Silverfish have retained their beauty as well as survivability during their 400 million years on Earth. Photo: Christian Fischer
By Kevin McKeon, Maine Master Naturalist
In 1843, geologist William Edmond Logan discovered a large, log-shaped rock specimen along the Gaspé Bay shoreline in Quebec. Sixteen years later, some scientists described it as a rotted yew tree that was full of fungi and had become fossilized. Other scientists insisted it was a 26-foot-long marine-based alga, or seaweed; other interpretations spawned differing debates. Then, in the early 2020’s, a similar specimen that was much better preserved was unearthed in the Rhynie chert rock formation in the Scottish Highlands, and scientists were able to study it with more clarity. Emerging from this study and published last January is the growing consensus that these fossils represent the existence, from about 400 million years ago, of a separate taxonomic kingdom of life — neither a plant, animal, protists, nor fungus — but a new kingdom! The research continues the taxonomic status of this extinct organism called Prototaxites.
During the reign of Prototaxites, which at 30 feet tall towered over all other existing, ankle-high plant life on Earth, a sea-dwelling crustacean crawled out of its ocean home to check out life on land — and decided to stay. Today, 400 million years later, it creepily crawls in the darkness, deathly afraid of the light; tiny, quiet crevices are its sanctuary. If bothered, it’ll speedily find another crack to slither into, awaiting darkness and stillness to return to foraging. It’s one of the first true land insects, found all over the planet, and has been around since way before the dinosaurs. It successfully evolved from that 400-million-year-old crustacean to live on land but has remained virtually unchanged since then. While other creatures evolved and diversified to form various life-lineages and their underlying species, this slithering insect continues to mirror its Devonian-period ancestors, who were crawling around Earth when today’s oil and coal deposits were beginning to be formed — a living fossil. Its silvery color and fish-like wiggling/crawling mobility give it its name: Silverfish, Lepisma saccharinum, the same creature we see on our bookcases, kitchens, and basements today.
The silverfish’s body is clothed with microscopic scales, similar to the scales on butterfly wings, evolved for protection. Silverfish have no wings but have two front antennae and three highly sensitive tail antennae used for sensing obstructions, vibrations, changes in air currents, pheromones for mating, and navigation; their sensing abilities are often described as like having eyes everywhere. Their actual eyes are very primitive, only able to sense changes in light. Like all of their crustacean ancestors and insect cousins, they molt as they grow; but unlike most of these others, silverfish continuously molt throughout their lives — up to 66 times during an eight-year lifespan, under ideal warm and humid conditions. And they can live without eating for almost a year as long as a moist environment is around that allows them to absorb water through their bodies. Without water, they’ll die in two or three weeks.
So, if there’s a leaky or “sweaty” water pipe, or any damp area in basements, kitchens and bathrooms, there are quite probably silverfish around. But they’re not harmful to us or our pets, carry no diseases or poisons, nor do they bite or sting. But they’ll eat our stuff that’s made from natural fibers like cotton and paper, including books and wallpaper, pillowcases and silk clothes, foodstuffs and pet food stored in very thin, paper wrappings – even stuff like soap, glue, and toothpaste. Part of its scientific name — saccharinum — refers to the silverfish’s love for carbohydrates. Since our homes provide ideal silverfish habitats, they have learned to gravitate towards humans; but they can and do live elsewhere: Leaf litter, rock piles, caves, and even other woodland creatures’ homes make a good living space for these insects.
Keeping areas fairly dry usually keeps silverfish away. Food-grade diatomaceous earth (DE), made from fossilized remains of tiny, hard-shelled aquatic algae called diatoms, has microscopic-sized sharp edges that act to scrape away the moisture-protective waxy coating on these slithery creatures’ scales, causing them to dry out and die. DE is used in our vegetable and flower gardens for that same effect against pests and is safe to use around pets — as long as it’s food grade DE. Care should be used due to the fineness of its dust. As with all pesticides, read, understand, and follow the labeling; the label is the law, and it’s there for your protection.
Silverfishes’ “indirect fertilization” reproduction rituals are ancient and rare among insects, beginning with vibrating bodies and the touching of antennae, after which the male quickly runs away; it’s up to her to catch him. If she does, he’ll stop and drop a sperm packet for her to pick up. Her small white eggs are laid singly or in small groups of 30 or less, turning brown after 20 days under ideal warm, humid conditions, but over 40 days when cool and drier. Hatchlings look like small adults, growing to maturity in about a year. Silverfish display higher activity rates in — you guessed it — warm, humid conditions. They don’t experience dormancy periods, remaining active year-round.
Ecologically, silverfish are considered valuable as a detritivore, facilitating organic material breakdown and soil-building as they feed on plant debris, rotting wood and leaves, and small, dead, soil-living creatures. However, in the archival worlds of museums and libraries, their penchant for paper goods, book-bindings, and ornate wallpaper make them a feared, unwanted pest.
Author’s note: I will be assisting with the Maine Master Naturalist course of classes throughout 2027 at the Wells Reserve at Laudholm Farm. Applications are being accepted until Oct. 9 for this course at https://mainemasternaturalist.org/ .
The post Silverfish: Ancient Creatures Who Will Gladly Move into Your House appeared first on Sanford Springvale News.
