Hello, 
 
I´m sorry I used spanish about swarm traps. It won´t happen again. I 
said that the mexican government used carboard boxes hung on trees, 
they were covered with plastic, like the one used in plastic bags. The 
boxes were about 60X40 cm (Don´t know in inches, about 2x1 ft, maybe a 
little bigger?)with a little hole in one side. They put citral (lemon 
grass is ok) to improve the trap.
 
I observed that swarms like to get into very old hives, better if they 
have a comb inside, and even better if they are a little up the ground, 
but africanized bees aren´t very selective.
 
Tere