Oriental cockroach (Blatta orientalis)

Oriental cockroach

The oriental cockroach is sometimes call the black beetle or waterbug (US).

Despite being called the oriental cockroach, it is not native to the ‘Orient’. It is thought to have originated in Africa or southern Russia.

Found worldwide in tropical and temperate regions (quite tolerant of cooler climates).

Prefers cool, moist, dark habitats, from which it gets its “waterbug” name.  They are found in leaf litter and around garbage bins outside and in buildings are found in basements and sib-floors, sewers, drains and other damp areas. They quite often use plumbing pipework to move into and within buildings. They tend to move indoors during the cooler seasons.

Oriental cockroaches live in aggregations – cockroaches of all ages (young nymphs to adults). Whereas the cockroaches don’t activity co-operate as a community, the young cockroach nymphs, which tend not to leave the harbourage, benefit from this arrangement as they feed on the droppings and vomit of older cockroaches.


Colour: Dark brown / black.

Size: Up to 27 mm

Males: Non-functional wings, ¾ the length of the body

Females: Only wing buds


Colour: Tend to be lighter than the adults – more reddish brown / brown

Size: From 4-25 mm


Eggs: 16 eggs per ootheca (egg case). Ootheca deposited in a warm, sheltered position, near a food source well before egg hatch.

Number of nymphal stages/moults to adult: 7

Length of life-cycle (Egg to adult): 365 days

Life span of adult: Up to 6 months

Like other cockroaches, the oriental cockroach will eat almost anything but it eats where it lives and is often found feeding on garbage, sewage, or decaying organic matter.

  • The adults cannot fly
  • They are not great climbers so are generally found at ground level
  • Oriental cockroaches are more slow moving than the other large cockroach species
  • They tend to move indoors and hide during cooler weather and are more active and visible in summer

Cockroaches are viewed as “dirty” insects, mainly due to their association with sewers and human waste. Indeed, they have been shown to carry a wide range of different diseases, in particular gastro bacteria such as Salmonella and E. coli, as well as a number of parasitic worms. When they move across food preparation surfaces and feed on any exposed food, there is always the potential to transfer these diseases to humans. This is particularly the case for oriental cockroaches which tend to live in sewers, drains and garbage bins.

Good hygiene is key to preventing a cockroach infestation:

  • Fix any leaks and areas of moisture
  • Consider draining and improved ventilation for moisture issues
  • Fill any cracks and crevices, that would allow cockroaches easy access from the outside
  • Ensure rubbish is put into sealed containers
  • Keep food preparation areas clean – clean up food spills and clear away dishes after meals
  • Don’t leave unfinished pet food out overnight

Treatment notes:

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