I have tried them. My greenhouse is very buttoned up so there isn't easy for them to simply fly away. They unfortunately didn't seem to make a difference. I did notice there was a new generation of the mealybug destroyers appeared some weeks after I thought they all died off, but they didn't put a dent in the mealybug population. I have been fighting mealybugs for years and the most effective control for me has been hort oil. Every winter when my greenhouse is packed full of plants the mealybug population booms, and I try to hose them off as best I can. In spring when I can bring container plants outside I try my best to eradicate every mealybug and apply hort oil all over. No pesticides seem to help, even high doses of imidacloprid.