Phthiraptera
Phthiraptera, also known as lice, are small, wingless insects that live exclusively as parasites on warm-blooded animals, including birds and mammals such as humans. They have specialized mouthparts adapted for piercing and sucking, and their bodies are highly flattened to facilitate movement within the feathers or fur of their hosts. Phthiraptera species can be divided into two main groups: chewing lice (Mallophaga) and sucking lice (Anoplura). Chewing lice feed on skin debris and feather barbs, while sucking lice consume blood. Lice are typically host-specific and spend their entire life cycle on their hosts, with adults laying eggs (nits) that hatch into nymphs which then molt several times before reaching adulthood. Infestations of lice can cause itching, skin irritation, and hair loss in both animals and humans, and some species are capable of transmitting diseases such as typhus and trench fever.