Caterpillar Hunter: All You Need to Know for Effective Pest Control

Caterpillar Hunter beetles are fascinating creatures known for their striking appearance and unique hunting habits.

One of the species, the Fiery Searcher Caterpillar Hunter (Calosoma scrutator), stands out with its deeply grooved metallic green elytra edged in lustrous reddish-orange coloration.

These meat-eating beetles play an essential role in controlling caterpillar populations, helping maintain a healthy balance in our ecosystems.

Various caterpillar species are prey for these hunters, such as the forest tent caterpillar and the eastern tent caterpillar.

Caterpillar Hunters can efficiently locate their prey and contribute to their population control, ensuring that they do not cause harm to trees and other vegetation in their natural habitats.

Understanding and appreciating the impressive Caterpillar Hunter beetle not only provides fascinating insights into the insect world.

Caterpillar Hunter Basics

Classification

Caterpillar hunters belong to the family Carabidae and are a type of ground beetle.

The ground beetles are a diverse group with over 40,000 species worldwide. Within that, the Caterpillar Hunters have 167 species.

Caterpillar hunters are well known for their beneficial role in controlling pest populations. Here are some classification details:

• Family: Carabidae
• Genus: Calosoma

Identification

Caterpillar hunters can be identified by their elongated, slightly flattened bodies and their large, powerful jaws.

They are recognizable by their large thorax, which is almost the size of their abdomens and much wider than their heads.

They have a metallic blue or green coloration, giving them a distinctive appearance.

Caterpillar hunters are well-adapted predators, feeding on caterpillars and other pests. Their habitat usually consists of gardens, fields, and agricultural areas.

Habitat and Range

United States

Caterpillar Hunters can be found throughout the United States¹.

The main species in the US, Calosoma scrutato are commonly found in forests, gardens, and fields².

Another native US species, Calosoma sayi is also found across the country. 

Some key features of their habitat are:

• Presence of caterpillars as prey
• Availability of leaf litter and soil for hiding

Other Places

The Calosoma sycophanta, or forest caterpillar hunter, is native to Europe.

Moreover, eight species of Calosoma are found in the southern Levant, including Egypt, Israel, and Jordan.

Physical Characteristics

Color Variations

Caterpillar Hunters exhibit a variety of colors, including:

• Red: Some species have bright red markings or bands on their bodies.
• Green: Green is a common color in caterpillars to help them blend in with foliage.
• Brown: Many Caterpillar Hunters have a brown color, providing excellent camouflage.

Additionally, they may display gold or dotted patterns to help with camouflage or mimicry.

Size and Shape

Caterpillar Hunters vary in size and shape. Examples of different sizes include:

• Large: Some species grow up to 4 inches (10 cm) in length.
• Small: Others may be as tiny as 0.5 inches (1.3 cm) in length.

Shape variations within Caterpillar Hunters range from slender and elongated to short and stout, each adapted to their specific habitats and lifestyles.

Life Cycle

Eggs

The life cycle of a caterpillar hunter begins with the eggs.

Female caterpillar hunters lay their eggs on plants, providing a food source for the soon-to-hatch larvae.

• Eggs are small and inconspicuous
• Laid on leaves or stems of plants where caterpillars are present

Larvae

Once hatched, the caterpillar hunter larvae feed on their preferred prey: caterpillars.

Some examples of the types of caterpillars they consume include the Forest Tent Caterpillar and the Saddleback Caterpillar.

• Larvae of the spiders are active predators
• Grow and molt through several instars
• Appearance changes as they mature

Pupate

The final stage in the life cycle is pupation. Caterpillar hunters form a cocoon, typically attached to a leaf or a twig, where they will transform into their adult form.

During their life cycle, caterpillar hunters play a crucial role in controlling the populations of various caterpillar species.

By preying on these pests, they help maintain the balance of the ecosystem and contribute to the overall health of the environment.

Feeding Habits

Diet

Caterpillar Hunters are insects that primarily feed on caterpillars. They can be found on trees and among foliage, where they search for their prey.

Their food choice can significantly impact the caterpillar population, providing a form of natural pest control.

Some examples of their diet include:

• Gypsy Moths and Tent Caterpillars
• Leaf-feeding caterpillars
• Moth larvae
• Butterfly larvae

Pest Control Role

Biological Control

Caterpillar Hunters play a crucial role in biological control as they help to regulate pest populations.

They are known as voracious eaters, capable of consuming large amounts of caterpillars in a short period of time.

They feed on various caterpillar species that can harm plants and trees.

Beneficial Insects

Caterpillar Hunters are considered beneficial insects because they combat pests without harming plants.

They act as a natural alternative to chemical pesticides.

Do Caterpillar Hunters Bite or Sting?

Caterpillar Hunter beetles (Calosoma spp.) do not sting, as they do not possess a stinger. However, like many other beetles, they can bite if handled or threatened.

The bite of a Caterpillar Hunter beetle can be painful due to their strong jaws, which they use for hunting and consuming prey, but it is not dangerous or venomous to humans.

It is always advisable to handle any wildlife, including insects, with caution and respect to avoid any unnecessary stress to the animal and to prevent bites or other defensive reactions.

Caterpillar Hunter Species

Calosoma Scrutator

The Calosoma scrutator, also known as the searcher, is a large, metallic green beetle that is native to North America. 

