The term “potato bug” is a source of considerable confusion, as it does not refer to a single species but rather to several distinct, unrelated arthropods across different regions. This common name is applied to creatures that either feed on potatoes, live in the soil where potatoes grow, or simply have a similar appearance. Examining the physical characteristics and leg counts of the three most commonly named “potato bugs” reveals why their leg numbers vary widely.
The Isopod (Pillbug or Sowbug)
The creature most frequently encountered and dubbed a “potato bug” in gardens is the isopod, commonly known as a pillbug or roly-poly. These organisms are not insects at all but are classified as terrestrial crustaceans, placing them in the same subphylum as shrimp, crabs, and lobsters. This classification explains their higher number of walking limbs, which is 14 legs.
Pillbugs, scientifically known as Armadillidium vulgare, and their close relatives, the sowbugs (Porcellio scaber), breathe using gills and must therefore remain in damp environments to survive. They are scavengers that primarily feed on decaying plant material, contributing to the recycling of nutrients in the soil. Their preference for moist, dark conditions means they are often found under rocks, logs, and garden debris, where they may occasionally feed on tender sprouts or tubers.
The Colorado Potato Beetle
The Colorado potato beetle (Leptinotarsa decemlineata) is a true insect and a significant agricultural pest. As a member of the Class Insecta and Order Coleoptera (beetles), the adult beetle possesses the characteristic six legs. The adult is easily identified by its oval, convex shape and its bright yellow-orange body marked with ten distinct black stripes running down its wing covers.
Both the adult and the hump-backed larva stage feed voraciously on the foliage of potato plants, which is the origin of its common name. The larvae also possess six legs on their thoracic segments, though they appear quite different from the adult. A single female can lay hundreds of eggs, contributing to their rapid spread and their notoriety as a destructive force in potato fields worldwide.
The Jerusalem Cricket
A third creature sometimes called a “potato bug” is the Jerusalem cricket (Stenopelmatus species), a large, flightless insect found mainly in the western United States and Mexico. This nocturnal insect is a member of the Class Insecta, belonging to the order Orthoptera. Like the Colorado potato beetle, the Jerusalem cricket has six legs.
Its large, bulbous head and stout, spiny legs give it a distinct and somewhat alarming appearance, earning it regional nicknames such as “child of the earth”. The powerful front legs are adapted for digging and burrowing beneath the soil, where they forage for roots, tubers, and other organic matter, occasionally damaging potato crops in the process.