The commonest and widespread Holarctic species, 

 riparia Falldn, breeds in water ranging preferably 

 from fresh to brackish. The variety macellaria Egger 

 predominates in the southern part of the range of 

 riparia. E. cinerea Jones prefers denser waters, up 

 to saturation of salts, and is common in brine ponds 

 of salt works of the West Coast as well as in 

 saline lakes where it becomes extremely abundant. 

 There are several North American species which 

 breed locally in hot springs and geyser effluents. 

 The larvae (figs. 14:57e; 14:59a, c) of Ephydra are 

 found in the masses of blue-green algae on which 

 they feed, and also in the upper* layers of the algae- 

 covered bottom ooze in shallow water. The puparia 

 (fig. 14:596) are attached by means of the hooklike 

 last ventral pseudopod of the larva to sticks or debris, 

 when available, but in deeper waters they usually 

 float in large masses on the surface. 



Key to Adults of the California Species of Ephydra 



1. Pollinose vestiture of the body white or gray 2 



— Pollinose vestiture of the body brassy to greenish 

 3 



2. Tibiae dark, contrasting with the bright yellow tarsi; 

 scutellum polished; hind cross vein oblique to the 

 costa; Inyo County auripes Aldrich 1912 



— Tibiae yellowish, concolorous with the tarsi; scutellum 

 pollinose; hind cross vein perpendicular to the costa; 

 southern and central California cinerea Jones 1906 



3. Legs mostly dark greenish; California 



riparia Fallen 1813 



— Legs mostly yellowish (pale southern variety) .... 



riparia var. macellaria Egger 1862 



Genus Coenia Robineau-Desvoidy 



rhe larvae of Coenia fumosa Stenhammar, a European 

 salt-water species, have been described by Beyer 

 1939). 



turbida Curran 1927. 



Inyo, San Diego 



Key to Adults of the California Species of 

 Paracoenia 



1. Acrostichal setulae nonseriate; hind cross vein sinuate; 

 scutellum distinctly convex; central and southern 

 California bisetosa (Coquillett) 1902 



— Acrostichal setulae in 2 distinct series; hind cross 

 vein straight; scutellum flattened; Sierra Nevada 

 platypelta Cresson 1935 



Tribe SCATELLINI 



Genus Scatophila Becker 



3olwig (1940) has given a fine discussion, including 

 ietailed figures of the immature stages of Scatophila 

 micornis Czerny, which he found living on wet stones 

 and wet flowerpots in greenhouses in Denmark. The 

 larvae feed on diatoms and protect themselves by 



473 

 Wirth and Stone: Diptera 



covering their bodies with sand grains and pollets 

 of feces. 



Key to Adults of the California Species of Scatophila" 



1. Marginal cell with 2 or more distinct white spots; male 

 face with a snoutlike protuberance medianly below; 

 Los Angeles and Santa Barbara counties, in green- 

 house) unicornis Czerny 1900 



— Marginal cell unspotted, or with a single weak basal 

 white area, or wings very pale and not appearing 

 spotted 2 



2. Large quadrate median white spot of submarginal cell 

 with a prominent dark central area; Los Angeles and 

 Riverside counties 



pulchra Sturtevant and Wheeler 1954 



— Median white area of submarginal cell without a darker 

 ce nter 3 



3. The larger facial bristle on outer lower corner turned 

 upward and outward, Scatella-like; middle femora of 

 male armed with a row of short spines along inner side; 

 widespread despecta (Haliday) 1839 



— Lower facial not pointed upward and outward; middle 

 femora of male lacking a row of spines 4 



4. Body color mostly whitish to grayish white, usually 

 with some darker markings, the disc of scutellum 

 largely to entirely whitish 5 



— Body color tan, brown, or black, usually with some 

 lighter markings, the scutellar disc largely dark but 

 often with basal and sometimes with apical gray areas 

 8 



5. Male face flat or concave in middle, with 2nd antonnal 

 segment thickly haired along inner side; female face 

 with a pair of diverging setae on upper carina (dis- 

 juncta) or not (arenaria) 6 



— Male face prominently convex medianly, the 2nd anten- 

 nal segment with sparse hairs; female face without a 

 pair of diverging setae on upper carina 7 



6. Male face flat to slightly concave medianly but not 

 membranous, the 2-3 stronger hairs on margin at each 

 side rather pale and weak; nearly uniformly whitish 

 species, the abdomen mostly whitish dusted; female 

 face silvery gray, the cheek width greater than width 

 of 3rd antennal segment; Mono county 



arenaria Cresson 1935 



— Male face concave, membranous medianly behind oral 

 margin, with 2-3 stout black bristles on each side 

 which are stronger than those of arenaria; less whitish, 

 especially on abdomen; female face with a pair of 

 diverging setae on upper carina; central California 

 disjuncta Cresson 1935 



7. Male face evenly arched in middle, thickly haired, 

 especially in 2 large lateral clusters in which 3-5 are 

 stronger; wing spots distinct, including apical spot 

 of submarginal cell; female face gray with some brown- 

 ish discoloration; Kern County to Riverside and Orange 

 counties bipiliaris Sturtevant and Wheeler 1954 



— Male face protuberant, the median part forming a broad 

 cone which involves the oral margin, the cone sur- 

 rounded by clustered hairs except at margin; wing 

 spots rather indistinct; female face silvery gray, the 

 cheek width about equaling width of 3rd antennal 

 segment; Humboldt County 



conifera Sturtevant and Wheeler 1954 



8. Acrostichal hairs of uniform size, in 2 regular rows 

 reaching nearly to scutellum; tannish species with 

 mesonotal pattern not or badly evident; reclinate 

 orbitals far forward, 3-4 times as far from inner verti- 

 cals as the latter are from the outer verticals; southern 

 and central California 



ordinaria Sturtevant and Wheeler 1954 



"From Sturtevant and Wheeler, 1954. 



