Porcellio haasi 'Bardenas' Isopods

The Bardenas Reales sits in the southeast corner of Navarre and looks like nowhere else in Spain. Clay, chalk and sandstone have been eroded into canyons, flat-topped plateaus and isolated hills standing alone on open ground, with gypsum running through the soil and streambeds that stay dry for most of the year. Vegetation is sparse, and shade is whatever a rock or a dead stem gives you. Every odd thing about keeping this isopod comes straight out of that description, which makes the habitat the care sheet.

The animal is Porcellio haasi Arcangeli, 1925, and 'Bardenas' is a locality line taken from that landscape rather than a selected colour morph. In our photographs the colouring is pale yellow over most of the back, marbled with light brown, with a white skirt and white legs. That marbling is the thing to check when you order, because our haasi 'High Yellow' carries discrete bright yellow spots on a dark back instead, with nothing flowing about them. Different pattern, different locality, same species. Our Porcellio haasi care guide sets the two lines side by side.

Keepers put adults at around 30mm, the figure in our care panel, against about 20mm for the High Yellow, which gives a mature colony real presence. It does not conglobate. No Porcellio does. Startle it and it scurries, then clamps flat under the nearest piece of bark. They are night-active and social, so most movement happens once the room goes dark, and a colony under a lifted flat of cork is usually piled up together in one spot.

The dry side is the whole job

Humidity belongs at 45 to 55 per cent, drier than almost anything else in the hobby, and the way to reach it is to damp a fifth to a quarter of the enclosure and leave everything else dry. Strong airflow keeps it that way, so ventilation has to be substantial rather than adequate. This is not a preference that can be softened. It is the actual requirement, and what undoes it is a keeper deciding, kindly, to mist the whole box. Temperature is the easy part. They do best at 18 to 26°C, and a UK room sits inside that band for most of the year; some keepers report them tolerating up to 30°C and others cap the range lower, so treat 26°C as the working ceiling.

Give the substrate 5 to 8cm with a clear moisture gradient built into it, damp at one end and dry through the rest, so the colony picks its own position. Hardwood leaf litter goes on top, where it works as food quite as much as it works as cover. Bark wants to be plentiful, laid flat and stacked in layers, because that is where they spend daylight. Calcium has to be high and permanent to carry moults on an animal this size, so cuttlebone or crushed limestone stays in and gets topped up. Protein comes round on a regular cycle, dried shrimp or fish flake, put down on the dry side where it will not spoil.

Breeding is where expectations need setting. They are prolific, but seasonally rather than steadily, so a colony can sit unchanged for a stretch and then produce a wave of young all at once. Keepers give lifespans of one to two years and of two to three, so a group depends on those bursts landing. Difficulty is moderate, well within reach of anyone who has run a colony before, but this is not a first isopod. If you are building a Spanish shelf around it, the Titan brings the grey-and-white Iberian look, Bolivari 'Lemonade' is another yellow Spaniard at size, Ornatus 'High Yellow' and the orange expansus fill out the colour, our Porcellio guide compares the genus, and the wider Porcellio range holds everything else.

What turns up is a deli tub with vents, sphagnum damp under the colony, and a double-walled box around the lot. Next-day Royal Mail, tracked, in before 1pm, dispatched Monday to Thursday and never on a Friday, so the box is not in the system across a weekend. The tub goes out holding a few beyond the count ordered, and our live-arrival guarantee stands behind it.