A pill millipede is a millipede that rolls into a ball, so most people who find one take it for a woodlouse. The one I sell, the Pikachu Pill Millipede (Rhopalomeris sp. 'Pikachu'), is small, yellow and cream with black spots and orange-red patches, and closes into a complete ball when disturbed, head and legs tucked out of sight. Keeping one comes down to a damp, very woody bed: rotting wood and decayed leaves as the food, moss over part of the surface and calcium always in reach, at 20 to 24°C for the Pikachu, which in most homes means gentle heat through the colder months.
Pill millipede or pill woodlouse?
A pill woodlouse, the pill bug or roly-poly of gardens, is a crustacean, related to crabs and shrimps, with seven pairs of legs; my guide to what isopods are covers that side of the family tree. A pill millipede is a myriapod, in the same broad group as centipedes, and in the Pikachu's order a female has 17 pairs of legs and a male 19, the male's rearmost pairs modified for mating. To tell them apart, count the legs or look at the tail: a pill millipede ends in one broad, undivided plate, a pill woodlouse in a set of small, narrow ones. My article on how many legs a millipede has compares the other groups.
The name also covers the giant pill millipedes, a separate order (Sphaerotheriida) of larger animals from southern Africa, Madagascar, South and Southeast Asia and Australasia, with 21 pairs of legs in a female and 23 in a male; this guide covers the smaller order, Glomerida, where the Pikachu belongs.
Rhopalomeris and the Pikachu name
Rhopalomeris Verhoeff, 1906 is a genus of pill millipedes in the family Glomeridae, found from Myanmar and Thailand to Malaysia and Vietnam, and in 2026 it was formally recorded from China for the first time, in Guangdong. At least eight new species were named in 2025 and 2026, six of them from Thailand. Those Thai species are mostly yellowish with dark spots. Four are so far known only from the site where they were collected, three of them on or beside a limestone hill or mountain, and another was found buried in the soil in May and June, months its describers class as the dry season.
I have found no paper or seller that ties the Pikachu to any named species, so it stays Rhopalomeris sp., and Pikachu is a trade name, a nod to its colour. The stock is sold as Thai, with no collecting locality given.
Appearance and size
Like the other pill millipedes of its order it is short and domed, built from about a dozen broad plates: a small collar behind the head, a large shield, a run of smaller plates and a broad tail plate. Unlike the flat-backed millipedes, it has eyes: the Rhopalomeris species descriptions count a small cluster on each side of the head.
I have found no published measurement of the Pikachu form. The 10 to 20mm in my care panel is one seller's figure of one to two centimetres, which fits the genus: the six Thai species named since 2025 run from under a centimetre to a little over two, and in each description the biggest animal measured is a female.
Setting up a pill millipede tub
In the wild these millipedes live under leaf litter, in the soil and on or beside limestone rocks, and a tub should offer the same layers. Give them 8 to 10cm of bedding built on flake soil, organic topsoil and white-rotted hardwood, with plenty of crumbling rotten wood worked through it. Keepers list moss, live or dead, among the foods for pill millipedes, so lay a pad of live sphagnum moss over part of the surface. Skip coir: it holds moisture but has no food value for a substrate-eater.
Aim for 20 to 24°C. English homes average about 19°C through the heating season, so from autumn to spring use a heat mat or heat cable on a thermostat, on the side of the tub, never underneath, where it would dry the bed out. A warm summer room may need little help, and in a heatwave the job reverses: switch the heat off and move the tub somewhere cooler.
Hold the humidity around 75 to 85 per cent through the bedding rather than by misting: keep it damp enough that a squeezed handful holds together without dripping, and give the moss a light spray now and then. A tub around 30cm long suits a small group, with air space above the bedding and enough ventilation to keep it fresh.
What to feed
Decayed material is the bulk of the diet: well-rotted leaf litter and soft, white-rotted wood, topped up as they disappear. The native British Glomeris marginata is recorded feeding on old, decaying leaves, and my article on fresh and well-rotted leaf litter explains what decay does to a leaf. Extras are optional and occasional: a slice of cucumber, a sliver of soft fruit or a pinch of fish food. Lift out anything left after a day or so, because uneaten food in a damp tub is how mites get going.
