Armadillidium granulatum Isopods (Yellow Spanish)

Every eye-catching granulatum morph in the hobby, the pearl-white, the citrus-washed, the vivid orange Naranjito, traces back to this animal: the standard Armadillidium granulatum, the Yellow Spanish Isopod. It is the foundation the selective work is built on, and it is a handsome, characterful woodlouse in its own right, so there is a good case for keeping the original rather than only its offshoots. The look is a dark grey-to-black body scattered with bright yellow spots, all of it carried on a distinctly granulated, faintly bumpy shell that gives the species both its name and its texture.

It is a coastal pill woodlouse of Mediterranean and Atlantic shores, from Portugal and France to Turkey and North Africa, living under stones near the shore, from cliff bases to the edges of saltpans, and like most Mediterranean isopods it takes UK room conditions in its stride. It is also one of the larger Armadillidium going. In 1885 Budde-Lund measured adults at 16 to 17 mm, the largest at 19 mm, which gives a settled colony real presence. The yellow spotting varies a lot from one animal to the next, from sparse pale flecks to dense bright patterning, which is exactly the raw material keepers have selected into the various Orange, White Pearl and Citrus Ghost lines. Start with the standard and you have both a fine display colony and a base to breed from.

The care is simple and forgiving, which makes granulatum a sensible step up from the most basic beginner species. It shelters under stones on hot, summer-dry coasts, so it wants a moisture gradient rather than a wet box: aim for something around 50 to 80% across the tub, one lightly damp corner under sphagnum and leaf litter and the rest left to breathe and dry between mistings, with good cross-ventilation over the top. It does best between 18 and 22°C, a band a normal UK room holds the year round, and it will sit out anything from 15 to 26°C without complaint. Like most true pill woodlice it conglobates, rolling into a tight sealed ball when startled.

Set a starter colony up in a five to ten litre tub with a clip-lock lid and cross-vented sides. For substrate I use a living base of flake soil, well-rotted hardwood and organic topsoil, five centimetres or so deep for burrowing. A plain coco-coir base is best kept out of it, holding damp while feeding a substrate-grazer nothing as it breaks down. Cap it with a thick layer of hardwood leaf litter, magnolia and oak both good, add cork bark for cover, and leave a calcium source such as cuttlebone or crushed eggshell in permanently for firm, clean moults.

Feeding is no trouble. Leaf litter and rotting wood are the always-available staple; on top of that offer soft veg like courgette, squash and sweet potato a couple of times a week, lift out anything uneaten within a day, and give a little protein such as fish flake or dried insects now and then to keep a breeding colony productive. As with all Armadillidium they will graze soft plants and moss in a planted setup, so choose tougher greenery if you want it to last.

Our Armadillidium granulatum care guide goes into the enclosure, humidity gradient, feeding and breeding in more detail.

Breeding is reliable once the gradient is right, the female carrying young in a brood pouch and releasing live miniatures that pick up their spotting as they mature. A group given warmth, calcium and steady food builds into a self-sustaining colony over a season. Browse the wider Armadillidium collection to see where it sits, or compare it with the speckled Magic Potion. Every order is captive-bred, boxed double-walled around a ventilated tub of damp sphagnum, and posted Monday to Thursday by Royal Mail, Next Day or Tracked 24, with a live-arrival guarantee and a 20% overcount as standard.