Insects in the Wet Tropics

Learning about insects means entering a world of numbers! This is the most abundant animal type on earth, boasting almost 90 percent of all living things. Scientific estimates put the total number of species of insects worldwide up around the 30 million mark. In Australia we have already described over 86,000 species divided into 661 families, but there are likely to be thousands more insects waiting to be found and classified. If the abundance of insects in the Wet Tropics compared to the rest of Australia is similar to that of other animal types, then there are probably around 40,000 insect species hiding in the forests here.

There are too many types of insects to cover here but some of the more familiar types are surprisingly diverse in Australia. Did you know that this island continent contains at least:

  • 50 species of stick and leaf insects
  • 162 species of mantis
  • 250 species of cicadas
  • 348 species of termites
  • 428 species of cockroaches
  • 550 species of shieldbugs
  • 2,827 species of crickets and grasshoppers
  • 4,000 species of ants
  • 7,786 species of flies
  • 20,816 species of butterflies and moths
  • 28,200 species of beetles!


Identifying insects

Insects and related animals all have an exoskeleton - like a hardened skin on the outside of the body. This exoskeleton protects the soft inner body, reduces dehydration and provides support and structure - mammals are the opposite, with structural support being found on the inside of the body and provided by a skeleton containing a central backbone. Insects do not have a backbone so they are one of many animal types referred to as invertebrates. Another term you'll hear applied to insects, spiders and related animals with an exoskeleton is arthropod.

There is a lot of confusion about insects because not everything that looks like an insect is an insect. For example, spiders are not insects, nor are mites, ticks and scorpions - they are in the arachnid family the same as the spiders. The little grey woodlouse or slater so common in garden soil is actually a crustacean. Millipedes and centipedes are not insects either.

To be classified as an insect, an animal must have three main body parts, three pairs of legs (which all emerge from the second body part) and one pair of antennae. Not all insects have wings but if wings are present in an invertebrate, it is an insect.


Insects and plants

There appears to be a strong connection between insects and plants. The greater the number of plant species in an area, the greater the number of insect species in the same area. This link is being studied but it is already obvious that there are more species of insects in the tropical rainforest environment than there are anywhere else. In the Wet Tropics two areas stand out as having the greatest concentrations of overall numbers of insect species and numbers of endemic insects (insects which occur nowhere else). The first area is the Carbine Tableland which is located north of the towns of Mossman and Julatten. The second area is the Bellenden Ker Range, about halfway between Cairns and Innisfail.


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