CHASMOMMA. 103 
hind tibia arched, much shorter than the femora; tarsi simple. 
Wings with the marginal cell broadly open; the third vein with a 
deep but broad kink, exactly as in Tropidia fasciata ; middle cross- 
vein just above the middle of the discal cell; vena spuria strong, 
but not entirely chitinised ; distal extremity of first posterior ceil 
shaped as in Xylota; lower corner of the discal cell rounded and 
without an appendix ; all the veins bare. 
Type: the tollowing new species. 
110. Chasmomma femoratum, sp. n 
3 2. Length of the body 7-8 mm. 
An interesting insect, strongly resembling Xylota femorata, L., 
but less than half its size. 
Head shining neous black, the occiput and frons in both sexes 
as far as the middle velvety black and dull; face witha faint white 

Fig. 16.—Chasmomma femoratum, sp.n. Q. X44. 
pollen, but the median tubercle shining black; frons and sides of 
face bearing very thin and rather long greyish hairs ; occipital 
border narrowly argenteous behind; antenne black, brownisl: 
towards the base. fy eke wholly make somewhat shining, with 
whitish pollen at the sides, on the usin and along the Meee se 
suture; the back is almost bare; pleure partly whitish pollinose, 
with rather short pale hair. Squamulze small, white; halteres 
whitish. Abdomen bluish black, shining, with the following dull 
black markings: a rounded spot on each side of the first segment; 
second segment with a median longitudinal band, dilated into a 
transverse band in front and behind, the posterior brn being some- 
what removed from the hind hoses: third and fourth seements 
with a similar pattern, which is, however, less distinct especially on 
the fourth: these patterns are more clearly defined and broader in 
