Burying beetles or sexton beetles, genus Nicrophorus, are the best-known members of the family Silphidae (carrion beetles). Most of these beetles are black with red markings on the elytra (forewings). Burying beetles are true to their name—they bury the carcasses of small vertebrates such as birds and rodents as a food source for their larvae; this makes them carnivorous.[2] They are unusual among insects in that both the male and female parents take care of the brood.[3]

Burying beetle
Temporal range: Cenomanian–Recent
American burying beetle (Nicrophorus americanus)
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Family: Silphidae
Subfamily: Nicrophorinae
Tribe: Nicrophorini
Genus: Nicrophorus
Fabricius, 1775
Type species
Silpha vespillo
Synonyms[1]
List
    • Acanthopsilus Poole, 1996
    • Canthopsilus Portevin, 1914
    • Cyrtoscelis Hope, 1840
    • Eunecrophorus Semenov-Tian-Shanskiy, 1933
    • Nechrocharis Poole, 1996
    • Necroborus Weigel, 1806
    • Necrocharis Portevin, 1923
    • Necrocleptes Semenov-Tian-Shanskiy, 1933
    • Necrophagas Leach, 1815
    • Necrophagus Poole, 1996
    • Necrophorindus Semenov-Tian-Shanskiy, 1933
    • Necrophoriscus Semenov-Tian-Shanskiy, 1933
    • Necrophorus Illiger, 1798
    • Necrophorus Thunberg, 1789
    • Necropter Semenov-Tian-Shanskiy, 1933
    • Necroxenus Semenov-Tian-Shanskiy, 1933
    • Neirophorus Berthold, 1827
    • Neonicrophorus Hatch, 1946
    • Nesonecrophorus Semenov-Tian-Shanskiy, 1933
    • Nesonecropter Semenov-Tian-Shanskiy, 1933
    • Nigrophorus Fabricius, 1787
    • Stictonecropter Semenov-Tian-Shanskiy, 1933

The genus name is sometimes spelled Necrophorus in older texts: this was an unjustified emendation by Carl Peter Thunberg (1789) of Fabricius's original name, and is not valid under the ICZN.

The American burying beetle (Nicrophorus americanus) has been on the U.S. endangered species list since 1989. This species was native to 35 U.S. states but now is only known to exist in 9.[4]

Reproduction

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Burying beetles have large club-like antennae equipped with chemoreceptors capable of detecting a dead animal from a long distance.[5] After finding a carcass (most usually that of a small bird or a mouse), beetles fight amongst themselves (males fighting males, females fighting females) until the winning pair (usually the largest) remains. If a lone beetle finds a carcass, it may continue alone and await a partner. Single males attract mates by releasing a pheromone from the tip of their abdomens. Females can raise a brood alone, fertilizing her eggs using sperm stored from previous copulations.[6] The carcass is usually buried by the beetle(s) to hide it from potential competitors, which are numerous.

An example of a species of Nicrophorus that displays this form of bi-parental care and burying activity is Nicrophorus nepalensis. Pairs of Nicrophorus nepalensis prepare carcasses and care for the developing larvae in a joint fashion. After burying a carcass, the beetles mate and lay eggs near/on the carcass. When the eggs hatch into larvae they begin feeding on the flesh of the carcass. The adults remain until the larvae begin to pupate.

Burying beetle life cycle

The prospective parents begin to dig a hole below the carcass. While doing so, and after removing all hair from the carcass, the beetles cover the animal with antibacterial and antifungal oral and anal secretions, slowing the decay of the carcass and preventing the smell of rotting flesh from attracting competition.[2] The carcass is formed into a ball and the fur or feathers stripped away and used to line and reinforce the crypt, also known as a nursery, where the carcass will remain until the flesh has been completely consumed.[7] The burial process can take around 8 hours. Several pairs of beetles may cooperate to bury large carcasses and then raise their broods communally.[8]

