115 



Wart-hogs remain in the burnt areas, feeding on roots, and thus 

 probably furnish a source of food for newly-emerged flies. 



In stud^-ing the proportion of sexes among captured flies, it was 

 observed that male flies become attached to possible hosts in order to 

 secure females which come to feed. When the possible hosts rest, the 

 females are less attracted and most of the males fly off. Pairing is 

 attempted by the male whatever may be the stage of development 

 of the female. Collectors can readily obtain flies by catching them off 

 each other and these captures always show a small proportion of 

 females. If flies which have settled near the possible host are included, 

 the results show a much higher percentage of females. The number of 

 active G. morsitcms decreases during the hottest part of the dav. 

 Examination of possible sheltering places during this period showed 

 that large numbers of females are to be found in recesses in the trunk 

 and bark of large trees, especially baobabs, while the males occur in 

 more exposed positions. The proportion of females taken in the 

 ordinary way in morning and evening was 12 and 10 per cent, 

 respectively ; when taken at mid-day, mostly ofE trees, the proportion 

 was 43 "5 per cent. The following explanation is suggested for the 

 variations observed in the proportion of males and females captured 

 at different times of the day : — Males which have recently fed, attend 

 man to await the females which come to feed. The female may be 

 secured by a male, or if pregnant, may be driven off, and attempt to 

 feed later. After feeding, the female retires under cover of large trees 

 or to breeding places to protect itself from the males. It is almost 

 certain that the sexes exist in the same area in equal numbers. Attempts 

 to control the fly by systematic capture would be most successful if the 

 flies were taken off the trees at mid-day. Breeding was apparently 

 at its maximum at the time of investigation, i.e. in October 1915; 

 the pupal period averaged 21 days, as against 10 weeks in the dry 

 season. The same shortening of the developmental period was 

 observed in the case of Mutilla glossinae, E. tarsatus and Stomatoceras. 



In September 1915, a large area of territory in Nyasaland was thrown 

 open for free shooting in the behef that this measure would reduce the 

 tsetse-flies. The author is of the opinion that the desired result cannot 

 be obtained in this way, because the fly-area is continuous with areas 

 in North-Eastern Ehodesia, and the game may retire to Rhodesia 

 during the dry season, returning with the rains and bringing an abund- 

 ance of flies with it. 



In a supplementary report, further observations are made on the 

 resting habits of G. morsitans, on artificial breeding places, and on 

 parasites. Baobab trees were found to be preferred as resting places, 

 though any large trees were suitable. Birdhme traps placed in 

 recesses of the trees did not prove effective in capturing flies. Numerous 

 artificial breeding places were successfully established. At Rifu, 

 where 10 species of trees had been felled, no one of them was apparently 

 preferred. The results indicate the possiblity of checking the fly by 

 the estabhshment of artificial breeding places ; at Lingadzi the results 

 almost suggested that control could be carriecl out by ehminating only 

 the larger natural breeding places. This method might be used over 

 small areas, such as those in the vicinity of main roads and important 

 centres. The possibihties of the transfer of flies by moving game 



