Pikachu Pill Millipede (Rhopalomeris sp.)

Most people who see one rolled up take it for a woodlouse. It is a millipede, one of the true pill millipedes, and when it is disturbed it closes into a complete ball with its head and every leg tucked out of sight. The trade calls this one Pikachu, a nod to its colour: a bright yellow pill millipede patterned with darker markings, small enough to sit on a fingertip once it has curled up.

The name, and what sits behind it

The full trade label is Rhopalomeris sp. 'Pikachu', and it is also traded as Pika-Pills, Pikachu pillipedes or Pika-pillipedes. Rhopalomeris is a genus of pill millipedes in the family Glomeridae, found from Myanmar and Thailand down to Malaysia, east to Vietnam and, since a 2026 record, into southern China. Thai researchers named one new species in 2025 and five more in 2026, several of them yellow-bodied and some known only from the limestone hill where they were first collected. No paper or seller I have found ties the Pikachu form to any of those named species, so it stays Rhopalomeris sp. for now. 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 rather than a long chain of rings, and it carries only 17 to 19 pairs of legs, a long way short of the hundreds on a giant; my article on how many legs a millipede has explains the difference. Unlike the flat-backed millipedes, it has eyes, a small cluster on each side of the head.

No measurement of the Pikachu form has been published. The 10 to 20mm in my care panel is one seller's figure of one to two centimetres, which fits the genus: the six species named from Thailand since 2025 run from under a centimetre to a little over two.

Care and set-up

In the wild these millipedes turn up under leaf litter, down in the soil and on the faces of limestone rocks, and one species was found buried in the soil in May and June, months its describers class as the dry season. Give them 8 to 10cm of substrate built on flake soil, organic topsoil and white-rotted hardwood, with crumbling rotten wood worked all the way through, because a pill millipede wants a very woody bed. Nearly every keeper account I have read includes moss, so lay a pad of sphagnum moss over part of the surface and keep it damp. Leave coir out: it stays wet but offers a substrate-eater no food at all.

Aim for 20 to 24°C. Indoor temperatures in English homes average about 19°C through the heating season, just under that band, so from autumn to spring warm the tub gently with a heat mat or heat cable controlled by a thermostat, mounted on one side and never beneath, where it would dry out the layer they live in. A summer room usually manages on its own. Hold the humidity at 75 to 85 per cent, keeping the bed damp but never waterlogged, and ventilate enough that the air does not go stale.

Handle them gently and briefly. A frightened pill millipede can release a sticky secretion from pores along the middle of its back. In the species analysed so far it carries two alkaloids, glomerin and homoglomerin, which have been shown to sedate a spider and to make toads vomit. I have found no study of what it does to people, so treat it as you would any millipede secretion: wash with soap when you have finished, and keep your hands away from your eyes until you have.

Diet

Rotting wood and decayed leaf litter are the diet rather than a garnish, so keep both topped up as they disappear. An occasional pinch of fish food and a sliver of soft fruit make welcome extras; lift out anything left after a day or so, because uneaten food in a damp tub is how mites get going. Make sure calcium is always available; a lump of Malawi light limestone suits an animal whose relatives live on limestone hills.

Breeding

Hobby keepers report young from several Rhopalomeris, so breeding is possible, though nothing has been published on how this form goes about it. In the best-studied pill millipede, the British Glomeris marginata, the female seals each egg inside a small capsule of soil that has passed through her gut, and the young hatch with just three pairs of legs, adding plates and legs as they moult. That is the case for leaving the substrate alone: eggs and young sit down in the bed out of sight, and digging could break open any egg capsules. Keep the wood coming and be patient.

Who the Pikachu suits

Think of it as a second or third millipede rather than a first. Mine are wild-caught, and wild-caught pill millipedes have a reputation for faring badly early on, so the first few weeks in a new tub are the real test. It suits a keeper who already runs a damp, wood-rich tub and wants something small and striking to put in it, and anyone who has enjoyed the pill woodlice, such as the Armadillidium isopods, and wants to see the millipede that rolls up the same way. The rest of my range is on the millipedes for sale page.

Each order of Pikachus is packed into an airy tub with moist sphagnum, sitting in a sturdy double-walled box, with a heat pack for company when the weather turns cold. Orders go out from Monday to Thursday, and every livestock parcel comes with my live arrival guarantee, whether Royal Mail takes it Tracked 24 or Next Day.