An unusual house guest

I had hoped to get some garden clean-up done this weekend, but it snowed a bit:

Given the winter weather, you might wonder how I could be doing another insect story, but right now I’m hosting an extra house guest. The beetle first showed up wandering the hallway at school, near the back doorway. Carabids are generally hunters, and many of them are beneficial to us because they eat pest insects. Chances are you’ve seen the ordinary sort of brown-legged, large black ground beetle running across the sidewalk in search of prey, or maybe hanging around your porch light at night.

Carabids can be distinguished by a couple of characteristics: firstly, the pronotum (the dorsal plate of the prothorax, meaning the section on the back of the beetle that’s between the head and body) is wider than the head but narrower than the rest of the body, and secondly, on the third (hind) legs the trocanter makes a rather distinctive lobe between the femur and coxa (diagram). Like many sorts of beetles, the elytra are striated, which is a fancy way of saying that the wing-covers are grooved.

There’s certainly no lack of beetles in the world; with about 40% of the species, Coleoptera is the largest of the insect orders. But once you get to know my guest, you won’t forget it — this is one smashingly gorgeous hexapod!

The Caterpillar Hunter (Coleoptera: Carabidae, Calosoma scrutator) also has another common name, the much more exciting Fiery Searcher.

Description: a nearly 3 cm (1.25″) long beetle, with shiny dark blue legs, black antennae, a metallic navy pronotum rimmed in orange, and grooved metallic green elytra rimmed in copper-red. The beetle is photographed on graph paper, with an off-white caterpillar clenched in it’s pincers. (I put the graph paper in its cage just for better photography, because despite its flashy coloring, the predator is not very noticeable against dark soil.)

At school, I carefully scooped up the beetle and popped it into a cage for the students to view safely, because those mandibles can give a nasty bite. I also bought some “wax worms” (a type of moth caterpillar) at the pet store to feed it, but since the beetle is mostly nocturnal, it proved to be a rather boring classroom pet as it spent most of the days snoozing in a crevice between a small rock and the soil substrate in the cage. (Well, I assumed it was asleep but it’s hard to tell with animals that lack eyelids; it was alive but not moving.)

Ground beetles are so named because that’s where they live; they like the cool damp spots, and hang out underneath rocks and bark and other debrís. Females lay individual eggs in the soil, where the larvae will return to pupate. But being caterpillar hunters, they are also found climbing trees in search of gypsy moth or tent caterpillars, especially during the spring.

After a couple of uneventful (read, “boring”) weeks, I took it home. Adults can live two or three years; I’ve no idea how old this one is, but it might be here some time. Today I waggled a waxworm right in front of its jaws, which prompted a quick response. My eldest described it as a “dedicated feeder”, as the beetle spent quite a while steadily consuming the caterpillar that was nearly as long as it was. It was, I noted, also a fastidious eater, as it only ate the insides of the moth larva, finally abandoning the rumpled exoskeleton, much in the way that we leave shrimp shells on our plates. It then wandered over to the side of the cage by the desk lamp, and sat in the warmth to better digest its dinner.

Like the rest of the Thanksgiving diners, my house guest is currently snoozing off its repast.



  1. Kelsey said,

    9 June 2013 at 0:38

    we live in northern illinois, getting ready for bed last night we saw this creature sitting on our bed. we will share our bed only with our kids, beetles no. i google searched and found this article. he has currently been released into our garden area. he was scary looking and to know that it may bite, i will search our beds every night.

  2. patrick said,

    4 May 2012 at 5:13

    i live in albuquerque, nm and encountered several of these while riding through the bosque. i found your article by trying to find out what these beetles are.

  3. Brook said,

    26 April 2012 at 2:52

    Hi! I just found one of our fiery friends when I was with my students on the playground. Wow- and they are STUNNING. I couldn’t believe it was so beatiful. So i too brought it home with the intention of keeping it… It must be a teacher thing :-) Thank you for your post, otherwise I’d be at a loss as to how to begin taking care of “Dora ” (named by my students). Since its late and petstores are no longer open, I wondered if Dora might eat a moth. Not long after turning on my outdoor lights, I captured a moth, and placed it I front of Dora. She fervently grabbed it and has been happily chomping away since. So again, thank you! Dora appreciates it as well!

  4. Jessica oliver said,

    28 March 2012 at 13:21

    I too was bit by a fiery searcher last night and went searching for info as it hurt pretty bad! lol. I found your site and must say, its really interesting! thanks for the great info.

