Firebrat: All You Need to Know for Effective Identification and Control

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Firebrats are fascinating insects that often go unnoticed in our homes. These small, wingless creatures have a distinct fish-like appearance with flat, tapered bodies and overlapping scales source. They are commonly mistaken for their close relative, silverfish, but there are key differences between the two.

Adult firebrats, scientifically known as Thermobia domestica, can grow up to 3/4 inches long and typically have a darker color compared to silverfish source. Both insects share similar habits and habitats, but firebrats prefer temperatures over 90 degrees Fahrenheit and have a high humidity requirement.

Firebrat Identification and Appearance

Physical Characteristics

  • Length: up to 3/4 inch long
  • Shape: flattened, elongated, oval
  • Appendages: three long tail projections, two long antennae

Firebrats are small, wingless insects with a distinctive shape. Their flat, elongated bodies are about 1/2 inch to 3/4 inch in length. At the tip of their abdomen, there are three long tail-like projections, and they have two long, threadlike antennae 1.

Color and Scales

  • Color: gray, brown, or mottled
  • Scales: overlapping, brownish

Firebrats have a variety of colors, ranging from gray to brown, often with a mottled appearance. Their bodies are covered in overlapping scales, which contribute to their characteristic “fish-like” look 1.

Comparison Table

Feature Firebrat
Length Up to 3/4 inch
Shape Flattened, elongated
Antennae Two long, threadlike
Tail Projections Three long
Color Gray, brown, or mottled
Scales Overlapping, brownish

To sum up, firebrats are small insects that are identifiable by their unique physical features, such as their flattened bodies, elongated shape, and overlapping scales.

Firebrat Life Cycle and Habits

Eggs to Maturity

Firebrats, or Thermobia domestica, start their life as tiny eggs laid in hidden or dark spaces. Some key points about their development include:

  • Eggs hatch in about two weeks.
  • Nymphs reach maturity in about three months.

Firebrats undergo several molts during nymph stage.

Nocturnal Activity

Firebrats are nocturnal insects, which means they are active at:

  • Night
  • Hiding during the day

These insects are fast-moving and swiftly find new hiding places when disturbed. They tend to prefer dark, warm spaces. For example, firebrats enjoy living in areas:

  • Around ovens
  • Near furnaces
  • Close to boiler rooms
  • Beside fireplaces
  • Around hot insulation

In summary, firebrats have a swift life cycle, transitioning from eggs to maturity within a matter of months. Their nocturnal activity and preferences for warm, dark spaces define their habits and behavior.

Firebrat Infestation and Home Invasion

Wall Voids and Wallpaper

Firebrats are home invaders that can cause damage to various household materials. They often hide in wall voids and feast on wallpaper. A common sign of their presence is:

  • Damage to wallpaper and book bindings, such as notched edges or holes

These insects prefer warm, damp, and dark places, so areas near boilers, furnaces, and hot water pipes are more prone to infestations.

Dry Food and Cardboard Boxes

Firebrats also target pantry items and can be found in:

  • Cardboard boxes containing dry food
  • Storage areas for books and paper products

To prevent and control an infestation, consider the following steps:

  • Store food items in sealed containers
  • Reduce humidity levels by using dehumidifiers
  • Regularly inspect storage areas for signs of damage
  • Keep storage spaces neat and clean


Aspect Silverfish Firebrat
Size 1/2 to 3/4 inch 1/4 to 1/2 inch
Color Silver or pearl gray Mottled gray or brown
Habitat Cool and damp places Warm, damp, and dark places

Remember, detecting and dealing with an infestation early can help protect your home and belongings from further damage.

Food Sources and Feeding Habits

Firebrats are insects known for their appetite for starchy substances and ability to adapt well in various indoor environments. In this section, we will explore their preferred food sources and feeding habits.

Starches and Paper

Firebrats primarily consume starches, which include:

  • Paper: They have a particular fondness for books, newspapers, and cardboard.
  • Glue: Firebrats often feed on adhesives used in binding or packaging materials.

These insects prefer living in environments rich in their preferred food sources, such as libraries, storage units, and homes with cluttered paper materials.

Pet Food and Clothing

Aside from starches and paper, firebrats are also attracted to:

  • Pet food: They enjoy consuming dry pet food, especially those containing grains and cereals.
  • Clothing: Firebrats are known to feed on clothing made from natural fibers like cotton, wool, and linen.

Below is a comparison table highlighting the common food sources and preferences of firebrats:

Food Sources Examples
Starches Paper, glue, books, cardboard
Pet Food Dry dog or cat food, birdseed
Clothing Cotton, wool, linen, synthetic blends

By understanding the preferred food sources and feeding habits of firebrats, you can take appropriate measures to control and prevent their infestations within your home or property.

Firebrat Prevention and Control

Temperature and Moisture Management

Firebrats are pests that thrive in high-temperature and high-humidity environments. To prevent their growth, consider the following:

  • Use dehumidifiers to reduce humidity levels
  • Regularly inspect and fix moisture-prone areas such as pipes and drains

For example, maintaining a temperature below 90°F and a humidity level below 50% can significantly decrease firebrats’ chances of survival.

