Darkling Beetle: All You Need to Know for Easy Identification and Fun Facts

Darkling beetles are fascinating insects that can be found in various habitats across the globe. These beetles are primarily known for their completely black color and unique defensive strategies, which they often employ to protect themselves from predators. Depending on the species, the shell of their abdomen can be either smooth or textured with ridges or bumps, making them an intriguing group of insects to study and observe.

One key characteristic of darkling beetles is their size, with some adults reaching up to 1.5 inches (3.8 cm) in length. These nocturnal scavengers feed on several types of “dead” materials like clothing, rugs, stored foods, and rotting wood, as well as fungi UWM Field Station. As their importance extends beyond their role in breaking down dead materials, darkling beetles also serve as a vital food source for many insect and animal species.

Darkling Beetles’ features:

  • Completely black in color
  • Smooth or textured abdomen
  • Scavengers on dead organic material
  • Can grow up to 1.5 inches

Overview of Darkling Beetles

Defining Features

Darkling beetles, as the name implies, are typically black or brown in color. These insects can have varying shell textures with ridges or bumps, depending on the species1. Some defining features include:

  • Black or brown coloration
  • Shell textures with ridges or bumps
  • Adult sizes up to 1.5 inches (3.8 cm) in length1

These beetles are known to walk with their heads down, making them easily identifiable1.

Tenebrionidae Family

Darkling beetles belong to the Tenebrionidae family, which is a very large and diverse group2. These beetles are commonly found in North America, with about 1,200 species identified3. They are generally small-to-medium-sized, slow-moving insects3.

The Tenebrionidae family is known for its nocturnal scavenger behavior, feeding on “dead” material like clothing, rugs, stored food, and rotting wood3.

Coleoptera Order

Darkling beetles are part of the Coleoptera order, which is the largest group of insects with one in four named insects being a beetle4. Key characteristics of the Coleoptera order are:

  • Biting and chewing mouthparts
  • Two pairs of wings; first pair being hard or leathery^[4^]

The first pair of wings, also called elytra, are not used in flight, but offer protection for the beetle’s body4.

Life Cycle and Reproduction

Larvae

Darkling beetles begin their life as eggs. When they hatch, they turn into grub-like larvae called mealworms. These larvae are initially white but turn tan as they age. They undergo several molts as they grow.

Pupation

After reaching their final larval stage, darkling beetles enter the pupation phase. During this period, they transform into pupae, an inactive stage similar to cocoons in moths and chrysalises in butterflies1.

Metamorphosis

The metamorphosis process in darkling beetles is known as complete metamorphosis. It involves four distinct body forms: egg, larva, pupa, and adult. Typically, a beetle remains as an egg for 7 to 10 days before moving on to the larval stage2.

Adults

Once the pupation stage is complete, the sexually mature adult darkling beetle finally emerges3. Adult beetles are known for their black color, and their abdomen shells can be smooth or textured with ridges or bumps, depending on the species4.

Darkling beetle comparison table:

Stage Description
Egg Initial stage; hatch into grub-like larvae
Larva (Mealworm) Grub-like appearance; molt several times as they grow
Pupa Inactive stage; similar to cocoon in moths or chrysalis in butterflies
Adult Mature, reproductive stage; completely black in color5

In summary, the life cycle and reproduction of darkling beetles involve:

  • Egg hatching into larvae (mealworms)
  • Larval growth and molting
  • Pupation and inactivity
  • Metamorphosis through four life stages
  • Emergence of mature adult beetles

Behavior and Habits

Natural Habitat

Darkling beetles are commonly found in the Columbia Basin and other areas of North America, primarily in the West. They thrive in environments with access to:

  • Dead plant or animal matter
  • Rotting wood
  • Fungi

Typical Diet

These little insects are omnivores and eat a variety of things:

  • Decaying plant matter
  • Fungi
  • Insect larvae
  • Dead animals

Adaptations and Defense Mechanisms

Darkling beetles possess remarkable defensive strategies:

  • Playing dead
  • Using chemical defenses

Their antennae are essential for detecting food sources and potential threats.

Temperature and Climate Impact

Temperature changes can affect darkling beetles’ behavior, distribution, and survival. A comparison table to illustrate the impact of different temperatures:

Temperature Impact on Darkling Beetles
Cold Slower movement, reduced activity
Warm Increased activity and reproduction

In conclusion, darkling beetles are fascinating creatures with unique behaviors and adaptations, thriving in various North American habitats. Their diet primarily consists of dead or decaying matter, and they possess notable defense mechanisms to evade predators. Temperature and climate play a role in their distribution and activities.