    • 9 October 2014 at 3:29

      I have to add this here in case anyone else has the same problem I did with these bugs. I was in 4th grade when I went to put on a girl scout uniform that was hanging in my closet. I felt a stinging bite. I removed the shirt and discovered a cocoon. which I put in a milk jug, and capped. within 3 hours I was covered in dots, had a fever and vomiting. I had to stay out of school for over 3 weeks to recover. the doctor said I had an allergic reaction to this bug. he also said that if I was ever bit again it would likely kill me. this isn’t something you want to give to kids to play with. you see after I got better I took the milk jug outside and dumped it out. this bug is what crawled out of it. it had gone into the cocoon of the moth to eat it and thats how it bit me in my shoulder. not everyone is allergic but I sure wouldn’t chance it again.

  5. kim said,

    6 November 2011 at 13:11

    i just moved to an apartment in a very old building. im feeding the mice poison for 3 or 4 days and i notice this beetle and he goes in where the mice are. then its in my tub getting a drink of water. its now in a butter bowl w lid. i live on the 2nd floor and there are 3. is the beetle eating the mice laying babies will i have an explosion of beetles?

    • andrea said,

      7 November 2011 at 0:17

      What kind of beetles do you have? The same as pictured, or something else? There are an incredibly large number of families and genera, not to mention species.

      How large is the beetle?
      A lot of the beetles that wander inside are Ground Beetles (Family Carabidae), which are most easily identified from the gazillions of other beetles by looking at the underside. On the hind (back) pair of legs near where they are attached to the thorax, there is an extra “lobe” (it kinda makes them look “muscular”). See this picture for an example, even if it’s not the same species of Carabid:

      If it doesn’t have that, then it’s some other type of beetle. See if this helps,
      or if you live in the U.S. take your critter in to your local Cooperative Extension Office for an ID:

      As for whether or not you’ll have more beetles, that depends upon the sexes (assuming there’s not a pregnant female) and their life histories.

      Wonderfully ambiguous answer, sorry! But at least you have some leads to work from. If you get some good close-up pix, let me kow where you live, and send them to andreasbuzzing care of my gmail account, and I’ll see what I can do …


  6. sandrar said,

    10 September 2009 at 22:11

    Hi! I was surfing and found your blog post… nice! I love your blog. :) Cheers! Sandra. R.

  7. Tina Hendricks said,

    9 September 2009 at 15:24

    I have those beetles everywhere. I have a little cage that I put things in to attract bugs for my hummingbirds, I put 2 Very ripe bananas in it hoping to get some knats for the birds. the next morning I realized that the cage looked really strange so i walked over to investigate and the beetles were having a field day with the bananas. It was almose spooky. I did think to get a pic of them it was quite interesting

  8. andrea said,

    20 June 2008 at 14:02

    A bite from any animal (including humans) has the potential to be dangerous. Your son’s bruise would simply be from the strong jaws.

    These beetles do NOT have venom, so the main concern would be from a (secondary) bacterial infection; simply wash such wounds with running water and antibacterial soap. Depending upon the person, putting a bandage on to keep dirt from getting in, or to keep them from picking at the wound may be helpful.

    And remember — many beetles (and other insects) are herbivores, or plant eaters, and pose no direct danger to us. In fact, ONLY ONE PERCENT of the million–plus species of insects are even pests!


  9. DONNA HOLTON said,

    20 June 2008 at 5:56


  10. sweetroad said,

    9 June 2008 at 23:55

    I have mealworms and my kids LOVE them! They think the beetles are great and are constantly watching them. Also, the lifecycle is relatively short so its fun to watch.

  11. qw88nb88 said,

    10 May 2008 at 17:25

    Raymee, they are predators, not herbivores. Go to a pet store and get some “wax worms” or find some caterpillars out in the yard.


  12. Raymee said,

    10 May 2008 at 13:55

    I think fiery searcher beetles are fasanating insects. I caght one the other day.
    But do they eat leaves, grass, and live under rocks? can you please answer and email me back…………….peeeeeeaaaaallllleeeeeeessssssssn

  13. K T Cat said,

    15 December 2007 at 2:34

    Great stuff!

  14. qarrtsiluni said,

    3 December 2007 at 22:05

    Thanks for an informative post about a fascinating creature.

  15. Sissy Willis said,

    3 December 2007 at 18:10

    The wicked oppressing shall cease from distressing. Thanks for a most interesting post.

%d bloggers like this: