Woodlouse

Quick Take

• That tiny garden bug you've been calling an insect your whole life? It's actually something far more unexpected. See its true taxonomy →
• A woodlouse has a secret defense move beyond curling into a ball, one that predators apparently hate. Explore its defense behaviors →
• Finding woodlice in your home is not random. It is a warning sign about something lurking in your walls or floors. What infestations signal →
• Woodlice have outlasted most creatures on Earth, and the reason traces back over 300 million years to a dramatic habitat switch. Trace their 300M-year history →

When a woodlouse feels threatened or in danger, it rolls its body up into a ball so only its shell is visible. A rolled-up woodlouse looks kind of like a pill. That’s how it earned the name pill bug. One of the most surprising facts about a woodlouse is that it’s a terrestrial crustacean and not an insect.

These tiny creatures feed on mildew, fungus, decaying leaves, and materials found in a compost pile. By eating this decaying material, woodlice help to release nutrients into the soil. During their two-to-three-year lifespan, they play an important role in the ecosystem.

4 Incredible Woodlouse Facts

• A woodlouse has 14 legs.
• Its exoskeleton, or outer shell, has the appearance of armor.
• Most of the time, they are found in a damp, dark environment.
• The life cycle of this crustacean includes these stages: eggs, baby (manca), juvenile, and adult. Their lifespan is two to three years.

The Evolution and Origins of Woodlice

Woodlice are a group of small crustaceans that belong to the order Isopoda. They have been around for over 300 million years, making them one of the oldest groups of terrestrial animals. Woodlice are found all over the world, and they occupy a wide range of habitats, from damp forests to urban gardens.

The evolution of woodlice can be traced back to their aquatic ancestors, which lived in the seas and oceans during the Carboniferous period, approximately 300 to 360 million years ago. Over time, some species of isopods evolved to live on land, adapting to the harsh conditions of the terrestrial environment.

Woodlice have a hard exoskeleton that helps to protect them from predators and environmental stress. They also have a unique respiratory system, which allows them to breathe air without drying out, and they are capable of surviving in a wide range of temperatures and humidities.

Woodlice’s adaptability has allowed them to thrive in many different habitats, from damp forests to urban gardens. They feed on decaying plant material, and their presence is an important indicator of soil health and fertility.

To summarize, woodlice are an ancient and fascinating group of crustaceans that have evolved and adapted to survive in a variety of environments. They play an important role in many ecosystems, breaking down dead plant material and recycling nutrients, and providing valuable insights into the evolution of life on land.

Classification and Scientific Names

Woodlice belong to the Order Isopoda and are spread across many families, including Armadillidiidae, Armadillidae, Agnaridae, and Alloniscidae, among others. There are 3,500-plus species of woodlice. One woodlouse species is Armadillidium vulgare. The name Armadillidium is derived from the Spanish word armadillo, meaning ‘little armored one,’ and refers to the creature’s armored body and ability to roll into a protective ball.

Some types of woodlouse are:

• Painted pill woodlouse — Armadillidium pictum
• Granulated pill woodlouse — Armadillidium granulatum
• Nosy pill woodlouse — Armadillidium nasatum
• Southern pill woodlouse — Armadillidium depressum

Appearance

A woodlouse has a shell that is dark gray or black. One of its most well-known features is its armor-like exoskeleton made up of seven plates. They have two legs on each of these seven plates, making a total of 14 legs on this little creature. Its body measures from 0.7mm to 18mm in length and is approximately 5mm wide. This crustacean has two short antennae on its head.

The main defensive behavior of a woodlouse is to roll into a ball at the first sign of a threat. This is a way to cover its vital organs to protect them from a predator. It can also secrete a foul-smelling chemical that repels predators. In addition, the gray or black color of this crustacean helps it to blend into its moist, dark habitat.

The lifespan of this creature is two to three years, so its defensive behavior is certainly effective!

Woodlice live in groups. If you lift a rock in a garden or look into a compost pile, you’re likely to see dozens of woodlice. An individual is called a woodlouse, two or more are woodlice, and a group is called a colony.

Habitat

One of the most amazing facts to remember about woodlice is that they live in all places in the world except Antarctica. They live in temperate to tropical climates. Gardens are a common habitat of this crustacean. Woodlice and their eggs are also found under piles of leaves, rocks, downed trees, and in the soil. Moisture and darkness are the two main features of its habitat.

Sometimes woodlice find their way into homes, especially if there is a welcoming habitat near the structure. Picture a group of woodlice living in a pile of rotting wood near the wall of a home. It wouldn’t be a surprise if a few woodlice made their way inside the house from time to time. They would only stay in a home if they found mold or another food source.

Diet

Generally, the diet of a woodlouse is herbivorous. But scientists categorize it as a detritivore because of the specific material it eats. The word detritivore contains ‘detritus,’ meaning decaying or rotting material in the environment.

What does a woodlouse eat?

The diet of a woodlouse includes decaying leaves, fungus, mold, and even the droppings of other animals. So, now you see why they are called detritivores.

What eats a woodlouse?

The predators of a woodlouse include frogs, shrews, centipedes, and spiders. All of these predators share the same habitat as the woodlouse. Baby woodlice are even more vulnerable to these predators because their shell is not as sturdy.

Prevention

If you see one or two woodlice in your home, know that they are not harmful in any way. But if you notice several of them, including baby woodlice, it may mean they are feeding on mold or mildew inside your home. You may have some rotting wood due to water damage in a ceiling or floor.

Fixing the damage is going to remove any reason for woodlice to be in your home. They would rather be in your garden.