The Martian Chronicles Lesson Plan

Why does the author compare the rockets filled with humans coming to Mars as "locusts"? What are locusts (on Earth) and what do they do? What effect do these human "locusts" have on Mars?

The author describes the humans as locusts because of their huge numbers--they swarm as locusts do. Locusts are insects that, at certain times, gather and travel in enormous numbers (up to millions in a single swarm). Locusts are highly destructive. They alight on fields of grain crops and eat them to death, destroying everything that lives and grows. Thus the author refers to humans on Mars as locusts not just to describe their swarming numbers but to infer their utter destructiveness...