Mrs. Frizzle's class challenges Mr. Order's class to a science contest, where the topic of the contest is magnetism.

When Wanda brings her pet ladybugs to school to find out how to take care of them, Ms. Frizzle takes the opportunity to show the kids the perils of insect life. Not only do lots of insects eat each other for lunch, but there are lots of other surprises when it comes to the world of Insect Invaders.