Silverfish and centipedes are common household invertebrates often confused due to their shared presence and somewhat similar appearances. Despite both being considered pests, they are fundamentally different organisms, belonging to separate biological groups with distinct characteristics, behaviors, and ecological roles.
Meet the Silverfish
Silverfish are small, wingless insects known for their distinctive, silvery-gray color and fish-like movements. An adult silverfish typically measures between 10 to 25 millimeters (0.3 to 1 inch) in length, with a flattened, tear-drop shaped body that tapers towards its rear. They possess two long antennae at the front of their head and three prominent, bristle-like appendages, called cerci, extending from their tail end.
These nocturnal creatures prefer damp, dark environments with high humidity, usually between 75% and 95%. Common indoor habitats include bathrooms, basements, attics, and kitchens. Silverfish primarily feed on starches and sugars, consuming items like paper, glue in bookbindings, wallpaper, cereals, and even textiles like cotton and linen. While they do not bite humans or transmit diseases, they can cause damage to property by feeding on household items.
Meet the Centipede
Centipedes are elongated arthropods with numerous legs and rapid movement. Their bodies are flattened and segmented, with each segment typically bearing one pair of legs. The number of leg pairs varies by species, ranging from 15 to 191 pairs, meaning no centipede actually has exactly 100 legs despite their name. Centipedes have a pair of long antennae and specialized forcipules, located behind the head, which are used to inject venom into their prey.
Centipedes are predatory animals that hunt other insects and small arthropods, including spiders, cockroaches, and even silverfish. They are typically found in moist, dark environments, such as under rocks, logs, leaf litter, and sometimes indoors in damp basements or bathrooms. Centipede bites can be painful to humans, causing localized swelling and redness, but they are generally not dangerous or life-threatening, with severe reactions being rare.
Key Distinctions
Silverfish and centipedes differ significantly in their biological classification. Silverfish are true insects, belonging to the class Insecta. In contrast, centipedes are members of the class Chilopoda, which falls under the subphylum Myriapoda, a group of arthropods that also includes millipedes. This distinction means they are as different from each other as an insect is from a spider.
Their anatomical differences are also pronounced. Silverfish have a wingless, tear-drop shaped body with six legs and three tail-like appendages. Their movement involves a wiggling or fish-like darting motion, and they cannot climb smooth surfaces. Centipedes possess an elongated, flattened body with numerous leg pairs, one per segment, and lack tail-like appendages. They move with a rapid, undulating motion of their many legs, allowing them to navigate varied terrains with agility.
Beyond appearance and movement, their diets and behaviors set them apart. Silverfish are scavengers, consuming starchy and sugary materials, and are nocturnal. Centipedes are active predators, utilizing venomous forcipules to subdue their prey. While their bites can be painful, they are typically not dangerous to humans, and centipedes are often considered beneficial for controlling other household pests.