Distinguished by its bright, metallic green head and wing covers with copper or purple highlights, it primarily preys on:

• Gypsy moth caterpillars
• Tent caterpillars
• Cabbage loopers
• Cutworms
• Armyworms
• Loopers

Related Species

There are many other Calosoma species that fall within the caterpillar hunter beetle category. Some common species include:

• Calosoma sycophanta: A European species that preys on gypsy moth caterpillars.
• Calosoma frigidum: Known as the forest caterpillar hunter found in the boreal forests.
• Calosoma wilcoxi: Targets tent caterpillars across North America.

These caterpillar hunter species are vital for controlling caterpillar populations, contributing to natural pest management in various ecosystems.

Conclusion

In essence, Caterpillar Hunter beetles, particularly the Fiery Searcher Caterpillar Hunter, are invaluable assets in natural pest control, targeting harmful caterpillar species across diverse habitats.

With their distinctive appearance, adaptive features, and voracious feeding habits, they contribute significantly to maintaining ecological balance.

Recognizing the importance of these beetles in biological control offers a sustainable alternative to chemical interventions, underscoring the intricate interplay and mutual benefits within ecosystems.

Footnotes

¹ Penn State Extension
² University of Kentucky Entomology
³ Wisconsin DNR
⁴ NC State Extension Publications

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 – Caterpillar Hunter Larva

Texas Bugs Everywhere
Location: Bulverde, Tx
April 17, 2012 6:27 pm
Hey!
I got home from vacation recently and found my yard in the Texas hill country swarming with these black bugs. I have never seen anything like them and I am curious what they are.
Plus, I have a little kid in the house who likes putting things that move into his mouth, so I am wondering if they are in any way poisonous.
Signature: Jake

Dear Jake,
This is the larva of a Caterpillar Hunter in the genus Calosoma, and though we cannot identify the exact species, there is a good chance it is the larva of the Fiery Searcher, Calosoma scrutator.  Interestingly, we just finished posting a photo of a Fiery Searcher. 

Both the larva and the adult Caterpillar Hunter is a fierce predator that can consume large quantities of caterpillars.  They are not poisonous, but they might bite if carelessly handled.  Though it may hurt a youngster, the bite of a Caterpillar is not dangerous.

Letter 2 – Black Caterpillar Hunter

Subject: Its BIG
Location: Fort Gibson, Oklahoma
April 15, 2017 1:30 am
I found this bug or beetle crawling in my bed. I first heard it, as I must have laid on it, and it started making a humming type noise which woke me. It was then it was on my arm crawling. I whisked it off onto my sheet and took snapshot. Then took it outside.
I want to see if you may identify it for me?
Signature: Not Important

Dear Not Important,
This is a Black Caterpillar Hunter, Calosoma sayi, and though they are not dangerous to humans, they do have powerful mandibles that could nip someone who tries to handle one.  According to BugGuide:  “Predatory on other insects, especially caterpillars.”

Letter 3 – More Caterpillar Hunter Larvae in Texas

Caterpillar, Worm or WHAT?
Location: Texas
April 17, 2012 12:15 pm
Can you tell me what this is? They are everywhere! Is it a beautful butterfly waiting to be born? Or something dreadful? I’ve found 2 in the house and there are lots of them around the neighborhood. I’ve never, in all my 51 years seen one before.
Signature: Michele

I want to feed it, but not sure what I should give it.  tried putting a tiny bit of water in the enclosure  It ignored.  Tempted to turn it out into the wilderness, but so many neighbors are reporting stepping on and squashing them, I am afraid.  Want it to survive!!!

Hi Michele,
We just posted a photo of a Caterpillar Hunter Larva from Texas.  Based on your letter, there is a population explosion, possibly due to a large number of caterpillars this season, and you should expect to see adult beetles in the near future.  Caterpillar Hunters eat caterpillars.  Nature has a way of balancing out the populations of natural predators and their prey species.

Thanks SOO much!  I asked everyone I knew and even strangers on the street what it was (I carried him around for a few days!).  NO one had ever seen one.  AND, I would have NEVER though to have fed him caterpillars.  Glad I set him free to do his job!

Letter 4 – Caterpillar Hunter Larva

what is this?
I found this bug in a puddle and it looks like a caterpillar, but it has 6 legs and they are alomost beetle-like. I’ve looked through all the caterpillar pages and found nothing. Do you think you could identify it?

This is a Beetle Larva. We are nearly certain it is the larva of one of the Caterpillar Hunters in the genus Calosoma.

Letter 5 – Caterpillar Hunter Larva

Subject: Odd Soil Dwelling Bug..
Location: BC, Canada
May 13, 2015 5:26 pm
I was out gardening this afternoon and after pulling up some plants in my garden, up for the soil pops this black insect. I have only seen them dwelling withing the soil and never above ground like you would a normal beetle would, not that I am sure it is even a beetle..

Now I have seen smaller versions of this one, but this particular fellow was about an inch in length. Other times they have been about half that size.
I have no idea what it could be and it would be nice to get a name or any info on this bug.
Signature: Kat

Dear Kat,
This is the Larva of a Caterpillar Hunter, one of the Ground Beetles in the genus Calosoma.  It is impossible to determine exactly which Caterpillar Hunter this will become, but the only species mentioned on BugGuide as being found in British Columbia is Calosoma frigidum.

Letter 6 – Black Caterpillar Hunter

Three bugs
Hi there, I found these critters in my backyard around my garage. After perusing your site (which is great by the way) my guess is the smaller guy is maybe a leaf beetle, the bigger black one maybe a borer (or hopefully a catapillar hunter) of some kind, and I know the yellow-on-black guy is a ladybird beetle larva, but haven’t found the species yet. Can you help me be more specific with these? Thanks,
Tim in Winnipeg, MB

Hi Tim,
We believe this is a Black Caterpillar Hunter, Calosoma sayi, but we will check with Eric Eaton since BugGuide lists it as a Southern species. You are correct on the Ladybird Beetle Larva and we are not sure what species the pupa is, but that could also be a Ladybird.

