Brown Prionid: Exploring Their World

The brown prionid, also known as Orthosoma brunneum, is a fascinating insect belonging to the longhorn beetle family.

Not only are they an exciting discovery for bug enthusiasts, but they also play a vital role in the ecosystem.

Brown prionids are known for their distinct elongated antennae, which make them easily identifiable.

These beetles are primarily found in the wooded areas of North America, where they contribute to the natural process of breaking down and recycling dead wood material.

In their natural habitat, brown prionids have certain advantages and disadvantages.

These beetles assist in decomposing wood, providing essential nutrients to the soil. However, on the downside, they can sometimes damage healthy trees if their population increases uncontrollably.

Brown Prionid: Basic Information

Classification and Scientific Name

The Brown Prionid (Orthosoma brunneum) belongs to the order Coleoptera and the family Cerambycidae. Specifically, it falls under:

  • Kingdom: Animalia
  • Phylum: Arthropoda
  • Class: Insecta
  • Order: Coleoptera
  • Family: Cerambycidae
  • Subfamily: Prioninae
  • Tribe: Prionini

Physical Description

The Brown Prionid is known for its distinct antennae. These beetles have:

  • Brown coloration
  • Elongated body shape
  • Body length: 20-50mm
  • Wing patterns: Brown with variable markings

Physical features of the Brown Prionid include:

  • Long and straight antennae
  • Robust body structure
  • Its mandibles are Large and curved

The bug uses its large mandibles for fighting and mating. Their antennae are especially noticeable due to their length and segmentation.

Compared to other beetles in the Cerambycidae family, the Brown Prionid’s antennae are relatively shorter.

Distinctive Sound

The Brown Prionid is known for its squeaking sound. This sound is produced using a method called stridulation:

  • Rubbing its wings against its abdomen
  • Utilized for communication and attracting mates

Life Cycle and Behavior

Eggs and Larvae

The life cycle of the brown prionid begins with the female laying eggs. These eggs are typically laid near decaying wood or roots of trees, like oaks.

Upon hatching, the larvae emerge and start feeding on roots and decaying wood. Some key characteristics of the larvae are:

  • Creamy white color
  • C-shaped body
  • Well-developed mandibles

Larvae prefer feeding on the roots of various trees and shrubs, providing them with essential nutrients.

Pupa and Adult

After reaching a certain size, the larvae undergo pupation and transform into pupae.

Pupation occurs mainly in the soil, near the food source. Key features of the brown prionid pupa include:

  • Exarate (free) appendages
  • Inactive and immobile stage

The pupal stage is followed by the emergence of adults. Adult brown prionid beetles are nocturnal, meaning they are active during the night.

Some features of the adult brown prionid include:

  • Brownish-black color
  • Robust body, measuring up to 2 inches in length
  • Attracted to light sources
Life Stage Characteristics
Egg Laid near decaying wood or roots of trees, like oaks
Larva Creamy white, C-shaped, feed on roots and decaying wood
Pupa Exarate appendages, inactive, mainly in the soil near a food source
Adult Brownish-black, robust body, nocturnal, attracted to light sources

The typical lifespan of a brown prionid beetle ranges from one to two years, depending on the availability of food and environmental conditions.

Habitat and Distribution

Native Range

The brown prionid (Orthosoma brunneum) is a native species primarily found in North America. Its range extends from Maryland in the north to Howard County in the south

This beetle thrives in areas with decaying wood, especially moist and rotting wood, which is essential for its growth and development.

Habitats

Brown prionids prefer habitats with abundant decaying wood, which they use for shelter, reproduction, and as a source of food. Some key habitat features include:

  • Moist: Brown prionids require moisture to survive, and they can be found residing in damp and decaying wood.
  • Decaying Wood: They are commonly found in environments with ample decaying wood, such as forests and woodlands.

Some examples of their preferred habitats include:

  1. Forests with rotting logs
  2. Old lumber piles
  3. Tree stumps in various stages of decay

Brown prionids can sometimes be found in residential areas if there is a sufficient abundance of decaying wood.

The brown prionid’s native habitat is essential for its survival, and maintaining a healthy ecosystem with decaying wood ensures their continued existence.

Diet, Damage, and Predators

Feeding Habits

The brown prionid beetle feeds primarily on decaying wood, plant roots, and sometimes bark. It is commonly found in forests and wooded areas.

  • Diet includes:
    • Decaying wood
    • Plant roots
    • Bark

Potential Harm

Brown prionid beetles can cause minor damage to trees and plants due to their feeding habits. However, they are not considered a significant threat to forests or agriculture.

