color of mayfly

i know in some river a mayfly will be one color of the net but are they the some color year after year

ill take a wild guess,other then variations between male or female they should be constant

Male & Female March Brown: http://zebu.uoregon.edu/~dmason/Mckenzie/bugs/rithrogena.html
Mayflies: http://en.wikipedia.org/wiki/Mayfly
Doug

i used a white here size 18-22

Where I live we have a river that produces two distinct coloration’s of the same species of may fly.

The river runs through a red sandstone canyon. There are sections where the river bottom is made up of deep red and pink gravels. A PMD variant has developed with a distinct pink colored body. The river also has PMD’s with the usual olive color.

Perhaps the color of a may fly is dependant on natural selection, I could see how a pink colored nymph could hide well in the red gravel sections of the stream, where an olive one would stick out.