I recall fishing a private, Central Oregon lake on a cool, sunny Fall day. Suddenly, with nary a cloud in the sky, large rain drops were intermittently splatting upon the lake’s surface….no clouds? drifting rain? wow. No, it was an event I had never witnessed before and was not the least bit ready for: a fall of Water Boatmen returning to the lake to lay eggs. One person on the lake, a big know it all, because he was prepared….had a water boatmen pattern and upon using it he was highly successful. Nothing I had really worked. I picked up one fish on a bead head diving Caddis. I have since then carried several versions of Water boatmen and on the sudden occassions when they start splatting, I am ready. This is akin to carrying Hex, Damsel and Dragon Adults and crawdad patterns. You never know. So, that said, tie up a half dozen simple patterns as you head out to the ponds, lakes, reservoirs, stillwaters this Fall. I read this takes place at ice off in the Spring but I have not witnessed it then.       http://www.onlineflytyer.com/article_waterboatman.asp  

 “The prime time to fish boatman imitations is in the late fall after the first frosts of the season. Capable of flight the mature boatman mate and disperse at this time crashing headlong into lakes all over the south central interior of the province. These cascading boatman give the illusion of rainfall. Upon slamming into the surface the water boatman spins wildly as though knocked senseless by the impact. Breaking through the surface film the boatman scoot down to the bottom depositing their eggs upon weeds and other subsurface debris. At certain times trout become fixated upon the surface-spinning boatman. Traditional boatman patterns cast at these selective fish prove fruitless. Anglers who have buoyant boatman patterns in their fly boxes can reap huge rewards at this time.”  

 
‘Water boatmen are considered a delicacy to people in many parts of Mexico, where they are harvested and eaten in large numbers. They are also used and exported as pet food.’ (little known facts…just as well, I say)
Water Boatmen~FlyUSA
Water Boatmen~FlyUSA