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Field of Mars Environmental Education Centre

Field of Mars Environmental Education Centre

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What are arachnids?

Arachnids include spiders, scorpions, harvestmen, mites and ticks. Their body is made up of two parts called the cephalothorax and abdomen. They have four pairs of legs. 

Arachnids also have a pair of chelicerae for catching and holding prey and a set of pedipalps which act as feelers.

All spiders (Marigung, marrayagong or danganuwa in Darug) belong to a larger groups of animals called arthropods. This means they have a segmented body covered in an exoskeleton and pairs of jointed limbs. 

There are over a million known arthropod species. Arthropods include insects, arachnids, myriapods and crustaceans.

Case study – huntsman spider


Huntsman spiders are large, hairy, flat-bodied spiders. Their legs fan out sideways enabling them to walk forwards and sideways. They are found in a variety of colours and patterns but are mostly brown, black or grey. Some species are very large reaching over 16 centimetres in leg span.


Huntsman spiders occur Australia-wide and are usually found on tree trunks, under bark, beneath stones and even on the walls of houses. Their flat body allows them to squeeze into tight places.


Huntsman spiders eat insects and other invertebrates as well as small lizards and frogs. They hunt their food instead of using a web. Their fangs are large and can be used to hold the prey until it is paralysed by their venom.

Role in the ecosystem

Huntsman spiders control invertebrate populations and pest species such as the household cockroach. They are also food for other animals such as birds, geckos and spider wasps.

Spider anatomy


The cephalothorax is the head and thorax fused together. 

Huntsmen have eight eyes to spot approaching prey and predators.

Located at the front of the spider are the mouth parts called chelicerae. This includes the fangs and pedipalps. They help the spider catch and hold their prey. Males of some species use their pedipalps when mating.

All the spiders' jointed legs are attached to the cephalothorx. The legs have sensitive hairs to pick up sounds, vibrations and air currents.


The abdomen has no appendages except for spinnerets which produce silk.

Huntsmen spiders build silk egg sacks the size of a 20 cent piece to protect their eggs. These can often be found under bark.

Find out more

The Invertebrate Explorer digital book explores the incredible world of Australian invertebrates.

Students can use the book to investigate classification, features, adaptations and habitats of a variety of Australian invertebrates through narrated videos, stunning images, interactive activities and detailed text.

This book was designed by teachers to support the NSW Science and Technology K-6 Syllabus and NSW English K-6 Syllabus.

Content supports living world, Australian animals and class studies on invertebrates.

Download free from Apple Books.

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