Are you speaking of the ramp style DE traps (piece of thin wood with DE glued underneath)?? I tried them last year and found them to be somewhat effective. Not 100% but they did a pretty good job over all.
This type of device doesn't actually trap the beetles. When the beetles attempt to hide beneath it their antennae are cut which disorients them. They then either desiccate from the cuts or become easier targets for the bees to force from the hive. Don't expect to see masses of dead beetles (although you may find little bits of them scattered around). Instead, look for a general lessening of their population.
Hope this helps,
"In the first place, we should insist that if the immigrant who comes here in good faith becomes an American and assimilates himself to us, he shall be treated on an exact equality with everyone else, for it is an outrage to discriminate against any such man because of creed, or birthplace, or origin. But this is predicated upon the person's becoming in every facet an American, and nothing but an American...There can be no divided allegiance here. Any man who says he is an American, but something else also, isn't an American at all. We have room for but one flag, the American flag...We have room for but one language here, and that is the English language...And we have room for but one sole loyalty and that is a loyalty to the American people."
Theodore Roosevelt 1907