Spider beetles are small, oval, or cylindrical insects that can be found in both residential and commercial settings.
With their long legs and brown color, they can be mistaken for spiders, hence their name.
However, it’s essential to understand if these critters pose any danger to humans or their environment.
Their lifecycle consists of scavenging for food during both the adult and larval stages, making them an annoyance in various settings.
While not necessarily dangerous, it is essential to consider their potential impact on various aspects of our lives.
By learning more about their behavior and distinguishing factors, we can better understand how to prevent and manage any potential problems they may cause.
Identifying Spider Beetles
Physical Appearance
Spider beetles are small insects measuring around 2-5mm in length, with an oval or cylindrical body shape.
They possess long legs and are typically brown in color. Their physical traits include:
- White, fleshy grub-like larvae
- Long-legged and brown in color
- Oval or cylindrical body shape
Spider beetles have a superficial resemblance to spiders, which is where their common name comes from.
Types of Spider Beetles
There are different species of spider beetles, but three common types found in the United States include:
- American spider beetle
- Whitemarked spider beetle
- Smooth spider beetle
Each species may have slightly different physical characteristics, but all share a resemblance to spiders.
Arachnids vs. Insects
While spider beetles look like spiders, it’s important to note that they are insects, not arachnids.
Here’s a comparison table to help differentiate between the two:
| Feature | Insects (Spider Beetles) | Arachnids (Spiders) |
|---|---|---|
| Number of Legs | 6 | 8 |
| Wings | Sometimes | None |
| Body Segments | 3 | 2 |
| Number of Eyes | Variable | Variable |
Are Spider Beetles Dangerous?
Spider Beetle Bites
Spider beetles are generally not known to be dangerous to humans.
They are small insects, typically measuring between 2-5 mm long.
These beetles are scavengers but do not have a biting habit1. Therefore, the risk of being bitten by a spider beetle is quite low.
Symptoms of a Bite
In the rare case that a spider beetle does bite, the symptoms may be similar to bites from other insects. Some possible symptoms include:
- Redness
- Swelling
- Pain
- Itching
It is important to note that these symptoms could also be caused by other insects, not just spider beetles.
In any case, it’s best to consult a medical professional if any bite symptoms persist or become severe.
Venom Risks
Spider beetles do not possess venom and are not considered a venomous insect.
The risk of experiencing venom-related symptoms as a result of a spider beetle encounter is non-existent.
However, venomous spiders do exist and can cause symptoms such as2:
- Nausea
- Fever
- Chills
- Body aches
- Severe pain
| Spider Beetle | Venomous Spider |
|---|---|
| Non-venomous | Venomous |
| No serious risks | Potential health risks |
In conclusion, spider beetles are not dangerous to humans. They do not have a habit of biting and do not possess venom.
Spider Beetle Infestations
Where They Nest
Spider beetles are known to nest in various places, particularly in dark and undisturbed areas. Some common nesting sites include:
- Attics: These pests often find shelter in the insulation or stored items.
- Storage areas: Boxes, old furniture, and piles of clothes can attract spider beetles.
- Pantry: They may also infest food storage areas, seeking out cereals, dried fruits, and other dry goods.
Feeding Habits
Spider beetles are scavengers, consuming a variety of organic materials. They typically feed on:
- Cereals and seeds
- Dried fruits
- Dead insects
- Rodent droppings
- Old wood (for some species)
These pests require moisture to survive, so they are often found in damp environments.
Signs of an Infestation
Detecting a spider beetle infestation can be challenging. However, some key indicators can help you identify their presence:
- Damaged packaging: Spider beetles can chew through food packaging, leaving small holes and exposing the contents.
- Frass: The presence of beetle droppings and debris from their feeding activities may indicate an infestation.
- Sightings: Spotting adult beetles or their white, grub-like larvae can be a clear sign of infestation.
By identifying where spider beetles nest and understanding their feeding habits, it is easier to notice the signs of an infestation and take appropriate action to prevent further damage.
Preventing and Controlling Spider Beetles
Inspection and Identification
Before applying any prevention or control methods, it is crucial to inspect your home and identify spider beetles.
Look for them in moist places, such as basements, and pay attention to food storage areas.
These beetles are small, brown, oval-shaped, and resemble spiders in appearance. The identification of spider beetles is necessary to apply targeted treatments.
Some signs of infestation include:
- Small holes in stored products
- Presence of larvae and cocoons in crevices and cracks
- Beetle sightings in moist areas, especially around food
Cleaning and Storage Tips
Preventing spider beetle infestations involves maintaining a clean environment, particularly in your food storage areas.
