Bug zappers were invented for one purpose: to kill mosquitoes, the bane of many summer evenings, camping trips, and exotic vacations. These blood-sucking insects do more than leave us with itchy bites, though. The diseases they carry and inject, such as yellow fever, dengue fever, and the West Nile virus, make them responsible for more human deaths than any other animal. The most deadly of these, malaria, has been mostly eradicated from the northern hemisphere, but it continues to pose a mortal threat in developing countries. It kills nearly 700,000 of the 350 million that succumb to the infection each year, and the majority of the deaths occur in sub-Saharan Africa.