Introduction

Van der Wulp (1890) described Exorista ignobilis from Guerrero, Mexico, based on a single male. The species was subsequently moved to Winthemia Robineau-Desvoidy, 1830, by Reinhard (1931) and has continued to be treated as a valid species of Winthemia to the present day (Guimarães 1972). However, Reinhard (1931) misidentified the species; he did not examine the holotype of Exorista ignobilis but instead relied on notes taken of it by J.M. Aldrich in 1929. Based on these notes, Reinhard (1931) misidentified three specimens from Chile and Argentina as Winthemia ignobilis and redescribed the species from this material. Aldrich (1934) himself accepted the identifications of Reinhard (1931) and included the species under the same combination in his faunal treatment of the Tachinidae of Patagonia and South Chile. Cortés and Hichins (1969) also recognized a Chilean species of Winthemia as Winthemia ignobilis. Although the identities of these specimens from Chile and Argentina have yet to be clarified, we suspect that everything once called Winthemia ignobilis from these countries is Winthemia reliqua Cortés & Campos, 1971.

A second nominal species, Winthemia antennalis, was later described by Coquillett (1902) based on a single female from Los Angeles County, California, United States. Coquillett (1897) had earlier misidentified this single specimen as Winthemia nigrifacies (Bigot, 1889) in his key to the species of Winthemia of America north of Mexico. Tothill (1912) continued the placement of this species in Winthemia in his key to the North American species of the genus, as did Reinhard (1931) in his revision of the “American” species of Winthemia. This classification was also followed by Sabrosky and Arnaud (1965) in the Catalog of the Diptera of America north of Mexico. Guimarães (1972), however, removed Winthemia antennalis from Winthemia in his revision of the Winthemia of America north of Mexico. Without further explanation, he wrote in his abstract: “Winthemia antennalis Coquillett does not belong in this genus and its correct placement has not been determined” (Guimarães 1972: 27). Sabrosky (1973) apparently agreed, as he did not include Winthemia antennalis in his paper on the identification of Winthemia species of America north of Mexico.

Winthemia antennalis was again treated as a Winthemia species, albeit provisionally, by Wood (1987). Wood (1987: 1210) explained this placement in a footnote: “Although arrangement of postpronotal bristles is different from other species of Winthemia, the male terminalia and unembryonated planoconvex egg suggest a relationship, which may ultimately be resolved by additional study of the tribe Winthemiini”. Recently, O’Hara and Wood (2004) maintained this classification and listed Winthemia antennalis under Winthemia in their catalogue of the Tachinidae of America north of Mexico.

The enigmatic placement and identity of Winthemia ignobilis and Winthemia antennalis became a topic of discussion among us when several specimens provisionally identified as Winthemia antennalis were collected in the Gila National Forest of New Mexico, United States, during the field meeting of the North American Dipterists Society in 2007. Upon further study we have determined that Winthemia antennalis Coquillett is a junior synonym of Exorista ignobilis van der Wulp and that this taxon belongs not to the Winthemiini but to the Ethillini, a tribe hitherto unknown from the New World. We discuss below the characteristics of the Ethillini and propose a new genus for the single known New World species of this tribe.

Materials and methods Specimens

Male terminalia of Neoethilla ignobilis were dissected following the method described in detail by O’Hara (2002), then dehydrated with ethanol and critical point dried. After examination, the terminalia were rehydrated and preserved in glycerine in a plastic microvial pinned below the specimen (cf. Cerretti and Shima 2011). One egg, almost entirely exposed but still attached to the ovipositor of a dried female of Neoethilla ignobilis from Plymouth, Massachusetts (CNC), was removed by tilting it carefully with a pin and then mounted on a micropin. After ESEM examination the egg was glued on a tag and pinned below the source specimen. Male terminalia, pinned specimens and egg were examined, uncoated, with a Hitachi TM1000 environmental scanning electron microscope (ESEM); male terminalia were also slide mounted and examined with a Leica DMLS. Figures 1a–e were prepared from composites of images captured using a Canon EOS 40D Digital SLR camera body, with a Canon MP-E 65mm 1–5X macro lens, mounted on a Kaiser RS1 copy stand (for further details see O’Hara 2012); figures 5a–c were prepared from composites of images captured with a Nikon Digital Sight DS-L1, DS-5M mounted on a Leica DMLS. Specimens examined are preserved in the following collections (acronyms used in the text):

BMHN Natural History Museum [formerly British Museum (Natural History)], London, United Kingdom (N. Wyatt).

