The Tiny Helpers: Bugs That Love Living in Terrariums
Discover the fascinating little creatures that help bring a miniature ecosystem to life.
One of the things I love most about building terrariums is that no two are ever exactly the same.
Of course, the plants and moss are usually the stars of the show. But spend a little time looking beneath the leaves, between the stones or along the forest floor, and you might discover something even more fascinating.
An entire little world of creatures going about their daily lives.
When people hear that I sometimes intentionally introduce tiny creatures into my terrariums, the reaction is often something along the lines of:
"Wait... you put bugs in there? On purpose?"
Well, yes! And there's actually some fascinating science behind it.
A natural forest floor is a complex living environment. Beneath the greenery, countless organisms are constantly breaking down organic material, recycling nutrients and interacting with one another.
A terrarium gives us a tiny glimpse into that world.
But not every little creature plays the same role, and not every bug is necessarily a welcome guest.
Let's meet some of the fascinating inhabitants you might encounter.
Springtails – The Tiny Cleaning Crew
Collembola
If there is one tiny creature that has earned its reputation as a terrarium favourite, it's the springtail.
These little organisms are often only 1–2 mm long, although their size varies between species. They may appear as tiny white, grey or dark specks moving through the moss and soil.
And here's something interesting: springtails aren't technically insects. They're classified as a separate group of six-legged arthropods called Collembola.
Many springtails have a special forked structure beneath their bodies called a furcula, which allows them to launch themselves into the air when disturbed.
But their real value in a terrarium is what they eat.
Most springtails feed on fungi, algae, microorganisms and decaying organic material.
By grazing on fungal growth and helping process decomposing material, they contribute to nutrient cycling within the soil.
This makes them particularly useful in humid, closed terrariums, where fungal growth can sometimes become a problem.
They aren't a magical cure for mould, but they can certainly be part of a healthy, balanced ecosystem.
Did you know? Springtails are naturally abundant in soils around the world, and their presence is often associated with active soil ecosystems.
Further reading: Colorado State University – Springtails
Woodlice – The Forest Floor Recyclers
Isopoda: Oniscidea
Woodlice are another fascinating group of creatures, particularly in larger terrariums with plenty of leaf litter and hiding places.
And despite their appearance, they're not insects either!
Woodlice are terrestrial crustaceans, making them relatives of animals such as crabs and shrimp.
They prefer moist environments because their respiratory structures need moisture to function effectively.
Their main contribution to an ecosystem is decomposition.
Woodlice feed on fallen leaves, rotting wood, fungi and other organic material, physically breaking it into smaller pieces.
This makes the material more accessible to microorganisms that continue the decomposition process.
In other words, they're part of nature's recycling system.
In a terrarium, smaller species can sometimes make interesting inhabitants, provided there's enough space, food and moisture.
Did you know? Female woodlice carry their developing young in a special brood pouch beneath their bodies.
Further reading: Woodland Trust – The Common Rough Woodlouse
Tiny Centipedes and Millipedes – Friends or Foes?
Chilopoda and Diplopoda
Now, this is where things get particularly interesting for me.
I've often included very small, many-legged creatures in some of my terrariums, which I've generally referred to as tiny centipedes.
I've never noticed them causing significant damage, and they've always seemed quite happy disappearing into the moss and substrate.
But here's the interesting part: centipedes and millipedes have very different diets.
And now I'm rather curious whether I've correctly identified all my little inhabitants over the years!
Centipedes – The Hunters
Centipedes belong to the class Chilopoda.
They are predators, feeding on other small invertebrates such as insect larvae, worms and various soil-dwelling arthropods.
They generally have one pair of legs per body segment and often move quite quickly.
In a terrarium, a tiny centipede may hunt springtails and other organisms that form part of the soil ecosystem.
They don't normally feed on healthy plants, but that doesn't necessarily mean they're ideal additions to every terrarium.
In a small, enclosed environment, introducing predators could reduce populations of beneficial organisms.
Millipedes – The Recyclers
Millipedes belong to the class Diplopoda.
Unlike centipedes, most millipedes primarily feed on decaying plant material.
They generally have two pairs of legs on most body segments and often move more slowly.
Many also curl up when disturbed.
Their feeding habits make them important decomposers in natural environments, although some species may damage tender plants under certain conditions.
So, which ones have I been adding?
That's something I want to investigate a little further!
