Cockroaches are insects of the order Blattodea. 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 6,500 ft (2,000 m).
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 1.5 cm long. Tropical cockroaches are often much bigger. When infesting buildings, cockroaches are considered pests.
The earliest fossils of cockroaches are from the Carboniferous period between 354-295 million years ago.
Cockroaches are generally either scavengers or omnivores with the exception being 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. They 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.
A female German cockroach carries an egg capsule containing around 40 eggs which she drops prior to hatching. It takes 3-4 months for development from eggs to adults. 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.
A regular 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 massive.
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. Roaches are actually very clean insects, even though they eat garbage. They are called the custodians of nature. They only live in houses where there are crumbs to eat or the garbage can is uncovered. They lay eggs inside the house’s hollow walls. It is commonly said that for every one roach seen, there are at least a hundred more hidden. The roach is also one of the hardiest insects on the planet 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.
- Periplaneta americana, American cockroach
- Eurycotis floridana, Florida woods cockroach
- Blatta orientalis, Oriental cockroach
- Blattella germanica, German cockroach
- Blattella asahinai, Asian cockroach
- Pycnoscelus surinamensis, Surinam cockroach
- Supella longipalpa, Brown-banded cockroach
- Periplaneta australasiae, Australian cockroach
- Periplaneta fuliginosa, Smokybrown cockroach
- Parcoblatta pennsylvanica, Pennsylvania woods cockroach
- Periplaneta brunnea, Brown cockroach
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”.
- The largest known cockroach by wingspan is a Megaloblatta longipennis, with an 18-cm wingspan.
- The largest by weight is a 50-g Macropanesthia rhinoceros.
- The smallest species is Attaphila fungicola, reaching only 4 mm.