Quick Guide to Bess Beetles: Understanding These Unique Insects

The Bess Beetle, also known as the Betsy Beetle or Patent Leather Beetle, is a fascinating insect found in rotting wood.

With over 500 species worldwide, these beetles play a crucial role in breaking down decaying wood and recycling nutrients back into the ecosystem.

One notable characteristic of these beetles is the “kissy” sound they produce, which is believed to have inspired their name.

Bess Beetle Basics

These beetles can grow up to 1.5 inches long and are primarily found in the tropics, with only two species in temperate regions: Odontotaenius disjunctus in the eastern United States and Cylindrocaulus patalis in Japan.

In their natural habitat, Bess Beetles live in rotting wood, sharing the space with their larvae. The adult beetles help their offspring by chewing the wood and preparing it for them to eat.

Bess Beetles also have an interesting relationship with mites. Mites are commonly found hitching a ride on the beetles, although the exact nature of their relationship is still not completely understood.

Overall, Bess Beetles are essential contributors to nutrient cycling and provide an intriguing example of insect behavior and ecology.

Bess Beetle Basics

Species and Classification

Bess beetles belong to the family Passalidae, which is part of the order Coleoptera in the class Insecta. They are arthropods and closely related to scarab beetles and lucanidae1.

There is only one species of bess beetle found in Kentucky, Odontotaenius disjunctus2. This species is commonly known as the horned passalus or passalid.

Physical Characteristics

Bess beetles are quite interesting due to their unique features:

  • Adults measure about 1 ½ inches (4 cm) in length3
  • They have a shiny, black appearance2
  • Adults possess distinct horns on their heads1

Comparing bess beetles to their close relative, the scarab beetles:

FeatureBess BeetlesScarab Beetles
Size1 ½ inches (4 cm)Varies (0.08-6.7 inches)
AppearanceShiny, blackVaries (black, metallic)
Horns/ProjectionsOn their headsOn heads and/or thoraxes
HabitatDecaying woodDung, soil, vegetation

Life Cycle and Behavior

Eggs and Larvae

Bess beetles, also known as horned passalus beetles, have a unique life cycle that begins with eggs.

Female beetles lay small, white eggs in decaying logs, where they hatch into larvae after about two weeks. The larvae have soft, white bodies and feed on the surrounding decaying wood.

Characteristics of Bess Beetle Larvae:

  • White, soft bodies
  • Feed on decaying wood
  • Undergo complete metamorphosis

Pupal Stage

After the larvae grow, they enter the pupal stage. During this phase, they develop inside specialized protective chambers called pupal cells.

This stage lasts for about one month. Here, they transform into adults, developing crucial features like:

  • Hard exoskeleton
  • Elytra (wing covers)
  • Mandibles (jaws)

Adult Phase

Once metamorphosis is complete, the adult bess beetles emerge from their pupal cells.

They have a dark, shiny exoskeleton and are well-equipped for life in decaying logs. Adult bess beetles are largely herbivorous, feeding on fungus-infested wood.

Features of Adult Bess Beetles:

  • Hard, shiny exoskeleton
  • Elytra for wing protection
  • Powerful mandibles

Family Groups and Social Behavior

Bess beetles live in family groups within their decaying log habitats. These groups consist of adult beetles, larvae, and pupae.

They are known for their social behavior, which is uncommon among beetles. Adult bess beetles even assist larvae by pre-chewing their food, making it easier for the young insects to consume.

Social Behaviors of Bess Beetles:

  • Live in family groups
  • Adults care for larvae
  • Unusual social behavior among beetles

In comparison to other beetles, the bess beetle’s life cycle and social behaviors are quite distinct. The table below highlights the key differences:

CharacteristicBess BeetleOther Beetles
Complete MetamorphosisYesYes
Social BehaviorYesRare
Family Group LivingYesUncommon
HabitatDecaying logsVaries by species

Habitats and Distribution

North America

The Bess Beetle, also known as the Horned Passalus, can be found in deciduous woodlands across North America, particularly in areas where hardwood logs are prevalent 1.

