38 INSECTS AND HUMAN WELFARE 



Trypanosomiasis is a general term for diseases like sleeping 

 sickness due to trypanosomes and there are many diseases of 

 this type, among which may be mentioned an old-world 

 affection of horses known as Surra; an African one, Nagana, 

 that attacks other domestic animals as well; and a South 

 American type termed Mai de Caderas. Flies are the insects 

 implicated in the transmission of these diseases, mainly the 

 large tabanid horse flies and the smaller stable-flies of the 

 genus Stomoxys. Surra has been introduced into the United 

 States, but was successfully stamped out before it had be- 

 come established. 



Among bacterial diseases of animals, anthrax may be men- 

 tioned as one which is sometimes transmitted by biting flies, 

 the insects acting as mechanical or contaminative carriers 

 only. 



The foregoing enumeration of insect-borne diseases is by 

 no means complete. Indeed, it would be well-nigh impossible 

 to make it so, in view of the rapid strides which are being 

 made at the present time toward a knowledge of these many 

 problems which bear on the question of public health. New 

 discoveries are being rapidly announced in all parts of the 

 world, and while it is difficult to see how the fundamentally 

 important revelations of the past twenty years can be 

 equalled in the near future, we should be very unwise to pre- 

 dict that they will not be exceeded. 



