Cysteodemus wislizeni, commonly known as the mesquite girdler, is a species of beetle belonging to the family Cerambycidae. It is found in the southwestern United States and northern Mexico. This insect is known for its distinctive behavior of girdling mesquite trees by chewing through the bark, causing the branches to die and fall off. The larvae of Cysteodemus wislizeni develop within the girdled branches, feeding on the wood.