178 THE HAUNTS OF LIFE 
be able to remain under water for consider- 
able periods, because they have various ways 
of carrying reserves of air, as bubbles en- 
tangled 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 beau- 
tiful 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 per- 
fect 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 larve 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 de- 
veloped from the air-tubes which are present, 
even though the openings to them are closed. 
And many of the larve breathe surface air 
from the first. The gnat larve, which we may 
find in any ditch, have a breathing-tube pro- 
