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Archive for July, 2018

Fig_01

A parental pair of burying beetles (Nicrophorus vespilloides) taking care of their larvae; beetles and larvae are sitting on the meat ball prepared by the beetles. © V.A. Timokhanov.

Of the 32 orders of insects 18 contain members that are carrion-feeders. Most of them are beetles and flies. Because carrion is a limited but valuable food resource, and quite unpredictable in distribution, insects, vertebrates and microorganisms compete for it. A clear characteristic of carrion-feeders is the ability to find and secure a suitable carcass quickly and to make efficient use of it.

In the northern hemisphere, the dead bodies of small mammals and birds are used primarily by burying beetles (Nicrophorus species, family Silphidae), which compete effectively with carrion-eating mammals. For instance, at the Biological Station of Michigan University (USA), scientists laid 780 fresh bodies of dead house mice on the ground in a hardwood forest. Within 24 hours 95% of the bodies had been discovered! Of them, 94% had been found by burying beetles and only 6% by scavenging mammals.

Male and female burying beetles form parental pairs concealing and maintaining carrion while also taking care of and raising their offspring (see Figure). A pair of adults buries a carcass of a dead animal, clean it from fur/feathers, destroys eggs/larvae of flesh-eating flies, and prepares a meat ball from it. The ball is protected from rotting by anal secretions from the beetles that kill bacteria. After mating, the female lays 4 to 30 eggs in the soil near the carrion. The young larvae that hatch from these eggs are fed by the parents that ingest flesh from the carrion and regurgitate partially-digested food directly to their mouthparts. The beetles interact with their larvae much as a mother bird interacts with her nestlings: when a parent approaches larvae, they rear up and make ‘begging movements with their legs’ asking for food. As the larvae grow in size, they beg less often and start feeding on their own. After one to two weeks, the larvae pupate in the soil, and a few weeks later new adult beetles emerge. The mother stays with her offspring until they are ready to pupate, while the male leaves a few days earlier.

The story is partly based on the book by G. Waldbauer (2003) ‘What good are bugs?’, Harvard Univ. Press, 366 pp.

 

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