The female burying beetle lays eggs in the soil around the crypt.[9] The larvae hatch after a few days and move into a pit in the carcass which the parents have created. Although the larvae are able to feed themselves, both parents also feed the larvae in response to begging: they digest the flesh and regurgitate liquid food for the larvae to feed on, a form of progressive provisioning.[7] This probably speeds up larval development.[10] It is also thought the parent beetles can produce secretions from head glands that have anti-microbial activity, inhibiting the growth of bacteria and fungi on the vertebrate corpse.[11]

The adult beetles continue to protect the larvae, which take several days to mature. Many competitors make this task difficult, e.g. bluebottles and ants or burying beetles of either another or the same species.[12] Throughout the entirety of the larva's development, the parents fight off these competitors all the while maintaining an ideal nursery inside the carcass for their offspring.[6] The final-stage larvae migrate into the soil and pupate, transforming from larvae to fully formed adult beetles.[2]

Parental care (and particularly biparental care) is quite rare among insects that are not eusocial (e.g. ants and honey bees). Burying beetles are exceptional in exhibiting this trait, and thus fall under the category of subsocial insects.[13][7]

Infanticide

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Burying beetles are known to commit infanticide at an early stage, which is also known as culling their young. This is done to ensure that the supply of food provided by the carcass is sufficient to nourish all the larvae sufficiently.[14] If there are too many young, they will all be underfed and will develop less quickly, reducing their chances of surviving to adulthood. If there are too few young, the resulting adult beetles will be large but the parents could have produced more of them.[3] The most successful beetle parents will achieve a good balance between the size of offspring and the number produced. This method of brood size regulation might be the result of the eggs being laid before the female has been able to gauge the size of the carcass and hence how many larvae it can provision.[14]

Conservation

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As of 2020, the American burying beetle (N. americanus) was reclassified from the endangered category to threatened by the Fish and Wildlife Service.[4] Burying beetles are important to the ecosystem and aid in nutrient recycling by burying dead animals. This allows for the nutrient-rich carcass to be recycled by the system.[15]

Species

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N. germanicus
N. humator
N. investigator
N. vespillo
N. vespilloides
N. vestigator

As of 2006 there are over 60 valid, extant species in the genus Nicrophorus although a few undescribed species and synonyms remain to be worked up.

Fossils

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A fossil of N. humator dating around 10,500 years was reported in 1962 by Pearson.[18] An extinct unnamed member of the genus is known from the Late Cretaceous Cenomanian aged Burmese amber of Myanmar, around 99 million years old.[19][20]

