American Cockroach

Information provided by Ohio State University.

The American cockroach is a pest in residences and large commercial buildings where food is prepared or stored such as restaurants, grocery stores, bakeries, breweries, pet shops, food processing plants, etc. This cockroach occurs both outdoors and indoors; it commonly breeds in sewer systems and underground utility networks, from which it then may invade structures. It is the most common cockroach species in city sewer systems. It favors microhabitats with high humidity. The American cockroach sometimes is commonly called a "waterbug" or "palmettobug."

Identification
Adult American cockroaches are approximately 1.3 to 2.1 inches long; they are among the largest of the cockroach pests in homes. These cockroaches have a somewhat flattened oval shape, spiny legs, and filamentous antennae that are uniformly brown and as long as or longer than the body. Adults have fully developed wings, but they seldom fly when disturbed. The forewings are glossy reddish brown to dark brown, sometimes paler towards the sides and tip. The pronotum ("shield" behind the head) is reddish brown with a yellowish brown border.

Nymphs (immature stages) resemble the adults, but they are smaller and lack wings. Nymphal early instars (the stage between molts) are grayish brown with a paler lower surface. Older nymphs are uniformly reddish brown. Wing pads are evident in third or fourth instar nymphs. Egg cases (oothecae) are mahogany brown to blackish brown and about 3/8 inch long. The eggs in each egg case are arranged in two parallel rows, usually with 14 to 16 eggs total.

Life Cycle
A female American cockroach produces 6 to 14 egg cases during her lifetime. She carries her egg case for a few hours or days after it is formed, then she drops or glues it in a sheltered site, often a crack or crevice, near a food source. The eggs hatch within 38 to 49 days (average = 44 days). Early instar nymphs molt (shed their skin) at approximately monthly intervals. Older nymphs molt at more variable intervals, usually every 1 to 6 months. The nymph's body weight approximately doubles between molts. There are 10 to 13 nymphal instars. Development time (egg to adult) of the American cockroach is greatly influenced by temperature; it averages about 15 months (range 9.5–20 months). The adult life span may be >1 year. Adult American cockroaches can continuously reproduce when conditions are favorable.

Habits
The American cockroach favors dark sites with high humidity. It most often is associated with sewers, steam tunnels, boiler rooms, and basements, especially around pipes and drains. This species also can occur in the landscape, reaching high numbers in moist, shaded leaf litter under trees and shrubs, in rotting stumps or logs, or in planters. It also may congregate under roof overhangs and in the roof gutter system where leaves and other debris provide both food and shelter for these large cockroaches. All stages require harborage sites where they hide during the day, coming out to forage for food and water at night.

The American cockroach is a scavenger that feeds on decaying organic matter and a variety of other foods. It is particularly fond of fermenting foods.

Damage and Injury
Cockroaches typically are not tolerated by humans, and the mere presence of these insects is considered a nuisance. Furthermore, American cockroaches often are responsible for significant fouling of food products and other items. American cockroaches also produce a strong, unpleasant odor, which they convey to harborage sites and food items.

The American cockroach can harbor numerous bacterial and viral pathogens in its feces or on its body. It can contaminate food and food-preparation items and surfaces with disease organisms that result in food poisoning, dysentery, or diarrhea.

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