Identification
Physical Characteristics
Size: A relatively large silverfish, with an adult body length of 10-15 mm. Its three rear appendages are very long and can add another 10-15mm to its total length.
Coloration: The defining feature is its colour. The body is covered in scales that give it a uniform, dull grey to greyish-brown appearance. Unlike the Common Silverfish, it lacks a metallic sheen, and unlike the Four-lined Silverfish, it has no distinct lines or stripes, though it may appear faintly mottled upon close inspection.
Key Features: Its uniform dull grey colour is the primary distinguishing feature. It is larger than the Common Silverfish and lacks the shiny lustre, and similar in size to the Four-lined Silverfish but lacks the dark stripes. Its robust and bristly appearance also sets it apart.
Biology & Lifecycle
Development & Reproduction
Reproduction Rate: The rate of reproduction is slow. A female lays a relatively small number of eggs in her lifetime compared to pests like cockroaches or flies.
Lifecycle Details
Egg Stage
Females seek out protected cracks and crevices to lay their eggs in small batches. The eggs are tiny, whitish, and oval. Hatching time is dependent on temperature, typically taking from several weeks to a couple of months.
Larval Stage
Not applicable. Silverfish have nymphs.
Pupal Stage
Not applicable due to their simple metamorphosis.
Adult Stage
Nymphs undergo multiple moults over a long period, potentially 1-2 years, before reaching adulthood. A key feature of silverfish is that they continue to moult even after reaching sexual maturity. Adults are very long-lived, capable of surviving for several years in a suitable indoor environment. This longevity allows a small, unnoticed population to persist and grow over a long time.
Reproduction Rate
The rate of reproduction is slow. A female lays a relatively small number of eggs in her lifetime compared to pests like cockroaches or flies.
Generations Per Year
Due to the extremely long development time, there is typically less than one generation per year.
Development Time
The lifecycle from egg to adult is very slow and highly dependent on temperature and humidity, but it typically takes more than a year and can sometimes extend to three years.
Seasonal Cycle
As an indoor pest, its lifecycle is not strongly tied to the seasons. It will remain active and continue to develop year-round in a climate-controlled home. However, population growth will be faster during warmer periods.
Environmental Factors
Temperature is a key driver of development speed. It is also very adaptable to a range of humidity levels, allowing it to out-compete the Common Silverfish in the drier parts of a house.
Habitat & Distribution
Preferred Habitats
- A very wide range of indoor environments.
- Roof voids and attics, especially where there are stored cardboard boxes.
- Wall cavities.
- Sub-floor areas.
- Bookcases, storage closets, and wardrobes.
- They are less dependent on high humidity than Lepisma saccharinum, making the whole house a potential habitat.
Distribution Patterns
Australian Distribution
Now widespread throughout Australia, found in urban environments in all states.
Climate Zones
- Tropical
- Subtropical
- Temperate
- Mediterranean
Urban vs Rural Distribution
Almost exclusively an indoor pest of urban and suburban areas.
Native Range
Its exact native origin is uncertain, but it is considered an introduced, cosmopolitan species.
Introduced Range
Now found worldwide, having spread with human trade and travel.
Introduction History
Considered a more recent arrival or a more recently identified pest in Australia compared to the Common Silverfish, but its prevalence is increasing rapidly.
Current Spread
It is becoming the dominant silverfish species found in domestic homes in many parts of Australia.
Limiting Factors
Its spread is dependent on human transport.
Behavior & Diet
Activity Pattern
Strictly nocturnal. They hide during the day in dark, secluded cracks and crevices and emerge at night to search for food.
Dietary Preferences
Feeding Habits
Generalist feeders on materials high in carbohydrates and protein.
Health Risks
Always consult healthcare professionals for medical concerns related to pest exposure.
Disease Transmission
- Not known to be a vector for any human diseases.
Allergens and Respiratory Issues
Like other silverfish, the dust created from their shed skins and feces could potentially act as a minor respiratory allergen for very sensitive people in heavily infested homes.
Contamination Risk
Can contaminate pantry foods with their bodies and feces, but the risk is low.
Vulnerable Populations
- Individuals with severe respiratory allergies.
- The most vulnerable 'population' is valuable paper documents, books, and textiles in museums and archives.
Symptoms of Exposure
- They do not cause any direct symptoms. Allergic reactions are possible but uncommon.
Transmission Methods
- Not applicable.
Risk Severity
Low. They are a pest due to the damage they cause, not any health risks.
Economic Impact
Treatment Costs
Professional Treatment
$200 - $450 for a standard internal pest treatment.
Prevention Costs
Costs related to good storage and humidity control.
Diy Treatment
$20 - $50 for insecticidal dusts and traps.
Property Damage
Structural Damage
The damage is to the contents of a property, not the structure itself. They can destroy items of high sentimental or financial value.
