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Background Information - 'Minibeasts'

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Introduction

'Minibeasts' is a useful lay term to use when generally describing a broad group of small animals. However, it is more scientifically accurate to classify the animals we are looking at as arthropods.

The diagram below shows the scientific criteria used for classifying various 'minibeasts' into the large group called arthropods and its smaller sub-groups.

Examples of the arthropod sub-groups are:

  • Insects include bees, butterflies, beetles, ants, moths, praying mantids, cicadas, cockroaches, fleas, wasps, and flies.
  • Arachnids include spiders, scorpions, pseudoscorpions, ticks, and mites.
  • Crustaceans include crabs, shrimps, prawns, lobsters, crayfish, and slaters.
  • Myriapods include centipedes and millipedes.

Most arthropods have a hard exterior casing known as an exoskeleton, which they must shed in order to grow. This process is called moulting.

Insects

Insects have six jointed legs and a body that is divided into three parts: head, thorax and abdomen. Insects have a head that has a pair of antennae and have mouthparts that are adapted for particular diets. 75% of all animal species described by scientists are insects.

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Arachnids (spiders, scorpions, mites and ticks)

Arachnids have a body divided into two parts: the cephalothorax (head + thorax) and the abdomen. They have four pairs of walking legs and lack both antennae and wings. They usually have 8 simple eyes.

Spiders are arachnids that have chelicerae (jaws with fangs) that inject poison, and they possess silk glands and spinnerets on the abdomen.

Scorpions, mites and ticks are also part of the Arachnid family. Scorpions have a long tail that ends in a stinger. They also have a pair of pedipalps (front limbs) that end in grasping pincers at the front of their bodies.

Most ticks and mites are parasites on other animals. A parasite is an animal that lives off the blood, body fluid or tissues of another animal. However, some mites feed on plant material rather than on animals.

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Centipedes and millipedes

Most centipedes have 20 - 30 pairs of legs. A very few have as many as 100 legs. Centipedes are carnivores that catch other invertebrates for food. Large centipedes may sometimes even eat vertebrates such as frogs, geckos and mice. Centipedes have fangs which inject venom into their prey. Don't touch a centipede as it can give a painful bite.

Millipedes are herbivores. They feed on vegetable matter and are found in moist places such as under logs. They have hundreds of tiny legs that move together in waves to carry the millipede along. They don't have venom but some species produce an irritating fluid.

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Crustaceans (crabs, shrimps and slaters)

All crustaceans have a body divided into a head, thorax and abdomen, and have more than eight legs. Most of them have a harder section protecting the thorax called a carapace. Many crustaceans live in water (both fresh and saltwater). Slaters are the most obvious crustacean that lives on land. You can find these in your backyard - check under pot plants and logs. Australia has at least 7 species of freshwater crab and many more species of saltwater crab.

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