Desert Spider Beetle: Your Quick Guide to These Fascinating Insects

The Desert Spider Beetle is an intriguing creature found in arid environments. This fascinating arthropod is part of the spider beetle family, which has several species known for infesting stored products. Although they share similarities with spiders, spider beetles primarily differ in their oval or cylindrical shape, long legs, and brown color ^(source)^.

These beetles have an array of characteristics that make them well-adapted for survival in their harsh habitats. For instance, their small size – ranging from two to five millimeters in length – enables them to navigate complex environments with ease. Additionally, they generally feed on organic debris and decaying matter, making it easier for them to find nourishment in their surroundings ^(source)^.

Desert Spider Beetle Overview

Family and Genera

Desert Spider Beetle belongs to the family Meloidae and the genus Cysteodemus. Their unique characteristics include:

  • Generally two to five mm long
  • Oval or cylindrical body shape
  • Long-legged and brown in color

Cysteodemus Armatus

Cysteodemus Armatus, also known as the Desert Spider Beetle, is a species native to arid regions. Some features of this species are:

  • Superficial resemblance to spiders
  • Active at night, hiding during the day
  • Attracted to lights
Feature Desert Spider Beetle Spider
Body Shape Oval or cylindrical Elongated
Legs Long and slender Long and hairy
Size 2 to 5 mm Larger than beetles

In summary, Desert Spider Beetles are small, yet fascinating insects native to arid environments. They have unique characteristics that set them apart from spiders and other beetle species.

Habitat and Distribution

California and Mojave National Preserve

The Desert Spider Beetle is found in California, USA, specifically in the Mojave National Preserve.

This region is known for its unique flora and fauna, making it an ideal habitat for the beetle.

Cinder Cones Area

In the Cinder Cones Area, these beetles thrive due to the presence of:

  • Volcanic rock
  • Sandy soil
  • Various plant species

These factors allow the Desert Spider Beetle to find shelter, food, and areas for reproduction.

San Bernardino County

San Bernardino County in California is another region where the Desert Spider Beetle can be found.

The county’s diverse range of ecosystems create suitable conditions for the beetle’s survival.

Comparison Table

Habitat Conditions Advantages for Desert Spider Beetle
Mojave National Preserve Arid desert & unique vegetation Diverse food sources & shelter
Cinder Cones Area Volcanic rock & sandy soil Ideal ground for egg-laying
San Bernardino County Various ecosystems Multiple options for habitat

Beetle Features

  • Adapted for desert environment
  • Carnivorous diet
  • Efficient reproduction

Beetle Characteristics

  • Well-camouflaged
  • Stealthy hunter
  • Resilient in harsh conditions

Physical Characteristics and Behavior

Size and Appearance

Desert Spider Beetles are small insects with their size ranging from 2 to 5 mm long. They are oval or cylindrical, long-legged, and brown in color. Their appearance is often likened to spiders, which earned them their name 1.

  • Size: 2-5 mm long
  • Shape: Oval or cylindrical
  • Color: Brown
  • Legs: Long

Inflated Beetle

The Inflated Beetle is another name given to desert spider beetles due to their distinct appearance. This refers to the swollen abdomen and spindly legs, giving them a unique appearance compared to other beetles.

  • Swollen abdomen
  • Spindly legs


Desert Spider Beetles are flightless, which means they rely on crawling for movement. This trait, along with their small size and spider-like appearance, makes them excel at navigating their arid and hostile habitats.

  • Movement: Crawling
  • Environment: Arid habitats

Life Cycle and Diet


Desert Spider Beetles start their life as eggs. They remain in their egg form for about 7 to 10 days before hatching into larvae1.

Larva and Cocoon

Once hatched, the larva go through a grub-like stage where they are white and fleshy2. As the larva mature, they form a cocoon3.

