Editor’s Note: The following article appeared on Mike Merchant’s blog, “Insects in the City,” which can be found at http://insectsinthecity.blogspot.com. The blog offers readers news and commentary about the urban pest management industry and is excerpted here with permission of the author.
If one were to poll pest control customers about what they thought was the most disgusting insect, there’s a good chance the American cockroach would come out on top. First of all, it’s large and scary, it’s very fast and, where it proliferates, it stinks. Add to this that the American cockroach is one of the few cockroaches that readily flies and you’ve got a disgusting pest.
Since few people want to admit to having giant cockroaches in their homes, alternative names are often given to the American cockroach, water bug and palmetto bug being the two most common. One of our largest cockroaches (reaching lengths of just over two inches), they often look much larger to a surprised customer. In fact, they are often described as three or four inches long.
Identifying American Cockroach Egg Cases
Unlike the German and brownbanded cockroaches, female American cockroaches concurrently mature not only the 16 eggs destined to be oviposited and packaged in the next egg case, but also the 16 eggs that will constitute the next egg case. Consequently, females feed (and forage) almost continuously to nourish these eggs, and this is interrupted only by bouts of egg case deposition.
Females often glue their oothecae to a suitable rough surface, and they often scrape paint, cardboard and other materials onto the egg case, camouflaging it well with the surroundings; presumably this is meant to protect the egg case from parasitoids.
The ootheca of the American cockroach is usually about 8 mm long and 4 mm wide, and weighs about 95 mg. Oothecae contain enough water for the eggs to complete embryo development. As in all pest cockroaches, the eggs are arranged in two parallel rows within the ootheca, with the keel (suture line), which is used for respiration, pointing up. The synchronized effort of the hatching nymphs forces the keel to open.
(Source: Handbook of Pest Control, 10th Edition)
American cockroaches, while much longer lived and slower to reproduce than the more common German cockroach, can become quite prolific in the right environment. While an American cockroach female only produces about 16 eggs per ootheca (egg case), compared to the German cockroach’s 36, she lives much longer and produces more oothecae and potential offspring over her lifetime (an average 360 offspring versus the German cockroach’s 320 offspring). Left undisturbed, American cockroaches can build up impressive populations, as anyone who has opened an infested sewer manhole cover can attest.
I guess one of the things that has always impressed me about the American cockroach is its ability to survive in places with little food. They are relatively common in urban sewer and storm drain systems, as well as steam tunnels and basements and storage areas of institutional buildings like schools, hospitals, prisons and factories. These cockroaches are often living on the edge, nutrition-wise, making do with feeding on glues and starches associated with boxes and papers. They are opportunistic feeders and while they prefer fermenting foods, they will feed on dog food in the lab and will readily feed on various cockroach baits.
My colleague Dr. Fudd Graham, from Auburn University, was recently inspecting a courthouse with a chronic American cockroach infestation. Following his nose, his inspection led him to a storage room that hadn’t been opened for over 18 months. The two tubes of cockroach bait Fudd applied were gone the next morning along with the cardboard on which the bait was applied.
Typical of many infested areas of buildings, this room had a floor drain that, due to lack of use, was dry. Dry floor drains are one of the most common entry points for American cockroaches to enter commercial buildings from sewage systems. Many people, even building maintenance workers, are unaware of the importance of periodically pouring a gallon or two of water into floor drains to fill the p-trap that is designed to block sewer gases and insects and other pests from entering buildings. A dry p-trap allows cockroaches to gain ready access to a utility room or food storage area in a building. Besides filling the p-trap, some companies have developed clever membrane devices that open for water flow, but close between use. Trapguard and Sureseal are two commercial products that can provide a long-term fix for gas and pest infiltration into storage and utility areas.
It’s important to remember that controlling American cockroaches has other benefits. Eliminating them helps reduce the potential food supply of rodents in a building. I’ll guess that most PMPs have seen the disembodied wings and legs of American roaches left on sticky traps. This often is evidence of mice or rats, which are fond of snacking on live roaches plucked from sticky cards. Additionally, ensign wasps are a common parasite of American and smoky brown cockroach oothecae, and are often seen flying around buildings that have an American cockroach infestation. While harmless themselves to people, the presence of these insects is a sign of cockroach presence in a building.
The author is an entomology specialist for Texas AgriLife Extension. Readers can contact him via email at firstname.lastname@example.org.