What are harmful insects?

Harmful insects are insects that are harmful in any way to plants, animals or humans. There are many ways in which insects can be harmful to the above; insects such as locusts can form huge swarms that can destroy whole crops in minutes. Other insects can pierce a leaf or stem of a plant and suck out its juices, leaving the plant to wither and die. Various types of insect carry diseases such as malaria and encephalitis which leave many children in developing countries orphaned and many parents childless.