Eric Eaton provided this confirmation: “Congratulations:-) Yes, those two are BOTH Calosoma beetles. I don’t know how to tell the species apart, myself. “

Letter 7 – Black Caterpillar Hunter

Unidentified Beetle
Location: Kinder, Louisiana
August 15, 2011 4:18 pm
I found this cute little beetle running across a parking lot. I scooped her up and brought her inside for a photoshoot. I let it free soon after. I was wondering what type of beetle she (or he) was. Thanks for the help in advance!
Signature: Skyler

Hi Skyler,
The large size of this Ground Beetle indicates that it is one of the Caterpillar Hunters. The southern sighting and the red puncture marks on the elytra or wing covers identifies it as a Black Caterpillar Hunter, Calosoma sayi, we believe.  You may verify our identification on BugGuide.

Letter 8 – Black Caterpillar Hunter

Subject: What kind of beetle is this
Location: Mississippi
August 5, 2014 9:52 am
I live in Mississippi and found this in my office.
Signature: Tayne

Dear Tayne,
This beautiful beetle is a beneficial Black Caterpillar Hunter, Calosoma sayi.  You can compare your image to images posted to BugGuide.  According to BugGuide, it can be recognized by being:  “Large, black, with prominent gold or red punctures and blue or green margins of elytra. (These are not prominent on cursory inspection–the beetle appears all black.)

Resembles C. calidum but larger (25-28 mm vs. 16-27 mm) and more southern in distribution. Quoting from Ciegler (2000).”  The red punctures are visible in your image despite the lack of critical focus and clarity.

Letter 9 – Caterpillar Hunter

While working in the yard at our Mt Washington, Los Angeles offices, we saw not one but two of the Calosoma species, Caterpillar Hunters. We released both into the vegetable patch hoping they would earn their keep by devouring the Geometrid Caterpillars that are chewing our beet greens, chard and other leafy greens.

When handled, the Caterpillar Hunters released a not entirely unpleasant odor. We believe this is Calosoma semilaeve based on Charles Hogue’s wonderful book, Insects of the Los Angeles Basin.

Letter 10 – Caterpillar Hunter

Stag Beetle?
This bug was out at the heat of the day “running” toward me (twice)from several feet away. It would stop in front of me-both times on pavement in the sun. The one in the picture posed for several shots. It is about 2 cm long although I did not have a ruler at the time.

I am curious as to what it is and if it will help or harm my gardens/trees. We live in CA within 2 miles of the beach. Never seen it before or since. Thanks for you help. PS I let both go on their way

This is a species of Caterpillar Hunter. We believe it is Calosoma semilaeve. We received so many identification requests from Southern California in mid May, we were prompted to declare is a secondary Bug of the Month.

The species is prone to periodic population explosions, which we beleive can be attributed to the rainfall pattern of last winter. That pattern produced lush vegetation and many caterpillars, the food of both the larval and adult Caterpillar Hunter.

Letter 11 – Caterpillar Hunter

Hi, Bugman. I love your site, although I’m glad I don’t have any of those bugs at my place! The one I found is bad enough. I found it in my front yard in suburban Chicago. Can you ID it?
Jerry Palm

Dear Jerry,
You have photographed a dead Caterpillar Hunter, Calosoma scrutator, one of the Ground Beetles from the family Carabidae. They are predaceous, feeding on insects and other small animals. They are especially fond of caterpillars.

They help to control Gypsy Moths and Tent Caterpillars. Adults will climb trees and they can also fly, often being attracted to lights in the spring. They are beneficial and should not be killed.

Letter 12 – Caterpillar Hunter

Need help with id on Beetle
Hello,
I live in Aston, PA and while leaving for work one morning I found this beautiful irridescent green beetle in our stairwell. In all my 51 years I’ve never seen one of these guys. I am attaching two photos of the top and bottom of this beautiful beetle.
Elwood McKay

Hi Elwood,
This is a Caterpillar Hunter, Calosoma scrutator, one of the Ground Beetles. Both adults and larvae have ravenous appetites for caterpillars, and they are very helpful in the control of the pestilence known as the Gypsy Moth.

Letter 13 – Caterpillar Hunter

Cool Looking Beetle
Hi,
I found his little guy in my store the other night and took him home to show my kids. It gave the girls a good squeal. They loved it, the next morning we let it go. They wanted to keep it and wanted to know what it eats, but if it’s a Caterpillar Hunter (Calosoma Scrutator) I’m not feeding it! Is that what it is? Love Those Critters
Oklahoma
P.S Love your site!

Hi Oklahoma,
You are correct. This is a Caterpillar Hunter and it is a beautiful specimen.

Letter 14 – Caterpillar Hunter

A few pics
I am sending these pics I took of a Polyphemus Moth, some sort of Hawk Moth?, a couple shots of spiders (I think they may be some sort of Orb Spider? There are literally hundreds of them in every nook and cranny of my acreage!) and a large bettle I found in my sunporch.

