Mosquito killer is one of the hottest and most effective home products for killing adult mosquitoes. An organic bug repellant is a solid material, applied topically to the skin, clothes, or other exposed surfaces to deter adult insects from entering or landing on that surface. Mosquitoes are pesky pests that can spread dengue fever, yellow fever, and other viruses if they feed on humans or animals. Mosquito killers were created to kill mature mosquitoes that have already laid eggs. The most effective products contain a variety of permethrin, which is known to kill mature mosquitoes and prevent re-infestation.