and nearly reaching eye margin, malar sulcus absent. POL 1.4 times as long as OOL; OOL 2.5 times as long as length of lateral ocellus and 1.8 times as long as LOL. Transfacial distance nearly 1.2 times as broad as height of eye; diameter of antennal torulus around 3.8 times as great as distance between them, distance between torulus and inner margin of eye equal to or slightly longer than diameter of torulus; inner margins of eyes parallel; lower face delicately coriaceous, with dense white setae, the median elevated area smooth. Clypeus small, squared, smooth, impressed in basal part, ventrally straight; anterior tentorial pits, epistomal sulcus and clypeo-pleurostomal line indistinct. Frons, vertex, interocellar area and occiput delicately reticulate. Postocciput alutaceous and shiny, smooth and impressed around occipital foramen; posterior tentorial pits large; height of occipital foramen as long as height of postgenal bridge; hypostomal carina emarginate, not going around oral foramen, continuing into gular sulcus. Labial palpus 3-segmented, terminal peg distinct, all three segments densely setose; maxillary palpus 5-segmented, terminal peg distinct, three terminal segments densely setose.
Mesosoma (Figs 9-12). 1.2-1.3 times as long as high in lateral view, with few white setae. Mesoscutum as long as broad, or only slightly longer than broad in dorsal view; with sparse scattered setae and transverse, delicate, interrupted striae which connect with longitudinally orientated weak striae, forming an irregular network of striae, and an irregularly reticulate surface sculpture. Notauli incomplete, extending at most to half length of mesoscutum; converging, deep and broad posteriorly. Anterior parallel lines extending to ½ length of mesoscutum; parapsidal lines distinct and broad, starting from posterior margin and extending to ½ length of mesoscutum; median mesoscutal line very short or absent. Mesoscutellum 0.5 times as long as mesoscutum, as long as broad, not overhanging metanotum, center of disk reticulate, sides and posterior 1/3 dull rugose; scutellar foveae present, ovate, not delimited posteriorly, bottom shiny, with some rugae; median carina broad. Mesopleuron uniformly delicately reticulate, smooth and shiny basally; mesopleural triangle conspicuously setose; dorsal axillar area coriaceous with numerous setae, lateral axillar area reticulo-carinate, without setae; axillula smooth, with white setae; subaxillular bar smooth, shiny, narrower than height of metanotal trough; postalar process long, strong, reticulate; metapleural sulcus reaching mesopleuron in upper 2/3 of its height. Metascutellum strongly reticulate, rectangular. Metanotal trough with short white setae; ventral impressed area at least twice as narrow as height of metascutellum, delicately reticulate. Propodeum setose lateraly, glabrous centrally; central propodeal area smooth, shiny, with many irregular wrinkles and rugae, lateral propodeal carinae weak, diverging anteriorly and converging in posterior 1/3. Nucha with irregular wrinkles and rugae.
Forewing (Fig. 13). Longer than body, hyaline, without cilia on margin; radial cell 3.3 times as long as broad; 2r distinct; R1 absent or hardly visible, Rs very inconspicuous, nearly straight; areolet absent or very indistinct. Rs+M indistinct, reaching basalis at half of its height.
Metasoma (Figs 14,16). Shorter than head+mesosoma, slightly higher than long in lateral view; base of 2nd metasomal tergite with felt-like dense ring of white setae, interrupted dorsally and few setae scattered on lateral surface of tergite. Narrow posterior band on 2 nd metasomal tergite and all subsequent tergites with very delicate dense micropunctures. Prominent part of ventral spine of hypopygium needle-like, tapering to apex, 7.5-8.5 times as long as broad, with two parallel rows of short white scattered setae which do not extend beyond the apex of spine.
Gall . Acorn galls. Individual chambers located in the acorn cup, often between the cup and the seed. Usually there is one gall per acorn, but sometime two or three.
