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If you have ever wondered why we are not overwhelmed by decomposing bodies of the mammals and birds that die in the countryside, the answer lies in the great variety of creatures that specialise
in feeding on them. Some are large - eagles, for example, eat dead sheep - but many are small and rather insignificant. Among the latter are the burying beetles (genus Necrophorus), which have many fascinating aspects
to their lifestyle. Most Necrophorus are large black beetles, about 1in (2,5cm) long, with two striking orange-red bands across their wing cases. As adults they are most common mid to late summer and in autumn, and,
because they are readily attracted by light, they are often found in or around houses and barns.
 If disturbed, burying beetles can put on a dramatic display, thoroughly alarming
would-be predators, and even to humans they can appear frightening. First, their orange and black colour indicates threat; second, they often make a convincing bee-like buzz while pulsating their
abdomen; and finally they can produce a rather repulsive smell. As a result they appear to be dangerous - like an angry bee or wasp - but in fact, apart from the smell, they are quite harmless. Many insects have
evolved similar 'bluffing' features; the familiar hover flies are a good example of totally harmless creatures that are excellent mimics of wasps.
Burying beetles have a superb sense of smell, and survive through their ability to detect the presence of fresh carrion. Both male and female beetles have this ability, and home in on the
corpse as soon as they possibly can; they compete with so many other beetles and flies - as well as other burying beetles - for the precious corpse that there is a great premium on
getting there first. Once they reach the body they crawl under it, sometimes joining a jostling horde of beetles, and begin to dig a shallow grave, so that the corpse gradually sinks into it.
If the ground is too hard they may even drag the body to a softer spot, but eventually it is buried and covered in a thin coating of soil, partly, it is thought, to reduce its attractant smell
but also to protect it from the elements. During this process, and especially as it nears completion, the first or largest arrivals may
oust the others, with the result that only one pair is left in triumphant occupation to mate and lay eggs. The female digs a small tunnel and lays her eggs in a chamber at the end. The
eggs soon hatch and at first the young larvae are fed by the female beetle on predigested bits from the corpse. Later they can make their own way to the corpse and here they live
out their larval lives. The female may leave after feeding the small grubs, flying off to find another meal. Burying beetles often act as hosts to mites - which look like tiny dull orange
'spiders' -that cling to the beetle's hairy bodies. Some mites are parasitic on beetles, but most are hitching a ride to another corpse on which they also feed. A small mite could never
crawl fast and far enough to reach a fresh source of food, so this is an excellent solution. Burying beetles seem rather gruesome, but their vital job makes them allies and, if trapped
at a light, they should be let out to carry on the good work!. |
