Isopod taxonomy and classification: the messy world of isopod naming

When I first started keeping isopods, I had one species: Cubaris sp. “Panda King”. Then, like a lot of keepers, I realised just how deep the rabbit hole goes.

Growing up in the UK, my idea of a woodlouse was the small grey creature you found when you lifted an old plant pot or turned over a piece of bark. I don't remember giving them much thought. They were just woodlice.

Once I entered the hobby, I discovered an entirely different world: huge Spanish species, brilliantly coloured species from Vietnam, unusually shaped species from Thailand and Malaysia, and others originating from places as far apart as Madagascar, the Philippines and Oman. Some are striped, some spotted, some almost metallic. Others have body shapes that barely resemble the woodlice I knew as a child.

Then there are the morphs. One species can produce a whole collection of its own through different colours and patterns. It is easy to understand why people compare isopod keeping to Pokémon – you really do start wanting to “collect them all”.

Of course, collecting is only part of the appeal. Learning the needs of each species, getting a difficult colony established and eventually finding tiny mancae running around the tub is what keeps me hooked.

The deeper I have gone into the hobby, though, the more I have noticed another side to it…

…the names can be an absolute mess.

Taxonomy is simply the way we classify and organise living things. Before applying it to isopods, I think it helps to use a familiar example.

Let’s take the domestic cat. A simplified version of its classification looks like this:

Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Felidae
Genus: Felis
Species: Felis catus

Each level narrows the group. Animalia contains animals, Mammalia brings us down to mammals, Felidae takes us into the cat family, Felis is the genus, then Felis catus identifies the domestic cat itself.

We can follow the same idea with a common terrestrial isopod, Armadillidium vulgare:

Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Crustacea
Class: Malacostraca
Order: Isopoda
Suborder: Oniscidea
Family: Armadillidiidae
Genus: Armadillidium
Species: Armadillidium vulgare

Straight away, this clears up one common misconception: isopods are crustaceans, not insects. They sit within Malacostraca, alongside familiar crustaceans such as crabs, shrimp and lobsters.

Isopoda is also far bigger than the terrestrial woodlice we tend to focus on in the hobby. The World List of Marine, Freshwater and Terrestrial Isopod Crustaceans currently records 11,030 species, found everywhere from the deepest oceans to mountain habitats, caves and underground aquifers.

For Xoticbugs, it is the terrestrial side that interests me most. Terrestrial isopods sit within Oniscidea, and even this smaller branch is enormous. A recent global database project counted more than 4,100 described terrestrial species across 568 genera and 38 or 39 families. The authors also make clear that major gaps remain, especially in poorly studied parts of the world.

That helps put the hobby into perspective. The incredible range we already see for sale is still only one slice of the wider isopod world.

At species level, scientific naming should become fairly simple. Under zoological naming rules, a species name has two parts: the genus followed by the specific name. So in Armadillidium vulgare, Armadillidium is the genus and vulgare is the specific name. Together, they form the scientific species name.

Then you enter the isopod hobby and find something labelled:

Cubaris sp. “Rubber Ducky"

This is where things start getting messy. The abbreviation sp. indicates an unspecified or unidentified species within a genus. “Rubber Ducky” is not a formally described species name in the same way that vulgare is in Armadillidium vulgare. In practical terms, Cubaris sp. “Rubber Ducky” tells us that we are dealing with an unnamed species currently being placed within the genus Cubaris, while “Rubber Ducky” is the hobby name we use to identify that particular animal.

That distinction matters. Cubaris murina and Cubaris sp. “Rubber Ducky” are two quite different types of label. The first is a formal scientific name. The second combines a proposed genus placement with an informal hobby name.

Sometimes the identification is broader still. You might encounter something sold as Armadillidae sp. “…”. Armadillidae is a family rather than a genus, so this effectively says, “we can place this animal somewhere within Armadillidae, but we aren't confidently assigning it to a genus”. Something labelled Isopoda sp. “…” gives us even less certainty. Take the famous Isopoda sp. “Shiny Gator”, for example.

You may occasionally see cf. or aff. too. These are qualifiers showing that an identification carries some uncertainty rather than forming part of the scientific name itself. Cf. – from the Latin confer, meaning “compare” – is generally used when a specimen resembles a named species but its identification is uncertain. Aff. – from affinis, meaning “related to” or “having affinity with” – indicates that an animal appears closely related to a named species but may represent something distinct.

I think the hobby could sometimes benefit from being more comfortable with that uncertainty.