Crack and Crevice Treatment

Sealing off potential hiding places for firebrats is essential in preventing infestations. Some steps to follow are:

  • Seal cracks and gaps in walls, baseboards, and flooring
  • Close openings around plumbing and electrical installations

By taking these measures, you limit the spaces available for firebrats to hide and lay their eggs.

Insecticides and Pheromones

The use of insecticides and pheromones can help in controlling firebrat infestations. Here are some pros and cons of using these treatments:


  • Efficient in reducing firebrat populations
  • Pheromone traps are non-toxic and safe for humans and pets


  • Insecticides may not be suitable for households with children or sensitive individuals
  • Overuse of insecticides can lead to resistant firebrat populations

In conclusion, managing temperature and humidity, sealing potential hiding places, and using insecticides or pheromones are three effective strategies for preventing and controlling firebrat infestations. By following these methods, you can maintain a pest-free environment in your home.


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Reader Emails

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

Letter 1 – Firebrat


What this bug?
Hello there,
I was wondering if you could help me identify this annoyance in our household. I’ve had absolutely no luck with other sites. I’ve attached a picture for you take a look. Most of these bugs were sited by old heaters in our basement apartment. Any help would be appreciated!

Hi Rob,
You have Firebrats, Thermodia domestica, a type of Silverfish. It is a domestic species recognized by the mottled pattern. It frequents warm and even hot places, often in boiler rooms and near heaters. This habit leads to its common name.

Letter 2 – Firebrat


Bathroom Buddy!
December 6, 2009
This little critter has been hanging out in our apartment bathroom here in Lakewood, CO for quite a while…Since september of this year. He’s about 1cm long and faster than a speeding bullet when you go to squish him! He has white and black stripes and resembles an earwig. He hides underneath our radiator in the bathroom and I’m pretty sure he may be coming in through a crack in our floor. (However, we live on the top floor of our apartment building!)
I’m sure he’s not the only one of his kind, but we have only seen one or two at a time. I managed to catch this guy (affectionately named “dwight” by the roomies) a few hours ago. I stuck him in our freezer and took this picture afterwards.
I checked your website this morning and couldn’t find anything like it!
Can you ‘dentify Dwight for us?
Everli in Colorado
Lakewood, Colorado, USA


Hi Everli,
Dwight is a Firebrat, Thermobia domestica, a type of Silverfish that likes heat, which would explain Dwight’s fondness for the radiator.  According to BugGuide:  “nymphs and adults feed mostly at night on products rich in carbohydrates or protien; stored foods, glues, book bindings, and paper products may be attacked


Letter 3 – Firebrats?


I love your web site!
We recently moved into a new house in the Phoenix, AZ area and we are seeing a lot of small (1/4 to 1/2 inch) bugs in the house that look a little bit like the silverfish that I used to see back in Virginia. They are very fast runners and they like to sit high up on the walls – particularly in the corners. They are beige with 3-4 brown stripes running from side to side and they have long thin antennae and what looks like antennae off the rear of the bug as well. They are extremely soft-bodied and, when threatened, their first response is to try to crawl deeper into the corner rather than simply run.
My camera will not let me zoom in close enough to get a decent photo, so I hope my description is adequate.
Peoria, AZ

Ed. Note: Several hours later, Bob sent this email.
After reading more about silverfish and firebrats, I suspect that these are the latter. Oddly enough, we don’t find them in the damp areas of the home as much as in the dry. We do not find them in sinks or drains or in greater quantities in the bathrooms or kitchen. Right now, I can find 2 or 3 of them in the living room and each bedroom, parked at the ceilings. The house stays pretty dry (<30% humidity most of the time) and there are no signs of moisture anywhere. They do not seem to be more active at night and they do not seem to hide during the day. The body is less carrot shaped than indicated in the drawings and photos I’ve seen on the web, with a slightly more rounded rear. My wife calls them “trilobites” because of their prehistoric appearance.

Hi Bob,
I am inclined to agree that you probably have Firebrats. They are very primitive insects and your wife likening them to trilobytes is interesting.


  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. 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.

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4 Comments. Leave new

  • I found a similar bug on my brick fireplace wall. it is a solid brown, has six legs, two very long antenia, and three long antenia like tails… could this possibly be the same type bug

  • If you are looking to control this bugs, you can use a peace of corrugated cardboard and dust it well with boric acid dust. You can find the boric acid in your local Home Depot or Lowe’s or any other hardware store or even in your local supermarket some times. Same treatment for Silverfish. Also can use an aerosol sprayer can and spray the area where you see them the most and make sure is a product that leaves residual so it keeps killing them for several days. Hope this helps many.

  • AlexW, extreme entomophile
    December 19, 2017 5:23 pm

    I know you may not see this while on holiday, but here it is:

    This silverfish is Thermobia domestica, the firebrat. Bugguide’s identification section says:

    “oblong/elongate yellowish body with dark brown bands and mottled spots on the dorsal surface; stout-bodied (abdomen relatively broad-tipped and often shorter than thorax, giving an overall “chunky” appearance)”


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