Innumerable and endlessly diverse
Together with crustaceans, millipedes and spiders, insects are classified among the arthropods. They are characterised by their six legs, which distinguishes them from e.g. spiders, which have eight legs.
Insects are the most diverse class of animals. Almost a million species have been scientifically described to date, which means they make up over 60% of all known creatures.
There are tiny, not even one-millimetre-long insect species, e.g. the fairy wasps, and species that are more than 30 cm in length, such as some stick insects.
An insect's body is divided into three parts: head, thorax and abdomen, a feature which can be seen particularly clearly in ants. The wings are formed from skin folds. In addition to the antennae and mouthparts, the head carries the compound eye, consisting of numerous individual eyes. The abdomen contains the digestive, respiratory, excretory and reproductive organs. The body is supported by an exoskeleton that cannot grow and therefore has to be moulted a number of times.
An insect develops in various stages from egg to larva to adult. Many species have a further stage between the larval period and the adult: the pupa. During the pupal stage the insect's body is completely reconstructed. This is especially well known in butterflies and moths. Often, the larval period is the longest phase of an insect's life, e.g. in mayflies, whose larvae live up to 2 years in water.
The class of insects is ancient. Around 400 million years ago, insects already populated the world. The species group has developed a wide variety of forms and adaptations and colonized nearly every habitat on earth.