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Burying or sexton beetles (Nicrophorus)Burying or sexton beetles (Nicrophorus) belong to the family Silphidae (carrion beetles); the alternative generic name, Necrophorus, is an emendation by Carl Peter Thunberg (1789) of Fabricius's original name and is not valid. Pearson (1) described a fossil of N. humator dating around 10,500 years in 1962.
Most burying beetles are black with red markings on the elytra (forewings). They have large, club-like antennae.
Chemoreceptors on the antennae can detect a dead bird, mouse or other small animal from a long distance. After finding a carcass, male beetles fight males and females fight females until the winning pair (usually the largest) remains. If a lone beetle finds a carcass, it can continue alone and await a partner. Single males attract mates by releasing a pheromone from the tip of the abdomen. Females can raise a brood alone, fertilizing her eggs using sperm stored from previous matings. The beetles must bury the carcass to get it out of the way of other burying beetles, as well as bluebottles, ants and other potential competitors. The prospective parents begin to dig a hole below the carcass. They cover the animal with antibacterial and antifungal oral and anal secretions to slow the decay of the carcass and stop the smell of rotting flesh from attracting competition. The carcass is formed into a ball and the fur or feathers are stripped away and used to line and reinforce the crypt, where the carcass will stay until the flesh has been completely consumed. The burial process can take around 8 hours. Several pairs of beetles may cooperate to bury large carcasses and then raise their broods communally.
The female lays eggs in the soil around the crypt. The small, white larvae hatch after a few days and move into a pit in the carcass that the parents have created. The larvae can feed themselves, also but beg for food from both parents (2). The parents digest the flesh and regurgitate liquid food for the larvae to feed on. This probably speeds up larval development. It is thought that the parent beetles can produce secretions from head glands that have anti-microbial activity, which inhibit the growth of bacteria and fungi on the corpse (3).
At an early stage, the parents may cull their young, so that there are enough larvae to feed on the available food. If there are too many young, they will all be underfed and will develop less quickly, so they have less chance of surviving to adulthood. If there are too few young, the resulting adults will be large but the parents could have produced more of them. 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 may be the result of the eggs being laid before the female can gauge the size of the carcass and hence how many larvae it can provision. The adults continue to protect the larvae, which take several days to mature, until the final-stage larvae migrate into the soil and pupate, transforming into fully formed adults.
The genus has 68 valid, extant species, but there are a few undescribed species and synonyms.
The American burying beetle (N. americanus) has been on the U.S. endangered species list since 1989.