These beetles make their homes in rotting logs of oak, hickory, and maple trees2.

  • Habitats: Deciduous woodlands
  • Common Trees: Oak, hickory, and maple


In the tropics, Bess Beetles are endemic to forests, often residing on the forest floor3. They thrive in areas with abundant decaying wood as they consume the rotting material for nourishment4.


  • Found on the forest floor
  • Consume decaying wood for nourishment
LocationHabitatCommon Trees for Rotting Logs
North AmericaDeciduous WoodlandsOak, hickory, maple
TropicsForest floorVarious tropical tree species

Diet and Nutrition

Feeding Habits

Bess beetles are known for their unique diet, which primarily consists of wood.

The larvae feed on rotting wood, breaking it down into small particles called pulp and frass. This diet is rich in cellulose but lacks certain essential nutrients.

Symbiosis with Fungi and Bacteria

To overcome the nutrient limitations of their diet, Bess beetles have established a symbiotic relationship with fungi and bacteria.

These microorganisms live in the beetles’ digestive system and help process cellulose-rich foods.


  • Bess beetles are found in decomposing logs, where they thrive on the rotting wood.
  • Certain fungi and bacteria in the beetle’s gut produce enzymes that help break down complex cellulose molecules.

Comparison Table

Feeding HabitsSymbiosis with Microorganisms
Wood-based dietKey to overcoming nutritional limitations
Primary food is rotting woodInvolves fungi and bacteria
Results in pulp and frassHelps digest cellulose-rich foods


  • Feed on wood, specifically rotting wood.
  • Digestive symbiosis with fungi and bacteria.
  • Process cellulose-rich foods efficiently.

Pros and Cons


  • Bess beetles play a vital role in breaking down deadwood and recycling nutrients in their ecosystem.
  • Their interaction with fungi and bacteria may offer insights into efficient cellulose processing, which could be beneficial for industries such as biofuel production.


  • Bess beetles’ feeding habits can be detrimental to wooden structures, leading to structural damage if infestations occur.

Communication and Defense


Bess beetles use a unique method of communication called stridulation.

They create sounds by rubbing body parts together, often producing a squeaking sound. Some key aspects of Bess beetle stridulation are:

  • Involves interaction between the abdomen and wings
  • Used for communication within the colony
  • May aid in locating nestmates

For example, Bess beetle larvae produce a begging call with their hind- and middle-pairs of legs to communicate with the adults.

This call helps adults identify the location and needs of their offspring.

Interactions with Intruders

Bess beetles have a shiny, hard exoskeleton that can protect them from predators and other dangers.

However, they rely on communicating and working together to deter intruders. Key interactions with intruders include:

  • Alerting nestmates through stridulation
  • Aggregating around the intruder
  • Biting the intruder with strong mandibles

The combination of sound, shiny exoskeleton, and group defense makes Bess beetles well-equipped to handle potential threats.

FeaturesBess BeetleCompeting Insects
Communication MethodStridulationVaries (e.g. pheromones, audible sounds)
ExoskeletonHard and shinyMay vary in hardness and reflectivity
Group DefenseYes, aggregation and bitingVaries among species

Bess Beetles in Science and Education

Research Contributions

Bess beetles, also known as bessbugs or horned passalus beetles, have made significant contributions to science.

They play a crucial role in ecosystems by recycling rotting wood. Researchers study Bess beetles to better understand:

  • Metamorphosis: Bess beetles undergo a complete metamorphosis, from egg to larva to pupa, and finally to adult.
  • Communication: Bess beetles are known for their vocalizations, making them an ideal subject for studying insect communication.

Bess Beetles as Classroom Pets

Many classrooms have adopted Bess beetles as pets because:

  • Low maintenance: They require minimal care, allowing students to focus on observation and learning.
  • Harmless: They are not toxic and do not bite or sting, making them safe for children to handle.
  • Educational opportunity: Students can learn about insect life cycles, metamorphosis, and the importance of decomposers in ecosystems.

