1 78 THE HAUNTS OF LIFE 



to remain under water for considerable periods, 

 because they have various ways of carrying 

 reserves of air, as bubbles entangled among 

 the body-hairs, for instance, while others are 

 able to use the oxygen mixed with the 

 water. 



In addition to these, many insects, such 

 as the gnats, may-flies, caddis-flies, and the 

 beautiful big dragon-flies, lay their eggs in the 

 water, and the great changes from egg to larva, 

 from larva to the " resting-stage," which is a 

 preparation for the emergence of the perfect 

 insect, are gone through in the water. Yet 

 this is not a case in which an aquatic race is 

 on the way to terrestrial life ; they are not 

 water-breathers, they are air-breathers, which 

 have adopted the habit of laying their eggs in 

 the water for the greater safety of the young. 

 Many of the larvae have become so well adapted 

 to aquatic life that they are able to breathe 

 dissolved air by gills, but these " tracheal gills," 

 as they are called, are developed from the air- 

 tubes which are present, even though the 

 openings to them are closed. And many of 

 the larvae breathe surface air from the first. 

 The gnat larvae, which we may find in any ditch, 

 have a breathing-tube projecting from the last 



