MOSQUITOES AND THEIR EXTERMINATION. 457 



the surface of the water be disturbed at this time, the insect would be 

 upset and drowned. It takes about seven minutes from the time when 

 the skin along the back of the pupa begins to split until the full- 

 grown mosquito comes forth and in a few minutes is ready to fly 

 away. A mosquito never grows any larger after this change. 



The length of time required to pass from the egg to the adult 

 insect varies from ten days to three weeks, according to the tempera- 

 ture. Warm weather hastens their development, while low tempera- 

 ture checks it. The 'wigglers' of some species of mosquitoes live 

 through the coldest weather of our northern winters unharmed, ready, 

 when the first warm days of spring have come, to complete their natural 

 changes. 



Mosquitoes' eggs are so very small that ordinarily they remain 

 unnoticed, but nearly every one who lives in the country is familiar 

 with the little 'wigglers' that are often seen squirming up and down 

 in rain-water barrels. Few people know that these little fellows are 

 connected in any way with mosquitoes, but it is a very easy matter to 

 prove that they are. Let any one who doubts this fact dip up a few in 

 a glass jar or tumbler and place them in the house, where they can be 

 frequently looked at. Seeing is believing; and after a full-grown 

 mosquito has once been seen to come forth from a pupa (which is the 

 last stage of the 'wiggler'), there can not any longer be any question 

 as to what these 'wigglers' really are. 



Most of the mosquitoes that annoy us are bred near by, often, 

 though unknown to us, in our own dooryards. Any water that is 

 accessible to mosquitoes and wdiose surface is undisturbed by winds or 

 rapid currents furnishes a breeding-place for them, and 'wigglers' 

 may often be found in water standing in old tin cans or bottles, in 

 rain-water barrels, in pools in the rocks, in roof or street gutters that 

 are not properly drained, in cesspools or in catch-basins, in fact, in 

 any place that will hold water for a week or two, no matter how small 

 the quantity, even if only a few teaspoonfuls. 



Since we know that without water mosquitoes in their first stages 

 can not exist, it naturally follows that all standing water should be 

 done away with or treated in such a manner that 'wigglers' can noi 

 live in it nor mosquitoes get to it to lay their eggs. To this end all 

 cans, bottles and every discarded utensil that will hold water should 

 be removed. All stagnant pools, where it is possible to do so, should 

 be drained or filled up. Cisterns, rain-water barrels and cesspools 

 should be screened or otherwise covered to prevent the adult insects 

 from having access to them. Where it is not practicable to fill, drain, 

 or screen the places that are suitable for mosquitoes to breed in, the 

 surface of the water may be covered with kerosene oil. This oil, 

 when spread over the water, prevents the 'wigglers' from getting air 