CNC Canadian National Collection of Insects, Agriculture and Agri-Food Canada, Ottawa, Canada.

MZUR Museum of Zoology, Università degli Studi di Roma “La Sapienza”, Rome, Italy (A. Vigna Taglianti).

USNM National Museum of Natural History [formerly United States National Museum], Smithsonian Institution, Washington, United States (N.E. Woodley).

Label data of the holotypes of Exorista ignobilis and Winthemia antennalis are cited verbatim with the end of lines and labels indicated by the following symbols: /, end of a line and beginning of the next; //, end of a label and beginning of the next (from top to bottom on the same pin).

Terminology

Morphological terminology generally follows McAlpine (1981), except for the antenna and a few details of thoracic chaetotaxy for which we are following Stuckenberg (1999) and Tschorsnig and Richter (1998), respectively. Measurements and ratios of the head follow Cerretti (2010).

Systematics Discussion

The Ethillini are a small tribe of Exoristinae formerly thought to be exclusively Old World in distribution. Most Ethillini share a number of character states with several members of Winthemiini but the relationships between these tribes remain unclear as they have not been investigated with a rigorous cladistic approach. The tribe can be defined by the following character states:

(1) Lower calypter strongly convex (Fig. 2d) – this is a very rare condition in the Tachinidae (as well as in other Calyptratae) and could arguably be considered apomorphic. Excluding Mycteromyiella Mesnil, 1966 and Calliethilla Shima, 1979, whose systematic placements in Ethillini are questionable (see also Crosskey 1984; Shima 1979; Cerretti 2012), all the other ethilline taxa share this character state. Interestingly, a very convex lower calypter is also present in a few species of Winthemia. This could easily be interpreted as convergence if not for the fact that Winthemiini also share other character states with Ethillini (see below),

(2) katepimeron usually entirely covered with fine setulae – within the subfamily Exoristinae this character state is shared with practically all known Winthemiini, a few Exorista and the exoristine genus Crassicornia Kugler, 1980 (cf. Cerretti et al. 2012; Cerretti 2012). Important exceptions exist for Atylomyia Brauer, 1898 and a few Amnonia Kugler, 1971 where the katepimeron is often entirely bare, and

(3) female ovipositor short (i.e., non-telescopic) – this could be a plesiomorphic condition compared to the long and telescopic one present in all Winthemiini.

In addition to the above states, all examined female ethillines have a macrotype plano-convex egg of white color. All the Exoristinae, most Phasiinae and the Eutheriini also have a plano-convex egg, or at least traces of a primitive planoconvex shape. This type of egg thus represents a plesiomorphic condition for Ethillini. It is worth noting that Ethillini show two reproductive strategies (Tschorsnig 1988): females with a short ovisac that lay unincubated eggs and females with a long ovisac in which eggs are stored until embryogenesis is complete (Paratryphera-group, see below).

Worldwide the following genera fall well within the above limits: Amnonia, Atylomyia, Ethilla, Ethylloides Verbeke, 1970, Gynandromyia Bezzi, 1923, Nemorilloides Brauer & Bergenstamm, 1891, Neoethilla gen. n., Paratryphera Brauer & Bergenstamm, 1891, Phorocerosoma Townsend, 1927, Prosethilla Herting, 1984, and Zelindopsis Villeneuve, 1943. As mentioned above, Calliethilla and Mycteromyiella have a questionable ethilline affiliation because of the lack of the distinctive convex lower calypter.