  • Minor damage to:
    • Trees
    • Plants

Natural Predators

Brown prionid beetles have several natural predators, which help control their population in the ecosystem.

  • Predators include:
    • Birds
    • Small mammals
    • Flies

For instance, certain fly species lay eggs in the larval stage of the brown prionid beetles, consuming and limiting their population growth.

Human Interaction

The Brown Prionid beetle, while primarily a dweller of forests and wooded areas, occasionally comes into contact with humans, especially in regions where their habitats overlap with populated areas. Here’s a closer look at these interactions:

Pest or Friend?

Generally, Brown Prionids are not considered harmful pests to humans. They don’t bite or sting, and their primary diet consists of decaying wood and plant roots.

However, in areas where they are abundant, their larvae might cause minor damage to tree roots or garden plants.

On the positive side, by feeding on decaying wood, they play a role in the natural decomposition process, recycling nutrients back into the soil.

Attraction to Lights

Like many beetle species, Brown Prionids are attracted to artificial lights. It’s not uncommon for residents in areas with a significant Brown Prionid population to find these beetles buzzing around porch lights or street lamps during the night.

This can sometimes lead to accidental home invasions, especially during warmer months when windows and doors are frequently left open.

Conclusion

The brown prionid, scientifically termed as Orthosoma brunneum, is a captivating member of the longhorn beetle family, predominantly found in North America’s wooded regions.

Recognizable by its elongated antennae and brown hue, this beetle plays a pivotal role in the ecosystem by aiding in the decomposition of dead wood.

While they do have a penchant for decaying wood, plant roots, and bark, their impact on trees and plants is relatively minor. However, their presence can sometimes be a concern if their population surges uncontrollably.

By understanding their life cycle, habitat preferences, and behavior, we can appreciate their role in nature and manage their presence effectively.

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.

93 thoughts on “Brown Prionid: Exploring Their World”

  1. we found a orthosoma burneum in our pool today. He is now resting in my 7 year old son’s bug trap overnight. He seems to burrow in the soil. Will he be okay overnight with roots and soil?
    Buggy brewers, west hartford, CT

    Reply
  2. That’s definitely quite strange, and fun to try to figure out, but I do feel sad for the poor little thing. If it was windy and the windows were open, it could have been blown in from somewhere. Sometimes birds will just eat the bodies of insects, and regurgitate the rest of it up because it gets caught in their throat.

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  3. I found one of these here in Abilene, TX! it’s huge! My miniature pincher was barking like crazy at something in the grass. Upon further investigation it was the biggest bug I’ve ever seen! It is about 3″ long (the size of my Dodge truck key).

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  4. I -THINK- I saw another one of these guys about 25 miles south of Boston, MA. Only saw him from beneath, though, because frankly after he thumped against my window I locked up the house tight, shut the shades, and cried for a bit.

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  5. I just found one of these on my screen door here in Orange, Ct. 7-19 I have not seen one of these before. Are they known to be in Ct? It’s beautiful and very large!!

    Reply
    • Connecticut is within the range of the Brown Prionid, but interestingly, a sighting map based on BugGuide submissions does not include any Connecticut sightings. You should submit an image to BugGuide to color in the map. There might be other factors in the dearth of sightings in Connecticut, but we suspect it is because of a lack of submissions rather than an environmental factor, however, ranges of native species often contain gaps in sightings.

      Reply
  6. I just caught my 10 month old schnauzer pup “playing” with one of these in the backyard. I’ve never, never seen one before and I can’t figure out where the little darlin’ found it. Schnauzers are great sniffers, so she probably chased it down from under some shrubs Thank you for your website! I live in Suffolk County Long Island.

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  7. Just found one of these crawling up our front porch wall in Reading, Pa. Got a great picture of it. How do I send it to you or post it? I’ve seen similar sawyer type beetles but never one of these.

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  8. Ah! That is definitely him. I was looking at Hardwood Root borers and Pine Sawyers, which were all similar, but none looked 100% like the one I’d found. This one certainly is!

    Not to worry about the state of the prionid, I released him into the remains of a fallen tree an hour or so after sending this in and taking measurements. He’s safe and sound. It’s good to know he’s a native species, so I’m glad I saved him from my mother’s angry boot that night.

    Thank you! 🙂

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  9. Ah! That is definitely him. I was looking at Hardwood Root borers and Pine Sawyers, which were all similar, but none looked 100% like the one I’d found. This one certainly is!

