There are dozens of North American insect species that can wander into your house and gradually make it their home. While many types of small, brown bugs are harmless, merely seeking warmth or shelter in your home, there are some that aren't so innocent. Bed bugs, for example, spread quickly and embed themselves in the fabric of blankets and mattresses. When you notice a single bug or insect running around your house, it does not necessarily mean there are more. However, if you notice several of the same type of bug in a short time, you should catch one and identify it.
Look for bugs if you see one around in your house. Stay alert and check every room in your house throughout the day. Look for them at night before you go to sleep with a flashlight, as some species are purely nocturnal or may run if you turn on the room light. Look at the paths they travel if there is any pattern -- some bugs, like the house centipede (Scutigera coleoptrata), leave scent trails to guide others of their kind.
Trap one of the brown bugs in glass or plastic jar or another small container. Place the opening on top of the insect and slide a thin sheet of paper under the jar and the bug. Be careful not to pinch off any of the bugs legs, keep the jar pressed against the floor until the paper is all the way across. Seal the container. Use cling film if there is no real lid.
Hold a magnifying glass to the insect and move the jar around to examine every part. Count the number of leg pairs. Look for damaged or lost legs, many insects can run just as well with missing legs. Arachnids always have eight legs and most beetles, have six. Myriapods, the classification that includes centipedes and millipedes, can have over a dozen pairs of legs -- one for each abdominal section.
Estimate the size of the insect by holding a ruler to the jar. Insects, even those that are closely related, can vary drastically in size. The American cockroach (Periplaneta americana) is 1 1/2 inches when it reaches adulthood, but its German cockroach cousin (Blattella germanica) barely exceeds 1/2 inch in length. Common household bugs can be even smaller -- the black carpet beetle (Attagenus unicolor) is only a 1/4 to 1/2 inch long.
Examine the insect's head and body, look for distinct separations between sections---particularly between the abdomen, thorax and head. Some parasitic insects, including fleas and ticks, have very tiny heads that connect almost seamlessly to an oversized abdomen.
Note the details of any colour or texture patterns on the insect's exoskeleton. The western conifer seed bug (Leptoglossus occidentalis) is an annoying pest that bears a unique black and brown pattern on its shell. The brown marmorated stink bug (Halyomorpha halys) is a relatively new, patterned pest in the United States as of 2010. It has distinct, arrow-shaped black markings on its oddly shaped exoskeleton.
Compare the insect's features, dimensions and unique traits to databases online. The website "Pest Control Canada" is one of the many informative sites with a database of pictures and user-generated content to help users match and identify insects. The website "Discover Life" offers a trait-oriented insect identification search that narrows the search to a specific Order and then further to identify the individual species. Once you identify your bug, check information from several additional sources to confirm your findings. Use a variety of sources to identify your bug. Some sites are primarily user generated and may contain some factual errors. Also, match as many traits as you can. Some insect genera have hundreds of individual species that appear almost the same.