430 



GENERAL SCIENCE 



eggs in little groups on the surface of stagnant water. 

 When the eggs hatch, the larvae (larva) come forth, little 

 squirming insects commonly known as wrigglers. The 

 larvae, or wrigglers, after about seven days, change into 

 another form called pupae (pupa). The pupa lives in 

 the water three days or longer and changes into the adult 



mosquito, which in 

 turn lays eggs and 

 begins a new cycle 

 of life (Figure 377). 

 When kerosene or 

 crude oil is poured 

 on the water, it 

 spreads over the 

 surface, forming a 

 film which pre- 

 vents the larvae and 

 pupae from getting 

 air from the surface 

 water and thus 

 kills them. The 

 adult mosquitoes 

 also cannot lay 

 their eggs on the 

 surface of the 

 water because they 

 become entangled 

 by the film of oil. 

 The above precautions and the careful screening of houses 

 will reduce malaria to a minimum. 



Yellow Fever. This disease is spread in the same 

 manner as malaria with one marked difference ; namely, 

 that while malaria is carried by one variety of mosquito 



FIG. 377. Life History of the Mosquito. 



The common mosquito (Culex). A, egg raft; 

 B, eggs ; C, young " wrigglers " or larvae ; D and E, 

 vi3ws of larvae ; F, pupa ; G, male ; H and /, fe- 

 males. A, B, C, G, H, and /, somewhat enlarged. 

 D, E, and F, very much enlarged. (After Howard.) 



