The hypothesis which I have previously suggested, that the limit of morsitans coincides more or less with that of the park (at least in Katanga), has just been confirmed by several new observations.. But sometimes the range of the fly terminates before the disappearance of the park. This double disappearance is generally gradual.

Between 9° and 5° S. Lat. the western limits of the park and of G. morsitans coincide roughly with the Lualaba-Lomami watershed, but most frequently they disappear a little to the east of this line, that is to say, they do not quite reach the Lomami basin.

In this region, between the Lualaba and the Lomami, the park and morsitans gradually disappear in the neighbourhood of 5·30° S. Lat., that is, a little south of Kongolo.