All insects are part of the taxonomical phylum Arthropoda, and they are collectively referred to as arthropods. It is common to see this name misspelled as “anthropod,” but this is not the correct term. They can be found in nearly every environment on the planet, and they currently account for over half of all known living organisms in the world. They have undergone many cycles of evolution depending on the resources available to them. With over one million described species currently living, and millions more estimated to exist, insects greatly outnumber all other animals.
In general, this classification of creatures is referred to as Insecta. In some cases, the terms “Ectognatha” and “Entomida” may be used instead, but these three labels are synonymous and may be used interchangeably. For simplicity, this guide will always use the classification Insecta.
The name Insecta is derived from the Latin word “insectum,” which means “divided body” or “cut into sections.”
Learn about why insects are classified as animals here.
The Four Major Insect Characteristics Listed
Insects are one of the most diverse groups on the planet, and their evolution throughout history is astounding. However, in order to be considered a member of the class Insecta, animals must meet a certain number of criteria. In fact, many people are surprised to learn that many of the bugs that are commonly believed to be insects are technically not a part of the Insecta class.
1. Insects have three distinct body segments.
One of the most well-known defining characteristics of insects is the division of their bodies into three sections: head, thorax and abdomen.
The head features a single pair of antennae and a pair of either simple or compound eyes. This is also where the mouth is located, but the type of mouth is dependent on the type of insect. Mouth variation is one of the main factors used to classify insects. The thorax is the midsection, and this is where the legs and wings are attached. The abdomen houses the digestive and reproductive organs, and it is also where the stinger is located if the insect has one.
2. Insects have six legs.
Unlike other members of the larger phylum Arthropoda that class Insecta belongs to, true insects only have six legs. Arachnids are often mistaken for insects, but they have eight legs. All insects have three pairs of jointed legs that are attached to the thorax of the body.
3. Insects have an exoskeleton.
Insects are classified as invertebrates, which means they have no internal spinal column to provide structure and protection. Instead, they have what is known as an exoskeleton, which literally means “outer skeleton.” These external skeletons are made from a tough, inflexible material called chitin, and they provide the support and protection that would typically come from an internal skeleton.
4. Insects hatch from eggs.
Almost every known species of insect hatches from an egg. For insects, fertilization and development occur inside of the egg, and the eggs of most species are specially designed to withstand harsh weather conditions such as droughts.
Insect Class Exceptions
As with most classification systems, there are a few exceptions to the general rules that govern which species are included in class Insecta.
- Certain species do not lay eggs.
The majority of insects lay eggs that develop and hatch outside of the mother. However, there are a handful of insect species that reproduce via different methods, such as those listed below.- Juvenile aphids, tsetse flies and certain cockroaches are ovoviviparous, which means that the eggs develop inside of the mother and hatch as soon as they are laid.
- Other cockroach species are viviparous, so the young gestate inside of the mother and are born alive.
- Some insect species display polyembrony, which means that one fertilized egg divides into many separate embryos.
- A few species are bioluminescent.
A small number of insects, such as fireflies, are able to generate light that can be used for mating or luring prey. - A select few insects are long-lived.
In general, insects live short lives. While most insects may only live a few days or weeks, the egg-laying queens of some ant, bee and wasp species can live for many decades.
The Life Cycle of Insects
The life cycles of insects are divided into two basic groups: complete and incomplete metamorphosis. Each life cycle has its advantages and disadvantages in terms of evolution.
Complete Metamorphosis Steps Listed
Complete metamorphosis happens in four distinct stages.
- Egg: The female lays fertilized eggs that hatch after a given span of time.
- Larva: This is the growth phase. Larvae spend nearly all of their time eating in order to prepare for their final transformation.
- Pupa: The pupa is the transformation phase. The insect is contained within a hard shell called a chrysalis, and all of the internal organs are broken down into a kind of “soup.” This liquefaction allows the adult body to form.
- Adult: Once the reorganization of the pupa stage is complete, the chrysalis will split open and the fully formed adult emerges.
Incomplete Metamorphosis Steps Listed
Incomplete metamorphosis occurs in lesser-developed insects and happens in only three stages.
- Egg: As with the insects that undergo complete metamorphosis, eggs are laid by the female and hatch into young.
