BASED ON A STUDY OF THE MALE GENITAL ARMATURE. 35 
somewhat triangular in shape, and turned outwards, forming, with the one on the 
opposite side, a median lobe-like projection (m/); on the outer margin of each 
of these appendages, near the base of the curved portion is a minute tubercular 
process ; this curious little structure is evidently moveable as in many instances 
it is seen lying concealed in a cavity extending distally from its base; in some 
instances both are seen to lie in a recumbent position ; in other examples either 
one or both may stand erect at right angles to the basal attachment. The heel 
or posterior lateral angle is normally somewhat strongly produced and narrowly 
rounded ; but in two examples (shown separately in fig. 17) this process is more 
broadly rounded ; and in one instance it does not extend distally as far as the 
sub-median process ; the latter is never so prominent as it is in G. morsitans, and 
immediately within its margin is a long bristle which in the majority of specimens 
lies upon the surface of the clasper with its point towards the proximal or basal 
portion ; but for the sake of clearness it has been figured as seen in some few 
instances ; outer lateral margins concave and furnished with a series of very 
long slender bristles or hairs, becoming more numerous proximally and shortening 
gradually as they extend across the flat portion, finally merging into those 
which extend along the inner lateral margin. These are again succeeded by 
short black spines which project over the median processes ; these black spines 
also gradually diminish in size and merge into the minute ones extending 
along the posterior or distal margin as far as the submedian process. The 
most marked feature of the claspers is their general angular outline and the 
somewhat straight-cut appearance of the posterior margin ; these characters 
taken together with the form of the median pair of processes will serve at 
once to distinguish the genitalia of this insect from those of G. morsitans, 
and with a little practice the species may be separated unerringly by the aid 
of a lens having a magnification of 20 diameters only. Inferior claspers 
small and covered with minute hairs; these together with the juxta (/) and its 
appendages and also the harpes (h) are practically identical with the corre- 
sponding organs found in G. morsitans. 
It may be well to note that this insect has a marked tendency to become 
‘greasy, so that all trace of colour disappears. Dr. Macfie has also noticed 
the same tendency and says, in a letter, dated 7th October, 1910, Minna, 
Northern Nigeria, ‘‘ When I was at Baro last September, on Sleeping Sickness 
duty, I noticed one day (September 11th, 1910) that there were two distinct 
forms of what I supposed to be G. morsitans—the one dark, the other pale. 
The difference was quite noticeable when the flies settled on the ‘ boys’’ coats, 
and I was able to catch specimens of each variety. Unfortunately all my own 
specimens were destroyed by ants, but one of the dark specimens which I had 
given to Dr. Ingram remained. I was ordered off to Bida before I could get 
any more specimens, but on my return to Baro on September 24th, Dr. Ingram 
pointed out to me that the tsetse I had given him was almost absolutely black. 
It certainly was not black when I gave it to him. Some other specimens he and 
Dr. Morrison had collected a week before had similarly turned black, and it was 
at first supposed that the naphthaline used as a preservative was responsible for 
the remarkable change. But as all the specimens of G. morsitans taken had been 
treated alike, and only some half dozen had darkened, this could not be considered 
19127 C2 
