Euxesta obliquestriata Hendel, 1909

Korneyev, Severyn V., Hauser, Martin, Kameneva, Elena P. & Gaimari, Stephen D., 2022, A key to species of the Euxesta sororcula species group (Diptera: Ulidiidae: Lipsanini), with new synonymy and a new record from the U. S. A., The Pan-Pacific Entomologist 98 (2), pp. 150-162 : 155-156

Euxesta obliquestriata Hendel, 1909

Figs. 1e ; 2

Euxesta obliquestriata Hendel, 1909:167 (description, diagnosis), 1910:27 (catalog); Curran, 1935:11 (key); Steyskal, 1968:54. 18 (catalog).

Euxesta mazorca Steyskal, 1974:73 (description); Cruz et al., 2011:103 (record from Brazil); Díaz, 1982:51 (record from Peru); Huepe et al., 1986:17, 18 (record from Chile); Bertolaccini et al., 2010:215 (record from Argentina); syn. nov.

Type Specimens. Syntypes: Euxesta obliquestriata , 1 ♀, BOLIVIA, labeled: “Meshagua, Bolivia / Songo”; “ Euxesta / obliquestriata H. det. F. Hendel”; “coll. Hendel”; “Paratype” [yellow paper]; “Syntype Euxesta obliquestriata Hendel 1909 des. Korneyev & Kameneva 2001” (NHMW). 1 ♂, labeled: “Mapiri/2000m, 4.V.[19]03 / Lorenzopata” (SMTD). 1 ♀, labeled: “Bolivia-Mapiri / IV.[19]03 / S. Carlos 800m” (SMTD). 1 ♀, BRAZIL, labeled: “Stiglmayr / Rio Gr. [ande] do Sul” (HNHM). 2 ♀, BRAZIL, labeled: “Theresopolis / Brasil” (HNHM). 1 ♀, PARAGUAY, labeled: “Vezényi / Asuncion 1904” (HNHM) (examined by EPK).

Holotype, Euxesta mazorca , ♀, ECUADOR, labeled: “Quito Equa/2500m alt. | Estac. exper. / Sta Cataline / Aug 1966 / V. Vazquez | Feeding on tip of corn ear # xs 218”; “HOLOTYPE / Euxesta / mazorca / Steyskal \ USNM 72830” [Steyskal handwriting on red paper rectangle] (USNM).

Allotype and Paratypes, Euxesta mazorca : 1 ♂ allotype, 3 ♂, 1 ♀ paratypes, same labels as holotype except for “ALLOTYPE” and “PARATYPE” (USNM) (examined by EPK in 2001).

Additional Specimens Examined. 1 ♂, ARGENTINA: Salta: Rosario de Lerma, Malaise trap, 21–25.XII.1983 (CSCA); 2 ♂, 10–14.XI.1983 (CSCA); 1 ♀, 17–18. XI.1983, M. Wasbauer (CSCA). 1 ♀, BOLIVIA: Prov. La Paz: Cumbre Alto Beni, vicinity of Caranavi, 1685 m, 15°40′19″S 67°29′35″W, Malaise Trap, 15–21. IV. 2004, S. D. Gaimari & M. Hauser (CSCA); 1 ♀, 16.VI.2004, S. D. Gaimari & M. Hauser (CSCA).

Remarks. Hendel (1909:155) differentiated this species from E. sororcula as having: “die Spitzenbinde ist breiter als der glashelle Zwischenraum davor. Aussenrand der zweiten Querbinde concav” [the apical band wider than the hyaline interspace before it. Outer edge of the second crossband concave]. He described the species as closely related to E. sororcula and E. latifasciata and easily confused with them. It is distinguished from the former by the always slightly concave, non-convex outer edge of the discal wing band, the shape of the subapical crossband, which is much wider posteriorly and covers the crossvein dm-m almost in the middle, not at the proximal edge, and the much wider apical band, which is always wider than the narrow hyaline interspace before it. In E. sororcula , according to Hendel (loc. cit.), the interspace between the discal and subapical bands is more oblique and curved in a way that its concavity is on the proximal margin. The costal band is narrower than the interspace proximal to it. Hendel (1909) mentions that E. latifasciata differs according to the description and illustration by the scutellum reddish posteriorly and reddish legs, whereas E. obliquestriata fits Loew’s description of E. sororcula . The wing pattern of E. latifasciata resembles that of E obliquestriata except for the shape of the hyaline interspace proximal to the wing apex, which is concave outside instead of on the inside. Body (without ovipositor) and wing 4–5 mm long ( Hendel, 1909:167).