Darkling Beetle Infestations

Causes and Signs

Darkling beetles are nocturnal scavengers that feed on plant matter, pet food, and debris. They can cause damage to plants and stored products. Common causes of infestations include:

  • An abundance of their preferred food sources
  • Damp conditions or moist areas
  • Weeds and dirt clods providing suitable hiding places

Signs of an infestation include the presence of adult beetles, their larvae (mealworms and superworms), or wireworms. You may also notice damage to plants, textiles, or stored foods.

Prevention and Control

To prevent and control darkling beetles, follow these steps:

  1. Remove food sources: Keep pet food in sealed containers and clean up any spills promptly. Regularly remove dead plant matter and debris.
  2. Eliminate hiding places: Clear weeds and remove stones, dirt clods, and any other possible hiding spots.
  3. Monitor and trap: Set up sticky traps or pitfall traps to capture and monitor beetle populations.
  4. Apply insecticides: In severe infestations, consider using insecticides, but note that some darkling beetles can develop resistance.

Pros of using insecticides:

  • Can provide rapid control of infestations
  • Can target specific pests

Cons of using insecticides:

  • May cause harm to non-target species
  • Overuse can lead to resistance

Natural Predators and Enemies

Some natural predators and enemies can help control darkling beetles:

  • Ground beetles: Predatory beetles that prey on various soil-dwelling pests, including darkling beetle larvae
  • Birds: Many bird species feed on beetles and their larvae
  • Reptiles and amphibians: Lizards, frogs, and other small creatures can prey on darkling beetles and their larvae
  • Nematodes: Microscopic roundworms that can parasitize darkling beetle larvae

By promoting these natural predators in your garden or property, you can reduce darkling beetle populations without resorting to chemical insecticides.

Footnotes

  1. U.S. National Park Service 2 3 4

  2. Missouri Department of Conservation 2

  3. Field Station 2 3 4

  4. PNNL: Science & Engineering 2 3

  5. Darkling Beetles

Reader Emails

Over the years, our website, whatsthatbug.com 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 – Stink Beetle

 

What Type of Beetle is this
Thu, Apr 30, 2009 at 8:42 AM
This was found on my back decl in Northern Nevada a couple days ago. It has a hard body and looks like it walks high. The deck is open air but has a sun cover over it to block the sun and the bug was under the shaded part
Lisa
Yerrington, Nevada USA

Acrobat Beetle
Stink Beetle or Acrobat Beetle

Hi Lisa,
This lumbering beetle is a Darkling Beetle in the genus Eleodes.  There are numerous species in the genus found in arid regions of the Southwest, and we are not skilled enough to differentiate the species from one another.  These beetles are commonly called Stink Beetles because they emit an odor as a defense mechanism.  Because of their habit of standing on their head with the rear end elevated when disturbed, they are also called Acrobat Beetles.

Letter 2 – Stink Beetle

 

Think it’s a Darkling.
April 17, 2010
This thing came crawling out a hole in our brick wall when it noticed a puddle on the ground as a result of my watering.. I believe it’s a Darkling Beetle, But not sue exactly which kind.
Vince Grgas, San Pedro CA.
Southern Los Angeles area

Stink Beetle

Hi again Vince,
You have correctly identified this as a Darkling Beetle, and more specifically, it is a Stink Beetle in the genus Eleodes.  The common name comes from the beetle’s habit of releasing a foul odor when disturbed.  The Stink Beetle is also called an Acrobat Beetle because it assumes a posture with its head down and rear end up in the air, also when threatened.  Alas, we do not feel we have the necessary qualifications to identify your Stink Beetle to the species level.  You can view numerous species in the genus on Bugguide.

Stink Beetle

Letter 3 – Darkling Beetle

 

Subject: What kind of beetle is this?
Location: Second growth hardwood forest, Cortland, N.Y.
December 2, 2013 10:31 am
Durning a wind storm the top of a big black cherry tree splintered and fell down. The center of the tree was mostly hollow. When cutting up the tree for fire wood this beetle was found. There were more beetles and tunnels through the rotten wood. Are they opportunistic or did they cause the death of the tree? Do I have to worry about them attacking my house?
Thanks!
Signature: M. Fortin

we cannot view your attachment.  Please resend and attach a photo or jpg.

