An order included in the Dictyoptera, and comprising 3500–4000 insect species, commonly known as roaches. The fossil record extends back some 400 million years, and roaches were found in abundance in the Carboniferous age. Blattaria are grouped with orders Isoptera (termites) and Mantodea (mantids) within the Dictyoptera. In fact, recent studies support the notion that termites are social roaches; Isoptera appear to be a sister group of roach species in the genus Cryptocercus that, like termites, digest wood with the aid of symbiotic intestinal protozoans.