Insects are small animals that have six legs, three body parts, and a hard exoskeleton. They can be found in nearly every environment on Earth and are essential to the survival of many ecosystems.
More than 50% of all insects are herbivores, meaning they only eat plants. Some of the most important insects, like bees and butterflies, are herbivore pollinators that help plants reproduce. Other insects, like ladybugs and lacewings are carnivores and they eat other harmful insects that could damage crops.
Still, other insects, like dung beetles and termites are detritivores that help decompose organic matter back into the food chain!
Apart from being important pollinators, herbivorous insects also help to keep plants in check and prevent them from taking over. Herbivore insects also provide food for other animals in the ecosystem, such as birds and bats. Without insects, many of these animals would starve to death.
What are insects and what do they eat?
Insects are arthropods belonging to the class Insecta. The study of insects is called entomology. They are found on every continent (except Antarctica), in most climates, and in nearly all terrestrial habitats.
Insects are opportunistic feeders and their diet depends on the species and their environment. Most insects are herbivores and feed primarily on plants. Some common plant foods include leaves, stems, flowers, fruits, and seeds.
Herbivore insects feed on plants do so by chewing small pieces off leaves with biting jaws or by sucking out the sap or nectar from the stems, leaves or flowers of the plant.
Other insects are predators or scavengers and feed on other animals or decaying organic matter.
There are more insect species than any other type of animal, around one million described species (about 30% of all described animal species).
Most haven’t been named or described yet though, and estimates for the actual number range from about 5 million to 100 million or more.
About 400.000 of these species are known to be herbivores, with the next largest group being the carnivores and the smallest group being actual omnivores.
These three groups are not completely set in stone though, as some herbivores might sometimes eat other animals if plant food is unavailable or the nutrient levels are low.
The standing hypothesis for how omnivore insects evolved is in fact that omnivore insects evolved from herbivore insects that lost their access to nutritious plant matter. They then had to feed on other insects to survive!
This ability to switch from a herbivore diet to a carnivore diet is an important feature of many insects that allows them to adapt quickly to changing conditions and food availibility. It is also an important buffer that keeps plant and prey animal populations in check!
What Insects are Carnivores, Herbivores and Omnivores?
There are many examples of insects belonging to the different categories and I am sure you know some of these insects already from around your house?
Important herbivore insects are all those pollinators you see in your backyards like bees, butterflies, and those small black flower beetles!
Some insects that are herbivores are:
- 1. Weevils
- 2. Aphids
- 3. Butterflies
- 4. Caterpillars
- 5. Cicadas
- 6. Leaf miners
- 7. Bees
- 8. Moths
- 9. Grasshoppers
- 10. Many Beetles (like the weevils, leaf beetles, and Longhorned beetles)
Some insects that are omnivores (insects that eat both plants and animals) are:
Examples of insects that are mainly carnivores are:
1. Bed bugs
2. Beetles (such as tiger beetles and rove beetles)
3. Assassin bugs
9. Praying Mantis
10. Doodlebugs (larvae of antlions)
Are Insects Producers, Consumers, or Decomposers?
Because insects need to acquire their energy from other living organisms, plants, or animals, they are consumers and not producers.
Whereas insects are not true decomposers, many help to eat or scavenge dead organic matter to aid the recycling of nutrients back into the food web.
What Type of Consumer is an Insect?
There are four types of consumers: omnivores, carnivores, herbivores, and decomposers. Insects are mostly herbivores and thus mostly primary consumers.
However, insects can be primary consumers, secondary consumers or tertiary because they may eat plants, other animals, and even other predatory animals.
Generally speaking, herbivores are primary consumers, omnivores are secondary consumers and carnivores are tertiary consumers. Quaternary consumers are those animals that are considered apex predators.
Can Insects be Considered Decomposers?
Insects do not eat dead or decaying matter and are therefore not decomposers, but they can be detritivores.
Detritivore insects eat dead plants in the form of leaves, wood (like termites), feces (dung beetles), and soil (earthworms). This helps reuse the nutrients of plants that would otherwise have to go through the slow process of decomposition by microorganisms on their own.
By eating dead plants, insects can speed up this process and offer some of the raw nutrients back to the environment when leaving their feces.
The bacteria in the guts of some insects play a very important role in their digestion and these microorganisms may be considered true decomposers.
Where are Insects in the Food Chain?
Insects sit very low in the food chain because they only eat plants. Animals that only eat plants are primary consumers and are placed on the second trophic level in the energy pyramid.
The energy transferred by an insect is the energy from the grass or other plants that they eat. This energy is transferred to the animals that eat the insect, for example, a grasshopper or an aphid.
This energy is then again transferred to the higher trophic levels via carnivorous insects, for example when the ladybug eats an aphid.
Food chains simply demonstrate how energy moves from one organism to the next, in a straight line.
Are Insects Autotrophs or Heterotrophs?
All insects are heterotrophs because they eat other living organisms. Practically no animals are autotrophic because animals do not get their energy directly from the sun as plants do. That is, animals like insects are heterotrophs and cannot make their own energy!
What Animals Prey on Insects?
Predators of insects include carnivorous insects like spiders, ants, beetles, wasps, and flies but also many larger animals like birds, rodents, and bats eat insects. In fact, bats are the animals thought to eat the most insects in the wild!
Some plants, like the Venus flytrap, will also “eat” insects!
While numerous animals will hunt for and eat insects in the wild, this is not a problem for the insects!
Most insects are numerous and divide fast so most species are not threatened by extinction.
In this blog post, I have looked into the diet of insects! Insects have some of the most astounding diets on the planet, eating everything from other insects, plants, and even other animals!
Of course, it goes without saying that not all insects eat plants, however, there are many species that are herbivores, but what really amazes scientists is the range of animals that insects eat, everything from other insects, to birds and mammals!
They are such an important food source, that drives energy through the food chain and sustains life across the planet! Insects, like those inching mosquitoes might be annoying, but they all have their important function in the ecosystem!
I hope you enjoy reading this article, and I do encourage you to look into my other articles on this blog for more exciting facts about wildlife and animal diets!
Omnivorous Insects: Evolution and Ecology in Natural and Agricultural Ecosystems. Nature Education.
Coll and Guershon. Omnivory in terrestrial arthropods: mixing plant and prey diets. Annu Rev Entomol 2002.
Grimaldi and Engel 2005. Evolution of the Insects.