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 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 name on these animals has changed. A 2025 revision kept Merulanella for three species from New Caledonia, none of them in the hobby, and created the new genus Ardentiella for two species from Myanmar. Most of the colourful Southeast Asian species in the hobby - the ones everyone knows as "Merulanella" - are now sold as Ardentiella, where they sit as undescribed species. You'll see both names used for them in the trade, though a few animals once sold as Merulanella, such as Sinodillo sp. 'China', are now sold under other genera. 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. Ardentiella is known from eastern Myanmar and western Thailand to Yunnan, Laos and Vietnam, and the hobby's lines are undescribed species from Vietnam and western Thailand. Their care follows from that warm, humid - but not sweltering - origin.
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 do best at about 20-23°C. They don't want to be cooked - excessive heat is a common cause of failure.
- Humidity: roughly 60-75%, with a moisture gradient from damp to drier 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. Lichen on twigs or bark is worth offering; ours graze it, though we have found nothing published that says any woodlouse needs it. 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, since woodlice build a calcium carbonate cuticle. Remove uneaten fresh food before it moulds.
Are They Good for Beginners?
No - and it's worth being clear 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?
Not quite. The 2025 revision kept Merulanella for three species, none in the hobby, and most of the colourful animals once sold as Merulanella are now sold as Ardentiella, where they sit as undescribed species; a few, such as Sinodillo sp. 'China', are now sold under other genera.
Where are Merulanella isopods from?
Tropical Southeast Asia: Ardentiella runs from eastern Myanmar and western Thailand to Yunnan, Laos and Vietnam, and the hobby's lines come from Vietnam and western Thailand. 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 (best at about 20-23°C) 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 worth offering. 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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