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Today on Animal Fact Files we’re discussing silverfish. For more facts on cool critters, don’t forget to subscribe! Silverfish were a request by lapuli the lapis lazuli spider. Thanks for the suggestion!

Silverfish have a confusing name on multiple levels, so let’s try and break it down. They belong to the order Zygentoma along with animals commonly called firebrats. Firebrats and silverfish look similar and their names are often used interchangeably. Both of these animals are also commonly called bristletails, though, that’s not much help either. The order Zygentoma was once called Thysanura and included silverfish and firebrats as well as jumping bristletails who now belong to a completely different order of animals (Archaeognatha). Whew! Okay… maybe we just need to start over...

Today on Animal Fact Files we’re discussing animals from the Zygentoma order who are often commonly called silverfish and sometimes called firebrats or bristletails. And knowing our luck this will all change again with reclassification, but, hey, at least it gives you an idea. Common names in the animal world can lead to some serious confusion. Which brings me to the second point we need to address: the “fish” in silverfish. Now, if you’re a veteran of AFF, first of all, thanks for staying even through our antics, and secondly, you probably have a decent idea of what an arthropod looks like versus a fish. Silverfish are not fish. They probably garnered this name because of their fish-like movements, but they’re still arthropods like the stick insects, scarabs, and black widows we’ve discussed previously. Anyway, on to the silverfish (and firebrats)!

Silverfish live throughout the world, however, those of you who have seen one in real life likely saw it in your home. There are nearly 400 different species in the Zygentoma order, and some species are considered pests since they enjoy living in the spaces we also inhabit. They’re drawn to our homes because we provide them a veritable banquette. In the wild, silverfish eat algae and lichen, but in our homes they’ll happily munch on sugar, cereal, glue found in book bindings and wallpaper, and certain kinds of fabric. Yum. They can live nearly a year without eating, though. Silverfish themselves are eaten by spiders and predatory insects. In our homes they’re typically found in basements, bathrooms, garages, and hiding under unread copies of the Lord of the Rings with animals commonly called firebrats preferring warmer, drier areas. They avoid light at all costs and will quickly scurry to a new hiding spot if disturbed. In the wild they live in caves, deserts, leaf litter, ant and termite nests... yes, not all silverfish are found trapped in our bathtubs and some prefer the company of ants over housecats.

When in the company of each other, silverfish can produce more than 100 eggs in their lifetime after fertilization - however, parthenogenesis has been observed in some species. Not all species have been observed for reproduction methods but what we do know is that silverfish eggs are fertilized by a spermatophore which is picked up by females after it has been deposited beneath a silk thread structure made by the males. The female will lay the eggs one to three at a time in hidden places such as under rocks, and the eggs will hatch within three to six weeks. The babies are born looking like tiny versions of their parents and will molt as they reach their adult size. On average, silverfish are less than a centimeter (0.35in / 9mm) in length, though they can grow to be as big as ⅗ inch (15mm) - though that’s not including their tail-like structures called caudal filaments. They can live up to four years depending on the species.

I would say you could probably guess what color silverfish come in, but with all that naming debauchery we had to discuss earlier I wouldn’t blame you for being skeptical. Many silverfish are silver with soft, moth-like shimmery scales. Firebrats will often appear darker and more mottled in color. And other members of the Zygentoma order can appear in other colors as well. They have flattened bodies, either rudimentary or completely no eyes at all, and no wings. These arthropods are commonly referred to as primitive because they go way back in the fossil record and seem to have appeared relatively early in the arthropod timeline. In fact, until 1926 the oldest insect fossil discovered was an animal from the Zygentoma order.

For more facts on silverfish, take a look through the links in the description. Leave a comment with your thoughts on these fishy insects. Thank you for watching and give a thumbs up for more Animal Fact Files.