95 



THE BIONOMICS OF GLOSSINA; A REVIEW WITH 

 HYPOTHETICAL CONCLUSIONS. 



By William F. Fiske. 



There are certain frequently observed and rather mysterious phenomena 

 associated with the bionomics of the better known species of Glossina ; such, for 

 example, as the local disparity between the sexes and the apparently arbitrary 

 distribution of the fly. It is difficult, if not impossible, to explain these, or at 

 least no explanation has yet been put forward which is wholly in agreement with 

 all that has been recorded of the subject. It appears necessary in consequence 

 to consider some part of the generally accepted bionomic history of these flies as 

 being based on insufficient evidence. 



That which is here attempted is to locate the source of possible error, and to 

 formulate an hypothetical bionomic history which shall explain the curious 

 phenomena above mentioned, and which shall remain closely in accord with 

 generally accepted theories. Any conclusions reached by such processes are of 

 necessity purely tentative, and they are only of value as they invite criticism and 

 discussion, or suggest new lines of research. 



Character of recorded Movements of Glossina from place to place. 



Three types of concerted movement from place to place are recorded of 

 Glossina. Roubaud, in the Report of the French Commission, and subsequently, 

 notes a seasonal migration of G. palpalis from permanent " belts " on the banks 

 of large streams, to temporary " belts " on the banks of small, intermittently 

 flowing streams, these latter being infested only during the rainy season. Various 

 other observers, notably Macfie,* have commented upon this same type of 

 migration, which appears to be characteristic of several and perhaps most species 

 of Glossina. These movements are directly governed by the seasons, and are 

 begun and completed within a calendar year. 



In Rhodesia there is evidence that some years ago G. morsitans was overtaken 

 by a widespread calamity, apparently associated with the destruction of certain 

 game animals by rinderpest. At all events it disappeared from many localities 

 where previously it abounded. Later reports from this region indicate that it is 

 gradually recovering portions, at least, of the lost ground. This is indicative of 

 quite a different type of concerted migratory movement, which is not governed 

 by the seasons, but by something else, and which may not be completed for many 

 years. 



The third type of concerted movement is recorded by Dr. Bagshawe, who, in 

 the course of a series of flight experiments, demonstrated that the flies were con- 

 stantly moving about from place to place within infested territory. These move- 

 ments were general, and a mile or more in two days was frequently covered by 

 individuals of either sex. He found that the flies passed both up and down a 



• Bull. Ent. Research III, May 1912, p. Gl. 

 (31313—2.) Wt. P 12—42. 1000. 9/13. D & S. 