Sorry-I don’t know how to attach a photo from iPhoto so I just copied it to this e-mail.
I live in the Finger Lakes area of New York state.  A black cherry tree on my property splintered about 20 feet up the trunk and fell over in a high wind.  The inside of the trunk was totally rotten with tunnels through the soft bits.
There were beetles in the tunnels.  They were approx. 1/4 inch long.  Did they cause the death of the tree or were they just opportunistically feeding on the dead wood?  Should I be concerned about them destroying my house?
Thanks for your time.
M. Fortin

Beetle
Darkling Beetle

Dear M. Fortin,
We managed to view and convert your attachment into a jpg.  This appears to be a type of Darkling Beetle.  We do not believe you need to worry about them infesting your home.  We are going to request a more knowledgeable opinion on this matter.

Eric Eaton  confirms.
You are absolutely right, it is some kind of darkling beetle, on the order of a mealworm.  No threat to structures at all.  It is likely scavenging the dead wood, eating fungus, or something else related to the rotting wood.
Eric

You are so kind!
Thank you for taking the time!
Were you able to see the picture I sent on your last e-mail?

Letter 4 – Darkling Beetle

 

Can you please tell us what kind of bug this is?Hi WTB!
Hello WTB.
Can you please tell us what kind of bug this is? We sure hope so! We found this bug on the dirt path in our back yard. We caught it in our bug vacuum, shortly after releasing an ant lion. I am 8 and brother is 6 and we LOVE bugs, so you can expect lots of questions and photos from us in the future, now that we’ve discovered your great website. We are anxiously awaiting your answer. Thanks! We live in El Cajon, California.
Thank you for your help!
The RamFam4

Dear RamFam4,
Sorry to have taken so long to get back to you, but we have been busy and also the site was down, yet again, due to heavy traffic. We wrote to Eric Eaton for assistance on your beetle. He wrote back: “The hairy beetle is some kind of Tenebrionidae darkling beetle. I’ll forward this message to a friend of mine who is an authority on California beetles. He’ll probably know the genus at least.” We hope to hear more and get you a more positive identification.
Ed. Note: We later heard back from Eric who contacted expert Art Evans who contacted Warren Steiner at USNM. According to Art: “the winner is Trichiasida! This, according to my friend and teneb expert, Warren Steiner at the USNM. According to me, the likely species are hirsuta, hispidula, gabbi, or impetrata. The genus was last revised by T.L. Casey in 1912 and is need of revision!”

Letter 5 – Darkling Beetle

 

Mysterious Beetle
Location:  Casa Grande, AZ
July 27, 2010 7:47 am
I found this beetle just walking across the floor at work. It does not appear to fly and it moves pretty slowly. It likes to play dead. It can flip itself over quite easily with its long legs. It did something like a headstand once, but it has not released any nasty smells or blistering agents, so it doesn’t seem to have that kind of defense.
The underside is of the abdomen is smooth, while the top of the abdomen is covered in tiny bumps. The antennae are short, divided into tiny, somewhat v-shaped segments, uniform, and consist of a single strand with no branching. The mandibles are small and there’s little, if any, gap between them and the head.
Here are some pictures with a ruler for scale. On the picture of the top of the beetle, you can see both the inches and mm side of the ruler. The picture of the underside shows only the inches side of the ruler.
Do you guys know what this thing is? I’m told that they’re fairly common, but I’ve never seen one before and nobody knows what they’re called.
Matt

Darkling Beetle

Update: I think I solved this one myself by looking at a few more
pictures on your site.  There are just too many kinds of beetles.  I’m
99% sure now, but I would appreciate a confirmation, though.
Death Feigning Beetle
Species Cryptoglossa variolosa
2009/08/31/ironclad-beetle-12/
http://bugguide.net/node/view/148169/bgimage
Seems like it has an apt name.  It played dead any time I went near
it.  Note that this one was originally covered in sand or dust giving
it a whitish appearance, like I see in many other pictures.  This one
got a bath before its photo shoot, which is why it’s solid black.  It
was then released, avoiding unnecessary carnage.
Matt

Darkling Beetle

Hi Matt,
YOur beetle is a Darkling Beetle in the family Tenebrionidae, but we are having issues matching it to a species.  It looks quite similar to
Asbolus verrucosus, which is pictured on BugGuide,  though that species appears to be gray while your specimen is black.

P.S.  The Death Feigning Beetle you cited is in the same tribe, Centriopterini, as the Darkling Beetle we cited.  We will check with Eric Eaton to see if he can provide a conclusive answer.

