This order of insects, scientifically known as Blattaria, consists of around 4,000 species worldwide, of which 30 species are associated with human habitations and about 4 species are well known as pests.
Although worldwide these insects have a bad reputation, many cockroaches live in warm, tropical areas and feed on decaying wood and leaves. They help break down this organic debris; in the process, they add nutrients to the soil through their waste. They’re also a food source for small reptiles and mammals. In other words, cockroaches are ¬an important part of many ecosystems.
In fact, in many parts of the world, just one or two species are responsible for most infestations. Unfortunately, people take much of the blame for this worldwide prevalence. Most cockroach pests have spread across the planet by hitchhiking on boats, airplanes, trucks and even in moving boxes and grocery bags.

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 found within buildings.
Female cockroaches are sometimes seen carrying egg cases on the end of their abdomen; the egg case of most cockroach species holds about 30 to 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 (young) that continue inflating themselves with air, becoming harder and darker within about four hours. Their transient white stage while hatching and later while molting (shedding their outer skin) has led to many claims of glimpses of an albino cockroach. Locally it is believed that the “white roach” is a separate super species that lives only underground and commands other cockroach species to do the jobs for them. An example is getting them food and cleaning them. This is obviously a myth. We also have a tendency to distinguish all cockroach nymphs and smaller species by referring to them as ‘Kokroċ’ while the large ones and adulst with wings as ‘Wirdiena’.

Seven species are known in the Maltese islands. These are the American Cockroch (Periplaneta americana) Wirdiena Ħamra, German Cockroach (Blattella germanica) Kokroċ tal-Faxx, the Oriental Cockroach (Blatta orientalis) Wirdiena tad-Djar, the Brown-banded Cockroach (Supella longipalpa) Kokroċ Isfar, the Egyptian Cockroach (Polyphaga aegyptiaca) Wirdiena Sewda, the Field Cockroach (Loboptera decipiens) Wirdiena tal-Gћelieqi and the Wood Cockroach (Ectobius kraussianus) Wirdiena tal-Buskett.

The latter two are never met in households as one is restricted to one locality and the other is restricted to garigue habitat. The Oriental, Brown-banded and Egyptian roaches are rarely met with as they prefer human disturbed areas but away from them. The latter might be attracted to a very dusty area such an abandoned garage but it is harmless and females are easily consumed by very large woodlice and males are confused with moths. Other species are also locally being discovered.

On the other hand the American and German cockroaches can be very loyal to our houses especially our kitchens and these are the ones that should be treated as pests
The American cockroach generally lives in moist areas, but can survive in dry areas if they have access to water. The members of this species prefer warm temperatures around 28-32 degrees Celcius and do not tolerate very cold temperatures. In residential areas, these cockroaches live in kitchens, basements and sewers, and may move outdoors during warm weather. They have been known to fly during mating season. To aid its resistance the latter is also scavenger that feeds on decaying organic matter and a variety of other foods. It is particularly fond of fermenting foods. Females produce egg cases and carry them protruding from the tip of the abdomen for about two days. Egg cases are then generally placed on a surface in a hidden location. Egg cases are about 0.9 centimeters long, brown, and purse shaped. Immature cockroaches emerge from egg cases in 6 to 8 weeks and require 6 to 12 months to mature. Adult cockroaches can live up to one year, during which females produce an average of 150 young. Despite its name this species originated from Africa and was spread through human agency.

The German cockroach, is a small species, measuring between 1.3 centimeters and 1.6 centimeters long; however, they are known to get bigger. It can be tan through brown to almost black, and has two dark parallel streaks running from the head to the base of the wings. Although it has wings, it is unable to sustain flight.

A female of this species carries an egg capsule containing around 40 eggs. She drops the capsule prior to hatching, though live births do rarely occur. Development from eggs to adults takes 3 to 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 to 400 offspring. Other species of cockroach, however, can produce an extremely high number of eggs in a lifetime, but in some cases the female needs to be impregnated only once to be able to lay eggs for the rest of her life.