24 STUDIES IN INSECT LIFE, ETC. 



of course, no food, but it grows gradually darker, 

 and after undergoing a tremendous internal 

 change, breaking down its old tissues and 

 building up new ones, the chrysalis-case cracks 

 and the adult flea jumps out into the world. 



Perhaps the most important of biting insects 

 is the mosquito, certain species of which carry 

 the microscopic organism which causes malaria 

 a disease which has probably played a greater 

 part in the history of the world than that 

 conveyed by any other insect. As in most other 

 biting insects, the piercing organ consists of two 

 tubes, or gutters, in the hollow of which lie certain 

 chitinous rods, with saw-like edges. The outer 

 gutter encloses an inner gutter facing the other way, 

 between these two tubes the blood the mosquito 

 sucks will ultimately flow. In the mosquito 

 there is also a median structure, like a double- 

 edged sword, the prolongation of the lower lip. 

 This is traversed by the duct through which flows 

 the so-called saliva of the insect. This saliva 

 carries with it the microscopic, unicellular 

 animals which cause malaria, and down this 

 minute, microscopic duct has flowed the fluid 

 which has altered the fate of continents and 



