How does a deer mouse make a thimble? Which bird is a backyard acrobat? What makes a firefly glow? Worms and squirrels, deer and little brown bats: Creatures in every part of your backyard, from under the ground to up in the trees, come to life in Backyard Wilderness.   Whether your backyard is 50 acres in the country or 500 square feet in the city, it is a wilderness for you to explore. You may have seen birds and butterflies, squirrels and spiders, but there is probably a whole lot more going on that you have never seen or thought about!   In this book you will learn about a variety of creatures that may live in your backyard wilderness. Many of the kinds of animals we show here--from mammals to insects--occur throughout much of North America. If a certain species does not live in your area, a similar one probably does. For example, if an eastern cottontail doesn't live where you do, perhaps a desert cottontail does instead. Be creative as you seek the creatures around you.