Phthiraptera is an order of insects commonly known as lice. These small, wingless parasites are primarily found on mammals and birds, feeding on their blood or skin. There are two main suborders: Anoplura, which includes sucking lice, and Mallophaga, which consists of chewing lice. Lice have a flattened body and specialized claws that help them cling to their hosts. They reproduce quickly, laying eggs called nits that attach to hair or feathers. Infestations can lead to discomfort and irritation for the host, making lice control important in both human and veterinary health.