About this guide
This guide was created to provide information about some common, but still unfamiliar, insects and spiders spotted in homes across Oregon. There are over 20,000 species of insects in Oregon, therefore this is not a complete guide.
The list of common household pests in Oregon is intended to help residents make informed decisions about pest control services. We hope to reduce some of the unfounded fears and misconceptions about insects and spiders.
A note about insects and spiders
Insects and spiders have a bad reputation for being dangerous, deadly, destructive, or disgusting. This is an unfair characterization of the largest group of organisms on the planet. Of the more than one million known insects, only a very small percentage of these are considered “pests”, or species that cause problems for people.
There are more myths about the threat of insects and spiders than can fit into this pamphlet, but you should know: most insects and spiders are completely harmless to people. Insects enter homes looking for food (often in the form of other insects or food crumbs), for shelter, or completely by accident. Some insects are capable of causing very severe economic damage to crops and structures, and others can spread disease, but most insects and spiders are not problematic in any way.
If you find an insect that might be a pest, it’s essential to know what it is before hiring exterminators or applying pesticides.
Here are 9 common household pests in Oregon
Hobo Spider – Eratigena agrestis
Notes: Introduced from Europe. Common in houses and basements. Usually seen when males search for females in late summers are fall. House spiders and hobo spiders look very similar. Hobo spider bodies range from 8-14mm, whereas giant house spiders have bodies as large as 18mm. Much misinformation has been spread about the danger of these species to people. Studies of spider bites by OHSU found little or no evidence of harmful venom. Neither species is considered harmful.
Pest Status: None. These species pose little or no risk to people. Bites are possible but very unlikely.
Management: None. If spiders are found in homes, look for points of entry such as gaps under doors in garages or basements, or unscreened windows.
Multicolored Ladybird Beetle – Harmonia axyridis
Notes: Introduced in the US in the early 1900s to feed on aphids. Often distinctive “M” behind head, wing covers variable.
Pest Status: Often invades homes in early fall to overwinter. Also considered a contaminant in winegrape harvest.
Management: Pesticide applications are not recommended. Exclusion via sealing of entry points (windows, doors, and vents) is currently the best recommendation. Crushing or vacuuming can lead to surface stains and unpleasant odor.
Western Box Elder Bug – Boisea rubrolineata
Notes: Native to western North America.
Pest Status: Nuisance pest. Adults and nymphs feed on seeds of maple trees, but do not cause damage to tree. Populations get very large in spring and summer, but infestations are relatively short.
Management: Pesticide applications are not recommended, as populations are widespread. Exclusion via sealing of entry points (windows, doors) is recommended.
Brown Marmorated Stink Bug – Halyomorpha halys
Notes: First detected in US in 1996, Oregon in 2004.
Pest Status: Severe invasive crop and urban nuisance pest.
Management: Research is ongoing but some pesticides have been shown to be effective in crop systems. For homeowners, exclusion via sealing of entry points (windows, doors) is recommended. Research into the introduction of natural enemies is in progress.
Tuxedo bug – Raglius alboacuminatus
Notes: First detected in Oregon in 2002. Feed on seeds of weedy plants.
Pest Status: Nuisance pest. Large populations invade homes in late summer and fall. Can produce a foul smell when crushed.
Management: Pesticide applications are not recommended. Exclusion via sealing of entry points (windows, doors, and vents) is currently the best recommendation.
Bed Bug – Cimex lectularius
Notes: C. lectularius feeds on human blood. Bed bugs have become a problem recently presumably due to developing resistance to commonly used pesticides.
Pest Status: Usually feed at night and are found in mattresses or furniture. Do not transmit disease.
Management: Difficult. Professional management is recommended, and repeated efforts may be necessary.
Elm Seed Bug – Arocatus melanocephalus
Notes: First detected in Oregon in 2012, and are known from southern and eastern Oregon and the Portland area.
Pest Status: Nuisance pest. Adults and nymphs feed on elm seeds and do not cause plant damage. Home infestations can be large in midsummer.
Management: Pesticide applications are not recommended. Exclusion via sealing of entry points (windows, doors and vents) is currently the best recommendation
Garden cross spider – Araneus diadematus
Notes: Common outside homes in Oregon. Introduced from Europe. They become very noticeable as adults in the late summer and fall. Size can vary from the pinhead sized spiderlings to mature females that have bodies half an inch long.
Pest Status: None.
Management: None. This species is very docile, non-aggressive, and poses little to no risk to people. Bites are possible but very unlikely.
Indianmeal moth – Plodia interpunctella
Notes: Indianmeal moth larvae feed on stored products such as grain products, cereals, dog food and other dried food products. They are very commonly in households and grocery stores. They are found worldwide.
Pest Status: Larvae damage food products by feeding, spinning silk cocoons, and leaving behind fecal matter and pupal cases.
Management: Keep containers of food tightly sealed, especially bagged products. Traps for adult moths are available.
The Oregon Department of Agriculture provides free insect identification for members of the public and for agriculture industry professionals. In many cases, no action is necessary because the insect is not a pest. There may be solutions besides pesticides that can help reduce insect populations. However, not every insect pest problem has a simple solution. In many cases, control methods are difficult, costly, or simply unknown.