Odontotaenius disjunctus

The patent-leather beetle or horned passalus (Odontotaenius disjunctus) is a saproxylic beetle in the family Passalidae (bess beetles) which can grow to just over an inch-and-a-half long, weigh 1-2 grams and are capable of pulling 50 times their own weight.[1] They have been used to study several aspects of general family characteristics since the early 1900s but remain a relatively unknown species within the diverse Coleoptera order.

Patent-leather beetle
Scientific classification edit
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Family: Passalidae
Genus: Odontotaenius
O. disjunctus
Binomial name
Odontotaenius disjunctus
(Illiger, 1800)
  • Passalus disjunctus
  • Popilius disjunctus
  • Passalus cornutus Fabricius, 1801


O. disjunctus is most commonly found in climates with higher humidity, mainly in the warmer parts of both hemispheres, and also widely distributed in temperate North American forests.[2] O. disjunctus beetles are usually found under, or inside, old logs or stumps and are rarely observed outside of their wooden habitats.[citation needed]

General life historyEdit

These beetles can be found in rotting logs (oak and hickory especially), this specific locale offers unique benefits in regards to protection from predators and external abiotic factors such temperature and precipitation. There is a level of stability with the two factors mentioned, the water retention in the wood helps to keep temperatures stable while aiding in further decomposition of the log itself.[2] The regulation of this environment allows for both day and night activity.[2] Larvae can reach adulthood in as little as 3 months due to a rich food source, with the average lifespan of an adulthood being up to one year.[3] Adults are only found outside of their log when they are searching for a new mate, or a new log in which to burrow.[3] Daily movements tend to be limited to within their log, any movements outside of the log are not as predictable and occur much less frequently.[4]


These beetles are shiny black, and have many long grooves on their elytra. They have a small horn between their eyes, and clubbed antennae. Females and males are difficult to distinguish based on external appearances alone.[2] There appears to be no sexual dimorphism between the two sexes, both tend to be equal in size and overall strength capabilities.[5] large size may be in part a result of exploiting a niche that provides an unlimited food source of rotting wood material.[2] Although flight is possible, these beetles predominantly walk as their main form of locomotion, they will walk long distances rather than flying.[6] Parasitic infections are common but not well known, external and internal parasites have been documented.[7] A nematode parasite, Chondronema passali, inhabits the abdominal cavity has been shown to effect stress responses in these beetles, although the results are relatively small, they do show that O. disjunctus is not only infected by parasites but are negatively impacted by them.[7] Males will often compete for females and territory like most beetle species, using their horn-like structure to flip and overturn their opponents. The strength of these beetles also tends to increase in times of stress, however, even in times without stimulation male beetles will exert an impressive amount of force onto a target.[1]

Feeding habitsEdit

Patent-leather beetles like to eat logs of certain trees, in which the wood is dead and decaying. They eat deciduous trees, such as oaks and elm. Wood inhabited by these beetles is usually well decomposed and falls apart readily. This unique food source prevents competition as these beetles have chosen a food source that is not highly sought after by other organisms due to the material being indigestible for most.[2] Adults feed primarily on wood, while larvae stages eat materials composed of fungi, wood and parental secretions.[2] Burrowing within rotting logs offers the triturated wood that is a staple in the diet of these beetles, this wood is consumed widely by the males and then further broken down through the digestive tract, and eventually expelled for the eventual re- consumption by all family members.[3]

Social systemsEdit

When disturbed, adults can produce a squeaking sound by rubbing their wings on the abdomen. This is called stridulation, and is often easy to hear, both adult and larvae are capable of producing these sounds.[2] This is used for communication within the colony, to communicate danger, courtship, disturbance and solo activities.[8][6] These four general categories can be further examined into more specific signals and patterns.[6] The acoustic repertoire of O. disjunctus can be broken down into bars, pulses and phonatomes, these are used to identify intra- and interspecific variations.[8] These sounds are produced specifically from when areas of the sixth abdominal tergite rasp against an area on the ventral side of each folded metathoracic wing.[6]

Many patent-leather beetles may live together in a colony in the same log and several colonies may be found within the same rotting log depending on the size.[6]However, only one pair of beetles is typically found in a single tunnel/burrow system, but a single large log may offer space for multiple pairs to be present.[3]