I have looked through your site to try and ID this beetle, but I am on dial-up, and therefore the length of time it is taking me to load up all of the beautiful pictures to compare it to is almost enough to make me want to throw my laptop across the room … lol … I have run a search and tried every sort of search words … ahh well, maybe you can help me 🙂

I have began taking “bug” pictures as a hobby, and I am enjoying your site each and every time I visit. I wanted to send along a few pictures of bugs from angles that perhaps you do not have pics from … like the fluffy poly moth’s face and head … he/she almost looks cuddly 🙂 And the spider picture where it is eating a fly might work for your page devoted to insects eating other things 🙂

I would love to know what type of beetle is in the attached picture … It was very aggressive, agile, and active … He was around the size of an adult’s thumb … Very nice colouring, but in the pictures he is covered in fuzz … crawling around under a sofa in the sunporch where the dogs sleep will do that to ya! … lol …

It took a couple swings at my Rottweiller and I decided to release it somewhere where my dogs would be safe 🙂 Thanks so Much!
Heather – Central Saskatchewan, Canada

Hi Heather,
While all of your images are very nice, it is very complicated for us to post multi-image letters efficiently. The beetle in question is one of the Caterpillar Hunters, probably Calosoma calidum.

Letter 15 – Caterpillar Hunter

Red speckled beetle found in MN
Hello,
I spent hours and hours looking at the 13 beetle pages (had to read most everything – fascinating!). Great site!!! Maybe this is not a beetle?? Because, I did not see this one anywhere. It looks somewhat like some of the wood boring ones, but not quite.

I did find a White Spotted Pine Sawyer in my house just a couple of days ago, but I found an identification on line for that one fairly quickly. This one I am having less luck with. He has bright metallic reddish specks on his back in lines. In the photos, it looks like the red spots fade to green as they go down his hind end, but that must have just been the lighting – all the specs or spots are reddish – almost bright, dark pink even?

I did not notice until I looked at the pics, but this little guy has a pretty good set of pincer type jaws too. He is very fast at crawling along – hard to photograph. I found him in my bathroom just cruising back and forth on the floor between the toilet and the tub. He/she is about one inch long.

I am in East Central Minnesota (Ogilvie, to be exact = middle of nowhere on a 160 acre horse farm with more hay fields than trees). Thanks for your site!
Take Care!
Kayla Hagel

Hi Kayla,
The reason you could not locate your beetle on our site is that it is a new species for our site. We are relatively confident we located your Caterpillar Hunter, Calosoma calidum on the Ground Beetles of Canada Website. Eric Eaton provided this confirmation: “Congratulations:-) Yes, those two are BOTH Calosoma beetles. I don’t know how to tell the species apart, myself. “

Letter 16 – Caterpillar Hunter and Oak Leaf Roller Outbreak

Big Beetle in FL
Location: Tampa, Fl
March 27, 2011 4:13 pm
Hi Bugman,
I’ve been living in Florida the last 8 years and never seen this kind of bug. Maybe it’s the size that has me flustered as it’s rather large at over 1 inch long. It scared my wife in the garage and we are in The Tampa Bay area.
Signature: CT

Dear CT,
This is one of the Caterpillar Hunters in the genus Calosoma.  They are important predators that help to control caterpillar populations.

Daniel,
I’m glad I asked and the Calasoma will come in handy. We’ve had a a very horrible webworm problem in the Tampa area this year (pictures attached). That accumulation of worms on the trunk is from one and a half days of worms.
Thank you, Cesar Tioseco

Hi Cesar,
Thanks for writing back with your images of the Caterpillar infestation.  We believe these are probably the same Caterpillars that we have received several letters regarding thus far this year from Florida.  Our first letter arrived March 7 and the caterpillars were identified as Oak Leaf Rollers, Argyrotaenia quercifoliana. 

The Texas A&M University website has information on these Caterpillars.  For various reasons, there are periodic outbreaks of certain insects that create media attention and cause concern, and then all is forgotten until the creatures reappear several years later in prodigious numbers again. 

We are curious about the control method that is documented in your photographs.  Is this a sticky tape product specifically designed to control insects on trees?

Letter 17 – Caterpillar Hunter

Subject: Creepy beetle
Location: Sw Arizona- Sonoran desert
August 21, 2014 2:30 pm
Hi bugman,
I’ve seen these bugs in large groups in a snake trap. They have been seen eating caterpillars, and were found with a dead mouse. We are calling them creepy beetles that seem to be very aggressive and vicious.
Signature: Intern

Dear Intern,
We have problems with the use of the term vicious to describe a predator that is capturing prey to eat.  This is a Caterpillar Hunter in the genus Calosoma, quite possibly Calosoma semilaeve, a species we featured numerous times in 2008 when we received numerous reports from Southern California, prompting us to name it as a secondary Bug of the Month for May 2008.

We believe your Caterpillar Hunter may be Calosoma semilaeve, a species posted to BugGuide under the name Callisthenes semilaevis, indicating that it is in a subgenus.  Caterpillar Hunters are very effective predators that feed primarily on Caterpillars and other insects, so they are incredibly beneficial. 

We imagine they might be opportunistic feeders that take advantage of dead animals like the mouse you found.  This species seems to experience years of few sightings, and then sudden population explosions, perhaps linked to years when desert caterpillars like the Whitelined Sphinx Caterpillars are also plentiful.

Hello and thank you for responding to our resourceful intern! I have worked here at Organ Pipe Cactus National Monument (Arizona) for over 25 years and have never seen anything like this.

We do get “blooms” of insects and this is certainly one. We have abundant caterpillars, as we frequently do in summer, of Hyles lineata and so they are certainly plentiful. The beetles do seem at first to be a little “creepy” in their behavior but I would not call them vicious. So it goes.

