The Grey Silverfish: An existing pest in North America and a spreading problem in Europe
The grey silverfish, Ctenolepisma longicaudatum, AKA “longtail silverfish” seems to be getting a lot more attention these days around the globe.
Although it has been present in the United States for some time, we have seen this species aggressively spread across all parts of Europe, leaving lots of damage to a wide range of materials in its wake.
These insects are synanthropic and rely on man to supply them with food and a living environment (synanthropic = ecologically associated with humans).
Grey silverfish can be differentiated from the common silverfish, Lepisma saccharinum by their extra-long bristletails.
Two hair-like cerci and a central filament called an epiproct make up the three long bristles coming off the tail end of this pest.
These bristles are nearly as long as the body of the adult silverfish. Grey silverfish also have barbed hairs (setae) around the outside of their bodies.
Larger than the common silverfish, grey silverfish can get up to 25 mm (nearly 1-inch) in length.
Insects Limited Video of Grey Silverfish: https://youtu.be/yA5TSJETaKI
Another important factor that sets grey silverfish apart is its ability to survive where other related species in the family Zygentoma (formerly Thysanthura) cannot.
Grey silverfish are more resilient to lower humidities and can survive at 55% whereas 70% is needed for common silverfish making it more difficult to control compared to common silverfish and firebrats Thermobia domestica who can be controlled by simple moisture or temperature adjustments.
[Image of a grey silverfish head and setae by Christian Dressen, via museumpests.net]
The main reason that silverfish are pests is because they can feed on and destroy books, paper and other belongings. Only a handful insects (termites, wood beetles) have the ability to break down the cellulose in books and paper, but silverfish have enzymes in their digestive system that allow them to receive nourishment from these items.
Grey silverfish seem to have spread like wildfire across most parts of Europe over the past decade. The species likely originated in South Africa, and it is argued that later introduction to North America is more likely than having origins there. Recorded first time in UK and in Norway in 2014, they are now in every country in Europe as well as Eastern European countries. In Germany, it has reported that 99% of silverfish problems stem from grey silverfish. They have been reported across the U.S. but mainly in the southernmost states and from the Midwest to California. They are voracious feeds and can do lots of damage in a relatively short time frame.
Grey silverfish can live from 5 – 7 years and females will lay approximately 50-60 eggs per year. They continue to molt even after they reach the adult stage.
[Grey silverfish image by Christian Dressen via museumpests.net]
This elongated molting ability makes killing them with residual chemicals a bit harder as they can shed the pesticide exposed exoskeleton. Sexual maturity is reached sometime after 16 months.
Monitoring silverfish with baited sticky traps such as the Trapper Museum Monitor is currently the best means of locating problem areas. Removing possible food sources and sealing floor crack and other harborage areas can be means of reducing populations.
Related Insect and Pheromone Posts
Read more about insects and pheromones in these related posts:
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