There are a few key differences between insects and worms. However, there are also a few species that cross the lines between invertebrates, worms and insects.
In this article, we explore the differences between worms and insects, what makes worms invertebrates, and what exactly makes them unique, but first..
Is a Worm an Insect?
Earthworms are not insects. But some insects have been given the “worm” name, which is technically incorrect, such as Agave worms or inchworms which are actually insect larvae (beetles). Most insects generally have an exoskeleton protecting their organs, with six legs which they use to move and two antennae. Worms do not have any limbs and have soft bodies with no exoskeleton. They use their segmented or unsegmented musculature to move around.
Due to their small size, habitat, and nutrition, it is no wonder why people call worms insects in everyday language.
Let’s explore the differences in the table below and then answer the most common questions in more detail..
|Body Cavity||Yes – haemocoel||Yes – haemocoel|
|Do They Molt?||No||Yes|
|Different Body Sections?||No||Yes, usually three|
Is a Worm a Bug or An Animal?
Yes, an earthworm or other types of worm are often unofficially called bugs. “Bugs” are a non-scientific term used to classify many types of small creatures.
Worms and insects both belong in the Kingdom Animalia, meaning that they are both considered animals.
We explain this concept in more detail inside our in-depth article, are worms animals?
But below the animal kingdom, their phylum is different.
Phyla is a hierarchy used to classify different animals just below kingdom level.
Worm and Insect Phyla
Most common types of land worms belong to the phylum annelida. For example, the earthworm which is a segmented worm.
Nematodes (for example, roundworms) belong to the phylum nematoda. This type of worm has an unsegmented body which is cylindrical with tapered ends.
Insects belong to the phylum arthropoda and the biggest group in the arthropod phylum is the class insecta.
You may have heard some insects called arthropods and that’s because of the phylum they belong to.
A marine worm is used to classify all worms who live in water.
The different species of marine worms can be found in many different phyla such as the phylum platyhelminthes (like flatworms), phylum annelida, phylum nematoda, nemertea (ribbon worms) and more.
What About Bugs?
The term insect, or bug, is typically very loosely applied to any small or microscopic animal that we can find in the ground, on the surface of the soil, or even flying around us.
People commonly use the term “bug” to encompass everything from:
- parasitic worms
- bristle worms
- velvet worms
- teredo worms
And more, but as we mentioned earlier, the term “bug” is a non-scientific term.
In truth, most worms are not insects at all.
However, these little creatures and insects, too, all belong to the animal kingdom.
There are six major groups in the kingdom animalia : mammals, fish, birds, reptiles, amphibians, and invertebrates.
Whereas the other five categories of animals are vertebrates (meaning that they have a bone structure in their bodies), worms AND insects are invertebrates (meaning that they have no bone structure).
This is a similarity they do share.
In this category, you will also find jellyfish, octopuses, coral, etc.
Other invertebrate groups include invertebrate insects, too.
Insects are partially defined as being animals with bodies divided into three distinct areas: the head, the abdomen, and the thorax.
Within the invertebrate insect family, you will find ants, bees, flies, the praying mantis, crickets, ladybirds and similar insects.
There are plenty of other animals in this line, and they are perhaps seen as more diverse in look and behaviour than worms. But no – they are not worms.
What Type of Insect Is a Worm?
Although there are indeed invertebrate insects, worms definitely are not insects.
Even segmented worms (i.e. annelids) do not have the same distinct body sections that insects do.
Worms are typically classified into three distinct groups.
- The first group being flatworms (no body cavity or segments)
- The second group being roundworms (have a body cavity, but no segments)
- The third group being segmented worms. (Are segmented and have a body cavity)
We have a post explaining the differences between earthworms vs flatworms.
Although each group consists of invertebrate animals, the worms vary in:
- appearance and body type
- habitat (living habitats such as damp earth, the surface of the soil, or salt water, fresh water, etc.)
- and nutrition (i.e. do they eat live organic matter or decaying substances)
Earthworms, in particular, are free-living segmented worms that live in the soil and feed on decaying organic matter.
They play a vitally important role in feeding other animal species, including some insects and directly or indirectly, all of the people living in the world!
Although other worms can prove to be a detriment to nature, such as parasitic worms, the common earthworm is undeniably essential to life on earth.
From the marine nemertean worm to the bootlace worm – they’re not insects at all.
Generally, if they are called worms, they are invertebrates.
That goes for the African giant earthworm, spiny headed worms and more, too.
What Is the Difference Between Worm and Insect?
As stated, worms are different from insects as their bodies do not have three distinct areas
- the head (ever wondered if worms have eyes and ears on their head region?)
- the abdomen
- the thorax.
Instead, they have elongated bodies that do not differ in size throughout the length.
Insects also have exoskeletons that are used to support their bodies.
Although the word “skeleton” will often make us think of bones and cartilage, exoskeletons are often made up of protein, calcium, and chitin.
This is the case with invertebrate insects such as ants, bees, ladybirds, etc.
Another difference between worms and insects is that worms breathe through their skin.
Indeed, worms do not have lungs as we humans do.
That is why them being in a moist environment at all times is essential to their comfort and their survival.
On the other hand, other invertebrates, such as invertebrate insects, breathe through their abdomen in tubes called the tracheae.
Finally, insects often have six legs that are all jointed. This is also the case with invertebrate insects.
In contrast, worms do not have legs or limbs.
In summary, the term worm isn’t generally used to describe an insect. They are different.
But some insect larva which have commonly been given the name of “worm” actually are insects, such as the tomato hornworm.
When it comes to defining certain animals and differentiating them from one another, the task can seem a little daunting, especially comparing worms vs insects.
Many creatures have similar features, lifestyles, and diets, making us assume that they are a part of the same family, when in fact, they could not be more different.
Earthworms happen to be in a league of their own called annelida. They are fascinating creatures that are quite literally responsible for life on earth.
However, their friends, the insects, play just as much of an important role, and invertebrate insects have their place in the circle of life, too.
As long they live, all of these creatures have a role to play and need to be treated with as much respect as we would assume that we humans deserve.