Identification
Physical Characteristics
Size: The female is the more conspicuous and dangerous spider, with a body length of about 10-14mm. The male is much smaller and often overlooked, measuring only 3-4mm.
Coloration: The female has a velvety or shiny black, spherical abdomen with a prominent red to orange longitudinal stripe on the upper side. This stripe may be broken or look more like an hourglass. Immature females are smaller, often brownish, with additional white markings. The male is light brown with white markings and a less distinct red stripe.
Key Features: The combination of a pea-shaped, black abdomen and the distinct dorsal red stripe on the female is the key identifying feature. Her messy, three-dimensional web is also characteristic.
Biology & Lifecycle
Development & Reproduction
Reproduction Rate: A single female can lay up to 5,000 eggs in her lifetime. This high reproductive potential allows for rapid population growth in favorable conditions.
Lifecycle Details
Egg Stage
After mating, the female can store sperm and produce several egg sacs over a period of months. She constructs between 4 and 10 round, cream-colored, papery egg sacs, each containing approximately 250 eggs. These sacs are suspended within her web.
Larval Stage
Upon hatching, the spiderlings (not larvae) emerge from the egg sac. Cannibalism is common, and only a fraction of the initial number will survive to leave the maternal web. The spiderlings are tiny and disperse by ballooning, releasing silk threads to be carried by the wind. This is a primary mechanism for their spread.
Pupal Stage
Spiders do not have a pupal stage. They grow by moulting their exoskeleton. Males mature faster, going through fewer moults than females.
Adult Stage
Males reach maturity in about 3 months, while females take longer, around 4-6 months, depending on conditions. Adult males have a short lifespan and spend their time searching for females. Adult females can live for 2-3 years, continuously producing egg sacs after a successful mating.
Reproduction Rate
A single female can lay up to 5,000 eggs in her lifetime. This high reproductive potential allows for rapid population growth in favorable conditions.
Generations Per Year
In warmer climates, breeding can occur year-round, leading to multiple, overlapping generations per year. In more temperate regions, there may be one or two distinct generations.
Development Time
From egg to adult takes approximately 3 to 6 months. This timeline is highly dependent on temperature and food supply.
Seasonal Cycle
Populations peak in the hot, dry months of late summer and autumn. Mating and egg-laying are most common during this time. While active year-round in much of Australia, their numbers are highest when insect prey is abundant.
Environmental Factors
Key factors for success are a dry, sheltered web location, protection from predators and rain, and a steady supply of ground-dwelling insects and other arthropods.
Habitat & Distribution
Preferred Habitats
- Dry, dark, and sheltered man-made structures are highly preferred.
- Underneath house eaves, window ledges, and in wall cavities.
- Inside sheds, garages, and outdoor toilets.
- Amongst stored junk, firewood piles, and rubble.
- Outdoor furniture, pot plants, mailboxes, and children's play equipment.
Distribution Patterns
Australian Distribution
Found throughout Australia, including Tasmania. It is more common in temperate and arid regions than in the wet tropics.
Climate Zones
- Temperate
- Subtropical
- Arid
- Mediterranean
Urban vs Rural Distribution
Extremely common in urban and suburban environments due to the abundance of ideal habitats (sheds, houses, etc.). Also found in rural and natural bushland settings.
Native Range
Native to Australia.
Introduced Range
Through human commerce, it has been accidentally introduced to and established in New Zealand, Japan, the United Arab Emirates, and parts of Southeast Asia.
Introduction History
While native to Australia, its spread to other countries like Japan is a relatively recent phenomenon, documented in the late 20th century.
Current Spread
Maintains a continent-wide distribution in Australia and continues to be an invasive species of concern in other countries.
Limiting Factors
Extremely wet conditions and very cold climates can limit population densities, although it can survive winters in sheltered locations.
Behavior & Diet
Activity Pattern
Primarily nocturnal. The female spends the day concealed in a funnel-like retreat within her web and becomes more active at night, often repairing the web or waiting for prey near the ground-level trap lines.
Dietary Preferences
Feeding Habits
Carnivorous generalist predator.
Health Risks
Always consult healthcare professionals for medical concerns related to pest exposure.
Disease Transmission
- Does not transmit infectious diseases.
Allergens and Respiratory Issues
The primary health risk is from the venom, not allergens.
Contamination Risk
Low. While they may live near homes, their webs are typically away from food preparation areas.
Vulnerable Populations
- Children and the elderly are more susceptible to severe effects from the venom.
- Individuals with pre-existing heart conditions (e.g., hypertension) are at greater risk.
- Anyone performing activities in high-risk areas (gardening, cleaning sheds) without protective clothing.
- Pets, especially cats and dogs, can also be severely affected by a bite.
Symptoms of Exposure
- Immediate, intense, and radiating pain from the bite site.
