Locusts

Between 40 and 80 million insects can be found in a swarm of locusts. Although largely unharmful to people, they can quickly devour acres of crops, and it is difficult to overstate how terrible it must be to contend with 80 million finger-sized grasshoppers.

The year 1874 (or 1875, depending on whose source you read) saw the arrival of the ferocious Rocky Mountain locusts. The swarm didn't have the typical 80 million members. One account places the number of bugs in this one at up to 10 billion, while another places it at much to 120 billion, and it lasted for five days, blocking the light from the sky.

The swarm engulfed many states, including Montana, Wyoming, Iowa, Colorado, Minnesota, Missouri, and Nebraska. They consumed grass, crops, sheep wool, and fence paint, among other things. Crop losses cost 200 million dollars. They broke into houses and consumed any food that wasn't covered by wood or metal. Even the beds and clothes were eaten. Despite the bugs' sinister appearance, they were extinct by the early 1900s.