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Cockroach

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Cockroaches are insects of the order Blattodea (the name Blattaria is often used, but it is not interchangeable "Blattaria" includes a number of extinct taxa which do not belong in the cockroaches, so, in technical terms, Blattaria is a polyphyletic group, and the name Blattodea is therefore preferred). The names of the order are derived from Greek blatta, meaning "cockroach". There are roughly 3,500 species in 6 families. Cockroaches exist worldwide, with the exception of the polar regions and in elevations above 2,000 m (6,500 ft).

The English word cockroach is derived from the Spanish cucaracha, meaning "chafer, beetle".

Among the most well-known species are the American cockroach, Periplaneta americana, which is about 3 cm long, and the German cockroach, Blattella germanica, about 1½ cm long. Tropical cockroaches are often much bigger, and in turn prehistoric forms such as the Carboniferous Archimylacris and the Permian Apthoroblattina were several times as large as these. When infesting buildings, cockroaches are considered pests; out of the thousands of species, however, only a handful fall into this designation.

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Evolutionary history and relationships

The earliest cockroach-like fossils are from the Carboniferous period between 354–295 million years ago. However, these fossils differ from modern cockroaches in having long ovipositors and are apparently the ancestors of mantids as well as modern cockroaches. Current evidence strongly suggests that termites have evolved, in turn, directly from true cockroaches. The first fossils of "modern" cockroaches with short ovipositors appear in the early Cretaceous. Mantodea, Isoptera, and Blattodea are usually combined by entomologists into a higher group called Dictyoptera.

Biology

Cockroaches are generally either scavengers or omnivores. The exception to this is the wood-eating Cryptocercus species found in China and the United States. Although they are incapable of digesting the cellulose themselves, they have a symbiotic relationship with a protozoan that digests the cellulose, allowing them to extract the nutrients. In this, they are similar to termites and current research suggests that the genus Cryptocercus is more closely related to termites than it is to other cockroaches. Cockroaches are most common in tropical and subtropical climates. Some species are in close association with human dwellings and widely found around garbage or in the kitchen.

Female cockroaches are sometimes seen carrying egg cases on the end of their abdomen; the egg case of the German cockroach holds about 30–40 long, thin eggs, packed like frankfurters in the case called an ootheca. The eggs hatch from the combined pressure of the hatchlings gulping air and are initially bright white nymphs that continue inflating themselves with air and harden and darken within about four hours. Their transient white stage while hatching and later while molting has led to many individuals claiming to have seen albino cockroaches.

Common household roaches A. German cockroach, B. American cockroach, C. Australian cockroach, D&E. Oriental cockroach (♀ & ♂)
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Common household roaches
A. German cockroach, B. American cockroach, C. Australian cockroach, D&E. Oriental cockroach (♀ & ♂)

A female German cockroach carries an egg capsule containing around 40 eggs. She drops the capsule prior to hatching. Development from eggs to adults takes 3–4 months. Cockroaches live up to a year. The female may produce up to eight egg cases in a lifetime. In other words, in favorable conditions it can produce 300–400 offspring. Other species of cockroach, however, can produce an extremely high number of eggs in her lifetime. She lays up to 100 eggs in each egg sac. She only needs to be impregnated once to be able to lay eggs for the rest of her life, allowing one single cockroach to lay over a million eggs in her lifetime.

The world's largest cockroach is the Australian giant burrowing cockroach, which can grow to 9 cm in length and weigh more than 30 grams. Comparable in size is the giant cockroach Blaberus giganteus, which grows to a similar length but is not as heavy.

Cockroaches are mainly nocturnal and will run away when exposed to light. A peculiar exception is the Oriental cockroach, which is attracted to light, thus making it a far more annoying pest. Cockroaches are sometimes called the custodians of nature. They live only in houses where there are crumbs to eat or the garbage can is uncovered. They lay eggs inside the house's hollow walls.

The cockroach is also one of the hardiest insects on the planet, capable of living for a month without food and remaining alive headless for up to a week. It can also hold its breath for 45 minutes and has the ability to slow down its heart rate.

It is popularly suggested that cockroaches will "inherit the earth" after humanity destroys itself in a nuclear war. Cockroaches do indeed have a much higher radiation resistance than vertebrates, with the lethal dose perhaps 6 to 15 times that for humans. However, they are not exceptionally radiation-resistant compared to other insects, such as the fruit fly . Their habit of living under shelter is also likely to help them to avoid radioactive fallout in the aftermath of a nuclear attack.

The cockroach's ability to withstand radiation better than human beings can be explained in terms of the cell cycle. Cells are more vulnerable to effects of radiation when they are dividing. A cockroach's cells only divide once when in its molting cycle, which at most happens weekly. The cells of the cockroach take roughly 48 hours to complete a molting cycle, which would give time enough for radiation to affect it; but not all cockroaches would be molting at the same time. This would mean some would be unaffected by the radiation and thus survive .

