I believe the primary source was discussed last week. (Discussion is still open but ain't nobody got time for that once it's off the front page!) 75% decline over 27 years in total flying insect biomass in protected areas | https://news.ycombinator.com/item?id=15502074 (Oct 2017, 428 comments)
Last week's article motivated me to plant Milkweed ( Asclepias tuberosa and Asclepias incarnata ) in my garden next year, to help with the population of Monarch butterflies and bees. On the other hand, I'll still be deploying my organic mosquito control based on plant oils injected into a mister system. I really don't think mosquitoes fulfill any role in the ecosystem that can't be filled in by other species; but the…
It's interesting how matter of factly you spread such a casual opinion about what our ecosystem does and doesn't need.