The term “potato bug” is a common but imprecise label used across different regions of the United States to describe three completely unrelated arthropods. These species range from a small, striped beetle that feeds on leaves to a large, wingless insect that burrows underground, and a tiny, segmented crustacean found in moist soil. Accurate identification relies on visual and behavioral cues.
The Striped Leaf-Eater (Colorado Potato Beetle)
The insect most often associated with the name “potato bug” in agricultural settings is the Colorado Potato Beetle (Leptinotarsa decemlineata), a significant pest of nightshade crops. Adult beetles are identified by their convex, dome-shaped back, which is about 3/8 inch long. Their hard outer wings, known as elytra, feature a bright yellow or orange background marked with ten black longitudinal stripes.
The immature stage of this beetle is a soft, hump-backed larva that can grow up to 1/2 inch in length. These larvae are a shiny reddish-bronze color with a black head and two rows of black spots running down each side of their body. Both the adults and the larvae are primarily found feeding on the foliage of potato, tomato, and eggplant plants, where females lay clusters of orange-yellow eggs on the undersides of leaves.
The Headed Ground Dweller (Jerusalem Cricket)
In the Western United States, particularly California, the name “potato bug” often refers to the Jerusalem Cricket (Stenopelmatus species), a large, flightless insect. These robust creatures can measure up to two inches in length and are characterized by a disproportionately large, bulbous head and a broad, shield-like thorax. Their heads are typically a pale, yellowish-orange color with eyes set far apart.
The body is stout and glossy, ranging from light tan to a reddish-brown, often displaying dark, segmented banding across the abdomen. Jerusalem crickets lack wings and are equipped with thick, powerful legs adapted for digging through soil. They are nocturnal and spend most of their lives underground, rarely emerging above the surface, where they use their strong mandibles to forage and defend themselves.
The Segmented Roll-Up (Pillbugs and Sowbugs)
Two types of small, segmented creatures, the Pillbug and the Sowbug, are commonly called “potato bugs,” though they are technically terrestrial crustaceans, not insects. Both species are dark gray, oval-shaped, and covered in a series of overlapping, armored plates, measuring less than 1/2 inch long. They thrive in damp, dark environments, frequently found under logs, rocks, or garden debris where moisture is abundant.
The difference lies in their defense mechanism: the Pillbug, or roly-poly, possesses the ability to curl its body completely into a tight, protective ball, a process known as conglobation. The Sowbug, however, is slightly flatter and lacks this ability, instead scurrying away when disturbed. Sowbugs also have uropods, two small tail-like appendages, that visibly extend from the rear of their segmented body, a feature absent on the Pillbug.