- Sweating, which is often profuse and localized to the bitten limb.
- Nausea, vomiting, and abdominal pain.
- Headache, fever, and general feeling of illness.
- Muscle spasms, weakness, and hypertension. Symptoms can last for hours or even days. Seek immediate medical attention for any suspected Redback bite.
Transmission Methods
- Health risk is exclusively from the venom injected during a defensive bite from a female spider.
Risk Severity
High. A bite from a female is medically significant and can be life-threatening without treatment, though fatalities are now rare due to antivenom.
Economic Impact
Treatment Costs
Professional Treatment
$250-$500 for a targeted Redback treatment program, which includes internal and external spraying and removal of webbing.
Prevention Costs
$150-$300 annually for a general pest control barrier treatment.
Diy Treatment
$20-$50 for household spider-specific aerosol sprays and surface sprays.
Property Damage
Structural Damage
None.
Garden Damage
None. They can be beneficial by eating insect pests.
Food Contamination
Negligible risk.
Equipment Damage
Can build webs inside machinery, but rarely cause functional damage. The primary issue is the risk to operators.
Business Impact
Restaurant Issues
Webs in outdoor seating areas pose a health and safety risk to patrons and staff, requiring diligent control measures.
Retail Impact
Presence in stored goods or on premises can pose a risk.
Reputation Damage
A known Redback problem can severely damage the reputation of any business, particularly those in hospitality, childcare, or tourism.
Operational Disruption
Workplaces like construction sites, farms, and warehouses must have spider management plans to protect employees, potentially disrupting work for inspections and treatments.
Agricultural Impact
Crop Damage
None. Can be beneficial predators.
Yield Loss
No direct loss, but pose a significant occupational health and safety risk to farmworkers, especially during harvest of certain crops like table grapes.
Beneficial Aspects
They eat a wide range of insects and other arthropods.
Economic Loss
Primarily through healthcare costs associated with bites and the cost of implementing pest management programs in commercial and agricultural settings.
Indirect Costs
Healthcare Costs
Significant. A bite requiring hospitalization and antivenom administration can cost thousands of dollars. Lost productivity from time off work is also a factor.
Cleanup Costs
Costs associated with professional pest control services.
Replacement Costs
None.
Preventive Maintenance
The cost of annual barrier treatments and personal protective equipment (gloves, etc.) for workers.
Detection & Signs
Visual Signs
- Sighting of a female Redback spider.
- Presence of their characteristic messy, tangled webs in sheds, under eaves, in mailboxes, or on outdoor furniture.
- Finding the distinctive, spherical, cream-colored egg sacs within a web.
- Webs are often low to the ground and have debris like leaves and dirt incorporated into them.
Physical Evidence
- The web itself, which feels sticky and strong.
- The egg sacs are a definitive sign.
- Remains of prey (insect husks, small lizard skeletons) within or below the web.
Behavioral Signs
- As they are nocturnal, you are more likely to see the spider out in the open on its web at night.
- A lack of other spiders in a particularly good location might indicate a Redback has claimed the territory.
Seasonal Indicators
- Populations and sightings increase dramatically in late summer and autumn.
- Spiderlings may be seen dispersing from a web in spring or summer.
- Increased web-building activity during warmer months.
Early Warning Signals
- A few small, messy webs appearing in sheltered spots.
- Seeing one Redback often means there are more nearby, or that conditions are ideal for them to establish.
Prevention
Sanitation Measures
- Reduce clutter around the house and in sheds. Piles of wood, bricks, or stored items create perfect habitats.
- Regularly clean outdoor furniture, paying attention to undersides and joints.
- Keep garden beds and vegetation trimmed back from the house perimeter.
- Seal cracks and crevices in foundations and walls to block entry points.
Exclusion Methods
- Install weather strips on doors and insect screens on windows and vents.
- Check items being brought indoors (especially from the shed or garden) for spiders or egg sacs.
- Wear gloves, long sleeves, and enclosed shoes when gardening or cleaning up outdoors.
- Routinely inspect and clear out mailboxes, utility boxes, and children's outdoor toys.
Landscaping Tips
- Avoid using dense ground-cover plants right next to the house.
- Keep a clear, vegetation-free zone around the foundation of the house.
- Choose landscaping materials that are less inviting, for example, using gravel instead of wood chips near the house.
- Position firewood racks away from the house and elevate them off the ground.
Monitoring Strategies
- Perform regular inspections (monthly in cooler months, fortnightly in warmer months) of high-risk areas with a torch.
- Pay close attention to sheds, garages, sub-floors, retaining walls, and outdoor furniture.
- A professional pest inspection annually can identify problems before they become severe.
Environmental Modification
- Improve ventilation in sub-floor areas to reduce dampness, which can attract the insects Redbacks feed on.
- Seal entry points into the roof void and sub-floor areas.