Biology. Only the sexual generation is known and it induces galls on Quercus costaricensis. Galls were collected in February and later in October in forests located above 3000 m altitude, adults emerged immediately after the galls were collected, in February and October. This very unusual emergence of adults in two periods may be due to the sporadic nature of the collecting and to the peculiar phenology of Q. costaricensis. In the area where the galls were collected, Camacho and Orozco (1998) observed the flowering and fruiting phenology for a four year period (July 1986 to July 1990. The female flowers were present for ten months of the year, starting in the rainy season, with a flowering peak in the dry season. Male flowers were present for seven months, with a flowering peak from October to January, the period from the end of the rainy season and continuing to the beginning of the dry season. During the four years of observation there was only one fruiting period, which was synchronous, very productive, and extended for eight months (August 1988to March 1989; this is one year after the initial production of female flowers and six months after the end of male flower production. Distribution. Currently known only from Costa Rica (Cerro de la Muerte). Etymology. In recognition of the continuing contribution of our friend, prof. Graham N. Stone (Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, Scotland) to research on oak gallwasps. Description (Figs 19-30). Asexual form.
Head (Figs 19-21). Slightly broader than mesosoma, with few white sparse, short inconspicuous setae, more dense on lower face. Head very slightly transverse, only 1.2-1.3 times as broad as high in anterior view and massive from above, only 1.6-1.8 times as broad as long in dorsal view; gena broadened behind eye, broader than transverse diameter of eye, delicately uniformly reticulate; malar space without sulcus, 0.4-0.5 times as long as eye height, with striae radiating from clypeus and nearly reaching eye margin. Lower face delicately coriaceous, without elevated area medially. Clypeus slightly impressed, setose, alutaceous, rounded and slightly emarginate ventrally, medially not incised, anterior tentorial pits small, indistinct; epistomal sulcus and clypeopleurostomal line distinct. POL = OOL, OOL 2.5 times as long as length of lateral ocellus and 1.5 times as long as LOL, interocellar area microreticulate, not elevated; frons, vertex and occiput microreticulate; postocciput and postgenae alutaceous. Labial palpus 3-segmented, terminal peg distinct, all three segments densely setose; maxillary palpus 5-segmented, terminal peg distinct, three terminal segments densely setose.
Mesosoma (Figs 22-23, 27). 1.4 times as long as high, mesoscutum dorsally concave in later view. Pronotum setose, with uniformly delicately reticulate sides, without carinae posterolaterally. Mesoscutum slightly broader than long in dorsal view, with sparse scattered setae; with transverse, delicate interrupted striae which are connected with longitudinally orientated weak striae forming an irregular network of striae, together forming an irregular reticulate surface sculpture. Notauli extending nearly to half length of mesoscutum, deep and broad posteriorly, narrowing toward anterior end, with smooth bottom; median mesoscutal line absent or present in a form of short triangle; parapsidal lines distinct, extending to half length of mesoscutum; anterior parallel lines distinct, extending to 1/3 length of mesoscutum. Mesopleuron uniformly reticulate. Mesoscutellum as broad as long in dorsal view, centrally delicately coriaceous, dull rugose along sides and in posterior 1/3; scutellar foveae transversely ovate, with smooth and shiny bottom, distinctly separated medially by elevated coriaceous area. Metascutellum rugose, higher than height of smooth, shiny ventral impressed area of metanotum; metanotal trough smooth, shiny, with numerous white setae. Propodeum coriaceous, with dense white setae laterally; with smooth, shiny central propodeal area, delimited by distinct parallel lateral carinae, which slightly converge in posterior 1/3; anterior half of central propodeal area with dense white setae, posterior half without setae. Nucha with longitudinal rugae.
Forewing (Fig. 26). Nearly as long as body, pubescent, without cilia on margins; radial cell open, around 3.5 times as long as broad; veins very light, hardly traceable; areolet indistinct, usually invisible; vein Rs+M points slightly below midway along basalis; R1 and Rs never reach wing margin, very inconspicuous, often invisible or absent.