The odor is a bit much, but I have become accustomed to and now rather enjoy the odor of Pinacate beetles (Eleodes).
We have some really nice photos of other insects “in bloom” – mostly beetles and bugs – and would be happy to share if you like.
Again, thank you!
Charles Conner    Biological Sciences Technician

Hi Charles,
We would love to receive your other insect images.  Please use the standard form when submitting them.  Great World Cup image, but sadly, we won’t post images that we cannot get permission to include online.

Letter 18 – Caterpillar Hunter

Subject: Beetle?
Location: Whittier, CA
May 18, 2016 4:48 pm
We found this Beetle in our garage. It is May 2016, about 445p in Whittier, CA.
It was between some boxes on the floor.
We looked at your site and think it’s a Stink Beetle but weren’t 100% sure.
Thank you!
Signature: Cunningham Family

Dear Cunningham Family,
This is one of the Caterpillar Hunters in the genus Calosoma, and interestingly, we just posted a gorgeous image of a relative known as the Fiery Searcher. 

We have always considered the black Caterpillar Hunters found in Southern California to be Calosoma semilaeve, though the species is not represented on BugGuide. 

BugGuide now has a posting of a black member of the genus from Southern California that is identified as Calosoma parvicolle and we would not entirely rule out that as your species.

Letter 19 – Caterpillar Hunter

Subject: Unknown Insect Larva
Location: Denver, Colorado
May 28, 2016 5:08 pm
Dear WTB,
While on a walk through my neighborhood in Denver, I found this black insect larva crawling around the sidewalk.
It was fairly large, I’m guessing around 1-1/2″ long, and moved at several inches per second, making taking a good photo a little tricky. This happened today, May 28th.

The area is a low-density urban neighborhood with lots of yards, lawns, gardens, and trees. There are water sources in the general area, but not near where the insect was found.

I’m guessing this is some type of beetle larva, but I’ve definitely never seen this species, or one that come close to this size, before.
Signature: Duncan

Dear Duncan,
This is the larva of a Caterpillar Hunter, a Ground Beetle in the genus Calosoma.  Both larvae and adults from this genus consume large numbers of caterpillars.  See this BugGuide image for comparison.  We are postdating your submission to go live to our site during our absence from the office in mid-June.

Letter 20 – Caterpillar Hunter

Subject: Ground Beetle
Location: Stevens Point, WI
April 29, 2017 6:53 am
Hello, I found this little guy in our 5 year old native wildflower garden in Stevens Point, WI on 4/26/17. He caught my eye with his bright blue outline, is this a Snail Eating Beetle? Thanks!
Signature: Ben Kollock

Dear Ben,
Your Ground Beetle is actually one of the Caterpillar Hunters in the genus Calosoma.  We believe we have correctly identified it as Calosoma frigidum based on BugGuide images.

Letter 21 – Caterpillar Hunter from Australia

Subject: Stinky black beetle
Location: Laverton Western Australia
March 19, 2013 4:37 am
Hi, these bugs really stink. There are hundreds of them around at the moment. They seem to detect you and head straight for you. If they get on you and you flick them off they leave a horrible stink behind. I have tried to find out what they are called and info about them but have had no luck .
Signature: Bugsy

Dear Bugsy,
This is a Ground Beetle in the family Carabidae.  It appears to be a Caterpillar Hunter in the genus Calosoma, and it might be Calosoma oceanicum, which accoring to the Calosoma of the World website is found in Australia.  As with most creatures, populations spike when there is a ready food supply, and perhaps conditions have produced an abundance of Caterpillars this year that can support the Caterpillar Hunter population.

Letter 22 – Caterpillar Hunter from California

What is it?
Hey guys,
Today April 26, a bunch of these beetles just showed up and they are everywhere! Never seen them around here before and the fact that they are in numbers makes me wonder…
Anyhow, before I smash them or roast them and eat them, thought I better find out what they are. I did review your many fine photos and saw a couple similar but not exact specimens. Thus the inquiry. I generally don’t use pesticides for all the obvious reasons. So, if these guys are problematic will the birds eat them? Thanks,
Greg
San Diego
Found them in the lawn and around foundation plantings.

Hi Greg,
Interestingly, when we tried to use BugGuide to identify what species of Caterpillar Hunter in the genus Calosoma you have, we found an identical request. Your request came first, but because we are a very small operation, and the posting is done internally, not through contributor posting, the image on BugGuide was posted first.

We will see if an answer is provided. Our money is on Calosoma semilaeve, which seems to be a well documented California species. Calosoma cancellatum is another possibility.

Frequest, well-spaced rains in southern California in the past six months are resulting in good vegetation growth and an increase in caterpillar populations. This means a food source for predators, including your Caterpillar Hunter.

Letter 23 – Ground Beetle from Ireland submitted on Saint Patrick’s Day

Unknown beetle from the south of Ireland
Location: County Kerry, south Ireland
March 17, 2012 8:38 pm
Hello Bugman!!
While hiking along the coast of southwestern Ireland, I came across this well armored beetle mucking about in the sheep muck!,, what might he be?
Signature: Kyle from Toronto, Canada

Kyle,
We are rushing to post your submission on Saint Patrick’s Day before the car arrives.  We believe this is a Caterpillar Hunter and we will research later.

Update:  Ground Beetle identified as Carabus clatratus
Additional research led us to this Ground Beetles of Ireland section on Habitas.org.uk and we found a nice photo of Carabus clatratus along with some wonderful information. 

