Y. Higa may occur. It is necessary to monitor the distribution of Ae. aegypti and Ae. albopictus, as well as climate parameters over the long term. Transportation and trade The flight range of Ae. aegypti and Ae. albopictus is relatively small, approximately 50–500 m [3, 10, 15]. In spite of small active movements, both species have spread across continents from their origins. This is associated with resistance of eggs to desiccation. Even when the water in a container dries up, eggs laid on the container wall can survive for several months. When containers with eggs are carried to a new place and rain falls, the eggs hatch. If there are host animals and climate is suitable, a population will be established there. Water-holding containers with larvae have also contributed to the movement of mosquitoes. From the 17 to 19th centuries, Ae. aegypti hidden in vessels on boats traveled from Africa to other continents [1, 2], while Ae. albopictus started to spread to the Pacific islands in the early 20th century. However, it was not until the 1970’s that the geographic distribution dramatically changed. Ae. albopictus larvae were found in Albania in 1979 and then in the U.S. in the 1980’s [71, 72]. The establishment of Ae. albopictus was first confirmed in Texas in 1986 [76]. Although there are some records of Ae. albopictus in the U.S., the species was not established in other states before 1986 [77, 78]. After that, however, Ae. albopictus expanded quickly over the country and has been recorded from 26 states at present [79]. All of the Ae. albopictus in the U.S. were collected from water-holding used tires. Therefore, it was speculated that Ae. albopictus eggs laid on the inside wall of used tires were carried and a population established [80]. In order to determine the origin of the Ae. albopictus population in the U.S., Hawley et al. (1987) examined the presence of egg diapause and found that North American strains of Ae. albopictus exhibit characteristics of photo- periodic sensitivity and cold-hardiness similar to strains originating from temperate zone Asia [19]. A careful inves- tigation of Ae. albopictus-infested tire-exporting countries and the tire imports of newly infested countries revealed that more than 90% of used tires imported to the U.S. were from Japan [81]. Similarly, Ae. albopictus was recorded from Brazil and the Dominican Republic where 81.5% and 97.4% of tires, respectively, were from Japan. Reiter (1998) concluded that infestations of Ae. albopictus in the U.S., Brazil and the Dominican Republic were probably primary infestations derived directly from Japan [81]. The large size of the Ae. albopictus population carried to the U.S. facili- tated the further spread of the species to other countries. Ae. albopictus was collected from tire piles in Italy in 1990 and the population was established by the following year [82, 23 83]. After 1990, Mexico, Guatemala and Nigeria were also found to be infested. These infestations were probably secondary, derived from the U. S. which exports 55.4–99.4% of the used tires to the above countries. The same was probably true for Italy. The Cuban infestation may have been derived from Mexico, from which 90.8% of used tires were imported [81]. Due to the global trade in tires, Ae. albopictus was introduced through many countries and continued to be recorded from parts of Europe and Africa after 2000 [84–87]. Since most of the current records are from human dwellings, therefore Ae. albopictus was probably introduced earlier without being noticed, and some authors considered the species to have been carried by used tires. Unfortunately, Ae. albopictus has become a vector of infectious diseases in the places it has newly invaded. In the U.S., West Nile virus was isolated from field-collected Ae. albopictus [88]. In the 2007 outbreak of chikungunya fever in Italy, Ae. albopictus was incriminated as the principal vector [27]. Chikungunya virus was also isolated from adult Ae. albopictus derived from larvae collected during a chikungunya outbreak in Kerala, south India in 2009 [26]. CONCULUSION The differing in spatical distribution of Ae. aegypti and Ae. albopictus reflects the difference in the niches of the two species in an environment. However, the spatial distri- bution of Ae. aegypti and Ae. albopictus sometimes does not conform to preconceptions as high abundance of Ae. aegypti in urban areas and Ae. albopictus in rural areas. This is attributable to the dependence of the vector mosquitoes on environments created by humans. Since the lifestyle and customs of people vary among countries and regions, the environments for Ae. aegypti and Ae. albopictus, such as larval breeding sites which are usually artificial containers, housing structures, gardens etc., also vary. As suggested by studies predicting changes in the distribution of dengue vectors, global warming and other aspects of climate change caused by the consumption of fossil fuels will undoubtedly have a great impact on spatial distribution of the vectors. The expansion of Ae. albopictus northward due to the influence of global warming on vector distribution provides actual evidence. In conclusion, however, environ- mental changes caused by human activities and human behavioral changes caused by climate change exert a greater impact on spatial distribution of Ae. aegypti and Ae. albopictus than direct climate changes. Uncontrolled urbanization and the construction of buildings without proper environmental management may create slums favor- able to Ae. aegypti. In slums, houses are built close to each