We call them bugs, but they aren’t


common pill-bug

Furthering my plan of identifying some of the diverse animals that make my yard their home, I was out photographing what I thought were a single colony of pill-bugs. They live beneath some flowers in the wood mulch. Hundreds of them were following seemingly randomly paths. I assume they were working at recycling the woody debris and doing what ever else pill bugs do. After taking a few pictures, I let them be.

Many years ago in my junior high science class, we were tasked with creating pill-bug habitats in jars. I found a large mason jar (likely stolen from my mom’s stash for canning plums and peaches) and layered woody debris topped with moss inside. I misted the interior and introduced a half-dozen pill-bugs caught from the yard. Un-phased by their new home, the pill-bugs immediately set to work doing what they do. I must have taken the little habitat into school on the bus – the jar propped up in my backpack hidden in the dark. The pill-bugs didn’t seem to mind and were just as busy when I pulled them out in science class. I don’t remember if we discussed it in class (we probably did and I forgot) but, despite their name, pill bugs aren’t bugs at all.


common woodlouse

With a name that includes ‘bug’, I’ve always thought pill-bugs were insects with many names like sow-bug and wood-bug. These elephant-coloured armoured animals, have about as much in common with an elephant as they do with insects. It turns out pill-bugs are part of the isopod group called woodlouse (still sounds like a bug to me). They’re a terrestrial crustacean, distant relatives to shrimp and lobsters. A woodlouse is protected by a long exoskeleton and has 14 little limbs under their armour. Although, woodlice have tasty family members, they’re said to taste like urine (I have no idea who did that taste test).

It turns out my woodlouse colony (they seem to be living together) has at least two types of inhabitants, both introduced from Europe like my other yard inhabitants: house sparrows and purple deadnettles. The one with solid grey exoskeleton, is the common pill-bug (Armadillidium vulgare – top picture). You can identify this pill-bug by picking it up, if it rolls completely into a ball, it’s a pill-bug. The other woodlouse with a browner exoskeleton marked with tan spots is a common woodlouse (Oniscus asellus – bottom picture).

Woodlice are generally not a problem in a garden – mostly they eat woody debris, performing an important recycling function. They’re an army of crawling composters.