Tritoxa Loew, 1873

Sinclair, Bradley J., Macleod, Alyssa M. & Wheeler, Terry A., 2021, Revision of the Nearctic genus Tritoxa Loew (Diptera: Ulidiidae), Zootaxa 4920 (3), pp. 359-379 : 360-361

Genus Tritoxa Loew

Tritoxa Loew, 1873: 102 . Type species: Trypeta flexa Wiedemann, 1830 (by subsequent designation of Coquillett, 1910: 617).

Diagnosis. The genus as a whole is immediately recognizable by the brown or black wings with three hyaline crossbands. Other characters include broadly flattened palpi, a strong anepisternal and katepisternal seta, vein R 1 setulose above from just distal of humeral crossvein, vein R 2+3 slightly sinuous, cell cua closed apically without extension; females with three elongate, cylindrical spermathecae and abdominal segment 6 significantly reduced; males with inner surstylus with prensisetae and phallus long and coiled, with ventral margin lined with spines.

Redescription. Head: dichoptic in both sexes, 1.3–2.6 times higher than wide; postocellar setae well developed, divergent; inner and outer vertical setae long, reclinate; ocellar setae short and latero-proclinate, slightly shorter and thinner than postocellar setae; 2 strong reclinate orbital setae, upper often stronger; frons wider than eye, essentially as tall as wide, with short interfrontal setulae except between upper pair of orbital setae; proboscis brown; palpus broadly flattened, yellowish to brownish with black setulae; lunule with setulae under anterior frontal margin sometimes visible; gena with subvibrissal setae and at least 1 long postgenal seta; antennal scape with dorsal rim of setae; pedicel densely setulose dorsally and dorsolaterally, with continuous rim of setae ventrally, also with notch prior to antennal seam; postpedicel pubescent, generally 3 to 5 times longer than wide; arista brown, short pubescent; supracervical setae yellow or black. Thorax: thoracic dorsum opaque with broad shiny lateral border; 1 postpronotal seta; 2 notopleural setae; 1 supra-alar seta; 1 postalar seta; 1 intrapostalar seta; 1 prescutellar dorsocentral seta; 1 prescutellar acrostichal seta; 2 pairs of scutellar setae; pleural segments shiny with white pruinescence; anepisternum usually with straight posterior row of setulae; anepisternum and katepisternum minutely setulose; 1 katepisternal seta; 1–2 anepisternal setae. Wing: brown or black with three oblique, hyaline crossbands (subbasal, discal, subapical) ( Fig. 9 ); area below subbasal oblique crossband and alula opaque, only tinged with colour; distinct humeral break present; R 1 setulose above from just distal of humeral crossvein, R 2+3 slightly sinuous, M vein distal to r-m crossvein gently and strongly arched; CuA arched to straight; apex of cell cua without point or extension. Halter white to yellowish-white. Abdomen: uniformly setulose; female with slender anteromedial apodemes present on sternites 3–6; tergite and sternite 6 short and transverse, subequal, significantly narrower than previous sclerites. Male terminalia ( Fig. 16 ): hypandrium U-shaped, with pregonite narrow, bearing row of fine setae; postgonite small and oval. Epandrium wide with many long setae; inner surstylus broad, bearing prensisetae; outer surstylus digitiform; subepandrial sclerite V-shaped, with stiff setae; cercus with long setae; phallus long and coiled with many long ventral spines with longer and denser fine spines apically. Female terminalia: oviscape short, nearly as long as tergite 5, slightly shorter than aculeus. Eversible membrane slightly longer than aculeus, with 2 pairs of taeniae, not reaching posterior margin; membrane finely microtrichose on anterior 0.75, apical 0.25 with fine multidentate scales. Aculeus narrow, 4 times as long as wide; cercal unit with 3 pairs of long setae (subapical dorsal, subapical lateroventral and subbasal lateroventral) and shorter anterodorsal pair; 2 strong sensillae anterior to subapical lateroventral seta. Three elongate, cylindrical spermathecae.

Remarks. The major morphological characters used for species identification are wing patterns, body and supracervical setal colour, parafrontal pruinescence, and differences in surstylar chaetotaxy and shape.

In a molecular phylogeny of the Tephritoidea , Delphinia Robineau-Desvoidy, 1830 and Tritoxa were resolved as sister taxa in a dataset that included 15 species of Ulidiidae ( Han & Ro 2016) . These two genera both share an obliquely directed subbasal hyaline crossband, with accompanying pale anal lobe and alula. These two Nearctic genera were not included in the barcode study of Palaearctic Ulidiidae ( Galinskaya et al. 2014) . Tritoxa is assigned to the subfamily Otitinae , tribe Cephaliini , a group of nine genera supported by the single synapomorphy, extremely broad palpi ( Kameneva & Korneyev 2006).

Figures

FIGURES 6–13. Wings of Tritoxa species. 6. T. californica sp. nov.; 7. T. cuneata; 8. T. decipiens sp. nov.; 9. T. flexa; 10. T. incurva; 11. T. pollinosa; 12. T. ra; 13. Tritoxa sp. Abbreviations: d bd—discal band; dm—discal medial cell; dm-m—discal medial crossvein; r-m—radial medial crossvein; sbap bd—subapical band; sbb bd—subbasal band.

FIGURES 14–17. Male terminalia of Tritoxa species. 14. T. californica sp. nov., posterior view; 15. T. californica, oblique lateral view; 16. T. cuneata, posterior view; 17. T. decipiens sp. nov., posterior view. Abbreviations: cerc—cercus; epand—epandrium; ph—phallus; prens—prensiseta; sur—surstylus.