A new genus and species of Eucoilinae ( Hymenoptera , Cynipoidea , Figitidae ) parasitoid of Euxesta eluta Loew ( Diptera , Otitidae ) attacked Bt sweet corn in Argentina

1 División Entomología. Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, Paseo del Bosque s/n, B1900FWA, La Plata, Argentina 2 Cátedra de Zoología Agrícola, Facultad de Ciencias Agrarias, Universidad Nacional del Litoral, R.P. Kreder 2805, 3080, Esperanza, Santa Fe, Argentina 3 Researcher of the Comisión de Investigaciones Científicas de la provincia de Buenos Aires (CIC), Argentina


Introduction
Eucoiline wasps are koinobiont endoparasitoids of dipterous Muscomorpha larvae and constitutes the most abundant and diverse subfamily of Figitidae.However, there has been poor taxonomic information on this subfamily in the Neotropical region, the only key to eucoiline genera cited for this region was published by Buffington and Ronquist (2006) and an updated synthesis of the knowledge on this subfamily was given by Díaz et al. (2008).Forshage and Nordlander (2008) proposed a tribal classification recognizing the following taxa: Diglyphosemini, Kleidotomini, Trichoplastini, Eucoilini and Ganaspini.Later, Buffington (2009) added Zaeucoilini to the group.Species belonging to Ganaspini attack Agromyzidae, Calliphoridae, Canaceidae, Chloropidae, Drosophilidae, Ephydridae, Lauxaniidae, Lonchaeidae, Phoridae, Sarcophagidae, Sepsidae, Tephritidae and Otitidae.The larvae of Otitidae are generally saprophagous, but some of them have developed phytophagous habits, eg.species of Euxesta Loew (Artigas, 1994).Species of this genus are secondary pests on garlic, tomatoes, potatoes, plants fruits, cassava and sweet corn, among others.Bt sweet corn is a transgenic plant genetically modified to include genes of the naturally occuring soil bacterium Bacillus thuringiensis Berliner (or Bt)".
In Santa Fe province (Argentina), the crops of Bt sweet corn are attacked by species of Euxesta (Diptera: Otitidae) that are considered secondary pests, causing severe damage to sweet corn.Two species have been identified: E. mazorca Steycal and E. eluta Loew, both appearing simultaneously and producing serious losses (Bertolaccini et al., 2010).Larvae attack the silks and consume the kernel contents, especially in the tips, although they can extend to all the ear length.The activity of these larvae constitutes one way of entrance for saprophytic microorganisms, making the product unmarketable for direct consumption.In this context, a new natural enemy of E. eluta was found, belonging to the tribe Ganaspini.This paper describes the new monotypic genus Euxestophaga Gallardo n. gen., with a new species from Argentina.

Methods
We studied a total of 72 specimens (46 females and 27 males).The specimens from Santa Fe province were obtained from pupae of Euxesta eluta in the framework of the research project CAI +D 2011: 2011:501 201 101 00009 LI (Universidad Nacional del Litoral, Argentina).The larvae of Euxesta eluta were collected in a commercial crop of sweet Bt corn (hybrid=GSS0974).Each pupa was individually placed in Eppendorf®vials (1.5mm), with a damp paper inside in order to conserve moisture.The pupae were periodically reviewed to determine the emergence of adult flies or parasitoids.Once the parasitoids emerged, they were preserved in 70% EtOH, together with the host puparia, the adult specimens of the flies host emerging from other non attacked pupae were preserved in 70% EtOH.The terminology used in the description follows Buffington (2009).Morphological terms used in this revision were matched to the Hymenoptera Anatomy Ontology (HAO, Yoder et al. 2010) (see Appendix).Identifiers (URIs) in the format http://purl.obolibrary.org/obo/HAO_XXXXXXXrepresent anatomical concepts in HAO version.Biogeographical regions are in accordance with Morrone (2001Morrone ( , 2014)).The collection localities were georeferenced with free software QGIS version 2.10.1-Pisa.The photographs were taken with a Canon Powershot A 520 adapted to a Leica steromicroscope (S8APO).Type material is deposited at Museo de La Plata, Argentina (MLP) and United States National Museum (Smithsonian Institution), U.S.A (USNM).Type of Epicoela seminigra Díaz (MLP) and specimens compared to Type of Epicoela rubicunda Borgmeier (MLP) were studied.

