240 



INSECTS AND DISEASE 



not less than 1000 named species of mosquitoes, yet 

 probably not more than a half dozen are capable of trans- 

 mitting the malarial disease (Fig. 62). These few species 

 are characterized by spotted wings and by tilting their 



Fig. 62. — A non-malarial mosquito, Theohaldia 

 standing on the wall. (About twice natural size.) 

 Kellogg and Doane, Economic Zoology. 



incidens, male. 



bodies upward at an angle when at rest, while the body 

 in other species is held parallel to the surface on which it 

 rests. If a malarial patient is bitten by a mosquito some 

 parasites are certain to be withdrawn in the process. One 



Fio. f)2A. — A malarial mosquito, Anopheles maculipennis, female, 

 standing on the wall. (Alwut twice natural size.) 

 Kellogg and Doane, Economic Zoology. 



of two things now takes place: If the mosquito is a non- 

 malarial one the parasites are digested along with the 

 blood and their history is closed. If it is a malarial 

 species the parasites in its digestive tract continue their 



