What are arachnids?
Arachnids are a group of animals from the animal class Arachnida which includes spiders, scorpions, harvestmen, mites and ticks. Their body is made up of two parts called the cephalothorax and abdomen and they have eight legs.
Arachnids also have a pair of chelicerae which are mouthparts that are used for catching and holding prey and a set of pedipalps which look like another pair of legs (often smaller) that act as feelers for their surroundings and locating prey.
Their habitat is mostly terrestrial environments however some species are located in freshwater and marine envrionments.
The majority of arachnids are predators, feeding on mainly on invertbrates and other small animals, with some species being parasties such as mites and ticks.
All arachnids belong to a larger groups of animals called arthropods. This means they have a segmented body covered in an exoskeleton and paired jointed limbs.
A group of arachnids you may be most familiar with are spiders. The local Darug people of the Sydney basin refer to spiders as marigung, marrayagong or danganuwa.
Case study – Huntsman spider
Appearance
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.
Habitat
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.
Diet
Huntsman spiders eat insects and other invertebrates as well as small lizards and frogs. They hunt their food instead of using a web to catch them. 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.
