Friday, June 3, 2011

Dun turned into spinner

Mayflies keep hatching on the river these days.  I often see the duns float past, and I enjoy watching them lift off the water's surface and fly for the trees. I posted about the mayflies hatching in my post titled, Fascinating Flotsam.  But there is more to the story as the duns aren't done transforming yet. When the mayflies' aquatic nymphs hatch, and the winged adult stage first emerges on the waters surface, they have one more molt to go to be fully mature.
  The mayfly there on the surface of the water is called a dun or a subimago.  This first winged stage has a layer of microscopic hairs to give it some extra buoyancy and waterproofing as it emerges from its former aquatic habitat.
  The duns fly from the water's surface to the trees or some other object like our riverside porch screen.  There they soon molt, leaving their exoskeletons behind.
  The mayflies are now fully mature and in this second winged stage they are called spinners or imagos.  Pictured below is a spinner that just molted and is about ready to leave its exoskeleton hanging on the underside of a leaf as it heads out into the wide world.
 This world above the waters surface is full of dangers though.  There might not be hungry fish, but there are plenty of spider webs...
 ... and even spiders without webs
 There are also birds, moving vehicles, and even bug lights to add to the danger.
But judging by the fluttering over the river, there are plenty of mayflies to go around.

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