200 THE CANADIAN ENTOMOLOGIST. 



black ; pile of pleura and scutellura white, the four bristles of the latter 

 black. Abdomen whitish pollinose, that at the base of the second, third 

 and fourth segments blackish-gray ; pile of abdomen, venter and femora 

 white, a few on the hypopygium black ; short pile of tibiae and tarsi, like 

 all the bristies of the legs, black. Wings, including the space between 

 costa and auxiliary vein, grayish-hyaline, veins black, narrowly bordered 

 with brown ; stigma dark brown, fourth posterior cell narrowly open, or 

 closed and short petiolate. 



9 same as the $ , with these exceptions : Front dark-brown pollinose 

 on the upper part, and near the middle marked with two large rounded 

 velvet-black spots contiguous to the eyes ; eighth and ninth abdominal 

 segments shining, their pile largely black. 



Length, 7 to 1 1 mm. Los Angeles County, California. Nine males 

 and seven females, March to May. 



Thereva novella, n. sp. $ same as otiosa, with these exceptions : 

 Style of antennae two-fifths as long as the third joint ; pile and bristles of 

 vertex and bristles of occiput yellowish-white ; thorax destitute of black 

 pile ; knob of halteres brown, margined with yellow ; veins of wings 

 largely yellow, stigma also yellow and indistinct. 



9 differs from the $ of otiosa, besides in the particulars above 

 mentioned, in that the front is destitute of the two round velvet-black 

 spots, having instead a narrow, interrupted, dark-brown cross-band ; 

 eighth abdominal segment opaque pollinose, its pile largely yellow. 



Length, S to 1 1 mm. Los Angeles County, California. Five males 

 and one female. 



Thereva Johnsoni, n..sp. $ black, base of third antennal joint, 

 tibiae, and base of tarsi, reddish. Head yellowish-gray pollinose, front 

 with two transversely oval shining-black spots on its middle ; pile of head 

 pale yellow, that of the front mixed with black, bristles of occiput and of 

 the antennas black. First joint of antennae slender, scarcely wider than 

 the second, third joint lanceolate, one and a half times as wide as the 

 second, three-fourths as long as the first joint ; style one-fifth as long as 

 the third joint. Thorax yellowish pollinose, marked with two light gray 

 vittae, the sides a purer gray ; pile of thorax and scutellum pale yellow, 

 less than half as long as the black bristles, a few black pile on the thorax; 

 pleura gray pollinose and yellowish-white pilose. Knob of halteres 

 brown. Abdominal segments one to six uniformly yellowish-gray pol- 

 linose and short yellow pilose, the seventh and following segments shin- 



