An analysis was made of the mating scar pattern of female Glossina palpalis palpalis Robineau-Desvoidy and Glossina fuscipes fuscipes Newstead. Measurements on fifty permanent preparations of the mating scars of females reared in the laboratory revealed significant differences in the length, width and in the distance between the centers of the mating scars of the two species. Plotting the distance between the centers of the two mating scars against the ratio width/length resulted in a 93% separation of the two species. It is proposed that this technique could be used during field surveys to expose possible cross-breeding in nature or as a tool in the entomological evaluation of a tsetse eradication campaign where one species is released in the habitat of the other.