The idea of using sterile males was first written about by the Russian geneticist A.S. Serebrovsky in 1940 but the English speaking world came up with the idea independently and applied it practically around the 1950s. Raymond Bushland and Edward Knipling developed the SIT to eliminate screw-worms preying on warm-blooded animals, especially cattle. They exploited the fact that female screw-worms mate only once to attack screw-worm reproduction. The larvae of these flies invade open wounds and eat into animal flesh, killing infected cattle within 10 days. In the 1950s, screw-worms caused annual losses to American meat and dairy supplies that were projected at above $200 million. Screw-worm maggots can also parasitize human flesh.