There are over a million species of insects already discovered and the Royal Entomological Society estimates that there may be as many as another 10 million species that are still to be discovered. Insects are the largest group of organisms in the world and also the most diverse. I wanted to find out how different insects feed.
Insects either use their jaws to bite and chew their food (such as dragonflies) or suck it up using a proboscis (like a butterfly.) Sponging is used by the housefly to soften the food with saliva before absorbing the liquid food.
In this article I look at the different feeding methods for insects and look at a few different insects to see how they feed.
There are two main types of feeding categories that insects fall into. Insects such as ants are chewers which can be seen by the holes they leave in plants. Grasshoppers, dragonflies, and beetles also fall into this category, using their jaws to bite into their prey. Many insects feed not just on plants but also other insects.
Suckers are the second category of insects. Mosquitoes fall into this category as they use their proboscis to suck blood from animals. Aphids also fall into this category as they extract food from plants.
Insects can also be divided into two categories according to their life-cycles, and their life-cycles are reflected in their method of finding food.
Insects fall into these two categories. Some insects such as butterflies transform by completing a metamorphosis through several stages. In the case of butterflies, this occurs when they change from eggs to larvae, before entering pupae and emerging later as a butterfly.
The process is gradual, and the way they feed goes through several stages as well. The larvae do feed, but the pupae do not, but when the butterfly emerges this does.
Insects that do not go through this complete metamorphosis resemble small adults when young, and these feed in the same way and have a similar diet throughout their lives.
This shows that although insects are either chewers or suckers, these may change as they go through metamorphosis.
Here are some examples of how different insects feed.
The froghopper or meadow spittlebug causes small amounts of foam, which is sometimes called cuckoo spit, to appear on plants in May and June. After hatching from these small eggs, these small insects push their stylet into the plant until it finds the water-conducting vessel in the plant, the xylem.
The young insect (nymph) then extracts water from the plant, which passes through its alimentary canal and leaves the body as foam. The nymph then lives in the foam protecting it form predators.
There are small amounts of nitrogenous nutrients in the plant solutions, and the froghopper nymph uses this as food in the foam, until the nymph molts and emerges as an adult. Once they leave the foam, the adults feed less often and the foam dries up.
Another insect that also uses a stylet to suck nutrients is the cabbage aphid. They push the stylet into the plants phloem, which house the energy and nutrient supplies. There are large amounts of sugar in the phloem and the aphids are able to extract this. The sugar passes through the aphids body and is excreted as sugary honeydew. This can e found on the leaves of trees when summers are dry.
Cabbage aphids can be a pest to farmers as they only live on cabbage plants and related plants. When there is a heavy infestation of cabbage aphids, they can drain the energy and nutrients from a plant. Once the supply runs out, the aphids will move onto the next plant.
Wasps feed on nectar and other liquid food, such as the juices from rotting fruit or on the honeydew left behind by the cabbage aphid.
The larvae of wasps develop in the nest and so adults need to supply food to the larvae. A well-established colony of wasps may contain thousands of cells so workers will attack and kill caterpillars, flies, spiders and butterflies in order to be able to feed the larvae.
The seven-spotted ladybird lay small clusters of yellow eggs near aphid colonies. Once the ladybirds have hatched, the larvae move to the nearest aphids and start eating them. As long as there are enough aphids to eat, the larvae grow, forming orange and black pupae attached to plants.
The seven-spotted butterfly larvae are true cannibals, however. If the supply of aphids dries up then they will attack and feed on each other.
Once they become adults, the seven-spotted ladybird continues to eat its diet of aphids, but will fly off on long distances to find food if needed.
Another way of feeding is done by a genus of fly. Although the adults feed on flower nectar, the maggots are parasitic. The eggs are laid in the lining of birds nests during the incubation period. The maggots will hatch usually at the same time as the young birds and will attach themselves by the means of a sucking disc to the underneath of the young birds.
The maggots use their mouth hooks to pierce the bird’s stomach, sucking the blood out. They hide amongst the nest material and it is thought that more than one hundred maggots may be found in a single bird’s nest.
The white-lined sphinx moth goes through a complete metamorphosis, and the larvae feed in a different way to the adults. The caterpillars will feed on the leaves of tomatoes, grape, willow weed, elm and other plants. The caterpillars will consume great amounts of leaves as it is not very nutritious.
In winter the energy and the nutrients from the plants allow the transformation into a moth. The white-lined sphinx moth feeds generally at night, and will use it proboscis to suck the sugar nectar from pale or white flowers as these stand out against the rest of the foliage.
The white-lined sphinx moth is also known as the hummingbird moth as they hover in front of the flow, extracting all the nectar before moving onto the next flower.
Dragonflies do not suck their food, but instead, use their jaws to bite. They generally outfly their prey and then deliver a few bits to kill them. Dragonflies feed on other insects and even smaller dragonflies.
Dragonfly larger lives in water and will eat almost anything that is smaller than themselves. Larger dragonfly larvae are also know to eat small fish. The larvae lives underwater, undergoing a series of moults as it ages. Once the final skin splits, the adult dragonfly emerges.
Houseflies use a method called sponging to get their food. Houseflies do not have jaws so their mouths absorb food like a sponge. Houseflies can only eat liquid food. Houseflies release saliva which is regurgitated from its stomach onto the food which then dissolves it. They then use their straw-shaped tongues to absorb liquid food. Houseflies taste with their feet.