Feeding Habits

Desert Spider Beetles feed on various items:

  • Grains
  • Seeds
  • Dried fruits
  • Spices
  • Dead insects
  • Rodent droppings4

Comparison between the larval and adult stage in terms of diet5:

Stage Diet Preferences
Larva Grains, seeds, dried fruits
Adult Spices, dead insects, droppings

Bullets for key features:

  • Egg stage: 7 to 10 days
  • Larva stage: Grub-like, white and fleshy
  • Cocoon stage: Transforming into adults
  • Diet: Grains, seeds, dried fruits, spices, dead insects, rodent droppings

Impact on Humans and Environment

Infestation and Pests

Desert Spider Beetles can cause infestations, becoming pests in some environments. They are attracted to certain plant species, which they feed on, causing damage to crops and landscapes. Effective pest control methods for Desert Spider Beetles are essential to prevent extensive damage to plants and vegetation. Examples of such methods include:

  • Biological control: using natural predators to keep beetle populations in check
  • Pesticides: applying chemical treatments specifically targeting beetles
  • Cultural practices: ensuring proper plant care and maintenance to reduce beetle-attracting factors

Dangerous or Harmful?

If you’re wondering whether Desert Spider Beetles pose a direct threat to humans, the answer is: not really. Despite their intimidating appearance, these insects are generally harmless to humans and are not venomous or aggressive. However, it is important to treat them with caution, as any unfamiliar insect could potentially have unexpected defensive reactions. Here’s a quick comparison of Desert Spider Beetles and dangerous spider species:

Attribute Desert Spider Beetle Dangerous Spider
Venomous No Yes
Aggressive No Possibly
Damaging to plants Yes No

In summary, Desert Spider Beetles pose a minimal threat to humans and the environment, primarily impacting plants they infest. By using effective pest control methods, their populations can be managed, and their impact mitigated.

Prevention and Control Methods

Identification and Inspection

Identifying a desert spider beetle is crucial for effective prevention and control. They are usually two to five mm long, oval or cylindrical, long-legged and brown. To inspect for their presence, look for:

  • Small holes in wooden structures
  • Fine, powdery frass near suspected infested areas

Possible prevention methods include:

  • Sealing cracks and crevices: Close off entry points where pests can hide.
  • Sanitation: Regularly clean and declutter your living areas; remove stacks of newspapers, magazines, and cardboard.

Professional Pest Control Services

For a more comprehensive approach, consider hiring a pest control professional. Benefits of pest control services include:

  • Expert identification and inspection abilities
  • Access to specialized equipment and treatment methods
  • Offering long-term solutions and prevention guidance
  • Handling potentially harmful chemicals safely

However, there are some drawbacks:

  • Can be expensive
  • May require multiple visits
  • Potential exposure to chemicals

Comparison Table: DIY vs Pest Control Services

DIY Prevention & Control Pest Control Services
Cost-effective Can be expensive
Addresses minor infestations Effective for severe infestations
Requires self-education and time Expert knowledge and solutions

To conclude, preventing desert spider beetle infestations can be done through proper identification, inspection, and a mix of DIY methods or professional pest control services.

Resources and Further Information

BugGuide and Naturalists

BugGuide is an excellent online resource for identifying and learning more about spider beetles and other insects. It offers:

  • Detailed photographs and descriptions
  • Information on habitats and behaviors

Joining a local group of naturalists can also help you expand your knowledge about desert spider beetles and other fauna in your area. They often organize field trips, workshops, and presentations to share information and expertise.

Local Extension Office and Expert Advice

Your local extension office can provide you with invaluable resources for understanding desert spider beetles. They can:

  • Offer expert advice and assistance
  • Give you access to up-to-date research and information

Contacting expert professionals in entomology and related fields can provide you with additional insights into desert spider beetles and their characteristics. These experts may be able to answer specific questions and share their research findings.

Resource Pros Cons
BugGuide Easy-to-use online resource May not cover all species
Naturalists Local knowledge and hands-on experience Membership may be required
Local Extension Office Personalized advice and assistance Limited to region
Expert Professionals Access to exclusive knowledge and research May be difficult to contact

In summary, a combination of online resources, local groups, and professional advice can provide you with a wealth of information on desert spider beetles and help you expand your understanding of these fascinating creatures.


