When people think of genetically modified organisms, food crops like GM corn and soybeans usually come to mind. But engineering more complex living things is now possible, and the controversy surrounding genetic modification has now spread to the lowly mosquito, which is being genetically engineered to control mosquito-borne illnesses.A U.K.-based company, Oxitec, has altered two genes in the Aedes aegypti mosquito so that when modified males breed with wild females, the offspring inherit a lethal gene and die in the larval stage. The state agency that controls mosquitos in the Florida Keys is awaiting approval from the federal government of a trial release of Oxitec’s genetically modified mosquitos to prevent a recurrence of a dengue fever outbreak. But some people in the Keys and elsewhere are up in arms, with more than 155,000 signing a petition opposing the trial of genetically engineered mosquitoes in a small area of 400 households next to Key West.