PREFACE. 



The discovery that the germs ot several of the most 

 important tropical diseases, namely, malarial fever, yellow 

 fever, and elephantiasis, are inoculated into human beings 

 by the bites of mosquitoes has revolutionised tropical 

 hygiene. Not only our comfort but our security in the 

 tropics now depends upon the measures we adopt against 

 these insects. 



There are several means of protection already well 

 known to us. For example, in India punkahs swing night 

 and day over the heads of Europeans, and at night almost 

 everyone employs mosquito nets. In America entire 

 houses are protected from the invasion of these pests by 

 means of wire gauze screens fixed to the windows and 

 doors. 



Such measures as these, however, have one great defect. 

 They protect only those who can afford them, and who are 

 necessarily few in number. Moreover, it is found in prac- 

 tice that the protection is only partial, because, whatever 

 efforts of this kind we may make, we cannot, especially in 

 the tropics, entirely avoid being bitten. 



Another safeguard against mosquito-borne diseases 

 consists in isolating ourselves in buildings separate from 

 the bulk of our neighbours, in the hope that, even if we 

 continue to be bitten by mosquitoes, these insects will not 



