While there are a million different types of insects, all have a hard exoskeleton which is segmented into three parts. In fact the word "insect" is derived from the Latin meaning segmented.
How Houseflies Work
Swat it, smash it, spray it. It's tough to get rid of the world's most annoying roommate: the housefly. But at least the housefly won't steal your food -- whoops, never mind.