German cockroach. Coloured scanning electron micrograph (SEM) of the head of a German cockroach (Blattella germanica). These insects have changed little in millions of years, and are considered living fossils. Despite their name, German cockroaches are not native to Germany, but instead originated in warmer areas. They have spread with humans, however, and now live throughout the world. They are unpopular as they feed on human scraps in many areas, and form huge populations. They give an area a foul smell, and carry bacteria and viruses. The German cockroach measures about 13-16mm long.