Passalid Beetle
Passalid Beetle

Benefits of Bess Beetles in Classrooms

  • Low-maintenance and cost-effective
  • Safe for children to handle
  • Provides hands-on learning experience


  • Bess beetles need a suitable habitat: a container with rotting wood
  • Proper hygiene is essential: washing hands after handling them

Bess Beetles vs. Other Classroom Pets

Bess BeetlesOther Classroom Pets
Low-maintenanceMay require more care
Non-toxic and harmlessSome may be aggressive
Educational opportunitiesMay not offer the same experience


The Bess Beetle, often referred to as the Betsy Beetle or Patent Leather Beetle, is a remarkable insect that resides in decaying wood.

With a global presence of over 500 species, these beetles are instrumental in decomposing wood and reintroducing nutrients into ecosystems.

They are recognized for the unique “kissy” sounds they produce. Found predominantly in tropical regions, only two species are identified in temperate areas.

Bess Beetles cohabit with their larvae in rotting wood, with adults aiding their young by pre-processing the wood for consumption.

Their symbiotic relationship with mites remains a subject of study. These beetles exemplify the intricate balance of nature, showcasing unique behaviors and ecological contributions.


  1. Horned Passalus (Bess) Beetle – Field Station 2 3

  2. Bess Beetles of Kentucky – University of Kentucky Entomology 2 3

  3. Bess Beetles | Science Literacy and Outreach | Nebraska 2

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 – Most Parental Beetles in the World: Patent Leather Beetles from Costa Rica

Subject: Costa Rican Beetle
Location: Chachagua, Costa Rica
January 2, 2014 12:02 pm
I found this bug running pretty quickly on a cement path near our cabin in Chachagua, Costa Rica. I think i’ve seen it on your site before but i can’t seem to find it. I took this picture last August (mid rainy season). Thanks for your help!
Signature: Sam

Patent Leather Beetle
Patent Leather Beetle

Dear Sam,
We are really happy you sent in your photos of a Patent Leather Beetle, our candidate for the most parental beetles in the world. 

They are also called Bess Beetles or Passalid Beetles, a reference to the family Passalidae to which they belong.   We need to finish cooking Squash Soup right now, so we are going to link to an old posting before we return and finish this posting.

Passalid Beetle
Passalid Beetle

I had been stumped on that for a while! Your website is great, even when I don’t need something identified it’s fun to skim through. Thanks so much!

Letter 2 – Bess Bugs

Stump Borer?
My son unearthed a big pile of these large beetles and their extra-large larvae near our woodpile. The closest I can come is the hardwood stump beetle. Is that what these are?

They are about 1.5″ long. The larvae is probably 2 inches or more. Forgot to mention in my stump borer email that I am in Maryland.
Laura Brader

Hi Laura,
We are so excited to get your photos. These are Bess Bugs, beetles in the family Passalidae. They are also known as Bess Beetles, Betsy Beetles and Patent Leather Beetles. The only species in the U.S. is also called the Horned Passalid, Odontotaenius disjunctus.

Adults eat decaying wood and they care for the grubs by feeding them pre-chewed wood. Both the adults and grubs are capable of making squeeking noises. These are social beetles, and they live in colonies with the adults caring for the young.

Letter 3 – Black Widow snares Bess Beetle

black widow with bess beetle
Location: Garner/Raleigh NC
April 28, 2011 6:49 am
Greetings! I don’t often have anything to post, but here’s some shots I took this morning of a black widow spider that lives in a crack in the brick mortar outside the front door of where I work in Garner, NC.

I noticed the web some time ago, but couldn’t tell what was in there until it came out to ’web up’ this rather large meal of what I believe to be a Bess beetle. Sure do hope it doesn’t decide to come inside!