It is described as:  “A large (22-28mm) metallic bronze, green or black ground beetle with conspicuous metallic bronze or red elytral depressions. Occupies a wide range of habitats in areas of high rainfall but principally in peaty marshes, wet hay meadows and boggy lakeshores. Can feed under water and prefers water-logged soils. ”  

We are fascinated that this endangered species is considered amphibious.  Additional information includes:  “World Distribution: Widespread across the north Palaearctic; Eurasian Boreo-temperate; (55) but local and in decline in western Europe (extinct in Switzerland and England).

Irish Status: Formerly widespread on certain types of blanket peat in Ireland (Johnson & Halbert, 1902) but now very local and probably in decline in most areas. Presumed extinct in at least Londonderry, Tyrone and Antrim with only a single extant site in Down, at Edenderry Marsh west of Belfast (Day, 1987).

Locally common in wet pasture and bog in Fermanagh but elsewhere its status is unknown though it should still be widespread in the west in areas of undisturbed Atlantic bog.

Ecology: According to Koch (1992) a stenotopic tyrphophilous species in central Europe. In Ireland recorded historically from wet places in bogs (Johnson & Halbert, 1902). McFerran et al. (1995) have recently pitfall-trapped considerable numbers in lakeshore pastures and hay meadows in areas of Fermanagh where the very wet Calp Series of soils (but not peat) predominates. It is not, therefore, restricted to peatlands in our area, although very wet ground conditions seem essential. According to Thiele (1977) it is amphibious, feeding in bog pools and shallow lake waters as well as in terrestrial habitats.”

We also located a nice photo on BioLib.

Letter 24 – Caterpillar Hunter in Los Angeles: Will this year see a significant rise in sightings?????

Subject: Calosoma?
Location: Los Angeles
March 18, 2015 4:50 pm
Found the way! I posted on the blog few minutes ago.
Is the bug in the pictures a Calosoma?
I found them in my backyard in West Central Los Angeles.
Thank you!
Signature: Simona

Hi Simona,
We agree that this is a Caterpillar in the genus Calosoma, probably Calosoma semilaeve, which we named Bug of the Month in May 2008 because of the sudden appearance of large numbers of the beetles in Southern California. 

For several years, we have noticed increasing numbers of Whitelined Sphinx Moths and their caterpillars might also be getting more plentiful in the area, providing a food source for the Caterpillar Hunters and an increase in their populations as well. 

These cyclical appearances are all part of nature dealing with bountiful food supplies, and then dearths of sightings when food is scarce.

Update:  April 11, 2015
Wayne’s Word Palomar blog has this to say about Calosoma semilaeve:  “Common calosoma (Calosoma semilaeve), a large beetle that runs free during daytime hours in search of prey. With its long cursorial legs it runs very fast. When disturbed or threatened it emits a foul oder that smells like burning electrical insulation.”

Letter 25 – Caterpillar Hunter Larva

What’s this bug?
Hi Bugman!!
We love your website!! Anytime we want to know what creepy crawly is crawling around, we seem to find it on your site. We are having a hard time finding out what this is…. I thought it might be a Hellgrammite, but our bug doesn’t have enough legs and we don’t live anywhere near water.

It crawls kind of like a catapeiler, but has pinchers. It’s like a morph of some kind of millipede or something. Anyway, we live in the high desert in California and we have had a bit more rain than normal this season. We have butterflies galore and with the butterflies came these bugs. I have never seen them before. They are only out in the day.

I looked everywhere to take a picture at 8:30 pm and was amazed to find only one straggler in our garage. They are everywhere in the day, especially climbing up the walls outside. I will try and send a better picture of one from the daylight. This one seems small compared to the others I have seen.

Anyway, I’m sure you know what this is and we are curious to know. Thanks for all your help and for putting together a great and informative website!!!!
The Kibbe’s

Dear Kibbe Family,
You might not think to try to identify this Caterpillar Hunter on our beetle pages, but it is a beetle larva. Caterpillar Hunters in the genus Calosoma undergo complete metamorphosis, and the larva look nothing like the adult, but unlike many insects that undergo complete metamorphosis, the larva and adult both have the same diet. They eagerly consume any caterpillars they encounter, which makes them a valuable natural control to caterpillar overpopulation.

Letter 26 – Caterpillar Hunter Larva

Unknown Black Killer Bug
Hello,
We have found several of these bugs in our yard. No one knows what they are, and we can’t find them on the internet. We have witnessed one of these bugs bite a earthworm in half. We see them chase the earthworms out of the ground, and attack them. They are pretty fast. We live in Spokane, WA. We hope you can tell us what it is. Thank you very much for your time.
Daniel

Hi Daniel,
This is a larva of a Ground Beetle in the family Carabidae. We suspect it is a Caterpillar Hunter, Calosoma scrutator.

Letter 27 – Caterpillar Hunter Larva

This is the first time this bug has been here in 20+ years that I know of. We live in So. Calif., South West Riverside county. Each year we have invasions of different bugs, but rarely the same bug here twice in a row (years wise). This year is a hoard of 3 different catapillars and this one (pictures). It looks kinda like a Hellgrammite.

They are all over the place, we have seen them eating dead catapillers but so far not killing them. They are about 1 1/4 inches long. One pict he is sitting on a 2×4 peice of wood. Sure would like to know what they are…friend or foe? Your web site is fantastic with good info, thanks for being there for the people that are interested in insects. Thanks
Larry

Hi Larry,
This is a Caterpillar Hunter Larva in the genus Calosoma. Caterpillar Hunters are Ground Beetles. We are expecting a big year for caterpillars in california because of all the rain over an extended period of time, which provided vegetation. We have gotten a few requests already for Caterpillar Hunter Larvae identification.

