What Do Woodlice Look Like: A Friendly Guide to Identifying This Common Critter

Woodlice are fascinating little creatures that you might come across in your garden or while exploring the great outdoors. Belonging to the family of terrestrial crustaceans, these arthropods are closely related to aquatic crustaceans like crabs, lobsters, and shrimp.

Their unique appearance sets them apart from other insects you might encounter. These tiny creatures are oval-shaped and have a segmented exoskeleton, giving them a distinctive, pill-like appearance. In fact, they are often called pillbugs or roly-polies for their ability to roll into a tight ball when they feel threatened.

As terrestrial crustaceans, woodlice have adapted to life on land, but they still require moisture to survive. Thus, you’ll typically find them under rocks, logs, or leaf litter, where the environment is damp and suitable for their survival. Next time you’re out exploring, keep an eye out for these intriguing little creatures and appreciate their unique characteristics.

Physical Characteristics

Comparison with Other Species

Woodlice are small crustaceans that can be easily recognized by their exoskeleton and segmented, flat bodies. They are usually grey or brown in color, which helps them blend in with their natural habitats like leaf litter, rotting wood, or under rocks. Woodlice play a crucial role in breaking down organic matter in their environments.

When observing these little creatures, you might notice that they have a similar appearance to both spiders and centipedes. However, there are some key differences:

• Woodlice have a strong exoskeleton, which is segmented into 14 parts, and they are usually found in damp, dark areas.
• Spiders have two main body parts (the cephalothorax and abdomen) and possess eight legs.
• Centipedes have elongated, segmented bodies with one pair of legs per body segment and typically have more legs than woodlice or spiders.

To help you better understand the similarities and differences between woodlice, spiders, and centipedes, here’s a comparison table:

Remember, when you encounter these creatures in your surroundings, they all have their unique characteristics and important roles in their respective ecosystems. By being able to recognize their physical traits, you’ll have a better understanding of the diverse world of small invertebrates.

Life Cycle

Woodlice, also known as roly-polies or pillbugs, have a fascinating life cycle. Let’s explore it in detail.

Eggs: Female woodlice carry their eggs in a special pouch called a marsupium. This pouch is also known as a brood pouch, and it is where the eggs are protected until they hatch.

Hatch and Young: When the eggs are ready, they hatch into small, white, legless young called mancae. At this stage, they are still within the marsupium and continue to develop there for several weeks.

After leaving the marsupium, the mancae look like miniature versions of adult woodlice, but with fewer body segments. As they grow, they go through a series of moults.

Juvenile to Adult: Each moult allows the woodlice to grow larger and develop new body segments. They will moult several times during their lifespan. During this time, they are considered juveniles.

Once they have completed all of their moults, they are considered adults. Adult woodlice are capable of reproducing.

Lifespan: The average lifespan of a woodlouse is around 1-2 years.

Here’s a quick comparison of the life stages:

So during their life cycle, woodlice transition from eggs in a protective pouch to legless young, and then through multiple moults, they develop into adults capable of reproducing. Remember, as with all living creatures, variations in lifespan and appearance may exist in different woodlouse species.

Habitat and Distribution

Woodlice inhabit various environments, including gardens, forests, and even homes. They are commonly found in the United Kingdom (UK) and the United States (US). Here, we will discuss their habitat and some noteworthy aspects of their distribution.

Household Incursion

Sometimes, woodlice venture into human dwellings. You may find them in damp and dark areas of your house. For example, these creatures often seek refuge under logs, rocks, and leaf litter. Woodlice prefer to live in moist soil environments because they require moisture to survive.

Although woodlice are commonly found in various habitats such as forests, gardens, and leaf litter, they are not usually seen in tropical and desert areas. In these extreme environments, their preferred living conditions are harder to come by. Nonetheless, in their ideal habitats, woodlice are known to play a vital role in breaking down organic matter and contributing to the overall dynamics of soil ecosystems.

When it comes to managing woodlice in your house, ensuring proper moisture control can help keep these creatures at bay. Remember, woodlice are not harmful to humans, but their presence can be a sign of dampness or moisture issues in your home.

In conclusion, woodlice are adaptable creatures that can be found in various habitats across the US and UK. Their presence in households is usually an indication of excessive moisture, and addressing this issue can prevent them from becoming unwanted guests in your home.

Behavior

Peculiar Eating Habits

Woodlice are fascinating creatures, often found in dark, damp environments. These little critters stay in cool areas during the day, becoming more active at night. Their eating habits may seem unusual to you, as woodlice are detritivores, meaning they primarily feed on decaying organic materials. Examples of food sources for woodlice include dead plant materials, fungi, and compost. This makes them beneficial organisms in your garden as they help break down and recycle nutrients through the decomposition process.

