Why do they need so much food?

I am following precautions regarding allowing them to get loose since
I don't want to disrupt the local ecosystem. I am curious, are Harvester Ants
  native to Saudi Arabia?
Apparently they do well in arid regions, and there
is plenty of that here

What
dose a ant do?
 Ant’s live in ground. They only make there homes in soft ground. 
Ant’s lay eggs every day when ant’s are hached they eat  there egg shele. Colonies are home to three  different kinds of
ant family members. Each colony has a queen. A queen is a  large female ant who
spends her life laying eggs. There also are a few males  with wings called
drones. There are thousands of workers, all of whom are  female. Workers are
very busy and active. Usually, worker ants are the only  kind of ant you’ll see
outside the colony