Cyberlocc has hit the nail on the head, "plenty of space for babies" If you have 1 chameleon, and go through 30 or so a week, a 20 quart might work if you bring in only 100-200 at a time. On the other hand, if you want to bring in 500-1,000 because you are feeding off 100 per week, get the 40 or 56 quart containers.
If you do roaches or crickets with the purpose of breeding, you will need the room for the young ones. Roaches seem to like to huddle together in tight spaces, so my roach colonies that are smaller in number all cluster and only use a few of the 10 egg ceases I have in my large containers.
The best container to ensure that bugs don't escape is shown in a thread I did on the Chameleon Forum and the Allpetroach forum. The title is: "My favorite Roach (and other feeders container)." Use the Search Feature to find it.
Bigger is better....
CHEERS!
Nick