Selected species

Oriental cockroach (Blatta orientalis). a, female; b, male; c, side view of female; d, young.
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Oriental cockroach (Blatta orientalis). a, female; b, male; c, side view of female; d, young.

Behavior

Cockroaches have been shown to make group decisions .

New research being conducted at the University of Florida shows that cockroaches leave chemical trails in their feces. Other cockroaches will follow these trails to discover sources of food, water, and where other cockroaches are hiding. One of the major implications of this research is a new technique in cockroach pest control. Cockroaches could be potentially removed from a home by leaving a chemical trail that leads away from the home.

Research has shown that group based decision making is responsible for more complex behavior such as resource allocation. A study where 50 cockroaches where placed in a dish with three shelters with a capacity for 40 insects in each, the insects arranged themselves in two shelters with 25 insects in each, leaving the third shelter empty. When the capacity of the shelters was increased to more than 50 insects per shelter, all of the cockroaches arranged themselves in one shelter. Researchers found a balance between cooperation and competition exists in group decision making behavior found in cockroaches. The models used in this research can also explain the group dynamics of other insects and animals. From the article, "For cockroaches, it seems, cooperation comes naturally." #redirect

Cockroaches and health risks

A 2005 national study on factors that affect asthma in inner-city children shows that cockroach allergens appear to worsen asthma symptoms more than other known triggers. This study, funded by National Institute of Environmental Health Sciences (NIEHS) and the National Institute of Allergy and Infectious Diseases (NIAID), is the first large-scale study to rank asthma triggers according to severity.

Additionally, a 2005 research study, sponsored by the [National Pest Management Association] (NPMA), shows a disparity in homeowner knowledge about this link. Only 10% of homeowners nationwide feel that cockroaches are a threat to their family’s health.

Habitat

Cockroach control, with cockroach baits, boric acid, and hydramethylnon gel.
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Cockroach control, with cockroach baits, boric acid, and hydramethylnon gel.

Cockroaches live in a wide range of environments around the world. Pest species of cockroaches adapt readily to a variety of environments, but prefer warm conditions such as found within buildings. Many tropical species prefer even warmer environments and do not fare well in the average household. Only a small handful of the 3,500 or so species of cockroach are suited to thrive in the typical home.

Pest control

There are numerous parasites and predators of cockroaches, but few of them have proven to be highly effective for biological control; wasps in the family Evaniidae are perhaps the most effective insect predators, as they attack the egg cases, and wasps in the family Ampulicidae are predators on adult and nymphal cockroaches (e.g., Ampulex compressa). House centipedes, however, are probably the most effective control agents of cockroaches, though most homeowners find the centipedes themselves objectionable.

Preventative measures include keeping all food stored away in sealed containers, using garbage cans with a tight lid, frequent cleaning in the kitchen, and regular vacuuming. Any water leaks, such as dripping faucets, should also be repaired. It is also helpful to seal off any entry points, such as holes around baseboards, pipes, doors, and windows with some steel wool and some cement or putty. Once a cockroach infestation occurs, chemical controls may help alleviate the problem. Bait stations, gels containing hydramethylnon, as well as boric acid powder, are toxic to cockroaches. A simple homemade cockroach trap is reported to be successful.

Popular culture

In popular culture, cockroaches are often regarded as vile pests, contrary to their fastidious habits. For example, English translations of Franz Kafka's The Metamorphosis generally read that the protagonist found himself transformed into a giant cockroach (although the original German is ambiguous.)

Movies which feature cockroaches include:

In the classic William Burroughs epic, Naked Lunch as well as in the subsequent movie, one of the main themes is an abundance of cockroaches and some of the characters resemble cockroaches in an uncanny way.

In the X-Files episode "War of The Coprophages" cockroaches are seen to group together to murder people. The character Dr. Berenbaum (based on the University of Illinois entomologist) suggests that it is actually swarms of flying cockroaches that are responsible for most UFO sightings (they generate an electro-static field which can be illuminated dependent on atmospheric conditions). In one of the scenes, a cockroach that escaped can be seen crawling over the camera, making it appear that the viewer's television has become infested. Though the shot was not planned, the producers decided to leave it in the episode.

The famous Mexican folk song, La Cucaracha, means "The Cockroach" in Spanish, and refers to cockroaches in some of its lines.

The cult computer game Bad Mojo deals with a person turned into a cockroach.

History

Some of the earliest writings with regards to cockroaches encourage their use as medicine. Pedanius Dioscorides (1st century), Kamal al-Din al-Damiri and Abu Hanifa ad-Dainuri (9th century) all offered medicines that either suggest grinding them up with oil or boiling. The list of ailments included earaches, open wounds and "gynaecological disorders".

Miscellaneous

External links

Wikimedia Commons has media related to:
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References

  • Firefly Encyclopedia of Insects and Spiders, edited by Christopher O'Toole, ISBN 1-55297-612-2, 2002
  • Insects: Their Biology and Cultural History, Bernhard Klausnitzer, ISBN 0-87663-666-0, 1987

 

From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.

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