How Diverse are Cockroaches Globally?
Stephanie L. Richards, PhD, Medical Entomologist
How many species of cockroaches are there?
Cockroaches have been documented as far back as 300 million years ago and have adapted to survive while many other organisms did not. Globally, approximately 4,600 species of cockroaches have been discovered so far and many more remain to be discovered by scientists. In North America, there are approximately 50-70 known cockroach species. Most cockroaches do not come into contact with humans and are forest dwelling creatures.
Less than one percent of all cockroach species are considered pests of humans and some species only occur where human living exist. These pests have likely been distributed throughout the world via human transportation. The distribution of some common cockroach species found in the United States and elsewhere are discussed below.
Where are cockroaches located?
Cockroaches thrive in subtropical and tropical climates throughout the world, but are also abundant in temperate climates. There are also some species of cockroaches that live in the Arctic region.
What are some examples and distribution information of cockroaches that are not considered pests?
The Madagascar hissing cockroach (Gromphadorhina portentosa) is an example of a non-pest species that is not associated with human activity. These organisms live on the forest floor and feed on rotting plant materials, including fruit. This cockroach is primarily found on the island of Madagascar; however, classrooms and individuals often adopt these organisms as pets due to their docile nature. The cockroach gets its name because of the hissing sound it produces in response to danger (to alarm predators), combat with other males, and/or in mating processes.
The giant cave cockroach (Blaberus giganteus) is found in rainforests of Central and South America and is about the size of a human hand. As the common name suggests, this species is found in areas such as caves and other places where there is little light exposure. It feeds on rotting plant materials and other items, such as bat excrement (in caves) and fruit.
The Pennsylvania wood cockroach (Parcoblatta pennsylvanica) is a common species in several areas of North America and the Florida wood cockroach (Eurycotis floridana) is found in the southeastern United States. These species (and other species of wood cockroaches) are not usually found inside homes. They generally live in forested areas and feed on decaying organic material. However, in some cases, these roaches may be inadvertently brought indoors in piles of firewood and they have been known to impact wooden shingles or homes located in heavily wooded areas.
What are some examples and distribution information of common household cockroach pests?
The American cockroach (e.g. Periplaneta americana) originated in the Old World (likely Africa). This species was likely transported to the United States from Africa in the early 1600s. They are scavengers and will feed on anything from decaying organic matter to hair, bread, fruit and book bindings. Some cockroaches have been linked to public health issues such as allergies and food safety. Some species are associated with mechanical transmission of bacteria, such as Salmonella, Staphylococcus aureus, Escherichia coli and Listeria.
Blatella species of cockroaches are largely found in Asia. The German cockroach (Blattella germanica) may be the most widely distributed species and has adapted to a variety of regions since its first discovery in 1797 in Denmark. Some scientists believe this species originated in Africa and made its way to Europe via trade routes, while others think its origins lie in Asia. German cockroaches are found (always associated with humans) as far south as southern South America and they are found on all continents except Antarctica. Some studies (e.g., Vargo et al., 2014, Tang et al. 2016) have characterized the genetic diversity of German cockroaches; however, it has been difficult to determine the origin of many cockroach populations since there are generally continual introductions from different locations. German cockroaches will feed on many foods, including meats, fats and starchy/sugary foods.
Cockroaches have been around for millions of years and will continue to be successful in human and nonhuman-associated environments. For the cockroach species that are considered public health pests, precautions must be taken to help prevent their occurrence and/or minimize abundance in homes, restaurants and other commercial establishments to protect health. Pest management professionals can help by instituting surveillance-based targeted pest control programs based on integrated pest management principles.
Tang Q, Jiang H, Yangsheng Li, Bourguignon T, Evans TA (2016) Population structure of the German cockroach, Blatella germanica, shows two expansions across China. Biological Invasions 18:2391-2402.
Vargo EL, Crissman JR, Booth W, Santangelo RG, Mukha DV, Schal C (2014) Hierarchical genetic analysis of German cockroach (Blattella germanica) populations from within buildings to across continents. PLoS ONE 9: e102321.