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Why do we study insects?

  • Insects spread disease. Malaria, which is a disease carried by Anopheles mosquitoes, kills over 1.5 million people in Africa every year, most of them children. Simulium flies in West Africa spread a disease to people called onchocerciasis which makes them go blind. Tsetse flies (Glossina spp.) infect people with sleeping sickness which left untreated can result in death. If you swallow a flea in your house you run the risk of being infected with tapeworm. There are many other diseases transmitted between humans and between humans and animals by insects and in order to control the spread of these diseases we need to study the vector insects that spread them.

  • Insects eat our crops. Millions of rand are spent annually in South Africa controlling insects that eat our crops. Insecticides are the one way of controlling pests but they have undesirable side-effects on our health and the environment so the preferred method is biological control where entomologists find beneficial parasitic and predatory insects such as parasitic wasps and ladybird beetles that can be released to control the pests.

  • Insects eat our stored food. The large grain borer, Prostephanus truncatus, has recently spread through subsaharan Africa and is causing value and weight losses to stored maize approaching 60%. There are many other stored product pests that can cause serious food losses and some of these you will have encountered in your kitchen if dry foods are left unprotected in your cupboard for too long.

  • Insects maim and kill our livestock. About 10 million km2 of Africa is affected by animal trypanosomiasis (nagana), spread by Tsetse flies (Glossina spp.), which seriously limits farming efforts. For cattle to thrive in these areas, they need to be given drugs and/or the tsetse need to be controlled. The sheep blowfly Lucilia cuprina causes about a R20 million loss to the South African wool and mutton industries per year. Ticks (which are arachnids not insects) spread many livestock diseases and farmers in South Africa spend millions annually on pesticides to control them.

  • Insects provide us with food. Honeybees (Apis mellifera) provide us with honey. Many people in Africa feed on insects directly: grasshoppers, flying termites and ants, mopane caterpillars are common food items. For a review of the insects eaten by people in Africa, see van Huis (1996).
  • Insects recycle waste. Dung beetles bury dung and prevent it from building up and acting as a breeding site for flies. Flies and beetles breed in dead animals and consume the flesh and skin resulting in nutrient recycling and cleaning up of the landscape. Termites eat dead plant material, so the nutrients in the plants are returned to the soil. There are numerous other insect groups that make their living on decaying organic matter.

  • Insects pollinate flowers. The deciduous and citrus fruit industries depend upon honeybees to pollinate flowers on fruit trees and without this pollination we would have no fruit. Bees, beetles and other insects are also essential in the pollination of most wild flowers.

  • Insects provide food to other animals. Birds such as robins, white-eyes and warblers feed mainly on insects. Antbears and pangolins have become specialists in feeding on ants and termites.

  • Insects control weeds. Leaf, wood and seed-feeding insects prevent particular plant species from taking over the land surface and becoming weeds. A plant often becomes a weed when it is introduced to a foreign country without the insects that feed on it. Entomologists return to the country of origin and find these insects and after checking that the insects do not feed on beneficial plants, they are introduced to control the weed.

See also: Bugs: the good, the bad and the ugly (USDA Systematics Laboratory)

References

  • van Huis, A. 1996. The traditional use of arthropods in sub Saharan Africa. Proceedings of the section Experimental and Applied Entomology of the Netherlands Entomological Society 7: 3-20.

 

 

Why do we study insects?


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