428 



MOSQUITOES 



oesophagus, in addition to a large stomach (Fig. 189). Connected 

 with the proboscis is a pair of salivary glands consisting of three 

 lobes each. One of these lobes in each gland differs from the 

 others and instead of secreting ordinary saliva is thought to secrete 

 the poisonous substance which prevents coagulation of blood and 

 produces the inflammation and pain attendant upon a mosquito 



FIG. 192. Larva and adult of Corethra, a member of the Culicidse which is not 

 a bloodsucker, but is often mistaken for a mosquito. The larvae prey on mosquito 

 larvae and other aquatic organisms. Note anterior and posterior "floats" in the 

 larva, and mosquito-like appearance of adult, except for lack of proboscis. (Larva 

 after Howard, Dyar-and Knab; adult after Smith.) 



bite. Schaudinn, however, has adduced some experimental evi- 

 dence that it is the contents of food reservoirs which cause the 

 inflammation. It is in the salivary glands that the malaria para- 

 sites, and probably the parasites of dengue and yellow fever also, 

 collect, and whence they are poured with the secretions of the 

 glands into the wounds. 



Life History. Mosquitoes, like other Diptera, pass through 

 a complete metamorphosis in the course of their life history, i.e.) 

 they undergo a transformation from larval to adult stages during 

 a period of rest. In a general way the life histories of all mos- 

 quitoes are much alike, but in details there is much variation 



