Confused mayflies wreak havoc on a Pennsylvania bridge
The primitive aquatic insects think the illuminated road is the river
![mayfly swarm](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2018/09/091218_CP_mayfly_feat.jpg?fit=860%2C460&ssl=1)
SWARM STORM Mayflies have been swarming a high-traffic bridge in central Pennsylvania, causing blizzard-like conditions for commuters.
Marisa Macchia