Insects eat by chewing their food and piercing their food and sucking out the nutrients. They also use their mouthparts to lacerate the food, then suck out the nutrients. Some combine chewing and lapping their food. Others also sponge their food up or siphon it.
Insects that chew their food include dragonflies and damselflies. Indeed, they get their scientific name, odonata, from the teeth found in their mandibles. Their labium can also be everted to catch prey and draw it into their mouths.
Insects that pierce their food and suck out nutrients include robber flies, mosquitoes, aphids and leafhoppers. However, their diet is quite different. Female mosquitoes need a blood meal, but aphids and leafhoppers suck the juices from plants. Robber flies prey on other insects.
Houseflies also sponge up their food because the structure at the end of the proboscis acts very much like a sponge.
Female horseflies use knife-like mouth parts to lacerate their prey before they suck up the liquid, which is often blood. Like the mosquito, this type of fly needs a blood meal before she lays her eggs.
Some types of wasps, including yellow jackets, both chew and lap their food. Moths and butterflies are famous for having a coiled proboscis that unfurls so that they can siphon nectar from flowers.