Dengue mosquito research. Larvae of Aedes aegypti mosquitoes (lower left) being analysed for their DNA (deoxyribonucleic acid). The DNA analysis may explain how resistance to pesticides develops, and this may result in methods to counteract any such resistance. Mosquitoes are a vector (transmitting agent) for many diseases. These ones are the main vector for the viruses that cause dengue fever. Pesticides are used to control mosquitoes in an effort to reduce the transmission of the dengue viruses to humans. Photographed in Cuba in 2002.