I apologize that the one pic of the front came out so blurry, but I had to put the camera down on the ground to take it & couldn’t see the screen. I included it anyway to possibly help identify age, as I know the spots on the back mean it is younger.

Really enjoy checking out your site, and have had many chuckles over some of your replies to those ’challenged’ posters who don’t quite get the spirit of your site. Rock on!
Signature: thank God for macro lens

Black Widow Eats Bess Beetle

Dear tGfml,
We are really impressed with this incredible Food Chain documentation.  We agree that the prey is a Bess Beetle, one of the few insects that actually has family values where adults care for and feed larvae. 

Both adults and larvae are capable of making sounds by stridulation and it is believe that the sounds are a form of communication.  BugGuide has a very informative page devoted to this family of interesting beetles. 

When the Black Widow matures, she will lose all of her red spots and only the red hourglass marking under her abdomen will remain on her otherwise glossy black surface, making her a strikingly distinctive creature.  Black Widows are shy, hiding by day, though they can often be found in the open in their webs once darkness falls. 

Though they are not aggressive spiders, readers should treat Black Widows with respect as their neurotoxic venom is quite potent.  Again, BugGuide has a marvelous information page on Widow spiders.

Letter 4 – Horned Passalid Beetle

“Chirping” Beetle
Hi Bugman!
My son and I live in Salisbury, Maryland. We found the attached bug (picture) under a log in our front yard. He (or she) is very strong, and makes a chirping kind of noise when you touch it. If you please, what’s that bug?

Hi Marie,
This is a Horned Passalid Beetle, Odontotaenius disjunctus. According to BugGuide: “Lifestyle of this family is unique for beetles: live in small colonies where larvae are cared for by adults of both sexes. Long life cycle, apparently more than one year. Larvae eat a rotting wood prechewed by adults.

(Some references state larvae eat feces of adults as well.) Larvae and adults also cannibalize injured larvae. Adults reported to fly very seldom. Adults are found at lights on occasion, despite statements in several sources. They may disperse by walking, but have been seen in Durham, North Carolina, to open elytra and fly briefly under lights (pers. observation, P Coin). A nuptial flight has also been observed (MacGown and MacGown, 1996).

Both adults and larvae make noises by stridulation, and this is said to serve as communication between them. Adults also stridulate when picked up, and especially, blown on. Stridulation mechanism of adults by rubbing abdomen against the wings. Larvae stridulate with reduced third pair of legs–these scratch against other legs.”

Letter 5 – Passalid Beetle

Subject: Beetle
Location: South Carolina
September 28, 2015 11:36 am
I need to know what kind of beetle I found in the woods of South Carolina during September please. Will you figure it out?
Signature: Lucas Prickett

Passalid Beetle
Passalid Beetle

Dear Lucas,
This is a Bess Beetle or Passalid Beetle, a species that lives in rotted wood.  According to BugGuide, they have an “Unusual (for beetles) subsocial lifestyle. Adults and larvae live together in family groups in galleries excavated in rotting wood by adults.

Adults care for larvae, and actively feed them prechewed food. Both adults and larvae stridulate, which is used for communication within the group. See Generic Guide to New World Scarab Beetles for more details.”

Letter 6 – Patent Leather Beetle

My son keeps finding these beetles in the woods under trees or under hay. I’m curious to know what do they eat? How long do they live? Do they carry germs? And What’s this beetle called? We love to look and play with them. They even have horns and fight each other.

Hi Sheri,
This is a Patent Leather Beetle, Odontotaenius disjunctus. It is from the Bessbug Family Passalidae. They are related to Stag Beetles and the most fascinating thing about them is that they live in colonies. Adults and larvae live together in galleries inside tree stumps and rotting logs.

Adults chew decaying wood and feed the larvae. They make a squeeking sound when disturbed by rubbing their wings against their backs. The larvae can also make sounds by scraping their legs against their bodies. This beetle was formerly known as Popilius disjunctus. They do not carry germs that can be passed to people.


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