Bed bugs are parasitic insects that feed on blood. Their bites can cause a variety of harmful symptoms. When they bite their hosts, who are usually human, they do so without even being noticed. Most of the time, the host can’t even feel the bite. This is because bed bugs have a unique bodily structure, called proboscises. Proboscises are two tube-like structures used to pierce the skin and inject saliva that has anticoagulant (anesthetic) properties and then drink the blood.