Are Isopods Insects or Crustaceans?
Many people first see isopods in gardens, forests, or terrariums and assume they are insects. They are small, crawl on land, and live in leaf litter, so the confusion is understandable.
However, isopods are not insects. They are actually crustaceans, which means they are more closely related to shrimp, crabs, and lobsters than to beetles or ants.
If you're looking to buy isopods in the UK or simply want to understand how to care for them properly, knowing this difference matters. Their crustacean biology explains why humidity, habitat structure, and diet are so important. For a full care overview, see our isopod care guide and isopod habitat setup guide.
What Are Isopods?
Isopods belong to the scientific order Isopoda, which sits within the crustacean class Malacostraca. This class also includes familiar marine animals such as shrimp, crabs, and lobsters.
The name “isopod” means “equal legs”, referring to the similar-looking pairs of legs along much of the body. There are thousands of known isopod species, including marine, freshwater, and terrestrial forms.
Many of the species kept by hobbyists come from genera such as:
- Armadillidium – hardy rollers that can tolerate slightly drier zones
- Porcellio – active surface roamers with strong feeding responses
- Cubaris – burrowing, humidity-loving collector species
You can browse a wide range of isopods available in the UK, including beginner species and more specialised tropical varieties.
Why Isopods Are Not Insects
Although isopods live on land like insects, several major biological differences separate them.
Body Structure
Insects have three main body sections: head, thorax, and abdomen. Isopods have a more segmented crustacean-style body with multiple similar sections.
Number of Legs
- Insects: 6 legs
- Isopods: 14 legs
This is one of the easiest ways to tell them apart. Isopods have seven pairs of walking legs, which is typical of crustaceans.
Antennae
Insects usually have one visible pair of antennae. Isopods have two pairs, although one pair is much smaller and less obvious.
Respiration
Insects breathe through tracheae, while isopods use modified gill-like structures. This is why they depend on moisture and do poorly in dry environments.
For more on this side of care, read our guide on isopod humidity guide: getting moisture levels right.
How Are Isopods Related to Shrimp and Crabs?
Because isopods are crustaceans, they share an evolutionary history with aquatic animals such as shrimp and crabs. Over time, some lineages adapted to life on land while still retaining many crustacean traits.
- Gill-like respiratory structures
- A segmented exoskeleton
- Multiple pairs of legs
- Regular moulting as they grow
That is why terrestrial isopods still prefer humid microhabitats and why enclosure design matters so much in captivity.
Why Moisture Matters So Much
Because isopods evolved from aquatic ancestors, they still rely heavily on moisture. In the wild, they are usually found in leaf litter, rotting wood, moss, and under bark where humidity stays stable.
A good captive setup should recreate those same functional zones:
- Leaf litter feeding layer for food and cover
- Bark shelter zone for hiding and protection
- Moss humidity pocket for hydration and moulting support
- Open substrate area for active movement and feeding
- Calcium source area for healthy exoskeleton development
To build these zones properly, many keepers use leaf litter and cork bark, alongside materials from our isopod supplies collection.
Why Do Some Isopods Roll Into a Ball?
Some species, especially those in the genus Armadillidium, can roll into a tight ball when threatened. This behaviour is called conglobation.
It helps protect their softer underside and reduces moisture loss. This is one reason Armadillidium species are so popular with beginners and display keepers.
If you want species with that classic pill bug behaviour, explore Armadillidium isopods. If you prefer highly active surface species, Porcellio isopods offer a very different style of behaviour.
Why This Matters for Keepers
Understanding that isopods are crustaceans, not insects, helps explain why care advice differs so much from insect care. They need stable humidity, organic substrate, leaf litter, shelter, and a habitat that supports natural behaviour.
This also explains why they are so useful in terrariums and vivariums. As crustacean decomposers, they break down waste and support healthy substrate ecosystems. You can read more in why isopods are important in bioactive setups.
Final Answer: Are Isopods Insects?
No, isopods are not insects. They are terrestrial crustaceans that share more in common with shrimp and crabs than with beetles or ants.
That crustacean biology is exactly what makes them so interesting to keep. It shapes their behaviour, their habitat needs, and the way they function in natural and bioactive systems.
If you're ready to explore species for your own setup, browse isopods for sale in the UK and choose a species that matches your enclosure and experience level.
