Insects in the Wet Tropics - General Information

Learning about insects means entering a world of numbers! This is the most abundant animal type on earth, boasting almost 90% 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 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 and
• 28,200 species of beetles!

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 same family as the spiders (the arachnid family). The little grey woodlouse or slater so common in garden soil is actually a crustacean. Millipedes and centipedes are not insects either as they have the wrong amount of legs.

To be classified as an insect, the it 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, it is an insect.

Insects and related animals all have what's called an exoskeleton which is like a hardened skin on the outside of the body. This exoskeleton protects the soft 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 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 of Queensland, two areas stand out as having the greatest concentrations of both overall numbers of insect species present and numbers of endemic insects present (insects which occur nowhere else). The first is the Carbine Tablelands which is located north of the towns of Mossman and Julatten. The second is a single mountain, Mt. Bellenden Ker, which is about halfway between Cairns and the town of Innisfail to the south.