There are certain frequently observed and rather mysterious phenomena associated with the bionomics of the better known species of Glossina; such, for example, as the local disparity between the sexes and the apparently arbitrary distribution of the fly. It is difficult, if not impossible, to explain these, or at least no explanation has yet been put forward which is wholly in agreement with all that has been recorded of the subject. It appears necessary in consequence to consider some part of the generally accepted bionomic history of these liies as being based on insufficient evidence.