Woodlice

"Everything from the humble woodlouse to specks of dust moving through
a ray of sunlight. Each tells a story".
- Fennel Hudson

introduction

Woodlice are members of the families Armadillidiidae and Porcellionidae, and are known for their ability to roll up into a ball when threatened. They have acquired many common names, including Pill Bugs, Roly Polies, Slaters, Potato Bugs, Butchy Boys, and Doodle Bugs. The overlapping plates that cover their bodies are called tergites, which are connected by flexible joints that allow for conglobation (rolling up). They are masters at breaking down decaying or decomposing plant matter, making them garden superstars. Pill bugs will also munch a little on living plants, especially in wet conditions and when there are no other food sources readily available.

These organisms have gotten some bad press in agricultural circles due to their proclivity for processing decaying plant matter. In agricultural fields, this debris is typically piled or left in large quantities to sit out and decompose into the soil once crops are harvested. After the plant matter is gone, however, large populations of woodlice that were attracted by its presence look for other things to eat, which typically is what is next planted in the field. Numerous crops, including soy, corn, beans, squash, melon, chard, beet, cucumber, potato, spinach, lettuce and strawberry have been damaged on a large scale due to this unfortunate circumstance.

Woodlice are known for rolling themselves into balls.

Woodlice use have two pairs of antennae.

Woodlice are isopods, and look similar to the giant isopods that live in the ocean.

Their hard, shell-like exoskeleton must be shed progressively as they grow. Each molt takes place in two stages; the back half is shed first, followed two to three days later by the front half. This allows woodlice to maintain partial mobility while in the process of molting. Woodlice are born with six pairs of legs and six body segments, and gain their last segment and pair of legs in their final molt. As adults, woodlice have one pair of prominent antennae, one pair of inconspicuous antennae, and seven pairs of legs.

Woodlouse Behavior

Woodlice are typically nocturnal and are detritivores, feeding mostly on dead and decaying plant material. They do not typically do well in very dry situations, preferring to stay near moist areas and sources of water. In dry climates or if they get stranded in a dry area, they will die. Woodlice need moisture; they rapidly lose water thorough their body orifices and so they are typically found in damp, dark places of the landscape, such as under rocks and logs.

Infant-stage woodlice are almost translucent.

Female woodlice keep their fertilized eggs in a marsupium.

Nymph woodlice (mancas) do not develop color or a hard exterior for at least the first few weeks of their lives.

Woodlouse Species

Worldwide, there are approximately 3,500 species of woodlouse. They are found in practically every habitat, and are members of the suborder Oriscidea. Their common name is derived from their proclivity for decaying wood.

Armadillidium nasatum
(Nosy Pill Woodlouse)
This western European species has a protrusion (nose) towards the front of its head, and is typically dark brown to black. To 0.8 inches.

Armadillidium pulchellum
Native to Europe, these woodlice reach 0.2 inches in length and is spotted with yellow dots and has is often reddish-brown at its edges.

Armadillidium vulgare
(Roly-Poly)
Native to the Mediterranean and naturalized in almost all ecosystems. Can reach up to 0.7 inches long. Dark body.

Ligia oceanica
(Sea Slater)
To up to 1.2 inches in length, these coastline-dwellers are native to the European North Sea and Atlantic areas. Grey to olive-green in color.

Oniscus asellus
(Common Shiny Woodlouse)
To 0.6 inches long, this species is native to the British Isles and Europe. Shiny brown/grey.

Philoscia muscorum
(Fast Woodlouse)
Up to 0.43 inches long, with its body raised up off the ground for faster speeds. Mottled grey-brown body.

Platyarthrus hoffmannseggii
(Ant Woodlouse)
0.16 inches long, this pale woodlouse typically hangs out near ant nests and is thought to be blind.

Porcellionides pruinosus
Native to Europe, this species has a widespread distribution, and is a common pet. There are many color forms, and they live for between 1 and 2 years.

Porcellio laevis
(Swift Woodlouse)
To 0.8 inches long, these woodlice are capable of quick bursts of speed, and are commonly kept as pets.

Porcellio scaber
(Rough Woodlouse)
To 0.8 inches long with a grey coloring.

Porcellio spinicornis
This species of woodlouse is widespread in Europe and North America, with a dark grey-brown body with rows of yellow blotches.

Trachelipus rathkii
(Rathke's Woodlouse)
This European species is common in North America, and reaches up to 0.6 inches long with a light brownish-orange body.

Woodlice in the garden

Having woodlice in the garden is a great indication that there is either very healthy soil in the landscape, or that there is a lot of decaying debris present. They are largely considered beneficials, despite some of their recent bad press, causing little to no damage to healthy plants. Large numbers of woodlice will congregate near compost bins, where they are very helpful in creating the black gold used to improve soil quality, texture, and fertility. They typically do not enter into homes, unless lost or in search of food, but do not last long in indoor environments due to the fact that they need a moist environment to survive.

Offer Places to Hide
Woodlice are primarily nocturnal, and during the day will hide in damp, dark places. They are commonly found under logs and stones, in soil, or crawling along the ground. They do not typically climb plants, preferring to stay in areas that have a lot of moisture so that they don't dry out.

Cut Out Pesticide Use
Pesticides hurt not just the pests targeted; they typically also affect the populations of beneficial insects and related organisms, as well, including woodlice. Since woodlice are so beneficial to the garden, mainly to soil health and the breakdown of decaying material, removing chemicals that can harm them is critical.

Encourage Biodiversity
Plant a variety of plants in the landscape (the more natives, the better). This will attract a variety of insects, which will provide the food source that will draw woodlice into the garden and keep them working for you and your soil.

Keep Your Soil Healthy
Healthy soil is one of the most basic things that gardeners can offer beneficials in home landscapes. Many soils in urban areas are dead, and do not contain any living ecosystems. Healthy soil can be built in as little as 2-3 years, and is the foundation of all biodiversity in the landscape. Keep soil well-drained and nutrient-rich to maintain its health.