We spent the evening watching the sun go down behind the high rocks on the far side of the lake. As dusk sank in around us swarms of bugs appeared above the water, and then, bats. Bats are a threshold animal, somewhere between something harmless like a chipmunk or a bird, but just creepy enough and with enough pop-culture stigma to make us skittish. Bats are mammals; like us, they are warm blooded and have hair, but they also have featherless, skin-covered wings and are mostly blind, instead using echo-location to navigate and hunt. There are thousands of species of bats, and it is estimated that bats make up one-quarter of all mammal species in the world. In the evening, if you see something flying, especially if it seems extra maneuverable or is near open water or a field, it is usually a bat. Bats love insects, and they are a social animal, often living in giant colonies that go out to hunt together in the evenings. On this evening, is seemed we were being visited by a large colony. Far from being scary or gross, these bats were magnificent. They were about the size of a swallow, fast, and fearless. They zipped past our heads diving low to skim across the surface of the water. They twisted and cavorted midair to snatch up dinner and avoid running into one another at the same time. They were acrobatic and mesmerizing and they entirely released me from my worry over sleeping out.