EUROPEAN SOWBUG
Oniscus asellus

Bug Index                      

 Assassin Bug

Bigeyed Bug

Boreal Firefly

Bumblebee

Damselfly

Dragonfly

Giant Diving Beetle

Giant Stoneflies

Giant Water Bug

Ground Beetles

Honey Bee

Lacewings

Ladybird Beetle

Mealybug-Destroyers 

Millipede

Pirate Bugs

Praying Mantid

Predatory Mites

Rove Beetles

Sowbug

Syphid Fly

Tachnid Fly

Yellow Jacket


Sowbugs are not insects, as is evident by the number of legs, seven pairs as opposed to the three pairs that insects have. Sowbugs are actually crustaceans, so their closest relatives include things like fresh water shrimp, crabs, crayfish and lobsters. Sowbugs are often common in gardens, hiding in damp places under logs and rocks. They feed primarily on detritus, dead plant and animal matter, including rotting wood. They are very effective decomposers and are often an integral part of a compost heap.

Identification: The oval shape, greyish color and fourteen legs should separate the Sow Bug from any other creature. Adults may be up to 15 mm long (about 1/2 inch). 

Distribution: This is not a native species, although it is found throughout much of North America. It was introduced from Europe. In Canada and the United States it is presently restricted to cities and suburbs, and is probably found in most larger communities.

Sowbugs are dormant in the winter. But, when the ground thaws in the spring, they become active and stay active until the first hard frost.

Habitat and habits: Sowbugs love dark, damp places and are most common in yards under wood or rocks. The more tangled an area one has, the more likelihood they are present. Compost heaps are a great retreat for this animal. They also often crawl through spaces in the foundation or through basement windows and end up in the basement where they can survive quite well if the basement is unfinished. They feed primarily on detritus, dead plant and animal matter, including rotting wood.

Comments: People often find these creatures in their basements, and are concerned about the possibility that they may do damage to the house or that they may be dangerous in other ways. Older houses with dry rot might suffer some damage as a result of Sowbugs, but this is likely to be minimal. They cannot bite humans and are not poisonous. In some areas some species of Sowbugs can be pests on cultivated plants. They are also very effective decomposers and are often an integral part of a compost heap.