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Why can mayfly swarms make roads slippery?
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mayfly
An adult mayfly (Ephemera vulgata) in Europe.
Mayfly swarms can make roads slippery because the insects sometimes mistake blacktopped roads for streams. When this occurs, they form swarms over the pavement and deposit their eggs on the road surface. The resulting accumulation of insects and their eggs can create hazardous, slick conditions for vehicles.1