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Blattella germanica (Linnaeus, 1767)

Synonym(s) : 

Common names

  • Blatte germanique
  • German cockroach
  • Cucaracha Rubia
  • Deutsche Schabe

Classification:

  • Order:  Dictyoptera
  • Family:  Blattelidae
  • Genus:  Blattella
  • Species:  germanica

Frequency index:

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Overview

German cockroaches originally come from Western Africa. It first appeared on Earth more than 400 million years ago.
In Europe, it is rarely found outside cities and inhabited places for it cannot survive under cold temperatures. It is an omnivorous, necrophagous, gregarious insect that is particularly fond of hot (25-32°C), damp (70% humidity) places, where foodstuffs are stored. It favours quiet, dark corners, and can be found about anywhere, in waste, under tapestries, in various pipes, in rubbish chutes, in cavities, electrical cupboards and cables included, and even in odd places such as electrical gear engines…
They are by far the most common cockroaches in households (90% of recorded cases) and they thrive in food warehouses, bakeries, restaurants and hospitals, especially in urban areas. The reason is that they find ideal development conditions (plenty of food, many shelters) in those places where temperature and humidity vary little. They are perfectly adapted to present urban housing, and their daily activity is divided into gathering and resting (gregarious phase) in the daytime, followed by rather individual scattering at night to find food. So they have a mostly nocturnal activity. Adults and larvae can easily move on vertical surfaces, but not on ceilings. Populations are usually composed of 80% larvae and 20% adults on an average.
 

 

Recognition criteria

Adult

Size

Up to 20 mm long.

Aspect    

Elongate and dorso-ventrally flat, with a soft body; head, thorax, abdomen clearly visible. Long, fine antennae. Well-developed eyes (more than 2,000 facets each) that allow nearly 360° vision.
Among the other cockroach species found in France, German cockroaches are easily recognisable thanks to the 2 black longitudinal stripes on their pronotum
Big wings, longer than the abdomen, yet they do not allow adults to fly long distances. Wings are longer in females, which makes it possible to differentiate them from males, which are also more slender.
There are 2 characteristic cerci at the end of the abdomen. Their tactile hairs are highly sensitive. They can sense sounds and the least vibrations, enabling cockroaches to run away rapidly.
Like other cockroaches, German cockroaches cannot see infra-red light but react quite well to ultra-violet light.  

Colour 

Dark yellow to dark brown, entirely light-coloured legs.

 

Larva

Taille  

7 to 17 mm long.

Aspect    

Look very much like adults, but wingless.

Coloration    

Uniformly light brown.

Development cycle

Shortly after mating, females secrete an ootheca that contains the eggs. It is laid in a rather damp place, nearby a food source. Cockroaches’ oothecae are characteristic of each species and thus allow their identification. German cockroaches’ oothecae have a strong, thick wall, they are 6 mm long and can contain an average 30 eggs. Eggs hatch 2.5 to 4 weeks later.
When hatching time is close, females hide their ootheca away in any kind of crack located not far from a food source. Then they cover it with food or excrements to protect it. A female can produce 4 to 8 oothecae throughout its life-time, each laid at about 1-month intervals. After about 15 weeks (at 25°C) and 5 to 7 molts, adults are formed.
Male adults can live up to 8 months and females up to 6 months in average temperature conditions around 25°C.
Temperature can considerably influence the species’ development length: the full development cycle can take up to 2 years in unfavourable conditions.
One pair of German cockroaches can theoretically give birth to several hundred thousands offspring, whereby the exponential proliferation of that species which represents a true scourge in certain conditions.

Infected materials

The food diet of German cockroaches is quite diversified, since it is composed of all the ingredients that constitute human and animal food : dairy products, meat, sweet or starchy food, paper, pet-food, beer, various types of fat, together with any kind of food waste.
They can even eat one another in case of serious food shortage, and can live through several-week-long fasting periods. However, they have to drink a lot of water to keep alive.
Cockroaches deteriorate, contaminate and soil food via their excrements. Moreover, they leave foul-smelling secretions where they have been.
They can also be the vectors of certain pathogenic germs (bacteria, fungi, protozoa, helminths).

Geographical distribution

German cockroaches are found worldwide and have a more or less widespread distribution in all hot regions of the 5 continents. They represent alone 90% of the pest cockroach population that can be found in urban dwellings.