  1. Spider Beetle | Horticulture and Home Pest News 2





Reader Emails

Over the years, our website, has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Desert Spider Beetle


Desert Spider Beetle or Black Bladder-Bodied Meloid
June 20, 2010
I found some of these beetles in my garden and looked them up to see what they were. They are very pretty, however, I really need to know if they are going to do any damage to either my house our my plants. Thank you for your information.
Living in New Mexico
Central New Mexico

Desert Spider Beetle

Dear Denizen of New Mexico,
Your identification is correct.  this is a Desert Spider Beetle or Black Bladder Bodied Meloid, Cysteodemus wislizeni, which is profiled on BugGuide.  Adult Blister Beetles feed on plants, but we don’t know the preferred plant that this species prefers to feed upon.  The Sam Wells Entomology page does not indicate the food preferences.  We believe they probably feed on some desert annual species.  They will not harm your home.  Blister Beetles, of which the Desert Spider Beetle is one, are capable of causing a skin reaction if they are carelessly handled.

Letter 2 – Desert Spider Beetle


Location: Dripping Springs, New Mexico
April 17, 2012 1:34 pm
Sorry I couldn’t get a better photo of this vividly colored bug. It wouldn’t stop it’s frantic running.
Signature: Lynn

Desert Spider Beetle

Hi Lynn,
Desert Spider Beetles in the genus
Cysteodemus are also known as Inflated Beetles.  They are actually a genus of Blister Beetles, a curious family that has great diversity in the deserts of the southwest.  You may read more about Desert Spider Beetles on BugGuide.

Letter 3 – Desert Spider Beetle


I have found a yellow and black beetle in the desert
This is the only picture that i have of it.. the rest were all way to blurry as i was following it around with my camera trying to get a perfect shot..It is the first time I have ever seen anything like that.. I found it in the desert in 29 palms, ca. Oddly enough though after a few hours i spotted another one on the other side of the fence. it is a very pretty beetle.. and its very fast. Can you help me at all with identifing it?

he he he i have finally found it i looked for it through almost all the beetle pages… thanks tho!! maybe you can still feature the picture cause the clarity on it is amazing. how much detail my camera caught.. :] thanks

Hi Terra,
We are happy you located your Desert Spider Beetle, Cysteodemus armatus, also known as the Inflated Beetle, on our site without our help.

Letter 4 – Desert Spider Beetle


Can you tell what this bug is?
I found this colorful beetle in Phoenix, AZ outskirts in the desert. Do you know the species? Thanks.

This is definitely a Blister Beetle, and we are also certain it is the genus, Cysteodemus, the Desert Spider Beetles. One species is black and the other is white. The white species is the White Bladder-bodied Meloid, Cysteodemus armatus. We are perplexed by the yellow coloration and wonder if it is a variation, a chemical tinting, a pollen dusting, or a different species. We will inquire if Eric Eaton has an opinion.

Letter 5 – Desert Spider Beetle


Mystery SoCal Bug (not a jerusalem cricket!)
This is a shot I took back in March of 06. We found it on a herp trip to SoCal, it was in a canyon somewhere between Joshua Tree & the Salton Sea. It was about the size of a lima bean. I’m a biologist and I’ve never seen anything like it. It’s been bugging me for almost a year, help bugman! Cheers,
Brandon Fessler

Hey Brandon,
What a great photo of a Desert Spider Beetle in the genus Cysteodemus. This is probably Cysteodemus armatus which is found in California. Desert Spider Beetles are a group of Blister Beetles in the family Meloidae.

Letter 6 – Desert Spider Beetle


blue beetles in New Mexico
Hi bugman,
I just moved to Las Cruces NM from Australia. My husband, 6 week old puppy and I were walking in one of the local arroyos yesterday and we saw what we thought were jewels on the ground. Closer inspection revealed two beetles. One large and one small….roundish like a grape with brilliant iridescent blue spots on their backs. They moved very fast once we took an interest in them. As my husband held back the puppy I used his cell phone to attempt a picture. I am not use to his phone and the glare was pretty bad at that time of the afternoon so the photos were dismal..but this one sort of captures the larger beetle in flight from us. My husband has previously lived in this area for a number of years and has never come across these beetles. I have started a search through Google and your site (I am up to page 6 of the beetles) but as the 6 week old puppy keeps wanting attention I am a bit distracted from the task! I hope that you can help us with an identification.

