Female mosquitos need to suck the blood of animals to survive. As part of attempts to develop mosquito repellents, scientists have studied the parasitic habits of mosquitos in detail. The result is repellents that actually work pretty well.
If trapped in an empty cage, a swarm of mosquitos will settle down on the walls on the cage and do nothing much. However, about every hour, half the mosquitos will detach from the wall and fly to another part of the cage. This mosquito rest half-life reminds scientists of the half-life of radioactive substances – the duration after which half the material decays.
When the cage is filled with high concentrations of carbon dioxide, the rest half-life drops from an hour to about six minutes. Mosquitos are much more active. This is because carbon dioxide is released by animals when they exhale, giving away their presence. However, this burst of activity does not last forever – after a while, the mosquitos get used to the carbon dioxide and return to their old rest half-life.
The next stage of experimentation involved a swarm of mosquitos in a wind tunnel with three different cylinders. One of the cylinders was warm, one was wet, and one was warm and wet. After some carbon dioxide was released into the tunnel to stir up the mosquitos, it was found that about 93% of the mosquitos landed on the cylinder that was warm and wet.
Once it was thought that mosquitos found their targets by sensing their distinct odor. This has subsequently been found to be false – mosquitos actually find their target based on warmth, moisture, and carbon dioxide in the air. Mosquito repellents, such as dimethyl phthalate, work by scrambling the biological radar of mosquitos, making them insensitive to carbon dioxide. Repellents are pungent odors to mosquitos which make them desensitized to their prey.
