Nycteribiide, parasitie Diptera, from Ceylon. 427 
strong black teeth of the ctenidium on its hind margin. 2nd and 
3rd segments each bearing on its surface 3 rows of somewhat 
longer bristles, and on its hind margin a row of moderately long 
bristles quite continuous across the body, 4th segment somewhat 
elongated, its median portion without bristles, the lateral parts 
bearing bristles; in the middle of its hind margin is the small 
ctenidium of about 10 short, blunt, black teeth; on either side 
of this the margin bears long bristles. At the sides of the body, 
on segments 2, 3, and 4, are some stiff bristles projecting outwards, 
Anal seqment (Text-fig. 2). Narrow, long, tapering towards 
apex. Length 14, or more, times as great as breadth at base ; 
breadth at apex } as great as that at base. Median part of dorsal 
surface bare; lateral portions with bristles, which extend on to 
the ventral surface ; apical angles bearing longer bristles. Claspers 
long, narrow, narrowly-pointed ; reaching back almost, or quite, to 
the hind margin of the penultimate segment ; bearing long bristles 
on their basal parts. The median portion of each clasper is slightly 
curved away from the body, so that a small space is sometimes left 
between the claspers and the abdomen; their apices rest on the 
surface of the abdomen. 
b. 
a. 
Fria, 2.—(a) Dorsal view of anal segment of ¢@, (+) ventral view. In 6, owing to 
curvative of the segment, the latter looks shorter than it really is. 
AMOUNT OF VARIATION. The 57 males exhibit no 
appreciable variation in size, structure, or colour; except, 
in the case of colour, that due to differences in the degree 
of maturity. It can therefore be said, in summing up, of 
the whole series of males and females, 100 specimens, 
that the characters are remarkably constant. There is 
only one striking variation, which is that already described 
in the female. 