Hi Kate,
Your photo is quite blurry, but we are nearly certain this is a type of Blister Beetle in the genus Cysteodemus known as the Desert Spider Beetles. There is one blurry photo on BugGuide that matches your image, and it is identified as Cysteodemus wislizeni.

Letter 7 – Desert Spider Beetle


Hello, What’s this bug?

A Desert Spider Beetle, Cysteodemus armatus.

Letter 8 – Desert Spider Beetle


Yellow and black bug
This was taken in the Mojave desert in SE CA (San Bernardino County) It was a fast moving bug about the size of a dime. I saw a similar bug in the desert of San Diego County but the insect was white in the place that this one is yellow. Both were crawling on the ground.

Hi Nancy,
This is a Desert Spider Beetle, a Blister Beetle in the genus Cysteodemus.

Letter 9 – Desert Spider Beetle


A Beetle Picture For You
Howdy! I was out and about some weeks ago and caught on camera this fabulous shiny beetle. I immediately tried finding out what it was, but to no avail, and soon gave up. Just now, however, I came upon your site again (I’ve come across it before but forgot about it) and saw a submission from Las Cruces, New Mexico that was the same kind of beetle, that now I know is a Desert Spider Beetle. My beetle was in El Paso, Texas, about a 45 minute drive from Las Cruces. Well, just wanted to share my picture and say thanks for helping me ID this guy (it was killing me not to know!) and that your site is great! Keep up the good work!  🙂

Desert Spider Beetle
Desert Spider Beetle

Hi Jen,
Your Desert Spider Beetle is a Blister Beetle in the genus Cysteodemus.  We are not certain of the exact species, but we are very happy our site assisted you in the identification.

Letter 10 – Desert Spider Beetle


Mottled yellow beetle, 1″ long with rounded body about the size of a nickle.
Thu, Apr 23, 2009 at 11:01 AM
This bug was moving very quickly across our cement patio to our bermuda grass lawn about 8:30 am, April 23, 2009. It has a very round back and head. It is mottled black with yellow, head is solid yellow; underbelly is shiny black. It appeared to be climbing stalks of grass, possibly nibbling on the ends; it tumbled off the stalks often, moving on to other pieces of grass. It moved almost too quickly to get a clear photo.
Lake Havasu City, Arizona

Inflated Beetle
Inflated Beetle

Hi Julia,
This is a Desert Spider Beetle or Inflated Beetle, Cysteodemus armatus, one of the Blister Beetles.  According to BugGuide, it is found in Arizona, Nevada and California.  Spring is the time of year we get the most Blister Beetle reports, and a relative, the Master Blister Beetle, is our Bug of the Month.

Letter 11 – Desert Spider Beetle


Anza Borrego Spider??
March 31, 2010
We were at Anza Boreggo this past Saturday (03-27-10), Spring Season. We were walking up one of the canyons, rocks. And I went to an area where there were some flowering cactus, and other wild flowers. As I was approaching a flower, I noticed what originally looked like a beetle! UNTIL, it started to move and put its two front legs on a flower!!! Then it looked like a spider! What kind of spider is this? It camouflages as a piece of an orchid flower leaf as well! The body was huge and bulbous!
Anza Borrego

Desert Spider Beetle

Hi Crystal,
Your photo is lacking the kind of detail that would make our identification easier, but we believe this is a Desert Spider Beetle, Cysteodemus armatus, which may be viewed on BugGuide.

