Phthirus is a genus of lice that infests the pubic area of humans. It is often referred to as the pubic louse, but there are other synonyms for this pesky parasite. Some common synonyms for phthirus include crabs, pubic crab lice, and Pthirus pubis. These lice are smaller in size than head lice, and their claws are adapted for gripping the coarser hair found in the pubic region. Phthirus infestations can result in intense itching, especially at night, and can lead to skin irritation and infection if left untreated. It is important to identify and treat phthirus infestations promptly to prevent further spread and complications.