Please note that this beetle was initially grey/white.  If it’s like
some of the pictures I’ve seen, that white or grey may be sand or dust
or something similar.  This beetle was initially covered in something
that washed off.  We actually have a lot of white dust (specifically
lucite, a white dust of plastic particles) at work near where I found
it, so this guy got a bath before I took his picture because I thought
it would make it easier to ID correctly.  That might explain the color
difference.  That said, there’s plenty of ordinary dust outside.  This
is a desert, after all.  I don’t know if it had lucite on it or some
other dust.  There’s simply too much dust around here to know.
It DEFINITELY tries to feign death, though (though I realize that
other beetles may do that).  The first thing it did when I examined it
was to flip over and lie still for several minutes.
Unfortunately, I released the specimen already.  For future reference,
what parts of it should I have tried to get a good picture of?  I no
longer have that beetle ID guide my biology teacher had years ago, but
I remember that it had me do things like count the number of segments
in the beetle’s leg (and to carefully look for hidden segments).  I
tried to find some kind of helpful guide like that online, but had no
luck.  That’s when I found your site.
Matt

Hi again Matt,
Thanks for writing back with additional information.  As we stated earlier, we are waiting for Eric Eaton to get back to us.  The kinds of details that help identify beetles are antennae and legs.  We believe there is enough detail in your photos for someone with more refined skills of identification, like Eric Eaton, to be able to identify your beetle.  Please be patient and see what kind of response we receive.

No hurry.  I just thought I’d let you know that it was white & dust
covered before, given that the coloring was confusing you.
Incidentally, if you want ideas for future content for your blog,
consider giving out tips on getting good photographs (and which parts
are important to show in detail).  I had to take dozens of photos
before I got anything but a black blob.  And my “ruler” looks strange
because it was actually a PDF that I printed out, because I didn’t
have a ruler handy (or rather, the ruler I did have was metal and too
shiny to be readable when photographed.
Matt

Letter 6 – Darkling Beetle

 

Subject: Fuzzy blue bug
Location: West Texas
October 27, 2012 9:29 pm
Hello,
My kids are cleaning out an old horse/goat/cow pen in West Texas. They came across this bug.
He (and his many family members) were living amongst the animal droppings. It was just found in late October. Temp was about 75, no rain.
He was about the size of a quarter.
Signature: Jenny Engstrom

Darkling Beetle

Hi Jenny,
This is a Darkling Beetle in the family Tenebrionidae, but that is a very large family and we are having trouble identifying the species.  It looks most like the members of the tribe Centriopterini which we browsed on BugGuide.  The closest photos on BugGuide are of this unidentified species from Yucca Valley and this photo of
Asbolus laevis from the Imperial Valley.  We have written to Eric Eaton for assistance. 

On Oct 27, 2012, at 9:46 PM, Eric Eaton wrote:
Daniel:
I would agree with Asbolus laevis.
Eric

Thanks Eric,
I remember you writing long ago that if I can’t figure out what a beetle is, check the Darklings.

Letter 7 – Stink Beetle or Acrobat Beetle

 

Arizona bug
October 17, 2009
I found this bug on my front porch. Any ideas?
Matt
Sun City, Arizona

Acrobat Beetle
Acrobat Beetle

Hi Matt,
This is a species of Darkling Beetle in the genus Eleodes which are known as Stink Beetles or sometimes Acrobat Beetles because of their habit of sticking their hind ends in the air and releasing an odor meant to deter predators.

Letter 8 – Stink Beetles Mating

 

black beetles? possible stink beetle?
anyhoo! I’d love to know whats up!
thanks
Rebecca Brown Long Beach, Ca

Hi Rebecca,
What a wonderful Bug’s Eye View of these Stink Beetles mating. You must have been crawling on your belly to get that angle. Stink Beetles in the genus Eleodes are found throughout the arid West. They have fused wings which makes flight impossible. They amble along the ground in hilly areas and deserts, and if disturbed, they stick their rear ends up and emit a foul smelling odor.

Authors

    by
  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

6 thoughts on “Darkling Beetle: All You Need to Know for Easy Identification and Fun Facts”

  1. I found two beetles in my new bathroom, one yesterday and the 2nd one today. They look like they are dead but they move their legs. Are they cause a danger to home or family?

    Reply
  2. Western Antelope Valley, CA saw an infestation lasting for four weeks recently. 30 dead in my pool daily. 1st night, hundreds. Now, 15 or 20.

    Reply

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