. Bulletin. Natural history; Natural history. April 1983 Pec:hliman, , & Teskev: Diitera of Illinois—Tabanidae 69 40. Fore tibiae unicolorous; median abdomi- nal triangles obsolete, arising from faint posterior bands (Fig. 160) calens (in part) Fore tibiae bicolored; abdominal tri- angles small but distinct, not arising from bands (Fig. 180) novaescotiae 41. Tibiae unicolorous, fore tibiae may be slightly paler at base; first posterior cell slightly or not at all narrowed at margin; subcallus thinly pollinose or denuded; usually under l5 mm nigripes At least fore tibiae bicolored; fir
. Bulletin. Natural history; Natural history. April 1983 Pec:hliman, , & Teskev: Diitera of Illinois—Tabanidae 69 40. Fore tibiae unicolorous; median abdomi- nal triangles obsolete, arising from faint posterior bands (Fig. 160) calens (in part) Fore tibiae bicolored; abdominal tri- angles small but distinct, not arising from bands (Fig. 180) novaescotiae 41. Tibiae unicolorous, fore tibiae may be slightly paler at base; first posterior cell slightly or not at all narrowed at margin; subcallus thinly pollinose or denuded; usually under l5 mm nigripes At least fore tibiae bicolored; first pos- terior cell much narrowed, closed at margin or petiolate; subcallus polli- nose; larger species, 15-19 mm 42 42. Frons over 6 times as high as width at base; hind tibiae uniformly yellowish white, barely darkened at apex; sec- ond abdominal segment with median triangle usually crossing segment, joining spot on first segment (Fig. 182); first posterior cell usually closed, frequently petiolate petiolatus Frons less than 6 times as high as wide; hind tibiae often extensively dark to- ward apex; second abdominal segment with median triangle rarely crossing segment (Fig. 183); first posterior cell may be open or closed, rarely petio- late melanocerus 43(38). Fore tibiae bicolored, basally pale with pale hair 44 Fore tibiae unicolorous, occasionally base somewhat brownish with orange hair 45 44. Frons narrow (Fig. 189), 5 times or more as high as wide; first posterior cell normally petiolate, sometimes closed at margin limbatinevris Frons moderately wide (Fig. 187), aver- aging times as high as wide; first posterior cell normally open although often narrowed at margin sulcifrons 45. Costal cell yellow; frons 6 times as high as width at base, distinctly widened above; antennae usually wholly orange turbidus Costal cell hyaline or faintly tinted; frons about times as high as wide, scarcely widened above; basal plate of third antennal segment partly black equalis Male
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