The confusion between “roach” and “cockroach” often stems from the different ways people refer to these insects. Many assume the two words refer to distinct species or groups. The distinction is not biological, but purely linguistic, setting the stage for a deeper look into the traits that define this order of insects and the specific species that interact most with humans.
Roach Versus Cockroach: A Question of Terminology
There is no biological difference between a roach and a cockroach; “roach” is simply the common, shortened form of “cockroach.” The word “cockroach” is an anglicized version of the Spanish word cucaracha. Both terms refer to any insect belonging to the scientific order Blattodea, which also includes termites. Any insect identified as a cockroach is also a roach, and vice versa.
Shared Defining Biological Traits
Insects within the Blattodea order share distinct physical and developmental characteristics. They possess a flattened, oval-shaped body that allows them to easily squeeze into narrow cracks and crevices. The head is often concealed from above by the pronotum, a large, shield-like plate. They also have long, slender antennae for sensing their environment and chewing mouthparts adapted for their omnivorous scavenging diet.
These insects undergo simple, or incomplete, metamorphosis, hatching from an egg into a nymph that resembles a smaller, wingless adult. The female protects her eggs in a hardened, capsule-like case called an ootheca, which can contain 10 to 50 eggs depending on the species. Cockroaches are nocturnal, relying on speed and ability to hide from light and predators.
Distinguishing the Common Pest Species
While general characteristics are shared, the few species considered pests exhibit notable differences in appearance and habit. The German cockroach (Blattella germanica) is one of the most common. It is identifiable by its small size—about one-half inch long—and two dark, parallel stripes running behind its head. This species reproduces rapidly and prefers warm, humid locations within homes, such as kitchens and bathrooms.
The American cockroach (Periplaneta americana) is the largest common pest species, reaching up to two inches in length. It is reddish-brown with a distinct yellowish, figure-eight pattern on the back of its head. These insects are often found in damp, dark areas like basements, sewers, and drains. They are also capable of flying short distances.
The Oriental cockroach (Blatta orientalis) is a dark brown or shiny black insect, about one inch long. It is sometimes called a “water bug” due to its preference for cool, moist environments. The females of this species have very short, non-functional wing pads. They also move more slowly than their counterparts.