Spiritually, locusts signify divine retribution, a force that cannot be opposed, and also a misuse of resources. As a flying insect, the locust can signify scattered thought and concepts that have not been properly thought out and marshalled. Put together, they may be a very powerful tool, albeit somewhat dangerous. The image of a plague of locusts is so strong in Western thought that even in dreams it has come to represent retribution for some misdemeanour. You might also like to consult the entry for Insect.