It’s from one and one-half to two inches long (not counting the antennae, which are longer than the body) and is a beautiful dark golden brown in color. It’s one of Chicago’s most numerous (albeit nontaxpaying) residents. It’s the American cockroach.
Cockroaches are found virtually everywhere. The first time I saw an American cockroach, my reaction (which I suspect is typical) was, “That’s it! I’m finding a place where I will never have to see one of these things again!” A little research revealed that even a move to the research stations of Antarctica would not be far enough — the scientists, no doubt inadvertently, brought Periplaneta americana with them. Roaches have even trekked to Greenland. So much for getting away from them. Research has shown people will tolerate as many as five American cockroaches in their homes per week. (I would like to know who the subjects of that research were!)
Most of us think of cockroaches as dark, disease-carrying, scuttering insects that should be obliterated. Because they are more active at night and in dark places, we attribute all kinds of nasty traits to them, including evil. The truth is, the cockroach is simply a biological organism and has certain environmental and nutritional needs, just as more charismatic nocturnal animals do. After all, white-tailed deer are active mainly at night and provide a home for deer ticks, which in turn carry debilitating Lyme disease. Yet, when you see a deer, chances are you still say, “Awww, isn’t that cute?”
Let’s debunk a couple of these myths, by the way:
Myth: Cockroaches are afraid of light.
Reality: Cockroaches prefer darkness, but are not afraid of light. They do run when you wake up and turn on a light, but not because of the light. They are extremely sensitive to surface vibrations; they can detect a movement of less than one-millionth of a millimeter. They are reacting to the air currents and surface vibrations caused by your movement, not to the light.
Myth: All cockroaches are filthy, disease-carrying bugs.
Reality: Cockroaches carry many diseases only because they tend to congregate in warm, damp places like sewers and pipes where they pick up disease organisms. A cockroach like the Madagascar hissing cockroach, which lives in a natural habitat, is not the same threat to other animals as our Chicago friends. According to the Audubon Field Guide to Insects and Spiders, it is a myth that cockroaches transmit diseases to humans.
Of the thousands of cockroach species, only a handful, including P.a., are considered to be pests. Most cockroaches (for example, the Madagascan hissing cockroach mentioned above) live in natural environments, filling a niche in their habitat, and rarely have contact with humans. The Madagascan lives under the detritus of the forest floor, munching away on decayed organic material, a niche that is very similar to that of the millipede.
Our Chicago varieties are for the most part pests. There is the German cockroach, which is small, numerous, and often visible. The Oriental cockroach is a black, one-inch insect and does not seem to be as common as the German and American. By the way, the names of cockroaches generally are incorrect. The Oriental and American cockroach most likely originated in Africa or South Asia. The German cockroach probably emigrated from West Africa. Another of the American cockroach’s common names does provide a clue as to how they became so widespread — ship cockroach (Captain Bligh described techniques used for killing them on the Bounty). Another nickname for the American cockroach is the Bombay canary! The most famous name for the American cockroach may be that publicized by humorist Dave Barry in his weekly column — the state “bird” of Florida. In spite of these names comparing P.a. to a bird, the American cockroach is only medium-sized when compared to some other species.
All three species consume foodstuffs and crops, act as vectors of various diseases, and carry parasitic organisms that are dangerous to man and domestic animals. They leave a noxious odor on the food they contaminate with their feces; they cause allergic reactions in humans through four means:
- Direct contact
- Injectant (from bites)
- Ingestant (from ingesting food that has been partially eaten by cockroaches)
That said, however, the main problem people have with cockroaches is emotional. Other insects, for example, fleas and mosquitoes, are far more serious vectors of disease in man and livestock. Locusts cause far more damage to crops.
Why do cockroaches live with us in this love-hate relationship? They require warm temperatures and high relative humidity (between 40 and 50%). Even in climates like Chicago’s, our homes provide both in abundance. They are omnivorous, eating bark, fruit, vegetables, termites, young bedbugs, and parasitic mites. At one aquarium, they ate reptile eggs. They’ve been known to gnaw on people’s feet, hands, and more delicate areas, causing abrasions and allergic reactions. Under overcrowded or stressful conditions, cockroaches will even eat each other, usually recently molted nymphs, copulating pairs, and injured adults — in other words, the most vulnerable. The contents of our cupboards suit them just fine. If you are one of those people who believe that a good housekeeper who keeps food tightly sealed and crumbs cleaned up will never have roaches, think about the following table, which shows how long (in days) American cockroaches can survive without food and/or water:
|No food or water||28||42|
|Dry food, no water||27||40|
|Water, no food||44||90|
Researchers believe the female survives longer than the male due to greater fat reserves (perhaps at least one thing we as humans can relate to!). The point is, no one can avoid cockroaches simply by trying to be immaculate. The cockroach’s food requirements are simply too minimal.
Although cockroaches may bother us, they have their problems, too. Several animals prey on cockroaches and their larvae and eggs, including some spiders, parasitic mites, beetles, ants, amphibians, reptiles (primarily geckos and anoles), birds, and mammals. One Peruvian bird, Troglodytes audex, is known as the cucarachero because of its cockroach consumption. The bird removes the head and wings to down the insect. Believe it or not, man is another cockroach predator. Cockroaches and their eggs are consumed by people in Australia, Thailand, China, Japan, and other parts of the Far East. They are eaten as food and for medicinal reasons.
As in other insects, many tissues of the cockroach can regenerate themselves, including eyes, antennae, cerci, and exoskeletal features, all of which regenerate over a number of molting cycles. The American cockroach is used in endocrine research because they can regenerate their prothoracic gland, a useful feature.
Cockroaches are unique among insects in that they can regenerate their legs in “all-or-none” fashion in a single instar (an instar is the period between molts). In other words, the leg either regenerates in one shot, so to speak, or it doesn’t. The new leg is not a replica — it is smaller and has only four segments rather than the original five. As the cockroach goes through several molts, the new leg does grow larger. This is a good adaptation for the cockroach, because two points along its leg yield easily to tension. (By the way, the only other insect that is known to regenerate a body part in all-or-none fashion is the butterfly, which can regenerates its wing imaginal discs.)
You’re no doubt curious about the love life of the American cockroach. In a three-dimensional vertical space (between your walls comes to mind), males live above the females. When the female is ready, she emits a sex pheromone, which makes the male come a-runnin’, so to speak. The stronger the scent, the straighter his path toward her. The female exhibits a calling pose — she lowers her abdomen slightly and spreads her 8th and 9th terga (dorsal plates) so the underlying tissues are exposed. When the male antennates her, she assumes a motionless stance. The male turns 180º, raises and flutters his wings, and moves backwards. The female must be receptive — courtship is a conflict situation in which there is a high potential for aggressive responses. (In addition, remember that mating cockroaches are vulnerable to the cannibalistic tendencies of their cronies.) In some encounters, the female mounts and the male attempts copulation; in others, the male attempts copulation without female stimulation. During her four-year lifetime, the American cockroach can produce 1,000 offspring. Cockroach nymphs are well developed when they hatch, resembling miniature adults, but it takes a full year and several molts before they reach maturity.
You probably don’t like cockroaches any more than you did before, but maybe you can look at them a little more objectively — they breathe, they eat, they drink, and they produce young, just like any other animal, all the while paying us the ultimate compliment of sharing our taste in both food and housing.
The American Cockroach. William J. Bell and K.G. Adiyodi, editors. Chapman and Hall Ltd.: London 1982.
The Biology of the Cockroach. D. M. Guthrie and A. R. Tindall, editors. St. Martin’s Press: New York 1968.
Copyright © Diane L. Schirf