Metasoma . As long as head and mesosoma together, slightly longer than high; all metasomal tergites smooth and shiny; base of 2nd metasomal tergite with felt-like dense ring of white setae, interrupted dorsally, and a few scattered setae on lateral surface of tergite. Narrow posterior band on 2 nd metasomal tergite and all subsequent tergites with very delicate, dense micropunctures. Prominent part of ventral spine of hypopygium needle-like, tapering to apex, 6.0-7.0 times as long as broad, with two parallel rows of short, white, scattered setae.
Gall (Fig. 31). Inconspicuous galls in twigs, without visible enlargement (swelling) of the infested twig (branch). The larval cells, 2×1 mm, are nested in the wood parallel one to another.
Biology. Only females are known to induce galls hidden in twigs on Quercus humboldtii. Twigs with galls were collected in May and adult wasps immediately emerged in the same month.
Distribution. Currently known only from Colombia, Boyaca, from deciduous mixed broad-leaved forests located about 2000 m altitude.
Etymology. In recognition of the continuing contribution of Dr. José Luis Nieves-Aldrey (Museo Nacional de Ciencias Naturales-CSIC, Departamento de Biodiversidad y Biología Evolutiva, Madrid, Spain) to research on oak gallwasps.
Species transferred to Zapatella. Five Nearctic Callirhytis species possess the same character set as the above two species and thus they are transferred to Zapatella. ( Only the asexual generation is known. It induces bud galls on Q. myrtifolia Willd. and Q. falcata Michx. in the USA (Florida and Alabama) (Weld 1922b, Burks 1979. Type galls were collected in October and adults emerged the next year in May (Weld 1922). The affected terminal bud cluster becomes enlarged, one or two green leaves sometimes grow out beyond the bud scales, and later the bud turns brown; the gall is completely hidden within the bud and is conical, with a thin-walled cell and a tuft of hairs near the apex (Weld 1922b).

Zapatella cryptica
The female is entirely uniformly reddish brown and the notauli are incomplete, reaching to 3/4 of the mesoscutum length, but darker lines that look like notauli reach the anterior margin of the mesoscutum; the median mesoscutal line is impressed and reaches the pronotum; the prominent part of the ventral spine of the hypopygium is 6.3 times as long as broad. See also the Zapatella species key.  Figures 52-58, 60, 62 Cynips quercusphellos Osten Sacken, 1861. Callirhytis quercusphellos (Osten Sacken ) (Burks 1979). Cynips quercussimilis Bassett, 1864, syn. n. Callirhytis quercussimilis (Bassett) (Burks 1979 Weld, 1925 (Weld's handwriting label). The two specimens were compared by GM to the Osten Sacken's cotype, deposited at the USNM (Washington, DC) and obtained by L.H. Weld from the Museum of Comparative Zoology by exchange (Weld 1922b) and they appeared to be identical with that specimen (cotype). For Cynips quercussimilis: Three female and one male paratypes: 'Waterbury, Ct., H.F.Bassett Coll.; Type; Beut. Coll rec'd 1935'.
Zapatella quercusphellos was collected also at Rosslyn, Virginia from Q. imbricaria in June and Q. phellos in May, adults emerged in late June. In both cases the greenish fresh galls were similar terminal enlargements on new growths, inconspicuous, only 5 mm long; after maturation galls were 8-10 mm in diameter (Weld 1926).
A detail examination of specimens of C. quercusphellos and C. quercussimilis, mentioned above, showed no appreciable morphological differences and thus, C. quercussimilis is a syn. n. of C. quercusphellos and here in the species transferred to the Zapatella genus, Z. quercusphellos, comb. n. Females are uniformly dark reddish brown; the notauli are incomplete, extending to half the mesoscutum length, with darker lines reaching the anterior margin of the mesoscutum; the median mesoscutal line extending to 1/2 of the mesoscutum length, further indicated by a dark line only; the prominent part of the ventral spine of the hypopygium is 6.2 times as long as broad ventrally. The male is much darker than the female, with a dark brown head and mesosoma, while the metasoma is slightly lighter (otherwise quite similar to Z. grahami). See also the key to Zapatella species.
Only the sexual generation is known. It induces stem swelling galls on Q. incana, Q. falcata, Q. ilicifolia Wangenh. , Q. imbricaria, Q. myrtifolia and Q. phellos along the Atlantic coast, from Florida to New York state (Burks 1979).
