18 



CHAPTER III. 



THE FOUR GROUPS INTO WHICH TSETSE-FLIES 



ARE DIVIDED.— TABLES FOR THE DETERMINATION 



OF GROUPS AND SPECIES. 



In his recent paper on the male genital appendages* — one of 

 the most valuable contributions to our knowledge of the Tsetse- 

 flies yet published — Mr. Newstead has divided the genus Glossina 

 into three groups. In the present work this arrangement is 

 adopted in a somewhat modified form, since Glossina hrevipalpis, 

 Newst., and its immediate allies are removed from the Glossina 

 fiisca group, in which they are placed by Mr. Newstead, and 

 formed into a group by themselves. It is believed that this 

 arrangement represents a natural grouping, which will aid the 

 student in the identification of species. The following Tables are 

 based solely upon external characters, in the ordinary sense of 

 the term ; though of course subordinate in value to those 

 derived from the male genitalia, external characters have been 

 found by experience to be sufiicient for the determination of the 

 species recognised in this volume, while they possess the 

 additional advantage of being present in both sexes. The Tables 

 here given must not be regarded as anything more than a 

 series of " short cuts " to the determination of species ; the 

 characters mentioned are simply those that are most convenient 

 and easily recognisable for this purpose, and it must on no 

 account be imagined that these represent the only differences 

 between species. The detailed descriptions in the following 

 chapters are in all cases comparative, and at the end of the 

 account of each species the differences between it and its nearest 

 allies are specially emphasised under the heading " Affinities and 



* "A Revision of the Tsetse-Flies (Glossina), based on a Study of the 

 Male Genital Armature," by Robert Newstead, M.Sc, A.L.S., etc. 

 (Bulletin of Entomological Research, Vol. II, Part 1, pp. 'J-36, Figs. 1-17 

 (April, 1911).) 