    Not to worry about the state of the prionid, I released him into the remains of a fallen tree an hour or so after sending this in and taking measurements. He’s safe and sound. It’s good to know he’s a native species, so I’m glad I saved him from my mother’s angry boot that night.

    Thank you! 🙂

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  10. Wow! I just had one on my screen door as well! Freaked me out, thought it was a female rhino beetle. The dog was put-off by it sitting there. It must be their time of year. I, too, have lived in my area (Franklin, MA) for about 3 decades and had not recalled seeing one before. I was not afraid but I was taken aback by it. It is pretty awesome.

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  11. Found one running across my family room floor. I also thought it was a roach,,,which I had never had in our home. We do have about 80 trees/shrubs on our property along with some rotting stumps. Our home is about 120 yrs ofls with clapboard siding. could these become a problem? We just had our home painted. the painting crew said that our property has the most unusual insects that they’ve ever seen. Now I’m worried.

    Reply
    • Brown Prionids will not damage your home. If you are paranoid about insects, perhaps that is not the ideal location for you. We would be more than happy to attempt to identify any insects that concern you if you email images using our Ask What’s That Bug? form. What is ofls? Some cryptic form of “awfuls” perhaps?

      Reply
  12. Just had one of these scare us while sitting on our patio. Large Brown big antenna and loud. We are in Thousand Oaks, CA.

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    • That is a very good possibility, though they generally appear later in the year. This was a warm winter in California, so that might have some influence on an earlier than typical appearance.

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  13. Never seen one in my 60 yrs on Earth. Nobody I showed it to had seen one either–new to Pennsylvania? Was found dead on sidewalk outside office bldg doors. Had to look it up to find out what the h the thing is. Almost 2″ long makes it a scary looking creature.

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  14. Found a swarm of bee-like insects buzzing around cellar window. Sound like bees, shaped like bees, about size of a honey bee, but appeared black with touches of white. Looked for it in my insect book but unable to find. Any ideas?

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  15. Is this bug also in Canada? It’s where I live and one bit me on the back while I was on my computer… It looks really close to the picture but I don’t know if they’re in Canada and if it’s the right bug. Help?

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  16. I’ve found three of these in my bedroom in the past week. Although I assumed they weren’t considered harmful, one was huge (about 1.5-2 inches) and the others were a little less than an inch so I’m worried that the larger one laid eggs somewhere. Are they invasive? Any tips on making sure there are no more in my room?

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  17. One of these was found in yakima washington in a friends swimming pool. It looks like theyre mostly found in the east coast. Just wondering if these guys have changed migratory paths

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  18. Thanks for the explanation, I understand the difference now. At least I got the brown part right. He (?) was very handsome.

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  19. I just found a brown Prionid on my screen door here in Grand Rapids MI. it was as big as my thumb – almost honey color.

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  20. Hey, I live in New haven, CT and have found 2 huge ones (about an inch) of these and 2-3 smaller ones about 1/2 an inch in my house over the last week or so, our house was built in 1900 as well and is down by a river… do they click and try to bounce away when you try to get them or is that just something they’re doing for me? scares the hell out of me lol

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  21. Sad that I just killed one while freaking out mistaking it for a roach ( palmetto bug) after just returning from Florida.. I’m here in Massachusetts , Cape Cod and I may have seen one before but not many ..

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  22. Just found one in my dogs feeding bowl of all places. Got good picture, very impressive, large beauty. About 2″ and bit through a twig I put by it’s mandibles.

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  23. Dear sir

    Hello
    I am looking for long horn beetles in puerto Rico. And want to buy dried insects there.
    For more information, contack me by my e-mail. Thank you very much

    Reply
  24. Dear sir

    Hello
    I am looking for long horn beetles in puerto Rico. And want to buy dried insects there.
    For more information, contack me by my e-mail. Thank you very much

    Reply
  25. Just saw one of these on an outside window. I absolutely cannot stand bugs and this thing is the stuff of nightmares for me! It was at least 2″ long. We live in a rural town in Tennessee, in a neighborhood. I have never seen one of these in my life. Do they fly? If it’s hot outside, could it come in the house or will it stay outside? It eventually got off the screen somehow and I next saw it crawling on the patio. I will probably have a heart attack if one of these come in my house. If I saw ONE, does that mean there are others? If so, where would they be found?

    Reply
    • They are attracted to lights, but they are not interested in living indoors. If one is found in the house, it was an accidental intrusion.

