Review of the little-known western Nearctic fly genus Philetus Melander (Diptera: Empididae), with a discussion of its phylogenetic assignment Author Cumming, Jeffrey M. Author Brooks, Scott E. Author Sinclair, Bradley J. text Zootaxa 2016 4093 2 261 274 journal article 10.11646/zootaxa.4093.2.7 4ece7a98-bd32-4fb5-acc4-ecb7128b8382 1175-5326 267656 9EBEA915-88BA-473F-9CC5-A944240D7095 Genus Philetus Melander Philetus Melander, 1928: 110 . Type species, Philetus memorandus Melander, 1928 (original designation). Melander, 1965: 455; Poole, 1996: 158, 368; Sinclair & Cumming, 2006: 74, 102–105, 107; Yang et al ., 2007: 350; Marshall , 2012: 288; Cumming et al ., 2014: 171, 205. Diagnosis . The genus is characterized by the following features: small size (body length 3.0–5.0 mm) brownish grey flies with silvery grey tomentum ( Figs 1 , 4 ); head produced obliquely downwards; ocelli positioned forward on broad V-shaped frons; eyes bare, dichoptic in male and female; inner eye incision present; antenna inserted just below middle of eye ( Figs 5, 6 ); apical stylus slightly tapered with 3 articles including minute terminal hyaline process, subequal to or slightly shorter than length of pyriform postpedicel ( Figs 7, 8 ); proboscis moderately long; epipharyngeal blades movable; palpus straight, directed forward ( Figs 5, 6 ); head and thoracic chaetotaxy dark; mesonotal setae on each side with a few short irregular presutural acrostichal setae, row of 4–6 long dorsocentral and 3–4 intra-alar setae, 1–2 postpronotal setae, 1–2 presutural supra-alar setae, 2 notopleural setae, 1 postalar seta, and 2 (pairs) of long scutellar setae; mesopleuron and laterotergite bare; legs without prominent bristles; wing (Fig. 9) with venation complete (for Eremoneura), including nearly straight Sc reaching C, forked R4+5, cell cua angled apically with CuA curved back towards short evanescent CuA+CuP vein, basal costal bristle present, pterostigma faint, anal lobe developed; male terminalia (Figs 11–20) with median apical hypandrial process, gonocoxal apodeme projecting anteriorly as process from anterodorsal margin of hypandrium, postgonite broad, ejaculatory apodeme lever-like and articulated to base of phallus, phallus tubular with desclerotized apex, epandrium deeply emarginate with left and right lamella connected basally, epandrial lobe present apically, proctiger differentiated into a long ventral and short medial subepandrial lobe attached to prolonged dorsal cercus; female terminalia (Fig. 10) with terminal segments partially telescopic, tergite 10 undivided without acanthophorites, cercus narrow, spermatheca unpigmented and sac-like. Geographical distribution ( Fig. 21 ). Known from Alaska and the Yukon Territory in the north to California, Nevada and Arizona in the south, including records from British Columbia , Washington, Oregon, Montana, Wyoming and Colorado (with undetermined female specimens listed in the Appendix). Remarks . In the Nearctic Region, this genus is most similar to Hesperempis Melander and somewhat like Hilara Meigen , but can be most easily distinguished from these empidid genera by the oblique form of the head with forward positioned ocelli and low inserted antennae. Philetus also has straight forward-directed palps and vein Sc nearly straight and joining C at an acute angle unlike Hilara . In addition, Hilara and most members of the Hilarini have vein R1 swollen prior to reaching C and males usually have the first tarsomere of the foreleg expanded (Sinclair & Cumming 2006). In their key to Nearctic genera of Empididae, Steyskal & Knutson (1981, p. 617) refer to a complete lack of thoracic setae in Hesperempis compared with Philetus , but this does not apply to all the included species of Hesperempis (Cumming et al . 2014) . However, the dark setae on the head and thorax of Philetus are diagnostic compared with the pale more inconspicuous chaetotaxy of Hesperempis . Except for differences in the male and female terminalia, specimens of Philetus also resemble the brachystomatid genus Heleodromia Haliday , although they can be easily separated by the presence of a forked R4+5 wing vein in Philetus . Marshall (2012: 288, fig. 5) provided a good-quality photograph of a live female specimen of Philetus , which is reproduced here with permission ( Fig. 1 ).