Well, they couldn’t survive the heat of a nuclear blast at ground zero, but their resistance to radiation may surprise you. In fact, most insects are much more resistant to ionizing radiation than mammals. Radiation is measured in units called Grays. Doses as low as three to six Grays were fatal to humans in Hiroshima and Chernobyl. By comparison, some adult cockroaches have survived doses up to nine-hundred Grays! That’s more than 150 times the lethal dose for humans!