Quick answer: Shiro Utsuri isopods (Nesodillo sp. 'Shiro Utsuri', listed in the hobby as Nesodillo arcangelii by many and until recently as a Cubaris) are a Taiwanese isopod of 15 to 20mm, white with black markings that vary from a light scatter to heavy patches. Keep them at 22 to 26°C, which in a British house means a heat source on a thermostat for most of the year; below the band they slow down and a colony does not build. Give them 60 to 80% humidity as a gradient, a damp end and a drier one with air moving over the top, a deep substrate they can eat with calcium in it, and a pinch of protein each week, which they take with more enthusiasm than most isopods. Easy on our panel, prolific once settled, out on the surface in daylight, and the tropical isopod I point beginners at. Ours are captive-bred here in the UK.
A lot of the tropical isopods on this site are cave animals that want stable conditions and are not a first isopod. The Shiro Utsuri is the exception, and it is why I recommend it so often. It wants tropical warmth and damp air, so it teaches the habits you will need for the harder species, but it forgives the mistakes you will make while learning them, it breeds while you learn, and it spends its time out on the bark where you can see it. If you want a tropical isopod that is not a gamble, start here.
What a Shiro Utsuri Actually Is
Nesodillo is a real genus, erected by Verhoeff in 1926 in the family Armadillidae, with around twenty-five described species spread across South and Southeast Asia and the Pacific, Taiwan among them. A lot of sellers and care sites file this animal under one of those species, Nesodillo arcangelii Verhoeff, 1928, and the same name gets used for the Silver Ghost, which tells you how loosely it is applied. We list it as Nesodillo sp. because I have not been able to find a published identification: nobody appears to have compared a Shiro Utsuri with the type material in print, and until someone does the species name is the hobby's best guess rather than a fact. It travelled for years as Cubaris sp. 'Shiro Utsuri', and you will still see that label; our guide to the types of Cubaris explains how many animals that label has covered.
The sources that give an origin give Taiwan, and none of them says where on the island. One care sheet places them around shallow ponds and streams, which I cannot confirm and pass on as hearsay. What matters for a keeper is that Taiwan is subtropical rather than tropical: this is not a cave animal, and it did not evolve in a place where the temperature never moves. That is the root of its easy reputation.
The Name, and Why It Is Backwards for Most of Ours
Among koi keepers a Shiro Utsuri is a black fish with white markings laid over it. The isopod wears the pattern the other way round. Ours are white animals with black markings, and how much black varies from one to the next: some carry heavy slate-grey patches and many carry a scatter of dark marks over a translucent white ground. Our own photographs show that spread, from a lightly marked adult on cork to a heavily marked one between pieces of rotten wood with a plain white youngster beside it, and the plain white youngster is the clue that the pattern comes in later. The koi keeps the black ground; the isopod inverts it, and every animal carries its own black signature.
The build is the classic Armadillidae one: a domed, tidy body of 15 to 20mm as an adult, a rounded face, white legs and antennae, and a tight roll when startled that leaves the markings on show. Unlike most of the tropical group it is not secretive. The animals in our photographs are sitting on bark in daylight, and that is how they behave in a settled tub. One source describes them as nocturnal. Ours are out in the day, in the photographs and in the tubs.
Warm, Not Hot, and Why It Forgives You
Our care panel gives 22 to 26°C, and that is where I keep them. The reason the Shiro Utsuri copes with more than a cave species is where it comes from. Lowland Taiwan sees winter days in the mid-teens and summers near thirty, so whatever corner of the island this animal lives in, it is built for a year that swings. The caves the Thai Cubaris come from were measured at 23 to 25°C all year round, so a cave species has almost no seasonal swing to cope with; a Shiro Utsuri has a margin on both sides.
That margin is not a licence to skip the heating. Measured across 823 English houses, the heating-season average is 19.0°C, December sits at 18.1°C, and July and August reach about 21.5°C, so a British room sits below the band for most of the year. Below the band they slow down, and I would not expect a colony to build there; inside it, at 22 to 26°C, they breed. I run a heat cable along the back of my racking on a thermostat, which holds a row of tubs inside the band, and for a single tub a low-wattage mat on a thermostat against one side does the same job, never underneath, so the animals keep a cooler edge to retreat to. The one room to avoid is the unheated one in January. In a July heatwave the job reverses: heat off, coolest room, out of the sun, and keep the damp end damp, because heat dries a tub before it cooks it. Our heating guide covers the equipment, and our seasonal care guide covers the British year end to end.
Damp Air and a Dry End
The panel's 60 to 80% is a gradient, not a target for the whole tub. Hold one end damp at the top of that range with sphagnum and a light misting, and let the far end run drier under dry leaf litter. The dry end has to sit at the bottom of the band, around 60 to 65%, and not just a little less damp than the wet end. The one humidity-response measurement I know of is on a temperate Porcellio, and it showed no response unless part of the enclosure sat below about 65%. Nobody has run that test on this animal, but it is the reason I would not hold a whole tub at 75%. Our humidity guide explains the gradient and how to read it.
A gradient only survives in a tub that breathes. Seal the lid and the moisture equalises, the dry end disappears and mould moves in. My own tubs carry large vents, two to four on each, and an oscillating fan moves air across the racking through the day. A Shiro Utsuri wants cross-ventilation, and what it must not have is still, wet air. Our ventilation and humidity guide goes through the mechanics, and the mould guide covers what happens when the air stops moving.
