282 MR. J. O. WESTWOOD ON NYCTERIBIA. 
furnished with strong bristles ; they are all similarly formed, and of a similar size ; and 
the sexes appear to offer no variation in respect to their structure. They are inserted, 
as above stated, at the anterior and lateral margins of the thorax, the pectoral shield 
extending beneath their bases, so that their motions have necessarily an upward direc- 
tion. In the anterior pair the core are distinct, bristly, and somewhat elongated. I 
cannot, however, perceive in Colonel Sykes’s species the coronet of bristles noticed by 
M. Dufour as being placed at the extremity of the “‘ premier article de leur hanche;”’ but 
this part in the two hinder pairs is soldered to the sides of the thorax. The trochanter 
is very short; the femora are thickened and compressed, having a transverse im- 
pression before the middle of the limb, as indicating a rudimental articulation, The 
tibie are more slender, but not longer, than the femora, having three rudimental articu- 
lations towards the base, and not being furnished with spurs at the tips. The basal joint 
of the tarsi is very long, and appears to be annulated. The three following joints are very 
short, whilst the terminal one is much larger, and furnished with a pair of large pulvilli 
and two strong curved claws, dilated at the base beneath ; a small portion of the base 
of each claw being less crustaceous, and differently coloured from the remainder. 
Dr. Leach, regarding the cove as portions of the femora, and overlooking the tro- 
chanter, described the femora as composed of two joints. In like manner he regarded 
the long basal joint of the tarsi as a portion of the tibie, which he also described as two- 
jointed, while he considered the terminal joint of the tarsi as forming two joints, evi- 
dently regarding the differently-coloured base of the ungues as a distinct articulation, 
The structure of the abdomen and its appendages varies considerably in the sexes of 
Nycteribia as well as in the different species. This circumstance, united to the uncer- 
tainty as to the determination of the individuals of each sex, has been the source of 
great confusion in almost every description hitherto given of the genus. This con- 
fusion I am enabled, by the assistance of Colonel Sykes’s specimens, to clear up. I 
have said that these specimens were females in various stages of gestation. In none 
were traces of articulation visible on the upper surface except a single one at the base, 
which, on the under side, is very conspicuous, being flattened, horny, and of the same 
colour as the under side of the thorax, while the rest of the abdomen is coriaceous and 
of a dirty whitish colour. This segment is terminated by a transverse series of very 
strong and blunt black bristles, which exist in all the individuals of the genus which I 
have examined. By Dr. Leach and Mr. Curtis it was regarded as the postpectus ; but 
that it is a portion of the abdomen is evident by its terminal series of bristles being con- 
tinued laterally and extending a short distance across the upper surface of the base of 
the abdomen, as represented in my figures: indeed, sometimes, according to Latreille, 
it is entirely continuous, both on the upper and lower surface, at the extremity of this 
basal articulation. 
The abdomen itself is of an oval form and very convex when distended, being slightly 
a i 
