DIPTERA 185 



diseases as sleeping sickness and malaria in man. In the west 

 of Uganda, since sleeping sickness was first noticed in 1901, more 

 than 200,000 people have died of it. Of the 300,000 natives who 

 inhabited the shores of the beautiful Victoria Nyanza, fewer than 

 100,000 remain, the rest having perished from this terrible disease. 

 In every case sleeping sickness has been transmitted from one 

 victim to another by the bite of a dipterous fly, the Tsetse Fly, 

 or Glossina palpalis. Malaria and yellow fever are diseases which 

 can only be transmitted from man to man through the bite of 

 certain mosquitoes or gnats ; while rinderpest, nagana, surra, gall- 

 sickness, diseases of cattle, horses, mules, and camels in the tropics, 

 are all transmitted to those animals through the agency of biting 

 flies. 1 



The Mosquito passes the larval and active pupa stages of its 

 life in stagnant pools and collections of water. As a larva it rises 

 tail first to the surface to breathe, sticking out through the surface 

 film of water its curious breathing-tube which is placed at the end 

 of the body, and at almost right-angles to the tail. In the pupa 

 stage it rises head-first to the surface, the respiratory apparatus of 

 two short tubes now appearing on the back of the insect. As it is 

 impossible for the Mosquito during these stages of its life to 

 breathe except by rising to the surface of the water to take in a 

 fresh supply of air, this is the period of its existence when it is 

 most easily destroyed; and this is successfully accomplished by 

 pouring any crude oil on the water infested by Mosquito larvae and 

 pupae, so as to form a perfect unbroken film of oil over the whole 

 surface, through which the insects find it impossible to thrust their 

 breathing-tubes, and consequently quickly drown. 



The Common House-Fly, after feasting, upon all sorts of unspeak- 

 able filth and garbage, so that the hairs which clothe its feet, legs, 

 head, and body have become laden with disease germs, enters the 

 house and at once walks over any food that may be exposed, falling 

 into the milk as likely as not, and contaminating everything it 

 touches. During the warm summer days every precaution should 

 be taken to prevent flies from entering rooms or settling upon food, 

 while all house refuse likely to harbour these pests in their larval 

 stage should be promptly destroyed. 



r R 1 See the author's lecture on " The Economic Importance of a Study of Insect 

 Life," vol. Ivi., p. 688, " Journal of Royal Society of Arts." 



