The cockroach is probably the most obnoxious insect known to man. About half a dozen species of cockroach have managed to acquire a relationship with man, rivalled only by lice and fleas. Cockroaches may only be known as accidental carriers of pathogens, nevertheless there is considerable evidence to incriminate a number of cockroaches as potential carriers of disease.
The pest status of the cockroach derives mainly from an aesthetic abhorrence of what is regarded as a loathsome intruder: its speed and unpredictable direction of movement, the enormous numbers to which populations can increase and the habit of cockroaches of tainting with a characteristic odour and fouling with excrement all food and surfaces with which they come into contact.
Cockroaches are an ancient group of insects which have existed on earth about 100 times longer than man. At the present time there are about 3500 known species, mostly of tropical origin. As a group, they show considerable diversity of size, colouration and habit. Today, the pest cockroaches have found our man-made environment and food highly suitable for their existence. Wherever food is stored, manufactured, or handled, cockroaches are potentially capable of establishing an infestation.
Cockroaches have the following general appearance; body oval and flattened. Head when at rest is nearly horizontal and bent under the thorax, with the mouth projecting backwards between the bases of the first pair of legs; almost concealed from above by an enlarged pronotum. The whip like antennae inserted just below the middle of the eyes, are composed of very many short segments and are often longer than the body. The mouthparts serve a biting, chewing and licking function; the mandibles are strong and toothed, the palps of the maxillae and labium have 5 and 3 segments respectively. The ocelli are often represented by two thin areas of cuticle. All three pairs of legs of the cockroaches are long and well adapted for running. The gizzard contains an armature for masticating food