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  26. I just found one on the side of my house in Long Island, New York. I’ve read they live in telephone poles and such. I recently found large holes in the pole for my mailbox, which is like a short telephone pole. There were 5 holes, each perfectly round and 3/4-1″ in diameter. Could this be from these beetles or something else, like a carpenter bee?

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  27. I live in NS Canada, and found two of these in a bucket of water the other morning. What terrifying looking bugs! Are they out during certain months in the summer, kind of like June Bugs?

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  28. I just found a large one of these guys on my front porch in Burlington Vermont. When I touched him he began making “hissing” noises and scurrying away.

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  29. Just had one fly up to our porch!! (Southwestern Wisconsin) I’ve never seen one before. SO BIG!!
    I caught it in a glass and let it go about 3 blocks away 🙂

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  30. Just had one fly up to our porch!! (Southwestern Wisconsin) I’ve never seen one before. SO BIG!!
    I caught it in a glass and let it go about 3 blocks away 🙂

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  31. my mother has encountered this thing crawling in her shirt last night. what do we do. do we kill it. and are there possibly more? i would post a pic of it but i cant.

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  32. One of these flew into the house earlier in Mount Airy, NC. Finally got him and put him out. I’ll be danged if it wasn’t right back in the window in less than 3 minutes. Scared the life out of me. Second time I got it the sucker bit me! Sadly, it’s dead. I’d never seen one and didn’t want to risk it biting one of the children. I believe I know why I saw it though. It’s a “new” old house, unkept yard and garden. We overhauled today and that meant moving rotten wood in the yard, cutting foot and a half grass, etc. Lots of weird bugs running around now that we weren’t seeing before.

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  33. My son and I saw this thing moving across my living room rug at 11;00 at night. We freaked out and caught it. Over 2 inches long. It is a brown prionid beetle. I’m concerned about it leaving others in the house. I have alot of old tree around my house and a rotting stump that I have been picking at. Do I kill it or let the birds eat it. Hopefully no young ones in my house again. I’m vacuuming often again.

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  34. Hi I just found one in Bucks County Pennsylvania hiding under some fiber pots. When it was exposed to the sun it acted like a vampire and scurried to find a hiding place. When I tried to help it to a better spot it hissed at me. It is ominous and I almost wanted to eliminate it due to its cockroach like appearance but I talked myself out of it after inspecting the tail end and antenna. I have a very important question though, is this a good or bad bug for the garden? what does it eat? I have pictures if you are interested.

    Reply
    • The hissing sound you heard is an action known as stridulation and is produced when the insect rubs parts of its body together. In our opinion, the Brown Prionid is a benign insect, and according to BugGuide: “Breeds in poles, roots(?) in contact with wet ground” indicating the larvae feed on rotting wood.

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  35. I live in Staten Island, NYC. I live near old trees and wetlands — I see these a few times a year in the summer. They get in my house every couple of years — but last night I was awoke by one CRAWLING ON MY CHEEK IN BED IN THE DARK. I jumped up and turned the lights on and saw it crawling in my WHITE sheets — I was horrified — but I stayed calm because I knew I had to catch him — which I finally did. He’s currently in my bedroom in a glass jar. I’ll post photos if anyone is interested.

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  36. Was just awoken by the very same Brown Prionid and am now wide awake. Freaked out and stepped on it and many small white eggs were seen; about the size of a sesame seed but rice looking. Allentown PA here. Used the app Picture Insect to identify it. So much for tonight’s sleep!

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  37. Awoke at 530 am to this guy and when I got close he chirped and flew off. I have a child here so I spent 2 hours looking for him to no avail. I fell back asleep and bam just woke at 830 to him flying around my room. Finally found what he was in here thanks. Mansfield, Ohio it’s been in the 90’s here.

    Why is there barely any info on them out there??

    Reply
    • According to American Insects: “Orthosoma brunneum is most often noticed when it blunders into the human world, attracted to houses by electric lights.” Now that you have a scientific name, you should be able to locate additional information.

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  38. Awoke at 530 am to this guy and when I got close he chirped and flew off. I have a child here so I spent 2 hours looking for him to no avail. I fell back asleep and bam just woke at 830 to him flying around my room. Finally found what he was in here thanks. Mansfield, Ohio it’s been in the 90’s here.

    Why is there barely any info on them out there??

