141 



Problem in North Mossurise, Portuguese East Africa " (145). " Late 

 burning/' writes this author, "is no emergency measure aganst fly. 

 In some areas especially, where the grass is already well reduced, its 

 full effects may take long to show. Again, its abandonment will mean 

 the return of the old conditions, for the underground stumps and roots 

 of pyrophytes are extraordinarily tenacious of life. It must be 

 regarded as a piece of administrative policy and be kept up annually. 

 That its adoption is necessary I am quite convinced, if only for the 

 reason that the country generally [i.e. North Mossurise] is at present 

 reverting more and more to wooding and becoming increasingly fitted 

 for tsetse, even in those areas in which the cover has hitherto been 

 sparse and light. The recommendation of the measure, in face of its 

 having to be kept up indefinitely, must be that the fires take place in 

 ! any case and that the annual cost of regulating them will be trivial. 

 The latter may even be met by the fines imposed on unauthorised 

 burners, and the actual burning, being done at a signal by the kraal 

 natives themselves, will cost nothing. 



" Apart from the prophylactic .value of the measure just mentioned, 



its effect, grass conditions being equal (which they are not), should show 



, first and chiefly in relation to G. brevipalpis and (in the area in which 



! this fly depends mainly on coppice) pallidipes. It will not affect the 



grown pyrophytic trees in any wholesale manner (unless in a very 



I exceptional season or unless they are weakened by ring-barking). Its 



' effect in relation to morsitans might even be regarded as problematical, 



! for that fly and pallidipes in the same wooding appear to be independent 



of undergrowth. The systematic burning back of smallish growth will 



assuredly tell as the established trees pass maturity and eventually 



go, with nothing to replace them, but the time involved will be long." 



In concluding this paper, Swynnerton writes : " I wish, therefore, 



to make it the one outstanding recommendation of this report that late 



burning with, very frequently indeed, a year of no burning should 



be given a trial over a considerable number of years ; also that, in the 



first season at any rate, an effort should be made to have the burning 



as simultaneous as possible over a large block." 



As regards the value of grass burning as a means of attack against 

 G. morsitans in Southern Rhodesia, views recently expressed by R. W. 

 Jack are similar to those of Dr. Lamborn quoted above (p. 140) with 

 reference to conditions in Nyasaland. It is pointed out by Jack (75) 

 that several investigators have emphasised the efficacy of grass fires 

 in reducing the numbers of the fly. He himself, however, " has been 

 unable to obtain the slightest evidence " in support of this theory ; 

 "indeed the evidence to the contrary is almost conclusive." If the 

 fly " could not avoid grass fires," it would seem impossible that the 

 species could escape extermination " in parts of the country inhabited 

 by natives." The mopani belts, where the grass remains short, are 

 probably, this author thinks, a convenient refuge from grass fires in 

 the dry season, and are also attractive to game after the onset of 

 the rains. 



CATCHING AND SYSTEMATICALLY TRAPPING TSETSE-FLIES. It is 

 obvious that in the case of a fly like Glossina, with feeble powers of 

 reproduction, catching the adults ought to produce a relatively much 

 more satisfactory effect than in that of a prolific insect such as the 

 House-fly, which is capable of producing from 600 to 900 eggs in the 

 course of its life. During recent years various attempts at catching 



