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Blatta orientalis (Linnaeus, 1758)

Synonym(s) : 

Common names

  • Blatte orientale, Blatte domestique, Blatte des cuisines, Cafard domestique
  • Oriental cockroach waterbug black beetle
  • Cucaracha negra
  • Orientalische Schabe Küchenschabe

Classification:

  • Order:  Coleoptera
  • Family:  Blattidae
  • Genus:  Blatta
  • Species:  orientalis

Frequency index:

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Overview

In France, the oriental cockroach is one of the least frequent species. It can easily be mistaken for the German cockroach, but it is smaller by one-third so that telling them apart is easy.
Blatta orientalis is particularly fond of dark, damp, cool places (basements, undergrounds, garages, storerooms, sewage pipes), and it is more rarely found in the upper floors of houses and warehouses, although it can reach them by climbing up pipes.

The species is frequent in bathrooms and kitchens, which it often reaches via rubbish chutes in blocks of flats. It moves around rather slowly and it does not like climbing up vertical surfaces, especially if they are smooth, for it is a poor climber.

Like many other species, Blatta orientalis is hardly ever seen in the daytime, but it has an intense nocturnal activity.
Females cannot fly because their wings are atrophied (very short); males have normally developed wings, but they are poor fliers: they can take to the air on very short distances, in the 2- to 3-metre range.
Under our climates,  this species lives for 3 to 6 months.

Recognition criteria

Blatta orientalis mâle

Adult

Size

20 to 30 mm long

Aspect    

Oval, dorso-ventrally flat body. Sturdy, rather long legs, tibiae with rows of spiny bristles.
Fine, moniliform antennae that can be longer than the body.
Very short elytra and stumped wings in females, whereas they cover ¾ of the body in males.
The two short cerci at the end of the abdomen have tactile hairs that are highly sensitive to sounds and vibrations, and enable oriental cockroaches to run away at the slightest noise.

Colour    

Dark brown to nearly black, more or less shiny.
The pronotum is generally darker than the thorax, and the legs are hued with reddish brown.

 

Larva

Size   

8 to 20 mm long

Aspect    

Look like adults, but wingless

Colour   

Light to dark brown

Development cycle

After mating, females lay about 15 successive oothecae that they carry at the end of their abdomen for 1 to 5 days before depositing them in quiet, inconspicuous places, always nearby a food source.

Oothecae are kinds of “baggy membranes” that contain the eggs.
Their size and shape are often characteristic and make it possible to easily tell which species they come from.
B. orientalis oothecae are 7 to 12 mm long and wide, and contain between 12 and 16 eggs.
Larvae hatch 6 to 12 weeks after ootheca formation. They undergo 7 to 10 successive molts before becoming perfect adults.

Full development requires between 8 and 18 months depending on ambient conditions (temperature and relative humidity), and on the nature and the nutrient quality of the feeding stock.

Infected materials

Oriental cockroaches are omnivorous. They feed on all our edible products and on all sorts of food waste.

Among the products they feed on, let us cite: dairy products, meat, sweet or starchy food, pet-food, beer, various types of fat, leather, hair, wool, dirty wound plasters, paper,…
They can also eat the glue used to bind books, thereby causing often severe damage in libraries.

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

Oriental cockroaches originally come from Africa. They are now distributed worldwide, but they are found above all in the hot, damp regions of the globe.