These are particularly notable for the blood-sucking propensities of the
female. Some tropical mosquitoes disseminate the germs of such diseases
as malarial fever. Wholesale destruction of the early stages, by pouring
petroleum on the surface of the stagnant water in which they live, has
been employed with conspicuous success at Havana and in the Panama Canal
zone as a preventive measure against yellow fever and malaria.
Midges are very minute gnats, of which the aquatic larvæ are known as
blood-worms.