Big ants and little ants

I have seen this scene many times here.  Ants are a real nuisance.  There are so many kinds also.  Some are really small but the smallest ones have the most fierce bite.  I have seen people swell up and have to go to the hospital from them.  There are also very fast ants (see the "many kinds" link for Psycho ants).  They move like a sped up movie!  But these in the picture are very curious.  There are big ants and little ones working together.  They travel the same path always.  Can you see the small ones carrying what looks like bits of rice?  I have seen these little ones get together and carry something the size of a nickel.  There could be as many as 50 tugging generally in the same direction.  The really big ants appear to be doing nothing at all.  But they are always there moving along with the little carriers.