Gray Silverfish Identification Guide
Ctenolepisma longicaudatum
The gray silverfish, also known as the long-tailed silverfish or urban silverfish, is a large species found in homes across North America. Distinguished by its dull gray color and exceptionally long tail filaments, it thrives in humid indoor environments and can damage paper, books, and fabrics.
Taxonomy
Gray Silverfish Coloration
Common color patterns to help identify gray silverfish
Gray Silverfish
Seasonal Activity
When gray silverfish are most active throughout the year
Where Gray Silverfish Are Found
Hover over states to see their names. Green regions indicate where gray silverfish have been reported.
Gray Silverfish Identification Guide
Physical Characteristics
The gray silverfish (Ctenolepisma longicaudatum) goes by many names. People also call it the urban silverfish, long-tailed silverfish, or paper silverfish. It is one of the largest silverfish species found in North American homes. Adults measure 12 to 19 mm long. This makes them larger than the common silverfish. Their bodies are covered in tiny scales that give them a dull gray to brownish color. They do not have the shiny metallic look of common silverfish.
The most striking feature is their very long tail filaments and antennae. These parts can be as long as their body. This is why they are called “long-tailed silverfish.” Their body is flat and shaped like a carrot, narrow at the back end. Like all silverfish, they have three tail-like parts at the rear and two long antennae at the head. They have small eyes and move with a quick wiggling motion that helps them escape danger.
Similar Species
Gray silverfish can look like other silverfish types:
- Common silverfish (Lepisma saccharina): Smaller at 12-13mm with a shiny silver-blue metallic look. They have shorter antennae and tail parts.
- Four-lined silverfish (Ctenolepisma lineatum): Similar size but has dark stripes down its back. The body is tan or brown with stripes.
- Firebrats (Thermobia domestica): Similar shape and size but with spotted gray and brown coloring. Firebrats like much hotter spots near furnaces and ovens.
Gray Silverfish Behavior and Biology
Habitat Preferences
Gray silverfish likely came from South Africa. They have spread around the world through trade. They do well indoors where temps stay between 68 and 80 degrees F. High humidity is key for their survival. Their eggs and young need moisture to grow.
Inside homes, gray silverfish like basements, bathrooms, kitchens, laundry rooms, and attics. They hide in dark, quiet places during the day. You might find them behind baseboards, inside wall spaces, under sinks, or in stacks of papers and boxes. They are also common in warehouses, libraries, and museums where paper products are stored.
Diet and Feeding Habits
Gray silverfish eat many things. Their diet includes starches, sugars, proteins, and fats. Common food sources include:
- Paper, cardboard, and book bindings
- Wallpaper and wallpaper paste
- Photographs and documents
- Cotton, linen, and silk fabrics
- Cereals, flour, and other pantry items
- Dead insects and shed insect skins
- Glue and adhesives
They can digest pure cellulose. This makes them a threat to archives, libraries, and paper collections. Gray silverfish can live several weeks without food. But they always need moisture to survive.
Reproduction and Lifecycle
Gray silverfish breed slowly compared to many pests. Females lay eggs in small batches. They place eggs in cracks and tight spaces. The eggs need high humidity to develop. Dry conditions reduce their breeding success.
Young silverfish, called nymphs, look like tiny adults. They shed their outer skin many times as they grow. The time from egg to adult takes 1.5 to 3 years depending on conditions. Their slow growth means a small problem can take 4 to 6 years to become a serious pest issue.
Activity Patterns
Gray silverfish are active only at night. They stay hidden in dark spots during the day and come out after dark to find food. They run very fast and can vanish into tiny cracks in seconds when scared. Their flat body lets them squeeze into spaces as thin as a credit card. Their speed, night habits, and hiding skills make gray silverfish hard to spot until there are many of them.
How We Treat for Gray Silverfish
Our gray silverfish control combines direct treatment with moisture control and sealing entry points. We address both the current problem and the conditions that let these pests thrive in your home.
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Full Inspection: Our licensed technicians inspect your home to find silverfish activity, entry points, and moisture problems. We check common hiding spots like basements, bathrooms, and storage areas. We look for signs of damage to books, papers, and fabrics.
