When I entered the woods there, I was at once pursued by a swarm of those wood flies which gyrate around your head and strike your hat like rain-drops. As usual, they kept up with me as I walked, and gyrated about me still, as if I were stationary, advancing at the same time and receiving reinforcements from time to time. Though I switched them smartly for half a mile with some indigo-weed, they did not mind it in the least . . .