Porcellio silvestrii 'Dalmatian' Isopods for Sale

Nobody has published the genetics of this pattern. Not for this species, not for any Porcellio. The only colour-morph inheritance study we could find in the whole group covers Armadillidium nasatum and a Porcellionides, which are different genera in different families, and its conclusions are not moving across.

That matters, because this page used to tell a genetic story. It talked about a pigment-absence mutation, named a Dalmatian gene and a piebald gene, stated that Dalmatian paired with Dalmatian produces predominantly Dalmatian offspring, and claimed this was the same genetic mechanism behind the spotting on Dairy Cow Porcellio laevis - a different species in a different part of the genus, with no published genetics of its own either. None of that is sourced. The single European seller who also lists this morph states no genetics whatsoever. We have taken the lot out.

One further deletion. This page told you males run orange and females grey, and offered it as a way to sex pairs by eye. That does not hold up: the trade disagrees about which sex carries the colour, one long-term keeper reports it in both, and another concluded it appears at random and cannot be isolated. Do not sex these by colour, here or anywhere.

What we can say is what the animals do here: the speckling is variable between individuals, cultures kept separate stay speckled, and we have never counted a brood to see what the ratios are. On how the pattern inherits, you know exactly as much as we do.

The species

Porcellio silvestrii Arcangeli, 1924. The address bar of this page spells the epithet with a single i, which is an error we have carried on all three of our pages for this animal and will fix with redirects.

Catalonia is the heart of its distribution, with Valencia and Castellón behind it and a thin scatter further inland. You may see it placed in León; that material was looked at again and turned out to be another species.

Size is genuinely unknown. Nothing is published, our own three pages for this species have carried two different figures, and the sellers who quote 25mm all quote the same unsourced number. Ours run a shade larger than the rough woodlouse in your garden, and that is as precise as we will get until somebody measures a series.

One further thing we will not do, having been caught by it elsewhere on this site. There is a well-documented Dalmatian pattern in Armadillidium nasatum that works by subtracting dark pigment and behaves as a recessive. It is tempting to reach for it here. Different genus, different family, different animal, and no basis at all for the transfer.

Conditions

Most British rooms sit inside the 18 to 24°C they want, with no help needed. Run humidity at 50 to 70%, dry-leaning, damp at one end only. No study has measured this animal, so both numbers are ours from the shelf. Airflow matters more than either: overwetting a stagnant tub kills this species faster than keeping it too dry.

Substrate 5cm is plenty - these are surface animals that want structure rather than depth. Flat stone, overlapping bark, a generous bed of leaf litter, white-rotted hardwood through the substrate, and calcium left in permanently. Protein about weekly; like most of the Spanish Porcellio they take it readily.

No rolling. Conglobation belongs to a different branch of the family tree; this animal flattens itself or bolts.

Honest positioning

It is a handsome animal, an easy one, and not rare - the same 2024 audit of the Spanish trade found this species in twenty shops at a modest price. What is uncommon is the speckled line, and how uncommon we genuinely cannot tell you, because that same survey recorded one commercial variety for the species and did not name it.

Posting runs early in the week, pre-1pm next-day. The animals sit on moist moss in a punched cup inside two-ply board, there are 20% more of them than your order says, and they are guaranteed to land alive. The other two lines are on the Porcellio page.