THREE OLD RIDDLES

1)
The caller all rejoice to see,
Desired above his betters;
The reigning favorite is he
Among all men of letters.

2)
My whole a thing
With a terrible sting;
But cut off my head,
And still more you'll me dread.

3)
Two splendid horses
In a never-ending race;
Each runs ahead of the other,
But never changes place.

Answers:

1. POSTMAN 
2. WASP / ASP 
3. DAY AND NIGHT