Thanks Daniel for the fast responce. Today I watched the larva in action and yes they are ferocious little critters. This year we do indeed have an over abundance of 4 types of caterpillers. I am glad we have the Hunters as the catetpillers are eating all vegetation they can find including the garden. Once again thanks and you have a real nice web site. I ues it often.
Larry

Letter 28 – Caterpillar Hunter Larva

Having trouble identifying this guy!
Location: Vancouver
October 8, 2011 7:35 pm
Hi! I found this bug on the forest floor. Consulted my Bland identification book but can’t determine what it is!
Signature: David

Hi David,
This is the larva of one of the Caterpillar Hunters in the genus Calosoma.  The adults are large active Ground Beetles that often have metallic coloration.  Both larvae and adults are ravenous feeders that consume caterpillars.  We would much rather see living specimens than preserved specimens in bottles.

Thank you Daniel, I will try my best to snap pictures before preserving or pinning them next time.

Thanks David,
We realized your specimen was for a collection.  Our real issue is with people who squash everything they see and then send us photos of mangled corpses for identification.

Letter 29 – Caterpillar Hunter Larva

Subject: Black bug, termite looking.
Location: SLC, Utah
May 12, 2013 9:19 am
I found some of these up againts my house when the hose water caused them to reach for higher ground. They have pincers on the front. Its spring here in SLC, Utah. Its not a termite is it? Thanks
Signature: Maren

Hi Maren,
This is the larva of a beneficial Caterpillar Hunter in the genus Calosoma.  Both larvae and adults eat Caterpillars.  Some adult Calosoma species like this Fiery Searcher have beautiful coloration.  See BugGuide for verification.

Letter 30 – Caterpillar Hunter Larva

Subject: unknown bug
Location: Santa Monica Mountains
March 16, 2015 8:23 am
I am so happy I found this service. Thank you for your expertise! I found this bug a couple of weeks ago in the Santa Monica Mountains. I have been keeping it with my meal worm farm and it has grown nicely.
Signature: Jeannie

Dear Jeannie,
We wrote to your briefly yesterday that this looked like a Caterpillar Hunter Larva and that it would probably eat your Meal Worms, and today there is a letter in our mailbox that we have not yet answered that contains a blurry image of what appears to be an adult Caterpillar Hunter in the genus Calosoma, so we decided to retrieve your letter and post it.  We believe this is going to be a significant year for the caterpillars of Whitelined Sphinxes in Southern California, so it might also mark an increase in Caterpillar Hunters, a predatory species.

Letter 31 – Caterpillar Hunter Larva from Serbia

What is this bug?
January 10, 2010
I found it in the garden under a flowerpot , I think it was eating a very small white root, i think its some kind of larva, since it had legs only on the front side of the body.
Stevan Kolarski
Serbia, Vojvodina, Deliblato

Dear Stevan,
This is a Ground Beetle Larva, probably a Caterpillar Hunter in the genus Calosoma.  You may compare your specimen to these images posted to BugGuide of a North American species.  Your larva may be Calosoma sycophanta, a European species that was introduced to North America in 1905 to help control the introduced Gypsy Moth.  It is also pictured on BugGuide as an adult.

Letter 32 – Caterpillar Hunter Larva: Stop the Carnage

PLEASE help! Please identify this bug.
Dear Bugman,
I found two of these so far. I think it is a beetle larva. Not sure if it is or not, and if so not sure what kind it is at all. They have six legs up front that seem short and it has VERY strong pincers up front/mouth area.

The first one bit/pinched a plastic fork pretty good as I tried to pick it up to inspect, and the second one bit/pinched my dog on the tongue when he picked it up with his mouth.

They are shiny black on the back and a grayish white color on the complete underside. PLEASE see attached photos. I am asking because I have disposed of both of them and do not want to kill a non destructive insect.
Thanks you for your time!!
Matt A.

Hi Matt,
Stop the Carnage. This is the larva of a Caterpillar Hunter, Calosoma scrutator, one of the larger Ground Beetles. Both the beautiful green adult and the larvae devour quantities of harmful insects, including the introduced pestilence, the Gypsy Moth.

Letter 33 – Caterpillar Hunter or Fiery Searcher

Beautiful Beetle
May 8, 2010
Here is a pretty beatle i found in my dogs bowl this morning, and thought i’d take some pics that ya’ll might enjoy. I was also wondering if this beatle is the end result of all the grubs i keep finding, i sent a pic of them before to ya’ll asking but havent heard anything. But here enjoy this beautifuly colored beatle.
Caitlyn in Austin
leander texas

Dear Caitlyn,
We are very happy we decided to look at some old letters from when we were out of the office.  This gorgeous beetle is a species of Caterpillar Hunter known as a Fiery Searcher, Calosoma scrutator, and you may read more on BugGuide.  Both adults and larva are ravenous predators that feed on caterpillars.  Though we haven’t seen your other letter, the larvae of the Caterpillar Hunters are not at all grublike.

Letter 34 – Ground Beetle

metallic green ground beetle larger
February 9, 2010
It was found in Midewin National Tallgrass Prairie in Wilmington, Illinois. Just thought it was neat. It is laying next to a ruler with centimeters. Thanks!
Beth R.
Illinois

Hi Beth,
WE believe this is a Caterpillar Hunter in the genus Calosoma, possibly Calosoma sycophanta, a European species that was introduced to help control the invasive exotic Gypsy Moth.  BioLib has numerous photos for comparison.  We wrote to Eric Eaton for his opinion.

