IMPORTANCE OF ENTOMOLOGY
NUMBERS AND BIODIVERSITY OF INSECTS
Despite their small size, the sheer numbers or biomass of insects means that they have a significant impact on the environment and therefore upon our lives.
Their species richness or diversity surpasses any other group of organisms. It has been said that insects outnumber all the other species of animals and plants combined.
This relative diversity may be appreciated by a speciescape whereby the size of an organism, as drawn, is approximately proportional to the number of described species in the group (or taxon) that it represents.
We do not know how many species of insects there are. There are about 1 million named species. It has taken about 300 years for scientists to describe these. Estimates of actual species richness vary from less than 5 million to as many as 80 million. Figures at the higher end of these estimates are dependent upon the diversity of species now being recovered from the canopies of rainforests.
Obviously there are many years (if not centuries) of work for insect taxonomists to describe, name and classify these species.
COMPOSITION OF INSECTS
Beetles are the largest group (or order) of insects. (The Mantophasmatodea is the smallest group with only a couple of recently discovered species in it.)
Both the number of insects and their diversity has led to the importance of insects in most aquatic and terrestrial food webs. They have roles as prey, predators, parasites and recyclers of dead matter, and many organisms, including most higher plants, could not exist without them.
WHY ARE INSECTS SO SUCCESSFUL?
There are many attributes of insects that have allowed for their success and diversification.
- Small size -there are many more niches for small organisms than for large organisms. For instance, one insect could live solely on and in the seeds of a specific plant.
- Short life cycle - this allows many generations within a given time for selection and evolution to take place.
- Large reproductive ability - large numbers of offspring support a large variation for selection and evolution to act upon.
- Variation in the life style of different stages in an insect's life (e.g. caterpillar versus butterfly) reduces competition for resources within the species.
- Wings-the ability to fly is relatively rare outside insects and has allowed them to colonise freely.
- Sensory sophistication - the sensory capabilities of insects surpasses most other organisms.
- Evolutionary interactions with other organisms - coevolution leads to greater specialisation and speciation.
- Adaptation of appendages - mouthparts, wings and legs have often become highly specialised.
ECONOMIC IMPORTANCE - HOW DO INSECTS AFFECT US?
An insect may be of benefit to us or be regarded as a pest.
Most are beneficial or have an indirect influence.
Fewer than 0.1% are regarded as pests.
ADVANTAGEOUS EFFECTS
Plant pollination - Pollination by animals is more effective than by wind. Most higher plants are pollinated by animals, usually insects such as bees, wasps, flies and beetles.
Production of products - honey, bees wax and royal jelly (an export industry for Australia), silk (produced by the caterpillar,Bombyx mori), shellac (a varnish produced by a plant bug), cochineal (red food colouring produced by a plant bug) and 'Spanish fly' (a beetle and supposed aphrodisiac).
Nutrient recycling - by detritus and dung feeders and particularly in Australia by termites.
Human food - over 500 species of insects are used as food by humans -usually crickets, grasshoppers, beetle and moth larvae and termites. Australian aborigines regularly ate honeypot ants, adult bogong moths and the larvae of wood moths (witchety grubs). (see entomophagy).
Miscellaneous - Indigenous peoples (e.g. from PNG) often used butterflies and brightly coloured beetles as head or body decoration. Insect collecting is a common Western hobby and there is a small industry in arthropod pets.
DETRIMENTAL EFFECTS
- Destruction or spoilage of food (both fresh and stored) and crops (including forests)
- Damage to goods - leather, paper, textiles, (by beetles, cockroaches, silverfish or moths), timber (by termites and different sorts of borers)
- Direct disease of humans or livestock
- Disease vectors
- Venoms, allergies, urtication
- Nuisance value - bush flies, ants
- Phobias - such as arachnophobia
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