INSECTS AND DISEASE 



225 



it, they inject a little saliva, which causes the usual irritation and 

 swelling of a mosquito bite. 

 Disease Transmission. This would be bad enough, but it has 



SOURCE 

 Nasal discharges 

 Open sores 



DISEASE HOW ENTERS MAN 



Carcasses 

 Sputum 



Privies 1 

 Manure} 



infantile paralysis 



optha/mia 



syphi/is 



yaws 



anthrax 



faberca/osis 

 typ/io/d 



diarrhoea 

 Cfio/era 



tapeworm 



Open jore 

 rood 



SWAT THE: 



FIRST 

 FLY 



2S9Z0OOO 



rfy lays /ZO e0QS 



MAY 10. 60 Hits lay 

 MAYZO. 3600 Hies fay 

 MAY3O.ZI6OOO F/itt /ay 

 JUNE /O. I Zf 60000 Hie* /ay 



JUA/EZO-77000O00 Flies lay 933/2.0O00O0 e<&S 

 "JUME 30-304665600000 f/tes /ay JS987Z00OO000 e&S 

 = JULY 9- 279 9 J6 0000000 r/ies /ay 3ZS9Z3ZOOOOOO00 e<?&S 

 JULY 1 1- 167^6/600000000 Flies lay 2O/ SSJ9&OO OOOOOOO eggS 



JUL Y 2 c l-/00'r 76 <3600O0o0OOO Flies lay /1093ZJ JX.00O0006OOO e#0S 



AUGUST S-60466/760000O0OOO0Flie3 lay 7'<3'>5 e: i4/l2O00OO0O0000 Sf&S 



FIG. 76. 



Upper. Diagram showing, the relation of flies to disease. 

 Lower. Cartoon from newspaper showing rate of increase of the fly. 

 From Pearse. 



been absolutely proven that if certain species of mosquitoes bite 

 a person having either malaria or yellow fever, the protozoan 

 which causes the disease, is taken up with the blood, develops in 

 the mosquito's body and may be injected with the saliva into the 



