The city's roach population was inadvertently introduced by trade. Such species as the American, Oriental, Australian, German, and brown-banded are all found in the city.
Roaches are also variable with respect to food preference.
Many are scavengers that feed on garbage, dead insects, and human food, and some species invade human habitats. Cockroaches are especially visible in poorly maintained buildings, because wall voids and accumulations of debris provide good shelter. Cracks around windows, doorways, and plumbing provide easy access to sources of food, but the insects easily enter new apartments as well, often by riding in on the clothing or shopping bags of residents, or by flying and crawling in from other buildings. They often seek the water around pipes and sinks and are known to be attracted to toothpaste. Although extermination by chemical control has sometimes proven effective, often it merely forces roaches into a neighboring apartment or building, and in some places roaches have become resistant to the most widely used substances.