There are over 2500 different species of mosquitoes throughout the world (Gilles and Warrell, 1993), most of which do not affect the well-being of humans, apart perhaps from causing nuisance. Some, however, are capable of transmitting diseases afflicting animals, for example, equine encephalitis or dog heartworm. Other species transmit diseases that cause illness in humans, the most important of which are malaria, filarial diseases, and arboviruses such as dengue, encephalitis, and yellow fever.