Types of Powder Isopods: Every Porcellionides pruinosus Morph

Every Powder isopod sold in the UK is the same animal. Powder Orange, Powder Blue, Powder White, the Dalmatian, the Oreo Crumble, the plain grey Wild Type: all of them are Porcellionides pruinosus, and the differences between them are colour lines within one species rather than separate species that happen to look alike.

That single fact decides almost everything about how you buy and keep them, and it is the thing most new keepers find out a generation too late. This guide runs through the morphs, explains where the frosted look actually comes from, and covers the one decision that matters more than which colour you pick.

The bloom is not wax, and it is not pigment

The species name comes from the Latin pruinosus, meaning covered in hoarfrost, and that is exactly what the surface looks like: a fine pale dusting sitting over whatever colour lies underneath.

The hobby almost universally calls this a waxy bloom. It is not wax. The only study to have analysed it, by Vittori and Gantar in 2020, reports something else entirely: a surface studded with microscopic spheres built from protein, with glycoprotein or polysaccharide alongside, and lipid absent from the analysis. Those spheres go on during the premoult stage, onto the shell that has not been revealed yet, and a surface wearing them sheds water measurably better than one that has had them removed.

So the finish is structural rather than pigment. That explains why an orange animal, a blue-grey one and a plain wild grey can all wear the identical frosting, and why calling a Powder White an albino gets the mechanism backwards. And because the layer is rebuilt at every moult, a freshly moulted Powder can look patchy or dull for a day or two before the finish comes back. That is normal and needs no intervention. Our guide to which white isopod is which goes further into the difference between a structural white and a pigment-loss white.

The morphs

Wild Type is the original: a plain grey animal, restless, out in the open far more than most isopods, and the stock every other line came out of. It tends to run at the larger end of the species and it is the cheapest way to get a working colony going. If you want the behaviour rather than the colour, start here.

Powder Orange is the one that made the species famous. A soft warm orange under the frosting, fast to establish, and the single most recommended first isopod in the UK hobby. If someone tells you to get Powders, this is usually what they mean.

Powder Blue wears a dusty blue-grey you will not find elsewhere in a collection of browns and oranges, and it can turn faintly metallic in the run-up to a moult. Same speed, same tolerance, same appetite as the Orange.

Powder White is where the bloom is easiest to see, because there is very little base colour beneath it. A ghostly white to pale grey animal that reads as frost on cold glass. Worth saying plainly: this is not an albino line, and it is a different thing from a Dwarf White, which is a separate species entirely.

Powder Orange Dalmatian puts scattered black spotting over the warm orange body. Dalmatian patterning usually turns up on a pale base, so orange dappled with dark flecks is an unusual combination and it holds its interest longer than a flat colour does.

Oreo Crumble is the black-and-white line, and it is the one most often bought by mistake. See below.

Rainbow Mix is not a morph. It is a deliberately mixed culture holding several of the lines above in one tub, sold as the least fussy way in. You get variety and a fast, cheap colony, and you give up the ability to keep any line pure.

The decision that actually matters

They all interbreed, freely and immediately, because they are one species. Two morphs in one enclosure will not stay two morphs.

The offspring are not a blend in any tidy sense either. Colour in this species behaves as a set of lines maintained by selection rather than a simple dominant and recessive pair, so a mixed colony drifts towards muddier intermediate animals over a few generations and the crisp orange or clean blue you paid for stops appearing. Nothing is wrong with the colony when this happens. It is simply what happens when selection stops.

So the choice is genuinely binary. Either run one morph per enclosure and keep it pure, in which case separate tubs are not optional and neither is checking what goes back into which box. Or run a Rainbow Mix deliberately, enjoy the variety, and accept that you are keeping a mixed colony rather than a colour line. Both are reasonable. The mistake is buying two pure morphs, putting them together to save a tub, and being disappointed in eight months.

Oreo Crumble is not a Dairy Cow

The mix-up is understandable, since both animals are monochrome and both get bought for the same jobs, but they sit in different genera. Dairy Cows are Porcellio laevis: bigger, flatter, more deliberate, and hungrier. An Oreo Crumble is a Powder, which means small, quick, and gone the moment you lift the bark.

For a cleanup crew under a fast-moving animal the Powder is usually the better pick. For a display colony where you want to actually see the isopods, the Dairy Cow is easier to watch.

Which one should you start with

Starting out, or seeding a bioactive enclosure? Powder Orange or the Rainbow Mix. Both settle fast, put up with a broad spread of conditions, and shrug off the errors every keeper makes early on.

For a display line you intend to keep pure, pick the single colour you like most and give it its own enclosure from day one. For a feeder culture or a genuinely low-cost start, Wild Type does everything the coloured lines do at a lower price.

Adults reach somewhere around 10 to 15mm depending on the line and the conditions, with the Wild Type usually the biggest. All of them want the same setup, which is drier and better ventilated than most people expect from an isopod. The full husbandry is in our Powder isopod care guide, and the whole range is in the Porcellionides collection.

Frequently asked questions

Is a Powder Blue the same animal as a Powder Orange?

Yes. Both are Porcellionides pruinosus, as are Powder White, the Dalmatian, the Oreo Crumble and the Wild Type. They are colour lines within one species, which is why they interbreed.

Can I keep two Powder morphs together?

You can, and they will do fine, but you will not have two morphs for long. Expect intermediate animals within a few generations. Keep one line per enclosure if you want the colour to stay.

Why does my Powder isopod look dull or patchy?

It has probably just moulted. The frosted layer is rebuilt at each moult rather than carried through it, so a freshly moulted animal takes a day or two to look right again.

Is the powdery coating wax?

No, although nearly every source says so. It is a layer of protein-based spheres on the surface of the shell, with no detectable lipid. It repels water and it is structural rather than pigment.

Are Powder Whites albino?

No. The white comes from the surface bloom over a very pale base, not from an absence of pigment, and their eyes are normally coloured. A true pigment-loss white is a different thing.