The bridge between Charlestown NH and Springfield VT was closed for about four hours Thursday night due to a heavy infestation of mayflies. Springfield Police say mayflies hatched from the halogen lights along the old toll bridge and the accumulation of the insects made the roadway extremely dangerous. Charlestown NH Police and Fire Department along with Charlestown’s Community Emergency Response Team (CERT) to assisted with traffic. Mayflies also closed the bridge in 2010 for a day. The bridge is conducive to the mayflies since they live more than 99% of their lives as nymphs on the river or lake bottom, before emerging as adults who mate then die within one or two days.