Merulanella isopods are some of the most spectacular and sought-after isopods in the hobby - vivid, active, tropical woodlice in fiery reds, yellows and blacks that genuinely turn heads. They're a world away from the plain grey woodlouse in your garden. If you've been admiring morphs like Red Diablo, Scarlet, Tricolor or Yellow Arrow, this guide explains what they actually are, where they come from, and what keeping them involves.
One important thing up front: the genus has been renamed. In 2025 the old genus Merulanella was reclassified, and all the colourful Southeast Asian species in the hobby - the ones everyone knows as "Merulanella" - were moved into a new genus, Ardentiella. You'll see both names used interchangeably in the trade; they're the same animals. We list them in our Ardentiella (ex Merulanella) collection to make that clear.
What Are Merulanella (Ardentiella) Isopods?
These are terrestrial isopods - land-living crustaceans, relatives of the common woodlouse - in the family Armadillidae. The hobby ones are prized for their striking colouration; in fact the new genus name Ardentiella comes from the Latin ardens, meaning "burning" or "fiery," after the bold red, yellow and black markings so many of them display.
They're a decent size for a display isopod - typically around 15-20mm as adults - and, unusually, they're bold and active, often out and visible by day rather than hiding away like many species. That visibility, combined with their colour, is exactly why they're so prized. They are not, however, beginner isopods: they're intermediate-to-advanced animals that reward keepers who get their specific conditions right.
Where Do They Come From?
This is where a lot of older information online gets it badly wrong: Merulanella/Ardentiella are tropical Southeast Asian isopods, not American ones. The hobby species come from Vietnam, China, Myanmar, Thailand and Laos. Understanding that warm, humid - but not sweltering - origin is the key to keeping them well.
Caring for Merulanella (Ardentiella) Isopods
These are rewarding but demanding isopods, and a few specifics matter more than they do for hardy beginner species:
- Temperature: around 19-26°C, and they tend to prefer the cooler end. They don't want to be cooked - excessive heat is a common cause of failure.
- Humidity: roughly 60-75%, with a proper moisture gradient so they can choose. Moist, not waterlogged.
- Ventilation: high. Good airflow is important - stagnant, stuffy conditions encourage the mould and crashes that kill colonies.
- Enclosure: secure and escape-proof, ideally with some vertical structure (cork bark, wood) since they like to climb.
- Substrate: a moisture-retaining base topped with plenty of leaf litter and decaying hardwood.
Get that balance - cooler, humid, well-ventilated, with a gradient - and they're far more rewarding to watch than most isopods. Get it wrong, particularly too hot or too stuffy, and they're unforgiving, which is why they're not recommended as a first species.
What Do They Eat?
Like all terrestrial isopods, Merulanella are detritivores, with a staple of decaying leaf litter and rotting wood that can be left in permanently. They particularly appreciate lichen, which is worth offering regularly for this genus. Supplement with small amounts of vegetables and fruit (carrot, mango and the like), a protein source (fish flake, dried shrimp) once or twice a week, and a permanent calcium source such as cuttlebone for healthy moulting. Remove uneaten fresh food before it moulds.
Are They Good for Beginners?
No - and it's worth being honest about that. Their colour and boldness make them very tempting, but they're sensitive to heat and poor ventilation, breed more slowly than hardy beginner species, and need their conditions kept in a fairly specific range. They're best suited to keepers who already have some experience with easier isopods and want to step up to something special. For a full species-level walkthrough, see our Red Diablo care guide. If you're new to the hobby, cut your teeth on a hardy species first, then come back to these once you've got the basics dialled in.
Frequently Asked Questions
Are Merulanella and Ardentiella the same thing?
Yes. The genus formerly called Merulanella was reclassified in 2025, and the colourful hobby species were moved into the new genus Ardentiella. You'll see both names used for the same animals.
Where are Merulanella isopods from?
Tropical Southeast Asia - Vietnam, China, Myanmar, Thailand and Laos. Despite what some older articles claim, they are not from the Americas.
Are Merulanella isopods good for beginners?
No - they're intermediate-to-advanced. They're sensitive to heat and poor ventilation and breed slowly, so they suit keepers with some experience rather than first-timers.
What temperature and humidity do they need?
Around 19-26°C (they prefer the cooler end) and 60-75% humidity with a moisture gradient, plus high ventilation. Avoid letting them get too hot or too stuffy.
What do Merulanella isopods eat?
Mainly decaying leaf litter and rotting wood, with lichen especially appreciated. Supplement with a little veg and fruit, occasional protein, and a permanent calcium source like cuttlebone.
Why are they so prized?
For their vivid red, yellow and black colouring and their bold, day-active, often climbing behaviour - they're far more visible and showy than most isopods, which makes them stars of a display setup.
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