    Reply
  39. My brother and i were casually sitting watching Tv when a bug fell from what we thought was the ceiling. We immediately killed it and found small white seed looking things(looked like sesame seeds). We for sure thought it was a cockroach, but after further research we found out that it was a Brown Prionid Beetle. Any idea what the sesame seed looking things were? Are there any more of these beetles in my house? Should we be worried

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  40. Worker found a brown prionid crawling in his workspace, a room in the center of a large warehouse. Can’t figure out how it got in. Caught it in a cup and is returning it to some wilderness next to the building. Lititz, PA.

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  41. Just found one on my screen door and it scared the crap out of me! My husband told me it was a cockroach so I did my research – definitely a brown prionid beetle. I’m in Southern Wisconsin and this is the first I’ve seen one – and hopefully the last! Don’t worry – he looked peaceful so I let him be!

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  42. There are here in Idaho too. Biggest beetle I know of around here.

    I just got done picking one up, but buy the shell, they look like they have some fierce mandibles!

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  43. There are here in Idaho too. Biggest beetle I know of around here.

    I just got done picking one up, but buy the shell, they look like they have some fierce mandibles!

    Reply
  44. Thank you.

    The beetle I saw last night looked just like the one in the photo above, and was 2in or more long not including the antennae.

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  45. Found a dead but big dark Brown Prionid floating in a bucket of rain water earlier this week. Never saw one like this here before. – Lebanon County PA

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  46. This guy scared the crap out of me when I caught him in a plastic cup that had a bit of water in the bottom, he started squeaking and I almost had a heart attack. Didnt know the little guy had it in him. Thought he was a cockroach at first too, thank the heavens hes not. I guesz its time to release him from beetle jail lol

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  47. I had one of these fly into my bedroom window at night. It made like a squeaky noise and it was about an inch long. I’m from Hendersonville, NC.

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  48. My daughter ready for bed on a hot muggy night on her phone was visited by this huge almost 2 inch beetle. She comes screaming out of her room. She is not a bug person. After this happened 3 times i was finally able to find and catch the huge Brown Prionid. We took many pictures and let it go the next day in the woods with lots of dead Scotch Pines for her to lay eggs. Harleysville,PA.

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  49. Saw one of these today here in NJ. Impressive critter, more shiny bronze colored than dull brown. Easily 1.75″ long. Had to look him up!

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  50. We live just outside of Philadelphia. Sitting in my office doing some work and my cat is going crazy near the desk shelves. I finally look and here’s one of these beetles! Now that I can identify it. Buzzing around. Captured it in a napkin and let it go outside. How did it even get in the house? Would it have been harmful to me or my cat?

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  51. i have a tarp on the underside of my top deck for rain protection. while i was out feeding the feral cats i saw this giant brown bug on it but it was dark out..first thing when i got a flashlight and my glasses for better view i thought it was a palmetto bug since living in fla many years ago you never forget those things lol…anyway the face/head area wasnt the same and the antenna looked different but i just couldnt get a close look because i was afraid it would drop on me lol…thought id do a search of beetles in ct and this one came up right away and i believe it is what it is…i noted the head area was not the same as a palmetto before i came in to look online and when i saw a photo of this one i knew it was it…im in waterbury ct..and i also just learned that palmettos are not beetles..and why is it that i feel better knowing this is not a palmetto bug and just a giant beetle lol..id add a photo but i also have raccoon babies hanging around and when they hear the screen door they come running up looking for cat food. 🙂 thanks for posting everyone..its very helpful for someone like me who likes to research things i dont know 🙂

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  52. I found one in my house last night (Stockbridge VT). It was laying on its back, kicking its legs trying to get back up. My first impressions is that it was a huge cockroach. Until I got up close and witnessed those scary/nasty looking pinchers as a mouth. I assume he was attracted to the light and squeezed into my house through the sides of a window unit air-conditioner. My wife would have had a heart attack if she found it. Will be sealing those open areas asap!

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  53. These beetles seem to love July. I live in northern Indiana and I found a 2″brown prionid on the outside of the laundry room window tonight. We had some rain today and the night has been humid. The laundry room light was on so it was probably drawn to it. I’m glad it was on the outside of the window. They give me the creeps because they look so similar to roaches. I actually thought the one I saw was a roach at first.

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  54. 8 years later from the 2 previous posts… I’m in Indiana. Never seen one in my 58 years! Saw one yesterday and appreciate this info. That bug freaked me out!

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  55. Visited by one in our house on a hot and humid night. We have central AC but had a lot of company and doors open all day. My husband mentioned that he thought he saw something flying in the living room earlier in the evening . Huge bigger! Phoenixville, Pennsylvania

    Reply

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