NY state has a long running study where on July 15th every year they would put up a super bright lighthouse bulb in the middle of the woods and put it over a tarp. After they night they'd weigh the physical mass of insect life that had come to the light, and died, overnight.

I forget the exact %, but they'd seen a 50 or 60 percent reduction in mass since the 70's, some depressingly high number.