Revision of the Nearctic genus Tritoxa Loew (Diptera: Ulidiidae) Author Sinclair, Bradley J. Canadian National Collection of Insects & Canadian Food Inspection Agency, OPL-Entomology, K. W. Neatby Bldg., C. E. F., 960 Carling Ave., Ottawa, ON, K 1 A 0 C 6, Canada Author Macleod, Alyssa M. 0000-0002-7048-8481 Department of Natural Resource Sciences, McGill University, Macdonald Campus, Ste-Anne-de-Bellevue, QC, H 9 X 3 V 9, Canada alyssa. m. macleod @ gmail. com; https: // orcid. org / 0000 - 0002 - 7048 - 8481 alyssa.m.macleod@gmail.com Author Wheeler, Terry A. text Zootaxa 2021 2021-01-29 4920 3 359 379 journal article 8337 10.11646/zootaxa.4920.3.3 3f20c135-c448-4c8c-a716-993e4f6d50d0 1175-5326 4478080 20794FBC-E83E-419F-945D-4F94C6F9A47C Key to the species of Tritoxa (modified from Steyskal (1967)) 1 Thorax and abdomen dark brown to black ( Fig. 1 ), wings with dark brown to black background ( Fig. 9 ); crossvein dm-m sinuate................................................................................. T. flexa (Wiedemann) - Thorax and abdomen reddish-brown to brown ( Fig. 2 ), wings with brown background ( Figs 6–8, 10–13 ); crossvein dm-m straight to slightly sinuate or angulate..................................................................... 2 2 Crossvein dm-m straight or slightly sinuate ( Figs 6–8, 10, 13 ); silvery parafrontal microtrichose stripe very narrow, only immediately adjacent to eye ( Fig. 3 )........................................................................ 3 - Crossvein dm-m angulate, or slightly angulate ( Figs 11, 12 ); silvery parafrontal microtrichose stripe broad, surrounding bases of orbital setae ( Figs 4, 5 )............................................................................... 7 3 Discal and subapical hyaline crossbands arcuate and parallel ( Fig. 10 ); subapical hyaline crossband attaining costa basad of crossvein r-m............................................................................ T. incurva Loew - Discal and subapical hyaline crossbands arcuate or straight ( Figs 6–8, 13 ); subapical hyaline crossband essentially straight, attaining costa apicad of crossvein r-m.................................................................... 4 4 Discal hyaline crossband reaching posterior wing margin, or at least extending beyond cell dm ( Fig. 13 ); small hyaline spot in costal cell distal to humeral crossvein; silvery parafrontal microtrichia stripe distinct, extending nearly half distance from eye margin to orbital setae......................................................................... Tritoxa sp. - Discal hyaline crossband not extending beyond cell dm ( Figs 6–8 ); costal cell distal to humeral crossvein dark, without hyaline spot; silvery parafrontal microtrichia stripe narrow, extending less than one-third distance from eye margin to orbital setae.. 5 5 Discal hyaline crossband ending in or very close to posterior distal corner of cell dm, generally tapered ( Fig. 8 ); inner surstylus with row of 5–8 strong prensisetae; outer surstylus arched mesally ( Fig. 17 )........................ T. decipiens sp. nov. - Discal hyaline crossband ending distant to posterior distal corner of cell dm and usually wide posteriorly ( Figs 6, 7 ); inner surstylus with prensisetae widely separated or in tight cluster; outer surstylus straight or arched ( Figs 14, 16 )............ 6 6 Inner surstylus with 3–4 strong, separated prensisetae; outer surstylus straight ( Fig. 16 ); phallus very long, comprising some 4–5 loops; discal hyaline crossband long, extending to opposite crossvein r-m ( Fig. 7 ).................. T. cuneata Loew - Inner surstylus with straight row of 4–5 thick prensisetae in tight cluster, decreasing in size with largest adjacent to outer surstylus ( Fig. 14 ); outer surstylus arched ( Fig. 14 ); phallus much shorter than typical of genus, comprising 2 loops ( Fig. 15 ); discal hyaline crossband shorter, not reaching opposite r-m crossvein ( Fig. 6 ).......................... T. californica sp. nov. 7 Crossvein dm-m with stump vein ( Fig. 12 ); silvery parafrontal microtrichia stripe extending 1/4 to 1/3 distance from eye margin to midfrons ( Fig. 5 ); discal hyaline crossband continuous from R 1 to posterior wing margin ( Fig. 12 ); anepisternum shiny............................................................................................. T. ra Harriot - Crossvein dm-m usually without stump vein ( Fig. 11 ); silvery parafrontal microtrichia stripe extending halfway from eye margin to midfrons ( Fig. 4 ); discal hyaline crossband disjunct along R 2+3 ( Fig. 11 ); anepisternum densely clothed in yellow microtrichia............................................................................. T. pollinosa Cole