Greek Shield Isopod (Porcellio werneri)

The world catalogue of land isopods gives the range of Porcellio werneri as three islands of the Cyclades, in the Aegean: Naxos, Paros and Amorgos. One care guide quotes a 2009 study of Aegean woodlice as placing it among the specialists of dry, rocky ground, though we have not been able to read the study itself. Either way, it does best kept mostly dry with air moving through, and the dry end of the tub matters more with this species than with most.

It is a strikingly flat woodlouse: 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, and listed scientifically as Porcellio werneri, the name Hans Strouhal gave it in 1929. Adults run around 20 to 25 mm long, 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 is a separate line with 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. Hold that ratio, and keep the air moving through the vents: this is not a species for a sealed, humid tub.

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 the isopod substrate guide.

Our care panel gives 17 to 26°C. An English home averages about 19°C over the heating season, so a heated room keeps them inside that band for most of the year; a room that drops below 17°C wants a heat mat or heat cable on a thermostat, fixed to the side of the tub and never underneath. The Greek Shield care guide covers the set-up, temperature and breeding in more detail.

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 once or twice a week. 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.

Alongside the protein, keep cuttlebone available permanently: woodlice build a calcium carbonate cuticle. 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 several 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 by Royal Mail Tracked 24, or Special Delivery Guaranteed by 1pm if you choose Next Day at checkout, 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.