The cockroach is probably one of the best known and most hated of insects. It is associated by most people as an indicator of filth and unhygienic conditions. The cockroach descends from an ancient lineage of insects which have inhabited our planted for around 100 times longer than humans. Some 4000 species are recognised today, of these only about twelve are commonly associated with humans. Due to their close contact with humans several common names have been given to these insects. The actual name cockroach is reportedly of Spanish origin, derived from the word "Cucaracha". In the UK the Oriental Cockroach Blatta orientalis is reffered to as the "black beetle" due to its dark colouration. It is also called the "mill beetle" and the "black clock", probably due to its appearance at dusk in mills. In certain regions of Europe the cockroach has been given local names which infer that the insect originates from a neighboring country, impling the neighbors are not as hygienic as themsevles. Examples for this are; "Russe" used in what was East Germany meaning "Russian Cockroach", in West Germany Franose is used, meaning "French Cockroach". Many other colloquial names have arisen, in the USA around Philadelphia the Oriental Cockroach is called the "Shad Roach" due to its presence in high numbers at the time when Shad fish spawn in the river Delaware. "Water bug", "Yankee settler", "Shiner" "Croton bug" "Steam-bug" and "Stream-fly" are all local names for the German Cockroach in various regions of the world.

The cockroach is a dorso-ventrally flattened insect, meaning it looks flatter when view from the side compared to its shape when viewed from above. The head is orientated in a downward facing position and from above is largely covered by the pronotum. Well developed compound eyes and very long filiform antennae are found on the head. The two pairs of wings are differentiated with the tegmina (forewings) being leathery and serving to protect the fan-shaped hindwings, which are the primary flight wings. The wings show mainly longtitudinal veination.

Click here for an image of a cockroach showing its morphology

Adult cockroaches can live for considerably periods of time up to two years if conditions are favourable. Being exopterygote insects they have an egg and several nymphal stages with the young nymphs showing similar morphology to the adults. There can be between 5 and 12 nymphal stages depending on species, and in the case of Blatta orientalis also depending on the sex. In this species the female take both longer to develop and passes through more nymphal stages than does the male. Eggs are contained within a specially secreted case, the ootheca and will hold between 12 and 50 eggs at any one time. The ootheca are extremely resistant to desiccation, and to some insecticides for certain species. The size and shape of the ootheca can often be used to determine the presence of a particular species.

The first nymphs are very small and white when they exit their egg. They quickly darken within a few hours showing a similar uniform brown colour common to the whole group. They take several months before reaching the adult stage. Cockroaches are able to fly but seem to do so rarely. Both temperature and diet effect flight and flight is uncommon in temperate climates as the flight muscles seldom reach a temperature where they can be activated. Cockroaches are gregarious insects and can quickly reproduce to form huge populations within a domestic environment. Although essentially tropical in origin they are able to survive the temperate climates of both the northern and southern hemispheres by sheltering within warm human habitations. Even though cockroaches seldom fly they are extremely fast runners and will run along surfaces usually where two meet, such as along skirting boards, or along cupboard backs which are not completely flush with the wall. They are nocturnal insects and spend most of their day resting in small cracks and crevices around dwellings.

Blattella germanica

Blatta orientalis

Periplaneta americana

Periplaneta australasiae

Periplaneta brunnea

Periplaneta fuliginosa

Supella supellectilium