Pill bugs and sowbugs are often grouped together under names such as roly-polies, woodlice, or terrestrial isopods. They are related, but they are not interchangeable in a classroom investigation.
If the lesson depends on a particular behavior, order by scientific name rather than by common name. Armadillidium vulgare is the familiar pill bug that can curl into a compact ball. Porcellio scaber, commonly called the rough sowbug or rough woodlouse, does not form the same defensive ball. That difference gives educators a useful choice—and can support a side-by-side comparison.
Both are terrestrial crustaceans, not insects. The better species for a class depends on the question students will investigate.
The quick comparison
| Classroom consideration | Armadillidium vulgare | Porcellio scaber |
|---|---|---|
| Common classroom name | Pill bug or roly-poly | Sowbug or rough woodlouse |
| Easily observed distinction | Can roll into a ball, a behavior called conglobation | Does not form the same defensive ball |
| Useful question | When does an animal remain active, pause, or conglobate? | When does an animal remain active or become motionless? |
| Best reason to choose it | The lesson specifically involves conglobation or pill-bug identification | The lesson benefits from a contrasting defensive response or a second isopod species |
| Current small-count listing | 10 A. vulgare isopods | 10 P. scaber sowbugs |
Choose Armadillidium vulgare when rolling behavior matters
The clearest reason to choose A. vulgare is conglobation. When this species curls up, its legs and softer underside are enclosed by the harder outer plates.
Conglobation is more than a convenient visual difference. In a controlled study, Jacob Smigel and Allen Gibbs measured water balance while A. vulgare was rolled up. Under their dry-air test conditions, conglobation reduced water-loss rate. The authors concluded that the behavior may help conserve water as well as provide protection from predators.
That research can lead to age-appropriate questions such as:
- Do all individuals conglobate during ordinary handling and observation?
- How long does each individual remain rolled up?
- Does the same individual respond the same way in repeated, gently conducted observations?
Conglobation should not be treated as a trick students must force the animal to perform. Some animals may not roll up on cue, and repeated poking or stressful handling can turn an observation activity into an animal-welfare problem. A result of “no conglobation observed” is still data.
Choose Porcellio scaber when you want a contrasting response
P. scaber cannot form the same compact ball as A. vulgare. Research has documented another defensive response in this species: tonic immobility, or remaining motionless after disturbance.
In a 2015 study, Ivan Tuf, Lucie Drábková, and Jan Šipoš found that the duration of tonic immobility varied among individual P. scaber. Body size and the type of treatment also affected the response. The important classroom lesson is not that every sowbug will “play dead” on command. It is that individuals can respond differently, so a class should record what actually happens instead of treating one expected behavior as the correct answer.
The published experiment used treatments that should not be copied casually in a classroom. A gentler activity can record behavior following routine transfer into an observation arena: moving, pausing, sheltering, or remaining motionless. Students can define those categories before observation and use the same procedure for every animal.
A simple two-species observation plan
A comparison works best when students know exactly what counts as an observation. One possible plan is:
- Label the cultures and data sheets with the scientific names.
- Prepare identical observation arenas before moving any animals.
- Keep observation time, light, temperature, moisture, and handling method consistent.
- Observe one animal at a time and record predefined behavior categories rather than impressions such as “brave” or “lazy.”
- Return each animal promptly to appropriate housing after observation.
- Compare the class results by species, then discuss variation among individuals within each species.
This activity can support conversations about classification, observable traits, operational definitions, repeated trials, and biological variation. It does not require students to assume that every member of a species behaves identically.
For housing and routine care, review the Ficarro Farms isopod care guide before the animals arrive. Set up habitats in advance rather than using the shipping container as long-term housing.
How many should a class order?
The species decision and the quantity decision are separate. Start with the lesson design:
- How many stations will run at once?
- How many animals will each station observe?
- Will students compare species, repeat trials, or both?
- Will the activity be a teacher demonstration or a small-group investigation?
The classroom isopod quantity guide walks through translating stations, animals per station, and separate observation sets into an order estimate.
Ficarro Farms currently lists 10-count options for both A. vulgare pill bugs and P. scaber sowbugs. A pair of small-count listings can support a modest side-by-side activity, but no single count fits every protocol. The product listings are for live animals; habitat materials and other supplies are separate unless a listing specifically says otherwise.
See the Ficarro Farms shop for the counts currently displayed, or contact Ficarro Farms before placing a larger or date-sensitive classroom order. Availability can change, especially when many classes need live animals at the same time.
The practical answer
Choose Armadillidium vulgare if the lesson requires a pill bug that can conglobate. Choose Porcellio scaber if the lesson benefits from a sowbug that remains extended and offers a contrasting defensive response. Choose both when the learning goal is comparison—and make the scientific names part of the lesson so students know which animal they actually observed.
Research references
- Smigel, J. T., & Gibbs, A. G. (2008). Conglobation in the pill bug, Armadillidium vulgare, as a water conservation mechanism. Journal of Insect Science, 8(44), 1–9.
- Tuf, I. H., Drábková, L., & Šipoš, J. (2015). Personality affects defensive behaviour of Porcellio scaber. ZooKeys, 515, 159–171.