Over the ten last years, beekeepers have observed that they had to face more and more queen failures. Low quality semen of the drones (males) can be an explanation. The following article indicates that neonicotinoids have been demonstrated to induce such a reduction in sperm quality at field-realistic levels.

https://www.theguardian.com/environment/2016/jul/27/leading-insecticide-cuts-bee-sperm-by-almost-40-per-cent-study-shows