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. The colouring is broad yellow marbling laid over a dark brown base, spreading far enough on some individuals that they read as almost solid yellow, and juveniles come through more yellow-orange before the pattern settles. That marbling is the thing to check when you order, because our haasi 'High Yellow' carries discrete yellow dots on the dark base instead, small and separate, with nothing flowing about them. Different pattern, different locality, same species.

Adults reach around 30mm, which makes this the largest haasi form in the hobby and 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 roughly one fifth 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. Anything from 18 to 30°C suits them, which makes this a warm-tolerant animal, and a UK room sits inside that band without help.

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. Lifespan runs one to two years, so a group turns over faster than the larger Iberians and 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 is the bigger Iberian giant, 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.