Hi Daniel!
Thank you very much for your quick and very accurate response!  It most definitely looks like a Desert Spider Beetle!!!  So I was right to think it was a beetle; I got a little freaked out the moment it looked like a spider.  Sorry I didn’t get closer to it, as I’m afraid of those things jumping at me!  It actually prevented me from going to the flowering cactus that I wanted to take a picture of! 🙂  But now I know exactly what it is!  What a specimen! 🙂

Letter 12 – Desert Spider Beetle


Bug seen in Anza-Borrego
April 4, 2010
Dear Bugman,
We saw this guy crawling across the sand in Anza-Borrego State Park on March 21, 2010. Any ideas?
Madena and Charlie
Anza-Borrego State Park, California

Desert Spider Beetle

Dear Madena and Charlie,
Just last week, we posted another photo of the Desert Spider Beetle or Inflated Beetle, Cysteodemus armatus, and that specimen was also from Anza-Borrego.  Your photo has much crisper detail than the photo we posted earlier.  You can read more about this fascinating beetle on BugGuide.

Letter 13 – Desert Spider Beetle


found a beautiful bug, but can’t find it anywhere.
April 11, 2010
My husband and I were out off roading in Southern New Mexico today and came across this little guy running across the road. The bright metallic blue/green caught our eyes… He was a fast little booger, and really didn’t want his picture taken. We think it’s a beetle of some kind, but not sure.
Southern New Mexico

Desert Spider Beetle

Hi Cecilia,
We couldn’t help but to immediately read your letter because of the subject line.  This beauty is a Desert Spider Beetle or Black Bladder-Bodied Meloid, Cysteodemus wislizeni, one of the Blister Beetles.  According to BugGuide, it ranges from Texas to Arizona.

Desert Spider Beetle

Letter 14 – Desert Spider Beetle


Black Beetle with Yellow Spots
April 30, 2010
Hi! There is an interesting black beetle with yellow smudges scurrying all over the San Felipe Baja desert this Spring. They are super fast, very aggressive, they will chase after you if you get too close! They’re bigger than a quarter.
Baja Beetle girl
San Felipe, Baja California

Desert Spider Beetle

Hi Baja Beetle girl,
The Desert Spider Beetle or Inflated Beetle is a Blister Beetle in the genus Cysteodemus, and you may read up on them on bugGuide.  We believe it is Cysteodemus armatus which Bugguide describes as:  “Flightless; distinguished from all other meloid beetles by its inflated (air space below elytra may serve as insulation), spheroid, fused elytra. Elytra are coarsely pitted, and often covered with a white to yellowish secretion.

Desert Spider Beetle

OMG!!!!!  you are a genius!
Thank you Thank you Thank you!  That’s totally it!!!!
Kym S. Farmen – Master Herbalist, Photographer

Letter 15 – Desert Spider Beetle


wondering what this bug is
Location: 31deg54’42.99”N, 106deg27’20.90”W
November 29, 2010 12:05 pm
One of my favorite photos. Took this in Aug. 2006 just after a record rain and flood in the desert off the Franklin Mountains in El Paso, TX. The abdomen of what appears to be a type of ant was roughly 1/2” long.
I’ve always wondered if the heavy and unusual amount of rain affected this bug’s normal appearance.
Signature: Christopher Licking

Desert Spider Beetle

Hi Christoper,
This is a Desert Spider Beetle in the genus
Cysteodemus.  Some members of this genus are known as Inflated Beetles because of the air filled abdomen.  Your beetle is the Black Bladder-Bodied Meloid, Cysteodemus wislizeni, which you may read about on BugGuide.  Rain frequently triggers activity in desert dwelling insects.

Letter 16 – Desert Spider Beetle


arizona beetle
Location: Parker Arizona
April 4, 2011 2:13 pm
Hi i was taking pictures for my homework when i ran across this bug and i was wondering what it is?
Signature: Ernie

Desert Spider Beetle

Dear Ernie,
What kind of picture taking homework are you doing?  This amazing beetle is one of the Blister Beetles and it is known as a Desert Spider Beetle or Inflated Beetle.  Blister Beetles have complex life cycles with the larval stage undergoing radical metamorphosis, passing through stages where it is grub-like and stages where is it more mobile.  According to BugGuide:  “Larvae have been found in subterranean nests of solitary bees.”

