Greek Shield Isopod (Porcellio werneri)

On the dry limestone of the Aegean islands there is not much cover and even less water, and the animals that make a living there tend to be specialists. Porcellio werneri is one of them: an isopod adapted to rocky, calcareous, sun-baked ground, spending the day pressed into a crack in the stone and coming out at night to feed. Ecological surveys of those islands list it among the species restricted to dry habitats, and that single line of habitat description is worth more than any care sheet, because almost everything that goes wrong with this species in captivity comes from ignoring it.

What that environment produced is the flattest woodlouse in the hobby. A wide grey disc with a pale serrated skirt running the full circumference, low enough to look pressed, and unlike anything else you will put in an enclosure.

Names

Sold as the Greek Shield Isopod, Werner's Woodlouse, or the Pancake Isopod, and listed scientifically as Porcellio werneri. Adults run around 20 to 25 mm across, which places them among the larger isopods available in the UK. Juveniles arrive brown and shift to the adult grey as they mature, so a mixed-age group will look less uniform than a photograph of adults suggests.

One thing to correct, since it turns up on a number of listings: this is not a Spanish species. That confusion comes from the several dry-climate Porcellio that do come from Iberia. Werneri is Greek, and while it wants a drier setup than most isopods, it is noticeably less extreme in that regard than its Spanish cousins.

Standard or Silverback?

We stock two lines and it is worth knowing the difference before you choose. This page is the standard form: uniform grey across the back with the pale skirt. The Silverback comes from a separate wild population and carries a broad silvery-white band down the centre of the body.

Care is identical between the two, so the decision is purely about looks and cost. The standard grey is the more affordable way into the species and, to my eye, the cleaner shape; the Silverback is the collector's version. Both do the same thing in an enclosure and neither is harder to keep than the other.

Why it is shaped like that

Most people assume the flatness is decorative. It is defensive. A Porcellio cannot conglobate the way an Armadillidium can, so where a pill bug rolls into a sealed ball, werneri does the opposite and presses itself down. Threatened, it clamps flat against whatever it is standing on or reverses into a crevice, and at that point there is very little for a predator to get purchase on.

In an enclosure you will see the behaviour constantly against cork bark, where they flatten so completely they seem to be part of the surface. It is the single most entertaining thing about keeping them, and it is why the enclosure needs crevices rather than open floor.

The setup

Roughly a third damp, two thirds dry, and generous ventilation throughout. That ratio is the whole game with this species. A sealed humid tub will finish a colony, and it does so quickly enough that people usually assume the animals were unwell on arrival rather than recognising the cause.

Lay 5 to 7 cm of a nutritious base such as our invertebrate substrate, moisten one end only, and cover the surface with dry hardwood leaf litter. Magnolia leaves hold their structure well and give them something to work under. Stack flat bark, slate or stones, because an animal built for crevices needs crevices to use, and give them floor area rather than height, since adult males can be territorial and a cramped tub produces more conflict than a roomy one. There is more on getting the base right in my isopod substrate guide.

Ordinary UK room temperature suits them from the high teens to the mid twenties, with no heating required.

Protein and calcium

Leaf litter and rotting hardwood form the base of the diet, but Porcellio as a genus is protein-hungry and werneri is no exception. Offer dried shrimp, fish flake or similar at least weekly. This is the same trait that makes the Dairy Cow a risk to soft-bodied tankmates when underfed, and while werneri is less notorious for it, the principle holds: a hungry Porcellio goes looking.

Calcium is the other requirement, and a large heavily armoured species gets through it. Keep cuttlebone available permanently. In a deliberately dry enclosure, clear uneaten wet food within the day so it does not create the damp patch you have been careful to design out.

Behaviour and breeding

Reliable rather than fast. With the gradient and airflow right they reproduce steadily; with either wrong the colony quietly stalls, without any obvious sign that something has gone amiss. Give a new group a couple of months before judging progress.

They are active at night and in the early morning and spend daylight hours under cover, so this is not a species that performs on demand. The pleasure is in lifting a slab and finding half a dozen of them fused to the underside.

Who they suit

An intermediate species. Not fragile, but the drier discipline runs directly counter to what most beginner guides teach, and that is what catches people out. Anyone who has kept a Mediterranean species already has the instincts for it.

See the rest of the genus in the Porcellio collection, or the full range in isopods for sale.

Arriving with you

Captive-bred in the UK. Orders leave Monday to Thursday only so nothing sits in the network over a weekend, travelling Royal Mail next day by 1pm in a double-walled box, with the animals in ventilated deli tubs on damp sphagnum moss. A 20% overcount and our live arrival guarantee come as standard. Build the enclosure before they arrive, and when you look at it and think it seems too dry, that is roughly correct.