The Greek Shield isopod is Porcellio werneri, a woodlouse from the Cyclades islands of Greece: a broad, flat oval, slate-grey down the middle with a wide pale skirt all the way round. It cannot roll up; disturbed, it clings flat to whatever it is standing on. Keep it at 17 to 26°C and 50 to 65% humidity, the figures on my care panel, in a well-ventilated tub kept damp at one end and dry across the rest, with flat bark to press under, leaf litter and rotten hardwood to eat, and calcium always in the tub. My Greek Shield isopods are captive-bred.
What the Greek Shield Isopod Is
Hans Strouhal, a Vienna zoologist who wrote widely on Balkan woodlice, described Porcellio werneri in 1929, and the World Register of Marine Species and GBIF both list it as an accepted species. Helmut Schmalfuss's world catalogue of land isopods gives its range as three islands in the middle of the Aegean: Naxos, Paros and Amorgos, all in the Cyclades. The one record on GBIF is a photograph taken on Serifos, in the western Cyclades, in August 2022. I could not read Strouhal's original description, so I cannot give its type locality or what it says of size or habitat.
The name probably honours Franz Werner (1867 to 1939), another Vienna zoologist, who made at least four collecting trips to the Aegean; Strouhal later wrote up the woodlice Werner brought back from Greece, but without the 1929 text I cannot confirm it. Armadillidium werneri, a Corfu pill woodlouse that Strouhal named in 1927, is a different animal. 'Greek Shield' is a trade name, and I have found no record of who coined it.
One care guide quotes a 2009 study of the woodlice of 90 Aegean islands, by Sfenthourakis and Triantis, as placing it among "specialists that are restricted to dry habitats, like calcareous rocky substrate". I could not open the study to check the wording, and I have found nothing else on its habitat. It is not one of the big, flat Spanish Porcellio it is often compared with, and a Dutch breeder notes that it does not need the extremely dry set-up those are kept in.
What It Looks Like and How Big It Gets
Seen from above it is a wide oval, with the side plates of every segment spread out into a flat skirt. In the photos on this page the back runs from lilac-grey through slate-blue to almost black, finely granular, and the skirt shades out to pale grey or nearly white. The Dutch breeder describes it as "dark gray, almost black with a white skirt", and another seller as dark with bright white "feathering" around the edge.
My care panel gives 20 to 25mm, as body length without the antennae and tail appendages, the convention on all my panels. The Dutch breeder gives adults up to 20mm, and one care guide about an inch at most. I have found no published measurement.
There is also a line sold as the Silverback, with a pale, cream-to-silver band down the middle of the back between darker flanks. The Dutch breeder that sells it calls it a cultured morph and gives it the same care figures, and I have found no published account of where it came from. My Silverback Greek Shield listing is out of stock.
Setting Up the Tub
A clip-lid plastic tub works well. A starter group settles in a 3-litre tub and 4 to 10 litres gives more room, but floor area matters more than height: this is a broad animal, and the Dutch breeder and a care guide both say males can be territorial. My own standard is an 11-litre tub, 17 litres or more for the larger species; my guide to how big a tub isopods need goes through sizes as a colony grows.
The three sellers and keepers I found who give a split keep a quarter to a third of the tub damp and the rest dry, and all three keep it well ventilated. Lay about 5cm of organic topsoil, flake soil and shredded rotten wood and moisten one end only. Coco coir holds moisture but gives a substrate-eater nothing to eat, so I leave it out. Cover the surface with dry hardwood leaves and add plenty of flat cover: slabs of cork bark, flat bark or slate give it surfaces to press under, and a piece laid across the gradient lets it choose damp or dry underneath. A pad of moss at the damp end holds water between mistings.
Temperature and Humidity
My care panel gives 17 to 26°C, the same band as the Dutch breeder. One keeper writing first-hand keeps them at about 24 to 27°C. An English home averages about 19°C over the heating season, about 18°C in December and about 21.5°C in July and August, so a heated room keeps the tub inside the band for most of the year with no heat mat. 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; I run heat cable along the back of my racking. Keep it out of direct sun, and somewhere cooler in a heatwave.
