Cockroaches are insects of the Order Blattodea. The names of the order are derived from Greek language 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 metres (6,500 feet). Cockroaches are also simply known as "roaches".

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 3cm long, and the German cockroach, Blattella germanica, about 1¨öcm 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.

Biology

Cockroaches are generally either scavengers or omnivorous. 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 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 (¡Ï & ¡Î)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 favorable conditions, it can produce 300-400 offspring. Other species of cockroach, however, can produce an extremely high number of eggs in a lifetime. Laying 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 a single 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.

Habitat

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.

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.

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