- Reduce outdoor lighting to minimise the attraction of insects, which are a food source for spiders.
Control Methods
Professional Treatment Methods
Chemical Control
A licensed pest technician will apply a residual liquid insecticide to all harbourage areas, such as eaves, window frames, sheds, fences, and sub-floors. They may also use an insecticidal dust in wall cavities and roof voids.
Biological Control
The Black House Spider (Badumna insignis) is a known predator of Redbacks, but this is not a practical control method.
Physical Control
Professionals will remove visible spiders and egg sacs as part of the treatment. Crushing the spider and its egg sacs is effective for immediate, localised removal.
Integrated Approach
The most effective professional approach is IPM: inspection to identify hotspots, physical removal of spiders and sacs, targeted chemical application to harbourage areas, and providing advice on prevention and habitat modification.
DIY Treatment Options
Natural Remedies
Generally not effective or recommended for a medically significant pest. The risk is too high.
Home Made Traps
Sticky traps can catch males or juveniles but are ineffective against established females in their webs.
Deterrent Methods
A registered surface spray from a hardware store can be applied to create a barrier around window frames, doorways and along the foundations of the house.
Mechanical Control
If you are confident, wearing protective gloves and shoes, you can kill a single spider with a spray from a registered aerosol insecticide, or by crushing it with an object like a shoe. It is crucial to also find and destroy the egg sacs.
Treatment Effectiveness
Success Rate
Professional treatment is highly effective, often with a 90-100% reduction in activity for several months. DIY methods can be effective for single spiders but often fail to control a larger infestation.
Timeframe
Professional sprays provide immediate knockdown and a residual barrier that can last for 3-12 months depending on the product and environmental conditions.
Follow Up Required
An annual Redback treatment is recommended for most Australian homes to maintain control.
Seasonal Considerations
The best time for a preventative treatment is in spring, before the peak summer season. Treatments are most commonly requested in summer and autumn when spiders are abundant.
Application Techniques
- Use a registered aerosol spider spray and directly spray the spider and its web.
- Apply a residual surface spray to known hiding spots and entry points.
- Always wear gloves when cleaning areas where Redbacks might be present.
- Destroy egg sacs by crushing or spraying them to prevent hundreds of spiderlings from hatching.
Professional Services
Professional Treatment Services
Chemical Control
A licensed pest technician will apply a residual liquid insecticide to all harbourage areas, such as eaves, window frames, sheds, fences, and sub-floors. They may also use an insecticidal dust in wall cavities and roof voids.
Biological Control
The Black House Spider (Badumna insignis) is a known predator of Redbacks, but this is not a practical control method.
Physical Control
Professionals will remove visible spiders and egg sacs as part of the treatment. Crushing the spider and its egg sacs is effective for immediate, localised removal.
Integrated Approach
The most effective professional approach is IPM: inspection to identify hotspots, physical removal of spiders and sacs, targeted chemical application to harbourage areas, and providing advice on prevention and habitat modification.
Professional Treatment Costs
$250-$500 for a targeted Redback treatment program, which includes internal and external spraying and removal of webbing.
Treatment Success Rates
Professional treatment is highly effective, often with a 90-100% reduction in activity for several months. DIY methods can be effective for single spiders but often fail to control a larger infestation.
Treatment Timeframe
Professional sprays provide immediate knockdown and a residual barrier that can last for 3-12 months depending on the product and environmental conditions.
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Browse All ProvidersSeasonal Patterns
Spring Activity
Spiderlings from overwintered egg sacs emerge and disperse. Young spiders grow, and populations begin to build.
Summer Activity
Peak activity period. Spiders are mature, breeding is frequent, and webs are abundant. This is the highest risk period for bites.
Autumn Activity
Activity remains high. Females are large and continue to produce egg sacs before the weather cools.
Winter Activity
In colder regions, activity drops significantly, and many spiders die off. In warmer regions, they remain active but may be less conspicuous. The species survives as egg sacs or sheltered individuals.
Breeding Season
Primarily summer and autumn.
Peak Activity Period
Late summer and autumn (February-May) is when populations are at their highest and spiders are most visible.
Environmental Factors
Temperature Effects
Warm weather accelerates their metabolism, growth, and reproduction. Hot, dry conditions are ideal.
Humidity Effects
They prefer dry conditions and will avoid persistently wet areas.
Photoperiod Effects
Longer day length in summer corresponds to the peak breeding season.
Weather Patterns
Heavy rain can destroy webs and flood habitats, but they are quick to rebuild in sheltered locations.
Legal Considerations
Pest Status
Considered a significant public health pest throughout Australia.
Control Regulations
Standard regulations for pesticide use apply. In a workplace setting, there is a legal duty of care (Work Health and Safety Act) to manage the risk posed by venomous spiders.
