The biotic regions used by BDWD follow from the traditional division of the world by zoologists into six regions (Slater, Wallace et alia) and our definition of those regions conforms to the ones used by the various Diptera catalogs. The boundaries of these have been slightly modified to more closely conform to political boundaries and are here illustrated (map 1, maps 2-5). Most countries fall entirely within one biotic region. Some countries, like France and the United States of America with their widespread possessions, have components in many biotic regions, but their political subordinate units fall entirely in one biotic region or another.

Only three countries, China, Indonesia and Mexico, extend across biotic regional boundaries. For these countries, the boundaries are drawn between political subunits, such as islands following Weber’s line (Indonesia), provinces (China, with the Oriental ones being Yunnan, Guangxi, Guangdong, Fujian & Zhejiang) or states (Mexico, with the Neotropical ones being Nayarit, Jalisco, Colima, Michoacan, Guerrero, Oaxaca, Veracruz, Tabasco, Chiapas, Campeche, Yucatan & Quintana Roo). While this separation of China and Mexico into their respective component regions is not the most accurate, it is the best approximation that conforms to International Data Standards, such as those of the Taxonomic Database Working Group.

For statistics on single biogeographic regions click on the following links:
All Biotic Region
Afrotropical Region
Australasian/Oceanian Region
Nearctic Region
Neotropical Region
Oriental Region
Palaearctic Region