Turn over a proverbial new leaf, or perhaps a damp flowerpot? Discovering critters in the wild is one of biology's best teaching assistants. You never know what may be waiting underneath. This blog is about the art and science of animal behaviour, including how to have fun in class without driving the teacher to early retirement.
Roly-polies or Pill Bugs, as they are often called, are calm enough to observe, slow enough to count and gifted with the sort of physical comedy that made the acrobatic pill bugs in A Bug's Life such scene-stealers.
They are also scientific impostors of the best kind. A pill bug is not an insect. It is a terrestrial crustacean, related to crabs and shrimp. They have adapted to life on land while still carrying a strong preference for moisture. Put several isopods in a choice chamber and a patch of damp filter paper suddenly becomes an animal behavior class.
Affiliate disclosure: This article contains an affiliate link to Carolina Biological. Clicking is free. If you make a purchase through this link, Bug Zoo® may earn a commission at no additional cost to you.
The isopod room I did not know existed
Years ago in Montreal, I met a serious isopod hobbyist who had an entire room filled with cultures he had collected from all over the world. There were hundreds of different species and varieties. He wanted to show me every one of them. They were very cool. I like the science of "bugs" but even I was amused at his enthusiasm.
Roly-poly enthusiasm runs much deeper than the occasional child lifting a garden stone and pocketing the goods for Mom to discover later when cleaning out the pockets to do laundry. Surprise!
Hobbyists keep colorful species, trade selectively bred morphs and debate the finer points of humidity, ventilation and identification. It's a niche. The names alone can sound like the dessert menu at an eccentric science convention. Rubber Duckies, Dairy Cows, Cappuccinos and Bumblebees all exist in the hobby lexicon.
The classroom kit featured here is designed for animal behavior rather than pet keeping, but it taps into the same fascination. Give people a closer look at an ordinary little creature and ordinary disappears rather quickly.
Five roly-poly facts for the dinner table
- They are crustaceans. Roly-polies belong to the order Isopoda alongside marine and freshwater relatives. NOAA estimates that scientists have described about 10,000 isopod species living everywhere from backyards to the deep sea.
- They have seven pairs of walking legs. The name Isopoda means “equal foot,” a reference to those similarly shaped limbs. This is useful information whenever dinner conversation has become too comfortable.
- Rolling up has a proper scientific name. It is called conglobation. True pill bugs can form a defensive ball, while many sow bugs cannot close themselves completely. Calling every woodlouse a roly-poly is therefore taxonomically casual, although extremely satisfying.
- Females carry their developing young in a pouch. The pouch is called a marsupium. Researchers have studied how this remarkable structure protects and supports developing offspring in terrestrial isopods. Read the open-access ZooKeys study of the isopod marsupium.
- Isopods are ancient. A fossil described in Science shows that the group was present roughly 300 million years ago. That is an impressive run for an animal still routinely discovered beneath a damp board. See the original fossil report.
If those facts awaken an unexpected desire to see designer isopods, the independent Isopod Site documents species, anatomy, photography and the increasingly elaborate keeping hobby. There goes the afternoon.
What can pill bugs teach about behavior?
A choice chamber offers two environments connected by a passage. Students place the animals in the chamber, record where they move and ask whether the distribution differs from chance. The apparatus is simple. The thinking does not have to be.
Pill bugs are especially useful for exploring taxis and kinesis. Taxis is directed movement toward or away from a stimulus. Kinesis is a change in activity, such as speed or turning rate, that is not itself directional. An isopod may remain longer in a damp area because its movement changes as conditions improve. Watching the final head count is only the beginning. The path, pace and pattern can reveal more.
Good questions practically volunteer:
- Do isopods spend more time on moist or less-moist filter paper?
- Does a covered area attract more animals than an exposed one?
- Does surface texture influence movement?
- Do results change when the chamber is rotated and the two conditions switch sides?
- Can repeated trials distinguish a real preference from random wandering?
This is where animal behavior becomes fun. Students have to make a prediction, define variables, count carefully and defend an explanation. The roly-polies may not read the lesson plan, which is exactly why the experiment works.
Inside Carolina's animal behavior kit
Carolina's Inquiries in Science: Behaving Like Animals Kit is intended for Grades 9 through 12. It provides materials for 30 students working in groups of three and is also recommended by Carolina for International Baccalaureate biology.
The current product listing includes:
- 125 pill bugs supplied through a perishable-materials voucher
- 10 choice chambers
- 100 sheets of filter paper
- 10 sorting brushes
- A digital Teacher's Manual and Student Guide
Teachers must request the living materials using the included voucher, so delivery timing belongs in the lesson plan. Carolina also lists several ordinary supplies that are needed but not included, such as small water containers, a spray bottle, spring water or dechlorinated tap water and paper towels.
At the time of this review, Carolina lists the complete kit as Call for Pricing. That makes it a more natural fit for a high-school teacher, biology department, IB program, co-op or substantial science club than for one family seeking a casual weekend activity. The value is in having classroom quantities, standardized chambers and teaching materials gathered into one package.
Keep the experiment curious and kind
Living animals turn a laboratory exercise into a responsibility. Keep conditions within gentle, biologically sensible ranges. A moisture comparison does not require baking one side bone-dry, and a light comparison does not require cooking the chamber beneath a hot lamp.
Move isopods with the sorting brushes or let them walk onto a surface rather than pinching them. Keep chambers ventilated, observations reasonably brief and moisture available. Return the animals to appropriate housing after each trial. Commercially supplied organisms should never be released outdoors unless the supplier's directions and local rules explicitly allow it.
The point is to observe choice, not discover how much discomfort a tiny crustacean can tolerate. Carolina provides a terrestrial isopod care guide for planning the living-animal portion of the lesson.
Carol's verdict
This kit earns its place when a teacher wants a complete, inquiry-based animal behavior lab for a full class. The choice chambers and classroom quantities remove a considerable amount of scavenging, improvising and counting pill bugs in a parking lot five minutes before the bell.
It is oversized for a single curious hobbyist, and the lack of a public price adds an extra step. For a high-school biology class ready to move beyond vocabulary and into observation, experimental design and argument from evidence, it has a strong and wonderfully wriggly premise.
View the Animal Behavior Kit at Carolina (affiliate link)
Clicking is free. Bug Zoo® may earn a commission if you buy, at no additional cost to you.
Questions people ask about roly-polies and the kit
Are roly-polies insects?
No. Pill bugs and sow bugs are terrestrial isopod crustaceans. Insects have six legs; adult isopods have seven pairs of walking legs.
Why do pill bugs prefer damp places?
Terrestrial isopods use specialized respiratory structures that need suitable moisture. Damp, sheltered habitats also reduce water loss, which helps explain their famous devotion to flowerpots, logs and the underside of almost anything left on the ground.
What is the difference between a pill bug and a sow bug?
A true pill bug can usually roll into a compact ball. Many sow bugs have projecting rear appendages and cannot close into a complete sphere. Both are terrestrial isopods, and common names vary by region.
How many students does the Carolina kit support?
Carolina states that the kit contains materials for 30 students working in groups of three, using 10 choice chambers.
Are the live pill bugs automatically shipped with the kit?
The complete kit includes a voucher for the perishable materials. The teacher must contact Carolina or return the voucher to arrange delivery, so confirm the current process before fixing the lab date.
Reviewed by Carol Maier, B.Sc., professional entomologist and founder of the original Victoria Bug Zoo.
This is an independent editorial review based on Carolina's current product information and cited scientific sources, not a hands-on test of the kit. Contents, pricing, availability and shipping requirements can change.
Thanks for supporting our mission to make the world a better place for everyone, bugs included.