Roughly 100 invertebrate animal species are protected under the Massachusetts Endangered Species Act, or MESA. These include moths, butterflies, dragonflies, damselflies, mussels, and crustaceans, among others. These species are all rare, and most of them need a very specific habitat to live in. For example, many listed moths and butterflies live in pitch pine-scrub oak barrens that are very open due to past fires or other disturbances. Additionally, listed aquatic species live in clean, unpolluted waters. Invertebrate conservation is achieved by protecting the habitats in which these species live. These habitats face a variety of threats, including outright destruction, exclusion of natural disturbance, invasive exotic plants, and introduced exotic parasitoids (like wasps and flies).