These beetles make tunnels in the wood; inside the galleries, the beetles will mate, lay eggs, and watch over their offspring.[2] The adults feed the larvae a chewed-up mixture of wood chips and feces. The larvae cannot feed themselves and take a year to develop. Being presocial beetles, the larvae are typically taken care of by the parents and young offspring.[6] This cooperative brood care is beneficial to all individuals involved, larvae receive optimal care and young adults are able remain in the burrow to increase fitness and wait for favorable conditions before exiting the log.[9]

Offspring rely heavily on parental care for protection and nourishment, food is mixed with secretions by the parent before the larvae can feed.[2] Reproduction appears to be affected by seasonality, with summer months being the time in which females lay majority of their eggs.[2] O. disjunctus remain in monogamous pairs, during the breeding season (early spring until late summer) they will repeatedly copulate and produce anywhere from 20-35 eggs over the time period.[3] Offspring remain in the parental tunnel for the rest of the year, overwinter, and then disperse in the following late spring.[3] Infanticidal behavior has been observed, and is most likely to occur in the event of a burrow take over by a male or female that has not yet had the chance to mate due to limited access to an empty burrow.[3]

Anthropological impactsEdit

The patent-leather beetle is considered beneficial in its activities to decompose dead wood, and is harmless to humans. The increase in habitat loss due to deforestation for agriculture has caused a decline in populations as they do not react well to fragmentation.[3] Studies reveal that a decrease in suitable habitat and increased open areas between forests have been the two leading causes of population decline and potential extirpation of some areas.[3] Shrinking habitat would also cause an increase in competition and infanticidal behaviors, further straining reproductive success.[4]



  1. ^ a b Davis, Andrew K. (2014). "Lifting Capacity of Horned Passalus Beetles During Passive and Stressed States". Journal of Insect Behavior. 27 (4): 496–502. doi:10.1007/s10905-014-9444-6. ISSN 0892-7553.
  2. ^ a b c d e f g h i j k Pearse, A. S.; Patterson, Marguerite T.; Rankin, John S.; Wharton, G. W. (1936). "The Ecology of Passalus cornutus Fabricius, a Beetle which Lives in Rotting Logs". Ecological Monographs. 6 (4): 455–490. doi:10.2307/1943239. ISSN 0012-9615. JSTOR 1943239.
  3. ^ a b c d e f g h i King, Andrew; Fashing, Norman (2007). "Infanticidal Behavior in the Subsocial Beetle Odontotaenius disjunctus (Illiger) (Coleoptera: Passalidae)". Journal of Insect Behavior. 20 (6): 527–536. doi:10.1007/s10905-007-9094-z. ISSN 0892-7553.
  4. ^ a b Jackson, Heather B.; Baum, Kristen A.; Cronin, James T. (2012). "From logs to landscapes: determining the scale of ecological processes affecting the incidence of a saproxylic beetle". Ecological Entomology. 37 (3): 233–243. doi:10.1111/j.1365-2311.2012.01355.x. ISSN 0307-6946.
  5. ^ J., Davis, Andrew K. Attarha, Barrett Piefke, Taylor (2013). Measuring the Strength of the Horned Passalus Beetle, Odontotaenius disjunctus: Revisiting an Old Topic with Modern Technology. University of Wisconsin Library. OCLC 908655329.
  6. ^ a b c d e f Buchler, E.R.; Wright, T.B.; Brown, E.D. (1981). "On the functions of stridulation by the passalid beetle Odontotaenius disjunctus (Coleoptera: Passalidae)". Animal Behaviour. 29 (2): 483–486. doi:10.1016/s0003-3472(81)80108-x. ISSN 0003-3472.
  7. ^ a b Davis, Andrew; Coogler, Brandon; Johnson, Isaac (2017). "The Heartrate Reaction to Acute Stress in Horned Passalus Beetles (Odontotaenius disjunctus) is Negatively Affected by a Naturally-Occurring Nematode Parasite". Insects. 8 (4): 110. doi:10.3390/insects8040110. ISSN 2075-4450. PMC 5746793. PMID 29057831.
  8. ^ a b Schuster, Jack C. (1983). "Acoustical Signals of Passalid Beetles: Complex Repertoires". The Florida Entomologist. 66 (4): 486–496. doi:10.2307/3494020. ISSN 0015-4040. JSTOR 3494020.
  9. ^ Dillard, J. R.; Maigret, T. A. (2017). "Delayed dispersal and prolonged brood care in a family-living beetle". Journal of Evolutionary Biology. 30 (12): 2230–2243. doi:10.1111/jeb.13190. ISSN 1010-061X. PMID 28981168.

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