298 J. J. SIMPSON — COLOUR CONVENTIONS TO INDICATE THE DISTRIBUTION 



futility of assigning to each a colour or shade which will be sufficiently distinctive, 

 the most satisfactory solution will be to adopt a few distinct colours for groups 

 and variations in the shajDe of the symbol for individual species. 



The following scheme has been drawn up on this basis and has been used in 

 the maps accompanying my reports. I may also say that in the preparation of 

 the scheme I have consulted Dr. A. G. Bagshawe, the Editor of the Bulletin of 

 the vSleeping Sickness Bureau, and also Mr. Guy A. K. Marshall, the Editor 

 of tliis Bulletin, and that the system will be adopted in any further maps which 

 may be published ia colour in either of these Journals. 



Symhols. — To achieve their aiin these ought not to be excessive in number 

 and should be sufficiently distinctive to be easily recognisable from one another, 

 at a glance. After a series of trials the following have been considered most 

 satisfactory : — (1) a solid circle, (2) a solid square, (3) a circle enclosing a cross, 

 (4) a square enclosing a cross, (5) a solid triangle, (6) a hollow triangle, (7) a 

 hollow circle, and (8) a hollow square. Modifications of these could easily be. 

 multiplied (.?<■(?, Plate VI). In the present system it is not necessary to adopt any 

 mpre, as only in one group, namely the palpal! s-gvo\\\) of Glossina, in which there 

 are six species, do we require more than four symbols. 



Colours. — Eed has already been assigned to sleeping sickness, and it seems 

 most advisable to retain its use for this disease. By means of the symbols 

 already given it is easily possible to represent other diseases, if necessary, by the 

 same colour. 



In the case of Glossina soiae sort of groiqjing !^is necessary, and separate 

 colours should be adopted for these groups. Mr. E. E. Austen in his recent 

 work* on this genus divides the vaiious species into four groups, and although 

 there may be a difference of opinion as to the relative values of these from a 

 taxonomic point of view, the arrangement forms a good basis for the purpose in 

 hand and obviates the necessity of introducing too large a number of symbols. 

 Consequently I have adopted it in this system and have added the various 

 controversial and new species since described in their respective groups. 



The following colours have been selected after a series of tests as being 

 sufficiently distinct to avoid unnecessary confusion and have been assigned to the 

 various groups as follows : — 



palpalis-growp — blue ; 



lyioi'sitans-gvoxi]) — green ; 



fiisca-group — brown ; 



by-evipalpis-gvowp — orange, t 



It is unnecessary here to enter into the details of the various species as I have 

 already explained the different symbols used and the application of these can 

 easily be seen at a glance on the accompanying plate. 



••"■ A Handbook of the Tsetse-Flies, 1911, pp. 19, 20. 



t Yellow has been purposely avoided as it is never very distinct, while in artificial light it is 

 hardly recognisable. 



