Like Dusty said on his blog the other day, these guys are incredibly hyperactive and difficult to catch. This one had staked out this twig as his home base (at least for a few minutes) and was using it as his lookout position to guard his little corner of the lake. When any other dragonfly, or mosquito hawk as I grew up calling them, came near, he would dart at them, chase them away, and return to his perch. Since he routinely landed near the same spot, I set up the tripod, focussed on that spot, and waited with the shutter release cable in my hand. He would land and I would trip off several shots. Until that afternoon I really did not know there are so many different kinds of dragonflies, many sizes, and colors, but all the same basic helicopter shape. And all very adept at changing directions abruptly in mid-air.