Follow these tips to keep your home beetle-free:
- Regularly vacuum pantries, shelves, and cracks
- Store food in airtight containers or the refrigerator
- Clean up spills and crumbs immediately
- Discard old or infested products
- Install tight-fitting screens and seal cracks to prevent entry
Chemical and Non-Chemical Treatments
There are various treatments available for controlling spider beetles, both chemical and non-chemical:
| Treatment Type | Pros | Cons |
|---|---|---|
| Insecticides | Effective in targeting pest populations | Can be harmful to humans and pets, not environmentally friendly |
| Vacuuming | Non-toxic and quick | Can miss some small, hidden insects |
| Diatomaceous Earth | Harmless to humans and pets, eco-friendly | Can be slow-acting |
Use insecticides as a last resort, especially in food storage areas, and opt for safer alternatives like vacuuming or diatomaceous earth.
Consider consulting a pest control expert for more guidance on controlling spider beetles in your home.
Effects on Pets and Natural Environment
Pet Food Issues
Spider beetles are known to infest stored products, which can include items such as pet food. Specifically, they may contaminate items such as:
- Dry kibble
- Birdseed
- Rodent food
As scavengers, spider beetles can spread germs and bacteria as they move from one food source to another.
While they are not directly harmful to pets, their presence within pet food can pose health risks to animals.
Role in Ecosystem
Spider beetles can be considered natural decomposers, breaking down organic material in the ecosystem.
They are not limited to infesting people’s homes, as they can also be found in places like:
- Gardens
- Ecosystems with decaying plant matter
- Areas near rodent nests
Though their scavenging habits have some benefits, spider beetles can also damage certain plants and other items, such as spices.
In the natural environment, their presence may be helpful or harmful, depending mostly on the specifics of their surroundings.
| Feature | Beneficial | Harmful |
|---|---|---|
| Decomposition | Breaking down plant material | Damaging spices and veggies |
| Scavenging | Keeps ecosystems clean | Contaminates pet food and human food |
| Feeding on rodents | May help limit rodent populations | Can contribute to spreading diseases |
To detect their presence, using a flashlight in the dark may reveal hiding spider beetles.
Identifying them early and addressing the infestation can help mitigate negative consequences to pets, food, and the environment.
Keep in mind that while spider beetles pose some risks, they are not considered severe pests in most cases.
Footnotes
Conclusion
Spider beetles are small insects that resemble spiders, but they are actually members of the beetle family.
They are not dangerous to humans or pets, but they can be a nuisance if they infest stored food or organic materials.
Spider beetles can be prevented by keeping food in sealed containers, cleaning up spills and crumbs, and inspecting items before bringing them indoors.
Spider beetles are harmless impostors that can be easily controlled with proper sanitation and pest management.
Reader Emails
Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these spider beetles. Scroll down to have a look at some of them.
Letter 1 – Smooth Spider Beetle
Subject: Should I be concerned?
Location: Boston, MA
April 16, 2017 6:34 pm
Hello,
I’ve found a few of these bugs in my apartment over the last couple weeks, mostly in the bathroom but occasionally in other rooms too. I have an infant son and I’m worried that these could be ticks, but they don’t quite look like most of the tick pictures I’ve seen online.
Do you have any idea what it is?
Signature: Thank you!
This is one of the Spider Beetles in the subfamily Ptininae, most likely the Smooth Spider Beetle, Gibbium aequinoctiale, which is pictured on BugGuide where it states:
“Cosmopolitan but more common in warm climes, and very few records in Europe; origin unknown (“tropical, subtropical”); found in stored goods across NA” and that it feeds on a “wide variety of dead organic materials; may be a dry stored product pest.”
Check the pantry for the site of the infestation, including large, bargain bags of pet food and bird seed.
Letter 2 – Shiny Spider Beetle
Subject: What Bug is this?
Geographic location of the bug: Westchester, New York, USA
Date: 01/28/2018
Time: 05:32 PM EDT
Your letter to the bugman: Hi There,
I was hoping you could help identify this. My sister works in a historic house. These bugs were found living in the rolled up carpets in the house.
They did not seem to be eating the carpet. They were found last week and they are a little bigger than a deer tick.
How you want your letter signed: AL
Dear Al,
This is a Spider Beetle in the genus Mezium, probably the Shiny Spider Beetle which is pictured on BugGuide. According to BugGuide, Spider Beetles feed on “dry stored products.” Though they generally infest stored foods, they might also feed on organic fibers in carpets.
Letter 3 – Smooth Spider Beetle
What kind of bug is this?
Location: Manayunk, Philadelphia, PA
April 5, 2012 5:05 pm
Found it crawling on a sweater I discarded on the floor after a night of drinking. I could have picked up the bug at any of these places:
-dry cleaners (where the sweater came from)
-a drinking establishment
-my couch
-my bedroom floor
Please advise!
