Japan used entomological warfare on a large scale during World War II in China . Unit 731 , Japan 's infamous biological warfare unit led by Lt. General Shirō Ishii , used plague-infected fleas and flies covered with cholera to infect the population in China . The Japanese military dispersed the insects by spraying them from low-flying airplanes and dropping bombs filled with a mixture of insects and disease . Localized and deadly epidemics resulted and nearly 500,000 Chinese died of disease . An international symposium of historians declared in 2002 that Japanese entomological warfare in China was responsible for the deaths of 440,000
Unit 731
Unit 731
Entomological warfare