- Nymph: In this stage, the young look like miniature versions of adults, but they cannot reproduce. Wings develop during this stage rather than the pupal stage. Nymphs will undergo a series of molts in order to shed their inflexible exoskeletons as they grow.
- Adult: After a nymph’s final molt, it will have fully developed wings and the ability to reproduce.
Insect List
Ambrosia Beetle
The ambrosia beetle forms a symbiotic relationship with the ambrosia fungi
American Cockroach
Despite its name, actually originated from Africa and the Middle East
American Dog Tick
Main vector of Rocky Mountain spotted fever
Ant
First evolved 100 million years ago!
Armyworm
They are so named because they "march" in armies of worms from one crop to another in search of food
Asian Cockroach
Originally discovered in Japan
Asian Giant Hornet
The largest wasp in the world!
Assassin Bug
The assassin bug is named for its quick strike ability.
Atlas Moth
Adult atlas moths do not eat - they live off fat they stored as larvae.
Australian Cockroach
The most common type outdoor roach in Florida
Banana Spider
People spin clothing and fishing nets out of these spiders’ silk.
Bed Bugs
Bed bugs feed for 4-12 minutes.
Bee
Rock paintings of bees date back 15,000 years
Beetle
There are more than 350,000 different species
Black Wasp
The great black wasp is a species of digger wasp.
Black Widow Spider
They typically prey on insects!
Blister Beetle
Blister Beetles are attracted to lights at night.
Brown Dog Tick
Can live its entire life indoors
Brown-banded Cockroach
Females glue egg cases to furniture
Bumblebee
The most common species of bee!
Butterfly
There are thought to be up 20,000 species!
Cabbage Moth
Cabbage moths are named after the vegetable they find the tastiest.
Cactus Moth
Cactus moths can cause serious damage to cacti in locations where they have no predators.
Camel Cricket
The camel crickets that are found in the USA are light brown in color. They also have dark streaks all over their body.
Camel Spider
Fast, carnivorous arachnid with a painful bite.
Carpenter Ant
Carpenter ants can lift up to seven times their own weight with their teeth!
Caterpillar
The larvae of a moth or butterfly!
Cecropia Moth
Cecropia moths don’t have digestive tracts, so they can’t eat.
Cicada
Cicadas have one of the longest insect lifespans
Cockroach
Dated to be around 300 million years old!
Common Furniture Beetle
The common furniture beetle feeds exclusively on wood
Common House Spider
House spiders have the ability to eat most insects in a home.
Cricket
Male crickets can produce sounds by rubbing their wings together
Cuban Cockroach
Believed to have been introduced to the United States by being shipped with green bananas.
Death’s Head Cockroach
People buy Death's Head Cockroach nymphs and raise them as pets!
Deathwatch Beetle
The adult deathwatch beetle taps on the wood to find a mate.
Deer Tick
Commonly found on white-tailed deer
Desert Locust
Solitary locusts are grey while gregarious locusts are yellow with stripes.
Devils Coach Horse Beetle
The Devil’s coach horse beetle can emit a noxious substance to deter predators
Dog Tick
Dog ticks feed on dogs and other mammals
Dragonfly
It's larvae are carnivorous!
Dubia Cockroach
The most popular species of feeder roach
Dung Beetle
The dung beetle can push objects many times its own weight
Earwig
There are nearly 2,000 different species!
European Corn Borer
Female can lay up to 600 eggs in her 14-day lifespan
Firefly
The firefly produces some of the most efficient light in the world
Flea
Adult fleas can jump up to 7 inches in the air
Florida Woods Cockroach
Often found on palmetto trees
Fly
There are more than 240,000 different species!
Fruit Fly
Fruit flies are among the most common research animals in the world
Glow Worm
Found inhabiting dense woodland and caves!
Gnat
Males form large mating swarms at dusk
Grasshopper
There are 11,000 known species!
Hawk Moth Caterpillar
Many hawk moth caterpillars eat toxins from plants, but don’t sequester them the way milkweed butterflies do. Most toxins are excreted.
Hercules Beetle
This dynastine scarab beetle makes a weird huffing sound when it’s disturbed.
Hercules Moth
Adult Hercules moths don’t eat since they don’t have mouths.
Honey Bee
There are only 8 recognized species!
Horsefly
Horseflies have been seen performing Immelmann turns, much like fighter jets.
