INSECTS IN RELATION TO DISEASE 329 



3. Insects as intermediate hosts (mosquito) 

 Life histoty and habits of mosquito 

 • Egg; larva; pupa 

 In still water 

 Adult 



Flies about freely 

 Male does not take food 



Female sucks juices from bodies of plants and animals 

 Life history of malarial parasite 



Plasmodium, sporulation : in red corpuscles of warm-blooded 



host 

 Male and female cells : in capillaries near surface of host 

 Conjugation : in stomach of mosquito 

 Fertilized egg : in wall of mosquito stomach 

 (Biastomeres : from swellings on stomach wall to saliv^ary 

 glands ; in red corpuscles change to Plasmodia) 

 Yellow fever as insect-borne disease 



No yellow fever among persons shielded from mosquito 

 (Aedes) even when exposed to contact with clothes, bed- 

 ding, discharges, etc. of yellow-fever patients 

 Yellow fever among persons stung by mosquitoes that had 

 previously stung yellow-fever patient, even when protected 

 from all contact with patients and their clothes, dis- 

 charges, etc. 

 No yellow fever among persons stung by mosquitoes other 



than Aedes 

 No yellow fever among persons stung by Aedes mosquitoes 



that had not previously stung patient 

 Yellow-fever parasite (Leptospira icteroides) recently dis- 

 covered by Noguchi 

 Means of combating mosquito and protecting health 

 Kill individual adults 

 Prevent breeding 

 Drain swampy areas 

 Fill in 



Oil waters that cannot be cleared away or drained 

 Clean up rubbish etc., in which water pools can form 

 Cover water barrels, fire pails, cisterns, etc. (screen) 

 Stock ponds etc. with fish 

 Keep edges of ponds and brooks clear of brush 

 Screen houses 



