88 



Insects and Disease 



convenience, indeed may pass wholly unnoticed, 

 to others a single bite may mean much annoyance, 

 and several bites may cause much suffering. 



After an hour or so the itching usually ceases, 

 but in some cases it continues longer. In some in- 

 stances little or no irritation is felt until some hours, 

 sometimes as much as a day, after the bite. In 

 such cases the effect of the bite is apt to be severe 

 and to last for several days. Sometimes a more or 

 less serious sore will follow a bite, probably due to 

 infection of the wound by scratching. It is doubt- 

 less the saliva that is poured into the wound that 

 causes the irritation. It is frequently asserted that 

 if the mosquito is allowed to drink its fill and with- 

 draw its beak without being disturbed no evil 

 results will follow. Those who hold this theory 

 say that the saliva that is poured into the wound is 

 all withdrawn again with the blood if the mosquito 

 is allowed to feed long enough. There may be 

 some truth in this, but for most of us a bite means 

 a hurt anyway and few will be content to sit per- 

 fectly still and watch the little pest gradually fill 

 up on blood. 



It is not known just what the action of the saliva 

 is, its composition or reaction on the tissues. It is 

 generally supposed to prevent coagulation of the 

 blood that is to be drawn through the narrow tube 



