Most peraccae setups fail in the same way, and it is not the humidity. It is that people build a deep, beautiful substrate for an animal that spends almost no time in it. This is a bark dweller. Get that right and the rest is undemanding.
The short version
Keep Armadillidium peraccae at 60 to 75 per cent humidity, built as a gradient across the tub. Hold it at 18 to 24°C, which most British rooms manage without help. Give it far more cork than you think it needs, stacked so the animals can pack in between the layers. Feed rotted hardwood and leaves as the base, protein a couple of times a week, calcium down permanently.
It is not a difficult species. It is just frequently housed wrong.
The substrate is not where this animal lives
Peraccae does not dig in. It climbs, and it spends the daylight hours clamped flat against the underside of bark in groups, often stacked shoulder to shoulder. Watch a settled colony at night and you will see them working across vertical surfaces as much as the floor.
So the usual instinct, which is to build four inches of gorgeous substrate and lay one piece of cork on top, gives this species almost nothing. You have built a floor it will cross and a ceiling it will not use.
What it wants instead is surface area, stacked. Take four or five flat slabs of cork and pile them with small gaps between, propped so the gaps stay open. Lean more up the back wall. Each slab is another two faces the colony can occupy, and the difference between one piece and five is the difference between a tub that looks empty and one where lifting a slab shows you forty animals.
Two to three inches of a well-draining mix underneath is plenty. Our substrate guide covers the mix, and changing cork bark covers when to replace the slabs.
Humidity: a slope, not a setting
Aim for 60 to 75 per cent, and treat that as a range the tub passes through instead of a number you hold everywhere.
Water one end and leave the other alone. In a decently ventilated box that gives you something in the 70s at the damp end and the low 60s at the dry end, and the colony will redistribute itself through the week without any input from you. If you find them consistently piled at one end, that end is telling you where the tub actually sits, which is more useful than a hygrometer reading taken in the middle.
Ventilate through two facing walls if you can. Still air anywhere in this range is what turns uneaten food furry, and mould is a much more common cause of trouble here than the humidity figure itself. There is more in enclosure ventilation and humidity and in the general humidity guide.
Mist the damp end. Do not fog the whole surface, because that flattens the gradient and removes the choice you built it for.
Temperature
18 to 24°C, which is an ordinary heated British house across most of the year and needs nothing plugged in.
It will sit through a winter dip into the mid-teens without harm, though it slows and breeding tails off until things warm again. The end to watch is the top: sustained warmth above the mid-twenties, particularly in a box that is also damp and poorly vented, is where colonies get into trouble. If your summer room runs hot, improving the airflow does more good than anything you can do with water. Our room temperature guide covers the general case.
Feeding
The staple matters more than the extras, and for a species this heavily armoured the calcium matters more than either.
White-rotted hardwood and hardwood leaves should be down permanently and should be the bulk of the diet. Everything else is a supplement to that, not a replacement for it.
Protein two or three times a week, in amounts the colony clears inside a day. Small and frequent beats one large weekly offering, because leftovers are what grow mould. Calcium stays available permanently as cuttlebone or a lump of limestone, and an animal moulting its way up to 18mm gets through a surprising amount of it. The calcium guide has the detail.
Breeding
It breeds readily once established, and establishment is the slow part. A starter group will often do nothing visible for two or three months, then begin producing steadily with no further intervention from you.
The most common reason a group stalls is density. A dozen animals in a large tub take a long time to find each other and reach the point where breeding takes off. Start them in something modest, let them fill it, and move them up later.
The second is bark again. A colony without enough sheltered surface spends its energy on finding somewhere to be. Broader troubleshooting sits in our breeding guide.
Starting a group
Ten to fifteen animals is a sensible starting point, and the tub should be smaller than instinct suggests. A two or three litre box with a good stack of cork will establish faster than a large display enclosure, because the animals find each other sooner and the gradient is easier to hold steady across a short distance.
Expect very little for the first fortnight. A new group will vanish under the bark and stay there while it settles, and opening the lid repeatedly to check on them slows that down. Feed lightly, keep the damp end damp, and leave them alone.
Once you are seeing juveniles reliably and the adults are visible on the cork in the evenings, the group has taken. That is the point to move them somewhere larger if you want to, or to split a portion off into a second tub as insurance. Keeping a backup culture of anything you would be annoyed to lose is worth the ten minutes it costs, and it is easier to do while a colony is producing well than after something has gone wrong.
What a settled colony looks like
Worth knowing, because this species hides so completely that people assume something has gone wrong when nothing has.
Lift a slab and you should find animals packed against the underside in a cluster, holding still for a moment before moving off together. That clustering is normal and is what you want to see. Animals scattered singly across the substrate, or all crowded at the damp end, usually mean the gradient has collapsed in one direction or the other.
Juveniles look wrong at first. They are paler and smoother than the adults, and the coarse tuberculate back that gives this species its trilobite look only develops as they grow, so a batch of young among slate-grey adults can read as a contaminant instead of the next generation. Give it a couple of months before drawing conclusions.
The other good sign is uneaten food that dries out and does not go furry. If protein is growing mould before the colony finishes it, the airflow needs attention whatever the humidity reads.
Common questions
Is peraccae a beginner species?
Yes. It sits at ordinary room temperature, wants a middling humidity that most setups hit without effort, and is large enough to be easy to see and count. The only real requirement is that you give it enough bark.
Why can I never see my colony?
Almost always not enough cork. This species packs under flat surfaces in groups, so with one slab in the tub everything will be underneath it. Add more, stacked with gaps, and you will start seeing them.
How big does it get, and how quickly?
Around 17 to 18mm, which is large for the genus, and it is in no hurry. Expect the better part of a year for a juvenile to reach adult size.
Can I keep it with other Armadillidium?
You can, but mixed cultures make it hard to tell which species is thriving and which is quietly disappearing, and hybridisation is a real risk within the genus. Keeping it alone is simpler. More on the genus in our Armadillidium care guide.
What else is like it?
Armadillidium gestroi was described by the same author in the same year and takes much the same setup, which is rare enough in this genus to be useful. Corcyraeum is another narrow-range species, though a considerably smaller animal.
Everything we breed is listed under isopods for sale.
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