Nicrophorus americanus
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| Nicrophorus americanus (Olivier, 1790) |
Nicrophorus americanus, the American burying beetle or giant carrion beetle, is an endangered species of beetle endemic to North America. It is the largest carrion beetle in North America, is carnivorous, feeds on carrion and requires carrion to breed. It is also one of the few species of beetle to exhibit parental care. The decline of the American burying beetle has been attributed to habitat loss, alteration, and degradation, and they now occur over less than 10% of their historic range.
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[edit] Physical description
N. americanus is between 25 and 45 mm long and can be identified by its striking, distinctive coloring. The body is shiny black, and on its wing covers are four scalloped, orange-red markings. Most distinctively, there is an orange-red marking on the beetle's pronotum, a large shield-like area just behind the head. N. americanus has orange facial markings and orange tips on their large antennae. The beetle is nocturnal and is a strong flier, moving as far as a kilometer in one night.
[edit] Reproduction
During the winter months when temperatures are below 15 °C (60 °F) N. americanus adults bury themselves in the soil to overwinter. When temperatures are above 15 °C (60 °F) they emerge from the soil and begin the mating and reproduction process. Burying beetles are unusual in that both the male and female take part in raising the young. Male burying beetles often locate carcasses first and then attract a mate. Beetles often fight over the carcass, with usually the largest male and female individuals winning. The victors bury the carcass, the pair mates, and the female lays her eggs in an adjacent tunnel. Within a few days, the larvae develop and both parents feed and tend their young, an unusual activity among insects, but a characteristic shared with the earwig. Brood size usually ranges from one to 30 young, but 12 to 15 is the average size.
The larvae spend about a week feeding off the carcass then crawl into the soil to pupate, or develop. Mature N. americanus beetles emerge from the soil 45 to 60 days after their parents initially bury the carcass. Adult American burying beetles live for only 12 months.
[edit] Ecology and behavior
Historical records offer little insight into what type of habitat was preferred by the American burying beetle. Current information suggests that this species is a habitat generalist, or one that lives in many types of habitat, with a slight preference for grasslands and open understory oak hickory forests. However, the beetles are carrion specialists in that they need carrion the size of a dove or a chipmunk in order to reproduce. Carrion availability may be the greatest factor determining where the species can survive.
[edit] Conservation status
Historical records show that this beetle once lived in 35 states of the United States, the District of Columbia, and three Canadian provinces: Ontario, Quebec, and Nova Scotia. Now, natural populations are known to occur in only five states: on Block Island in Rhode Island, Oklahoma, Arkansas, South Dakota and Nebraska. They have also been reintroduced to Ohio. N. americanus was listed as an endangered species in 1989; the IUCN lists the species as critically endangered. Biologists have not shown why N. americanus has disappeared from so many areas. Widespread use of pesticides may have caused local populations to disappear. The dramatic disappearance of this insect from many areas, however, took place before widespread use of DDT. Lack of small carcasses to bury would prevent the species from reproducing, and changes in land use has reduced the quantity of small- to medium-sized birds and mammals preferred by N. americanus. Even the extinction of the once ubiquitous passenger pigeon may have had a ripple effect on carrion feeders like this beetle.
The immediate goal of conservation efforts is to reduce the threat of extinction by creating captive and wild populations. Biologists have attempted to establish a beetle population releasing laboratory-raised American burying beetles on Penikese Island in Massachusetts. Biologists return each year to Penikese Island to study the survival and growth of the beetle population.
[edit] References
- World Conservation Monitoring Centre (1996). Nicrophorus americanus. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 10 May 2006. Listed as Critically Endangered (CR A1c v2.3)
- U.S. Fish and Wildlife Service, Division of Endangered Species. 1997. The American Burying Beetle
- U.S. Fish and Wildlife Service, American burying beetle (Nicrophorus americanus)
- U.S. Fish and Wildlife Service. 1991. American Burying Beetle Recovery Plan