Garden Damage
None.
Food Contamination
Minor contamination of stored dry foods.
Equipment Damage
None.
Business Impact
Restaurant Issues
Can infest dry storage areas.
Retail Impact
Can damage paper, textile, or book stock.
Reputation Damage
Their presence can harm the reputation of businesses that handle paper records or textiles, like libraries, archives, and museums.
Operational Disruption
May require temporary closure of areas for treatment.
Agricultural Impact
Crop Damage
None.
Yield Loss
None.
Beneficial Aspects
None.
Economic Loss
The economic loss is associated with damage to stored goods like books, documents, photographs, and natural fibre clothing, as well as the costs of control.
Indirect Costs
Healthcare Costs
None.
Cleanup Costs
Cost of cleaning and discarding damaged items.
Replacement Costs
Potential for high replacement costs of valuable or sentimental items.
Preventive Maintenance
Ongoing pest management costs for sensitive commercial operations like museums.
Detection & Signs
Common Signs of Gray Silverfish Activity
- Damage to paper items: Irregular holes and notches in books, documents, and wallpaper
- Yellowish stains: On fabrics and paper where silverfish have fed
- Cast skins: Shed exoskeletons found in infested areas
- Small dark droppings: Tiny, pepper-like feces in storage areas
- Live sightings: Actual silverfish seen at night in bathrooms, closets, or storage areas
Best Detection Times
Silverfish are nocturnal, so signs of activity are most evident during evening and night hours. Check for damage to stored items, shed skins in quiet areas, and direct sightings when turning on lights in dark spaces like bathrooms or storage areas.
Prevention
Sanitation Measures
- Reduce clutter wherever possible. Silverfish love piles of boxes, paper, and stored clothing.
- Store important documents, photographs, and books in sealed plastic containers.
- Regularly vacuum your home, including closets and behind furniture, to remove food sources like crumbs and dead insects.
Exclusion Methods
- Seal cracks and crevices along skirting boards, in walls, and around window and door frames to reduce their hiding spots.
- Carefully inspect any cardboard boxes or second-hand furniture before bringing them inside.
Landscaping Tips
- Keep the perimeter of your house clear of leaf litter and ensure the foundation is dry.
Monitoring Strategies
- Use sticky traps placed in suspected areas of activity, such as in closets, behind toilets, and in the attic, to monitor for their presence.
- Perform regular visual inspections of dark, quiet storage areas.
Environmental Modification
- Control humidity throughout the house. Use exhaust fans in bathrooms and kitchens.
- Use dehumidifiers in any areas that are prone to dampness, like basements or sub-floor areas.
- Fixing any sources of moisture leaks is a critical step in making the environment less hospitable for them.
Control Methods
Professional Treatment Methods
Chemical Control
A professional treatment typically involves applying a residual insecticide spray to internal cracks and crevices, skirting boards, and other harbourage areas. They will also likely apply an insecticidal dust into voids like the roof and sub-floor area.
Biological Control
Not available.
Physical Control
Addressing moisture issues and reducing clutter are key physical controls recommended by professionals.
Integrated Approach
A comprehensive IPM plan is most effective. This includes a thorough inspection, targeted chemical application to kill the existing population, and providing detailed recommendations on environmental and structural modifications (like humidity control and sealing cracks) to prevent reinfestation.
DIY Treatment Options
Natural Remedies
Diatomaceous earth can be applied as a fine powder into cracks and voids. It is non-toxic but slow-acting.
Home Made Traps
Simple sticky traps or glass jar traps can be used to catch and monitor them, but they will not control a large infestation.
Deterrent Methods
Scents like cedar or lavender are often used as repellents in closets but offer limited protection.
Mechanical Control
A thorough vacuuming of all potential hiding places can help to reduce numbers of both adults and eggs.
Treatment Effectiveness
Success Rate
Professional treatments are very effective for reducing the current population. The long-term prevention of their return is highly dependent on the homeowner's efforts to control humidity and clutter.
Timeframe
A noticeable reduction in activity should be seen within one to two weeks of a professional treatment.
Follow Up Required
For heavy or widespread infestations, a follow-up treatment may be necessary after a few months.
Seasonal Considerations
Treatment is effective at any time of year as they are an indoor pest.
Application Techniques
- Targeted 'crack and crevice' spraying.
- Void dusting with a powder applicator.
- A general perimeter spray inside the home along all wall/floor junctions.
Professional Services
Professional Treatment Services
Chemical Control
A professional treatment typically involves applying a residual insecticide spray to internal cracks and crevices, skirting boards, and other harbourage areas. They will also likely apply an insecticidal dust into voids like the roof and sub-floor area.
Biological Control
Not available.
Physical Control
Addressing moisture issues and reducing clutter are key physical controls recommended by professionals.
