Insects are literally 'everywhere'. Their remarkable adaptability, strength in numbers and high reproductive rates have helped them to become without doubt the most dominant form of life on earth. To back up thus statement the question must be asked that 'If all insects were non-existent tomorrow then what sort of world would we have within twelve months of their demise?'. A key factor in the food chain and the whole ecological balance, insects are precious in the extreme and yet are often overlooked and treated with disdain. But just what are insects?
Insects are characterised by several distinguishing features which sets them apart from any other group of organisms.
The first and most obvious feature is that all insects have 6 legs. These appendages are all attached to the thorax as well as the wings. If it doesn't have 6 legs then it's not an insect.
An insects body is composed of 3 parts - head, thorax and abdomen. Remember INSECT = IN SECTIONS.
An insect has an external skeleton (exoskeleton) rather than an internal one. This is mainly composed of chitin.
Most insects possess 2 pairs of wings.
It is important to remember that there are many small creatures that many of us consider as insects but upon examination are in fact members of other groups, for example:- Woodlice (crustaceans), Centipedes and Millipedes (myriapods) and most famously Spiders (Arachnids).