MOSQUITOES 57 



food, seek a convenient pool of water on which to deposit 

 their eggs. 



Eggs. The eggs of Culex pipiens are laid on the sur- 

 face of the water in more or less boat-shaped masses, 

 (Fig. 21). Each mass contains from 75 to 200 eggs, con- 

 sequently they vary much in size. They measure from 

 ^ to ^ of an inch in length and 

 are plainly visible to the eye. 

 The eggs stand on end in 

 regular rows with the larger 

 ends down. When first laid 

 the masses appear yellowish 

 white, but a little later they FlG- 21 

 become dark brown in color 

 and appear as small masses of soot floating on the water. 

 Very often where there are many egg masses on the water, 

 several of them will run together by capillary action and 

 form a raft of eggs on the surface. We have seen as 

 many as a dozen of these egg masses clinging to each other. 



Each individual egg is long and cylindrical, larger at the 

 lower end, and tapering to the upper end. As seen from 

 the side, it resembles the blade of a knife (Fig. 20, d). 

 These eggs float on the surface of the water from 

 twenty-four hours to several days, depending upon the 

 temperature, and then hatch. 



Larva. When the egg hatches, there issues from the 

 lower end a larva, or "wriggler." Every one that has 

 looked into rain-barrels that have stood for some time 

 during hot weather has surely seen "wrigglers." These 

 are the product of mosquito eggs. The larva of Culex 

 pipiens rests for the greater part of the time with the tip 

 of the abdomen at the surface of the water, and the head 



