Acari is a term used to describe the arthropod pests that belong to the subclass Acarina. These pests include ticks, mites, and other related species that can cause severe health problems in both humans and animals. Some of the synonyms for the term Acari include arachnids, spider-like creatures, and red bugs. They are considered parasitic organisms that feed on the blood and bodily fluids of their hosts, making them highly dangerous pests to have around. It is essential to take preventative measures to avoid contact with Acari, as they can cause diseases such as Lyme disease, Rocky Mountain spotted fever, and other severe health issues.