405 

 Wirth and Stone: Diptero 



Humboldt and Modoc counties to San Mateo and Mari- 

 posa counties pugetense Dyar and Shannon 1927 



Stem vein with light yellow hair; Placer and San Joaquin 1. 



counties to Inyo County — 



canonic olum Dyar and Shannon 1927 2. 



Claws simple 5 



Claws with a basal projection or subbasal tooth .... 13 

 Frons and terminal abdominal tergites shining black — 



or brown 6 3. 



Frons and terminal abdominal tergites distinctly 



pollinose 8 



Fore coxae darkened, brown; Inyo and Ventura counties 



to San Diego County. . . jacumbae Dyar and Shannon 1927 — 



Fore coxae clear yellow 7 



Hairs on stem vein and base of costa pale; Plumas 4. 



County to El Dorado County venustum Say 1823 — 



Hairs on stem vein and base of costa dark; Plumas 



County to Monterey County 5. 



tuberosum (Lundstroem) 1911 



Mesonotum with 1 or more distinct, rather broad, 

 straight stripes; if 1 it may be rather diffuse and not 



reach scutellum 9 



Mesonotum unstriped or the stripes very narrow and — 



some of them not straight 11 



A single median orange brown to black stripe; Mono 



and Inyo counties venator Dyar and Shannon 1927 



Seven alternating stripes of contrasting color 10 6. 



Darker stripes of scutum orange; lateral dark spots of 

 dorsum of abdomen absent or indistinct on most of the 

 segments, never as prominent as the median dark — 

 sclerites; ventral projections of paraprocts not long 

 enough to cross tips when in normal position (Monterey 



and Fresno counties to Riverside County) 



bivittatum Malloch 1914 7. 



Darker stripes of scutum dark brown to blackish; dorsum 

 of abdomen with pronounced dark lateral spots on 

 several of the segments, nearly as dark as the median — 

 sclerites; ventral projections of paraprocts distinctly 

 crossing each other when in normal position (Butte 8. 

 County to Santa Barbara and San Bernardino counties) 



trivittatum Malloch 1914 — 



Predominantly ash-gray and black species, the thorax 9. 

 with a pattern of blackish stripes on a gray ground; 



coxae gray 12 



Predominantly yellow or yellowish gray; thorax with — 

 almost no pattern; fore coxae clear yellow; San Bernar- 

 dino, Riverside, and Imperial counties 10. 



griseum Coquillett 1898 



Arm of genital fork with a somewhat darkened external 

 process; the internal process smaller and paler and 

 removed from one on other side; Modoc County to 



Monterey and San Diego counties 



vittatum Zetterstedt 1838 — 



Arm of genital fork with no external process; the 

 internal process large, pale, rather close to one of 11. 

 other side; Siskiyou County to San Diego County 



argus Williston 1893 



Claws each with a strong basal projection; Butte County 



meridionale Riley 1887 — 



Claws each with a small subbasal tooth 14 



Fore coxae dark; Plumas County to Riverside County 



piperi Dyar and Shannon 1927 



Fore coxae yellow 15 12. 



Frons shining or subshining 16 



Frons opaque, covered with pollen 17 — 



Mesoscutum with 3 lines, the median one straight and 

 slender, the lateral ones curved and somewhat wider; 13. 



Mariposa and Inyo counties hunteri Malloch 1914 



Mesoscutum not lined (fig. 14:19i); Siskiyou County to — 



Santa Barbara County arcticum Malloch 1914 



Anterior gonapophyses elongate, their inner margins 

 subparallel; hairs of paraproct long and stout; Siskiyou 14. 

 County to Riverside County . . .virgatum Coquillett 1902 

 Anterior gonapophyses short, their inner margins con- 

 cave; hairs of paraproct short and rather slender; — 



Siskiyou County to San Diego County 



canadense Hearle 1932 



Moles 



Radial vein with hair dorsally 2 



Radial vein bare dorsally 4 



Postnotum with appressed yellow scales; ventral plate 

 very narrow and acutely pointed medially, the basal 



arms strongly divergent aureum Fries 



Postnotum without scales; ventral plate broad 3 



Dististyle, when viewed from end, showing a flattened, 

 shiny, triangular area, 1 corner of this forming an inner 



lobe latipes Meigen 



pugetense (Dyar and Shannon) 



Dististyle tapering evenly to a point, not truncate in 



this manner canonicolum (Dyar and Shannon) 



Dististyle short and stout with 3 or more teeth 5 



Dististyle with only 1 or 2 teeth, or no teeth, often 



longer 6 



White submedian area of scutum usually extending back 

 to white prescutellar area; dististyle subquadrate, an 

 obtuse rounded angle between the lateral and apical 



margins; teeth small and set close together 



argus Williston 



Pale submedian areas of scutum fading out before 

 reaching prescutellar area; dististyle subtriangular, 

 the apicolateral margin a continuous curve; teeth 



larger and set farther apart vittatum Zetterstedt 



The white submedian areas of scutum visible in an 

 anterior view extending back to white prescutellar area 



trivittatum Malloch 



These white submedian areas, if present, not reaching 

 white or denuded prescutellar area although the dark 

 lines of this aspect may be white when viewed poste- 

 riorly 7 



Dististyle flat, quadrangular, with a distal internal 

 angle more or less prolonged toward the median line; 



dististyle smaller than the basistyle 8 



Dististyle more or less cylindrical, or if flattened 



distinctly longer than wide 10 



Median area of scutum broadly orange except for anter- 

 ior part venator Dyar and Shannon 



Median area of scutum not orange 9 



Thorax mostly velvety black; white submedian marks 

 extending back from anterior margin of scutum about 



1/3 of distance to scutellum bivittatum Malloch 



Thorax gray; white submedian marks on front of scutum 



not prolonged posteriorly griseum Coquillett 



.Dististyle with lateral angles which give a sinuous 

 appearance, not more than 3 times as long as wide and 

 without basal projection; ventral plate rather broad 

 with a strong, narrow median projection nearly 1/2 as 

 long as dististyle, and lateral, rounded rectangles 



virgatum Coquillett 



Dististyle with lateral margins more regular and/or 



ventral plate not so formed 11 



Dististyle more than 4 times as long as wide, narrowed 

 at basal 1/3; without basal process or pronounced 

 angle; ventral plate semicircular in shape with a median 



notch canadense Hearle 



Dististyle not more than 3 times as long as wide; not 

 narrowed at basal 1/3; if longer, then a basal process 

 present; ventral plate of various shapes but not semi- 

 circular 12 



Dististyle with a stout spine, sclerotized lobe, or 



distinct tube die at base internally 13 



Dististyle without a stout spine or distinct tubercle at 



the base 16 



Base of dististyle with a stout spine or horny pro- 

 jection internally 14 



Base of dististyle with a rounded lobe bearing short, 



stout, spinelike hairs internally 



tuberosum (Lundstroem) 



Basal prongs of ventral plate with short lateral pro- 

 jections; apex of adminiculum hyaline, the sides set 



off by a notch, hairy piperi Dyar and Shannon 



Basal prongs of ventral plate without lateral projec- 

 tions; if apex of ventral plate is smooth and pale it is 

 much longer and narrower 15 



