Entomological warfare (EW) is the use of insects as weapons to disrupt supply lines, destroy crops, or damage populations. There is a record of limited validated use of EW against China in WW2 but the concept is ancient with several recorded instances. EW can be used in three ways: insects as direct weapons, insects as crop destroyers and insects as disease vectors. Other historical examples include plague-infested fleas during the Black Death in the 14th century and ancient warfare where pots were filled with scorpions. The use of insects as biological warfare agents is generally banned in modern international law but countries such as Japan, Germany and the U.S. have experimented or adopted programs for the use of insects as biological agents during warfare. The potential of EW has grown with advances in technology. Genetically engineered insects for military applications have been discussed.