Among the most well-known species are the American cockroach, Periplaneta americana, which is about 3 cm long, and the German cockroach, Blattella germanica, about one-and-a-half cm long, and the Asian cockroach, Blattella asahinai, also about one-and-a-half cm in length. Tropical cockroaches are often much bigger, and extinct cockroach relatives such as the Carboniferous Archimylacris and the Permian Apthoroblattina were several times as large as these. When infesting buildings, cockroaches are considered pests; out of the thousands of species, however, only a handful fall into this designation.