Take the case of preventive work to combat the mosquito which carries dengue fever. A survey in Thailand discovered that when people sprayed adult mosquitoes with pesticides, total egg production fell, but the number of offspring which survived actually increased because of the decline of competitors, and the number of disease-carrying mosquitoes ultimately grew.
以登革熱病媒蚊﹘﹘埃及斑蚊的防治為例，泰國的一項調查發現，當人們用藥劑噴灑斑蚊成蟲時，成蚊的產卵密度減少，存活的幼蟲和蛹因競爭對手減少，數量反而增加，病媒蚊也隨之增加。