Steyskal (1974) described E. mazorca as follows:

“Length of wing 4.0–4.8 mm. Agrees with E. obliquestriata in basic pattern of wing, interantennal space of same color as lower parts of face (not dull black), wholly dark metallic blue-green abdomen, and largely black legs. Head as in Fig. 2 ; largely yellowish, metallic greenish on frontal triangle, parafrontal plates, vertex, and occiput; middle of face and sides of clypeus infuscated to variable extent; antenna usually wholly orange, but 3rd segment sometimes a little infuscated above; front largely almost polished, narrow orbits silvery tomentose.

Thorax wholly metallic greenish, mesoscutum lightly pale grayish tomentose with indistinct more blackish arcuate postsutural transverse band, especially evident above wing bases; scutellum blackish. Angle between line connecting posterior dorsocentral bristles and each acrostichal bristle 45°.

Legs largely metallic greenish; forecoxa (except basilateral oval dark spot), most of inner face of forefemur, fore- and midbasitarsi, hindbasitarsus (except more or less of tip), and distal end of forefemur tawny.

Wing as in Fig. 1 [= Fig. 2b in the present work] medial hyaline band attaining costa in nearly full width, impinging on only small apical part of 1st vein (R 1); preapical hyaline band somewhat narrower than apical brown band; section of 4th vein crossing preapical hyaline band about equal in length to apical section in brown area; length of apical brown area in discal cell less than half as great on 5th vein as on 4th vein; brown area in base of 2nd costal cell squarish, not extended along costa; extension of tip of anal cell about as long as greatest width of cell.

Abdomen wholly metallic bluish green, very lightly pale tomentose.”

Steyskal wrote that the type series of E. mazorca had previously been identified as E. obliquestriata . Nonetheless, he did not compare these two nominal species at all.

In 2001, EPK studied the type series of both E. obliquestriata and E. mazorca and found no essential characters to distinguish them; all the minor differences in coloration and wing pattern are variable, leaving no gap between them. We consider these species to be conspecific and thus the names to be synonyms. The wing depicted in Hendel (1910) (see Fig. 2a ) has some differences from our illustration made from the same wing of the same specimen ( Fig. 2c ) and does not show differences from that of E. mazorca .

Distribution. Argentina ( Bertolaccini, 2010), Colombia, Ecuador, Peru ( Steyskal, 1974), Chile ( Huepe et al., 1986), Brazil ( Hendel, 1909; Cruz et al., 2011), Bolivia, Paraguay ( Hendel, 1909).

Biology and Economic Importance. Euxesta obliquestriata is considered a major pest of sweet corn ( Díaz 1982, Huepe et al. 1986 [as E. mazorca ]), along with some other Chaetopsis and Euxesta species, but it is not clear if they infest corn only as secondary invaders, together with the other species, or as independent pests. Also, it is not always clear whether the species was identified by an expert, and therefore some specimens reported in the literature as E. obliquestriata may refer to other species. However, it is obvious that it is widespread throughout the tropics of the New World, where it is a native pest associated with corn plantations not treated with pesticides.

Figures

Figure 1. Wings: (a) Euxesta latifasciata; (b) E. leucomelas (=E. fascipennis); (c) E. wettsteini; (d) E. abdominalis, syntype, MCZ; (e) E. sororcula, type, NHMD; (f) E. obliquestriata, syntype, NHMW. (a–b modified from Wulp (1899); and d modified from EOL site https://eol. org/pages/734579/media). Abbreviations: SA = subapical band; A = apical band; phi – preapical hyaline interspace. Fine black lines show the ratio of SA and phi along vein R4+5 and light blue arrows indicate other characters mentioned in the key.

Figure 2. Euxesta obliquestriata (= E. mazorca): (a–d) wing; (e) head, left-side lateral view; (f) head, anterodorsal view; (g) head, left-side lateral view; (h) head, anterodorsal view; (i) habitus, left-side lateral view. (a, c, e, f) type specimen from NHMW: (a) modified from Hendel (1909); (d, i) holotype of E. mazorca, syn. nov.; (b, g–h) adapted from Steyskal (1974).