Most insects eat plants but about one in three feed on other animals. All of the insects are quite choosy about what they eat.

At different stages in their lives insects that feed plants may feed on different parts of the plant. A caterpillar might feed on a plant's leaf while the butterfly that it grows into may feed on the nectar in the flowers on a plant.

Insect that eat animals most often feed off of other small insects for their food. Mantids and some beetles hunt other insects like grasshoppers and ants, while dragonfly nymphs catch most other water insects. Some insects like the female mosquito, don't have to chew to feed even though they live off of other animals. They suck up the blood of other animals including humans. The male mosquito feeds on juices they suck from plants while the larvae chew small plants or animals.

Insects have different types of mouths according to what they eat. Many have strong jaws that can grab and hold things as well as cut up an chew their food. Plant eaters like grasshoppers have these jaws as do the mantids that eat the hoppers.

A number of insects have special hollow sucking tongues. These include butterflies and moths. They unroll the tongue or proboscis, into flowers and suck up the nectar from the flower.

Some other insects like the fly squirt out some saliva juice onto their food so that the food dissolves. When the food has dissolved the fly sucks the juice up.