Armadillidium scaberrimum 'Sandstone' Isopods

For years this animal moved through the hobby under the wrong name. Stock now sold as the Sandstone Isopod was traded as Armadillidium omblae, and it was never that species. The distinction is worth getting right, because this was not a renaming. Armadillidium omblae has not gone anywhere. It is a valid species with its own description, a different animal entirely, and it still carries that name today. What happened is that hobby stock was misidentified. Most sellers now use the right name, though we could find no published account of who re-identified the stock or when. The animal on this page is Armadillidium scaberrimum, described by Stein in 1859.

The trade name suits it on both counts. The back is densely covered in fine granules that catch the light and break up its outline, and the colour runs from cream to a peachy tan, some animals with a cool lilac-grey cast and a few with bluish patches on the back. Stein measured his animals at 15mm when he described the species, and Budde-Lund gave 14mm for one Stein sent him. This page used to say about 20mm, as other listings do, and we have found no published measurement that supports it.

Underneath the shell this is an uncomplicated pill woodlouse from the Dalmatian coast of Croatia and from Kotor, just over the border in Montenegro, and easy to keep provided most of the tub stays dry. Sellers describe it rolling into a ball when disturbed, though neither Stein nor Budde-Lund says whether it closes completely. Keepers report it active by day as well as at night, so a settled group is one you actually see rather than one you keep on trust.

Warm room, dry floor

We have found nothing published on how this species lives, so these are keepers' figures. Temperature is the uncomplicated part. Anywhere from 17 to 26°C suits it. An English home averages about 19°C over the heating season and about 21.5°C in July and August, so a heated room keeps the tub inside that band for most of the year with no heat mat; a room that drops below 17°C in winter wants one on a thermostat, fixed to the side of the tub and never underneath. Humidity is where keepers can go wrong. Aim for 50 to 65 per cent, drier than most people expect from a pill woodlouse, and arrange it as a slope from damp to dry, never one flat reading. In practice we keep about a fifth of the floor area damp and let the remaining four fifths run dry. Medium ventilation goes with that, enough airflow that moisture leaves the enclosure instead of hanging in it.

Substrate and feeding

A nutritious base substrate 5 to 8cm deep is all this species needs. Cover it with a generous layer of dry hardwood leaf litter, which gives the colony shelter and something to graze at for weeks on end, and add bark for the group to gather under. There is always cuttlebone or crushed shell in my tubs, because woodlice build a calcium carbonate cuticle. Vegetables go down readily, as does an occasional protein source.

Undemanding, robust and hard to upset, this is a sensible pill woodlouse for anyone stepping past their first species. It is prolific, though not in the way people picture: it produces large broods at intervals rather than a steady trickle of young, so numbers can sit still for weeks and then jump. Adults last two to three years. If the Adriatic angle appeals, the Clown comes off the same stretch of Croatian coast and is the bold-patterned opposite of this one, with Skeleton-Nebula a second line of that same species. For more texture, we also keep the spiny Beier's Pill Woodlouse, and Armadillidium granulatum is the pebbled Spaniard. Our Sandstone isopod care guide goes further into the name, the size and the setup, our Armadillidium care guide covers the genus, and the wider Armadillidium range shows what else sits on that shelf.

Sandstone go out over damp sphagnum, the deli tub vented, the outer box carrying two walls of card. Posting days run Monday to Thursday with nothing after that, by Royal Mail Tracked 24, or Special Delivery Guaranteed by 1pm if you choose Next Day at checkout, so no group of ours spends a Saturday in a sorting office. Counts include spares beyond what you asked for, and the live-arrival guarantee applies as always.