There is an extraordinary diversity of bugs on Earth. The numbers of mammals,
birds, reptiles, amphibians and plants are relatively well known, but
scientists can only guess at the number of species of insects and other
There are about 36,000 species of vertebrate animals in the world, of which
9,040 are birds and 4,000 are mammals. By comparison, estimates of the number
of species of invertebrate animals range from 1.5 million to 10 million, and
even up to 30 million.
Scientists generally agree that the number of species yet to be described and
named is greater than those that have been named so far. Many species are yet
to be discovered, while others are in museum collections waiting to be
Insect species make up the largest group of arthropods. In fact, they are the
largest of all animal groups. Of all the animal species on Earth that
scientists have named and described, 75% are insects.
Entomologists, or scientists that study insects, divide the insect world into
smaller and smaller groups according to similarities. The class Insecta is
divided into 30 groups, called ‘orders’. Insect species sharing the same order
may be similar in body shape, types of mouthparts or wing structures. Australia
is home to insect species from 26 orders.
The order Coleoptera, containing beetles, is the largest group of insects. There
are estimated to be about 500,000 different species of beetles, making up about
a quarter of all animal species.
Another large insect group is the order Hymenoptera. This diverse order contains
wasps, bees and ants, and comprises more than 115,000 species. Though termites
are often called 'white ants', they actually belong to the order Isoptera. The
vast number of insects from these two orders accounts for more than half of the
total weight (or biomass) of insects in the world.
The number of individual insects estimated to be alive in the world at any one
time is 10 quintillion, or 10,000,000,000,000,000,000. It is figured that for
every human being on the planet there are about 200 million insects.