My experience has been that these tiny creatures haven't caused obvious problems in my terrariums, but that alone doesn't establish exactly what they are or what they're eating.
It's a wonderful reminder that even after years of working with miniature ecosystems, there's always something new to learn.
Until a species is properly identified, I wouldn't recommend intentionally adding it to a terrarium, particularly one containing delicate plants.
Tiny Snails – The Unexpected Visitors
Gastropoda
Every now and then, a tiny snail makes an appearance inside a terrarium.
They can arrive unnoticed on plants, moss or other natural materials.
And while watching a miniature snail explore a glass landscape can be rather charming, their relationship with plants is a little complicated.
Many species of snails and slugs feed primarily on decaying vegetation, fungi and algae, making them part of the natural decomposition process.
Others happily feed on living plants.
This is particularly important in a terrarium containing delicate mosses, miniature orchids or young tropical plants.
A snail that seems harmless today might also reproduce under favourable conditions, leaving you with more inhabitants than you expected.
Personally, I prefer to observe unexpected snails carefully rather than deliberately introduce them.
Did you know? Snails feed using a specialised structure called a radula, covered in rows of tiny teeth that help scrape food from surfaces.
Further reading: Natural History Museum – For the Love of Snails and Slugs
Tiny Spiders – The Quiet Predators
Araneae
Occasionally, a tiny spider may find its way into a terrarium.
Spiders are predators, feeding on insects and other small invertebrates.
In nature, they form an important part of the food web and help regulate populations of other organisms.
Some build webs, while others actively hunt their prey.
But a terrarium is a much smaller and more restricted environment than a forest.
A spider may not find enough suitable food to survive, and its presence could also affect populations of beneficial creatures.
So although spiders are fascinating and often useful in gardens, I don't consider them necessary additions to a planted terrarium.
If one appears, it's worth identifying it and considering whether the environment can support it.
Further reading: University of Minnesota – Spiders and Their Role as Predators
A Little Science: How the Ecosystem Works
Here's where all these tiny creatures become part of a much bigger picture.
In nature, organisms are connected through what scientists call a food web.
Plants produce organic material through growth.
When leaves fall, roots die or other organic matter accumulates, fungi, bacteria and decomposing organisms begin breaking it down.
Springtails and woodlice participate in this process by feeding on fungi, microorganisms and decaying material.
Predators such as centipedes and spiders may feed on some of these smaller creatures.
Meanwhile, microorganisms continue transforming organic material, helping return nutrients to forms that plants can use.
It's a complex network of interactions, even at a very small scale.
And that's one of the things I find most fascinating about terrariums.
A glass container may only be a few centimetres wide, but the biological processes taking place inside it are remarkably similar to those occurring on a much larger scale in nature.
Of course, a terrarium isn't a complete forest ecosystem, and not every natural interaction can be recreated successfully in such a small space.
The aim isn't to include as many organisms as possible. It's to create conditions in which the inhabitants can coexist without overwhelming the system.
For a wonderful introduction to the science beneath our feet, explore the Natural History Museum's guide to life in soil.
Should You Add Bugs to Your Terrarium?
Not necessarily!
A terrarium doesn't need a collection of visible insects or other invertebrates to be successful.
Even when we can't see them, bacteria, fungi and other microorganisms are already involved in the processes happening within the substrate.
For most planted terrariums, I would consider appropriately selected springtails the most useful optional addition.
Other inhabitants require more consideration.
The size of the terrarium, the plants inside, the available food and the environmental conditions all influence whether a particular creature is suitable.
It's also important to avoid introducing unidentified wild organisms, which could carry unwanted pests or pathogens.
And remember, a terrarium is a contained environment. Introducing or removing organisms can have a much greater effect than it would in a large natural habitat.
A Tiny World Worth Exploring
One of the greatest joys of keeping terrariums is discovering how much life exists in such a small space.
Sometimes I find myself looking at a terrarium I've had for years and suddenly noticing something I've never seen before.
A tiny creature moving beneath a leaf.
A springtail hopping across the moss.
A miniature trail winding through the soil.
Or a mysterious many-legged inhabitant disappearing into the undergrowth.
It reminds me that there is still so much about these little ecosystems to discover.
And perhaps that's what I love most about terrariums.
They're not simply arrangements of plants inside glass.
They're opportunities to observe nature, ask questions, experiment and learn.
The more closely you look, the more you realise just how much is happening in a world that fits in the palm of your hand.
Living Art, Perfectly Composed.
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