In the Ope River in the town of Moroyama, white wagtails and Japanese wagtails were preying on mayflies that had eclosed on the surface of the water. Mayflies are preyed upon immediately after they eclose on the surface. Some mayflies escape into the forest without being preyed upon. Some of the mayflies do not eclose properly and are unable to fly. I observed them from April 15 to around April 25.
Category: mayfly
Eclosion of mayfly on the surface of water.
I noticed the eclosing of the mayflies because of the constant fling of the wagtails. However, it was difficult to see them eclosing. Even when they do eclose, most of them are soon preyed by the wagtails.
A mayfly was attacked by a water slider.
Before sunset, the mayflies were eclosing on the surface of the water. Even after they eclosed and flew away, most of them were preyed upon by water sliders. Although rare, I saw two cases of mayflies attacked by water striders in five days. The mayfly that was attacked could not fly. The water sliders are sucking the mayfly’s bodily fluids.