Systematic treatment
Euxestophaga Gallardo, gen.n. http://zoobank.org/4AE50295-A5F5-4733-9A31-D9426AD831B5Figures 1-4 Diagnosis.This new genus can be separated from other Ganaspini by the following combination of characters: occiput diagonally striate; female antenna clavate, club consisting of six flagellomeres; male antenna with F1 modified and longer than F2; dorsal surface of scutellum areolate-punctate, posterior border of disc bluntly rounded; lateral bars of scutellum striate; dorsal surface of scutellar plate with midpit placed close posterior margin of plate, with two or three punctures on each side, with a setae on either side; forewings hyaline, apical margin with hair fringe, marginal cell closed; base of syntergum with hairy ring present; and micropunctures present on posteri-or1/3 of the syntergum.
Type species.Euxestophaga argentinensis Gallardo, sp.n.Description.Body stout, shiny.Head massive, subcircular in anterior view, broader than mesosoma, nearly glabrous.Toruli not projecting.Ocellar tubercle not prominent.Ocellar hair patches absent.Compound eyes glabrous.Inner orbital furrows present.Posterior margin of gena distinct, but not carinate.Occiput diagonally striate.Malar spaces smooth, without conical protuberances.Malar sulci present.Female antenna with 13 segments, club consisting of six flagellomeres; male antennae 15 segments, filiform.Shape of dorsal margin of pronotal plate in anterior view broadly truncate, emarginate.Mesoscutum longer than wide, quite arcuate, without median mesoscutal carinae, with rows of punctures in position of notauli, parascutal impressions incomplete.Shape of posterior part of scutellum in dorsal view bluntly rounded.Lateral bars of scutellum striate.Scutellar foveae wider than long, deep and large.Dorsal surface of scutellum areolate-puntate.Scutellar plate suboval, posterior margin rounded, dorsal surface with midpit placed close posterior margin of plate, with punctures on each side, with a setae on either side.Anteroventral cavity of metapleuron subcircular, setose.Forewings of normal size, hyaline, apical margin with hair fringe, basal margin lacking hair fringe, with membrane pubescence mostly reduced hair bases, marginal cell closed, longer than broad.Metasoma sessile; base of syntergum with hairy ring present, remainder of metasoma glabrous.Micropunctures present on posterior 1/3 of the syntergum more or less visible.
Biology.Specimens of this new genus and species were reared from Euxesta eluta on Zea mays L. (Bt sweet corn).Bertolaccini et al. (2010) cited Dettmeria Borgmeier (Eucoilinae, Zaeucoilini) parasitizing larvae of Euxesta species on Bt sweet corn in Argentina, but, on reviewing the material mentioned in this paper, we concluded that the specimens were misidentified as Dettmeria, which belongs to the new genus and species here described.
Etymology.In reference to genus of the host, Euxesta and "phagein", to eat.Gender: feminine.
Remarks.Within Ganaspini, Euxestophaga is similar in morphology to Epicoela Borgmeier and Striatovertex Schick, Forshage and Nordlander, all of them present occiput diagonally striate, dorsal margin of pronotal plate emarginated, forewing with erect setae on subcostal and membrane with pubescence reduced.Epicoela includes two species known from Neotropical region, whereas Striatovertex is a genus widespread in the New World, with 13 species in total; one species in Australia, and other introduced in Hawaii from North America (Schick et al. 2011).With reference to their biology, host species of Epicoela are unknown, while representatives of Striatovertex attack dipterous Sarcophagidae, Muscidae and Calliphoridae.
The three genera can be separated by the following characters: 1 Female antenna with F5 or F6 to F11 moniliform, club consisting of 6 or 7 flagellomeres (Figure 5).Dorsal surface of scutellar plate with a triangular concave area in anterior part (Figure 6).Description.Female.Total length 1.85-2 mm.(Fig. 1).Head and mesosoma black, metasoma completely dark reddish brown.Antennae brown, mandibles, wings venation and legs yellowish brown.
Head (Figs 1-3) in anterior view as high as wide.Malar sulci simple.Antenna (Fig. 1) with 13 segments, pilose, subcylindrical, flagellomeres 1 and 2 subequal in length, F6 to F11 moniliform, club consisting of six flagellomeres, with rhinaria.Posterior margin of gena distinct, but not carinata (Fig. 2, see arrow).Pronotum.Pronotal plate (Fig. 2) wide, striate in anterior half as well as bridge that connect this half with posterior half.Posterior half with row of setae, lateral foveae open.Dorsal margin emarginate.Pronotal ridge absent.Sides of pronotum convex, with a pubescent area on upper half of ventral margin (beneath pronotal plate).
Wings.Forewings hyaline (Fig. 1), apical margin with hair fringe, basal margin lacking hair fringe, with membrane pubescence mostly reduced hair bases, marginal cell closed, longer than wide.Legs (Fig. 1).Fore and mid coxa subequal in size, variously setose, hind coxa about twice the size of either fore or mid coxae, with a patch of woolly setae on posterior margin.Femora and tibiae sparsely setose, tibiae with more apprised setae; tarsomeres covered with dense appressed setae.
Etymology.In reference to the country where the specimen was collected: Argentina.