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Interior Treatment: We treat baseboards, cracks, and other spots where gray silverfish hide and travel. We use products that silverfish cannot detect. They contact the treatment as they move along their normal paths. This leads to better control.
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Exterior Treatment: We treat around the foundation and entry points outside your home. This creates a barrier that stops new silverfish from getting inside while we control those already there.
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Moisture Control Tips: Gray silverfish need high humidity to survive and breed. Our technicians will suggest ways to cut moisture in problem areas. This may include dehumidifier use, better airflow, and fixing plumbing leaks.
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Ongoing Prevention: We suggest triannual service (three times per year) to keep your home protected. Gray silverfish are stubborn pests with long lifespans. Regular treatments help keep them under control and catch new activity early.
References and Further Reading
- Silverfish and Firebrats - University of California IPM
- iNaturalist - Long-tailed Silverfish (Ctenolepisma longicaudatum)
- Norwegian Institute of Public Health - Long-tailed Silverfish Biology and Control (PDF)
- Insects Limited - Grey Silverfish: A Spreading Problem
- Wikipedia - Ctenolepisma longicaudatum
Other Silverfish
Explore other species in the silverfish family
Commonly Confused With
Gray Silverfish are often mistaken for these similar pests
Where Gray Silverfish Are Found
Hover over states to see their names. Green regions indicate where gray silverfish have been reported.
Common Questions about Gray Silverfish
How can I tell a gray silverfish from a common silverfish?
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Gray silverfish are larger than common silverfish, measuring 12-19mm compared to 10-13mm. They have a dull gray or brownish color without the metallic sheen of common silverfish. Their most distinctive feature is their very long tail filaments and antennae, which can be almost as long as their body.
Is the urban silverfish the same as the gray silverfish?
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Yes, the urban silverfish is another common name for the gray silverfish. Scientists once classified it as a separate species (Ctenolepisma urbanum), but it is now recognized as the same species as the gray silverfish (Ctenolepisma longicaudatum). It is also called the long-tailed silverfish and paper silverfish.
Are gray silverfish harmful to humans?
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Gray silverfish do not bite, sting, or transmit diseases to humans. However, they can cause significant damage to books, papers, wallpaper, photographs, and fabrics by feeding on starches, cellulose, and proteins found in these materials.
Why do I have gray silverfish in my home?
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Gray silverfish are attracted to humid environments with temperatures between 68-80 degrees Fahrenheit. They often enter homes seeking moisture and food sources like paper products, glue, and starchy items. Poor ventilation, water leaks, and stored paper goods create ideal conditions for them.
Where do gray silverfish hide during the day?
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Gray silverfish are nocturnal and hide in dark, protected areas during daylight. Common hiding spots include behind baseboards, inside bookcases, under furniture, in wall voids, behind wallpaper, and in storage boxes containing paper or fabric.
How long do gray silverfish live?
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Gray silverfish have a long lifespan compared to most household insects. Under ideal conditions, they can live 2-3 years, though the full life cycle from egg to reproducing adult takes 1.5-3 years depending on temperature and humidity levels.
Will reducing humidity help get rid of gray silverfish?
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Yes, reducing indoor humidity is one of the most effective prevention strategies. Gray silverfish eggs and young nymphs require higher moisture levels to survive. Using dehumidifiers, improving ventilation, and fixing water leaks can make your home less appealing to these pests.
Can gray silverfish damage my book collection?
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Yes, gray silverfish are known pests of libraries and archives. They feed on the glue in book bindings, paper, and photographs. Over time, an infestation can cause irreparable damage to valuable books and documents.
With five years of hands-on experience in the pest control industry, George Schulz is a registered technician with the Virginia Pest Management Association and a proud third-generation professional in a family business that's been protecting homes for over 57 years. He manages and trains a team of service pros while also leading internal research efforts—recently spearheading a deep-dive review of thousands of documents on pest control materials to hand-pick the most kid and pet friendly, most effective solutions tailored specifically for homes in the DC metro area.