For humidity the panel says 50 to 65%, again the Dutch breeder's figure; a keeper on an invertebrate forum calls it a species for "pretty arid" enclosures. The panel covers the whole tub, the lower figure roughly the dry end and the higher the damp end; my guide to humidity for isopods explains the gradient. Mist only the damp end. If the colony crowds into the damp end day after day, give it more moisture or cover; if the substrate turns to mud or smells sour, the tub is too wet or the air too still.
Feeding
It is a detritivore, so leaf litter and rotting hardwood should always be in the tub; they are most of what it eats. On top of that, give a little fresh food twice a week, such as a slice of courgette, carrot or sweet potato, and protein once or twice a week, such as a pinch of fish flakes or dried shrimp. One breeder gives protein twice a week, and another seller recommends a higher-protein diet for it. Clear leftovers before they mould, putting fresh food on the damp side and lifting it within a day or so. Keep a calcium source in the tub at all times, a piece of cuttlebone or Malawi limestone.
Breeding
Two sellers, a care guide and a forum keeper call it, or think it, a seasonal breeder, and the last two put it at a brood or two a year; the Dutch breeder rates its breeding moderate and allows 8 to 12 months to establish a stable colony of its Silverback line. I have found no published brood size, age at maturity or lifespan for it. Most woodlice need both sexes to breed; the female carries her eggs in a fluid-filled pouch under her body, and the young leave it alive, pale and still short of their last pair of legs. Most woodlice live about two years, and some three or four; the common pill woodlouse, Armadillidium vulgare, can live up to about five.
I start colonies with twenty or more animals where I can, because a bigger group settles in and builds faster than a handful. Keep the standard and the Silverback in separate tubs, hold the gradient and the airflow steady, and give a new group several months before you judge it.
Behaviour and Handling
One breeder describes it as active at night and in the early morning, and a care guide calls it shy, so expect to find it under the bark. Like other Porcellio, it cannot roll into a ball as a pill woodlouse does. Instead, "When disturbed, they tend to strongly cling against the substrate for defence", as one keeper on an invertebrate forum puts it, and the care guide describes them pressed flat against cork bark. It cannot bite you and has no venom, so it is safe to handle, but do not try to prise a clinging animal off a surface; lift the bark it is on, or let it walk onto a flat hand.
Is It a Good First Isopod?
My care panel rates it medium, and the Dutch breeder moderate, though it calls the species "a non demanding species to keep and breed" once a colony is established. One care guide's author thinks its reputation for being difficult is largely unfounded now. What it asks for is a mostly dry tub with air moving through, which runs against much beginner advice, and patience with a seasonal breeder. It suits a keeper who has already kept a Porcellio or a Mediterranean pill woodlouse, and it is a good step towards the big Spanish species in my giant Spanish Porcellio care guide, which want it drier still. For a very first isopod, start with one my care panels rate easier, such as the Dairy Cow, another Porcellio.
Frequently Asked Questions
What is a Greek Shield isopod?
It is Porcellio werneri, a woodlouse that Hans Strouhal described in 1929, known from the Cyclades islands of Greece. It is broad, flat and slate-grey with a pale skirt, and clings flat when disturbed instead of rolling up.
Where do Greek Shield isopods come from?
The world catalogue of land isopods gives Naxos, Paros and Amorgos, three islands in the central Aegean, and a 2022 photograph may add Serifos. Mine are captive-bred.
How big do Greek Shield isopods get?
About 20 to 25mm, the figure on my care panel. A Dutch breeder gives up to 20mm and a care guide about an inch at most; I have found no published measurement.
Do Greek Shield isopods need a heat mat?
Not in a heated room for most of the year. My care panel gives 17 to 26°C, and an English home averages about 19°C over the heating season. If the room drops below 17°C, add a heat mat or heat cable on a thermostat, on the side of the tub and never underneath.
How fast do Porcellio werneri breed?
Not quickly. Sellers and keepers describe a seasonal breeder, two of them with a brood or two a year, and one breeder allows 8 to 12 months for a Silverback colony to establish, so start with a good-sized group and give it time.
Are Greek Shield isopods good for beginners?
They make a better second species than a first. My care panel rates them medium; the care is not hard, but the mostly dry, well-ventilated tub runs against much beginner advice, and colonies build slowly.
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