Hobby names have a very real purpose. In fact, I love them. Names such as “Rubber Ducky”, “Mango Sticky Rice”, “Ember Bee” and “Electric Blue” are memorable and make it possible for us to talk about animals that may not yet have formal scientific names.

The complication is that hobby naming isn't regulated. There is no official body deciding what a newly imported species should be called, or checking whether somebody else is already selling the same animal under another name. The name may come from the collector, importer, breeder or seller. If it catches on, it becomes part of the hobby.

This can make it really difficult to keep track, not only for beginners but for experienced keepers too.

One example I have personally come across recently is Cubaris sp. “Goldfish”. This animal has been in the hobby for several years but is still very rare, and I only got my hands on it last year. Yet the same species has also cropped up and been sold as Cubaris sp. “Piranha”. Someone new to the hobby could quite reasonably see Goldfish and Piranha on two sales lists and assume they were buying two different species.

Then the opposite happens: completely different animals are given names that make them sound related.

The word “Ducky” is perhaps the clearest example. Rubber Ducky became one of the best-known isopods in the hobby, and it didn't take long for Ducky to start appearing in the names of other animals. Amber Ducky, Helios Ducky, White Ducky and others all followed.

Take “Albino Ducky” and “White Ducky”. The names sound as though they should describe two pale or white versions of the same species. In the hobby, however, Albino Ducky is a morph derived from Rubber Ducky stock, while White Ducky refers to a completely different animal and separate species.

The shared word “Ducky” says more about hobby naming than it does about their relationship.

At the end of the day, we also have to acknowledge the commercial side of the hobby. A good name can transform the way an animal is perceived.

“Brown unidentified isopod from Thailand” is unlikely to attract the same attention as a memorable name accompanied by dramatic photographs and a story about a rare new import. Names help animals stand out on sales lists, social media posts and websites. They make them easier to remember, easier to search for and, importantly, easier to market.

Cool names create hype. Hype creates demand, and demand can push prices higher.

That does not mean somebody giving an isopod a memorable name is necessarily doing anything wrong. Most undescribed species entering the hobby need some practical label so that breeders can distinguish one stock from another. A hobby name is often the most sensible solution.

The difficulty comes when marketing starts to blur the distinction between a useful label and biological evidence.

Attaching the name of an already desirable species or group to something new can immediately make it sound familiar and collectible. If “Ducky”, “Bee”, “Panda” or another popular term already carries value in the hobby, using it for a new animal can create an implied relationship even where none has been demonstrated.

Colour can work in much the same way. An unusually red, yellow or pale individual may appear far more desirable once it has been isolated, photographed and given its own name. Sometimes that genuinely represents the beginning of a selectively bred morph. Other times, it may simply be natural variation that has acquired a marketable label.

That is why provenance matters so much. If two animals with different names are actually the same stock, or a supposedly new morph is simply ordinary variation, the commercial consequences are not trivial. A keeper may pay substantially more because the name suggests they are buying something biologically distinct.

The issue, then, is not that commercial naming exists. Isopod breeding is a hobby and a business for many people, myself included. Attractive names are part of what makes it fun. The important thing is that the name should not be allowed to imply more certainty than the evidence behind it.

What I found especially interesting while researching this article is that none of these concerns are new.

On 3 March 2022, an excellent discussion appeared on the r/isopods community under the title Important thoughts. Its main subject was the hobby's naming problem. It discussed Rubber Ducky morphs losing their original stock name, the same morph being given different names and vendors renaming animals to make them sound more appealing.

The discussion even moved into attempts to sort the many hobby “Cubaris” into rough groups, while acknowledging that these were artificial groupings based largely on what could be seen from above.

Keepers were already questioning Cubaris placement and the reliability of older terrestrial isopod classifications. Reading those conversations now is quite striking because so much of it could have been written today. We have more species, more morphs and more hobby names than ever, yet many of the same problems remain.

It makes me wonder what the situation will be in five years from now. Will some of today's Cubaris finally have proper genera? And will some of our popular current hobby names have disappeared completely?

That brings me to what I think is one of the biggest problems in current isopod classification: Cubaris.

An extraordinary range of animals circulate under Cubaris sp. names. Cubaris sp. “Purple Giant”, Cubaris sp. “Tropical Fire Ass”, Cubaris sp. “Electric Blue”, Cubaris sp. “Crabby” and many more are grouped under the same genus despite some having very different body forms.

I keep Cubaris sp. “Purple Giant” myself. To my completely unscientific eye, its shape reminds me much more of the general body form I associate with Troglodillo.

