Role of insects
Insects exist in all shapes and sizes, round or long, crawling or flying, and from well-camouflaged to vividly coloured. There are about 5.000 dragonflies, 20.000 grasshoppers, 170.000 butterflies, 82.000 bugs, 120.000 flies, and 110.000 bees and wasps. The beetles are the largest insect group with at least 350.000 different species. The real species number of flies, hymenoptera and butterflies could be even a lot higher.
Some insects live to a large extent under water and swim well or slide over the water surface. Insects are found anywhere in the world, except on open sea, and live in all possible niches in nature. Most insect species live on plants but a large number lives on other animals, often other insects. The combination of their enormous species number and large shape richness makes insects an important link in each ecosystem, apart from the marine ecosystems.
The (according to recent insights polyphyletic) mammal order Insectivora or insect eaters to which the shrewmouse and bat belong would not even exist without insects. Other animal groups like reptiles, amphibians and insect-eating birds are also dependent on these little creatures. Besides animals, there are also a lot of plants which depend from insects (not only bees but even some beetles and flies) for pollination. Even humans benefit from them. Thanks to insects, products like honey, silk and beeswax now exist. Moreover, insects also play a part in the pollination in hives and in nature. Humans even use insects to control other insect species. Known examples are ichneumon wasps who kill caterpillars and some ladybirds species who eat plant louses. Varnish was formerly produced using shellac, a substance tapped from a louse species. The Spanish fly is famous for its capacity as potency-increasing stimulant, even if its not a fly but a beetle. Insects are considered a delicacy in a lot of countries. A lot of caterpillar and grasshopper species are valued for their high protein percentage and nut flavour.
Some insects are however harmful because they can bite or sting painfully (deer fly, wasp), or even carry diseases (malaria mosquito, tsetse fly). Nevertheless, most damage is done by plant-eating insects like louses, caterpillars, thrips and other sucking or gnawing insects able to ruin whole harvests. The larval form or nymphs of insects are often a lot more damaging due to their rapid growth process which causes them to be gluttonous. Moreover, cultivated horticulture is their preferred environment. Long-horned beetles are an innocent beetle family which lives on small quantities of nectar and pollen. They mainly concentrate on reproduction. The larvae are able to cause severe damage to dead or living trees but also to all sorts of wooden objects like works of art and especially girders in old buildings. There are several insect species which can cause sometimes inconceivable damage by swarming. A known example is the desert locust. The break-out of the Chikungunya virus on among others Madagascar and the French Isle Réunion in the beginning of 2006 was blamed to mosquitoes. This virus infected more than 150.000 persons with the painful infection, 77 of them died because of this virus.
The larval form of insects, such as maggots, is also used in forensic research. This is due to the fact that larvae are greatly dependent on the food supply and temperature for the speed of their growth. This technique permits us to make a better estimate of a crime victims date of death if the larvae have an optimal food supply and the temperature can be reduced.
Another rather experimental use of insects is the healing of wounds with aid of sterile maggots (fly maggots). These latter prefer rotting, or dead flesh, and do not eat the healthy flesh. This therapy permits the wound to heal more rapidly because the dead and infected flesh is being removed.