It looks like something out of a horror movie, but this scene was very, very real.
Police were called to a bridge in Sabula, Iowa, after a pair of motorcyclists came off their bikes after skidding on mayflies.
Teena Franzen was enjoying a ride along with her son in his police car when she recorded the nightmarish incident on Saturday night, reports whdh.com.
The footage was uploaded to YouTube, along with the caption: "Sabula Iowa Police department was called to assist a motorist on the Sabula Savanna bridge.
"When the officer arrived he realised what had happened. Millions of shad-flies had hatched and made the bridge like ice. There were literally inches of the bugs on the ground."
Speaking to wqad.com, Teena said: "I've lived in Sabula since '75, I've never seen that many before, ever."
Officer Stephen Thayer, of Sabula Police Department, said the flies were "piled knee high": "Biggest thing I noticed was after cars were stopped and sitting for so long while we're trying to get cars moving again is they were probably piled knee high in front of their headlights from just sitting there."
Mayflies, or shadflies, are aquatic insects, which are part of an ancient group of insects termed the Palaeoptera, also containing the dragonflies and damselflies.
Over 3,000 species of mayfly are known worldwide, grouped into over 400 genera in 42 families.
Mayflies are relatively primitive insects and exhibit a number of ancestral traits that were probably present in the first flying insects, such as long tails and wings that do not fold flat over the abdomen. They are aquatic insects whose immature stages (called "nymphs") live in fresh water, where their presence indicates a clean, unpolluted environment.
Mayflies "hatch" (emerge as adults) in spring, not necessarily in May, in enormous numbers, as seen here. Some hatches even attract tourists. But we're pretty sure we'd run a mile if we saw this...
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