Housefly
The fly has no teeth
Imperial Moth
Since the imperial moth doesn’t eat, it does die shortly after it lays its eggs. Its lifespan is only about one week.
Insect
Insects go back over 350 million years, making the creatures older than man, flowering plants and dinosaurs.
Insects
There are an estimated 30 million species!
Japanese Beetle
Can clear an entire fruit tree in 15 minutes in a swarm
Joro Spider
Named after a Japanese spider demon
Ladybug
There are more than 5,000 species worldwide!
Locust
Each locust can eat its weight in plants each day.
Lone Star Tick
Only females have the ‘lone star’ marking
Madagascar Hissing Cockroach
One of the largest types of cockroach
Maggot
Will only live in wet areas
Mayfly
There are 2,500 known species worldwide!
Mealybug
They have a symbiotic relationship with ants.
Mole Cricket
Adult Mole crickets may fly as far as 5 miles during mating season and are active most of the year.
Monarch Butterfly
During migration, Monarch Butterflies may travel 250 or more miles each day.
Mosquito
Only the female mosquito actually sucks blood
Moth
There are 250,000 different species!
No See Ums
There are more than 5,000 species.
Peacock Butterfly
The eyespots on this butterfly’s wings deter predators from attacking.
Pennsylvania Wood Cockroach
Seeks out sources of light
Polyphemus moth
The Polyphemus moth doesn’t eat.
Pond Skater
There are 500 different species!
Praying Mantis
The mantis can turn its head 180 degrees.
Purple Emperor Butterfly
Inhabits deciduous forests!
Puss Moth
Caterpillars squirt formic acid!
Redback Spider
The redback spiders found in New Caledonia differ from other populations in that they don’t practice sexual cannibalism and don’t bite people as much.
Scorpion
There are around 2,000 known species!
Spider Wasp
They prey on spiders to feed their larvae or they parasitize other spider wasps.
Spotted Lanternfly
The spotted lanternfly is often confused for a moth, but it’s actually a type of planthopper
Squash Beetle
Often mistaken for a ladybug
Stag Beetle
The stag beetle consumes rotting and decaying wood when it is in the larva stage.
Stick Insect
There are more than 3,000 different species!
Tarantula Hawk
Tarantula hawks are excellent pollinators, especially for milkweed.
Termite
Their mounds can be up to 9 meters tall!
Tiger Beetle
The adult tiger beetle is one of the fastest land insects in the world
Tiger Moth
The bright colors of this moth are a signal to predators that it has a terrible taste.
Tsetse Fly
Tsetse flies are large biting flies that live in the tropical regions of Africa.
Wasp
There are around 75,000 recognised species!
White Butterfly
This butterfly determines the smell and taste of a flower with its feet.
Wolf Spider
Carnivorous arachnid that hunts its prey.
Wood Tick
Almost always found above 4,000 feet in elevation
Insects FAQs (Frequently Asked Questions)
What are the general features of insects?
Insects are all members of the group Arthropoda, which makes them arthropods. It is not uncommon to see this group mislabeled as “anthropods,” but the correct spelling is “arthropod.”
In general, insects share all of the following common features:
- An exoskeleton
- A pair of wings
- A segmented body
- Six segmented legs
- One pair of compound eyes
- One pair of antennae
What is an insect?
An insect is an arthropod that has distinctive characteristics such as three body segments, six jointed legs, one pair of antennae, one pair of compound eyes and an exoskeleton.
How many legs does an insect have?
All true members of class Insecta have three pairs of jointed legs.
What is the life cycle of an insect?
Depending on the species, insects experience either complete or incomplete metamorphosis. The stages of complete metamorphosis are egg, larva, pupa and adult. The stages of incomplete metamorphosis are egg, nymph and adult. Insects generally have short life cycles that may last a few days or a few weeks.
Are spiders insects?
Spiders are not a part of the class Insecta, but they are part of the larger group of arthropods. Some people incorrectly label this group as “anthropods,” but this is not quite right. Because they have four pairs of legs instead of three and only two distinct body segments, they belong to the class Arachnida.
What are the largest flying insects in the world?
The largest flying insects in the world are often beetles like the titan and goliath beetles. When it comes to wingspan, contenders include the white witch and Atlas moths. Other surprisingly large flying insects include tarantula hawks and giant water bugs.
