Spiders are some of our best allies in the fight against insect pests which cause damage and disease in cities. Often misunderstood, spiders are a vital part of Sydney’s ecosystems and actually help us out more than most people might realise. They are fascinating creatures with a stunning variety of shapes, colours and behaviours, and you can find many of them in your own backyard!
Important allies
Spiders are the primary terrestrial insect predator on Earth. They have been evolving strategies to catch and eat insects for millions of years, which makes them a wonderful ally in pest control.
Without spiders, the population of pest insects around the world would explode.
Spiders also help control insects that can harm humans, such as flies, cockroaches and mosquitoes, and limit the diseases that these pests can spread.
On farms, spiders help control pests that damage crops. They provide a natural pest control service that enables farmers to reduce the amount of pesticides they use to produce our food.
Spiders also provide a source of food for other animals such as birds, lizards and small mammals.
Spiders you could see in your garden
Common Sydney spiders
Spiders are a diverse group. Over 40,000 species have been identified in the world. In Australia we know of over 3,500 species, but there are likely to be more than double that number which haven’t been described yet. You could even find a new species in your backyard – although most spiders will run away at the sight, sound or smell of a human!
Help our native spiders
It’s okay to have insects and spiders in your garden!
Steps you can take to make sure spiders survive outside and continue to provide us with benefits, such as preserving the balance in insect numbers and avoiding pest outbreaks, include:
Do not spray pesticides outside. Pesticides kill insects that would have been a food source for spiders. Without a food source spiders will starve or move away. Broad-spectrum pesticides will also kill off beneficial insects and spiders in your garden. This can result in only hardy pest insects in your garden, and with no natural predators or beneficial insects this gives pest insects the opportunity to thrive.
Encourage insects (aka spider food) by providing plant resources, especially native plants. Providing food as well as places to live, rest and hide are important support for insects in your garden. For example, this could include trees and plants of different sizes. The goal is to create environmental complexity. This means adding layers to your garden such as logs, rocks, leaf litter, flowering plants, small shrubs, trees; whatever will fit in to provide habitat for spiders and their prey.
Do not remove spiders or damage their homes. An easy way to help spiders do their important jobs is to preserve their habitat. The outside world, which includes your garden, is their natural habitat. Unless you have identified spiders as dangerous, leaving them where they are is the best way to let them happily do their job.
What spiders eat
Most spiders are generalist predators, which means they eat a variety of prey. However, different groups of spiders use different hunting methods to catch their prey.
Spiders are loosely grouped into 2 predator groups:
-
active ambush hunters
- sit-and-wait, on a web, down a burrow, on a flower or other foliage.
Where spiders live
Where a spider lives depends on how they catch their prey.
Active hunters do not make webs and live in burrows or funnels in the ground or under logs. For example, huntsman and wolf spiders.
Sit and wait predators make and live in webs to catch their prey. These spiders need lots of vegetation (or buildings!) as attachment points for their webs, such as orb-weaver spiders.
Some spiders have unique and interesting homes. For example:
- Leaf-curling spiders curl up and suspend a leaf in their web so they have somewhere to hide from predators.
- The web of the St Andrew’s cross spider is easily identified by the cross shape they weave into it, which is thought to attract flies and deter birds.
- Jumping spiders don’t use webs to catch prey, but they do build little silk tents between leaves to sleep in and lay their eggs.
What to do if you come across a dangerous spider
Although most spiders are venomous – they use their venom to subdue their prey – very few cause risk to humans.
Spiders known to bite humans but are not medically significant include wolf, mouse, huntsman, white tailed and black house spiders.
White tailed spiders are easily identified by their cylindrical body shape and distinctive white or grey spot on the end of their abdomen. They are active hunters and prey on other spiders. They may be found inside houses, but white tailed spiders are not venomous to humans.
Always err on the side of caution and don’t handle these types of spiders.
Two species to be extra cautious about are redback and funnel web spiders – both cause nasty bites.
A funnel web spider bite can be life threatening.
Visit NSW Poisons Information Centre for more information or ring the Poison Information Hotline on 13 11 26.
Redback spiders are easily identified by their messy webs and round black bodies with a distinctive red stripe.
Funnel web spiders can be difficult to identify, even for experts. They have a similar large chunky body to many other ground-dwelling spiders such as trapdoor, mouse and black house spiders. An important point is that they only ever make their funnel-like webs in the ground.
Black house spiders are sometimes mistaken for funnel webs when people see their cylindrical webs in garages or on window panes. But funnel webs are much larger spiders and only build their webs in the ground, most frequently under logs and lots of leaf litter.
If in doubt, stay away.