Show a real wood bug. Ask if students have seen them before in parks or gardens.
Ask what are the needs of an animal to stay alive? (food, water, shelter). Wood bugs have these needs too.
Class discussion of the needs of wood bugs (food, water and shelter), including where they like to hide, and what they like to eat. This discussion can be based on experiments done in class (see other activities in the lesson plan), and/or by a walk to find and observe wood bugs in their natural environment (wood bugs are easily found in the fall or spring under logs and rocks in gardens and forests).
Wood bugs’ food is rotting wood and leaves, so wood bugs are often found in the upper layer of a compost heap. Wood bugs are decomposers and eat dead plants (as well as some live ones). Decomposers are a crucial part of the cycle of life on earth.
Wood bugs need water to drink, as do all living things. They also need water in the air from which they obtain their oxygen (they do not breathe oxygen gas as we do). Wood bugs evolved from, and are closely related to, shrimp-like marine organisms. Like these ocean animals, they have gills - using them to extract oxygen from water. Because of this, they always need to be in a moist environment, and will die fast if they dry out.
For shelter, wood bugs like to live in moist dark places, such as under paving stones, rocks and chunks of rotting wood.
See reference for more information and different kinds of wood bugs: http://en.wikipedia.org/wiki/Woodbug. I believe I collected wood bugs from these three families: Oniscidae, Porcellionidae and Armadillidiidae (pill bugs, which roll into a ball).
Students build and maintain a habitat that satisfies the needs of wood bugs:
A layer of damp sand will keep the environment moist. A piece of rotting wood provides shelter. Vegetables (they love potato) and partway rotted leaves for food. Keep the sand damp (but not soggy - it is easy to make it too wet). Sprinkle dry sand with dechlorinated water. Remove any food that becomes mouldy. Store the habitat in a cool area of the room.
Wood bugs are added to the habitat from the walk, previous experiments, or from a collection made by the teacher in advance.
Students continue to take care of their wood bugs. If there are no small holes or gaps around the lid, take it off periodically to make sure there is enough oxygen in the container. It is important that the rotting leaves do not grow mould - remove any that do. The habitat needs to be moist but not soggy. A habitat can be kept for just a week, or several weeks. If kept for several weeks, babies may be born in the habitat. Do not pick up the wood bugs with fingers as they are very delicate. Use a paintbrush if you need to move them around.
After a week or so, look for evidence of the wood bugs eating (food with nibbles out of it), excreting (brown spots of fecaes under the wood), growing (a shedded exoskeleton), having babies (new baby wood bugs; the eggs are too small to see with the naked eye).
When the habitat is ready to be dismantled (after a month or months if they are doing well in the classroom), they need to put back where they came from (assuming it is warm enough - spring and fall are when wood bugs are not hibernating, so the best time). Could be combined with a decomposer hunt activity.
Students use a paintbrush to flick the wood bugs from their habitat into a garden or sheltered spot.