Only the asexual generation is known. It induces bud galls on Q. coccinea Muench. and Q. falcata in Virginia, USA (Weld 1952). The frons, vertex and head posteriorly are dark brown to black, the mesoscutum along and between anterior parallel lines and along parapsidal lines is black, scutellar foveae and the central propodeal area are also dark brown; the rest of the body is reddish brown. Notauli are complete, the median mesoscutal line extending to 2/3 of the mesoscutum length, scutellar foveae transverse; the prominent part of the ventral spine of the hypopygium is very long, about 8.5 times as long as broad from ventral view. -Head and mesosoma with large dark brown to black patches (Figs 63-68); scutellar foveae transverse, broader than high (Fig. 68)  Body darker, head and mesosoma always with large dark brown to black spots (Figs 1,2,4,5,9,10,12); POL 1.4 times as broad as OOL (Fig. 2); bottom of scutellar foveae with rugae (Fig. 11); prominent part of ventral spine of hypopygium 7.5-8.5 times as long as broad (Figs 14, 16). Acorn galls (Figs  17-18 (Fig. 20, 40); bottom of scutellar foveae smooth, without rugae (Fig. 22, 44); prominent part of ventral spine of hypopygium 6.0-7.0 times as long as broad (Figs 29-30). Galls in twigs ........6 6
Callirhytis balanaspis Weld (only the asexual generation is known) induces acorn galls on red oaks, also has a very pale venation, R1 invisible, the malar sulcus absent, the mesoscutum with delicate, net-like reticulate transverse sculpture, as in Zapatella. However, the ring of very dense white setae at the base of the 2 nd metasomal tergite is absent and the prominent part of the ventral spine of the hypopygium is only 3.0-3.5 times as long as broad. This species is definitely not a Callirhytis 'sensu stricto', it closely resembles Zapatella, and form a discrete unit within Callirhytis 'sensu lato'.
In Callirhytis corrugis (Bassett), which induces acorn galls on red oaks (Burks 1979), the forewing venation is pale, with some veins invisible, but the mesoscutum is coarsely transversely rugose, the malar sulcus is present, POL is shorter than OOL, the female antenna has 12 flagellomeres, the ring of very dense white setae at the base of the 2 nd metasomal tergite is absent, and the prominent part of the ventral spine of the hypopygium is less than 2.0 times as long as broad. It is a true Callirhytis as noted in Melika and Abrahamson (2002).
In Callirhytis glomerosa Weld, which induces bud galls on red oaks, the malar sulcus is absent, the ring of very dense white setae at the base of the 2 nd metasomal tergite is present, the hind coxae have dense white setae on the dorsoposterior surface as in Zapatella; the mesoscutum is very finely transversely rugose and the prominent part of the ventral spine of the hypopygium is much shorter, as in Callirhytis. However, it differs form both genera in the trapezoid head in anterior view (much shorter from above) and the female antenna with 12 flagellomeres. This species is definitely not a Callirhytis 'sensu stricto', closely resembles Zapatella, and forms a discrete unit within Callirhytis 'sensu lato'.
Callirhytis medularis Weld induces stem swelling galls on red oaks and is only known from the sexual generation. However, in C. medularis, the female antenna has 12 flagellomeres, the head is more massive from above, much broader than the mesosoma; the mesoscutum is dull rugose, with strong transverse ridges, the mesoscutellum broader than long, the metanotal troughs and hind coxae without dense white setae, the 2nd metasomal tergite without a ring of dense white setae at the base; the ventral spine of the hypopygium is much shorter. This species is definitely not a Callirhytis 'sensu stricto', closely resembles Zapatella, and forms a discrete unit within Callirhytis 'sensu lato'.
Preliminary morphological analysis (GM and JPV, umpublished data) also showed that some Nearctic Callirhytis species that induce stem swelling galls on different sections of oaks, form distinct morphological and phylogenetic units. Thus, some of these discrete morphological groups form distinct genera, which might be monophyletic groups.