That does not mean I am going to relabel my animals as Troglodillo. I have no scientific basis for doing that, and they may eventually prove to belong somewhere else entirely. What it does make me question is how much confidence we should place in the Cubaris part of the existing hobby name.

There is good reason to be cautious. Isopod taxonomy has a history of animals being moved between genera as researchers compare new material with older descriptions. So when I look at the huge variety of undescribed animals currently grouped under Cubaris, I would be very surprised if lots of them remained there.

Hobby names become even more complicated once we add morphs.

A morph is a different form within the same species or stock, often selected for colour or pattern. Importantly, a morph isn't another formal rung on our taxonomic ladder. In the hobby, morph names are practical labels for the different forms we breed.

Cubaris sp. “Panda King” is a perfect example and happens to be where my own isopod collection began. Selective breeding has produced a huge range of Panda King forms. Pink Panda, Pink Rose, Red Panda, White, Yellow, Chocolate and other lines can all look different while tracing back to Panda King stock. I have gone much deeper into that side of the hobby in my separate article on selective breeding in isopods.

This is where keeping the history of a line becomes important.

If an all-pink animal appears within Panda King stock, is isolated, bred over generations and eventually produces a stable pink line, there is a clear story connecting the morph back to the original stock. Once that information disappears, however, “Pink Rose” can easily begin to sound like the name of a completely separate species.

The same morph may even acquire several names. The all-pink Panda King forms are a good example, with names such as “Pink Rose” and “Rosea” appearing within the hobby. If different breeders produce similar-looking lines and name them independently, the picture gets muddier again.

Then there are cases where similar names make us assume two animals are morphs when they may actually be different species.

Cubaris sp. “Red Pak Chong” has sometimes been described by keepers as simply a red morph of “Pak Chong”, despite the two being from very different localities and indeed being different species. Again, the name can push us towards an assumption before we have looked at what sits behind it.

A good friend of mine, Aran, actually led me to question another example, and our conversation partly inspired me to write this article in the first place. We were discussing Troglodillo sp. “Sunset” and Troglodillo sp. “Orange Mask” and began questioning whether they really are two separate species.

Looking at them, they appear remarkably similar, with their morphology to my untrained eye looking identical. Orange Mask seems to keep the typical Sunset orange colour around the face while much of the rest of its body is darker grey. My own suspicion is that Orange Mask could turn out to be a morph of Sunset rather than a completely separate species.

The key word there is suspicion. Neither Aran nor I sitting there comparing the two is enough to change their taxonomy. I would love to see them tested properly through controlled breeding, close morphological comparison and perhaps eventually genetic work. Until then, “I don't know” is the right answer.

That conversation made me think about how often we simply accept whatever name came attached to an isopod without stopping to ask who decided it, or what evidence sat behind that decision.

Natural variation creates another problem.

Ardentiella sp. “Ember Bee” is a good example from my own collection. A normal Ember Bee colony can produce a range of colours. Some animals are more yellow, others more red, with plenty sitting around the familiar orange.

I have then seen animals sold separately under names such as “Ember Bee Red” or “Ember Bee High Yellow”, sometimes for two to five times the price of ordinary Ember Bees. There is nothing wrong with selective breeding. Stable morphs developed over generations are one of the parts of the hobby I find most interesting. What I question is whether every unusually colourful animal needs a new name and a much higher price attached to it.

If I were paying a large premium for a special colour line, I would want to know how many generations had been selected, whether that colour reliably passed to the offspring, and whether I was actually buying a stable morph rather than normal variation within the species.

One of the biggest examples of just how much taxonomy can change came in 2025.

For years, some of the most spectacular Southeast Asian isopods in the hobby were kept and sold under the genus Merulanella. Ember Bee, Blister Fire, Crimson Diablo and many of the brightly coloured species familiar to collectors were associated with this group.

Then Benedikt Kästle and Omar Rafael Regalado Fernández published a major reassessment of Merulanella. Their work went back through historical specimens and old descriptions, then compared the animals in much greater anatomical detail. The result was a major reshuffle.

True Merulanella was restricted to New Caledonia, a French territory comprising dozens of islands in the South Pacific. Several other genera were recognised from animals that had previously been grouped around it, including Ardentiella – the name now applied to the part of the group most familiar to many hobby keepers.

The World List now recognises Ardentiella Kästle & Regalado Fernández, 2025 as a valid genus.

The paper even includes undescribed Ardentiella from Vietnam already circulating in the pet trade. I think that last point is fascinating. These weren't just forgotten museum specimens that had nothing to do with us. The hobby was already keeping some of the animals while scientists were still working out where they belonged.

