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species as host. Their reproductive power, moreover, is very great, 

 and when, as the result of exceptionally favourable circumstances, their 

 host multiplies to an abnormal extent, they are capable of completely 

 arresting its invasion. 



PREDATORY ENEMIES OF TSETSE-FLIES. The predatory enemies of 

 Tsetse-flies include vertebrates (mammals, birds and reptiles), arachnids, 

 and certain insects . We will begin by taking the role of the vertebrates . 



Reference has already been made (see p. 90) to the experiments 

 carried out by Mr. LI. Lloyd at Ngoa in order to determine the relation 

 of G. morsitans to the smaller animals mammals, birds, reptiles and 

 amphibians In the course of these experiments it was found that, in 

 the majority of instances, small animals of this kind in captivity, when 

 attacked by captive Tsetse, succeeded in catching and devouring them, 

 provided, of course, that the animals were awake. 



It is therefore important to observe and note carefully everything 

 relating the pursuit of Tsetse-flies by small mammals, birds, reptiles 

 and amphibians, whether insectivorous or omnivorous. 



Practically nothing is known at present as to the habits and food of 

 tropical insectivorous bats, particularly those of Central Africa. This 

 also applies to the part played by these animals in the destruction of 

 noxious insects, particularly blood-sucking Diptera. We do not know 

 whether they are capable of devouring Tsetse-flies, and since bats are 

 nocturnal animals and fly fairly high in the air, while Tsetse-flies 

 are seldom- on the wing by night and rest close to the ground, there 

 are doubts on the subject. The role of bats in the destruction of 

 mosquitos is by some writers regarded as important, and Dr. C. A. Q. 

 Campbell, of San Antonio (Texas), who made a special study of bats 

 as destroyers of these insects, of which, he states, they are the most 

 inveterate enemies, concludes from analysis of the droppings that a 

 single bat devours about 500 mosquitos per day. 1 It would be well 

 therefore to learn more of the natural history of Central African bats. 



What has been said with regard to bats may apply equally well to 

 all the other insectivorous mammals, as well as to insectivorous birds, 



1 At the beginning of 1911 Dr. C. A. Q. Campbell established a roosting- 

 place or shelter for bats, constructed according to his own designs, in a place near 

 San Antonio where mosquitos were abundant. In August the number of bats 

 -entering the roost was estimated at several hundred, and the creatures took 

 twenty minutes to enter; in 1912 the number of bats inhabiting the roost was 

 .so great (500,000), that they were several hours in leaving it ; as a result, the local 

 mosquito population soon showed a great reduction. The breeding of bats is 

 therefore useful from a hygienic standpoint, and its commercial side is not 

 to be despised, either, since the roosts are capable of furnishing a considerable 

 quantity of bat-guano. ' It should, however, be stated that Dr. Campbell's 

 belief in the value of bats as mosquito destroyers is not shared by Dr. L. O. 

 Howard. Writing on " Mosquitoes and Bats " (Public Health Repts., Washing- 

 ion, D.C., xxxv, no. 31, pp. 1789-1795, 30 July 1920), Dr. Howard cites evidence 

 showing that mosquitos do not form a large proportion of the diet of bats, that 

 only a very few species of bat are gregarious, and that no diminution in the 

 numbers of mosquitos or in the amount of malaria was observed in certain 

 localities in the United States where bats were swarming. In connection with 

 mosquito reduction, Dr. Howard does not think that bat roosts are sufficiently 

 promising to justify the expenditure of public money upon them. 



In all probability bats do not suffer from the bites of mosquitos, Tsetse-flies 

 and other blood-sucking Diptera, owing to the peculiar conformation of the coat 

 of hair with which their bodies are covered, and their special odour. They also 

 appear to be little subject to disease, since, in the caves in which they live in 

 enormous numbers, packed one against the other or even hanging in clusters, 

 the collectors of guano very rarely find a dead bat. 



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