The United States of America covers a very large land area, and covers a wide variety of ecosystems, from Arctic in Alaska to near-tropical in the Southern States and tropical in Hawaii. Because there are so many different environments, it's no surprise that there is an equally large variety of insects and spiders. Some of them, like the black widow spider, are famous around the world, but the great majority are unfamiliar even to local residents.
Some butterfly species are found throughout the USA, but others are found only in the warmer southern states, or the deserts of the south-west or the forests of the north, so I'm going to create several pages to cover the different regions. At the moment you'll have to make do with one page, which describes the butterflies of northern Illinois.
Butterflies and some moths are very obviously attractive, but most people don't give much thought at all to the caterpillars which preceded them. In fact, some of the caterpillars are more brightly colored and beautifully patterned than their equivalent adult stage, as you'll see on my page of caterpillars of northern Illinois.