424 Mr. Hugh Scott on a large series of 
of the large tubercles on the bare space in the centre of 
the dorsal surface of the abdomen. Westwood described 
and figured them as being 4 in number, arranged as at 
the corners of a square. This is the most usual con- 
dition, and is found in some allied species. Sometimes, 
however, one tubercle is out of place, and the grouping 
irregular; and the number is not constant. Thus out of 
the 43 Ceylon females (see Text-fig. 1) :— 
34 females have the big tubercles 4 in number (Fig. 1, 
a), in some cases irregularly arranged. 
4 females have 5 big tubercles (Fig. 1, 0), with a more 
or less regular pentagonal arrangement. 
1 female has 6 big tubercles (Fig. 1, ¢), irregularly 
arranged. 
1 female has 7 big tubercles (Fig. 1, @), very irregu- 
larly placed, in an anterior group of 4 and a 
posterior group of 3.* 
Fia. 1.—Diagrams of the dorsal surface of the penultimate abdominal segment, ? 
of C. sykesi Westw. to show variation*in the arrangement of the large black tubercles. 
These varying specimens show no departure from the 
normal condition, except in regard to the number and 
position of these tubercles. The result of the investigation 
is important, since it shows that the number of the 
tubercles cannot be relied on as a specific character. 
Enderlein has described the only female out of 7 speci- 
mens from the Maldive Islands. According to his descrip- 
tion, it corresponds closely to a typical female of C. 
sykest, except in having 5 tubercles instead of 4 on the 
* The number of big tubercles is also sometimes reduced by 
variation to below the normal. I have examined 7 other specimens 
of C. sykesi now in the Cambridge Museum, collected in Ceylon in 
1877. Three are females, and while 2 of them have the normal 
4 tubercles, the third has only 2 big tubercles, placed transversely. 
