Can biology beat the mosquito? All very clever, but biology has fought back. Mosquitoes that used to bite people while they were in bed have changed their behaviour, and now hit them in broad daylight and the open air. In 60 countries, mosquitoes have evolved resistance to the chemicals, and no new versions have been approved in the past 30 years. To add to the problem, some have the habit of breeding in old tyres - and the stuff that leaches out of the rubber may itself act as a weak insecticide, so that larvae become cross-resistant to chemicals that have not yet been used in the wild. The malaria parasites, too, have become resistant. Even artemisinin, the Chinese miracle drug recently accepted in a synthetic version by the WHO as equivalent to the version extracted from plants, is losing its power in some places. Four million chemicals have been tested in the lab, and 20,000 do something to kill off the culprit - but none has been passed as safe for humans. Vaccines, too, have a chequered history. They do well against short, sharp diseases such as smallpox, but not against chronic infections like malaria. Forty years" work and millions of dollars mean that one may be available by 2015. Even so, tests suggest that it will protect only a third or so of children treated, and lasts only a year or so - which may save lives, but will never drive the disease out. The malaria parasite is a busy little beast. It takes only 10 minutes to migrate from the bite via the bloodstream (where it is open to attack by the immune system) to the liver (where it is more protected and multiplies with enthusiasm). Then it bursts out again into the red cells, and the symptoms begin. The biggest problem is its amazing diversity. Unlike smallpox or leprosy, which are pretty much global clones, malaria comes with a dizzying array of distinct identities, which means that a vaccine that works against one variant, or in one place, fails against another. Indeed, every patient may carry his or her own unique infection. Also, in a Machiavellian response to their host's (and their doctors") defences, the parasites can also change their personality by shuffling through their wardrobe of coats as they multiply in the red blood cells. An infant bitten many times will gain some general protection (albeit still laden with parasites), but only at the cost of the deaths of many who are less lucky. The battle goes on. Victory might, perhaps, come via a vaccine that acts in the skin or in the liver and stops the attack before it really gets going, but that is years away. New sprays against larvae, and fungi that attack adults, or hormones that disrupt their sex lives, are all being tried. The situation is not hopeless: Turkey, for example, has reduced the annual rate of infection from more than 100,000 people 40 years ago to just four in 2011. Even so, plenty of control programmes have failed over the decades; and most did so for the same reason - not enough money was available to keep the troops in the field. The malaria problem, unlike most others, may be solved by throwing cash at it. Steve Jones's latest book is 'The Serpent's Promise: The Bible Retold as Science" (Little, Brown)