When the revision was published, I changed the relevant labels in my own collection and on Xoticbugs from Merulanella to Ardentiella.

For me, that is exactly how we should approach taxonomy. We use the best information we have, then change the name when good published work gives us a better answer.

The study also shows why proper taxonomy is so different from looking at a sales photograph. Kästle and Regalado Fernández examined historical specimens and compared detailed morphological structures to separate these groups. These are the sorts of differences most of us would never see while looking into a culture tub.

Later in 2025 we got another brilliant example.

For years, an attractive orange-pink species from Martinique had circulated in the hobby as Cubaris sp. “Salmon”, or “Salmon Martinique”. It was already being bred and sold under that provisional name.

When Kästle (again), Binder, Jones and Coulis formally studied the animal, it did not simply become a newly named species of Cubaris. They described a new genus and a new species: Caribodillo martinicensis.

I love this example because it captures the whole issue in one animal. Cubaris sp. “Salmon” wasn't a bad name. It allowed keepers to identify and discuss the species for years. It was simply the best working label we had at the time.

Then the science caught up.

This is where things become much more technical, and where I freely admit the limits of my own knowledge.

I have never sat down with an unidentified specimen, a microscope and a taxonomic key and tried to formally identify it. I wouldn't know where to begin without guidance.
What I have learned while looking into this, though, is how little colour alone can tell us.

Taxonomists may look closely at the cephalon and frontal structures, pereonites, pleon, telson or pleotelson, uropods, antennae, respiratory structures and male pleopods, among other features. Depending on the group, small structures underneath the animal may tell us far more about its relationship to another species than the striking pattern across its back.

The Ardentiella revision is a good example of this. The researchers compared features such as body form, the pleotelson, uropods and other fine anatomical details when reassessing the genera.

That explains something that can seem strange from a keeper's point of view. Two animals may look almost identical in photographs and still prove to be separate species. Equally, two animals with dramatically different colours may turn out to belong to the same species.

Breeding can give us useful evidence, particularly when we are trying to work out whether two captive colour forms are morphs of the same stock.
I used to think about the species question quite simply: if two animals can breed together, they are the same species; if they can't, they are different. This is not true.

The ability to interbreed does not provide a universal definition of a species. Different groups can present much more complicated biological situations, which is one reason taxonomists may rely heavily on morphology alongside other evidence when distinguishing terrestrial isopods.

If we know an animal came from a particular cave, island, mountain, province or collection site, that information should stay with the culture. It gives us something real to work with.

Personally, I would often prefer a locality-based hobby name to be paired with a fictional descriptive name. It creates less ambiguity and preserves useful information about where the stock actually came from.

If two near-identical animals originate hundreds of miles apart, that may prove important later. Likewise, knowing that two supposedly different hobby animals came from the same place may give researchers another clue when they eventually compare them.

This matters because terrestrial isopod taxonomy is nowhere near finished. The OniscidBase project records more than 4,100 described Oniscidea but stresses that taxonomic knowledge remains incomplete. Those gaps overlap with many of the tropical parts of the world producing some of the most unusual animals now entering collections.

New species can enter the hobby much faster than science can formally work through them. An animal is found, exported, established by breeders, photographed, named and sold. Before long, keepers across several countries may have it. A scientific description takes much more.

After all of this, I don't want the takeaway to be that hobby names are bad. They are a huge part of what makes isopod keeping accessible and fun.

We just need to understand what they actually tell us.

A formally described species such as Armadillidium vulgare carries very different weight from Cubaris sp. “Rubber Ducky”, a Panda King morph name or an Armadillidae sp. label.

As keepers and sellers, the best thing we can do is preserve locality and lineage information, avoid treating every colour change as a new species, and update names when better scientific work becomes available.

Merulanella becoming Ardentiella and Cubaris sp. “Salmon” becoming Caribodillo martinicensis show that some animals can already be well established in the hobby before science has fully worked out where they belong.

What is perhaps most striking is that keepers were already raising many of these same problems on Reddit in 2022: the Cubaris catch-all, morphs gaining new names and sellers renaming stock. More than four years later, much of that
discussion still feels current.

Either way, I suspect some of the tubs in our collections today will carry very different labels by 2040 or even 2030.

For me, that uncertainty is part of the appeal.

There is still so much left to learn.

The name on the tub is our best answer for now. It doesn't always mean it will be the final one.

"A classification system that is still being written"