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COLOUR CONVENTIONS TO INDICATE THE DISTRIBUTION 

 OF BLOOD-SUCKING INSECTS AND THE DISEASES 

 THEY TRANSMIT. 



By Jas. J. Simpson, M.A., D.Sc. 

 (Plate VI.) 



The necessity for graphic representation of the distribution of insects and the 

 diseases which are transmitted by them is now so evident as to need no special 

 demonstration. But it is further obviously important that some uniform method 

 should be adopted in the preparation of such maps, in order to make them inter- 

 comparable, and the object of the present notes is to suggest a comprehensive 

 system of notation for the whole genus Glossina — a system which may be readily 

 adapted for use in other genera or families of blood-sucking insects. 



The only scheme hitherto adopted was that used in the maps published by the 

 Sleeping Sickness Bureau in which red was restricted to sleeping sickness, brown 

 to Glossina tachinoides, blue to Glossina palpalis, green to Glossina morsitans and 

 G. pallidipes, and yellow to Glossina fusca. At the time when that scheme was 

 formulated the recognised species of Glossina were much fewer than at present 

 and their bionomics were less perfectly known. Further, the records of Glossina 

 morsitans and G. pallidipes were not sufficiently exact to permit of discrimination 

 between the two species and one colour had consequently to be used to include 

 both. 



Recent work has shown more emphatically than ever that such distinctions are 

 not only advisable, but necessary, and this, combined with the fact that several 

 new species have recently been described, renders it impossible to assign to each 

 of the species a definite colour sufficiently distinctive to avoid confusion. This 

 wUl be at once evident when it is remembered that there are, at present, seventeen 

 species of Glossina more or less universally recognised. Some of them are, 

 however, subjects of controversy, but until such disputes are definitely settled we 

 must take note of them separately. Moreover, in the event of any so-called 

 species being either submerged or proved to be distinct, it will be much easier, 

 and lead to less confusion, to group two series of conventions, already published, 

 into one, than to divide one series into two or more. In fact, the latter procedure 

 is possible only after a re-examination of all the specimens so recorded — an 

 almost impossible task. 



So far, only sleeping sickness and Glossina have been considered, but it may 

 be found advisable also to record graphically other diseases and their carriers, 

 for example, yellow fever and Stegomyia fasciata . For the present it is proposed to 

 deal only with the former, but it will be evident that should maps be required 

 for the latter a similar system of notation could be employed. 



If we recognise, therefore, the necessity for representing graphically the 

 distribution of sleeping sickness and of seventeen species of Glossina and the 

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