Daniel:
Sorry, I disagree.  It is not even in the Calosoma genus.  Something much smaller, but I don’t recognize it.  Carabidae are pretty tough, for me anyway.
Eric

Update:  January 2, 2017
Thanks to a comment, we believe this may be Agonum cupripenne which is pictured on BugGuide.

Letter 35 – Caterpillar Hunter with Prey

caterpillar hunter beetle
I thought you might enjoy this photo I took of the Caterpillar Hunter Beetle enjoying a meal!
Deb from SE PA

Hi Deb,
Awesome image of a Calosoma scrutator earning its common name Caterpillar Hunter.

Letter 36 – Caterpillar Hunters

Subject: Beetle invasion.
Location: Chantilly, Virginia, USA
May 9, 2014 7:09 am
Today I came to work in Chantilly, Virginia and our building is inundated with these beetles. At first glance I thought that they are Japanese Beetles, but something about the shape of the body tells me I’m wrong. I’ve searched several of the insect identification guides but I cannot find any photos that match this beetle.
I’d like to find out what this beetle is, in hopes of understanding why there were none yesterday and there are hundreds of them today.
Signature: +Ed

Hi Ed,
Your beetles are Caterpillar Hunters in the genus Calosoma. The beetle in one image seems considerably darker than the beetle in the other image, so we are wondering if they are all metallic green with red or gold borders.  We believe the discrepancy in coloration is due to camera exposure and lighting. 

We also believe your beetles are most likely Fiery Searchers, Calosoma scrutator, and you may compare your images to the images on BugGuide.  Perhaps populations are peaking this year because there is a significantly larger proportion of prey, namely caterpillars and other insects.

Thank you for the quick response.  I did some searching later and you confirmed my suspicion about Calosoma Scrutator.  Truly a beautiful beetle.
~Ed

Letter 37 – Forest Caterpillar Hunter, not Fiery Searcher

big shiny beetle
November 1, 2009
I found this guy wandering across my office floor this morning (November 1st). I live in Hampton Bays, NY (East End of Long Island). It’s been steadily cooler weather, but we haven’t seen a frost (or been close) yet. He’s about an inch & a half long – the nail in the photo is a good reference. I scooped him up and put him outside for the photo shoot. Thoughts?
Dawn L
Hampton Bays, NY

Hi Dawn,
What a positively gorgeous specimen of the Caterpillar Hunter commonly called a Fiery Searcher, Calosoma scrutator.  The reds and golds on your specimen are much more pronounced than in most individuals. 

They are known to climb trees in search of caterpillars, and though the typical life cycle is one year, adults may overwinter and are reported to survive as long as three years.  You may get additional information on BugGuide.  The Fiery Searcher is one of the predators we plan to profile in the book we are attempting to complete.

How interesting!!  Let me know if you want to use the photos for the book – I have others of her, as well as an AMAZING set of photos of a black widow with her egg sac!  You have a wonderful website, and I rely on it all the time for bug id.  It somehow makes them less scary when you know what they are and learn about them…
Thanks!
Dawn

Thanks for the offer Dawn, but since our book is not an identification guide, we will not be using photographs which will make the publication cost prohibitive.  We will be using old entomological drawings as a more decorative means of illustrating the book.

Update
WE received a comment that corrected this identification as the imported Forest Caterpillar Hunter, Calosoma sycophanta, and according to BugGuide:  “native to w. Palaearctic (east to Siberia)(1); introduced intentionally and established in e.US (so.ME-MD-WV-w.PA) Introduced in 1905 to control Lymantria dispar and Euproctis chrysorrhoea.”

Letter 38 – Fiery Searcher, a Caterpillar Hunter

green beetle
We found this green beetle on our patio umbrella and we cannot find out what it is. We live in Southern Ontario. Can you help us? Thanks,
Kobe

Hi Kobe,
This is a Fiery Searcher, Calosoma scrutator, a Caterpillar Hunter.

Letter 39 – Larva of a Caterpillar Hunter

Subject: Insect Identification
Location: Oklahoma, USA
September 24, 2016 11:51 pm
My son has these in his garden. What are they?
Signature: BPWO

Dear BPWO,
This is the larva of a Caterpillar Hunter, a Ground Beetle in the genus Calosoma.  Many times immature insects have a different diet than the adults, but not so with the Caterpillar Hunters.  Both larvae and adults ravenously feed on Caterpillars.

Letter 40 – Possibly Caterpillar Hunter Larva

Subject: beatiful dark blue
Location: Turkey
November 29, 2012 7:20 pm
i found this beatiful big bug at garden, it looks like trying to find a new home for winter. its leng is nearly 7 cm with 6 legs,if any one know this bugs name please let me know .Thanks.
Signature: Mete

Dear Mete,
This is a beetle larva, and we believe it is a Ground Beetle Larva in the family Carabidae, and most specifically, we suspect it is a Caterpillar Hunter.

Letter 41 – Unnecessary Carnage: Caterpillar Hunter Larva

Subject: identify bug
Location: plymouth mass
July 17, 2016 10:18 am
Just wondering what type of bug this is
Signature: lara killen

Dear Lara,
This is the larva of a Caterpillar Hunter, one of the Ground Beetles in the genus Calosoma.  It looks like someone killed it, so we are tagging this posting with Unnecessary Carnage.  Many people kill insects with which they are unfamiliar out of irrational fear. 

This is a beneficial species and we hope that should you encounter another in the future, you will let it survive to eat caterpillars.  Caterpillar Hunters are important natural control agents for Gypsy Moths and others.