Signature: Resident of the City of Buggerly Love
Dear Resident,
As much as we are amused that you may have picked up this Smooth Spider Beetle, Gibbium aequinoctiale, in a drinking establishment, we would put money on your couch or your bedroom floor.
Spider Beetles are known to infest stored foods in the pantry, and you may want to check any food that has been unused for past the expiration date to see if it is contaminated. The BugGuide may have additional useful information for you.
Letter 4 – Smooth Spider Beetle
Almost cute
Location: Queens, NY
January 6, 2011 10:29 pm
Not sure what it was, but it sure wasn’t in a hurry. Spent most of it’s time stuck in a puddle on my bathroom sink. It was about 1-1.5mm long. (color is correct, yes my bathroom sink is that ugly pistachio color). Sorry for blurry pictures, reverse mounting a lens is not great for handheld shooting.
Signature: Ian
Dear Ian,
Try as we might, we are unable to determine why you consider your fine photographs to be blurry. This is a Smooth Spider Beetle, Gibbium aequinoctiale, and it is a common household intruder that feeds upon stored flour products in the pantry.
If you find more individuals, you may want to inspect the old cookies on the back shelf or the crumbs under the cushions of the couch. See BugGuide for additional information.
Letter 5 – Smooth Spider Beetle
Subject: Found some bugs near our dogs bed…help?!?
Location: Northern Virginia/DC
February 4, 2015 10:19 pm
Found about 10 of these guys on the floor near the dog bed. None on the dog, some were dead. Easily visible with the naked eye, medium brown color, and looked like 6 legs with a set of feelers. Teardrop shaped body. Don’t appear to be blood filled. Please help!
Signature: Bugging out in Virginia
Dear Bugging out in Virginia,
This is a Smooth Spider Beetle, Gibbium aequinoctiale, a common household pest that infests stored foods. According to BugGuide, they are found: “Mainly houses, flour mills, occasionally warehouses, hospitals, stores” and they feed upon a “wide variety of dead organic materials; may be a dry stored product pest.”
Do you buy bargain bags of dog food? Was there a bag of dog food near the dog’s bed? You may want to check the bag for the source of the infestation.
Letter 6 – Smooth Spider Beetle
Subject: is this a bed bug?
Location: Richmond VA
February 17, 2017 11:08 am
This found in bed with others. None of the characteristic flat bed bugs were found. It’s tiny- only a few millimeters. I took the photo using a stereomicroscope.
Signature: Bugging out
Dear Bugging Out,
This is NOT a Bed Bug. It is a Smooth Spider Beetle, Gibbium aequinoctiale, and we verified its identity on BugGuide. According to BugGuide: “wide variety of dead organic materials; may be a dry stored product pest.” They are relatively common household pantry pests.
Letter 7 – Smooth Spider Beetle
Subject: What is that
Geographic location of the bug: 11214
Date: 12/22/2018
Time: 08:21 PM EDT
Your letter to the bugman: the mm ruler is on the left
How you want your letter signed: Alex
Dear Alex,
This is a Spider Beetle, a common Household Pest that will infest stored foods. We are confident it is a Smooth Spider Beetle, Gibbium aequinoctiale, which is picture on BugGuide where it states the habitat is
“Mainly houses, flour mills, occasionally warehouses, hospitals, stores” and food includes “wide variety of dead organic materials; may be a dry stored product pest.”
Thank you very much for your help – it was done perfectly
Alex
Letter 8 – Spider Beetle
Help with this one
I know my bug isn’t glamorous like a Luna Moth but I am really concerned about this thing and if somehow, not seeing any for 3 years, it has followed me from Chicago to New York.
I sent a message a little over a week ago with a pic that wasn’t that clear. Hopefully these are better. He is pretty small so it is tough to get a good close up focus.
This is a Mezium Spider Beetle. They are pests in stored grain products.
Expert Update: (05/22/2008) spider beetle errors
Dear Bugman,
I believe I had written earlier when looking at many of the spider beetle pictures. Almost all of the shiny brown, globular body, images are of Gibbium aequinoctiale and not Mezium species. There is a combined 2 image photo (finger and beetle & 2 beetles) of Mezium : the answer was posted by Eric Eaton, I believe.
Gibbium species do not have a velvety covering on the thorax, Mezium species do. You should correct your website postings so people will have a better idea of what they have been finding. Best regards,
Lou
Louis N. Sorkin, B.C.E.
Entomology Section
Division of Invertebrate Zoology
American Museum of Natural History
New York
Dear Lou,
Thanks so much for resending this vital correction to our website. We really appreciate your expertise on this. We sincerely hope that addressing you with such familiarity doesn’t detract from your professional status.
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These do to dogs or a human
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