Integrated Approach
A comprehensive IPM plan is most effective. This includes a thorough inspection, targeted chemical application to kill the existing population, and providing detailed recommendations on environmental and structural modifications (like humidity control and sealing cracks) to prevent reinfestation.
Professional Treatment Costs
$200 - $450 for a standard internal pest treatment.
Treatment Success Rates
Professional treatments are very effective for reducing the current population. The long-term prevention of their return is highly dependent on the homeowner's efforts to control humidity and clutter.
Treatment Timeframe
A noticeable reduction in activity should be seen within one to two weeks of a professional treatment.
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Browse All ProvidersSeasonal Patterns
Spring Activity
Activity and reproduction begin to increase as the ambient temperature and humidity rise.
Summer Activity
Peak season for population growth and activity.
Autumn Activity
High levels of activity continue while conditions remain warm.
Winter Activity
Activity slows in colder, unheated parts of a house, but continues year-round in heated areas.
Breeding Season
Year-round indoors, but faster in warmer weather.
Peak Activity Period
Late summer and autumn.
Environmental Factors
Temperature Effects
Warmth speeds up their very slow lifecycle.
Humidity Effects
Adaptable to a range of humidity but still prefer moist air. Dehumidification is a key control tactic.
Photoperiod Effects
Not relevant.
Weather Patterns
External weather has less effect as they are an indoor pest, but periods of high external humidity can increase indoor humidity, favouring them.
Legal Considerations
Pest Status
A common domestic nuisance pest.
Control Regulations
Use of insecticides is regulated by the APVMA.
Professional Requirements
A license is required for the commercial application of pesticides.
Environmental Considerations
Minimal, as treatment is confined indoors.
Compliance Requirements
- All pesticide applications must follow the product label instructions.
Frequently Asked Questions
I have silverfish, but they aren't shiny and silver. What are they?
If you are seeing silverfish-shaped insects that are a plain, dull grey colour and lack the classic metallic shine, you are most likely dealing with the Gray Silverfish, *Ctenolepisma urbana*. This invasive species has become extremely common in Australian homes. Unlike the Common Silverfish (*Lepisma saccharinum*), which has a distinctive silvery lustre, the Gray Silverfish has a uniform, non-reflective grey or brownish-grey appearance. It is similar in size to the Four-lined Silverfish but lacks the dark stripes on its back. Its success comes from its adaptability to the warmer, drier conditions inside many modern homes.
Are Gray Silverfish more damaging than other types?
The damage they cause is very similar to other silverfish species, but their habits can sometimes make them seem more destructive. Like their relatives, they feed on starchy materials like paper, glue, book bindings, and some fabrics. However, because the Gray Silverfish is more tolerant of drier conditions than the Common Silverfish, it is not restricted to just the damp areas of a house like the bathroom or laundry. It can establish infestations in living rooms, bedrooms, offices, and attics, bringing it into contact with a wider range of valuable items like books, documents, and stored clothing, potentially leading to more widespread damage throughout the home.
How do I prevent Gray Silverfish from getting into my stored belongings?
The best way to protect your belongings is to make them inaccessible. The number one rule is to avoid storing items in cardboard boxes. Silverfish are attracted to cardboard both as a food source (the paper and glue) and as a dark, safe place to hide and breed. Instead, invest in high-quality, airtight plastic storage containers. This creates a physical barrier that they cannot penetrate. For items in closets and drawers, ensure they are clean and stored in a dry, well-ventilated space. Using sachets of lavender or cedar blocks can act as a minor repellent. Reducing overall household clutter is also key, as it eliminates many of their potential hiding places.
What is the most effective way to treat a Gray Silverfish infestation?
An effective treatment combines environmental control with chemical application. First, you must address the conditions that favour them. Use dehumidifiers and exhaust fans to lower the humidity in your home. Seal up cracks and crevices along skirting boards and around pipes to eliminate their hiding spots. A professional pest controller will then apply a targeted treatment. This usually involves a residual insecticide spray applied to all internal skirting boards and a fine insecticidal dust applied safely into voids like the roof space, sub-floor area, and wall cavities. This combination ensures that both the active insects and their hiding places are treated, providing long-lasting control.
Why has the Gray Silverfish become so common in homes?
The Gray Silverfish is a perfect example of an invasive pest that has adapted brilliantly to modern human lifestyles. While the Common Silverfish needs high levels of dampness, the Gray Silverfish can thrive in the relatively drier, warmer, and more stable conditions provided by insulated and climate-controlled homes. Our houses offer them protection from predators and harsh weather, a year-round stable temperature, and an abundance of food sources in the form of paper, books, textiles, and stored food. They have spread globally through the movement of goods and have found modern homes to be an ideal habitat, often allowing them to successfully out-compete and replace the less-adaptable Common Silverfish.
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Image Gallery
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