Pine barrens, also known as "pine plains", "san plains", "pinelands", "pine bush", and "pitch pine-scrub oak barrens", occur throughout the northeastern U.S. from New Jersey to Maine (see Atlantic coastal pine barrens) as well as the Midwest and Canada. Pine barrens are plant communities that occur on dry, acidic, infertile soils dominated by grasses, forbs, low shrubs, and scattered trees; most extensive barrens occur in large areas of sandy glacial deposits, including outwash plains, lakebeds, and outwash terraces along rivers. The most common trees are the Jack Pine, Red Pine, Pitch Pine, Blackjack Oak, and Scrub Oak; a scattering of larger Oaks is not unusual. The understory is composed of grasses, sedges, and forbs, many of them common in dry prairies. Plants of the heath family, such as blueberries and bearberry, and shrubs such as prairie willow and hazelnut are common. These species have adaptations that permit them to survive or regenerate well after fire. Pine barrens support a number of rare species, including lepidoptera such as the Karner Blue butterfly (Lycaeides melissa samuelis) and the barrens buck moth (Hemileuca maia), and plants such as the Sand-plain Gerardia (Agalinis acuta).