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 shape 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 Sleeping Sickness Bureau, and also Mr. Guy A. K. Marshall, the Editor 
of this Bulletin, and that the system will be adopted in any further maps which 
may be published in colour in either of these Journals. 
Symbols—To achieve their aim these ought not to be excessive in number 
and should be sufficiently distinctive to be easily recognisable from one another 
ata 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 (see Plate VI). In the present system it is not necessary to adopt any 
more, as only in one group, namely the palpalis-group of Glossina, in which there 
are six species, do we require more than four symbols. 
Colours.—Red 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 some sort of grouping ‘is necessary, and separate 
colours should be adopted for these groups. Mr. EK. EH. Austen in his recent 
work* on this genus divides the various 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-eroup—blue ; 
morsitans-@roup—green ; 
fusca-group—brown ; 
brevipalpis-group—orange.} 
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-Ilies, 1911, pp. 19, 20. 
+ Yellow has been purposely avoided as it is never very distinct, while in artificial light it is 
hardly recognisable, 