Letter 17 – Desert Spider Beetle


Subject: Iridescent green/blue beetle in New Mexico?
Location: Albuquerque, New Mexico
September 3, 2013 4:51 pm
We saw these beetles in our yard recently. The only other one we have seen was found dead, two or three years ago. One was a hole dug by our dogs, gripping the vertical surface. It’s near what looks like a burrow. The other was seen a few days later, in the same general area, but out in the open. The beetles are iridescent green or blue, depending on the lighting. They are quite bulbous. These two were different sizes, but between 1/2” and 3/4” long. I haven’t been able to identify anything similar. Please help!
We are in Albuquerque, New Mexico, on a mesa of volcanic rock and find sand. We don’t have a lot of vegetation around us, either.
Thanks for your assistance.
Signature: Eric Jackson

5:03 PM
I kept searching and finally found it!  It’s clearly a Desert Spider Beetle (Cysteodemus wislizeni) according to pictures on your site.
Thanks for your great resource!

Desert Spider Beetle
Desert Spider Beetle

Hi Eric,
We are happy you managed to self-identify this Desert Spider Beetle, 
Cysteodemus wislizeni, despite our somewhat daunting archive.

Letter 18 – Desert Spider Beetle


Subject: weird metallic beetle new mexico
Location: new mexico usa
April 16, 2015 12:23 pm
I been seeing these beetles all over my yard and in my tree wells
Signature: seraphim

Desert Spider Beetle
Desert Spider Beetle

Dear Seraphim,
Though it is commonly called a Desert Spider Beetle, this member of the genus
Cysteodemus is a Blister Beetle.  We believe it is most likely Cysteodemus wislizeni which is found in New Mexico and Texas according to BugGuide.

Letter 19 – Desert Spider Beetle


Subject: Big Bend Bug
Location: Big Bend National Park, Texas
May 9, 2015 7:26 am
Just after photographing the April sunrise lighting up Santa Elena Canyon in Big Bend National Park, we saw the bug in the attached photo. It is very pretty, with iridescent green, blue, and lavender highlights. Can you please identify him for us?
Thank you
Signature: Richard Banke

Inflated Beetle
Inflated Beetle

Dear Richard,
This is a gorgeous image of a Desert SpiderBeetle in the genus
Cysteodemus.  Based on ranges indicated on BugGuide, this is most likely Cysteodemus wislizeni, sometimes called a Black Bodied Meloid.

Thank you for the quick response (and the nice compliment on the photo!).

Letter 20 – Desert Spider Beetle


Subject: Arizona bug
Location: Lake Havasu City, Arizona
March 7, 2016 4:50 pm
I work for a newspaper and a reader sent in a pic of this bug. What the heck is it??
Signature: Pam in Havasu

Desert Spider Beetle
Desert Spider Beetle

Dear Pam in Havasu,
This incredible insect is a Desert Spider Beetle or Inflated Beetle,
Cysteodemus armatus,  a Blister Beetle species that is limited to the Colorado and Mojave Deserts in the states of California, Nevada and Arizona.  According to BugGuide:  “Recorded food plants of adults: most commonly Larrea tridentata, but also a number of other plants (Acamptopappus sphaerocephalus, Chaenactis, Geraea canescens, Palafoxia arida, Gilia, Loeseliastrum matthewsii, Tiquilia). While creosote leaves are dependable even in the driest of years, other plants are likely preferred when available.”

Letter 21 – Desert Spider Beetle


Subject: Desert Beetle?
Location: Desert between Nevada and California
March 29, 2016 11:11 am
Can you help me identify this bug please? It’s been driving me nuts! 🙂 It looks like a beetle for sure (to me, anyway) because it had a hard shell. It was about the size of a dime. Found in the desert of Zzyzx, CA (the Desert Science Center), it was a dark gray with a white spot on the head and long black legs.
Signature: Lara

Desert Spider Beetle
Desert Spider Beetle

Dear Lara,
This is a Desert Spider Beetle or Inflated Beetle in the genus
Cysteodemus.  According to BugGuide, Cysteodemus armatus has “white to yellow-brown incrustation” which tends to vary from individual to individual, which explains the white head in your image.