The grasshopper parasitoids Gynandromyia and Phorocerosoma and the genus Zelindopsis (Phorocerosoma-group) share the following: postpronotum with five setae, with the three basal strongest arranged in a triangle; female sternites 4–6 very large and exposed from the ventrolateral margins of the corresponding tergites; and egg surface dorsally smooth with two aeropilar areas, irregular in shape. The number and disposition of postpronotal setae are exactly the same as in nearly all the Winthemiini, and the egg characteristics are shared with several other Exoristinae. However, the features of the female abdominal sternites appear to be unique within the Exoristinae and may represent a strong apomorphy in support of the monophyly of this group of ethilline genera. Interestingly, males of Mycteromyiella share with males of several species of the Phoroserosoma-group the presence of distinctive spots of setulae and microtrichia on the ventral side of abdominal tergites 4 and 5, and also its members are parasitoids of Phasmatodea (Shima 1976), which are currently considered the living sister-group of the Orthoptera (cf. Grimaldi and Engel 2005).

All the remaining ethilline genera (Ethillini s. str.) share the following, probably derived, character states:

(1) postpronotum with the three strongest, basal, setae arranged in a line (Fig. 2b),

(2) male tergite 6 bare, wide and not indented antero-medially,

(3) male segment 7+8 very wide and platiform (cf. Tschorsnig 1985), and

(4) egg distinctly operculate (Tschorsnig 1988) (Fig. 5d–e).

The presence of operculate eggs is a very rare condition in tachinids. In most Exoristini an operculum is delineated by a line at the anterior end of the egg (cf. Wood 1972; Cerretti 2010), in Eutherini an oval “window” is situated on the dorsal surface of the egg immediately in front of its posterior end (Herting 1966), while in Ethillini s. str. an operculum is situated on the dorsal surface of the egg in its anterior half or in the middle (cf. Tschorsnig 1988; Tschorsnig and Richter 1998). Such substantial differences in the shape and position of the operculum in these groups suggest that the three types may have evolved independently and thus be non-homologous. Based on the four states listed here we consider the Ethillini s. str. to be a monophyletic lineage.

Finally, two probably monophyletic groups may be identified within Ethillini s. str. (cf. Tschorsnig 1985; Cerretti 2010). The first is the Paratryphera-group, composed of Amnonia, Atylomyia and Paratryphera. These taxa share the following character states:

(1) long ovisac for storing fully embryonated eggs,

(2) pregonite and postgonite at least partly fused basally,

(3) connection between male sternite 6 and segment 7+8 on right side very narrow,

(4) intermedium (cf. Tschorsnig 1985) not differentiated,

(5) epiphallus light-colored and attached to apical portion of basiphallus,

(6) ventrolateral sclerites of distiphallus greatly reduced, and

(7) dorsal connection between basiphallus and distiphallus almost membranous.

The second probably monophyletic group within Ethillini is the Ethilla-group, composed of Ethilla, Nemorilloides, Prosethilla and Neoethilla gen. n. These taxa share the following character states:

(1) short ovisac, females lay unembryonated eggs,

(2) pregonite and postgonite not fused,

(3) connection between male sternite 6 and segment 7+8 on right side very wide,

(4) intermedium very large,

(5) epiphallus massive and attached to basal portion of basiphallus (Fig. 5c),

(6) ventrolateral sclerites of distiphallus heavily sclerotized and covered with spinulae (Figs 4c–d, 5c), and

(7) dorsal connection between basiphallus and distiphallus heavily sclerotized (Fig. 5c).

We transfer the New World species Exorista ignobilis van der Wulp to the Ethillini and assign it to the new genus Neoethilla based on its distinctive characteristics. Neoethilla may share a sister-group relationship with Prosethilla, as evidenced by its lack of lateral marginal setae on the scutellum and similar egg morphology (operculum, microsculpture and shape very similar in these genera, judging from figures of Prosethilla by Tschorsnig (1988)). Neoethilla is clearly distinguishable from Prosethilla by its very large compound eye that occupies most of the head in lateral view (gena very narrow, compared to 1/3 or more of vertical eye height in Prosethilla), parafacial entirely covered with fine setulae (as in Winthemia), and ocellar setae not (or just slightly) differentiated from other setulae on the ocellar triangle.