While woodlice mainly consume decay, they sometimes snack on fruit, leaves, and seedlings as well. Be sure to keep an eye on your plants and take necessary measures to prevent woodlice from feeding on your precious seedlings. Since these creatures prefer cool and moist environments, maintaining a well-draining garden should prevent large congregations of woodlice.

Species Specifics

Nicknames Around the World

Woodlice are small, flattened crustaceans that can be found in various environments. They have earned numerous nicknames around the world including pill bug, roly-poly, sow bug, slater, armadillo bug, cheeselog, doodlebug, and potato bug. Some well-known woodlice species include Armadillidium vulgare, Porcellio scaber, and Oniscus asellus.

Armadillidium vulgare, often called the pill woodlouse, is a little different from the rest of its family members. It has the unique ability to roll into a ball, reminiscent of an armadillo, hence another nickname – the armadillo bug.

Porcellio scaber, also known as the common shiny woodlouse, is one of the most widespread species. As the name suggests, its exoskeleton has a shiny appearance.

Finally, Oniscus asellus, or the striped woodlouse, stands out with its distinctive, irregular striped pattern on its back.

Here’s a comparison table of these three species:

To help you easily identify these woodlice species, remember the following bullet-point features:

• Pill woodlouse (Armadillidium vulgare): rolls into a ball, also called armadillo bug
• Common shiny woodlouse (Porcellio scaber): shiny exoskeleton
• Striped woodlouse (Oniscus asellus): distinctive striped pattern on its back

Now that you’re familiar with these species and their unique characteristics, you can have a closer look while exploring your environment and appreciate these small, fascinating creatures.

Threats and Conservation

Woodlice are small, terrestrial crustaceans commonly found in moist habitats. They play an essential role in breaking down organic matter, which helps maintain a healthy ecosystem. However, they also face numerous threats in their natural environments. In this section, we will discuss the threats woodlice face and conservation efforts in place to protect them.

Predators and Pests

Woodlice have various predators that include birds, beetles, and toads. These predators naturally help control woodlice populations in the wild. In some cases, woodlice can become pests themselves, particularly when they infest damp areas of homes and gardens. Fortunately, they are not harmful to your health or property, but they can be a nuisance if their numbers increase. To keep them at bay, you can keep your home and surroundings clean and dry, thus ensuring that they don’t thrive and multiply.

Conservation and Wildlife

As part of the wildlife ecosystem, woodlice contribute to nutrient cycling and provide food for numerous predators. Despite not being endangered or threatened, their wellbeing is vital to maintaining natural balance. Efforts to conserve habitats can help protect woodlice populations. By being aware of these small creatures’ importance, the different factors that threaten them, and their role in the ecosystem, you can contribute to their conservation and play a vital role in sustaining biodiversity.

Remember that woodlice are essential for a healthy ecosystem, and maintaining their natural habitats will keep their populations thriving. So, the next time you see these small crustaceans, think about their vital role and do your best to educate others on the importance of conservation and wildlife protection.

The Role of Woodlice in the Ecosystem

Woodlice, our little crustacean friends, have a significant role in maintaining the health of ecosystems. You might not realize it, but they contribute to crucial processes like decomposition and nutrient cycling.

As detritivorous organisms, woodlice feed on materials such as:

• Leaf litter
• Decayed wood
• Fungi
• Bacteria

This feeding behavior helps break down organic matter, making essential nutrients available for plants to uptake. As they digest and metabolize these materials, woodlice also participate in the dispersal of microbiota by voiding fecal pellets, which further aids in the decomposition process (source).

Woodlice have a significant presence in various habitats. For instance, their density in European woodlands can reach up to 800 individuals/m², ensuring a steady contribution to soil dynamics. They are native to many landscapes globally, adapting well to different environments.

In addition to their direct contributions, woodlice indirectly influence other organisms in the ecosystem. Interestingly, the presence of woodlice has been associated with higher predation success by nursery web spiders. This interaction highlights how woodlice play a part in sustaining food chains in their habitats.

To sum it up, woodlice are humble yet crucial players in maintaining ecological balance. By breaking down organic matter and recycling nutrients back to the ecosystem, these little creatures keep our ecosystems nourished and thriving.

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Woodlouse from Australia

Subject: ID bug
Location: Sydney, Australia
January 22, 2016 2:36 pm
Hello,
I have found many alive and dead bugs in a bedroom. Sometimes they’re curled up in an almost ball.
Please help to identify them.
With thankd
Signature: N/A

This terrestrial Isopod is commonly called a Woodlouse, and those that roll into balls are frequently called Pill Bugs or Rollie-Pollies.

