Watch it. Either the bugs don't go in at all: you need better bait. Or there's a gap where they are getting back out: tape the gap. Or they are too clever, a

Watch it. Either the bugs don't go in at all: you need better bait. Or there's a gap where they are getting back out: tape the gap. Or they are too clever, and find the hole in the tip of the cone. I've never seen that, but you could try making the cone deeper?