The male Anopheles mosquito is a much maligned and misunderstood creature. Unlike the female of the species, he likes to dine on pollen, nectar, or something sweet, such as sugar. He is also shy around people, unlike the female, which hungers for them. To lay thousands of eggs, the girls need a rich source of nutrients: human blood. As the sisters feed, they can unwittingly pass on the malaria parasite, an organism that attacks the red blood cells of around 500 million people, killing 1 million every year.

To end these female blood feasts, in an attempt to eradicate malaria, scientists at Imperial College London are using genetic modification in an attempt to allow male mosquitoes to dominate. This would deliver a double whammy: a decline in mosquito numbers over the generations and a smaller proportion of females to spread the parasite.

Led by Andrea Crisanti, the scientist who created the first genetically modified Anopheles mosquito, the team is already planning tests in the field, albeit in enclosures. Mr. Crisanti said there are many diehard opponents of this and related work. Biofundamentalists fear that a modified “Frankenbug” could run amok with unintended effects. Their concerns have been fueled by research on modified bugs to thwart Chagas disease, parasite-resistant bees and silkworms that produce stronger silk, as well as the genetically modified, or GM, mosquitoes. Opponents point out that, once in the wild, there is no way to recall these organisms if they cause harm.

However, Mr. Crisanti is relaxed about the risks. “Every one in my lab has been bitten by a GM mosquito, but we are still in pretty good shape,” he says. Although he believes that the potential benefits outweigh the theoretical risks posed by GM bugs, he fully understands the unease. “It is justified, and the burden is on us to reassure people.” But he says there is no evidence of mosquito genes passing to humans.

One old-fashioned attempt to enlist mosquito males in the fight against malaria is already being studied — using radiation to sterilize males and then release them, a method employed to eradicate the screw worm fly from North Africa. But the logistics are daunting; Africa is home to around 100 billion Anopheles mosquitoes. Computer models suggest that eradicating the disease from the continent would require more than 100 billion sterile males to be released, necessitating a colossal “mosquito factory” to be built.

Although the need is desperate, with around 2,000 African children dying daily from malaria, there is much work to do before GM insects are released into the environment. Mr. Crisanti does not want to discuss exactly when this will be. His collaborators, in an unnamed tropical country, are in discussion with local people about the first step, which will be to see how the GM mosquitoes fare with their wild relatives in large enclosures. If the first stage goes well, the next step will be to use GM to tinker with a gene called “doublesex” that plays a role in the way males and females develop: the male form of this gene would be implanted to skew the sex ratio because the males will only sire more males.