96 
MANUAL OF NATURK STUDY. 
1. Where ground is tilled, these earth-worms 
help to carry water from the surface to the tile ditch, 
and thus help in the drainage. 
2. In time of rain after a long dry spell, they 
help the water to soak into the ground rather than 
have it run off into ditches, and thereby become 
wasted so far as the plants are concerned. 
3. They reclaim waste land by bringing dirt to 
the surface and covering up stony places, etc. 
Henson estimated the amount of dirt brought to 
the surface to be about 36 tons to the acre per year. 
Darwin’s estimate was about half that amount. On 
an average, according to Henson, there are 53767 
worms to the acre, or 36.5 tons. 
The ants, also, do an immense amount of exca¬ 
vating and opening up the soil so as to make it 
more conducive to the health of the plant. Bees 
help in the fertilization of flowers and thus pay 
for all the honey obtained. The same may be said 
of the hornets, yellowjackets, bumble bees, etc. 
The butterfly and moth also aid in this, but their 
larvae are destructive to the life of the plant. But 
then, again, insect-eating birds destroy the larvae 
and thereby repay by way of defence to the plant. 
Birds help in the distribution of plant seed. Ani¬ 
mals of various kinds help in the dissemination of 
seed. How? The excrement of animals and birds 
