INSECTS 



that it is one of the minute, non-filterable organisms 

 called spirochetes. The virus will not develop in the 

 mosquitoes at a temperature below 68° F., and A'edes 



aegvpti will not breed 

 y in latitudes much be- 



/ yond the possible 



range of yellow fever. 

 Yellow fever, there- 

 fore, is a disease ordi- 

 narily confined to the 

 tropics and warmer 

 parts of the temper- 

 ate zones. Season- 

 al outbreaks of it 

 that have occurred in 

 northern cities have 

 been caused probably 

 by local infestations 

 of infected mosqui- 

 toes brought in on 

 ships from some 

 southern port. 



The malaria mos- 

 quitoes belong to the genus Anopheles, a genus repre- 

 sented by species in most temperate and tropical regions 

 of the world, which are prevalent wherever malaria oc- 

 curs. Our most common malaria species is Anopheles 

 punctipennis (Fig. 180), characterized by a pair of dull 

 white spots on the edges of the wings. The Anopheles 

 females lay their eggs singly on the surface of the water, 

 where they float, each buoyed up by an air jacket about 

 its middle. 



The larvae of Anopheles (Fig. 178 B) differ conspicu- 

 ously from those of Culex and Aedes both in structure and 

 habits. Instead of a respiratory tube projecting from near 

 the end of the body, as in Culex (Figs. 174 E, 17O) there 

 is a concave disc (Fig. 178 B,/) on the back of the next to 



[34o] 



Fig. 



180. The female malaria mosquito, 

 Anopheles punctipennis 



