The German cockroach

German cockroach

German cockroach

Season for German cockroach

Season for German cockroach

Latin: Blatella germanica.

This is the most common of the cockroaches that occur in connection with food in Northern European countries. It is approximately 12 mm long and have well-developed elytrons that cover the entire abdomen. The breast is yellowish brown with two dark stripes. Under the elytrons are quite well-developed flying wings. They are not used to fly, but is on rare occasions used as a kind of gliders when the cockroach jumps from tables and shelves onto the floor. Cockroaches are omnivorous, but you rarely find them in food. They are active when it is dark. When it is bright, they sit in cracks and crevices near furnaces, heating pipes, refrigerator motors and other places where they can find temperatures between 25 and 33 ° C, as they prefer.

Cockroaches are social insects. A substance that attracts and unifies them is secreted from glands in the intestine and released later from the excrement. Mating behaviour is also controlled by scent signals. The female secretes fragrances which in low concentration attract males, while higher concentrations of the same odorant triggers the mating game. These pheromones are used in some cockroach traps. Females lay their eggs in brown capsules. These capsules are divided into 30-40 small compartments, each containing an egg. The female carries around the capsule – sticking out of the vulva – until offspring begins to swarm out. Development is progressing through 6 -7 nymphal stages which are relatively wider and darker coloured than the adults. The small nymphs can hide in crevices, which are only 1.6 mm wide (a pregnant female needs 4.5 mm). The development takes about 2 months at 30 ° C, whereas it takes six months at 21 ° C.

German cockroach, female with egg capsule

German cockroach, female with egg capsule

German cockroaches are most comfortable in moist, warm areas with access to water. They climb well and can be found throughout the rooms from floor to ceiling. Dispersal of the cockroach is quite passive. The insects are transported around in goods or empty packaging. The voids in beer cases for example are good hiding places for cockroaches. Cockroaches can damage food by chewing them, by contaminating them with their droppings and by the unpleasant odour that cockroaches have. In addition, it is generally poor advertising that cockroaches come with a company’s goods.

(3) The German cockroach and the forest cockroach

Dusky cockroach

Dusky cockroach

The German Cockroach

The German Cockroach

The German cockroach is hardly more common in Germany than anywhere else in the world. It lives in the wild in tropical forests. As a synanthrope species in colder regions it favours especially indoor environments that are both warm and humid. Outside the tropical forests the German cockroach lives in bakeries, greenhouses, hospitals etc. It spreads between houses by heat ducts.

The forest cockroach tolerates lower temperatures than the German cockroach. It lives in forests around the world, including Northern Europe, and appears only occasionally inside. In Northern Sweden it is synanthrope.

German cockroach

( Latin: Blattella germanica)

This is by far the most common species of cockroach in Europe.

For most people the idea of having cockroaches on the kitchen table is in- tensely unpleasant, but for those with an eye for such things these are elegant insects.

Both sexes have very well-developed wings, which cover the whole of the abdomen, but these are used not for active flying, but for gliding when they jump, for instance, from the table to the floor.

The female lays her eggs in a special brown capsule which is divided into 30-40 small compartments, each containing a single egg. In the German cockroach the female carries this egg capsule protruding from her genital aperture until the small, wingless young are ready to hatch out. At room temperature the full development to the adult stage takes about 6 months.

Cockroaches are practically speaking omnivorous. They are active at night, spending the hours of light hidden in crevices, particularly near warm places, such as ovens or radiators.

They are very gregarious, and a substance produced in the alimentary canal and passed out with the faeces may serve to attract and keep them together. During the mating period cockroaches are also motivated by scent. The females produce a scent which the males perceive by way of special sense organs on their antennae.

In many parts of northern Europe cockroaches occur in bakeries and restaurants, and also in hospitals, canteens, food factories and many private kitchens. Normally cockroaches cause no real damage. It has been suggested that they transmit disease but this has not been directly proved (see also p. 55). On the other hand, there is a need to be watchful, for several species of pathogenic bacteria have been isolated from cockroaches caught at random. These insects may also destroy foods, partly by gnawing them, but mainly by fouling, and by tainting them with their unpleasant smell. Cockroaches also cause damage by gnawing paper, leather and textiles.