The grasshopper's diet consists of plant foliage, especially grasses and spurges. It eats roughly half of its body weight in plants every day, according to About.com. The vast majority of grasshoppers are polyphagous, which means they are able to eat many types of plants. Only one of the 8,000 grasshopper species relies on one single plant species, making it monophagous.
Some grasshoppers eat from a single plant in a day, while others prefer to feed from multiple host plants. Grasshoppers have salivary glands that chemically digest the carbohydrates in the plant matter they eat using enzymes, including protease, lipase, amylase, invertase and others, depending on the grasshopper's diet.
When grasshopper populations become crowded, a swarm can defoliate an entire agricultural landscape, utterly destroying many farmers' crops. Every year, grasshoppers cause billions of dollars worth of damage to grazing lands all over the world, according to About.com.
Contrary to popular knowledge, grasshoppers are able to fly, in addition to their powerful jump. They use their ability to fly to escape predators. Grasshoppers sometimes spit a brown liquid, which scientists believe is a self-defense mechanism used to drive away predators. Their green color also allows them to hide effectively in planted areas.