BASED ON A STUDY OF THE MALE GENITAL ARMATURE. 3.3 



somewhat triaugular in shape, and turned outwards, forming, with the one on the 

 opposite side, a median hibe-Hke projection (ml) : 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. mordtuns, and 

 ivnnediately within its marc/in 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 (A) 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. jMacfie 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 C 2 



