A family of cave-dwelling early humans is preparing a feast of mastodon meat. The cook bends down to retrieve a stone utensil and is startled to uncover a cockroach, which scurries into a rocky crevice.

We may never know whether such an event took place, but it could have. While humans have existed for an estimated 5 million years, fossil evidence indicates that cockroaches have been on Earth for more than 300 million.

“Cockroaches are considered one of the most successful groups of animals,” says entomologist Steven Jacobs. “Because they are so adaptable, cockroaches have adjusted to living with humans much more readily than humans have adjusted to living with them.”

Despite our best attempts to eliminate them, cockroaches thrive in nearly every corner of the globe. Worldwide, there are about 3,500 cockroach species, about 70 of which are found in the United States. Five of the most commonly encountered in Pennsylvania are German, brown-banded, Pennsylvania wood, Oriental, and American cockroaches.

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“The German cockroach is the most economically important urban pest,” Jacobs says. “It’s also the most common cockroach species found in houses, apartments, restaurants, hotels, and other institutions—not just in Pennsylvania, but in most parts of the civilized world.”

Adult German cockroaches are small—1/2 to 5/8 of an inch long—and tan to light brown, with two dark parallel lines running from the back of the head to the wings. They have fully developed wings but do not fly. The German cockroach usually is found in kitchens (near dishwashers, stoves, and sinks) and bathrooms.

German cockroaches prefer a warm, moist environment. They scavenge on a wide variety of foods, but are especially fond of starches, sweets, grease, and meat products. Garbage often is their principal food source. “Cockroaches seek mates, food, and water at night,” says Jacobs. “During the day, they hide in dark cracks or crevices that provide warmth and humidity.”

Cockroaches are persistent and hard to control. “These insects produce a large number of eggs and reach sexual maturity quickly,” Jacobs explains. “German cockroaches carry their eggs until hatching time, and because they are smaller than other cockroaches, they can hide more easily. A single female may spawn 10,000 descendants in one year.”

If not controlled, German cockroaches can become a nuisance and a health threat. “German cockroaches produce odorous secretions that can affect the flavor of foods,” says Jacobs. “When cockroach populations are high, you may notice this odor near the infestation.”

Disease-causing organisms such as bacteria, viruses, and protozoa have been found on cockroach legs and bodies. “These microorganisms can be deposited on food and utensils as cockroaches forage, putting people at risk for food poisoning, dysentery, diarrhea, or other illnesses,” Jacobs says. “Cockroach excrement and cast skins also can cause rashes, watery eyes, sneezing, and congestion in people with allergies.”

Although it’s difficult to keep cockroaches from entering your home via boxes, grocery bags, suitcases, and other containers, you can take steps to prevent a serious problem. “Sanitation is the key,” Jacobs says. “Clean up all spilled foods, including crumbs on the floor. Don’t leave dirty dishes overnight. Store cereal, crackers, cookies, flour, sugar, and bread in sealed, airtight containers.

“Empty garbage each evening into a sturdy container with a tight-fitting lid,” Jacobs continues. “You also may have to make structural modifications, such as caulking holes in walls where pipes pass into the kitchen and bathroom areas.”

The first step to controlling cockroaches, according to Jacobs, is to survey areas of known or suspected infestation. “Place sticky traps at strategic locations, such as under equipment or counters, against a wall, or in the corner of a floor, shelf, or drawer,” Jacobs explains. “Most commercially available traps come with bait to lure cockroaches. One week of trapping usually provides sufficient information.

“Historically, insecticidal dusts, sprays, and fogs were used to control cockroaches,” Jacobs says. “Recently, we’ve found that control is best achieved through the use of various cockroach baits, which come as stations, gels, or granular materials. But for pesticides to be effective, the chemicals must be applied into or near the sites where the roaches live. Be sure to follow all directions and safety precautions on labels to protect people, pets, and the environment.”

—Chuck Gill