44 3I0SQUIT0ES 



to count the larva? in an ordinary rain-water barrel. On 

 July 6tli, the water in one barrel was filtered and was 

 found to contain 17,251) eggs, larva? and pup?e. On July 

 22d, 19,110 additional ones were counted. If anyone is 

 mathematically inclined, let him assume that half of these 

 developed into female mosquitoes, each one of Avhich laid 

 400 eggs, and that twelve generations breed in a summer 

 in the northern United States. It will then be perfectly 

 obvious tliat a large neighborhood may be well supplied 

 with mosquitoes from a single neglected rain-water barrel. 



The Poison of Mosquito Bites. 



That fine old observer, Reaumur, rather thought that a 

 poisonous fluid was secreted by the mosquito and that 

 its x)uiTOse was to cause the blood to flow more readily 

 when it bites. Later observers have accepted this state- 

 ment, or have denied the existence of such fluid, stating 

 that the swelling following the bite was caused by the 

 irritation of the puncture, without the aid of poison. 

 Dimmock (1881) convinced himself that a poisonous saliva 

 was introduced. He noticed that if the mosquito punc- 

 tures the skin without entering a blood-vessel, although 

 it may insert its x3roboscis for nearl}^ its full length, no 

 poisonous effect is produced upon the skin ; but when the 

 proboscis strikes blood and the insect draws its fill, the 

 subsequent swelling and iwisonous effect are obvious. 

 He argued that these eff'ects indicate a constant outpour- 

 ing of some sort of i^oisonous fluid during the blood- 

 sucking process. 



