86 THE ANIMALS AND MAN 



gether to form a narrow, irregular, little raft, slightly concave 

 on the upper surface, and wholly unsinkable. They are 

 to be found on small pools of standing water, or in water- 

 ing-troughs or exposed barrels wherever indeed there is 

 quiet or stagnant water. These egg-masses should be 

 brought into the schoolroom and kept in glass tumblers, 

 with some of the water on which they are found floating 

 (fig. 36). Examine an egg-mass with a hand lens to note 

 the arrangement and appearance of the eggs. How many 

 are there in the mass? 



The eggs should be kept under pretty constant observation 

 for hatching is likely to take place soon after they are brought 

 into the schoolroom. Ordinarily they hatch in from twelve 

 to twenty-four hours after they are laid. They may, of 

 course, hatch at night. But if the hatching occurs during 

 the day it can be easily observed. From which end of the 

 egg does the young mosquito emerge? It may not be easy 

 to find the egg-masses on the pools; in that case the wrigglers 

 or larvae (described in the next paragraph) should be sought 

 for and brought into the schoolroom in tumblers or jars 

 containing water taken from the pool in which they are 

 found. The life-history can be studied from this point on. 

 The tumblers must not be kept in places too cool or dark, 

 or the young mosquitoes will develop abnormally slowly. 



The "wrigglers" or larvae.- -The newly hatched mosquito 

 bears no resemblance to the familiar winged fly which we 

 call by that name. In this first stage of its life, or second 

 stage, if we call the egg stage the first, it is familiarly known 

 as a "wriggler," but is called larva by naturalists. The 

 active young stage of any insect which differs markedly 

 from the fully developed or mature one is called the larval 

 stage. 



The larvae swim actively about. By what means do they 

 swim? If they cease swimming do they sink deeper in the 

 water or rise to the surface ? Is the body of the larva denser 