Substrate and Calcium
Build the substrate 5 to 8cm deep on organic topsoil, flake soil and white-rotted hardwood, a base the animals can burrow into and eat, rather than coco coir, which holds water and offers no food to an animal that eats its substrate. Keep calcium in the tub permanently as cuttlebone or crushed shell, because a colony short of it moults badly. Our substrate guide has a working mix and our calcium guide covers the choices. Over the top goes a generous layer of hardwood leaf litter, with magnolia doubling as food and cover, and cork bark for the animals to sit out on, which they will.
Feeding, and the Protein Point
Leaf litter and rotting white wood are the diet and should never run out; top them up as they vanish rather than to a timetable. On top of that base I offer a piece of carrot or courgette once a week and a little protein about as often, fish flake, dried shrimp or an isopod blend. One care sheet describes a strong feeding response and a preference for protein over the vegetables. Treat that as a preference rather than a greater need: the risk with an animal that goes for protein is overfeeding, so keep the pinch a pinch. I feed a wide variety across the whole range of foods we sell, because a varied diet is the thing I have found does most for breeding. Lift anything uneaten within a day or two, and run a springtail culture alongside from day one to keep the mould down around the protein. Our guide to feeding insects and protein to isopods covers the choices.
Breeding, and How Fast It Builds
This is a prolific isopod once it has settled, and by the standards of the tropical species it is quick. Adults reach breeding age at roughly six to eight months, broods are a good size, and a colony held inside the band builds steadily and keeps going for the two to three years these animals tend to live. Females carry their eggs in a brood pouch and release live young, the young in our photographs are plain white and the marked adults beside them suggest the pattern comes in later, and the spread of patterns in a colony is part of the pleasure of keeping it. The first weeks after arrival are quiet; leave the tub alone through them.
Start with a group. I start my own colonies at twenty or more animals where I can, because a bigger group settles faster and gives a better spread of pattern, and with a Common-rarity species that is an easy number to reach. Our guide to how many isopods to start with sets out the arithmetic. Give a new group a couple of months before you expect anything.
Is the Shiro Utsuri the Right Isopod for You?
It is rated Easy on our panel and I stand by that without the caveat I attach to the cave species. It wants warmth and a gradient, and it will forgive a missed misting, a cool week and an overfed tub in a way the cave species will not. If you have never kept an isopod it is a fair first tropical, and if you have kept a Porcellio or an Armadillidium and want to move towards the cave species without the risk, it is the obvious step. Our beginner isopods collection is where it sits.
On the black-and-white shelf it fills a particular gap. Zebra isopods give you clean stripes and drier Mediterranean care; the Panda King gives a similar contrast but with cave-species rules, and our Panda King guide sets out what those rules ask of you; Snow White goes the other way to pure pale. The Shiro Utsuri sits between: patchier markings than a Zebra, a tropical humidity profile, and none of the fuss. It also earns its keep as a cleanup crew in a humid bioactive vivarium for dart frogs, tree frogs and moisture-loving geckos, sitting happily alongside springtails; our guide to building a bioactive cleanup crew covers that job. Give it its own tub if you want to breed it cleanly; our guide to keeping different isopods together covers when mixing works.
Frequently Asked Questions
Is the Shiro Utsuri a Cubaris?
No. It was sold as one for years and the label is still in circulation, but the hobby has moved it out of Cubaris and into Nesodillo, a genus of the family Armadillidae named in 1926, and we list it as Nesodillo sp. Nobody has published an identification either way, so treat both names as labels rather than settled taxonomy. What matters in the tub is that it is not a cave animal and does not need cave conditions.
How big do Shiro Utsuri isopods get?
Around 15 to 20mm as adults on our panel, big enough to see the markings without a lens.
Do Shiro Utsuri isopods need a heat mat?
For most of the British year, yes, and always on a thermostat, fixed against the side of the tub rather than underneath. An English home measures about 19°C in the heating season and 21.5°C in July and August, and the band starts at 22°C. Below it the colony slows and does not build.
How fast do Shiro Utsuri isopods breed?
Quickly, by the standards of the tropical species. Six to eight months to breeding age, good-sized broods, and a colony that keeps producing once it is inside the band.
Can I keep Shiro Utsuri isopods in a dart frog vivarium?
Yes. They suit humid bioactive setups, they tolerate the airflow those need, and they work through waste and mould alongside springtails. Expect a frog to eat some, and keep a breeding colony in its own tub if you want to be sure of numbers.
How long do Shiro Utsuri isopods live?
Two to three years on our figures, though a colony effectively runs indefinitely once it is breeding. One care sheet says up to two years; I have not found a published measurement.
Why is it called a Shiro Utsuri?
After the koi variety of that name, a black fish with white markings. The isopod is the reverse, white with black, and the amount of black varies from animal to animal. Hobby names describe the animal; they are not taxonomy, and there is no more official name to give you.
Where to Start
The Shiro Utsuri listing carries current stock, and it sits in our other species collection alongside the animals that do not fit a genus page. Every colony we send is captive-bred here in the UK, travels in a ventilated deli tub on damp sphagnum inside a double-walled box, is dispatched Monday to Thursday so nothing sits in the post over a weekend, and comes with our live arrival guarantee and a 20% overcount.
Leave a comment