Letter 22 – Desert Spider Beetle


Subject:  California Spring Beetle
Geographic location of the bug:  California, desert
Date: 04/14/2019
Time: 09:23 PM EDT
Your letter to the bugman:  Hello! I have found a beetle in the desert munching on a normal grass weed. I tried to search online for beetles native to california, but have not found anything like it. Is it foreign? Or diseased? Thank you for helping me identify this beetle, I am so curious to find what it is!
How you want your letter signed:  Mimi

Desert Spider Beetle

Dear Mimi,
Spring vegetation growth in the arid deserts of California, Arizona and Nevada bring out the diversity in the Blister Beetle family Meloidae.  This Desert Spider Beetle is in the genus

Letter 23 – Desert Spider Beetle


Subject:  Photos of Desert Spider Beetle
Geographic location of the bug:  Albuquerque New Mexico
Date: 06/13/2019
Time: 10:58 AM EDT
Your letter to the bugman:  Just wanted to share these good images of the Desert Spider Beetle.
How you want your letter signed:  Chris Krupar

Desert Spider Beetle

Dear Chris,
Thanks for submitting your images of a Desert Spider Beetle.  According to BugGuide, the species found in New Mexico is
Cysteodemus wislizeni.

Desert Spider Beetle


Letter 24 – Desert Spider Beetle or Inflated Beetle


Whats that bug?
Thu, Apr 9, 2009 at 1:41 PM
Please identify and/or help me identify the insect in the attached image? I’m thinking some sort of beetle?
what are my options?
mecca ca

Inflated Beetle
Inflated Beetle

Hi Gus,
This is a Desert Spider Beetle in the genus Cysteodemus.  We would further identify it as an Inflated Beetle, Cysteodemus armatus.  This species is found in California, Arizona and Nevada in the Mojave and Colorado Deserts.  You can see more images and read about the fascinating life cycle on BugGuide which indicates the “Larvae have been found in subterranean nests of solitary bees.”  The Inflated Beetle is a Blister Beetle that gets its common name because of the air space under the fused elytra or wing covers.  This air space is thought to act as insulation in the cold desert nights.

Letter 25 – Inflated Beetle


Subject:  What’s this beetle?
Geographic location of the bug:  Portland Oregon, sandy riverbank
Date: 04/27/2019
Time: 06:49 PM EDT
Your letter to the bugman:  This cute little fellow got us all wondering what species he might be. He was spotted on the bank of the Willamette river near the forest’s edge in April. Any idea? Thanks so much for any insight you might have!
How you want your letter signed:  Beetle Bystander

Inflated Beetle

Dear Beetle Bystander,
This is a Desert Spider Beetle or Inflated Beetle in the genus
Cysteodemus.  According to BugGuide, there are two species in North America and neither is reported from Oregon, and the range is listed as “sw. US: Colorado, Mojave, and Chihuahuan deserts.”  We are not certain how unusual this Oregon sighting is.

Letter 26 – Inflated Beetle


Subject:  Found beetle
Geographic location of the bug:  Golden Shores AZ
Date: 03/28/2020
Time: 12:39 AM EDT
Your letter to the bugman:  I’d like to know what kind of beetle this is
How you want your letter signed:  Please and thank you

Inflated Beetle

We have identified your beetle, Cysteodemus armatus, on BugGuide.  It is commonly called a Desert Spider Beetle or an Inflated Beetle.


  • Bugman

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5 thoughts on “Desert Spider Beetle: Your Quick Guide to These Fascinating Insects”

  1. I saw one just like this in Parker, Arizona around April 24th 2011. It was moving really fast so all I have a blurry pics, but it looked just like that – same Fluorescent like Yellow and Jet blackness.

    So, Thank you for your post and picture!! It was most helpful!

    I wonder if they are still perplexed or if they have figured out why it’s yellow and now white, like they thought it should be.

    Once again – Thank you!! 🙂

  2. We have one in our collection (forestry research center) that is black but partially ‘dirty’ with a brownish yellow dried grainy substance that does look like pollen or even mixed with bits of sand- we are officially calling it crud- it seems to be caught in its honeycomb-like texture.

    • BugGuide refers to a “white to yellow-brown incrustation” on Cysteodemus armatus, which is information we did not have in 2006 when this posting originally went live on our site.


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