100 H. C. EFFLATOUN. 



DIAGNOSIS:— An exceedingly common, rathor small, 

 narrow, almost bare fly, which can be at once recognised by the 

 absence of the vena spuria, the very thick hind femora, which are 

 serrate beneath and possessing individual strong spines and a large, 

 stout basal spine ; antennas dark brown. 



DESCRIPTION:— Male: Face as well as the frons entirely 

 covered with pure silvery white or pale yellowish-white dust, and 

 with a few white hairs on the lower part of the face at the sides ; 

 fare descending below the atennae in a gentle curve to the upper 

 mouth-edge, which is its most prominent part ; below this the face 

 retreats to the lower mouth-edge, and thence in a straight line to 

 the jowls ; the lower end of the vertex is thin and rather flat, 

 and about its middle it is a little wider owing to the incurved 

 margin of the eyes (but not so much as in Sphcerophoria) ; the 

 jowls and all the vertex are covered with pure silvery-white dust 

 and possess a few white hairs, but the uppermost part of the occi- 

 put (immediately behind the vertex) possesses a few yellowish 

 hairs, and the dust is usually greyish. Vertex long, possessing 

 silvery-white dust and a few hairs on the front half of the vertical 

 triangle, but with its hind or upper part black and bearing incons- 

 picuous yellowish pubescence. Frons quite small, little produced, 

 and quite free from pubescence. Eyes meet for a distance which 

 is somewhat longer than the length of the frons, with the facets 

 on the upper front part rather dilated. Antenna? with the two 

 basal joints blackish or reddish-brown but with the third joint 

 either entirely blackish or in great part black with the tip very 

 dark reddish-brown ; arista very dark reddish-brown, gradually 

 tapering towards the tip. All the three joints, especially the third 

 possess exceedingly fine whitish dust. 



Thorax rather dull black, thinly punctate and with the 

 postalar calli reddish-brown or dark brown, and with traces of 

 two lighter lines on the front part of the disc; the humeri and 

 the sides down to the suture, as well as the pleurae are covered 

 with dust which varies from pure silvery-white to whitish-grey ; in 

 the elongate hollow immediately above the postalar calli it is also 

 greyish. The pubescence is extremely fine, short and inconspicuous, 

 but fairly dense, even and uniformly pale. Scutellum very flat on 

 the disc and possessing short pale hairs with a few tiny incons- 

 picuous bristles at the tip. 



Abdomen with the basal segment dull black but greyish 

 on the two basal corners. The second segment is yellow, 

 with a broad triangular blackish band always present on 

 the lower margin ; the upper margin is usually yellow- like the 

 rest of the abdomen, but sometimes, it bears a small triangular 