Keep calcium in the tub at all times, such as limestone or cuttlebone. The British Myriapod and Isopod Group notes that Glomeris marginata is most typical of woodland on lime-rich soils, and that in Flanders soil calcium was the strongest factor in how many there were; several Rhopalomeris were collected on limestone hills.
Breeding and lifespan
Keepers report young from Rhopalomeris, often quite quickly, though I have found nothing published on how the Pikachu breeds. In Glomeris marginata the female seals each egg in a small capsule of soil that has passed through her gut and leaves them, and the young hatch with just three pairs of legs, adding plates and legs as they moult. Rhopalomeris may differ: in 2024, scientists describing a species from Myanmar reported a female and two males found guarding eggs beneath the shield behind the head, which they call the first paternal brood care seen in the order. Eggs and young are easily missed, and digging can break egg capsules or disturb a guarding adult, so leave the substrate alone and keep the wood coming.
I have found no lifespan figure for any Rhopalomeris, and I cannot tell the age of a wild-caught animal on arrival, so the ten to eleven years recorded for Glomeris marginata is a sense of scale, not a promise.
Handling and the defensive secretion
Handle them gently and briefly, over the tub. A frightened pill millipede can release a sticky secretion from pores along the middle of its back, where most millipedes' glands open along the sides. In Glomeris marginata it carries two alkaloids, glomerin and homoglomerin, which in tests sedated wolf spiders and made toads vomit. A 2024 paper on the chemistry reports one or both in every species of the order analysed so far, and every species on its list is European or North American; I have found no analysis of an Asian species, and no study of what the secretion does to people.
Treat it as you would any millipede secretion: wash your hands with soap afterwards, keep them away from your eyes until you have, and if any gets into an eye, rinse it with plenty of water and get it looked at promptly. Children can hold one with supervision, and the supervision is about hand-washing and keeping fingers away from eyes.
Who the Pikachu suits
Think of it as a second or third millipede rather than a first. One keeper rates this order trickier to breed than most long-bodied millipedes and isopods, and for a first millipede my guide to the best beginner millipedes is the place to start. Mine are wild-caught, and wild-caught pill millipedes have a reputation for faring badly early on, though the keeper accounts I have read mostly concern the giant pills, blaming starvation or heat on the journey. The first few weeks in a settled tub are the real test. It suits a keeper who already runs a damp, wood-rich tub, or anyone who has kept pill woodlice and wants the millipede that rolls up the same way. The rest of my range is on the millipedes for sale page.
Frequently Asked Questions
Can you keep pill millipedes as pets?
Yes. Smaller pill millipedes such as the Pikachu can be kept in a tub at home, though they suit a keeper with an easier millipede or two behind them. They cannot bite or sting, but they are for watching more than handling, and you should wash your hands with soap after touching one.
How do you care for a pill millipede?
Give them a ventilated tub with 8 to 10cm of damp, very woody bedding, moss over part of the surface and calcium always available, and feed rotting wood and well-rotted leaf litter. Keep the Pikachu at 20 to 24°C, using a heat mat or heat cable on a thermostat, on the side of the tub, never underneath, through the colder months.
What do pill millipedes eat?
Pill millipedes eat decaying plant material, mostly well-rotted leaf litter and soft white-rotted wood, and keepers add moss. Cucumber, soft fruit or a pinch of fish food can be offered occasionally, and a calcium source should always be in the tub.
How long do pill millipedes live?
Up to ten or eleven years in Glomeris marginata, a native British species, according to the British Myriapod and Isopod Group, with males maturing in their second or third year and females in their third or fourth. I have found no lifespan figure for any Rhopalomeris, the Pikachu included.
What is the difference between a pill millipede and a pill bug?
A pill bug is a woodlouse, a crustacean with seven pairs of legs; a pill millipede is a millipede, and the British kind, from the same order as the Pikachu, has 17 pairs of legs if female and 19 if male. Both roll into a ball, but they evolved the habit separately. Count the legs, or look at the tail: one broad plate on a pill millipede, several small ones on a pill bug.
Are pill millipedes found in the UK?
Yes. Britain has native pill millipedes, among them Glomeris marginata, which is usually black or dark brown and up to 20mm long and lives in leaf litter and under stones, most often in deciduous woodland on lime-rich soils. My UK millipede identification guide covers the native species.
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