Arachnids fact sheet | Field of Mars EEC

What are arachnids?

Arachnids are invertebrates with jointed legs and hard outer skeletons. Spiders, scorpions, ticks, mites, harvestmen and pseudoscorpions are all arachnids. Most adult arachnids have eight legs, no antennae and no wings. Many are predators that hunt insects and other small animals.

Arachnids are found in many places around Field of Mars Reserve, including leaf litter, soil, bark, logs, rock crevices, shrubs, trees, wetlands, gardens and school grounds. Some are easy to see, such as spiders in webs, while others are tiny and hidden in leaf litter or soil.

Golden orb weaving spiders are arachnids that build large silk webs to catch prey.

Scorpions are arachnids with pincers and a curved tail with a sting.

How do you know it is an arachnid?

Adult arachnids are not insects. Insects have six legs, antennae and three main body parts. Adult arachnids usually have eight legs, no antennae and no wings. Spiders have a front body section called the cephalothorax and a back section called the abdomen. Ticks and mites can look more rounded because their body sections are harder to see.

Some arachnids are very small, so students may need to look carefully. A tiny animal found during a leaf litter search or tree shake might be a mite, tick, spiderling or another small invertebrate. Always observe arachnids without touching them.

Spiders have eight legs, no antennae and two main body sections.

Arachnid groups

Arachnids are a diverse group of animals. Some are familiar, such as spiders, while others are tiny, hidden or less often noticed.

Spiders

Spiders are the most familiar arachnids. They have two main body sections and spinnerets that make silk. Some spiders build webs to catch prey. Others hunt on the ground, under bark, on flowers, on tree trunks or among leaves. Around Field of Mars Reserve, spiders can be found in leaf litter, logs, grasses, shrubs, trees, gardens and wetland edges.

Spiders are predators that help control insect populations.

Ticks and mites

Ticks and mites are usually much smaller than spiders. Many mites live in soil, leaf litter, water or on plants. Some help break down organic material. Others are parasites. Ticks are parasitic arachnids that feed on the blood of animals. They should never be handled by students.

Red velvet mites are tiny arachnids found in leaf litter and soil.

Scorpions and pseudoscorpions

Scorpions are arachnids with large pincers and a curved tail with a sting. Many live under logs, rocks, bark or in shallow burrows. They are mostly nocturnal predators. Pseudoscorpions look like tiny scorpions with pincers, but they do not have a tail or sting. They often live in leaf litter, soil or under bark.

Australian woodland scorpions often shelter under logs, rocks or bark during the day.

Harvestmen and other small arachnids

Harvestmen can look like spiders, but their body sections appear more joined together and they do not make silk webs. Many harvestmen feed on small animals and decaying material. Other arachnids include small groups that students may only see during careful leaf litter, bark or soil searches.

Harvestmen can look like spiders, but their body sections appear more joined together.

What is the life cycle of arachnids?

Arachnids grow by moulting. This means they shed their hard outer skeleton as they become larger. Most spiders, ticks and mites hatch from eggs. Young spiders are called spiderlings. Some spiderlings stay close together for a short time before spreading out to find their own shelter and food.

Scorpions have a different life cycle. Female scorpions give birth to live young and carry them on their backs until after their first moult. The number of moults and the time taken to become an adult depends on the arachnid group and species.

Some spiders guard their egg sacs until the young hatch.

What adaptations do arachnids have to help them survive?

Arachnids have many adaptations for sensing, hunting, hiding and protecting themselves. Sensitive hairs and body parts can detect touch, vibration, air movement or chemicals. Many spiders use silk to build webs, make shelters, protect eggs, wrap prey or create safety lines.

Some arachnids use venom to catch prey. Others rely on camouflage, speed, burrows, strong legs or hiding places under bark and leaf litter. These adaptations help arachnids survive as both predators and prey.

Bark huntsman spiders use flattened bodies and camouflage to hide on trees.

Why are arachnids important?

Arachnids are important parts of healthy ecosystems. Predatory spiders, scorpions, mites, pseudoscorpions and harvestmen help keep insect and other invertebrate populations in balance. Tiny mites and other soil arachnids help move nutrients through leaf litter and soil.

Arachnids are also food for birds, lizards, frogs, mammals, centipedes, wasps and other spiders. A habitat with many kinds of arachnids often has shelter, prey, leaf litter and healthy microhabitats.

Arachnids help food webs by feeding on other invertebrates and becoming prey for larger animals.

How can you help arachnids?

You can help arachnids by protecting habitat. Leave leaf litter, bark, sticks, logs and rocks in place where it is safe to do so. These provide shelter, hunting places and egg-laying sites. Plant local native trees, shrubs, grasses and groundcovers to create a layered habitat that supports insects and other prey.

Avoid unnecessary pesticide use, especially in gardens and near bushland edges. Observe arachnids carefully without touching them. Some spiders, ticks and scorpions can bite or sting, and ticks should be removed safely by an adult or health professional.

Native plants and leaf litter provide shelter and food-web habitat for arachnids.

Explore more

Use the fact sheet links on this page to learn more about invertebrates found in bushland, gardens, wetlands and school grounds.

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