Professional Requirements
Pest control technicians must hold a valid state-issued license to apply pesticides for the control of spiders commercially.
Environmental Considerations
While targeting Redbacks, care must be taken to minimise spray drift and impact on non-target organisms, especially bees. Targeted application to crevices and harbourage areas is key.
Compliance Requirements
- Workplaces must have a risk management plan for venomous pests.
- Pesticide application must adhere to the product label's instructions, which is a legal requirement.
- Technicians must provide documentation of the treatment performed.
- No special permits are needed for Redback control.
Frequently Asked Questions
What makes the Redback Spider different from other venomous spiders?
The Redback Spider, Latrodectus hasselti, is distinct from other venomous Australian spiders like Funnel-webs in several key ways. Firstly, its habitat and behaviour make it a far more common threat in suburban settings. While Funnel-webs live in burrows in the ground, Redbacks thrive in man-made structures—sheds, outdoor furniture, mailboxes—bringing them into frequent, close contact with humans. Secondly, the venom itself is different. Redback venom is a neurotoxin that causes a specific set of symptoms known as latrodectism, characterized by intense, radiating pain, profuse sweating, and muscle spasms. Funnel-web venom, by contrast, is a different type of neurotoxin that can cause more rapid and life-threatening systemic failure. Thirdly, the bite itself is often less dramatic. A Redback bite may feel like a sharp pinprick initially, with severe pain developing later, whereas a Funnel-web bite is immediately and excruciatingly painful from large, powerful fangs. Finally, an effective antivenom for Redback bites has been available since 1956, making fatalities exceptionally rare today, though the experience remains deeply unpleasant.
How dangerous is a Redback Spider to humans and pets?
A bite from a female Redback Spider is considered medically significant and potentially very dangerous. For humans, the injected neurotoxic venom can cause latrodectism. This condition involves severe and escalating pain that can last for hours or days, localized and sometimes widespread sweating, nausea, vomiting, muscle weakness, and hypertension. While an effective antivenom exists and fatalities are now almost unheard of, the bite is still a serious medical emergency, particularly for children and the elderly who can experience more severe reactions. Pets are also at high risk. Cats are notoriously susceptible to Redback venom and a bite can often be fatal. Dogs can also suffer severe symptoms and require immediate veterinary care. The danger is compounded by the spider's tendency to hide in places where accidental contact is likely, such as in shoes left outside or under the lip of a pot plant. It's important to note that only the female is dangerous; the male is too small to deliver a clinically significant bite.
What is the most effective way to get rid of Redback Spiders?
The most effective way to get rid of a Redback Spider infestation is to hire a licensed pest control professional. Given the medical risk, a DIY approach can be dangerous and is often incomplete. A professional will conduct a thorough inspection to identify all harbourage areas ('hotspots'). Their treatment typically involves a multi-faceted approach. They will physically remove and destroy any visible spiders and their egg sacs. Then, they apply a commercial-grade residual insecticide spray to common Redback habitats like eaves, fences, shed interiors, retaining walls, and outdoor furniture. They may also use an insecticidal dust for voids and cavities. This combination not only kills existing spiders but also creates a protective barrier that can prevent new spiders from establishing for many months. For immediate, single-spider situations, a direct spray with a household insecticide can work, but this fails to address the likely presence of others and their egg sacs, which can contain hundreds of future spiders.
How can I prevent Redback Spiders from returning?
Preventing Redbacks is about making your property less inviting to them. This involves a combination of sanitation, exclusion, and regular inspection. Start by reducing clutter. Tidy up sheds, garages, and areas around the house, as piles of timber, boxes, or junk are ideal Redback homes. Regularly clean outdoor furniture, BBQs, and children's play equipment. An essential step is to seal potential entry points into your home; use weather strips on doors and seal cracks in the foundation. Be vigilant. Always wear gloves when gardening or working outdoors, and shake out shoes or clothing that have been left outside. A key professional strategy is an annual pest control treatment. A licensed technician can apply a preventative barrier spray in spring, which is the most effective long-term solution to stop Redbacks from establishing themselves on your property before their population peaks in summer.
When are Redback Spiders most active during the year?
Redback Spiders are most active and abundant during the hottest months of the year, specifically late summer and autumn (from around January to May in most of Australia). During this period, the spiders have reached maturity, food sources (insects) are plentiful, and the warm weather is perfect for breeding. Females will be at their largest, producing multiple egg sacs, leading to a population boom. This is consequently the time of highest risk for humans, as the increased number of spiders means more potential for accidental encounters. While they can be found year-round in many parts of Australia, their activity significantly decreases in winter, especially in cooler southern states. They will either find a sheltered spot to wait out the cold or die, leaving their more resilient egg sacs to overwinter and hatch the following spring. Preventative treatments are therefore best timed for spring to head off this peak summer activity.
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