Letter 2 – Woodlouse from Alaska

Subject:  Identify
Geographic location of the bug:  Juneau, ak
Date: 10/11/2017
Time: 06:09 AM EDT
Found this in my bathroom. Can u tell me what it is
How you want your letter signed:  Albert Dick

Dear Albert,
We always love getting submissions from Alaska.  This is a Woodlouse or Sowbug, a terrestrial Isopod in the suborder Oniscidea.  According to BugGuide, they are found:  “wherever cool, dark, moist places are available to shelter woodlice from dryness and heat during the day” and they feed upon “Plant material, usually dead. If live plants are soft and moist enough on the outside, they will eat them and sometimes do damage.”

Letter 3 – Woodlouse and The Right to Life of the Lower Beasts

This one’s new to us!
August 9, 2009
Generally we like to emulate Albert Schweitzer(sp?) who thought all life forms had a right to exist and would gently sweep or shoo even bugs out of his dwelling. (We draw the line at mosquitos.) Most others are captured and released. Our cats take a different view. This bug lost his anntena (sp) in a battle before we rescued him. We would like to know what he is, He is very camera shy. Took us MANY attempts to get even these two shots. Tried the scanner for his underside, but he wouldn’t hold still! He has 12 legs. They seem translucent and they hold him up off the ground like a spider (only my daughter says his knees go in towards his tummy). He’s got no particularly interesting colours, just a brown/grey all over. He’s about 7 or 8 millimeters long. We’ re not very knowledgeable about bugs in general although we have some that we’ve done a bit of research on. Our assumption is that this is a male bug because of those two spikes on his rear end. We think a girl would have a third one (ovipositor). We’re willing to take instruction if we have made an invalid assumption. Thank you.
Not all girls are afraid of bugs!
southern Alberta, Canada

Dear Not All Girls …,
Thank you for your wonderful paraphrase of Albert Schweitzer’s world view.  We also believe in the Right to Life of the Lower Beasts, and this is getting us much heat lately from litigious readers who threaten to sue us after we provide them with free information.  We have a right to free speech, and we try to be courteous and respectful while making our beliefs regarding the Unnecessary Carnage of insects known.  Like you, we draw the line with certain species, including mosquitoes, but Argentine Sugar Ants are probably the one species we would love to eliminate from our Los Angeles home.  We also show no mercy with Aphids on our plants, meal moths and pantry beetles in our stored grains, and cutworms in our garden.
Your creature is a Woodlouse or Terrestrial Isopod in the suborder Oniscidea.  We hesitate to attempt any more specific identification that that.  According to BugGuide:  “Woodlice need organic matter, which can be found in most soils, and they need cool moist conditions. Many places that might seem too hot and dry have cool hiding places where they can wait out the dryness and heat.“

Update
August 15, 2009
Thank you most kindly for the information.  He/she appears to have been a sowbug.  Or at least that’s what he most resembled in the pictures provided.  We released him outside that same day so we hope he is doing okay even with his missing antenna.  We live in what is normally a very arid part of Canada, but we have had some unusually wet weather this summer.  That would explain why we hadn’t ever seen one before.  I agree that some bugs must be ruthlessly, albeit mercifully, eliminated.  But my list is also very short.  Even carpenter ants can be of some benefit as long as they remain FAR from my house.  In 5 years they had almost completely reduced to compost a trio of stumps in my front yard.  But when they attempted to set up residence under my steps I felt no compunction in exterminating them–as mercifully as I knew how.  My children were also taught (and my husband retrained) not to be mean to bugs.  I’ll have little success with my grandson, though.  His mother, alas, considers anything with more than 4 legs to be anathema. I sometimes feel like I have very little support in my view so it is wonderful to discover a site like yours.
Sincerely,
Not all girls are afraid of bugs! (or snakes, frogs, lizards, etc)

Letter 4 – Woodlouse from Ireland

Subject:  Bug
Geographic location of the bug:  Ireland
Date: 02/06/2019
Time: 08:39 AM EDT
Your letter to the bugman:  I have found two of theses and my skin is itchy could you tell me what it is
How you want your letter signed:  I don’t understand this

This is a terrestrial Isopod known as a Woodlouse and we doubt it has anything to do with your itchiness.

Letter 5 – Woodlouse in Belgium

Subject: The wall walking bug
Location: Belgium, Gent
April 5, 2017 6:34 am
Hello,
After a more general cleaning of my home, the next day I noticed this bug walking on the wall. It might have come out of the wooden beams(I live in the last floor, roof floor kind of an attic). It seemed to be intelligent because it moved only when I was gone. I took a picture while it was there. To take in account, our house has damp problems, but apart from that we try to keep it as clean and as dry as possible. There is not much light in the room in general. This bug was around 1cm long, it was the last days of April when I saw it.
Thank you so much for the great work that you do, I will be looking forward on an answer to hopefully receive an answer for what kind of bug this might be!
Signature: Katrina

Dear Katrina,
This is a common Woodlouse, a terrestrial crustacean often found in gardens.  Woodlice prefer dark, damp conditions.