References

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  1. ^ GBIF: Nicrophorus Fabricius, 1775 (retrieved 13 January 2020)
  2. ^ a b c Scott, Michelle Pellissier (January 1998). "The Ecology and Behavior of Burying Beetles". Annual Review of Entomology. 43 (1): 595–618. doi:10.1146/annurev.ento.43.1.595. ISSN 0066-4170. PMID 15012399.
  3. ^ a b Trumbo, Stephen T. (1990). "Reproductive Benefits of Infanticide in a Biparental Burying Beetle Nicrophorus orbicollis". Behavioral Ecology and Sociobiology. 27 (4): 269–273. doi:10.1007/BF00164899. ISSN 0340-5443. JSTOR 4600477.
  4. ^ a b "Federal Register :: Endangered and Threatened Wildlife and Plants; Reclassification of the American Burying Beetle From Endangered to Threatened With a Section 4(d) Rule". 15 October 2020.
  5. ^ Canada, Environment and Climate Change (10 October 2012). "American burying beetle (Nicrophorus americanus): COSEWIC assessment and status report 2011". www.canada.ca. Retrieved 2023-04-25.
  6. ^ a b Benowitz, Kyle M.; Moore, Allen J. (December 2016). "Biparental care is predominant and beneficial to parents in the burying beetle Nicrophorus orbicollis (Coleoptera: Silphidae)". Biological Journal of the Linnean Society. 119 (4): 1082–1088. doi:10.1111/bij.12830. PMC 5181846. PMID 28025585.
  7. ^ a b c Smiseth, P. T. (July 2004). "Behavioral dynamics between caring males and females in a beetle with facultative biparental care". Behavioral Ecology. 15 (4): 621–628. doi:10.1093/beheco/arh053. hdl:10.1093/beheco/arh053. ISSN 1465-7279.
  8. ^ Muller, J. K. (March 2003). "Nestmate recognition in burying beetles: the "breeder's badge" as a cue used by females to distinguish their mates from male intruders". Behavioral Ecology. 14 (2): 212–220. doi:10.1093/beheco/14.2.212. ISSN 1465-7279.
  9. ^ Canada, Environment and Climate Change (10 October 2012). "American burying beetle (Nicrophorus americanus): COSEWIC assessment and status report 2011". www.canada.ca. Retrieved 2023-04-25.
  10. ^ EGGERT, ANNE-KATRIN; REINKING, MARTINA; MÜLLER, JOSEF K (January 1998). "Parental care improves offspring survival and growth in burying beetles". Animal Behaviour. 55 (1): 97–107. doi:10.1006/anbe.1997.0588. ISSN 0003-3472. PMID 9480676.
  11. ^ Duarte, Ana; Rebar, Darren; Hallett, Allysa C.; Jarrett, Benjamin J. M.; Kilner, Rebecca M. (24 November 2021). "Evolutionary change in the construction of the nursery environment when parents are prevented from caring for their young directly". Proceedings of the National Academy of Sciences. 118 (48). Bibcode:2021PNAS..11802450D. doi:10.1073/pnas.2102450118. hdl:10871/128609. ISSN 0027-8424. PMC 8640939. PMID 34819363.
  12. ^ Trumbo, Stephen T.; Valletta, Richard C. (April 2007). "The Costs of Confronting Infanticidal Intruders in a Burying Beetle". Ethology. 113 (4): 386–393. Bibcode:2007Ethol.113..386T. doi:10.1111/j.1439-0310.2006.01326.x. ISSN 0179-1613.
  13. ^ Trumbo, S.T. 1994. Interspecific competition, brood parasitism, and the evolution of biparental cooperation in burying beetles. Oikos. 69:241–249.
  14. ^ a b Bartlett, J. (September 1987). "Filial cannibalism in burying beetles". Behavioral Ecology and Sociobiology. 21 (3): 179–183. doi:10.1007/bf00303208. ISSN 0340-5443.
  15. ^ "This Beetle Lays its Eggs in Dead Mice Carcasses and then Covers Them With Mucus – But it's Endangered and Important". The Equation. 5 September 2018. Retrieved 2023-04-26.
  16. ^ "A Bit of Good Luck: A New Species of Burying Beetle from the Solomon Islands Archipelago". Science Daily. 21 June 2013.
  17. ^ Sikes D, Trumbo ST, Peck SB (2016) Cryptic diversity in the New World burying beetle fauna: Nicrophorus hebes Kirby - new status as a resurrected name (Coleoptera: Silphidae: Nicrophorinae). Arthropod Systematics & Phylogeny 74(3): 299-309
  18. ^ Sikes, Derek S.; Madge, Ronald B. & Newton, Alfred F. (29 August 2002). "A catalog of the Nicrophorinae (Coleoptera: Silphidae) of the world". Zootaxa. 65 (1): 1–304. doi:10.11646/zootaxa.65.1.1.
  19. ^ Cai, Chen-Yang; Thayer, Margaret K.; Engel, Michael S.; Newton, Alfred F.; Ortega-Blanco, Jaime; Wang, Bo; Wang, Xiang-Dong; Huang, Di-Ying (30 September 2014). "Early origin of parental care in Mesozoic carrion beetles". Proceedings of the National Academy of Sciences. 111 (39): 14170–14174. Bibcode:2014PNAS..11114170C. doi:10.1073/pnas.1412280111. ISSN 0027-8424. PMC 4191754. PMID 25225362.
  20. ^ Toussaint, Emmanuel F. A.; Condamine, Fabien L. (April 2016). "To what extent do new fossil discoveries change our understanding of clade evolution? A cautionary tale from burying beetles (Coleoptera: Nicrophorus)". Biological Journal of the Linnean Society. 117 (4): 686–704. doi:10.1111/bij.12710.
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