Why are egg-laying female mayflies vulnerable to fish?

Egg-laying female mayflies are vulnerable to fish because of their specific methods of oviposition (egg deposition), which require them to interact directly with the water's surface.1

While some species drop their eggs from a height, many others must fly low over the water, striking the surface repeatedly with the tip of their abdomen to wash off eggs, or they land on the water's surface to release their eggs as they die. Because these behaviors involve close, repeated contact with the water, the females become easy targets for feeding fish. Consequently, these insects are highly susceptible to predation by fish during the egg-laying process, a vulnerability so well-known that human fishers often pattern their artificial lures after them.1